Replacing stem on non-oversize bars I have a road bike from Circa 2003 and it currently boasts an ITM Millenium stem. The stem is a bit long for my liking at around 130mm and I was thinking of replacing it with a shorter one for a slightly more upright riding position.

I have a feeling my bars however are of clamping diameter 25.4 mm, although they may be 26mm as it is an Italian bike (ITM bars too). Shopping around I notice that pretty much all new stems are of the oversize 31.8 mm clamping diameter so I assume they won't fit my bars.

How would I get around this problem? I heard one could get shims to thicken the bars at the clamping point but sourcing them seems to be tricky.

25.4 ( or one inch ) is almost always an MTB handlebar diameter or a very old cheap bike. From 2003 and of good quality, it is almost certainly a 26mm handlebar.

There are parts of the bike you can bodge without much concern and parts you can't. Anything in the fork/headset/handlebar area is not something you should try and "make work". If it goes wrong, you'll crash hard.

You should still be able to find 26mm stems if you look hard enough. Here is a good source.

http://store.velo-orange.com/index.php/components/stems/threadless-stems.html

They also sell the appropriate shims to use your bar with a 31.8 stem, but if it were my bike, I'd just pony up for a new 31.8 handlebar.


Rebuild Gary Fisher Mullet rear derailleur I have a Gary Fisher Mullet from sometime between 2006 - 2008. I don't know anything about bike except the fact that I got one Hehe.

My rear derailleur is in pretty bad shape. Well, I don't know for the derailleur itself but the gears are smashed.

I barely use the bike and I don't bike that much at all. But it's summer and I wan't to at least do some runs with it because it is almost brand new.

The derailleur is a Shimano, not sure about the model, but it's the one that came with the bike, so that might help.

I'm trying to keep the cost as low as possible, so I was wondering if I can buy the gears without changing everything, and then go to a bike shop and have someone ajust it ? Or do I need to buy a complete system for it ?

Thank you for your inputs, Greetings.

For explanation of bicycle parts see: Terminology index - a list of bike part names and cycling concepts

The problem you describe may be caused something other than worn sprockets. It may be 'ghost shifting' where the chain hopes back and forth between two cassette sprockets. This may be caused be misalignment or bad adjustment of the derailleur or gear shifters.

I would take your bike to a good local bike shop, have them diagnose the problem and find out what components - if any - are worn out. You may find that you simply need a good tune-up.

Good news is you can replace the cassette and chain, derailleur etc. individually without having to replace the whole drivetrain (unless the whole drivetrain is worn out of course!)


What kind of Rear derailleur do i have and what RD should I buy as a replacement? I have an old mountain bike (21 speed) and I'm not sure what kind of rear derailleur i have. So far the performance is still okay but I was planning to replace it with my spare RD (SunRun Index) but according to the mechanic it's not compatible. Is there a way that I could still use my spare RD on my bike? if not then, what rear derailleur should i look for? (preferably shimano)
Still a newbie when it comes to bike parts

I think you will need a claw hanger adapter.  The old derailleur has one that appears to be non-removable, and the new one has a 10mm bolt that expects to find a matching hole in the frame, which yours won't have.
You probably want something that looks like this:

There is a sunrace branded one, but it looks the same in the critical dimensions as a generic pictured above.


Is there any reason to keep original drive-train components together until they can all be replaced? I broke the master link in my chain a while ago and my LSB told me it was because I wasn't cleaning/lubricating my chain often enough. The chain had experienced more wear than it should have as a result. I asked about replacing the chain and was told that you typically don't want to replace individual parts of the drive-train, that mixing and matching new chain and old chain-rings is a bad idea. Is there any truth to this? Why would a new chain on an old (we're talking less than 4 months) be a bad thing?

Breaking a master link, as already said, is not so common, and is usually not related to the chain wear. It can be related to loss of lubrication, for example when the chain RUSTS and gets some hard links that cause the chain to get entangled with the derailer while pedaling, for example. But only because it is worn, supposing it is clean and lubed, I'd say no.
Installing a new chain with an used cassette might be divided in two kinds of situations:

You install and the chain doesn't skip. This is the ideal situation, meaning you replaced the chain at the right time, and your cassette will last much longer (note: this is the recommended thing to do - use lots of chains with the same cassette, replacing them often as soon as they get some wearing);
You install the chain AND IT SKIPS over the cogs when you pedal. That means you waited too much to replace the chain. It might be very difficult or almost impossible to use the new chain and make the cassete wear "back to normal". In this case, it MIGH BE a better idea to keep riding with that chain for a bit more and replace it together with the cassette later (waiting too much can be dangerous, since the chainrings might get damaged in the process). Even when the chain skips, though, if it skips only while pedaling hard, and/or only on specific gears, it is usually possible to ride slowly in the beginning, and the skipping starts to disappear as the cogs wear, and everything might come back to normal.

So, the shop guy may or may not have told you the truth, depending on how much your cassette is worn. This is not an easy thing to do if he didn't measure the chain with a gauge, so it is possible that is obvously worn, or he has a very good eye, or he actually wants to sell you the whole kit. Besides, the need to change everything together is surely NOT true, since the expected is to change the chain often, so as to preserve the gears, which can last MUCH longer.

I would do the following: buy a new chain and try. If it works, it works. If it skips, I put back the old chain and keep the new one at home. When the time arrives, I change the cassette and then install the new chain.

(Finally, some crafty people are able to remanufacture the shape of the cassette teeth by disassembling the cassette and correcting the teeth shape with a round file, one by one. I did it successfully a lot of times, but it takes some skill and a lot of time and hand labor, sort of a masochistic hobby, but anyway it works and can save you some money or at least the trip to the shop.)


Can I jump from small heights on my bicycle? I have recently bought a Merida Matts 40-D bicycle. I didn't buy it for extreme sports, rather for a recreational cycling, etc, but as I'm only 22 years old, it's too tempting to jump down from small stairs when riding through the city. Let's say the height to jump is less than 1 meter and my weight is 74 kg (162 lbs). Can I use this bicycle for such, once in a while, or should I not? I don't want to break it, nor destroy the wheels, etc.

EDIT: To further clarify what I mean, I made this simple scheme:

So basically, I never hit the stairs, just the ground when landing.

Your bike is designed for riding on rough terrain, like forest trails, roots, take an occasional drop. It should not break after a few drops from low heights, if you apply the technique correctly. Of course, it will shorten its life, so if it becomes regular practice, you should switch your bike from entry level MTB to something more appropriate.

You might find stickers on your bike that it is not designed for racing, but just recreation usage. This may put limitations on warranty.


Quick link won't 'click' I'm brand new to bicycle maintenance/repair and just replaced my chain for the first time which I'm very excited about. I do, however, have a problem. I used a quick link to attach the chain and I haven't been able to get it to 'pop' into place. I've pedaled it a bit while it's upside down and everything seems fine, I'm just not sure if it is. I don't want the chain to let go on me all of a sudden (I can easily undo the link by hand right now, seems too easy).

Does that seem right?

The master link on the picture looks properly closed. Master links for 8- and 9-speed chains often do not require tools to open them, while 10/11/12/13-speed chains are better approached with special pliers.
Be, of course, sure that you use a master link that matches your chain and is not too wide, e.g. an 8-speed one for 8-speed chain, 9-speed for 9-speed etc.


Which upgrades are required for participate in cycle race? I want to take part in cycle race, so for that I upgrade my bicycle to 18 gear. (It was not shipped with gears)
Here is my cycle STREET RACER NE 26T. (this is the same model I've, but size may be different)

Is it good idea to use upgraded cycle in race or I should buy new one on which gears are pre installed?

Here is my event detail
Vishal Khadi BRM - 200 and here 200 BRM on 16-Jul-2017

Also is this type of bicycle is ok for this type of race event or I need other one?

Here are some personal detail
I am riding around 20km (in 1 hour) in working days.
40-45 km in weekends and it take aprox 1 to 1.5 hour.
Max speed I rode was 42km / hour (in trafic)

This is first time I am taking part in cycle race event, so how should I start practice for this event?

You can ride any bike in a race, provided it's in good enough working order to get you over the line.

Regarding gears, it looks like the cost to add derailleur style gears may be prohibitive, as I assume this bike's rear wheel is single-speed specific and the dropouts aren't vertical (which isn't the end of the world but not ideal). I'd probably either look at a geared road bike, or rebuild your rear wheel around an Alfine/Nexus internally geared hub.

If this is your first race I'd probably just ride what you have to see if you like riding competitively before spending money on upgrades or on a new bike.

edit: This 'race' appears to be a 200km audax - I'd be incredibly reluctant to do that kind of distance as your first race. Have you ridden over 150km in one hit? If you're super fit, or not bothered about your time you could do it on your existing bike, but a specific road/audax bike would do it quicker and more comfortably. Maybe build up slowly to that kind of distance - that's a very long day in the saddle.


Is my new-to-me used suspension fork a MY2000 Manitou Mars Elite Hyperlite? I just got a new-to-me used fork from circa 2000. It's supposed to be a 26" 1 1/8th threadless Manitou Mars Elite fork with 80mm travel.  I'd like to source spare parts and repair/service instructions -- do I have it correctly identified as a MY2000 Manitou Mars Elite Hyperlite? I've uploaded photos, in particular one with a date code stamp on the "bridge" that shows "00" surrounded by 12 wedges, 11 of which have raised dots. This suggests to me a manufacturing date of 11/2000, which may or may not be MY2000.  Serial number is 300169715, but I've been unable to find a decoder that gives date of manufacture or model year from that, and Hayes(Manitou) hasn't yet returned my call.
Q: Is this a MY2000 Manitou Mars Elite 26" 1 1/8 threadless 80mm fork? MY2001? Some other variety of Mars fork?

Hayes tech support recently returned my call on this, and although they don't have access to serial number records that far back, they did confirm that the 11-00 manufacturing date stamped in the arch almost certainly means it's MY 2001. They also sent me the tech manual -- I was impressed with Hayes' helpfulness!


Align Alfine 11 when the bolt does not go far enough? I recently got a new bike (Cube Travel SLT, with belt and Alfine 11).

