rec autos frequently asked questions archive name rec autos part this article is one of a pair of articles containing commonly asked automotive questions the other article contains questions of general consumer interest and is broken out to facilitate crossposting to misc consumers rpw last change february ct now permits radar detector usage new tire traction q a rpw commonly asked questions radar questions q where are radar detectors illegal a in the us currently virgina and the district of columbia prohibit all usage of radar detectors new york prohibits their use in large trucks in canada they are illegal in manitoba ontario quebec newfoundland and pei prince edward island they are apparently are illegal through most if not all of europe legislation which would make them illegal is pending in many other jurisdictions chances of such legislation passing varies a great deal q where are radar detector detectors used do they really work a usage is spreading rapidly initially they were used only in canada but now they are appearing in new york and virginia it is unsafe to assume that they are not in use in connecticut and d c they work by detecting a certain frequency radiated by many currently available super het radar detectors some brands of detector radiate more strongly than others and are thus more likely to be spotted new radar detectors are becoming available which may not be detected by the current generation of detector detectors note that a detector may only be spotted by one of these devices if it is turned on q what is vascar is it some kind of radar a vascar is nothing more than a fancy stopwatch and time speed distance computer it depends on the operator pressing buttons as the target vehicle passes landmarks no radar signals are emitted by a vascar system q what is ka band radar where is it used should a radar detector be able to handle it a ka band has recently been made available by the fcc for use in the us in so called photo radar installations in these installations a low powered beam is aimed across the road at a degree angle to the direction of traffic and a picture is taken of vehicles which the radar unit determines to have been in violation of the speed limit tickets are mailed to the owner of the vehicle because of the low power and the degree angle many people believe that a radar detector cannot give reasonable warning of a ka band radar unit although some manufacturers of radar detectors have added such capability anyway the number of locales where photo radar is in use is limited and some question the legality of such units best advice learn what photo radar units look like and keep track of where they are used or else don t speed q do radar jammers work are they legal a quick answer no and not in the usa detailed answer cheap radar jammers do not work well at all jammers that work are expensive and usually the property of the military jammers are a major violation of the regulations of the federal communications commission of the usa driving technique and vehicle dynamics questions q what are understeer and oversteer a understeer and oversteer are terms describing the behaviour of a car while cornering near the limit limit of adhesion that is most drivers do not normally drive hard enough for these terms to be descriptive of the situations they encounter simply put they tell whether the car wants to go straight in a corner steer less or understeer or it wants to turn more in a corner oversteer understeer is commonly designed into most production cars so that untrained drivers inadvertantly traveling too fast won t get into trouble understeer may also be induced by using too much throttle in a corner oversteer is designed into some more performance oriented cars it may be induced by lifting on the throttle trailing throttle oversteer or tto in extreme cases lifting on the throttle may induce so much oversteer that the car reacts by fishtailing or spinning some technical details in a corner at speed the tires on the car will develop what are called slip angles the slip angle is the angular difference between the direction that the car is traveling and the direction that the steering wheel is directing the car to travel in understeer the front wheels have a greater slip angle than the rear wheels in oversteer the rear wheels have a greater slip angle than the front wheels q what is a rev matched downshift a when downshifting the engine must be rotating faster in the lower gear than it was in the higher gear however during a downshift normally you declutch and lift your foot from the throttle so the revs drop rather than increase in rev matched downshift you blip the throttle before re engaging the clutch so that the engine will already be up to the new speed this results in a much smoother and faster downshift q what does heel and toe mean a heel and toe is a technique used to do a rev matched downshift while braking this is normally challenging because you need the right foot for both the brake and throttle it is called heel and toe because you use one end of the foot on the brake and the other on the throttle to match revs for the downshift in many modern cars this is a misnomer often you must use the ball of the foot on the brake and the right side on the throttle note that some race car drivers will skip the clutch and just use the left foot on the brake and the right foot on the throttle accomplishing the same thing q what is double clutch downshifting a while your right foot is doing the above your left foot can do one of three things nothing declutch once or declutch twice the reason for declutching twice is to match the speeds of the two shafts in the transmission to the speed of the