What is the weak link (braking system)

[MJK]

Ok, so I just had my first track experience at Mid-Ohio. Very addictive. I believe I was reasonably speedy for a first timer, but started to lose a little confidence in my brakes as I got faster.

I went to the track with OE 97+ brakes, OE 97+ rotors, Carbotech Bobcats, fresh ATE and all else stock. Pads and rotors both wore fine, but the brakes got a little soft towards the end of some later sessions. They recovered somewhat when cooled, but not all the way.

I assume this is mostly the fluid, and ordered some motul to flush the system again.

Is there anything else I should do here?

(like pads, stainless lines, air management). Any input would be appreciated.

 

[Acura NsX Pilot]

I am no track expert but I think most will suggest going to a more aggressive pad first. If all else fails BBK ......... Ohhh damm that go fast crack pipe !

 

[MJK]

Well, I was looking around and it seems like the next step up the Carbotech product lineup is the Panther+, which squeals on the street. I'd rather not do that if there is an acceptable street/track solution.

So, can I keep the temps down with deflectors/ducting? Should I got to another pad mfr? Will just Motul make the difference I need from ATE?

If it helps any, the place I could feel the weakness the most was at the end of the back straight going from 130 -> 65.

 

[asylum]

More agressive pads can resist better to heat... and then you will reach higher temperatures. If you go on a track that is very hard with brakes and you make several sessions during the day, no doubt you will reach the fluid boiling point, no matter the quality of it.

Hence, you need something to reduce the heat, which is (by cost) :

- cooling ducts (if well done, this can be very efficient)
- better rotors (with better cooling capacities and/or 2 piece rotors)
- bigger rotors / bigger calipers (bigger surface)

 

[Briank]

In my first session on the second day at mid-Ohio I got some brake fade also from about 125 to 50 at the end the end of the long straight. My 91 is stock with except for Stop-Tech two piece rotors in the front and I run Valvoline synpower brake fluid. What caused this problem was I was braking way too early starting at the beginning of the cones if I would have gone in further and braked harder I would have not had the fade issue.

 

[EvilSTi7]

Now that you've gone to the track once, you will probably have to start using dedicated street and track pads. Unfortunately once you start to get the hang of braking hard anything decent on the street will give up under the punishment the track offers.

The ATE fluid will be fine, there really isn't a reason to switch it. I'm pretty sure the bobcats are meant to be street pads, so they probably contributed pretty heavily to your brake fade problem.

Like i said earlier, your going to have to run a dedicated track pad. I'm not sure if pagid makes applications for the nsx but i would definitely check out the Pagid Yellows. If you want to stick with the carbotech's people have had good results with the XP10's in front and the XP8's in the rear.

Also just to through some other choices out there, Performance Friction 01's (PFC-01) and Hawk DTC70's.

 

[gjoey66]

I have a dedicated track car (944 turbo) and almost everyone in my series uses ATE because we get it free with our Pagids...I really really doubt you boiled fresh ATE...maybe after 2 seasons...and I'd still say with regular bleeding it would be fine. I'm not positive about the NSX, considering racing one that's why i'm on this forum, but stainless lines are the first thing you need to switch to if you're going to be tracking a car. Secondly, you absolutely can't use street pads on a track with a car that heavy and abuse the brakes...they can't handle the heat...don't brake as hard...and therefore you break longer and longer just making it worst...you need to get a set of track pads and switch them before DE's, plus after you start getting quicker you'll be going through a set of pads in 3-6 weekends.

 

[nsxtasy]

I have driven 12,500 actual track miles on my NSX, and an equal number on other cars. Some of the advice given above is very good. Some of it is inconsistent with my experience.

I would guess that the two biggest reasons you encountered fade are driver technique, and the Bobcat pads. As Briank aptly points out, track novices have a tendency to start braking too early, and also to brake more, i.e. with similar entry speeds at the end of the straight, but with slower speeds going through the corners. I wish I had a chance to give you a ride at the event - hopefully you rode with another instructor - to demonstrate this.

