brake rotor question
Thread Starter
Instructor
Joined: May 2005
Posts: 247
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From: Ramona CA
brake rotor question
I recently replaced the front rotors and pads with brand new Napa parts. I have a pulsating feeling under light braking. Typically if the front rotors are warped, I would expect a rotor shake in the steering wheel which is not occuring. Neither the front or rear rotors appear to have hot spots on them. I would normally return the rotors to Napa but I can't find my reciept. What I want to know is if the rears could possibly be the culprit. I wouldn't expect the rears to be doing much under light braking but that's when the feeling is most felt. I'll probably just turn all the rotors but I would like to know if it could just be the rears because I need to replace them and I don't want to mess with turning the fronts if they don't need it. 
Thread Starter
Instructor
Joined: May 2005
Posts: 247
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From: Ramona CA
yes and yes for the front. On a side note, I am pulling the rears to adjust the parking brake shoes. I just noticed that the rear lugs were way way way tight. My impact gun wouldn't take them off and I had to use my torque wrench to get them loose. Perhaps the rears are screwed because the last person that touched the rears (not me) overtightened the lug nuts.???
Race Director
Joined: Jul 2004
Posts: 16,795
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From: Lake Havasu City, AZ
When I last replaced my front rotors and pads, I had a similar pulsating that went away after seasoning and bedding...
New rotors should be driven for 4-5 days of normal driving on the old pads. Then they should be seasoned by 5-6 stops from 50 or 60 to zero, then driven long enough to cool.
The new pads should then be put on and after a few regualr driving days they should be bedded in to the new rotors. Again this is through a series of 60-0 stops followed by a cooling period.
for articles on warped rotors and proper seasoning and bedding in techniques... see this link http://www.stoptech.com/tech_info/te...e_papers.shtml
New rotors should be driven for 4-5 days of normal driving on the old pads. Then they should be seasoned by 5-6 stops from 50 or 60 to zero, then driven long enough to cool.
The new pads should then be put on and after a few regualr driving days they should be bedded in to the new rotors. Again this is through a series of 60-0 stops followed by a cooling period.
for articles on warped rotors and proper seasoning and bedding in techniques... see this link http://www.stoptech.com/tech_info/te...e_papers.shtml
Melting Slicks
Joined: Jan 2003
Posts: 3,251
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On a similar vein. If the pulse does not worsen with heavy braking as it should with warped rotors, then I would say the rotors are fine. The rear brakes are really wimpy and don't contribute much to the real braking unless you changed out the proportioning valve spring.
Look at the Ball joints and tie rods. A bad ball joint will pulse with light braking and get better with firm braking. Bad tie rods will be loose if you grab the wheel from left to right and ball joint will be loose when grabbed at the top and bottom. It's best if you can lift the front end to unload the joints.
Look at the Ball joints and tie rods. A bad ball joint will pulse with light braking and get better with firm braking. Bad tie rods will be loose if you grab the wheel from left to right and ball joint will be loose when grabbed at the top and bottom. It's best if you can lift the front end to unload the joints.
Last edited by IM QUIKR; May 18, 2006 at 09:22 PM.
Thread Starter
Instructor
Joined: May 2005
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From: Ramona CA
As an update, I did some better breaking in of the pads and it seemed to improve. I'll be driving it to work tomorrow so I'll get a better feel to see if that truly was the problem. The hubs have no rust on them and I'll check the front end parts too. The car has 60K miles, do the front end parts wear out that fast? The steering seems tight to me but it does have some strange attitude when driving through uneven pavement. You really need to hold on to the steering wheel when there's a bump in the road because it will follow. I just assumed that had something to do with the A. worn out tires, and B. the aggressive alignment that the Z51 suspension has. By the way, I spun her out the other day because my traction control was disabled because of a bad female connector on the left front, hence the TCL light and ABS light, and the bald tires, and me giving it too much throttle. Time for tires for sure, but I did fix the bad connector today.
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Team Owner
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From: SoCal
Originally Posted by skelly1
As an update, I did some better breaking in of the pads and it seemed to improve. I'll be driving it to work tomorrow so I'll get a better feel to see if that truly was the problem.