The hub is not aligned. Looking at the manual, for instance at http://www.koga-signature.com/docs/Maintenance-Manual.pdf (bottom left of page before last) it says to shift down from 11 to 6, then align the yellow dots with the cable adjustment bolt.

Well, the bolt does not go far enough. I can align very precisely when in gear 7, but that's not the point. When I ride, I feel the hub skipping around gear 6-7 and I guess that's the reason.

How can I align the hub when the bolt does not go far enough?

The 'bolt' that the user manual refers to us usually known as a 'barrel adjuster'. Their function is to effectively shorten or lengthen gear or brake cables relative to their housings. In your case this is used to fine tune the cable length to achieve proper gear selection in the hub.

Your problem is that the cable is either too long or short even when the barrel adjuster is at the extremes of adjustment. What's probably happened is that the cable has stretched or the housing has moved a little bit (common in new bikes). The user manual seems to show there is a little clamp on the cable that locks into the hub, the position of that clamp probably needs to be adjusted to bring the gear alignment back into the adjustment range of the barrel adjuster.

If you're not familiar with bike mechanics I'd take it to a bike shop for the adjustment. If the bike is new you should be able to take it back to the shop you bought it from for free adjustments (at least that's common practice I the US, I would assume the same is true in the Netherlands).


Gear to protect against hand injury in a crash I commute to work a few miles on my bike in the city.  Today someone walked out in front of me and I squeezed the brakes too hard and went over the handlebars.  I suffered a mild elbow fracture because I put my arms out in front of me and the palms of my hands are destroyed.

I started thinking, I have had several incidents while commuting (mostly in snow or on leaves) and I almost always get hand injuries as a result.  I'd like to get gloves that protect my hands.

But:

I don't want the gloves to make injury to elbows, arms, head, scaphoid, or anything else greater.  That is, they shouldn't stick to the asphalt too hard nor slide too much (I think...I'm open to suggestion)
They should be comfy to ride.  I can have a separate pair for winter and summer riding.
I'd prefer if they were tough enough to withstand a few falls without taking too much damage.
I'm always on roads and bike paths, so asphalt is the only landing consideration.

I'm not sure what kind of stuff to get.  Cycling gloves seem like they are mostly leather and it seems like they would be damaged from a fall like I just had.  Motorcycle gloves seem heavier duty and have more protection, but I don't know how they would have affected this situation.  That is, I'm very glad my hands are hurt and face/head/shoulders are fine.

Is damage to wrists or scaphoid bone a serious concern?  If so, are there good gloves for that?  I'd love some suggestions.

Edit: BTW My commute is only like 20 minutes each way per day.  Long distance issues are not of concern for me.

Thankfully I never ride without gloves. The light weight gloves with padded leather in the  palms is all you need - they are cheap, comfortable and effective - what more could you ask for. I had a crash after my bike was tampered with and the front wheel fell off. I am a programmer, and although I emptied the company first aid kit of dressings, and could not walk properly or bend my elbow for days, I could still type. Had I not been wearing gloves, I would have been off work for weeks.

As I see it, if you damage the leather enough to make the gloves unserviceable, and walk away - keep walking - straight to you lottery shop. Leather is tough and slide - in my case the gloves, which took the full impact of my fall, had no visible damage - unlike my shoulder, elbow and hip....

Wearing big heavy gloves might protect you hands, but downhill riders and motorcyclists that wear these also wear full face helmets and body armour - unless you do the same you will come off and although your hands will be fine, the rest of you won't be.

Any bone damage is a problem - if you don't want it, don't fall off. You can learn to fall to minimize injury - downhiller riders are the masters of this, question is - can you be bothered as the only real way to learn is to do it.... You could wear body armour but its no guarantee.....

Edit:
Since writing this many years ago, I have taken up Martial Arts with my children (I am over 50). The techniques taught have helped enormously in a couple Mountain biking falls I have had, including one where I went 'over the bars'.


Cyclopark Sportive Kent I love riding my bike and am looking at my first challenge! I've seen a sportive in October from Cyclopark, I've not been there and not sure of the roads the route is on, looks hilly!! Has anyone seen info or know the roads?  All help gratefully accepted for a newbie!!

The CycloPsycho 2016 ("A major test of skill and nerve") takes place on Sunday, 30th October 2016.

  Where is it?

  Starting and finishing at Cyclopark in Kent, this killer sportive takes in some of the most feared and steepest climbs Kent has to offer. All routes start with a lap of the circuit and head straight out into the surrounding country side.  Avoiding busy main roads is a real bonus compared to many sportive routes.

  Why ride it?

  Not one for the faint-hearted, with 13 categorised climbs and over 7,500 feet of climbing, on the long route, this ride is sure to test the legs of any rider.

  The Long Route> 88 miles  Start 8:30am

  The Medium Route> 67 miles Start 9:00am

  The Short Route> 28 miles  Start 9:30am


Out front attatchment for mobile phones/GPS I'm looking for a case to mount my android as a GPS device.  I find that a lot of cases require attaching off centre (thus taking unecessary handlebar space), or have very bulky clips that don't fit around the stem, (and anyway, I like to have my cyclecomputer on the stem) or on the top bar, which often obstruct my legs or gets knocked.

Has anyone seen a mobile phone case which attaches like the Garmin out front system? (http://www.amazon.co.uk/Garmin-Out-front-Bike-Mount-Edge/dp/B0096855IO) which looks like it'd do a good job of keeping the GPS at the right position for reading, without obstructing the operation of the bike.

Edit: Nexus 4, weather proofing needed! (thanks)

Thanks

DriKase and Drikase XL (for large phones or phones with cases) are good waterproof phone cases which mount to your stem and keep your phone dry while being able to operate it through the liner. It doesn't set it out front of your bars though.

http://shop.alt-gear.com/c/bikase


How to choose the light bulbs for a given dynamo I have a 16V 8W bottle dynamo and two light bulbs:

one is marked 6V 0.05A and is working properly
other does not have any inscription and ceased to work.

I would like to replace the second light bulb. What should I search for?

Apparently the 1970s PX-60 (see the OP's comment  had a Soubitez bottle dynamo ("génératrice") on the rear wheel as sold. Similar looking vintage Soubitez dynamos come up on eBay, where sellers and photos both indicate that they're 6V 3W.

However dynamos labelled 16V 8W really did exist: They were made by Sankyo, and again appear on eBay.  They were apparently fitted to Raleighs and Schwinns in the 70s.  If that's really what the OP has, and the output is really that much higher rather than just being an optimistic rating, I could be tempted to try something like a 12V 5-6W incandescent bulb in the front, and 12V 1W at the back, if you can somehow make them fit.  These are cheap as they're used in cars, so getting a couple for testing would be reasonable, as would getting through them quicker than you'd really like.


Cable head is too small when I came to change the shifting (gear) cable on my claude butler bike I found that the original cable has a slightly bigger head(nipple) than the replacement cables I have-3.9mm compared to 3.5mm and consequently will not work-wtf
The mech is shimano v brake

Sounds to me like you've got Campagnolo-sized shifter ends.  The difference is subtle but definite.
Left is Shimano, Right is Campagnolo.
Not sure how you're measuring, using a ruler might explain the difference. The common-quoted diameters are
Shimano shifter end barrel diameter: 0.173" (4.39 mm)
Campag shifter end barrel diameter:  0.159" (4.04 mm)

Generally speaking, campagnolo stuff is more expensive because it is less common, because it is more expensive (loop!)  These shouldn't cost more than a couple of dollars each.


Padded saddle VS padded shorts Why do cyclists use padded shorts instead of padded saddle? It seems like putting padding on the saddle would be more optimal. Doubly so for triathlon.

Padded seats tend to have more padding than used at any given time. This pushes the other 'extra' padding into the soft tissues. This causes numbness and discomfort over time.

So slim hard seats are actually more comfortable over time, if they are the right size. You need to make sure your sit bones (ischial tuberosity) are well situated. The sit bones of your hips are designed to support weight for long periods of time, where a plush seat disperses your weight to muscles and other areas.


Which option; cx bike or mtb and road bike? I've done my research and i've narrowed it down to 2 options for me

Option 1: buy a low-end cyclocross bike for $1200
or
Option 2: buy a low-end road bike for $800 and a low-end mountain bike for $400

My budget is $1200
I want a bike that will allow to me ride on the road and on the rough trails.
Please don't suggest a touring or hybrid bike because i don't want the relaxed geometry. I want to go fast.
I'll be using these bikes for fitness and fun, not for commuting.
So which option would be better for me?
Would a low-end road bike be better on the road than the low-end cyclocross?
And would a low-end mountain bike be better on the trails than the low-end cyclocross bike?

Thank you for your input

I want a bike that will allow to me ride on the road and on the rough trails

I guess we can't be sure what you mean by "rough trails", but if you're talking about what I call "rough trails", a CX bike just isn't going to do it.

  i don't want the relaxed geometry. I want to go fast.

Relaxed geometry and high speed often go together off-road (think DH bikes).

On the road, a $1200 CX is not going to be as good as a $800 roadie, but that's only because of the knobby tires.

I think your best option is the road-mountain combo.

If you wanted one bike to do both jobs, I think a mountain bike with ~1.75" semi-slicks would be better than a CX. Plus, that won't cost you $1200.

A side note: No matter what you end up getting, you should buy used. You'll get much more bike for your money.


Chain slips off chainrings with a lot of pedal force I have a 2001 Raleigh R600 road bike. It wasn’t ridden much when I got it, and I’ve recently been putting some miles on it. It was a 3x9 speed with 9 speed components. I just changed:

Wheels
Cassette: to a 10 speed with 34t largest (was 28t)
Rear derailleur to a short cage 10 speed
10 speed chain

When I put a lot of force on the pedals (standing up or high gear and push hard), the chain comes off the chainring and makes a grinding/cranking sound.
LBS said components are not compatible, but my shifting is 95% optimal on the rear derailleur. I even can get into the largest cog. If I’m not pedaling with a ton of force, it rides very smoothly and shifts fine. Chain length should be good based on my calculations.
I didn’t change the chainrings, and they could be worn. Is it that or that my components aren’t compatible and it’s misaligned somehow?