Although I have not personally used the Carbotech Bobcat pads, I have heard that they are really just street pads, and not suitable as a dual-purpose street-track pad. I have used the Carbotech Panther Plus pads, which work well on the track, but as you note, squeal (LOUD!) on the street. Right now I am using the Hawk HP Plus pads, and am very happy with them. They work well on the track, and don't make any noise on the street. They tend to dust a lot, but on the track, so do all pads.

I see that some people above are recommending track-only pads. Track pads certainly give an added bite, but their downsides (squealing and poor bite when cold) make them unsuitable for street use IMHO. Those who are willing to swap pads before and after track events can certainly benefit from track pads. I'm not. And I'm very happy with the performance of good street-track pads like the HP+ (even though true track pads may give slightly better performance). I don't think track-only pads are the only way to enjoy excellent braking on the track with the NSX. Maybe if you're in competition and looking for tenths of a second in lap time, it would be a different story.

It's hard to tell whether you only faded the pads, or actually boiled the fluid, but it won't hurt to step up to Motul RBF 600 fluid. ATE fluid is good, too, but Motul has significantly higher boiling points.

I don't think you need stainless steel brake lines. Those who claim benefits with stainless lines do so based on swelling of rubber brake lines and a spongy brake pedal. I have my original stock brake lines and have never experienced a spongy brake pedal, even after 12,500 track miles on them.

I have 2.5" cooling ducts running from my front air dam to the front brake hubs, where they are zip-tied to a flange welded to a hole cut in the brake splash shields. The ducts help. They're also a bit of a PITA, as they occasionally come off or wear. I suggest first switching to Motul and to another brake pad. If you're still encountering problems, then you might want to install cooling ducts.

In addition to the cooling ducts and Hawk HP+ pads, I still have the stock calipers and stock-sized rotors (I've used many kinds and they're all fine). And I was doing pretty darn well in the instructor run group (I think only three instructors passed me in NSXs, and two of them were race cars). Which ought to tell you something about whether or not you need anything expensive.

 

[gjoey66]

I don't think you need stainless steel brake lines. Those who claim benefits with stainless lines do so based on swelling of rubber brake lines and a spongy brake pedal. I have my original stock brake lines and have never experienced a spongy brake pedal, even after 12,500 track miles on them.

ok...first of all, the stainless brake lines are for safety not just to eek a few tenths out of a lap...and if you're boiling ATE fluid...I promise you those rubber lines are swelling and the reason you get brake fade. Yes boiled fluid will turn moister in the system into air bubbles which will contribute to brake fade...but you'd be really hard pressed to achieve this in one track event, darn near impossible, the fluid itself has the capasity to hold a small ammount of moisture and with a flushed system, you must have done something wrong. Now if we were talking a 350rwhp monster that's having to bring the car down from 120mph at every corner...yea you might need Motul...and don't get me wrong, I'd use it over ATE because i know it's better, but i sure wouldn't diagnose a brake fad problem on a stock car to ATE. BE VERY CAREFUL OF ADVISE YOU GET...TOO MANY TIMES PEOPLE CHASE PROBLEMS WITH LOTS OF $$$ BECAUSE OF FORUM OPINIONS.

I'd talk to an instructor at an event who not only drives their own car but sees many others out there...I've also seen many many track miles, take my advice keep looking for someone that solved the problem...then establish who fixed it with the simplest, safest, and cheapest solution...that will keep you coming to the track.

and I wouldn't say 57deg F is a considerable dry boiling point advantage...since this was fresh fluid. if your fluid temps are in the 500's period...you might have another problem.

 

[MJK]

Motul is on the way, and may put some stainless lines on at the same time. I will swap over to the Hawk HP+ pads when the bobcats go, or before my next track event (whichever comes first). If that doesn't do it, I'll get/make some ducts.

Thanks everyone for the input.