DH
Premium Supporting Vendor
Joined: Aug 2001
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From: King George VA
That's a good link posted by rws.1 above. If you didn't catch it, there is a good article on that page about the myth of warped rotors:
http://www.stoptech.com/tech_info/wp...rakedisk.shtml
I go through lots of pads and rotors on the track and I had a similar problem to yours once. As mentioned in the above article, in my case it was uneven pad material buildup vice a warped rotor. After a proper rebedding they were fine. Since then, I've been much more careful to follow the bedding instructions that come with the new pads.
http://www.stoptech.com/tech_info/wp...rakedisk.shtml
I go through lots of pads and rotors on the track and I had a similar problem to yours once. As mentioned in the above article, in my case it was uneven pad material buildup vice a warped rotor. After a proper rebedding they were fine. Since then, I've been much more careful to follow the bedding instructions that come with the new pads.
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Instructor
Joined: Aug 2004
Posts: 168
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From: Hooksett NH
I would also check to see if there is any play in your Hub Assemblies(Wheel Bearings).
I had to have one replaced, under warranty, on my 2004.
This might also be what you are feeling on those bad roads.
Good Luck
I had to have one replaced, under warranty, on my 2004.
This might also be what you are feeling on those bad roads.
Good Luck
Race Director
Joined: Dec 2000
Posts: 19,304
Likes: 85
From: San Diego CA
As long as you have OEM-style rotors, you will continue to have uneven deposit issues, I'm afraid. This is very common throughout the automotive industry and it certainly has something to do with the brake pad material. Slotted rotors are, IMO, the best defense against this problem. Not only do they run cooler than plain rotors, but they also keep the pads from glazing and from depositing those pedal pulsation-causing jitters that irritate us all.
Racer
Joined: Jul 2000
Posts: 485
Likes: 2
From: Charlotte NC
skelly1,
It very well could be your rear rotors. They are prone to uneven pad deposits, just like the fronts are.
Do you happen to have any race pads on hand? If so, you may want to try something like this: http://www.stoptech.com/tech_info/wp_padremoval.shtml
You would be shocked at how well a set of Hawk Blue pads can fix a "warped rotor." I had a problem after a track day a while back with a pulsation that developed with some race pads at the track. I threw some Hawk Blues in and it took about 5 laps around the parking lot to solve the problem. I always keep a set on hand when I go to the track for a quick fix if I or one of my customers needs it.
Dave68 was getting at the problem in his post...I'll elaborate a bit. The issue is running your pads above or near their Max Operating Temperature. When you do so, pads start to break down...they'll come off in chunks, and smear onto your rotor face. It happens most often when people try to take a street pad on a racetrack. They just aren't designed for that type of heat, and they don't respond well at all.
It very well could be your rear rotors. They are prone to uneven pad deposits, just like the fronts are.
Do you happen to have any race pads on hand? If so, you may want to try something like this: http://www.stoptech.com/tech_info/wp_padremoval.shtml
You would be shocked at how well a set of Hawk Blue pads can fix a "warped rotor." I had a problem after a track day a while back with a pulsation that developed with some race pads at the track. I threw some Hawk Blues in and it took about 5 laps around the parking lot to solve the problem. I always keep a set on hand when I go to the track for a quick fix if I or one of my customers needs it.
Dave68 was getting at the problem in his post...I'll elaborate a bit. The issue is running your pads above or near their Max Operating Temperature. When you do so, pads start to break down...they'll come off in chunks, and smear onto your rotor face. It happens most often when people try to take a street pad on a racetrack. They just aren't designed for that type of heat, and they don't respond well at all.
Burning Brakes
Joined: Aug 2000
Posts: 1,132
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From: Morganton, NC, USA
Everyone be careful when bedding pads to rotors so that you do not come to a complete stop with your foot on the brake pedal when the pads and rotors are hot. This will deposit a relatively thick patch of pad material on the rotor, replicating the shape of the pad. Guarranteed high spot on the rotor and a pulsing brake pedal.