I've done something similar - mixing a shimano 105 9 speed triple chainset with a 10 speed chain and a 10 speed cassette and 10 speed derailleur.  It all worked adequately.  It ran fine after a lot of tweaking.
However my chainrings were worn and I had similar slips while climbing.  So I scored some new-old-stock chainrings for the big and middle rings, and all my slipping problems went away.
They happened to be biopace, but that's not relevant.


Crank arms are not parallel to each other. What could have caused this? It is a cottered crank. Crank arms themselves don't seem to be bent. It is a non-cartridge style spindle. Any ideas as to why they are not lining up?

Like you said, they are cottered, what makes them aligned is that pin through a hole, which at the same time tightens the crank arm around the axle.

If you google "cottered crank", you can see the spindle, which has a slot in each side.

My hypothesis would be: or the cottering bold got deformed, or the spindle slot itself got deformed, or both.

A bolder hypothesis would be twisting of the spindle due to deformation or cracking, but most probably the bearings would not spin freely (how are the cranks spinning, by the way?)

The side which appears on your photo looks OK from outside, the other side we cannot tell.

But for sure this is a VERY irregular situation, which demand a full disassembly of the system, and absolutely no use before that.


pedal falling off axis One of the pedal arms in my bike is loosening off the crank every so often. When it starts to happen, the pedal arm, that has square ends, and the nut will end up detaching from the crank, so I have to tighten it back up with a socket wrench like the one in the picture below as tight as I can, but after a few weeks it will start to loosen again. Everything else seems to be ok otherwise.

What can I do to fix this problem permanently?

Is it the pedal or the crank arm?  I'm presuming the crank arm, since you wouldn't tighten a pedal with a socket wrench.

If the crank arm is coming lose regularly then most likely the "socket" in the arm, where it attaches to the crank axle, has become deformed from riding it loose.

But it's possible that you've just not been tightening the crank bolt tight enough -- it needs to be VERY TIGHT.  (The Park Tools website has torque specifications for many brands, if you want to look there.)

You can lessen the chance of the bolt loosening by using a removable thread lock compound on the bolt.  Also, if the crank axle has square (vs splined) ends and the crank arm socket has become badly deformed, a clever person can make shims from a pop/beer can to eliminate the "play" -- not a permanent fix, but enough to squeeze a few more months of use from the setup before you must replace the crank arm (and possible the crank axle).


Sealed bearings characteristics for road bike wheels? I have fulcrum racing quattro road bike wheels. I'm changing my bearings quite often since I noticed that in general they last around 5000 km (over winter). I'm usualy using SKF 61903 bearings from local dealer, i even used NTN bearings they both lasted around the same.

I noticed that bearing of the drive side of the rear wheel gets worn out much quicker than on a non drive side. I'm wondering is this due to higher forces from chain or there is a humidity and rust problems.

What parameters of the bearings should I consider when buying new bicycle bearings? Don't just say buy ceramic bearings. I'm sure that helps them not to get rusted that much since only bearing race can get rusty but still..:D

I noticed there is multiple choices when it comes to bearings. I know there are ceramic bearings, ABEC 1-X and also double lipped bearings,.... anyone with some more experiences?

What parameters are you looking for when buying new bearings for bicycle wheels?

This answer will be updated if and when I find more information. Please note that I'm not a bearing expert. If anyone has supplemental information, I'd welcome hearing about it in comments or in another answer!

Dimensions

The bearing dimensions are the first obvious parameter you should pay attention to, just to make sure you buy the correct ones for your wheel. The first video that @Greg posted discusses bearing sizes, which are denoted by the numbers in the bearing model. An interesting point: 69103 bearings are apparently equivalent to 6903 bearings, i.e. the bearing outer diameter (30mm), inner diameter (17mm), and depth (7mm) are identical. In fact, someone with Fulcrum wheels asked this on a forum and was told that they are identical. This may aid you in finding bearings from different manufacturers, although my impression is that SKF is generally a good manufacturer.

Sealing

In summary, most cartridge bearings have seals on one or both sides. For winter riding, you want to make sure your bearings seals are good, preferably full contact. Determining what is a good full contact seal may be difficult, however. To some extent, you can trade sealing for friction, and this tradeoff clearly matters if you are building a bike specifically to challenge the hour record. For practical use, the watts saved aren't worth the risk of damage due to contamination or the additional drag. Even for a pro racer, poor sealing will lead to additional contamination, which could cause greater drag.

All bearings have seals to keep contaminants out of the bearing, and the grease inside it. Generally, going from least sealing to best, there are non-contact bearing shields, low-friction and non-contact rubber seals, and full-contact rubber seals. Bearing shields do not touch the races of the bearing (i.e. parts that touch the bearing bore and the axle), and they offer the least friction. The full-contact seals offer the greatest friction. That said, the friction gained versus a low-friction seal could be something on the order of magnitude of 1-3W per hub. This is a very small difference. I am basing this off a podcast by Friction Facts (podcast #8, I believe), and I will cite this when I can retrieve the source. Phil Wood's site explains that they have two bearing types: standard bearings with full contact seals, and another bearing for races and fair weather than has a partial contact seal. A page by SKF briefly describes the types of sealing available for bike bearings.

You can sometimes deduce the type of bearing seal using the letters after the bearing's size code. However, the codes may be unique to each bearing manufacturer. Adam Kerin of Zero Friction Cycling says that the suffix -ZZ almost always denotes a non-contact shield (see the paragraph at the very end of the linked PDF), but you don't want this type of bearing anyway as it doesn't offer sufficient protection. Post 16, by Josh Poertner of Silca, on this Slowtwitch.com thread appears to corroborate this also.

Bearings can also be sealed on one or both sides. A 6903-1RS bearing would have a rubber seal on one side. I believe the other side is open to the elements. In contrast, 6903-2RS bearings have rubber seals on both sides. I think that 1-RS bearings should have lower friction than bearings sealed on both sides. Enduro says that they offer some bearings with a full contact seal on one side and a medium-contact seal on the other sided. This is a possible compromise between friction and protection from both sides. As Kerin (link above) discusses, the exact type of seal can vary considerably from manufacturer to manufacturer, but he feels (based on experience) that -2RS shields from cycling manufacturers are likely to be low-contact seals, but among generic bearing manufacturers, -2RS might be anything.

From some sleuthing, it appears that Fulcrum's freehubs may have been equipped with -1RS seals. This YouTube video by Cycling Weekly offers a guide for servicing Campagnolo and Fulcrum freehubs. Starting at 6:12, the presenter confirms that the two cartridge bearings in the freehub (at least the one he serviced) are sealed on one side only. He says that he doesn't see the point in sealing on the other side, as it's not exposed to dirt ingress.

I am not positive about this. Say you get water inside the freehub. Depending on how you move the bike around, it might then intrude into the bearings from the unshielded side. I don't know how big an issue this could be, and I'd welcome other users' comments. In this thread on the BikeRadar forum, one commenter (Cyclobob) basically said what I did (water will eventually ingress through the unprotected side).

You might check the seal types on the bearings you ordered. The previous version of this answer said that I would be surprised if you had got -1RS bearings to begin with. I may have overstated things there! Nonetheless, if you have been getting -1RS bearings, then considering that you want to keep riding in the winter, it might be worth seeing if -2RS bearings improve durability. If you got bearings with low-friction seals, then you definitely want to find a full-contact seal.

This recorded conversation in the newsgroup rec.bicycles.tech (credit Sheldon Brown's site) alludes to some bearings with double contact seals or labyrinth seals. I have not yet found a cartridge bearing designation that specifically says they have these types of seal. It may be that there is not enough room in the common cartridge bearings to place seals like these and to maintain sufficient ball size to bear the loads. Or it may just not be common practice yet.

Grease in the bearings

Bearings are filled with grease. They may vary in the amount of fill. Less grease may produce less friction up to a point, but this will probably protect the bearings less. Phil Wood's site says that their fair weather racing bearings are 30% filled, and their regular bearings are 100% filled. On Slowtwitch.com, Josh Poertner posted that typical industrial bearings are 20-25% filled because they spin very fast and will eject grease if filled more. In contrast, bike bearings need a higher fill proportion, which adds miniscule drag but which prevents contaminant intrusion. He did not specify how much, but maybe more is better. If you over-fill the bearing, presumably it would eject the grease and you'd need to clean it up.

I'm not seeing fill rates specified on most of the bearing sites I've Googled, so I'm not clear how consumers might obtain this information. Nor is it clear what an optimal fill rate would be.

Note that it's possible to re-grease cartridge bearings. This involves picking one of the rubber seals out, cleaning out the grease, and injecting new grease. Do be careful not to damage the seal, but I believe careful use of a pick tool, or perhaps a pair of tweezers, would be sufficient. This Global Cycling Network YouTube vid demonstrates how to do this. They extracted the bearings from the hub before servicing. This vid by November Bicycles makes it clear that you may not need to remove the bearings, but it may depend on where they're situated. You could try re-greasing your bearings, perhaps halfway through winter.

One industry development that might be worth paying attention to is encasing the bearings in an oil-soaked polymer. SKF appears to have pioneered this design for use in food services, but it may be starting to move to bikes. As far as I can tell, the bearings are encased in a polymer that takes up all the free space inside the cartridge (recall: we would otherwise fill part of this space with grease). SKF argues that the polymer insert plus the external seals mean that contaminants physically can't intrude into the cartridge bearing. Normally, if you pressure wash the bike, the water might force the lip of the seal inside the bearing, but they think that there simply isn't any room for that to happen with this design. These bearings are cheaper than ceramic bearings, but are still fairly expensive. This development may be worth watching.

Manufacturing tolerances?

Manufacturing tolerances for the bearing could be an issue. For example, your 61903 / 6903 bearing has an outer diameter of 30mm. Really, this is 30.0 +/- x millimeters. If the bearing is too big for the hub's bore, this could be an issue. Most likely, some manufacturers have worse tolerances than others. However, I don't think there's a way for consumers to know this information. About the only thing you have to go on is general reputation. For example, SKF and Phil Wood have (as far as I know) good reputations.

Also, the tolerances of the hubs could be an issue. If the bearing seats aren't quite parallel, or if they're misaligned, this could cause your bearings to wear out faster. Again, I don't see a way to tell as a consumer.

