Murdered04GT

I just installed ford racing slotted and cross drilled rotors and hawk pads oon my 04 Gt, when I apply the brakes i get a vibration/shimmy in the front end and the steering wheel shimmies back and forth from right to left. the harder i press the pedal the worse it is and its worse at higher speeds?!? Does anyone have any idea what could cause this? or how to fix it!?!?

GINGERBREDMAN00

As far as I know that's usually the symptom's from warped rotors..
did they seem to be loose or wiggle around when you put them on? maybe they require larger diameter lugs? I'm just thinking out loud, but it's just a thought of what it could be..or maybe worn suspension parts that where close to being wore out and can't take the added stress / load you just put on them?

Murdered04GT

I Just can't imagine the rotors would be warped. Brand new qa1 struts and coilover kit on a few days before and had no problems with stock brakes. Car had inner and outer tie rods a few months ago and car only has 34k miles on it. Problem started right after new rotors and pads installed

petrock

did you break the rotors in properly? The first couple hundred miles are critical. If you do a bunch of hard braking at high speed to a (almost) complete stop after initial install, you can easily warp new rotors.

Are you sure that everything was installed correctly and tightly? The rotors fit properly on the hub etc? Did any grease, oil or brake fluid get on the rotors or pads before, during or after install? All these could cause the problems you describe.

I would start by taking it all apart and reinstalling. Paying close attention to using the proper torque on the bolts and that everything fits snuggly/properly. If the rotor is loose it could cause this problem.

67mustang302

False. Most proper pad/rotor bedding procedures require that you slowly brake at low speeds and work your way up to high speeds and hard stops to almost a complete stop. What DOES cause a problem with that is after you finish the high speed bedding cycle, coming to a stop and leaving the brakes applied....it causes material to tear off the pad and adhere to the rotor causing a high spot. It effectively creates rotor runout which can result in the vibration. If the rotors warp after doing high speed high temp braking within the first 50ft of driving, then they're complete crap.

Did the rotors vibrate from the instant you used them? Or did it start after time? What bedding procedure did you use? Do the rotors appear to have any teeny-tiny hairline cracks in them?

petrock

Don't be so quick to judgement... Especially on a subject that isn't as cut and dry as "true" & "false".

Doing a bunch of high speed hard braking produces a ton of heat. If you don't let the rotors cool down enough in between each high speed braking run the rotor will just retain all that heat to the point that they can even start to glow. This can weaken the rotor and it can warp and even crack as a result. Warping and cracking is fairly common in cross-drilled rotors due to the holes weakening the rotors. This forum is littered with threads about drilled rotors prematurely warping/cracking/failing.

67mustang302

I'm well aware of that. That's why rotor bedding procedures require you start with low speed light braking and slowly work your way up to high speed and hard braking. It slowly builds heat under pressure in the rotor to finish the rotor treating process that can't be done cost effectively during manufacturing. The Wilwood stuff I buy(and others) can also be purchased pre-bedded from the factory, but it's anywhere from 80-120% more expensive that way.

You have to bed rotors/pads in with hard high temperature braking at some point to completely finish the bedding cycle. If not, the rotors could fail because they haven't been cycled and settled for high temp use. But you can't just start out with hard braking either. That's why there are bedding procedures, and not following them will damage rotors. Proper bedding should include high temp hard braking, and should also be complete within the first several miles.

And yes, cross drilled rotors crack all the time because they're mostly for looks and not performance. Partly because it removes material that would otherwise be there to absorb and conduct heat.

.boB

I agree with 67mustang. every break in procedure I'v ever used or seen starts with low speed braking and then moves up to faster and harder braking.

Read this: http://www.stoptech.com/tech_info/wp...rakedisk.shtml