In my first session on the second day at mid-Ohio I got some brake fade also from about 125 to 50 at the end the end of the long straight. My 91 is stock with except for Stop-Tech two piece rotors in the front and I run Valvoline synpower brake fluid. What caused this problem was I was braking way too early starting at the beginning of the cones if I would have gone in further and braked harder I would have not had the fade issue.

Good info, thanks Brian.

If memory serves I was braking at the 4 cones and not standing on them quite as hard as my instructor (who had a BMW w/APs). Not ideal, which likely heated everything up a little, which made the brakes a little softer, which made me a little more cautious, which heated the brakes more, etc. By the time I was confident enough to really stomp on them, there was not 100% of it left. I'd definitely like to avoid this next time.

I would guess that the two biggest reasons you encountered fade are driver technique, and the Bobcat pads. As Briank aptly points out, track novices have a tendency to start braking too early, and also to brake more, i.e. with similar entry speeds at the end of the straight, but with slower speeds going through the corners. I wish I had a chance to give you a ride at the event - hopefully you rode with another instructor - to demonstrate this.

You are probably spot on, thanks for the advice. I did not get a chance to ride with an instructor in an NSX, but did in other cars. If I manage to catch you at another event, I would love a ride in an NSX to get a feel for everything.

 

[stuntman]

Stock lines, (especially high mileage lines - 100,000+) start to expand during heavy usage. SS lines offer an improved/stiffer pedal, especially high mileage cars. I would bet that you would feel a huge improvement with SS lines, i'm surprised with as much tracking that you do you havn't already upgraded to SS lines.

Ive installed (and driven on) SS lines on over 20 cars, track cars, daily drivers, and double-duty. Everyone (including my mom who isn't he best driver in the world) felt a huge improvement with SS lines. To say SS lines wont improve the feel is a false statement. I don't know why you keep trying to argue that SS lines wont improve the feel when they obviously do.

I'm not going to go into my credentials (some of you may know) but I can say that I have a few laps around a track in stock and SS lined cars before :biggrin: and with my experience, they do make a difference.



In regards to Motul/ATE Dry/Wet boiling points:
ATE Super Blue Racing 536/392
Motul Racing 600 585/421

ATE tends to be a bit cheaper than Motul and offers very similar performance (20-50* is not HUGE). It's a better bang/buck in most cases IMO. I use both and think both are great products, but ATE is easier to find around here and plus I like the blue...

 

[BioBanker]

I will echo almost everything that Ken has said, but suggest that the SS lines WITH BLEEDERS are probably also a good investment.

My NSX has about 6,000 track miles on it. Im not one for hassel, so I daily drive it just as I track it. Same pads (HP+, like Ken) and RA1s day in and day out. I dont want to swap either pads or rubber before and after an event; who has time for that? Id rather spend the 30 minutes doing a basic tech of the car instead.

The braking system on my CTSCd NSX is stock caliper, HP+ pads, Motul 600, SS lines and stock sized rotors (powerslots).

I have never perceived any fade with this set up. Come to think of it, full stock worked fine for me too (but that was 10 seconds a lap ago). My pads squeal on the street, but not like race pads. I dont mind it.

If I were to do it all over again, I would install bleeders and consider skipping the high price Motul for a high quality, but less resiliant, brake fluid that is way cheaper. The Ford fluid for example. That way Id be able to flush the fluid after EVERY event and I bet the average quality of fluid in my lines would be higher over the longer term than it is now.

EDIT: Ive actually picked up a set of GY F1 GSD3s for XPO - didnt want to get stuck over the weekend in the rain with my bald RA1s. So the GYs are on my car right this second. Ill swap back to RA1s once track season resumes.

 

[L8apex32]

As we all know, MY opinion is the one that counts. :biggrin:

The whole answer is that your (street) pads were losing grip at higher temperatures. Pads are designed with a certain friction level at certain temperatures. Street pads have good grip and low temps. Consider a winter day, first stop of the day. Track pads have getter grip when warmer. Full race pads don't grip that well when cold.

That is what you were feeling. Period.

