Another brake question (brake ducts)

[asylum]

Ok now that I have tracked my NSX a few times, I realised that the brakes become totally inefficient after some laps. But that's not really astonishing from stock brakes.

To what I have read on the forum, it seems that it is not really important to change the rotors untill stock one are cracked. And even if it is the case, which aftermarket brakes are the best concerning cooling ? Have you detected a big difference in brake temperature at track events using aftermarket rotors (stock size) compared to stock brakes ? Are they all pretty equivalent ?

So first I will go with pads (Carbotech Panthers or Hawk) and a good fluid.

I have read that brake ducts are important and makes the front brakes ~ 100° cooler. Which one are the best bang for the buck ?

 

[MvM]

hi Asylum,

I had the same experience that you have with the NSX stock brakes.
First thing that made a big difference for me was having somebody with track experience drive with me and telling me when to brake and when not. I think that after a few sessions I was braking much less than before and that of course will also make a difference in how your brakes will perform.

Second, I added the Dali racing air deflectors and switched to Axxis pads. Maybe not the best around but they are not expensive and have better bite than stock. You could also go with Ferrodo 2500 pads since you are (also) in Europe. This also made some difference.

Last, for now, I changed the rotors from stock to the Stoptech Aerorotors. This really made a big difference. Compared to OEM the Stoptech rotors have a really good curved vane design that keeps the rotors a lot cooler. I was driving at Spa with this setup and although I had an accident that day it had nothing to do with the brakes because even at the end of a session they did not fade and I was really pushing the car hard (a little too hard actually....).
I had also change the fluid to Motul.

Since then I have added SS-lines and am considering the upgrade to the RB-rotors in the 97+ sizes with larger brackets and my original calipers. However, I have to wait for the brackets to be available again.

 

[Hugh]

You need to do the following:

Use a hugh quality/high boiling point brake fluid such as Motul RBF-600.
Install stainless or kevlar lines.
Use the right pads. Carbotech Panther, Axxis Ultimates etc... Go to SoS and look at their comparison matrix.
Make sure your rotors are still within spec, if not replace them.
Get some cooling to the rotors. Dali air deflectors work fine or you can go up a step and install ducintg. There's a DIY about this in the current issue of NSX Driver.

Have fun!

 

[VBNSX]

agreed w/ the dali air deflectors. With my setup I have the dali air deflectors and two 3" high speed fans that blow into the centers of the hats. Together they work wonderfully.

good luck out there.

x

 

[nsxtasy]

Ok now that I have tracked my NSX a few times, I realised that the brakes become totally inefficient after some laps. But that's not really astonishing from stock brakes.

Actually, the stock brakes are just fine. I did tons of track events with the stock brakes for years, with no problems with fade ("inefficiency", in your terms). The one caveat is that the stock pads, like many brake pads, fade the first session you get them really hot on the track (and sometimes the second session, too), but then they are fine for the remaining life of the pad. This is sometimes called "green pad syndrome" by track folks. It's the most likely explanation for what you experienced.

Or, perhaps you're using inferior aftermarket pads. (Not all aftermarket pads are inferior to stock pads, but cheap ones you get at the auto parts store are, as are Legend pads which will also fit the NSX.)

It's also possible that you have air in your brake system or that you boiled your brake fluid. I agree with Hugh's suggestion that getting high-temperature brake fluid (e.g. Motul RBF 600) is a good idea.

In any case, the stock NSX brake system is perfectly adequate for track use and does not fade.

To what I have read on the forum, it seems that it is not really important to change the rotors untill stock one are cracked.

Or, if they are at or below the minimum spec for thickness.

which aftermarket brakes are the best concerning cooling ? Have you detected a big difference in brake temperature at track events using aftermarket rotors (stock size) compared to stock brakes ? Are they all pretty equivalent ?

I've tried a lot of different brake rotors. That's one of the advantages of extensive track use; you can try a new kind every time you change them! I'm now on the 12th set of front rotors on my NSX. In my experience, all the different one-piece rotors I've tried last the same amount of time before they eventually crack, typically 4-8 events with ~150 track miles each. Two-piece rotors such as the Stoptech Aerorotors last longer, 6-12 events, but eventually crack also. I have not seen any difference in stopping power, which is limited by the tires rather than the brakes.

