Modulating brakes...

[Jonny Zed]

My brakes modulate when I stop. It's especially noticable when I'm pointed downhill. At first I thought it was the rear antilock. I've had the front right tire off (stupid spark plug change!) and that disk was fine. I haven't had the rear off, but I don't have any of the typical grinding / squealing noises associated with worn pads. Any thoughts?

 

[JDraper]

Could be warped rotors. They are difficult to spot visually, but the usual sign is a pulsing brake pedal and vehicle shaking. Take it to a brake repair shop, have them check it out. Take it in, tell 'em what you're feeling, and have them give you an estimate on the repairs. You don't have to leave it with them, but the estimate should (if the shop is reputable) tell you what is wrong. Most chain shops (midas, Monroe, etc) will give you a free estimate.

 

[mrboyle]

Dealing with brakes on a daily basis I see more warpped rotors than I care to remember. The warpage is due to one unavoidable fact: metal, when heated and cooled expands and contracts at different rates. This causes the rotors to chang shape (microscoipc changes) every time you use the brakes. Over time the rotor will distort enough that when you apply the pedal the distortion will actually force the piston of the caliper to fluctuate in and out, causing the pulsating feling you are experiencing. The only cure is to either machine the surface of the rotors making them parallel again, or replacing them with new ones. There is one major downfall to the machining process though. In order to create a true surface it is necessary to remove material from the rotor. In dooing so the rotor becomes thinner and a thinner rotor will warp faster than a thick one. Its up to you when it comes to making the call, but I seriously recomend replacing the rotors as opposed to replacing them.

 

[Jonny Zed]

Thanks for the info! I think a rotor change is in order...