Unless you have a failure in your system, you won't ever boil your fluid. All brake problems I've had in the NSX have been about temperature of pads and rotor, not of fluid. I've never boiled my fluid in the NSX (or any other street car) and I've tried.

I have boiled the fluid in my recently sold SRF race car twice. Once it was due to the gradual failure of a wheel bearing. Full race conditions, hot day, with extra heat from a failed bearing is what it takes to boil brake fluid. The other time was after a minor bump from an RX-7 (1st gen, much heavier than a SRF) that messed up something in the U-joints/half shafts. Again, caused too much heat in one corner.

Here is another fact. Boiled fluid pushes the fluid out of the caliper and back into the brake lines and back towards your master cylinder. The bubbles remain in or near the caliper. It is a MAJOR loss of braking... not a gradual "I felt it on this area of the track". It also gets worse every corner and every lap. And, if one corner boils, say right front, the left front will soon. Similarly, if the rears boil (after my accident with the RX-7), then the fronts do. Most of you have never experienced this.

And, you will never notice the difference between the OEM brake lines and the stainless ones. Try to find a post or story anywhere on a failed/expanded/stretched brake line. You can't.

If you want to test your brake lines, push on your brake pedal with both feet as hard as you can. Feel it stretch? Me neither.

By the way, you can find a testimony for any product. Take them for what they are worth.

Anyway, this is an on-going debate by those that have some experience, mid level experience and lots of experience.

If you want to go fast on the track, get better pads and don't let yourself worry about all the other suggestions. Remember, its the driver that *really* matters and the point is to have fun.

One final thought. If you track often, you will want better tires. That will likely mean getting a 2nd set of wheels for the fast tires. When switching between street tires and track tires, it is a convenient time to swap pads. That's what most of us "fast" guys do.

 

[john@johnhudakracing]

Everyone in run group 'A' should be bumped to 'C'

 

[DCNSX]

If you're on a budget, as I am, two less-expensive improvements are to remove your brake "rain" shields, front and rear. I believe there is a DIY. Some have reported heat deterioration of a suspension piece (a bushing?) but you can leave the part of the shield in to protect that.

another improvement is the Dali front brake air deflectors- about 3x larger in area compared to the OEM deflectors, these are a cheaper (and more easily installed) alternative to full ducting right into the hub. but less effective.

I've found these two improvements have helped my braking and I do about 8-12 track days per year.

Also, I run AXXIS Ultimate pads. They dust a LOT, even in street use, but are fine on track.

 

[nsxtasy]

My NSX has about 6,000 track miles on it. Im not one for hassel, so I daily drive it just as I track it. Same pads (HP+, like Ken) and RA1s day in and day out. I dont want to swap either pads or rubber before and after an event; who has time for that? Id rather spend the 30 minutes doing a basic tech of the car instead.

The braking system on my CTSCd NSX is stock caliper, HP+ pads, Motul 600, SS lines and stock sized rotors (powerslots).

I have never perceived any fade with this set up. Come to think of it, full stock worked fine for me too (but that was 10 seconds a lap ago). My pads squeal on the street, but not like race pads. I dont mind it.

What about "green pad syndrome"? You know, your session the first time the pads get really hot. Don't they fade for you? They do for me; just about any pad does. But after a session or two, they're fine for the remaining life of the pad.

Interesting that yours squeal on the street; mine don't, at all. < shrug >

If I were to do it all over again, I would install bleeders and consider skipping the high price Motul for a high quality, but less resiliant, brake fluid that is way cheaper. The Ford fluid for example. That way Id be able to flush the fluid after EVERY event and I bet the average quality of fluid in my lines would be higher over the longer term than it is now.

Maybe, maybe not.

The folks at Acura of Brookfield (WI) do a lot of track-prepping of NSXs, and go to a lot of track events. They have a brake fluid tester they use to test the actual boiling point of the fluid. They find that with street cars using DOT 3 or DOT 4 fluid, the boiling point goes down around 20 degrees F per year. With heavily tracked cars using high-temp fluid like Motul, it can go down up to 100 degrees F per year (or, about 50 degrees during the six-month track season in northern areas). Which means that if you flush the fluid in spring with Motul (593F boiling point), even at the very end of the season, its boiling point is still higher than fresh Ford heavy-duty DOT 3 PM-1C fluid (500F). (Note that Ford changed its fluid last year and the boiling point is lower than in the past.)