So first I will go with pads (Carbotech Panthers or Hawk) and a good fluid.

I tried the Carbotech Panther Plus and didn't like it. It's fine for track use but it squealed too much on the street for my taste. I greatly prefer the Cobalt GT Sport pads, which rarely squeal and have a nice bite and just as much stopping power. The Hawk HP Plus weren't bad, either.

I have read that brake ducts are important and makes the front brakes ~ 100° cooler. Which one are the best bang for the buck ?

You'll need to fabricate them yourself. You can get the NACA inlet ducts and high-temp ducting from Pegasus.

Second, I added the Dali racing air deflectors and switched to Axxis pads. Maybe not the best around but they are not expensive and have better bite than stock.

Be careful when buying Axxis pads, since they sell several types of pads. They make the Axxis Ultimate, which I haven't tried. They also make Axxis Metalmasters, which I have tried and were absolute garbage, totally unsuitable for track use.

Install stainless or kevlar lines.

I think stainless steel brake lines are totally unnecessary, and they are a maintenance headache. The first question to ask, before doing anything in this regard, is whether your brake pedal feels spongey (and don't even consider the question unless you're sure that all the air is out of your system). Those who claim advantages for stainless lines say that their only advantage is to prevent a spongey pedal due to the brake lines swelling. With over 11K of track miles on my 16-year-old NSX, I have never had a spongey brake pedal, and I still have my original brake lines. And most folks who get stainless lines recommend then replacing them every few years, because dirt can get in between the outer and inner layers of the lines and cause them to abrade. Unless you have a spongey brake pedal, "If it ain't broke, don't fix it."

 

[asylum]

Thanks a lot for these answers. The air ducts with ventilators seems a little bit to much for a mainly street used car.

But will the air duct sold by SOS (for example) help a little bit or is it worthless ?

 

[Ponyboy]

But will the air duct sold by SOS (for example) help a little bit or is it worthless ?

Those are a good idea (supposing you're talking about the Ritmo ducts) and will be more effective than something smaller or not there at all. I only had issues with my front rotors and went to the Stoptech Aerorotors in stock 11.1" size and then eventually went to a front Stoptech big brake kit. For your application, I'd strongly consider just getting the Aerorotors, ducting, good dual use brake pads, hi-temp fluid, and some braided SS lines. That setup should be more than sufficient.

As a further precaution, you can also get the interior surface of the rotors coated with a heat radiating material (BBE from Swaintech).

http://www.swaintech.com/store.asp?pid=10968

 

[VintageracerNYC]

I have tried many combos in my track use and just recently upgraded to a new setup from Racingbrake.com...its a larger two piece directional rotor with a bracket to use the stock calipers and I am using Hawk HT60 pads...I have not Raced on them as of yet but tested them and they are working great!!!!!! BUT the Hawk compound I am using is NOT a street compound..also be sure and use Motul 600 as it has a high dry and wet boiling point...and I am using fully dedicated 5" ducts to each wheel from the front...look up RACINGBRAKE.COM as they were really nice to deal with. Lots of good info and advice

 

[nsxtasy]

I am using fully dedicated 5" ducts to each wheel from the front...

I take it you have removed the air conditioning from your car?

With the A/C left intact, the largest diameter ducts we could manage were 2.5 inches, which could just barely squeeze alongside the lower corners of the radiator above the core support.

 

[Scin]

Good pads will easily fix this. The NSX brakes are decent, but not exactly known for spectacular performance. I had several instructors drive my car when it had Panther Plus pads on it, and they commented on the great brakes. Some of these guys drove Porsches! So for brake feel/stopping power switch your pads.

I like the Panther Plus the best for the track (when considering street/track pads and not track only pads), but they squeek something aweful on the street. I currently have the GT-Sport pads that Ken preaches about They are a nice upgrade over stock too, but not as good as the Panther Plus on the track. They are however better on the street, they perform nicer at lower temps then the Panthers do.

After running with better pads I went through a set of new brembo rotors in two track weekends. I ended up getting Stoptech Floating rotors after that. You may end up in the same situation. I would suggest getting the Dali brake deflectors or better yet do what Ken did with his ducting setup (I currently run the deflectors because I am too lazy to duct just yet).

