Brake Pads

[quiksilver55]

Hey guys, I just wanted to share my experience so far with my mildly upgraded brake system and look for advice.

I'm currently running:
- Stock ('91) calipers
- Hawk HP Plus pads
- Powerslot rotors
- Downforce front brake air deflectors
- Stainless steel brake lines
- Motul RBF 600 fluid
- Front splash-guards removed

This setup has been a significant upgrade to stock, but not perfect.

During my last track event, I noticed significant feedback from the front brakes. I spoke with Stoptech and Hawk and they both said I was likely feeling uneven pad deposits on the rotors, most likely caused by overheating. The HP Plus pads are described as perfect for street AND track use, not requiring a change in between. Hawk said the pads are designed to operate 100F-800F, and that the DTC 30 pads are likely a better match since they can handle 100F-1200F. I do not have temperature indicating paint, so I'm unsure what temps are being reached, but I am surprised the HP Plus pads aren't living up to their description.

Until I have more info, they recommended taking 120 grit sandpaper to the rotors and pads to remove any deposits and glazing, re-bed the brakes, and see where we're at after that. If the problem returns, I may switch to the DTC 30 pads up front (not available for rears).

I mostly drive the car at Nola Motorsports Park in New Orleans, but do occasionally take it for a Sunday drive, so I'm not looking for a track-only solution. Without taking the big step up into BBK territory, I'd like to make the most of my current setup. So, any recommendations? I've never sanded rotors or pads before, anything I should do or avoid doing?

 

[docjohn]

I've used aluminum oxide sandpaper with variable results....I would try thier suggestion,plus knowledge is power,so invest in a pyrometer so you can check your own tire and rotor temps.

 

[quiksilver55]

Did you use the sandpaper by hand, rotary tool or block? I'll be headed to Lowes to pick some up, but want to ensure I have the proper tools for the job.

 

[docjohn]

took my wheels off and just rubbed hard as hell.......now i'm nearly blind,and have to routinely shave my palms....:redface:

 

[quiksilver55]

I think you might have done it wrong, then. Did your instructions read as follows: 1. Remove wheels 2. Remove pants.....

Thanks doc. Anybody have any experience with a similar setup or use the DTC 30 pads?

 

[nsxtasy]

I'm not sure what you mean when you say there was significant "feedback" from the brakes. Vibration? Noise? Feel? Please describe what you mean.

That's almost exactly the setup I was using, with many many MANY track events on it. I used to have vibration problems until I learned how to bed my brakes properly, using the instructions on Stoptech's website, before I ever took them out on the track. (The key thing to make sure of is to get the brakes REALLY HOT when you're bedding them, and then to not touch the brakes all the way home from that point so the layer you put on the rotors doesn't get scraped off, and has a chance to cool down overnight. I used to bed them late at night to ensure that I could get home without using my brakes.) Once I did that, I didn't have any problems whatsoever with vibrations. (If you do, though, you can go through the whole bedding process all over again.) I never had to sand my rotors.

Oh, and I think their comment about the uneven deposits being due to overheating misses the mark. The uneven deposits happen because of inadequate bedding, rather than overheating.

One more thing, it's common for those with a fairly low level of track experience to use the brakes more than they need to. With experience, you learn how to use less braking, over a shorter distance, and carry more speed through the turns.

 

[quiksilver55]

Nsxtasy, the feedback was felt in the pedal and the steering wheel as a vibration.

Although it was my first time doing so, I did follow the bedding instructions on Stoptech's site, but I could have easily done a piss-poor job at it (I'm definitely not perfect).

Lastly, the track has three places where pretty heavy braking is being applied: 1. At the end of the 1/4 mile front straight, from 125 to 60 for a 80 degree right hander; 2. Approaching turn 3, from 100 to 40 for a left hairpin double apex; and lastly at the back straight "bus stop", from about 110 to 40 for a 90 degree right hander.

I'm definitely still working on my technique and setup, but I've taken a few laps with track instructors who have dialed in my times to within a second of consistency. Without a doubt, there's still lots of room for improvement.

 

[g3driver]

I have the same set up and no problems with over 15 track days a year. I noticed vibration after one event then after a hard session went away. Good luck.

 

[nsxtasy]

Thanks.