Theoretically, a bike store could measure bearing sizes with an accurate pair of calipers as they come in and keep logs, but how many stores have time to do that? Relatedly, I think that Hambini has a video where he compares the variance in bottom bracket shell diameter among small samples of some common bike manufacturers, but again, it is hard to get a big enough sample as a consumer.

Bearing roundness (ABEC scale) - don't worry about this

You may see some bearings that are specified as ABEC-5, for example these units sold by Jenson USA (link only for example purposes). The ABEC scale is an ordinal rating of how round the balls are. The grades go 1, 3, 5, 7, and 9. My impression is that this is only one of a number of important characteristics for bearings in general. I think bike bearings may usually be grade 3 or 5, and that higher grades may offer no advantage for bikes. Our bearings don't rotate as fast as industrial ones). This online retailer and this article by Bike Radar seems to align with that point.

Bearing loads - this is a function of the hub design, and you can't change this post hoc

Last, the feedback I've got from mechanics and wheelbuilders is that small bearings will wear out faster. Adam Kerin (same link as before) appears to corroborate this. A bearing needs adequate size to bear the load. This isn't an issue with your hub, but I've had an ultralight front hub with 688 bearings. Kerin specifically calls them out as inadequate, and indeed, my hub bearings wore out very fast. You can't change the size of the bearings in the hub, and 6903 is a pretty common size for a rear hub anyway. However, where they're placed in the hub might make a difference, and also how many there are.


Replace solid axle with quick release on Fixed Gear This goes off a previous question:

Quick Release on Fixed Gear Bike

Suppose I want to replace my solid axles with quick release skewers on my fixed gear bike. Yes, I am aware that this isn't necessarily recomended, but done right it should be fine (i.e. enclosed cam qr skewer, chain tensioner like surly tugnut).

The spacing in the rear 120mm, what kind of quick release skewers do I get? I can't seem to find any with 120mm spacing. Is it simple to buy one that is ~130mm and shorten it? How do you do that?

Relavent links:

http://sheldonbrown.com/fixed-conversion.html#qr

http://www.bikeforums.net/singlespeed-fixed-gear/704523-quick-release-fixed-gear.html

This is easily accomplished, simply replace the axle from your wheel with a QR axle, at most you may have to cut an axle/skewer to length and maybe cut more threads if you can't find an axle and skewer with enough thread on it. But you'll need to be comfortable with cutting metal and have the right die set.

If you try shopping around for a 120mm rear QR axle, you'll have better luck looking for a complete hub and just parts it. They're not super common though, and not cheap...


How do I take apart the axle and freehub on this bike I have a long wheelbase recumbent built by Sun Bicycles.  There are some complications with finding out what kinds of components went into the interior of the bike.  Brakes and shifters have their brands labelled proudly, but the rest, not so much.  And the manual that came with the bike doesn't mention anything about advanced maintenance.

This is my first major bike maintenance project, going beyond my normal stuff of cleaning and oiling the chain or replacing the brake pads.  The entire drivetrain has about 5000 miles on it and needs an overhaul.  I can feel a lot of drag in both the front and rear axles.  Not grinding drag, but just sluggishness in turning about the axle.  So, I was taking them apart to figure out what components need replacing, and in both cases I ran into basically the same problem.

The front looks like this:

I've started to take off the lock ring here on the front hub.  That entire conical shape actually appears to be the front lock ring.  I can take it completely off, but once done, I have a lock ring on the opposite side, the axle sticking through the entire bike, and no indication that any part of it wants to come out.  So, problem the first... how do I get the rest of the axle to slide out?

The back looks like this:

On the opposite side, I just have an axle sticking out.  On this side, I have a freehub and an axle with a lock ring, and no clue how to get the lock ring loose so that I can pull the axle out.

What am I missing?  This should be relatively easy, but I've been banging my head against it for a couple of hours and making no headway at all.  My bike shop was closed today and is closed tomorrow, so I'll call them on Thursday if I'm still having trouble.  But, I wanted to ask here, first.

They both look pretty standard to me. Normally you remove the lock nut and cones from one side. The bearings should be visible and fall out (careful to catch them all.). The axle should then just push through to the other side. If you can see the bearings (or they fell out), a gentle tap, with a light hammer may be needed (although i cannot imagine why) to dislodge the axle.

With the rear wheel, remove the lock ring and cone from the left side (non-drive) and push the axle through (again, watch the bearings).


Convert Recumbent to Handcycle? Has anyone ever successfully converted a recumbent bicycle or tricycle to hand-powered?  How?  What are the major obstacles to overcome?

Do you want this as an able-bodied person to play with, or as a disabled person because your legs don't work? If the latter, (two wheeled) bicycles are out of the question unless you're young, fit, and slightly insane (I say this because it's certain you will fall off a two-wheeler, probably more than once, and if the guy I watched/helped is any guide, you are likely to also fall off at speed at least once).

The problems differ based on the type of bike or trike. The most suitable IMO for conversion are SWB ASS bikes (short wheelbase, above seat steering) and trikes. The "hand-pedal" part is the same in all cases. Look at any handcycle, but essentially you mount standard handgrips on bicycle pedal axles, then add brake and gear levers. The cables from those need to be long as they flex as you pedal. The pedals mount to standard bicycle chainring(s) and a standard "bottom bracket" (even though it's not at the bottom any more). That bottom bracket mounts to the top of the steerer tube and the chain runs to a standard bicycle rear wheel.

The trike will be easier to ride and harder to fall off, especially up hills. Handcycles go up hills very slowly. Most handcycles for wheelchair users are trikes, normally delta trikes (often with with negative trail). Negative trail makes them easy to build, hard to ride, and unstable at speed. But since you're already looking at a few thousand dollars, easy to build helps to keep the cost down. The more expensive ones are usually better designed for speed (however I have been very unimpressed with the ones I've seen from a rideability point of view). The conversion can be very easy - you "just" build an arm with a wheel at one end, pedals at the other, and a steering pivot in the middle. You can even buy those premade as wheelchair accessories (http://www.riomobility.com/en/manualhandcycle/index.htm). If you can do that, scratch building the seat/rear wheels shouldn't be too hard. "Conversion" now means "chopping up random bikes to get bits" rather than "add hand-pedals".

But very few foot-pedal trikes are delta trikes, and the ones that are are slow. That's because deltas are inherently unstable, especially when braking and turning (very common in racing or in an emergency). A second hand recumbent tadpole is also likely to be easier to find. Search for "recumbent trike" and you will find a lot of tadpoles, few deltas. Converting a tadpole you'll need to insert a bicycle headset into the frame in front of the seat/behind the cross-member, extend that up, then build your pedal/steering unit on top. The chain will twist when you steer, but that's ok (world record setting speedbikes commonly do this). The chain goes to the rear wheel, and you'll need two idler cogs to bend it up to your cranks. http://www.TriSled.com.au in Australia have built at least one of these but it was very expensive (take a $4000 trike, add a couple of weeks work to convert it to a handcycle). It did, however, work very well :)

Converting a SWB bike is likewise fairly easy. Remove the existing stem and handlebars, build your hand-pedal setup to plug into/onto the existing steerer tube, weld on a couple of idler cogs, and you're done. Don't paint it yet! First try riding it. You will fall off, and may decide to revise how the chain idlers work. The first mount you build may well not be strong enough, especially.

In both cases you will probably find that having the pedal unit pivot forward makes getting on and off much easier.

One other option is a rowing bike - Thys make them commercially, and apparently they're not bad to ride (but they definitely work your legs as well as your arms)


How to change small chainring I have a bike with a 46/36T crankset (FSA Gossamer Cross BB30) and I'd like to change the small chainring to an even smaller one.

Googling around suggests that the smallest chainring I can get for a 110mm BCD crankset is 33T. Is that right?

Furthermore, it seems that I won't need to replace anything else at all, not even the chain. I run an Ultegra RD-6800-SS rear mech with an 11-28T cassette and all the specs seem to check out:

Max front difference: 16T (in my case, 46-33=13).
Total capacity: 33T (in my case, (46-33)+(28-11)=30).

So just swap out the chainring and good to go, or am I overlooking something? (Never done this before.)

Finally, how do I make sure that the chainring I buy is compatible with my drivetrain? It seems that the BCD (110mm) is all that matters, so something like TA 110 PCD Zephyr would work?

P. S. As I am looking at a picture of the Zephyr chainring, I notice that it says "9/10 speed". What does that mean exactly? (My drivetrain is 11-speed.)

P. P. S. This page lists what looks like the same product as compatible with 8/9/10/11 speeds, but with the following cryptic remark: "For 10-/11-speed drives only with 1 or 2-speed crank handle!" Are they simply trying to say it's too thick for a triple chainset or does this refer to something else?

Most drivetrain setups have a 16 tooth difference between large and small rings.

Near compact: 52/36
Compact: 50/34
Sub compact: 48/32

You are trying to get a close to a super compact on a 110mm BCD and will have a chainring tooth difference of 13.

That means the rear derailleur will easily accommodate this as you have calculated.

The front derailleur will also handle the chaining size difference.

Chain length is set on the large chainring and largest cog sprocket, so you should not have to shorten the chain (assuming your chain is correctly sized to begin with). You will be within the derailleur total capacity so it will take up the extra slack.

If you do have too much slack in small ring and smallest sprocket, check the chain is sized properly.


V-brakes during winter? I'm considering some Schwalbe Marathon Winter tires so I can continue commuting to work during the UK winter ( -3°C to +8°C, with some snow and ice). However, I only have V-brakes. Are those brakes going to be acceptable in sub-zero temperature, occasionally while snowing?

Yes. They will be fine. Plenty of people use them in the Minnesota Winters without problems. Just make sure they are always in good shape, which is something you have to do with all brakes.


Please identify a bike that is like a cross trainer Yesterday I saw a strange looking bike that I would like to identify. Its features are:

Stood up riding position with no seat
Had cross trainer (running machine) pedals
Handles were similar to those of a child's scooter with a rubber grip
Located in Bradford, UK

I can't include images as I don't have the rep.

My question is, what is this type of bike called?