The whole answer is that your (street) pads were losing grip at higher temperatures. Pads are designed with a certain friction level at certain temperatures. Street pads have good grip and low temps. Consider a winter day, first stop of the day. Track pads have getter grip when warmer. Full race pads don't grip that well when cold.

That is what you were feeling. Period.

I don't agree with this. MJK was experiencing fade at the end of a track session (on a hot day). Not at the start of a session.

Unless you have a failure in your system, you won't ever boil your fluid. All brake problems I've had in the NSX have been about temperature of pads and rotor, not of fluid. I've never boiled my fluid in the NSX (or any other street car) and I've tried.

I have boiled the fluid in my recently sold SRF race car twice. Once it was due to the gradual failure of a wheel bearing. Full race conditions, hot day, with extra heat from a failed bearing is what it takes to boil brake fluid. The other time was after a minor bump from an RX-7 (1st gen, much heavier than a SRF) that messed up something in the U-joints/half shafts. Again, caused too much heat in one corner.

Here is another fact. Boiled fluid pushes the fluid out of the caliper and back into the brake lines and back towards your master cylinder. The bubbles remain in or near the caliper. It is a MAJOR loss of braking... not a gradual "I felt it on this area of the track". It also gets worse every corner and every lap. And, if one corner boils, say right front, the left front will soon. Similarly, if the rears boil (after my accident with the RX-7), then the fronts do. Most of you have never experienced this.

This, I do agree with, and it's an excellent point. Boiling the fluid is not a "sort of fading" feeling. It's a major failure of the braking system. I experienced it, not on the NSX, but on an older track car before I started using Motul fluid.

And, you will never notice the difference between the OEM brake lines and the stainless ones. Try to find a post or story anywhere on a failed/expanded/stretched brake line. You can't.

If you want to test your brake lines, push on your brake pedal with both feet as hard as you can. Feel it stretch? Me neither.

By the way, you can find a testimony for any product. Take them for what they are worth.

Yup.

It's also worth noting that a lot of parts on the NSX were designed with high performance in mind. For all I know, it's quite possible, even likely, that brake lines can swell on many other cars, and stainless steel lines will prevent that. It just hasn't happened on my NSX.

If you're on a budget, as I am, two less-expensive improvements are to remove your brake "rain" shields, front and rear.

There are two downsides to keep in mind when deciding whether or not to do this. One is that the splash guards are between the brake hubs and the ball joints. If you remove them, that exposes the ball joints to a lot more heat, and this can lead to faster deterioration of the ball joints. And they're expensive to replace, because you have to replace the entire knuckle as well. What the folks at Acura of Brookfield do on NSXs is to cut only part of the splash guards so that the portion alongside the ball joint remains.

The other downside is if you want to install brake cooling ducts, you can use those splash guards as a mounting point. That's what I did, with a hole cut in them and a flange welded to the edge of the hole, and the ends of the cooling ducts zip-tied to the flange.

 

[docjohn]

MJK there is alot of good info here,after reading through it all I would say #1 thing to do( assuming you will track again) is to use the brakes harder for shorter periods,meaning braking is an aquired skill just like driving the "line".In the future make a point to have your instructer teach you how to use the brakes just enough to do what they need to do in order to get you to propper turn in.Most newbs at the track are stresssing the brakes 40-50 % more than an instructer level driver would be at the same speeds.Remember however fast you may have felt you were going in your group the really fast guys were doing it 10-20 sec a lap quicker Some of those really fast guys I'm sure had stock callipers:smile:

 

[docjohn]

[


-I dont quite understand this sentence....[/QUOTE]

What I mean to say is that if you drove at MJK"s pace you would be on the brakes 40-50% less than him.Specificly as a racer of some renown you would be braking later or in some instances not at all,for the same turns at the same speed that a novice would be,,, get it now?