engine this is usually coupled with rev matching so that while the engine is in neutral and the clutch engaged the throttle is blipped and both shafts of the transmission speed up the procedure is as follows declutch move gearshift lever to neutral engage clutch match revs declutch move gearshift lever to next lower gear engage clutch this sounds like a lot of work but with practice it becomes natural the problem that double clutching solves is normally the function of the synchronizers within the gearbox in transmissions without synchros or with very worn synchros double clutching makes it much easier to shift basically if you double clutch well you are not using the synchros at all this is generally unnecessary on street cars with synchros in good condition q what do the numbers for acceleration from mile skidpad and slalom times in the auto magazines really mean may they be compared a in short not as much as the magazines want you to believe and almost never in more detail the acceleration numbers mph and mile times in the us may be vaguely compared as long as they all come from the same source testing procedures vary so much from magazine to magazine that comparing a road track number to a car driver number is quite pointless keep in mind too that the same variation applies from driver to driver on the street the driver is a major often the major part of the equation skidpads vary and even if they didn t skidpad figures are really only tests of the stickiness of the stock tires they change radically when tire compounds change do not make any assumptions about the comparative handling of say two sports sedans based on skidpad numbers this is not to suggest that skidpads are without value however skidpads are an excellent educational tool at driving schools they are simply of limited value in the comparison of anything except tires slalom times are slightly more useful they test some small parts of the automobile s transient response however they are also heavily influenced by the stock rubber on the car and they do not test many corners of the car s envelope they do not tell you all you need to know before making a buying decision for example they don t tell you what the rear end of the car will do on a road which suddenly goes off camber when a car has an adjustable suspension these tests are usually done in the sport setting which may be quite unsuitable for daily driving the list of caveats could go on for page after page q my buddy claims that wide tires don t make any difference according to his freshman physics textbook and that you can t ever accelerate or corner at more than g does he know what he s talking about a in short he hasn t got a clue in more detail the equations for friction used in freshman physics textbooks presume that the surfaces are smooth dry and non deformable none of which properly apply to tire traction except in the case of a stone cold tire on dry pavement which is far below its proper operating temperature pavement is never smooth it is always irregular to a greater or lesser extent tires which are not really dry and solid as rubber is a substance which in its natural form is liquid and which has only been coerced into a semblance of solidity by chemical magic deform to match the surface of the pavement which a vehicle is traveling over in a tire at operating temperature grip is actually generated by shear stresses inside the deformed rubber and not by anything even remotely resembling friction in the freshman physics sense of the term the colder a tire is relative to its operating temperature the closer its behaviour will be to the traditional concept of friction if much hotter than the its proper operating temperature the more likely the possibility of some part of the tire actually reverting to liquid which is mostly like to happen deep in the tread causing characteristic blisters and chunking this latter though is almost completely unlikely to happen in normal street driving so unless you re a competition driver or do a lot of high speed track driving don t worry about it because tire traction is completely out of the domain of simple friction it does not obey the freshman physics equation at all thus dragsters accelerate at more than g and race cars corner and brake at more than g because simple friction does not apply it is actually possible for different sized contact patches to generate differing amounts of grip an actual analysis of tire behavior would require techniques such as finite element analysis due to the complexity of the mechanism misc questions q what does name or acronym stand for a here is a list of some of the names which are commonly asked about be careful in soliciting the meanings of other names as misinformation abounds on the net in particular never ask in rec humor if you want a useful result saab svenska aeroplan a b or the swedish airplane corporation alfa societa anonima lombarda fabbrica automobili or the lombardy automobile manufacturing company fiat fabbrica italiana di automobili torino or the italian automobile manufacturers of turin bmw bayerische motoren werke or bavarian motor works mg morris garage q does vw own porsche a no porsche is a publicly held company controlled by the porsche and piech families porsche has extensive business dealings with vw audi which causes some confusion since currently porsche is in some financial difficulty there is a possibility that mercedes or vw may be interested in purchasing the company in the near future but this is only speculation at this time richard welty welty cabot balltown cma com nothing good has ever been reported about the full rotation of a race car about either its pitch or roll axis carroll smith