Sounds like an Eliptigo, as in  https://gearjunkie.com/elliptigo-stand-racing-bike.  They're intended to duplicate the exercise of running, but without the impacts of hitting the ground.

There isn't really a generic name for them, other than the class of "Funny Bikes" or possibly an "Exercise Bike"


Tyre liner causing a slow puncture -- am I doing something stupid On a beater bike I've got (25 year old Raleigh MTB) I run tyre liners because I had spare tyres and was too cheap to buy good anti-puncture ones.  They do their job quite well -- I've just picked broken glass out that had gone through the tread but stopped at the liner.

But the reason I found the broken glass was that I had a flat.  I knew the tyre was a bit soft but over the weekend it went right down.  On inspection I saw this on the outside of the tube:

That curve matches the end of the liner, and with enough air in the tube I could feel it leaking.

The liner doesn't feel like it has a rough edge (we'll find out because I left the liner in with a new tube), and it's been running fine for over a year.  This would appear to defeat the point of liners, so am I missing something?  Does too high pressure cause this? Too low?

I've never seen this exact flat, but I can see how it can happen.  It's why some brands of liners now have rubber tips at the ends of them.  a little filing just to be sure it's smooth there with an emery board should take care of it.  Or as suggested in the comments, a piece of electrical tape should help.


Tightening straight spokes Being faced with a wheel with these devilish things, I'm wondering how people keep them from twisting when tweaking the nipples.  I've been using a pair of Vice Grips, but that's clumsy and seems a bit crude for such exotic items.

Anyone got a better idea?

Note:  These are Easton spokes which are round, with the nipples in the rim (not "backwards" like some fancy rims).  The stub end is very slightly flattened, but there's no practical way to reach that end when the spokes are in place on the hub.

Aside:  I'll note that the Easton hub I've been working on is the devil incarnate.  To do any adjustment of the drive-side spokes one must first (per the manufacturer and my experience) de-tension the non-drive-side spokes 3-4 turns, then re-tension after the drive side is fixed.  Otherwise the drive-side nipples round over.

A Twist Resist will let you hold the spoke and resist the twisting. They're designed for holing spokes to prevent windup and spinning on straight pulls.

The internet says you can use a cable holder in a pinch, or even some smooth jawed pliers.

I'd be tempted to try thread lock on the hub end as a quick and dirty solution.


Rear Rack for Cannondale Trail 6 with Disc brakes I was having a real trouble finding a suitable rear rack for my bike, a Cannondale Trail 6, with disc brakes.

My usual bike use is to the office (bag containing laptop, lunch, rain jacket, etc. with approx 7-8 kg. weight), but sometimes I do take my bike outdoors, which may or may not require a rear rack.

So, my expectations from the rack are:

Easy to remove them when not needed.
Something that goes in the rear wheel hub (in the quick release notch), not something attached to the frame.
To take on 12 kg. weight.
Easily installable and serviceable by me. :)

Please suggest some options. TIA.

Another option could be the Blackburn EX-1 rack. I've used it on my cross bike due to it not having rack mounts and it carried my bike camping supplies quite well. It also comes with the long skewer. Also compared to a lot of racks it is fairly cheap.

Might not be quite as easy to remove/install if you don't have rack mounts.

Blackburn EX-1 @ Nashbar


Why are trigger shifters so widely used, instead of the twisting grip shifters(revoshift)? I recently rebuilt my whole bike. It was in terrible condition. I also decided to get a new freewheel with more speeds. While i was doing some research and looking through shifters and freewheels, i found out that the twisting grip shifters were limited to only 6 and 7 speeds. I couldn't find any twisting shifter with more than 7 speeds. I personally find them so comfortable, convenient, easy and way faster to shift than the common trigger shifters. I finally decided to get rid of the old 6 speed freewheel and install a brand new 7 speed freewheel with a huge low gear for crawling.
Why are trigger shifters so widely used? I don't see any advantage.
Update: Many people said that twisting grip get stiff over time and are difficult to twist. Yes they get a bit stiff over time, but from my experience they still aren't hard to twist at all
Below image of twisting grip shifter

In the context of a high-end MTB designed to go quickly over difficult terrain, trigger shifters have the following advantages:

They can be operated using only the thumb, without changing the grip, so the index finger is always ready to brake.
Getting mud on the gloves does not impair operation.

Modern grip shifters do exist, Sram makes a wide range of those, and in my experience, the cheapest option (the GX model) is very reliable and performs very well. For completeness sake, grip shifters have the following advantages:

Ability to shift through the entire cassette in one motion (assuming a single chainring setup, typical for the context), useful before a sudden steep hill.
Absence of a protruding element to be hit by the knee in case the leg unclips unexpectedly.


Bottom bracket damage work-around I built up a Specialized Rockhopper over this last summer, ending up with a sleek, blacked out, Deore & XT equipped thing of beauty.  During a brief stop at a buddy's place, the 12mm Kryptonite cable lock was forced and it was gone.  About five days later, I'd chased it down, finding it completely stripped.  Even the BB cable guide was removed.

I've decided to rebuild, mostly in hope of transforming my anger as much as the Specialized.  The left bottom bracket shell has some damage that concerns me, I'm asking for possible solutions and to run by ya'll my thought on a possible fix.

!

I'm going to face this left side, if only to remove the galled aluminum that sticks out past the original, proper edge.  Could one be more aggressive and remove 2.5 mm from the shell width on this left side (ending up with a 65.5 mm shell) then add a 2.5 mm spacer to bring the cup out to the 68 mm position?

Can I use that many spacers with outboard bearing cups? (There'd be 2, 2.5 mm spacers on both the right and left side).  I remember on cartridge bearing BB's that there is a limit to the amount of spacing tolerated and it's different for metal cups than if plastic.  Is there a similar restriction with outboard bearing cups?

Finally, is the frame ruined? (If so, somebody cue AC/DC's "Dirty Deeds" cuz it's gonna be my jam for a while).

You could most likely also instead do the following: face the frame by 2.5mm... don't install a spacer under either cup.. install them directly into the frame. When installing the left side crank slide a spacer (1 1/8 inch headset spacer for example with on side pressing against left side crank and other side pressing against the rotating ring on the bearing cup) over the axle of the crankset before proceeding to install the left side crank arm. Make sure to choose a spacer with just enough thickness to ensure you can adjust it so there is no play on the bearings/crankset axle. I've done this on one of my mountainbikes and ridden it for well over two year without issue.
Using this method you have the entire bearing cup's thread length engaged in the frame even after facing off 2.5mm (or another amount for that matter).

Your suggestion of facing off only the called aluminium sounds like a good option to me. I believe the amount/total thickness of spacers underneath the bearing cups is limited because there needs to be a certain length of thread engaged to aquire the required strength. This would also explain why it differs between metal and plastic cups (since the latter have much stronger threads). This being said a 2.5mm spacer shouldn't cause any issues based on my experience. Perhaps you could consider tightening the bb cup on the faced side a little less (make sure it's properly snug though otherwise you'll ruin your threads most likely ... As is also the case when not tightening a pedal correctly and using the bike after) and installing (high strength?) Loctite or another thread locker to prevent the cup from loosening. .


Shredded bits of material under my trainer I'm starting to get a pile of what looks like tire rubber under my trainer. Could it be something else like dry chain lube coming off? Is this normal? Have I set up my trainer incorrectly? Do I just have to accept that my rear tire will need replacing in the spring?

Yes, its tyre rubber.
People typically use either old/worn, cheap hard compound or dedicated turbo tyres for this reason with wheel on style trainers.
The bad news is that more typically sprays off backwards than down on the mat where you see it, so there's a good chance the rest of your room has a light coating of rubber particles too!


Is "bike fit" through site reliable? I want to buy a bike, in this case a moutain bike, and the salesmen always ask my height, I am 1.90m, searching the Internet I heard about "bike fit", so I found some sites that through the measurements of your body suggest which dimensions Should use:

https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp
http://www.argonautcyclecoaching.com/index.php?p=bike-fit-calculator

In my region to make a "bike fit" they charge about $ 600, I found it very expensive, being that I will use the bike to get to and from work (14km).

I wonder if it's really good for me to do, or trust these sites?

P.S.: Translated via google translate, corrections are welcome.

A $600 dollar bike fit would be a professional fit where the set the bike up, adjusting everything to the last millimeter, replacing components as required and making the bike as fast and comfortable as humanly possible. Such a fit will save you a few seconds over a hundred kilometers of riding. For a 14km commute it is not needed.  (Everyone would benefit from a good fit, some more so due to discomfort and bio-mechanical problems, but the gains of spending the time and money quickly diminish)

When buying a bike, the most important thing to get right is the frame size, everything else is adjustable (with or without replacing parts). From a simple sales perspective, frame size is determined by height and will probably be correctly chosen 90% of the time using just height.

Best thing to do is buy a bike from a reputable LBS. At no extra cost they should help you select the right bike (size, style etc), and set it up to fit you. They won't go as far as the $600 fit, but should have you riding out of the shop on  a bike you can comfortably and reasonably efficiently ride for the distances you are needing. (Things like seat height, handle bar height etc).


Dawes Super Galaxy - Tubes I picked up a near new Dawes Galaxy that had been in storage for 8 years. I'm super excited to get on a tour. I have both Lands End to John O'Groats and London to Paris locked in:)

The tires are marked Schwalbe Marathon 32 - 622 (28 x 15/8 x 1 1/4 - 700 x 32c) hs308. Tube markings have always confused me, and I'm sure it gets asked here all the time.

What tube should I be looking at here in the UK as a spare?

Will this one be OK?

Yes, the number most usually listed is 700x32, so anything with that in the range will be the right size. You can even get away with slightly bigger or smaller tubes in a pinch.

The ones you linked to should be fine, or try these from Schwalbe. Some people recommend Schwalbe for reliable tubes as well as tyres.

Note valves: It might matter whether you currently have Schrader (like a car tyre) or Presta valves. If you have presta, the Schrader tube valves might not fit through the hole in the rim. Probably simplest to get the same kind.