 

[MJK]

^^^

Doc, I am sure that is part of the problem. I did very well in my group with this, but I am sure there is plenty of room for improvement compared to anyone with more experience.

At this point, I think I am after a setup that is streetable and is still a little more confidence inspiring on the track. Only having 60% of the braking ability you started the day with is not a good feeling, which makes you brake a little earlier, which exacerbates the problem, etc. Just looking to keep everything at 100% long enough to improve my technique.

 

[2slow2speed]

^^^

Doc, I am sure that is part of the problem. I did very well in my group with this, but I am sure there is plenty of room for improvement compared to anyone with more experience.

At this point, I think I am after a setup that is streetable and is still a little more confidence inspiring on the track. Only having 60% of the braking ability you started the day with is not a good feeling, which makes you brake a little earlier, which exacerbates the problem, etc. Just looking to keep everything at 100% long enough to improve my technique.

Not sure if this will help, Carbotech P+'s will dust quite a bit but fortunately the brake dust is not corrosive (unlike a pad like the Hawk Blue), you can minimize a bit of the squeal if you use the shim that comes with the OEM brake setup with some brake anti-squeal-compound, once it starts to deteriorate/breakdown (due to the high temps at the track) you will start hearing the squealing again

BTW: You might only have had 60% of the braking ability later in the day because you were going faster and having to slow down more than when you started during the day, it's not a bad thing because it means that you were becoming faster overall

 

[BioBanker]

What about "green pad syndrome"? You know, your session the first time the pads get really hot. Don't they fade for you? They do for me; just about any pad does. But after a session or two, they're fine for the remaining life of the pad.

Interesting that yours squeal on the street; mine don't, at all. < shrug >

I may not pick that up because the first session of the day is usually just spent driving around out there at 6/10ths to get a sense of the car and the track that day, plus I usually do some type of break in on them prior to the track. My sessions may also be short; they're always less than 25 mintues, usually 15 to 20. Plus, Mosport's not a track that's tough on brakes. It is super fast. Get on the gas and stay on it.

Mine squeal all right! Not bad, but enough that Ive had antisqueal compound put between the pad and the caliper. Still squeal, but only on the street in slow stops.

 

[asylum]

I am back from a track event. The first time using Carbotech P+ front and rear. I have the Ritmo brake deflectors, stock rear rotors, Dixcel slotted front rotors from gt-rom (these are in fact stock design rotors with slots).

The result was very good and I had no signs of fading or boiling fluid. Perhaps Carbotech P+ pads have better heat dissipation than my previous pads.

My Carbotech P+ do not squeal at all. Be sure you use a good grease.

 

[nsxtasy]

My Carbotech P+ do not squeal at all. Be sure you use a good grease.

I used anti-squeal compound on the backing plates. They squealed (LOUD!) anyway. < shrug >

 

[L8apex32]

I am back from a track event. The first time using Carbotech P+ front and rear. I have the Ritmo brake deflectors, stock rear rotors, Dixcel slotted front rotors from gt-rom (these are in fact stock design rotors with slots).

The result was very good and I had no signs of fading or boiling fluid. Perhaps Carbotech P+ pads have better heat dissipation than my previous pads.

My Carbotech P+ do not squeal at all. Be sure you use a good grease.

The Carbotech Panther+ pads get high marks from me, too. They work great on the track.

I've had the Panther+ pads on since April (street and track use) and I'm on my 2nd set now. The first set did not really squeal much and this one squeals only a little. It is certainly tolerable for me and the wife... my muffler is much more obnoxious.

I only say this because pad squeal tends to vary between cars and people. You may find it to be tolerable, but you may not. And, you my get much worse squeal like NSXTASY does which I might even find too much. YMMV.

 

[MJK]

Where are you guys getting the anti-squeal compound, particularly those of you for whom is it working well?

Any place I can get it online?

Gracias all for the help. :smile: