Newbie Brake question...

[Arshad]

During normal city/highway driving, my brakes feel great. However, if I come to a stop from a high rate of speed, eg. over 180km/h, there is some shudder at the end. This occurs if I just keep the brakes depressed the entire time with moderate pressure. If I hit the brakes hard for a few seconds, then let off, then hit again, then let off etc then I don't see this problem.

I was under the impression that warping on the rotors would result in this type of shudder, but then shouldn't it happen all the time (ie. when braking hard)?

Last year I had my front rotors replaced, and my rear rotors machined. I also had my rear pads replaced. Does this sound like I simply might need to replace my front pads?

 

[hlweyl]

Sounds like slightly warped rotors to me. Make sure when you are having your car serviced that they properly torque the lug nuts(with a torque wrench) to 80 ft lb and NOT use air tools to reinstall lugs which can result in warpage of the rotors.

good luck

 

[jgtcnsx]

ya sounds like rotors and pads have them replaced on front and rear may be even an upgraded pad and rotor just for the little extra

 

[Arshad]

Normally I'd assume it was the front rotors, but I'm surprised since I had a new pair of front rotors installed maybe about 12000miles ago -- I didn't expect it to go so fast. I'll have them look at the rotors and pads tomorrow when I take my car in to the dealership.

I was considering getting the comptech OEM-sized cross-drilled and R4S pads, but then I read up on cross-drilled and all of a sudden it doesn't sound so appealing unless I also go much bigger. I'd love to get a BBK, but my wallet is going to be considerably lighter tomorrow after I get the CTSC put in. Maybe next year

 

[comquat1]

Here's what I had going on with my brake setup that I just put on brand new less than two weeks ago. I got new rotors and pads and noticed my fronts were shuddering under hard braking from 70mph-50mph then would stop. I figured it was a bad bed in procedure and was going to rebed in the pads after I went to a track event today. Well, at this event, I had horrible shudding going on all day, it would not go away no matter how hot the brakes got. I talked to John Vasos and he told me to take the rotors to my dealer and have them cut 2 thousanths(sp?) off of each rotor and reinstall them. He said even brand new rotors can be off by a very little bit and that would cause your shuddering. So that's where I'm at, I'll be taking my rotors off soon to get them cut, hopefully that will solve my prob and it may help yours too. FYI I have no problems with city driving, but I don't hammer on my brakes driving in the city as I did on the track today.

 

[Bram]

Arshad, So you are getting a CTSC for your car...cool

Are you getting it from Woodbine ?

Bram

 

[Arshad]

dnyhof: Thanks for the advice. I have my car at the dealership and they're going to look at the pads and rotors tomorrow and let me know if anything needs to be replaced or machined.

Bram: Yeah I'm getting the 6lb kit put in at Woodbine. I needed a bit more "oomph" ;-)

 

[nsxtasy]

It's not warped rotors; it's uneven deposits on the surface of the rotor, possibly combined with "hot spots" that have formed as a result, creating uneven thickness of the rotor when it is heated. When rotors are truly warped, they shudder at all speeds and temperatures, and you don't need to get them hot to make them shudder.

Read more here.

You can try having the rotors turned (refinished) but it may come back. If you replace the rotors (almost always the front rotors) it will cure it. Bed the new rotors to avoid a recurrence.

 

[nsxtasy]

I talked to John Vasos and he told me to take the rotors to my dealer and have them cut 2 thousanths(sp?) off of each rotor and reinstall them. He said even brand new rotors can be off by a very little bit and that would cause your shuddering.

He did say that even new rotors can be slightly off from true, but he did NOT say that it would be enough to cause shuddering. (I was there.) It isn't.

I have tried lots of different kinds rotors and I have never seen a set of rotors that did this when they were new.

This is NOT a problem in the rotor manufacture. It can occur from numerous causes, including improper bedding (most frequent cause), uneven deposits on the rotor surface (usually from improper bedding), hot spots (usually from those uneven deposits), and, for rear rotors, setting the parking brake when the brakes are hot.

 

[Arshad]

Thanks Ken, those links were very informative. I had no idea that you absolutely had to bed in your brakes in order to avoid this problem! They're going to be machining my front rotors, but from reading that first link it appears that even if I bed them in now, the original problem will still exist and will eventually come back again.

Now I know what to do when I replace the rotors!

 

[NSXDreamer2]

With a proper bed in, your brake shouldn't have any problem, I have to alternate street / race pad (well, bare with me there, I only use carbotech panther+ AS race pad which in reality is not even considered as a true race pad...) I can assure you that the good bed in makes a night and day difference. I also fround out that while the shuddering is disturbing, it doesn't neccesary affect the braking distance if you start ignoring the fact that your steering wheel is shaking My first two track days had a little shuddering, first time (it was a red flag in the 3rd lap of the first session, I have no choice but stopping at a slope w/ no cooling.) Second time, almost same situation. both I experienced extensive shuddering at the end of straightaway. I can assure you that if your rotor doesn't have any wear (eg. ridges on the edge of the rotors), you should be able to take the shuddering away from a good, proper bed-in. Also if you can keep your bed-in process from ABS engaging, it will also helped a more uniform deposit.

 

[comquat1]

He did say that even new rotors can be slightly off from true, but he did NOT say that it would be enough to cause shuddering. (I was there.) It isn't.

I have tried lots of different kinds rotors and I have never seen a set of rotors that did this when they were new.

This is NOT a problem in the rotor manufacture. It can occur from numerous causes, including improper bedding (most frequent cause), uneven deposits on the rotor surface (usually from improper bedding), hot spots (usually from those uneven deposits), and, for rear rotors, setting the parking brake when the brakes are hot.

Turns out my rotors were off, I tried fixing them the way Cobalt said (by sanding with 100 grit on the rotors and reinstalling the pads and rebedding) and that was a bit better but didn't solve it completely. Finally this weekend I brought them in to get them turned a bit, voila! No more shudder at any speed! There's a first time for everything I guess and if i can happen, it'll most likely happen to me whenever I try to do something myself instead of a dealer.