Brake vibration at the track

[Dhalsim]

I did a HPDE at Laguna Seca yesterday. I noticed after 2 laps when I hit the brakes I would get a pulsing/shaking feeling. Normally I would suspect a warped rotor but at the beginning of each session the vibration wasnt there. I also considered if it was the ABS but I wasnt hitting the brakes hard enough some of the times to be activating the ABS.

I had the TCS on the whole time if that makes a difference.

And I dont know if this is related but the day after the event the TCS light came on as I was cruising on the highway.

Anybody have any idea what this might be?

 

[Dhalsim]

I may have found the problem.

This is from a post from nsxtacy in another thread?

No; it's exactly the opposite. If the rotors are actually warped, the shudder will appear whether the brakes are hot or not. If the shudder only appears when the brakes get hot - such as on the racetrack, or braking hard on the highway - then that is not an indication of warped rotors. Rather, it indicates uneven brake pad deposits on the surface of the rotors, that causes them to expand unevenly. This is described in the Stoptech article (see link above).

Can I get confirmation that this is the likely culprit?

 

[NSXDreamer2]

It's really very very difficult to warp the rotors...

With some brake pads, you are most likely getting that shudder with deposit build up but it also had a lot to do with
1. how your brake..
2. proper cool down lap?
3. Not setting up e-brake after you back to paddock?

Now the other thing I would try and recommend is to scruffing the rotors with sanding paper, then do a proper bed-in...

NOTE, I found out that you must check your caliper pin and the rubber boots, as when those lubricant dried up, you mostly will getting more uneven deposit...

 

[Dhalsim]

I read the stoptech white paper on the subject and I think it is unlikely its a warped rotor and probably more a symptom of improper bedding of the pads by the PO.

Looks like I got some sanding to do.

 

[robfenn]

Thought it was deposits myself. As has been said, warping discs is hard.

As we found out though, it can be done! Tried getting the discs skimmed but the problem re-appeared towards the end of the next track day.

We skipped uprated discs and went straight for the AP 6 pots... but i'd go for some aftermarket discs/pads with some better temp ratings and see how you get on.

 

[nsxtasy]

Yup. As I've posted here previously, I used to encounter the very same shudder. At the time, I thought it was warped rotors, I replaced the front rotors, and the shudder went away, only to return with the new rotors after another few track events. Then I read the white papers on the Stoptech website, and started religiously bedding my rotors any time I replaced rotors, switched to a new pad, or encountered any shudder, and that took care of it, no more shudder.

If you're already experiencing shudder, you can try sanding the rotors, but it might be more effective just having them turned, with instructions to the folks doing it to take off no more than is absolutely necessary. (The Stoptech website suggests wearing off the deposits with a highly abrasive pad like Hawk Blues, but that involves two pad swaps, more trouble than benefit.) Then bed them afterwards, of course. Or you could replace them and then going forward just make sure to bed the rotors before the track event. And follow the bedding instructions on the Stoptech website! After you get the brakes REALLY HOT while bedding, you have to drive it home without using the brakes again and then park it overnight.

The TCS light is not related. The most common causes of the TCS light coming on are (a) improper tire sizes (note that with the wrong tire sizes, they can work with TCS when new, but can trigger it when one end wears more than the other), or (b) pavement irregularity (gravel, slick spot, etc).

 

[Dhalsim]

what grade sandpaper should I use to sand the rotors?

Also when the shop was swapping my tires I remember seeing an outline of the brake pad on the rotor so I know for sure there is brake pad residue on the rotors.

 

[nsxtasy]

Also when the shop was swapping my tires I remember seeing an outline of the brake pad on the rotor so I know for sure there is brake pad residue on the rotors.

That outline is normal (when you come to a stop) and happens from brake dust, not from the kind of residue that causes shudder.

 

[Dhalsim]

brake dust? I ran my finger over the brake pad impressions and it wasnt just dust.

 

[NSXDreamer2]

if your imprint is rust, then I wouldn't worry about it, if it's the pad material build in, you might really want to check the caliper pin as it might not retract properly (alas, sticking a little) then when you came off from the session and park, the rotors just boil the pads thus imprint...

Ken was right, you be better off turning the rotors, but I'll try sandpaper first. 150-200 should work fine.

 

[ChopsJazz]

I used to encounter the same shudder (at Laguna Seca also), even after changing rotors and pads and properly bedding them in. I found that the stock rotors would develop tiny hair-line cracks (like spider webs) on the surface of the rotors. I believe these cracks were causing slight variations in the rotor surface at higher temps. I started adjusting my braking technique to give the brakes more time to cool between uses and less time to heat up during use. That is, brake later (or rather, not too soon) and harder, and not trail-brake in corners. As I built up speed at each track I would determine where my braking points were and not brake too soon before that point. After that I would apply the brakes HARD, but not enough to get into the ABS (as many pros do today). Braking later and harder has helped stop the brake shudder for me.

