Chainring rubbing frame after tightening cranks. What should I change? Bike details:


Singlespeed (steel)
Square taper threaded BB
58/19 ratio (hence huge chainring rubbing the frame)
130mm bcd 5-bolt crank/chainring
Mileage on cranks: several thousand km in all weather (tropical climate)
Riding purpose: commuting, ~125km per week, with sporadic longer rides.


Background info:

I have this ridiculous tooth count due to component availability at the time of setup. Initially, there was a clear gap (around 1-2mm?) between the chainring teeth and the frame. All was good.

Almost two years and thousands of kilometres later, the cranks started to get loose (creaky on downstroke). After having to tighten the bolts twice over 2 weeks, I removed the cranks, cleaned and lightly greased the spindle (yes, I know, this is a point of contention too) and crank holes, and re-installed them (I do not have a torque wrench... let's just say they're tight enough but not too tight).

Now the chainring rubs at certain crank positions. Visual inspection of the crank arms shows no cracks/damage.

Possible solutions I came up with:


Get a BB with a longer spindle (cheapest; sounds the most short-term; fit may be affected; chainline may be affected; crank arm wear and tear may bite me later).
Change the crank arms (so far, impossible to find online. I tried CRC, Wiggle, bike24. The others have very expensive shipping to my place. Haven't asked LBS yet.).
Change the chainring and cog (expensive since I'm running a White Ind ENO freewheel; crank arm wear and tear may bite me later).
Change the chainset/crankset and cog (bloody expensive, and I haven't been able to find a singlespeed square taper 52t (for 52/17) chainset online, meaning the arms and ring will have to be bought $eparately. Haven't asked LBS yet.)


Suggestions? Any input is welcome.
The first thing to do if you haven't yet is confirm that the taper bore on the drive side crank is still in good condition. Take it off, hold it up against a light, and look for any deformation. The squares formed by the two ends of the bore should be in perfect alignment. Because square taper cranks are a press fit, there is nearly no tolerance for deformation here before the crank has issues with coming loose or falling off.

What you're experiencing here is one reason, really the biggest, why I don't like to grease tapers. You get unpredictable things happening with how far the crank sinks on, and it seems like it makes it more likely to be an issue over time. Some hold the theory that the combination of greasing spindles and re-tightening the bolt can contribute to or cause the cranks failing outright over time, which is a rabbit hole of a topic, but google Jobst Brandt's writing on this if you want to understand that argument.

If the bores are still in good condition, and the chainline was right before and now it's too far in in front, then getting a new BB that puts the chainline correct again is a fine solution, barring any issues with tight clearance between the ring and the frame. Usually I don't really see anything less than around 3mm between the frame and any part of the crank as acceptable, although it's a line I'd be okay pushing on my own bikes.

The cheap and simple solution if it works is to put a 2mm or so spacer under the shoulder of the drive side bottom bracket cup. This will make the cranks asymmetrical by that much, but most people wouldn't notice. The reason this doesn't always work is that many left side cartridge BB cups have a lip on the end of the threaded section that will keep them from being able to sink into the BB shell to correctly secure the cartridge once the spacer is in place. (Usually the end of the threaded section pokes out just a little bit, with the spacer it will need to be below level of the shell face just a little bit.) Spacers such as this are a common bike shop item. Using a single 2.5mm Hollowtech 2 BB spacer is a likely thing to be able to find, or a freehub body spacer, or a cog spacer off a used cassette, or a 1.8mm 10->11 speed spacer, or a 1.8mm Shimano cassette spacer for Mavic road wheels, etc.

If the left cup does have that lip, you may be able to grind it off without weakening the cup too much.