Pulsing Brakes

Matt's 03 GT · Feb 2, 2007

Hello everyone:

I just have a quick question:

I just replaced the pads and had the rotors turned on my '03 gt. The rotors had never been off the car (the washers were still there) but were pulsing. I had them turned at a local machine shop and everything was fine for the first 300 miles.

The brakes are now pulsing again.

Is this a problem with the rotors?
Should I get them turned again?

Should I just replace them? If so, are the Ford rotors known for warping? What brand do you recommend?

Thanks,

Matt

DTNODYA · Feb 2, 2007

Your front rotors could be warped again .. though it's pretty rare to have them warp again after 300 miles. I had mine turned a few months ago and haven't had any problems with them. You may want to try jacking the front up, loosening the lugs and evenly re-tightening them.

Matt's 03 GT · Feb 2, 2007

I will check the lugs again.

The pulsing only occurs when I am slowing from high speed (about 60+).

I am also going to have the tires rotated and balanced today.

Kilgore Trout · Feb 2, 2007

Same thing happened with my GT, had the rotors turned and they were great for about a month or two and then the pulse was back. Why? Because the stock GT rotors SUCK. Get a set of cheap Brembo replacements from Tire Rack and fix the problem for good. Be sure to paint the hats of the new rotors with high temp silver so they always look good and never rust.

Matt's 03 GT · Feb 2, 2007

Kt:

I thought the Brembos were just for the Cobra's... and I'm just a lowly GT

Tire rack... Searching!

Matt's 03 GT · Feb 2, 2007

http://www.tirerack.com/brakes/brak...Mustang&autoYear=2003&autoModClar=&perfCode=P

This seems to be the best deal... About $47.00 each.

Thanks KT I will let you know the results.

Re-doing a brake job because of crappy ford parts FTL

silver04GTstang · Feb 3, 2007

on my truck i took it to merchants and they improperly tightened my lug nut and the first time i jammed the brakes it warped my rotors, soi i waited till i had autotech at school and turned them my self and torgued my lug nut in a stap pattern. the best thoing to do is take the rotors off yourself and take them and have them turned and put them back on yourself, but im a fan of not paying anyone to do the work for me. so take it to a shop you trust.

Mustang5L5 · Feb 3, 2007

Just use it as an excuse to upgrade to a 13" kit

tomustang · Feb 3, 2007

it could a number of things adding to your brakes pulsing, like steering rack or front suspension parts, don't stop at the brakes themselves

KronicRacer · Feb 3, 2007

before you go nuts going heavy on the new brakes..... read this
this
http://www.baer.com/Baer_tech/Braking_202/Pad_Bedding_Street_Light_Track.html

and
http://www.baer.com/Baer_tech/Braking_202/Rotor_Seasoning_Street_Light_Track.html

Will Smith · Feb 3, 2007

the problem you are most likely experiencing is Warped rotors. Yes you can machine rotors sometimes and there is a min machine to specs as to how thin they can be. What happens is if you get close to the machine to limit a lot of times on ford and I see it everyday at the dealership i work at is somebody cut them and the first time it rains or very soon after cut they warp again is cause they are to thin. The heat buildup and letting them sit just tears them up. Some shops don't even look at those specs and just eye ball it. Thus obviously they were cut way to thin to begin with.

COMPSYSTEMS · Feb 4, 2007

What about the rear.

Sometimes you have to look at the not so obvious things to find the answer. What about the rear brakes? I had a problem on a car where the slide pins were covered in break dust and didnt let the caliper move like it should. This was putting all the load of the breaking force on the front rotors causing them to warp and be glazed from the heat. SAFELY...Try slowly pulling up on the parking brake while driving slowly down the street to see if it is smooth drag or if it has a shimmy.

CobraRed_96_GT · Feb 4, 2007

my discs seem to be quality, I turned em 2 years ago my self at the auto shop in school and have yet to show any problems

LaserRed01GT · Feb 5, 2007

Matt's 03 GT said:
Hello everyone:

I just have a quick question:

I just replaced the pads and had the rotors turned on my '03 gt. The rotors had never been off the car (the washers were still there) but were pulsing. I had them turned at a local machine shop and everything was fine for the first 300 miles.

The brakes are now pulsing again.

Is this a problem with the rotors?
Should I get them turned again?

Should I just replace them? If so, are the Ford rotors known for warping? What brand do you recommend?

Thanks,

Matt

One of the most common causes of warped rotors are lug nuts that have been tightened to tight or the minimum thickness of the rotor has been exceeded.

Our lug nuts are only supposed to be torque'd to 95 lb-ft. So many shops still use a impact wrench on the lug nuts and a lot of those impact wrenches they are using can generate well over 400 ft-lb, big no no. It's very imporant you make sure the shops that you go to or you yourself use a torque wrench on the lug nuts.

Brake disc Minimum thickness Front 1.1 in
Brake disc Maximum Runout 0.002 in
Brake disc Maximum thickness Variation 0.00035 in
Brake disc thickness Rear 0.55 in
Brake Disc allowable runout on vehicle 0.004 in
Brake Disc Maximum thickness Variation 0.0004 in

Normally they will cut around .005-.010" off the rotor, .015" if they are bad. But, a lot of times these shops won't really pay attention how accurate they set up the brake lathe. Where did you have them turned?

Matt's 03 GT · Feb 5, 2007

This was the first time the rotors were turned so I doubt they art too thin.

I had them turned at Pep Boys. I did the brake job itself, and just took the rotors to them off of the car.

The pulsing did go away for about 300 miles so I am confident that the pulsing is from the front brakes.

I torqued the lugs myself in a cross pattern.

I am going to order the Brembo brakes today and I will let you know what happens.

Thanks all for your help,

Matt

2002GreyGT · Feb 5, 2007

I warped a few set of cheap rotors, blanks, drilled / slotted, before I finally broke down and got some blank cobra stock brembo's ( I have cobra brakes up front). Get the zinc plated if you can find them, that way you don't have to paint them to keep them from rusting and looking like crap.

Make sure you are also not over tightening them, what did you torque then too?

~K

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