 

[nsxtasy]

I used to encounter the same shudder (at Laguna Seca also), even after changing rotors and pads and properly bedding them in. I found that the stock rotors would develop tiny hair-line cracks (like spider webs) on the surface of the rotors. I believe these cracks were causing slight variations in the rotor surface at higher temps. I started adjusting my braking technique to give the brakes more time to cool between uses and less time to heat up during use. That is, brake later (or rather, not too soon) and harder, and not trail-brake in corners. As I built up speed at each track I would determine where my braking points were and not brake too soon before that point. After that I would apply the brakes HARD, but not enough to get into the ABS (as many pros do today). Braking later and harder has helped stop the brake shudder for me.

Braking later and harder is good advice. However, don't stop checking your rotors for cracks, just because there is no shudder! Cracks develop due to the massive expansion and contraction of the rotors with track use, and are almost unavoidable with ongoing track use. As Ken notes, they start as hairline spiderweb looking stuff. As you continue to drive on them, the cracks start to open up, typically in a radial direction. Once the cracks are roughly half an inch long, which is about when you can start feeling them if you run the edge of your fingernail over the surface (DON'T do this when the rotors are hot ), you need to replace the rotors, DO NOT keep driving on them on the track (if you drive home on those, avoid using the brakes any more than you have to). Also note that you may feel some vibration caused by the cracks when they reach this point; you typically don't feel it when the brakes are hot, out on the track (the cracks fill in as the rotors expand), but you do feel it when the brakes are cold, at the start of the day. Which is all the more reason for inspecting the rotors for cracks before every track session during the event.

 

[ChopsJazz]

Braking later and harder is good advice. However, don't stop checking your rotors for cracks, just because there is no shudder!

Amen!

 

[Dhalsim]

chops...in fact in my other post about my track day I mentioned that I thought I needed to do a better job on braking by braking harder and later going into the turns. I will check my rotors for the cracks and replace them if I find any. I will try your technique my next time out.

 

[ryans]

let me know if you need rotors, my brother gets a good price on brembos. My car used to the shudder too, I can't remmeber if it does it lately though.

 

[titaniumdave]

What pads are you running? Some street pads will do just what you have described once they get some heat into them. They will give inconsistent braking when hot, once they cool down they will be OK again.

You might just need a higher temp pad, bed them in well. Also helps to let the pads sit over night after you bed them, so you bed the new pads the night before your track day. Green pads can do the same thing, but generally they will get better through out the day.

 

[SMGNSX]

My brakes do the same thing even at $10K when they start to shutter heat them up better by braking earlier or harder to get rid of some of that pad material just hanging around. Laguna is a fast track and in the novice group you would not use the brakes long or hard enough being your speeds are lower,There are only 2 turns that need full on mashing brakes thats 11 and 2 and moderiat breaking at turn 7, the rest are love taps to settle the car for the turn in.

The fix:

1.You can change your pads to a race pad to clean the rotor then change back
2. Sand them (this does not work that great)
3. Turn the rotors
4. Stand on the brakes and get them hot to burn the crap off them:biggrin: the funnest.
5. Call me on my cell (you have the number and you are only 15 minutes away)

Steve

 

[standring]

Steve,
Remember just a couple weeks ago when you were instructing me at T-hill the same thing happened in my car during the last two sessions. I was able to get thru the first lap and by the second one even you could feel it in the passenger seat. You told me at the time to just go easy the following lap and then it was okay for a several turns.

I'm going to Laguna Seca next Saturday. I don't want to ruin my time there with the same problem coming up! Maybe I should change out my pads and rotors even if I don't see the exact problem. Although someone previously said that they did change everything and eventually had the problem appear at his next event.
-Jim S.

 

[SMGNSX]

Steve,
Remember just a couple weeks ago when you were instructing me at T-hill the same thing happened in my car during the last two sessions. I was able to get thru the first lap and by the second one even you could feel it in the passenger seat. You told me at the time to just go easy the following lap and then it was okay for a several turns.

I'm going to Laguna Seca next Saturday. I don't want to ruin my time there with the same problem coming up! Maybe I should change out my pads and rotors even if I don't see the exact problem. Although someone previously said that they did change everything and eventually had the problem appear at his next event.
-Jim S.

Hi Jim,

Your are right I said to cool your brakes down as they smelled that they were cooking and needed to cool down. You as well had some pad build up on the rotors from the stock pads and caused some shutter. Your shutter seem to lesson when they cooled.

