I've been getting pretty serious brake fade and even "shimmy's" when stopping from 1xxmph + pretty hard. It feels like the brakes are going to explode. After they cool down... it all good. No shimmy... but if I go back to 100 mph...and try to slow down to 40 by the time I get to 70.. they are fading and shimmying like crazy. I don't think they are warped because this only happens on high speed runs... then having to break hard.... everyday cruising they are fine.

The rotors and pads are new since this spring. The tech did not use a torque wrench for the rotor bolts(im not sure if this would be the cause)...could being over or under tightened have this kind of affect... also I am getting some pretty crazy hot spots. I did "bed" them in.....but only from 60-10 mph... so i couldn't really feel the shimmy.
They are Brembo Gran Turismo with the 8 piston calipers.

thanks.

 

The tech didn't use a torque wrench on the rotor bolts???!?!? They HAVE to be torqued properly! That is a major safety hazard, I can't believe any reputable mechanic would not torque a fastener as critical as those.

Also, are you using the Jurid pads on your system? There are some other compounds available from Brembo that are much better for fade resistance. The Ferodo FM1000 material for instance.

The shimmy you are experiencing is in the steering wheel I assume? If so, then this is what is called judder, and the "hot spots" are actually areas where the transfer layer of pad material is not even on the disc. This uneven transfer layer is what is causing the judder.

One of the precautions with bedding in the Brembo upgrades is that you have to take care during the initial stops to take the plating off the disc with very gentle stops to prevent generating very much heat and forcing the plating material into the slight pores in the disc or embedding it in the brake pad material. Once the disc surfaces are free of the plating, you can commence with a typical bedding procedure.

 

Thanks... I had a strong feeling that the bolts not being evely torqued was the main issue.

Thanks. they are going to be reinstalled tomorrow.

 

If the fasteners weren't torqued in the first place, all of the bolts and nuts should be replaced, as they could and probably were subjected to stresses that they were not meant to. Also, the bolts have a high temperature 2-part epoxy thread lock compound pre-applied to the threads that is activated on assembly. If the nuts are simply torqued now, first the epoxy thread lock will give an inaccurate impression of the installation torque as they are now effectively "glued" in place. Second if the nuts do turn, then that will be breaking the thread lock and will render it non-existant.

My other concern is that even once this work is completed properly, with the discs in their present condition the judder will most likely not subside as the uneven transfer layer will still be present.

 

There is a specific way of tightening the bolts that hold the rotors to the hat-
Because of the brembo design one will seem loose in comparison to the other.

 

If you have this judder when the discs are hot, but not
when they're cold, this seems to be the disc warping
because of thermal distortion, and thankfully returning
to shape when they cool down. The first thing I would
try is to add the (relatively cheap) GT3-cup air scoops
to get more air to the discs. If you can keep them cool
you may get rid of the problem. Even stock brakes should
have zero problem with what you're trying. Do you still
even have the small stock scoops on your control arms?
Joe

 

Thanks for the reply Joe....
Actually its on my M5. I know the guys here are very good with race applications and expierienced. So Thank you all for the replies.

New hardware and more aggresive pads are now on there way!

 

Fabryce, the hardware system on these discs is different than the type you are referring to. On the 380x34mm discs like the ones he's got all of the fastener locations are the same.

 

I had the same problem, changed pads and brake fluid and all gone!

 

philly I vote for poor pad bed in procedure as your cause of judder. and those huge brakes wouldnt fade after one hard brake. are you just talking about on the street? I cant believe you would get the kind of track level fading problem.
Oh yeah, and Joe is always right also!!
those are great brakes hope all works out

 

They're definately poorly bedded-in, the famous Stoptech website tells you how to recover the rotors. I'd be afraid, very afraid of a tech who doesn't use a torque wrench to bolt on a rotor.

 

I found out that I should be using a more aggressive pad... so new pads and hardware have been ordered. The rotors seem to be allright(not warped)... just a nice 2 inch thick blue line going around them. So.. we shall see.

Thanks everyone.