Ok now that I have tracked my NSX a few times, I realised that the brakes become totally inefficient after some laps. But that's not really astonishing from stock brakes.

To what I have read on the forum, it seems that it is not really important to change the rotors untill stock one are cracked. And even if it is the case, which aftermarket brakes are the best concerning cooling ? Have you detected a big difference in brake temperature at track events using aftermarket rotors (stock size) compared to stock brakes ? Are they all pretty equivalent ?

So first I will go with pads (Carbotech Panthers or Hawk) and a good fluid.

I have read that brake ducts are important and makes the front brakes ~ 100° cooler. Which one are the best bang for the buck ?

 

[VintageracerNYC]

Dear NSXTASY

Indeed I have removed all of the a/c and its condensers in the front. I have removed EVERYTHING actually! The Hawk race pads really work incredibly well and the new rotors from Racingbrake made a huge difference! I can now ALMOST brake as late as the Porsche Cup cars I race against with the stock calipers!

 

[goldNSX]

Thanks a lot for these answers. The air ducts with ventilators seems a little bit to much for a mainly street used car.

But will the air duct sold by SOS (for example) help a little bit or is it worthless ?

If you're interested in the SOS brake ducts I have a new pair here in Switzerland for sale.

 

[NSXLR8R]

The other option is to just use the Porsche deflectors (See FAQ). I installed these on my car in 98, planning to take temp. reading then install ducting aftewards to see how much cooler it made them. I never did step two...why....becasue, the deflectors, cooled the brakes well enough. I have never cooked them since....and yes, I do drive hard. (This assumes one has removed the dust shields)

The most important things here are....and in this order.....

Dust shields...gone (optional depending on which cooling you choose)

Get air on the rotors...Dali, Porsche, or some deflectors or ducting
Upgrade Pads...lots to choose from
Rotors...the stock ones will be fine until they get hairline cracks, then change them. Cryogenically treated replacements with efficient veining, and degassing, are cheaper than stock replacements. So it is a no brainer.

No need to get upgrade crazy here. Unless you jsut got more money than you need. I still run the stock calipers (front and back). With good fluid, and proper braking technique on the track, you will be fine with them.

Being fast is all about momemtum, and braking kills momentum, so keep it to a minimum, and get it done and overwith as quickly as possible!

 

[nsxtasy]

Dust shields...gone (optional depending on which cooling you choose)

Beware. The splash guards (as they are more commonly called) sit between the brakes and the ball joints. When you remove them, this exposes the ball joints to more heat, and they can eventually fail. And they're expensive to replace, since you have to replace the entire knuckle.

What our local dealer, Acura of Brookfield, sometimes does, is they cut off most of the splash guards, but leave the section between the brakes and the ball joints.

I still have the splash guards; there's a hole cut in them, and a flange welded around the hole. My brake ducts are attached to the flange.

 

[stuntman]

Being fast is all about momemtum, and braking kills momentum, so keep it to a minimum, and get it done and overwith as quickly as possible!

Yes being fast has a lot to do with momentum, but it also has a lot to do with efficiency. -Using the tires efficiently (at 100%) as well as using the brakes efficiently. Overslowing corners is will hurt your lap times and you do want to keep the momentum of the car through the corner. But after a long straight into a lower speed corner, you must be efficient with your brakes. The more efficient you are with your brakes, the later you can brake and the lower your laptime will be.

If your midcorner speed for that low speed corner is 40mph and your tire dosn't generate enough grip to go faster, and you are traveling at 130mph down the previous straight, the quicker you can slow the car down - the later you can brake and still slow the car down to your 40mph mid corner speed, the better your laptime will be. For a situation like this, braking later (at the limit of the tire's grip) to slow the car down is faster.

Granted, braking too late and or overslowing the corner will hurt your laptime, momentum is very important and this is just making your braking more efficient to your turn-in point where you then keep the car at 100% of it's grip in cornering.

 

[NSXLR8R]

True, as Stuntman says, "

being fast has a lot to do with momentum, but it also has a lot to do with efficiency. -Using the tires efficiently (at 100%) as well as using the brakes efficiently."