The way to clean them is in the first couple laps get them hot to try to clean them off and then let them cool just like bedding in new pads. Thunderhill uses alot more hard brakeing than Laguna.

If you are still running the same pads and breakes you were running when we were togather you need to make some changes. You had said you were going to do alot of track events coming up, the new brake system we discussed would be in order at this time. You carry alot of speed when you drive and you must have the stopping power needed. You are also a late breaker and with that the car needs to slow down or stop quicker with that speed. The stock brakes dont like late breakers as you make much more heat quicker.
I would go with the set up You Kip and I, talked about or chang the stock brakes as follows, SS brake lines, vented and slotted rotors and a better pad front and rear (like a HP street pad or a track pad) also completley flush your system and use the Motul brake fluid.

Laguna seca you need good hard breaking and you being a late breaker might have to breake earlier or you will be stuck in the gravel in turn 2 so some brake work would good for you. 85,000 miles on your rotors, they need to go for the track. Give me a call if you have the number or email me ar call Shad @ 916-861-0032 ( I talked to him last week about your car and said you would be calling him so he is expecting your call)

Steve

 

[2slow2speed]

IMHO, Laguna Seca is much harder on the stock brakes or any aftermarket brake system on a NSX than Thunderhill being run in the CCW direction will ever be.

The combo between T10, T11, T2 and T3, T4 at Laguna Seca is brutal it does not allow the brakes to cool off. That happens to most cars that track at Laguna Seca. I've never heard anyone make a comment that Thill is harder on the brakes than Laguna

Maybe Steve got confused when he wrote the comment above??

996 Porsche GT2's with PCCB would cook their ceramic rotors at Laguna Seca, that is how brutal that track can be for fast cars. (The NSX is a relatively fast car for Laguna given how underbraked they are)

Just my 2 cents. All the above advice applies however. I was just making a note about the relative harshness on the brakes between LS and Thill.

 

[2slow2speed]

Steve,
Remember just a couple weeks ago when you were instructing me at T-hill the same thing happened in my car during the last two sessions. I was able to get thru the first lap and by the second one even you could feel it in the passenger seat. You told me at the time to just go easy the following lap and then it was okay for a several turns.

I'm going to Laguna Seca next Saturday. I don't want to ruin my time there with the same problem coming up! Maybe I should change out my pads and rotors even if I don't see the exact problem. Although someone previously said that they did change everything and eventually had the problem appear at his next event.
-Jim S.

Try searching for nsxtasy's brake ducting post, that is one of the few ways that your stock NSX brakes will survive at Laguna if you are fast at Laguna.

Having confidence in your equipment is rule #1 in tracking

 

[nsxtasy]

SS brake lines, vented and slotted rotors and a better pad front and rear (like a HP street pad or a track pad) also completley flush your system and use the Motul brake fluid.

You don't need stainless steel brake lines unless you want them for the bling. The only performance benefit is to prevent a spongy brake pedal due to flex in the rubber lines. I've never had a spongy brake pedal on my NSX with stock brake lines, and if you don't, don't bother with them.

All decent rotors are vented, including the stock rotors. Slotted rotors don't provide any benefit. They don't hurt, either. Based on my experience, they will provide the exact same performance and longevity as solid-faced rotors or drilled rotors, all of which will eventually crack after roughly the same amount of track use.

For pads, I've been very happy with the Hawk HP Plus (HP+) pad for combined street and track use. The stock pads are pretty good for both purposes, too, in my experience.

Fluid has nothing to do with brake shudder. I make sure that any time I'm on the track, my fluid has been flushed within the previous 12 months (in my part of the country, the track season is seven months long, so I just do it every spring). I use Motul RBF 600 too.

 

[titaniumdave]

You don't need stainless steel brake lines unless you want them for the bling. The only performance benefit is to prevent a spongy brake pedal due to flex in the rubber lines. I've never had a spongy brake pedal on my NSX with stock brake lines, and if you don't, don't bother with them.

Ken is right, but brake lines are a wear item. It is good preventative maintainence to replace them every 10-15 years. SS line are the same price or less than stock lines from Honda, might as well put them on IMO.

 

[NSFRBLX]

Ken is right, but brake lines are a wear item. It is good preventative maintainence to replace them every 10-15 years. SS line are the same price or less than stock lines from Honda, might as well put them on IMO.

Make sure your SS brake lines are DOT approved. The shop that made mine used DOT stamped lines and pressure tested them before handing them over to me. The tech who made them mentioned if I was ever to be in an accident and the brakes were in question. I would expose myself to liability.