How to remove a seized & snapped bolt and extractor from a welded titanium cage boss I have a titanium frame with aluminium bottle cage bolts screwed into it. I tried to remove them the other day and one of them snapped off at the head.
I drilled a hole through the remains and tried using a reverse-threaded screw extractor to back it out. Unfortunately, this happened:

The bolt is seized so badly that a steel screw extractor snapped before it broke loose. Now I have a chunk of steel in an aluminium bolt in a titanium frame. What options do I have?

The first thing I would do is assess the question of what happens if your efforts result in the eyelet threads getting wrecked. Is the eyelet and its welded connection chunky enough to fix it by helicoiling? Look at a helicoil tap chart. Does it have enough meat to handle a 6.145mm hole in it?

Then look around a little at the ti framebuilding suppliers to get an idea how big the hole in the frame is. Is the eyelet basically this thing, 10mm flanged top and 6.5mm shank dia?:

(6.5-6.145)/2 is not much but it's not nothing. Is the bead placed in a way where it's going to shore things up at all, or is it only connecting to the top flange? Ideal would be if the helicoil threads get at least 6mm worth of chunky material to reside in between what the flange and joint give, so the 3.55/2 part isn't being asked to do anything structurally. 5mm would probably fine, and less than that I don't love.
If you can helicoil, life is easier. You can try and brain surgery your way through and keep helicoiling as a backup plan, or you can skip that part and obliterate everything and just helicoil it, that's up to you. Proceeding in a way where the threads remain intact at all costs is more perilous and time-consuming.
Broken extractors can be a big problem because they're made of such hard steel. There's a hierarchy of tool hardnesses in industry and extractors are around the top of it because they're intended to be able to bite into fasteners that themselves are made of hard stuff, like stainless or grade 8 bolts.
This is what I would do if I had to tackle it:

This kind of Dremel bit, a round carbide burr (probably some other names too) is the most effective thing I've found that can cut into the broken stub without wandering around. The challenge in situations where you ultimately want or need to save the frame threads is you have no forgiveness for the tool wandering, and this is the safest way I've found of addressing that. (You have to be very careful, go slow, hold it firm but don't force it, and all the other usual precautions). You could try to go the whole way with it, or just establish a hole/divot to start a drill. For a drill to follow it, you need something made for drilling hardened steel, i.e. proper fancy carbide bits.
So you can use the round carbide burr and, optionally, your carbide drill bits to gradually get through the broken extractor. Once that's out you're back to where you started. What I would do is take advantage of the relative high hardness of ti by switching to a drill hardness that will be effective against the aluminum but bounce off the ti, like say a wood-oriented bit, making it easier to get through without hurting the threads. Cut out as much of the aluminum as possible with this succession of drill bits. If you nail it up front with your perfectly placed pilot hole, which the round dremel burrs can help create, you can use your series of larger drills to clear away enough al to have the peaks of the frame threads poke through.

We see that transition happens at about 4.134mm. So looking at a drill bit size conversion chart, we see from an imperial set it's between 5/32 not quite taking you there and 11/64 being big enough it starts eating frame, but there are some other sizes that do take you right to the cusp if you're willing to order fancy drills from the internet:

In other words, 11/64 takes you there but also works against you if you're trying to save the frame threads. A maximum case attempt at saving them would probably involve getting a 4.1mm bit.
Once you're there, looking at the remains of the bolt and the peaks of the threads poking through neatly, I would try to dig in with a stainless steel scriber on the top, trying to clear away enough that you can begin to get a tap started into the threads. You can be aggressive since the ti will be harder than the stainless. One of the things working in your favor if you take it this far is that the sections of thread that aren't corroded in place will start falling away.  It may be easier to use a bottoming/plug type M5 tap, which is a good reason to have them around. Once you get it started into the frame threads, you should be able to use it to clear out material the rest of the way down. Understand that the whole trick to this stage is that you're trying to get a tap started into the frame threads. You're not trying to just jam a tap into a seized-together mass of frame thread and broken bolt. If you do, you may start cutting new threads overlaying the frame threads, which will tend to ruin them. The suggestion of a bottoming tap is because it's not tapered, so it may be easier to start with confidence. When it's an aluminum bolt, this part will tend to be easier, because any tap should clear it out easily.
Another thing you could consider is going to an M4 helicoil, if it's dubious whether you have the material for an M5. A steel M4 bolt is sufficient for a bottle cage, and this way you're not flirting with taking away too much material. It won't look like new though. To make this work you would be creating a new set of threads that overlay the old ones and hoping it would be strong enough, so it's last-ditch, but may be something to try as a bailout plan if you reach a point where the threads are ruined and you don't think there's enough material to enlarge the hole.
Note also that everywhere above where I talk about an M5 helicoil, you could substitute the plan of going to an M6 thread, since the hole size is close to the same. It's actually a little bit smaller, so perhaps there's a scenario where M6ing it is a better call. I kind of hate doing this to bikes, especially nice ones, but there may be a scenario where it's appropriate.


When turning a corner my rear wheel touches the brake pad, is this normal? I replaced my brake pads about a week ago and today I noticed that, when turning (or generally under lateral force), the rim touches one of the brake pads (depending on which way I'm turning.

I hadn't noticed it before but today was the first wet day so maybe the sound was louder because of this.

I don't notice myself slowing down at all, but don't really want to be unnecessarily wearing down my brakes.

The brakes aren't super close when released, maybe 2-3mm on each side.

I would expect a certain amount of flex in the wheel, but as I built the wheel myself I just wanted to check that this wasn't a problem with my build (though its already done 1000 miles probably so it cant be too bad!)

There would be room to widen the brakes slightly if this is all that might be required.

When stationary and holding the wheel and applying lateral force manually I can make the rim touch either brake pad without a great deal of effort.

Any input appreciated

Thanks!

You should check the wheel hubs. They may have too much free play. Take out the wheel and wiggle the axle. See Sheldon Brown's page here: http://sheldonbrown.com/cone-adjustment.html
The new brake pads may be closer to the rims than the old ones so that the fault showed up.


Help decoding a J.C. Higgins frame number on a vintage cruiser The serial is 502 46560 887408. The bike is complete, I may fix it up as a cruiser, or completely restore it depending on parts availability, but for now I'm trying to find out the basics. I can see a bracket on the head tube, perhaps it once had a tank?

4656 is the model number.  It's also the order number in the catalog.  There are books for sale on Ebay that show the bicycle pages from the Sears catalogs that cover Elgin, JC Higgins, and Sears bikes from the early 30's through the mid 60's.  Each page tells the year from which the pages are taken. Match the number on the bike to the cataolg number and you can figure out the year and style.  The 502 is Murray Bicycle's code for the bikes they built for Sears.  The last six numbers are the bikes individual unique serial number.


Can I replace my Shimano RX 100 with a Campagnolo group? I just purchased a Concorde Mistral with Columbus Gara tubing and would like to transfer my Campagnolo group from an SLX frame that is too big. The Concorde frame has a front derailleur mounting bracket on the seat tube just like the SLX frame I already have. I understand I would be losing the indexed feature the Shimano has, but would it be possible?

As Pete H has commented, a partial swap will probably not work out.

On frames / bikes of this age, things were easier as compatibility was not quite so much of an issue, so some elements could probably work together OK - but if you are not sure / inexperienced, best is to swap everything.

Worth checking, though, that the threads for the bottom bracket on both frames are the same - some Concordes used to be Italian threads, your existing frame may be Enlish and they are not interchangeable.

To check which you have, measure the width of the shell, width-ways (i.e don't try and measure the diameter) excluding the cups that screw into it - 70 mm Italian, 68 mm English.


Rear tire has started rubbing frame at one spot Riding my bike within my suburban residential neighborhood, I felt a shock, like a snap although I don't think anything snapped, followed by a rubbing noise every few seconds. Pedaling and the brakes continued to work.

I pulled over and examined my bike, starting with the brakes, and discovered that the left side of the rear tire now rubs against the left chain stay at one spot, near the tube valve stem. The wheel/tire is perfectly centered everywhere else along its circumference, just not there.

I've had this bike for about a year (bought at Goodwill), and, aside from a break over the winter, I've been riding it at least once a week, and I can tell you that this didn't happen before.

I haven't done any hard riding recently; I've been taking it easy as I build back up from my winter break.

The tire is seated correctly on the rim, as far as I can tell.

I didn't count the spokes off one by one, but looking at where they each meet the rim, they seem to all still be intact. There weren't any dangling off or obviously snapped away.

The bicycle is an old Univega hybrid bike with 700c Bontrager tires. I'm no expert, but I'd describe the tires as road tires, about an inch wide.

I'm stumped for what's caused it or how to fix it.

Check the spokes - its likely one or more has broken ("I felt a shock, like a snap....".). The ones to check are ones that got from the rim, where the rubbing is occurring, to the hub on the opposite side of the rubbing (in your case, the right side of the hub). If these have let go, there is nothing stopping the rim being pulled to the left.

It may be that these are loose, not broken, although it unlikely. If the spokes are not broken, you might be able to straighten the rim by tightening the right side spokes and if needed, loosening the left side ones. It's not too hard if the rim is not too far out of true, but needs patience for a novice.

If there is a broken spoke, or the rim is a long way off and cannot be "tweaked" it will be worth taking to your LBS to get them to look at it. As it's only a year old, spokes should not be breaking.


handlebar under-tape (extra layer)? I'm going to be re-taping my bars for the first time soon, and I was thinking about a putting an extra layer of tape for just slightly increased diameter and padding. I have big hands, but I don't want the padding kits that are available, as I think that might be too much.

Is this under-taping at all common? I was thinking about using cloth medical-style tape. Would this be a good choice?

(I don't race, just exercise/commute/day-trip, will be getting compact drop-bars)

Double taping or double wrapping is definitely common, and as with all things bicycle there are various opinions on the best way to do it.

I do it mostly for comfort, although as with many others I do have hands big enough to comfortably hold the bars when they're bulked up like that (I'm using two layers of foam tape rather than an under-layer of cotton tape).

I'm not sure there's much advantage to using a layer of non-padded tape, but if it works for you go for it. It's easy enough to remove, so at worst you've lost whatever you paid for the tape.