Specifically because these efficiency components contribute directly to momentum, or in some unfortunate cases, the lack of it.

Anyway, it may seem a bit like we are getting off subject here, but the general idea is to convey how with proper braking technique, one can drive hard, and not "require" a hardware upgrade on the NSX brakes....will the big brakes get you faster lap times.....yes, when one's driving skill reaches that level, but they are a luxury, not a requirement. AND...should not be used in lue of proper braking technique!

Smooth, firm, an get it over with.

Maximise efficiency, subseqently maximising momentum. Enjoy!

 

[stuntman]

^ I agree. First upgrade your pads, fluid, and stainless steel brake lines and that should be sufficient for most.

One other thing to keep in mind is the limiting factor of the tires. The stock tire width is relatively narrow and may be the weak link to cause longer braking distances (assuming that the brakes have proper fluid/pads and that you are using the brakes to their full capability).

So it might also be true that your braking system is now fine, but under braking, you are at the limit of your tires level of grip. This means that upgrading to bigger rotors or big brake kit WILL NOT improve your braking distances. If your brakes cannot get into ABS or lockup lap after lap, then the issue lies in your brakes. But if you can go lap after lap, threshold braking, and can easily get into ABS or lock up the tire every time, then your limiting factor is your tires and need to get wider/stickier tires.

I haveto admit that I am an advocate of improving the driver (efficiency) over equipment.

 

[Alan C.]

I think you may find that the geometry of the contact patch changes but the area doesn't change as much as you might think with larer tires. Stickier R compounds, yes, an improvement.

 

[stuntman]

I think you may find that the geometry of the contact patch changes but the area doesn't change as much as you might think with larer tires. Stickier R compounds, yes, an improvement.

Wider tires do yeild more grip (to a point) which the stock NSX tire width will greatly benefit from, so does stickier R compounds.

 

[nsxtasy]

Wider tires do yeild more grip (to a point) which the stock NSX tire width will greatly benefit from, so does stickier R compounds.

Differences in grip between tire models (due to softer compounds and more aggressive tread patterns) are nearly always far, far greater than differences due to tread width. If you're looking for better performance, concentrate first and foremost on getting the stickiest tire model you can.

 

[Ponyboy]

Wider tires do yeild more grip (to a point) which the stock NSX tire width will greatly benefit from, so does stickier R compounds.

There are a lot of caveats to that though. Wider tires do yield more grip vs. a stock tire provided both of them are the same compound and they are both in a handling situation. It has to do with the shape of the contact patch being more long width wise than length wise. The wider tire has more contact area in total (I've measured them!) but not as much as you might think (maybe 10% tops). I'm more apt to stick with nsxtasy's advice - get the stickest stock sized tire you can find.

That said, ATBE, the longer length contact or "narrower" tire will stop better than the wider tire.

 

[nsxtasy]

The wider tire has more contact area in total

Not true. The area of the contact patch depends only on the air pressure in the tires and the weight on the tire. (Read more here.)

(I've measured them!) but not as much as you might think (maybe 10% tops).

I've spoken about this with the Technical Director at the Tire Rack. He told me that they measured the size of various contact patches for tires of various sizes and widths, using the same car and the same air pressure, and found that the differences in the areas measured were less than their measurement error (which was about two percent).

 

[Ponyboy]

I'm sorry. I should have stated "according to my measurements." And I'm not making it up - the total area was greater.

The may have been some differences in the sample though. I tested the stock 225-16s Yokohamas vs. 285-18s Bridegstones at the same PSI.

Try it for yourself if you like.

 

[Ponyboy]

And before you go off the deep end with the last word:

- I understand your point and criteria involved.
- I agree that the areas are generally the same.

It just did not play out as exactly the same in my test. The wider tire had more area. And I think it's very likely that the difference in tire brands, models, etc was the difference. Still, there was a difference.

 

[nsxtasy]

I suspect that the Tire Rack's measurements were more accurate than yours. No disrespect is intended for your methodology, but I bet they rolled the car onto a pane of glass and outlined the area to measure from underneath (which is more precise than trying to trace around a tire on a piece of paper, where you can't really get all the way to the edges of the contact patch - which is the most precise way I can think of for a DIY measurement at home).