Magazine Today
The driver in the left lane suddenly relishes missing his exit, so he cuts in front of you. You mas h the brake pedal, and it vibrates like a running chain saw as the antilock braking system (ABS) keeps you out of a skid. Thankfully, you don’t rear-end the jerk’s car, as he also brakes to slow down.
Hesoheoff ramp and go ne, so you don’t get the chance to pull alongside and express your feelings with universal sign language. But that’s probably a good thing.
While it can be reassuring to feel that ABS-connected brake pedal pulsating beneath your firm pa ntedfoot, it’s reasonable to suspect a problem if you ge the same pedal pulsation with a light to medium braking application.
ABSesqueIf the brake feels like the ABS is cycling, but you know that it’s not, check the individual axle trigger wheel ls in front (and o n some ca rs a also in back ) and the adjacent wheel l speed sensors. If you see a damaged wiring connector, bent sensor mounting bracket, or stone-damaged trigger wheel, that’s a likely cause.
But on almost all cars, the cause norma ll y is something in the service brake itself, and the primary problems are ones you usually can check and correct yourself. the titles of all bulletins for your specific make and model car.
Lug Nut Torque The No.1 cause of brake pedal pulse-on is uneven lug nut torque. The usual reason is that some mechanic overtightened the wheel lug nuts with an impact wrench, distorting the brake disc. How do you know if your torque There’s no proper alternative to torquing the lug nuts in a crisscross pattern, by stages and with a torque Oil the threads and chamber with engine oil?
wrench h is acc urate Well if it’s by a name-brand tool company and hasn’t been thrown around o r ha d a cement block dropped on it, it should be okay.
Check the torque a t each wheel and compare the read ing wit h ma nu fac to rider’s spec ifications. If there’s a difference o f 20% between a n y two lu g nuts, that’s too.
Last word
Try loosening an ll the lug nuts, and clear night-e stud threads Before you check even the most likely pro bl ems on a late model, make absolutely sure there isn’t a factory problem with a specific fix. Sure, this is low on the ” likely” list, but it’s a lot easier to look for a bulletin than to pull wheels, etc. One possibility: the AIIDa ta Web site, a leading supplier of information for professional mechanics.
