Pulsating Pedal
Thread Starter
Racer
Joined: Feb 2002
Posts: 378
Likes: 19
Pulsating Pedal
Seem to have a pulsating pedal, that I'm having a problem trying to figure out. About a year or so ago had 3 leaking calipers replaced and everything was okay at the time that work was done. The following year is when this pulsating issue started.
Looking at all the rotors, nothing seems out of the ordinary, there no scoring on the rotors or chewed up pads or any sort of noticeable distress. Checking the run-out up front, it's at .006 and .007.
Suppose I'll check the run-out out back, but I'm looking for big time run-out. IMO, the run-out that I seeing up front does not point to it being the problem.
Has anyone come across anything like this? the pulsating is very noticable.
Thanks for any response.
Looking at all the rotors, nothing seems out of the ordinary, there no scoring on the rotors or chewed up pads or any sort of noticeable distress. Checking the run-out up front, it's at .006 and .007.
Suppose I'll check the run-out out back, but I'm looking for big time run-out. IMO, the run-out that I seeing up front does not point to it being the problem.
Has anyone come across anything like this? the pulsating is very noticable.
Thanks for any response.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
This is my problem. It only happens to the left front rotor. Look at it real close and you can see a slight coating on part of the rotor. Some 100grit sand paper takes it right off and it's OK for a while. I'm thinking I need to get a better set of pads.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If the rotor has NO runout, the pads will continue to 'smear' on the rotor...even when they are not being applied. You need to have some rotor runout (.002-003") so that the pads will be "pushed" away when they are released from the rotor and not continually rub on them. If this is your case, the pulsations may be from the inconsistent surface condition being created on the rotor with little or no runout (a pad 'grabbing' condition).
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Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
Originally Posted by Goody
Pulsating brakes are typically caused by brake pad material built up on the rotors.
A simple fix is to do a really hard stop from highway speed and then DO NOT SIT with the brakes on until they have cooled (do your stop and then quickly drive on). The pad transfer happens when the rotors are hot and you sit with the brakes on.
Last edited by Rich's'78; Sep 21, 2009 at 01:01 PM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
you may also have a low spot in one of the rotors. did you measure the run out in several places on the rotor or just one?
this is exactly what i had....
this is exactly what i had....
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Sand the rotor surfaces with 100 grit paper and see if it makes any difference.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I have found on 4 piston calipers rotor runout doesn't effect the pedal hardly at all but a rotor with parallelism issues will.
If a rotor is parallel but has runout the fluid push is contained inside the caliper with the pistons on the opposite side compensating for the other side and the fluid in the line going to the master never moves.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
As I said before, my pedal pulses for a while and then it seems fine for a while. Apparantly the pad material is transferring to the rotor and occasionally it gets wiped clean. I'm using the replacement organic pads. Would a semi-metalic pad eliminate the build up of the pad material?
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
Drive vehicle with light touch on the steering wheel; and apply the brakes. A front wheel pulsing rotor/caliper will transmit pulse through the steering. Organic pads give the least amount of brake pad failures. 
