For a 99 Civic LX 4-door sedan, can someone please post the specs for -- -- rotor thickness -- brake pad thickness -- drum shoe thickness, if it uses drums in the rear I have a friend with this car who gets vibrations in the steering wheel when she brakes. Anything else you'd check right now?
Other than rotor runout due to actual warpage... http://www.babcox.com/editorial/bf/bf100326.htm Make certain that 1) All glaze deposits have been sanded off the rotor 2) All rust has been sanded off the hub and rear of the rotor's "top hat". http://www.tegger.com/hondafaq/misc/rotor_off.jpg http://www.tegger.com/hondafaq/misc/glaze.jpg http://www.tegger.com/hondafaq/misc/glaze-off.jpg Glaze makes "hard spots" that differ in friction properties from the unglazed portions of the disc. Glaze is simply pad material that has embedded itself into the surface texture of the disc. The pads will regularly grab more or less depending on what they are travelling on, and this will be felt as vibration. A wire wheel or lots of work with 50-grit emery cloth will fix that. If there is any sort of rust, or any particles on the flange or the back of the rotor, the rotor will sit crooked on the hub, and runout will be excessive, and this will be felt as vibration. Once you are past that, then you need to read the Babcox article **very** carefully. Don't let anyone tell you overtorqued wheel nuts have caused this. On Hondas this is simply *not* true unless there are other factors at play, such as flange rust. Another factor is tires. When you brake, the front tires are pressed into the pavement more firmly than if you are just cruising. If the tires are cupped or otherwise unevenly worn, this can show up most when they are pressed harder (or lighter!) into the pavement. Of course, odd tire wear leads us directly to the possibility of suspension wear... Check the brakes first.
Thanks, Tegger. Update: My friend's car was due for an oil change and so she decided to let the dealer do it today and also check out the brakes. She said the rotors just needed an "adjustment." Not sure what that means, or whether she had the wording right (though I mentioned rotor warping to her as a possibility before all this, so she was attuned to something possibly being wrong with them) but I gather it may simply have consisted of cleaning off the rotors.
the babcox article /does/ mention torque as a factor in causing runout - it's the 4th point after the first paragraph on that subject. all you say is great advice, but i believe the babcox article is deficient in that is does not acknowledge the important fact that in a runout situation, [ie. where the disk is wavering fron side to side] there is a momentum effect. a single piston caliper has a significant mass & therefore momentum differential between the piston side & the caliper side. the piston is light & can follow the disk runout much more easily than the heavier caliper, no matter how easily that caliper may be able to slide. for low speed runout, the effect will be small or indeed negligable, but at higher speed, the caliper will always be playing "catch up" to the piston because of its higher mass and will therefore create a pressure differential in the hydraulics, which will in turn be felt at the pedal. in a fixed caliper, with opposing pistons, provided both pistons are equally free to float, the there will be no pulsing under runout because the momentum of both pistons is the same. maybe carryng this assumption from fixed calipers to single piston calipers is the cause of this omission.
Since the caliper cannot move more quickly than the piston, the piston is eventually kicked back into the caliper as the rotor strikes the pad on the piston. The caliper/pad assembly therefore eventually floats free of the rotor anyway, same as the fixed caliper type. If the caliper or pads are frozen in place and cannot slide correctly, then the effects are a bit different.
right, momentum. yes, but there's a time delay, and that's where the hydraulics experience a pressure pulse. for single piston, if the caliper's not free to slide, the effects are more pronounced & happen at lower speeds, but the net effect is the same, the piston being forced in & out of the caliper causing the pulsing.
I see your point. I suppose Babcox could have emphasized that more, but then how many other things could they have emphasized? Regardless of that, the Babcox article deals with the causes of pulsation complaints, not specifically with the effects of those causes. The main premise of the Babcox article (as I gather it) is that it is too common for pulsation complaints to be incorrectly identified as "warped rotors", and for the "warpage" to be wrongly identifed as actual distortion of the friction faces. They are saying that you need to investigate several other significant causes of pulsation before pinning the blame on distorted friction surfaces.
yep. i've seen disks be worse after being skimmed than they were before, so the babcox article is great in that it encourages people to not assume it's the disk every time. and that's why it's a good article. they just need to update the single piston caliper theory a bit, that's all.