What I usually do is buy bargain-bin tape for the bottom layer because no-one sees it, and I'll often wrap top-down because I think that works better. I don't tuck the first set of tape into the bar at the bottom, only the outer layer starts tucked in. And I'll often run the outer layer a turn further up towards the stem so it's anchored onto the bar rather than just the first layer of tape. I get that extra tape by only wrapping round the brake levers as little as possible (ie, I don't do the extra figure-8 around the levers), partly because the extra padding often spoils the feel of the levers.


Fork damper circuit reconditioning I have a rockshox Dart II from 2007. I have recently rebuilt it for the first time in 9 years as it had basically locked up, and not so surprisingly given its neglectful treatment, its still not really doing what it is supposed to. while the fork drives with significantly less stiction and reaches its travel limits, there is so much rebound, even when the adjuster is fully open, that it would probably be better suited on my car. I assume the rebound and compression have had it, but I wonder if there is a fix that doesn't involve buying a new one.

Short answer, no, there isn't a non-replacement option at this point.

Partly because the Dash is a very basic shock, and thus repair becomes not cost effective compared to replacement.

Repair in this case involve replacing the damping cartridge, seals, and oil, which is basically all the internal parts if it's an air sprung model.

(A coil spring model would also have a spring side.)


Why does my drivtrain skip under hard torque? I recently purchased a new bike, a Specialized hardtail mountain model.  It is on the cheaper side, but with the brand I expected a good ride.  Less than a month of riding it, the drivtrain has started skipping.  Under a hard torque load, the rear drivtrain will "chink", and the crank will slip forward just a little.  It only does this in a few gears, specifically 7 and 8 on the back with the middle chainring. Shifting down to 6 usually stops it.  As it is good quality, brand new bike I did not expect this.  I looked at the rear derailer, and it appears to be ever so slightly bent, but i dont think this is the problem.  It is hard to look back while pedaling hard, but it doesnt look like the chain is trying to go up or down a gear.  Since I got it, I have given it a good wash and lubed everything back up, but the problem remains.  It is a less expensive bike, so I expect to replace some components eventually, but I would like to get my money's worth from the old ones first.   Also, I live over two hours from the nearest bike shop, so any help here would be appreciated.

Skipping like that is usually worn cassette, chain or chainring(or all 3).  Considering it's only doing it in the highest gears, my first guess would have been the cassette.  But since it's only a month old, it's much more likely to be the derailleur is mis-aligned just a little bit.  You say the derailleur is "ever so slightly bent", that little bit can make a big difference if it's out of alignment with the gears.  Also, as Criggie says in the comments, the cables "settle in" a little after about a month or 2 of riding, that's very common, and the reason most shops offer a free tuneup in the first year you own a new bike.  May be worth checking to see if the shop you got it from offers one.


Hey my right gripshift won't turn, need help My mongoose bikes right shifter won't shift, it's too hard or stiff and the wire that connects to the gripshift is loose which isn't normal because the left shifter is in place and not loose and works. So any help would be appreciated.

Sounds like the gripshift itself is broken.
The usual process to diagnose jammed shifter or derailleur problems is to disconnect the cable at the derailleur, check the derailleur will move through it's full range, then tension the cable and work the shifter to make sure it pulls in and pays out cable.
If the cable is loose but the shifter will not move something must be jammed in the shifter itself. Try disconnecting the cable at the derailleur and pulling it out of the shifter. The head of the cable might have come off and has gotten stuck in the shifter.
If you can't get the shifter to move with the cable pulled out replacing it is probably the only option.


How much food should I carry cycle touring and what factors affect this? I am planning a cycle tour that will pass through some areas where I know there will be plenty of access to food and some areas that will be away from food for a day or two. I am going to Turkey, Georgia, cycling down through Azerbaijan, Armenia and Iran. I envisage that food will be easily available in Turkey, Georgia especially in towns but less so in remoter parts of Iran as my route will go through some of the lesser populated areas.
Any advice appreciated.

I fear that the only useful answer is also the trivial one: you need one days food for every day between food supplies. Eat whatever you can get, and as much of it as you need.

My practice on longer tours is to have a "standard days food" made up of long-lasting items. Usually rice with milk powder, sultanas and sugar for breakfast (it's compact and keeps well) and noodles, beans and dried veges for dinner, then some sort of cracker biscuit with spread for lunch. These are bought wherever I can, so vary depending on where I am. But that's my fallback stuff, and I often carry the same 3-4 days worth of those for weeks at a time. But it means that as long as I have or can find water, I can cook and eat. I'll increase the stock if I think I'm going somewhere that doesn't have supplies, aiming to always have 3-4 days spare. Remember that a days riding is 3-5 days walking if your bike fails and there's no-one around to give you a lift, so plan to be able to get yourself out on foot if you have to.

Wherever I can I buy a day or two worth of fresh food and live off that. I'll buy muesli, milk, bread, fresh fruit and veges and eat them in whatever combination works (usually the more fragile or fast to go off first, leading to "watermelon, lettuce and avocado salad" for breakfast). Expect to eat local food, and be ready to live off local staples if you can - that will make your trip more interesting as well as cheaper.

I also carry small, robust gift items that are relevant to my story to give to people who provide hospitality along the way. I find that especially where I'm unusual local people will often be happy to talk to me and invite me into their homes. I will often trade an evening of story-telling for a meal and bed, then leave a thank-you card (cards are a photo of me with my bike, in a scenic location, and have my contact details inside). In the first world that's generally all I'll leave, because that's more than most people expect. They stick it on the fridge and it works as a conversation starter for months :) I find personal business cards very helpful too for giving to random people who are interested in you. Get them plastic coated or whatever so they last a bit longer and can survive a bit of dampness.


Are rear derailleur cable intervals equal? On one occasion in the past I paid attention to get the rear derailleur to be "just right". On eight gears on an MTB, I would get gears 1-2-3 and 5-6-7-8 to be perfect (minus the chain rub on one end or another, depending on the FD position), but I couldn't eliminate a nagging problem from gear 4. On occasion, the gear would shift back and forth between gears 4 and 5.

I'm now tuning a new bike, road this time, and would like to understand enough to never experience this again.

From "How to Adjust a Rear Derailleur – Limit Screws & Indexing"  I pulled this image:

The image clearly shows that the distances moved by index shifting are not equal.

And so I'm now telling myself, perhaps my unsettled gear #4 was due to my having in the past pulled the cable too far in one direction or another. I was using the barrel adjuster to fine tune the derailleur under a cog, but the cable as a whole was misaligned. A picture will illustrate why this matters.

For some geometric reason, perhaps the misalignment didn't affect gears 1-3, 5-8, but affected gear 4.

Can this happen? I've never seen what's inside an index shifter. Will it happily shift beyond its range, stopped only by the limit screws?

As I no longer have that MTB, I don't really care at this time why gear #4 on that bike was sometimes unsettled. But I do want to understand:

Are rear derailleur cable intervals equal?

If the intervals are equal, then there is no issue. Shifting the cable cannot misalign the settings.

If the intervals are not equal, then something (the limit screws? the shifter? ...?) should stop the amateur mechanic from misaligning the entire cable.

Your assumption is that there is an unlimited number of clicks in the indexing inside a shifter. There aren't. For rear derailleurs shifters there is one click for each gear in the cassette. (i.e. a 10 spd shifter has 10 clicks). If you mis-align the clicks, you only get 9 gears not 10.

Often the indexing is setup to pull a larger amount on the biggest cog ( or lowest gear) in the rear cassette. It's tuned by the manufacturer to get the best shifting performance based on the typical cassette used in the group.

I suspect the issue from your older bike was not due to indexing, but due to a worn cog in the cassette. One gear in the middle just being flaky is a common symptom of a worn cassette and chain.

Cogs don't get the same amount of use or force through the chain so they often wear at different rates, especially if you don't replace your chain often enough. If you want the best shifting, get a chain gauge and check your chain for wear at regular intervals. My strategy is to buy the cheapest chain that works and replace it often.


Checklist for Gates Beltdrive conversion... Having had a good look at a Scott Sub 10 1012 model today I'm very very VERY keen to convert my On-One Pompetamine Versa 8 to belt-drive. It has a Shimano Alfin 8 hub.

So... what advice can you give me? So far I know/think that:

I need to get the read-triangle on the drive side cut and have a gate brazed in (I'll do this myself probably).
I'll need to get hold of an Alfin fit sprocket.
I don't have an eccentric BB mount/shell so will have to tension with track-ends and tugs (or will I??)
That it's blinking expensive :)

Thanks!

The biggest hurdle is definitely engineering the split dropout or the separable chainstay. S and S Machine doesn't sell their S&S couplers to amateurs, so the most elegant method of splitting the chainstay proper isn't really available to you.  Other methods - using flat stock or other threadings - are likely to provide endless headaches there. Gates publishes a spreadsheet containing engineering documents for a few different dropout designs, you could possibly make them or get them manufactured to your specification by a local machinist and braze them ion, but once again you're looking at some significant expense and complexity.  There are a few other dropout designs as well, but they appear to be proprietary.

Ultimately you're looking at a sub-$300 frameset; you might be best off finding a Gates-compatible mass-produced frameset and moving all your parts over to that.


Is it safe to cut off from the inside of my helmet? Having a rather "pointy" head (think of something like Patrick Stewart's head), all bicycle helmets I've every tried on tend to have contact with only one point at the top of my head.

Now my idea was to cut a little bit away from that rigid foam at that location. Let's say 1-2 millimeters at the size of a dime.

My local bike dealer told me that the whole helmet has a fine-tuned structure that completely breaks down when removing even the slightest piece of rigid foam, no matter how small.

While this sounds strange to me, I'm confused right now.

Therefore my question is:

Does a bicycle helmet still has protection when slicing some 1-2 mm from the inner rigid foam at a size of a 1-2 cm circle?

(I'm from Germany, in case this matters; maybe our helmets here are different)

Unbeknownst to many consumers, different helmet manufacturers use different molds for their helmets. Just like some shoe brands are known to be thinner or wider than other brands, some helmets are more oval, some more round, and some pointier. Even from the same manufacturer, their racing models might be different from MTB, skateboarding type, and general lines. And there might be a helmet with a vent hole in exactly the right place out there.