My guess is that the most likely culprit is the bedding. When done properly, in advance of the track event, it really does prevent vibration on the track. Note that when you're bedding the brakes, if you have the windows open, you should smell them pretty strongly (after doing those really HARD stops). And as I mentioned, absolutely do not touch the brakes after that (which requires some tricky driving - I have some stoplights on the way home from my bedding course and I have to time them so I don't have to stop for a red light).

Also keep in mind that you can bed the brakes again, using the same procedure. So if you experienced some vibration this past time at the track, I'd recommend re-bedding them thoroughly before your next track event, then seeing if that works.

 

[quiksilver55]

OK guys, thanks for all the input. I did quite a bit of research on burnishing/bed-in procedures and found that Hawk's instructions fell short of most technical articles and videos I've reviewed. The best video I found is linked here. Tire Rack and various other websites have great write ups on the science behind burnishing.

Hawk's instructions called for 6-10 brake applications from 35mph followed by 2-3 from 40-45mph, then a 15 minute cool down. That's it. I don't think that process provided the necessary transfer layer the first time around, and not knowing any better, I didn't repeat the process or know what a properly bed-in rotor should look like.

I sanded the front pads and rotors last night, hopefully to remove any high spots, and will be re-bedding the pads and rotors this morning prior to an afternoon track session. I'll provide some feedback afterwards.

 

[nsxtasy]

OK guys, thanks for all the input. I did quite a bit of research on burnishing/bed-in procedures and found that Hawk's instructions fell short of most technical articles and videos I've reviewed. The best video I found is linked here. Tire Rack and various other websites have great write ups on the science behind burnishing.

Hawk's instructions called for 6-10 brake applications from 35mph followed by 2-3 from 40-45mph, then a 15 minute cool down. That's it. I don't think that process provided the necessary transfer layer the first time around, and not knowing any better, I didn't repeat the process or know what a properly bed-in rotor should look like.

Yeah, that's not really enough to get them really really hot, which is what you need to happen. Stoptech recommends ten hard 60 to 10 mph stops, and you can even do a few more than that. Again, smelling the pads is your tip-off that this is working. Stoptech's technical white papers are pretty good:

• The "Warped" Brake Disc and Other Myths of the Braking System
• Pad and Rotor Bed-In Theory, Definitions and Procedures
• Removal of Uneven Pad Deposits From Rotors Using Aggressive Friction Compounds

 

[quiksilver55]

Alright guys, looks like the bed-in process worked. I shaved almost 3 seconds off my personal best time and was able to push harder in the straight knowing I would have greater breaking power. Granted, the air temp was low, likely adding a little giddy-up, but keeping the track temps low as well (so those might have countered each other).

I did notice the even distribution of friction material became less uniform on the rotor by the end of the day, with a little bit of vibration evident. I'm assuming I'll need to repeat the bed-in process again?

By the way, I did use a non-contact IR temp sensor. The sensor maxes out at 600F, so the temp was off-scale immediately after the bedding process. Warm-down laps probably threw off my actual temps on the track, but they were consistently around 400F when I pulled into the pits. Not sure how to get accurate temps I'm actually reaching during lapping other than using rotor temp paint. Ideas?

- - - Updated - - -

Here's a video, taken with Harry's Lap Timer, of my best lap of the day. This was one of the last laps, so the vibes had developed again. You'll notice the brake vibration pretty clearly in the hard braking areas. Keep in mind the phone is held by a RAM mount with 2 pivots, so the vibes will look worse than they actually felt.

Strangely enough, I had the whole track to myself today. There were a couple of puddles from rain earlier in the day, but a dry track otherwise. I'm sure I could have eeked out just a little more time if I hadn't worked around them.

 

[nsxtasy]

I did notice the even distribution of friction material became less uniform on the rotor by the end of the day, with a little bit of vibration evident. I'm assuming I'll need to repeat the bed-in process again?

Yes, repeating the process before your next event would be a good idea.

Also, inspect your rotors for cracks. Cracks start as "spider web" type hazing, and then start to get bigger. They open up when the rotors are cool, fill in as the rotors expand when hot on the track, so check them when they're cool. I'd check them before every track session. When I saw cracks - typically in a radial direction - as long as 1/2", ones I could feel with the edge of my fingernail (when cool, of course), I ended my track day and replaced the rotors. This happened after anywhere from 600 to 1400 actual track miles, so figure 4-9 track events with an average of 150 miles apiece. So you can expect to replace the rotors on a regular basis.

Of course, we are talking only about front rotors. I never had any issues whatsoever with heat in the rear rotors.

As for the rotor temperatures, I never bothered measuring them. I never saw any significant benefit in having that information.

 

[quiksilver55]

nsxtasy, where are you being quoted 150 apiece? I ordered my rotors from autoanything.com and they have 'em for $61/front and $58/rear. They're always running some sort of 15% off deal too, with free shipping (direct from centric parts), it's pretty unbeatable. All told, should be just over $100 to replace both fronts if that's what it takes.

Not sure what year nsx you're in, since I know the 97+ rotors are bigger and more expensive.

 

[nsxtasy]

nsxtasy, where are you being quoted 150 apiece?

Huh? Oh wait, it sounds like you're referring to this part:

When I saw cracks - typically in a radial direction - as long as 1/2", ones I could feel with the edge of my fingernail (when cool, of course), I ended my track day and replaced the rotors. This happened after anywhere from 600 to 1400 actual track miles, so figure 4-9 track events with an average of 150 apiece.

That number (150) refers to the typical number of track miles per event, not the price of the rotors. I'll go back and edit to make it clearer.

 

[quiksilver55]

Oh good, I was afraid somebody was robbing you blind.

I ended up having a long talk with the guys at Stoptech today and decided to order another set of front Powerslot rotors (cryo treated this time) and a set of their performance street pads. Despite being called "street pads" they can operate up to 1400F, which is well above the HP Plus pads, so we'll see how they do.

I'll keep running the current pads and rotors in the back and test the new pads/rotors together when they arrive. Until then, I'll keep the fronts as they are and try to keep from thermally shocking them as much.

Thanks for the advice, I keep on learning. Any good recommendations on places to learn suspension setup (KW V3) and tire pressures?

 

[docjohn]

does the kw allow both bump and rebound adjustment? btw I used post number 12000 .....I need a 12 step program..

 

[nsxtasy]

Thanks for the advice, I keep on learning. Any good recommendations on places to learn suspension setup (KW V3) and tire pressures?

Don't know about suspension setup, sorry. For tire pressures, are you using R compound tires? Most R comps specify a target pressure measured when hot, and you can find it on the tire manufacturer's website or the Tire Rack website. When I was using street tires (the OEM tires), I usually used the recommended 33F/40R, measured cold. You could start there and then adjust up or down depending on what the car is doing.

 

[g3driver]

for dunlop star spec I use 33 to 35 HOT all the way around. I found 40 to be way overinflated and the car will push and get less grip and temperature. As far as KW settings I used the settings billy recommended and they work out great for me.

 

[chrisfast]

a set of their performance street pads. Despite being called "street pads" they can operate up to 1400F, which is well above the HP Plus pads, so we'll see how they do.

You were able to find Stoptech pads for all for corners with oem rotors and calipers? I can only find fronts. Where did you find the pads if you don't mind sharing? Thanks!

 

[quiksilver55]

Doc, the V3's allow for low speed rebound and compression adjustment, while the high speed settings are fixed. I haven't messed with the factory setting (tuned at/for nurburgring). More info here.

nsxtasty, I'm currently running the Falken RT615K tires in stock '02-'05 wheel fitment (5mm spacers up front to clear the '91 brakes. They were recommended to me by a guy at the track as an inexpensive replacement to my previous Dunlop Z1 Star Specs. The Falkens don't tend to get greasy when hot like I noticed the Dunlops doing. So far, I'm pretty happy with them. Somehow, they're not even unidirectional, so I could swap from left to right if I'm wearing one side faster.

g3driver, I've been running 32/35 hot and still playing with optimal temps. Could you post the KW V3 setting billy recommended?

chrisfast, I don't think Stoptech makes a rear pad for the stock nsx brakes. I'm replacing the fronts only since they tend to carry considerably more heat. I'll continue to use the Hawk HP Plus pads in the rear until they wear out, then might switch to the Hawk DTC 30 pads, which can handle 1200F vs 800F on HP+.

 

[docjohn]

Is your local track smooth?

 

[quiksilver55]

Yes, it was just finished last year, so it's as smooth as a baby's bottom.

 

[docjohn]

ok...try getting Billy's settings and time some laps,then if its dry try incrementaly increasing front rebound without changing anything else,and see what happens.

 

[quiksilver55]

Can anybody point me to Billy or his settings?