It's important to find a helmet that fits correctly and comfortable. It might take having to go to different stores and trying different brands and types (or even to a store in a different country, if you have the opportunity).

That being said, through, if it were my head and I had to decide between a helmet that was partially shaved to fit -- or a larger helmet with some extra padding to fit; I would choose the latter. The helmet manufacturers provide extra padding pads of varying thickness in the box because they know they can't produce a helmet that fits perfectly on everyone's head. As long as the helmet is snug on your head and not uncomfortable, you should be good to go. Remember that many cyclists wear beanies in the winter and cycling caps in the summer under their helmets -- something that is well known to the helmet manufacturers.

Remember the worst helmet is the helmet you don't wear.


Could anyone help me resolve the differences between these two BMX bikes? I'm deciding between those two bikes and since I'm not a pro, I cannot spot many differences. I was hoping you guys could help me out.

One notable difference I know of is that Mongoose Capture 11 has more rims than its competitor, I hope that's a good fact, right?

Mongoose Capture 2011 specifications:

Frame:  Full Hi-Ten
Fork:   Full Hi-Ten
Crank:  3pc Tubular Cromo, 170mm,33T steel chainring
Bottom Bracket:     Mid Sealed Bearing8 spline
Speeds:     1 Speed
Cog Set:    Odyssey 13t freewheel
Wheels Size:    20"
Rims:   Alloy 36H front, 48H rear
Hubs:   36H Steel, 3/8" axle
Tires:  Innova (F&R) 2.125
Pedals:     Mongoose Nylon Fiber
Brake:  Pro Rush with Pipeline cable
Handlebar:  Mongoose Hi-ten 7.5"
Stem:   Mongoose Front Load50mm Ext.
Headset:    1-1/8" Ahead
Brake Levers:   Rush RX402 hinged
Spokes:     ED Black Steel
Grips:  Mongoose Kraton
Saddle:     Mongoose Slim
Seat Post:  25.4 straight steel
Seat Clamp:     Alloy single bolt slim
Extras:     1 pair axle pegs

GT Slammer 2011 specifications:

Type of Frame   GT freestyle design, Steel tubes, DT gusset, American BB, seat stay mounted U-brake, GYRO cable guides
Fork    GT freestyle design, hi-ten 1-1/8" steer, 31.8mm hi-ten blades, 6mmT. Dropouts
Crankset Chainwheel     Forged steel one piece crank, 170mm / 33T steel GT design
Bottom Bracket  American loose ball type
Cog Set     DNP 13T. Cr-mo
Chain   KMC Z510
Rims    Alex G303, pinned aluminum, 32F/36R hole
Front Hub   Steel body, 3/8" heat treated axle, 32 hole
Rear Hub    Steel body, 14mm hi-carbon axle, 36 hole, single FW threads
Spokes  14G
Nipples     Brass
Tires   GT Air Bags, 2.1"
Pedals  GT Jump design, PP material
Front Brake     Rush 900D, aluminum Caliper
Rear Brake  Rush 933D, aluminum U-brake
Brake Levers    Tektro 289A full aluminum lever and clamp
Handlebar   GT dirt/street Steel, 7" rise
Stem    GT freestyle drop design, machined GT logo
Headset     1-1/8" threadless, steel
Grips   GT Wing shroom design
Saddle  GT Slim mini street design, 8mm rails
Seat Post   Steel, 25.4mm x 200mmL.
Seat Clamp  Alloy Single bolt
Extras  SST ORYG, one pair GT 36mm OD x 97mm forged steel pegs

UPDATE

After what @mathew suggests, I have found 2 other competitors:

GT Performer 2011 for $369, of which the description says:

Type of Frame   GT Freestyle Design Frame with Cr-mo main tubes, machined 1-1/8" headtube, 19mm CS, DT gusset, Mid BB, seat stay mounted U-brake, and GYRO cable guides
Fork    GT freestyle design, Cr-Mo 1-1/8" steer, 31.8mm hi-ten blades, 6mmT. Dropouts
Crankset Chainwheel     GT tubular Cr-Mo 3pc., 8T spline, single bolt clamping, 175mm / 25T steel GT design
Bottom Bracket  Mid size sealed bearings, 8 spline Cr-Mo axle

Versus Mongoose Article 2011 for $329, which has:

Frame:  CromoFront Triangle
Fork:   Cromo Steerer
Crank:  3pc Tubular Cromo, 175mm,25T steel chainring

Is any of these latter two better/worse, or are they the same?

The heart of a bicycle is the frame - even on a BMX. Both of the models that you are looking at use high-tensile steel rather than steel alloyed with chromium and molybdenum ('cr-mo' steel).

With a normal bicycle made of high-tensile steel the problem is the weight - the frame (and fork) weighs significantly more than it would be if it was made of a better 'cr-mo' steel.

On a BMX bike the problem with high-tensile steel is not just the added weight. High tensile steel bends whereas 'cr-mo' steel flexes. You need this flex if the bike is to survive crashes as well as intended heavy impacts.

Given that there is a premium attached to 'cr-mo' frame/fork many manufacturers replace one or more tubes in a high-tensile steel frame with 'cr-mo' tube(s). They can then put a sticker on the frame claiming it is 'cr-mo'. This gives the impression that the frame is 'cr-mo' when it might be mostly high tensile steel. Therefore, when comparing bikes, look at the frame and fork to see how much of it is 'cr-mo' and how much of it is high-tensile steel. Get this detail right and go from there. Components can be replaced - if the bike comes with cheap plastic pedals then you can upgrade them to something more desirable when they break for a modest amount of money. So get the frame right and look for something with 'cr-mo' at least in the main tubes.

EDIT:

The GT Article and the Mongoose Performer are very similar in specification. The separate seat clamp on the GT is a neat touch, the frame also appears to be chrome plated rather than painted. Personally I prefer the chrome plating as it can be polished up very easily to remove rust spots whereas the painted frame shows damage that bit more evidently. There is little to choose between the components, so on the basis of the chrome plated frame I would check that it is (and not just painted silver) and go from there.

The slight complication and opportunity is with the pricing. There are new 2012 versions out of both of these bikes. Some dealers may therefore want to discount the 'shop soiled' 2011 models that they have in stock so that they can get the 2012 models in. You may want to look at the differences in the model years to see what those differences are, maybe it only comes down to paint scheme, but, with a bit of shopping around, you might be able to get yourself a deal.


Back pain when cycling up hills There are lots of questions here about back-pain, but generally about cycling in general and cycling on flat surfaces.
I am after more practical tips on avoiding back pain when cycling up hills - with gradients between 10 to 22% (moderate to steep!).
Any suggestions?
I heard regular core stretching and exercises helps with this considerably.

There are so many factors involved that can lead to back pain that I would be suspicious of anyone providing the answer.

Some factors that can affect

Your current bike fit.

Body angle: is your current fit very aggressive or more relaxed?
Is you seat set back appropriate or too far back?
Is your saddle height correct for your level of flexibility?

Your Technique

How do you position yourself on your bike  when climbing  (e.g., do you use the tops of the bars or do you get in the drops)?
Do you spin or do you mash gears

Your current bike setup

What gearing do you currently have
Is this gearing sufficiently low enough for climbs

Other personal factors

Have you injured your back before
What is your hamstring flexibility
What is your mid and lower back flexibility
What is your hip flexors flexibility
The list goes on

Summary

After addressing all of these issues I would then start looking at factors such as core strength, functional weaknesses and associated exercises.

In short, narrowing down the cause of back pain is often can be difficult.  I would suggest finding a someone who specializes in both physio and bike fitting. They exist and will likely be your best bet at tracking down the cause and finding a solution.


What proportion of adults in Britain can ride a bike? I'm guessing it's a very high proportion, but has someone got a reliable statistic for this?

This may be the closest you're going to get.  It's not an exact match:

It's England not Britain
It's not how many can ride a bike, but how many do

Sport England's Active Lives survey says that 6 million adults in England cycled for leisure/sport and 3 million for travel at least twice in 28 days, over the year to November 2019.  Extrapolating from demographic data for England, there were about 43.6 millions adults in England in 2019, which means something like just 14--20% of English adults ride at least twice a month (13.6% assumes that all the "travel" riders also ride for fun, while 20.6% assumes that people only ride for one or the other, never both.  The latter is clearly unrealistic, so I'd assume closer to the lower figure.
This is in decent agreement with 2018 figures saying 11% rode at least once pre week (8% leisure, 6% travel). These 2018 figures are at leats partly based on an earlier version of the Active Lives study.
I think it would be reasonably accurate to assume the same proportions across the UK as in England.

Trying to figure out how many can ride is harder, but I'll have a go.  There are hints from recent data suggesting many people got back on their bikes in lockdown.  Figures from Scotland show that in some places recorded trips doubled, however that could just be the same riders going out more.  Cycling Industry News reports comparable figures.
A survey for HSBC/British Cycling (reported in BikeBiz) says that 19% of UK commuters are more likely to cycle to work post lockdown.  That strongly implies that at least 19% of commuters are capable of cycling.
Of course, when you consider whether someone can ride, you have to think about whether they can wobble along a deserted path, nip through traffic, or somewhere in between.  Crucially the context in which you ask someone will affect their answer - I'd expect a larger proportion of people to say they could ride if prompted by pictures of a nice peaceful path, compared to a rush-hour city.
Realistically, based on what I've quoted above and in the absence of hard figures, I'd estimate that a bit over 20% are capable of riding for practical purposes, while far more can handle a bike in ideal circumstances.


Shimano Claris FH-2400 Rear Hub Dimensions I would like to purchase this hub, rim and suitable spokes, but I am not able to find dimensions of this hub necessary to calculate spoke size. I have checked usual places where such information can be found, but without success.

Does anyone own this hub, and has taken its measures?

Details found here: http://productinfo.shimano.com/specifications.html

Spoke Hole P.C.D. Left/Right (mm) 45
Flange distance (mm) 57.9
Dish (mm) 8.4

Based on these figures, I would calculate the following values for your chosen Spoke Length Calculator:

Centreline to Left flange: 37.35mm
Centreline to Right flange: 20.55

Spoke hole diameter is not given.