Performance Friction, source and compound recommendations
 

I'm getting my 82 911 ready for some track time next week and it's been a few years...

What is your favorite source for Performance Friction pads?

Any suggestions on compound? Last time I think I was using PFC 80, but I see that there are many options... I'm looking for a track pad, and my car is suspect to brake overheating (yes, have cool brake kit and good fluid), so looking for something not overly agressive in terms of friction.

Thanks,

Jeff

I run the PF97's and have been very happy. They seem to provide very good breaking and limited amount of rotor wear. My use is primarily DE at 2750lbs with brake cooling ducts.
If you're a Nasa member you can get a 10-15% discount off their site direct from PF.

John

Thanks John, that's very helpful. I will look at their web site. I used to be a NASA member, but not for many years now...

Have you tried a more aggressive compound in the rear? I used to have a different compound in the rear to help with brake bias, but can't remember what the hell it was :)

I also like the 97 compound, got them from Porterfield.

I get my PF-97's from a local supplier. Very happy with them.

I run PFC-01s front and PFC-97s rear. I always get the pads and rotors from Mark at frozen rotors.

Which of those two compounds is the more aggressive (higher friction) compound? What was your motivation for the different compounds in terms of braking behavior?

Thx,

Jeff

I believe they both have the same peak cf, but the 01s have a bit more initial bite than the 97s, but they both have good initial bite IMHO. I Figured I'd give it a try because it's what Frozen Rotors recommended, using the 01s as a front compound and the 97s as the rear. It just feels perfect on my car with the brake setup that I run, which would be stock for a '93-'94 turbo.

Thanks!

jaydubya, I think you will want to just use 97s. I bought mine from a local supplier, but won't use them until the 22nd. In fact, I'm not sure you can get 01 for stock SC/Carrera front calipers.

Speaking of which, what calipers do you have? This is worth knowing to make a proper recommendation.

Hi Andy,

I just have the regular old SC calipers, with the stock Zimmerman rotors (and cool brake kit for the front).

Checked the parts boxes in the garage - I was previously running PFC 80 in front and PFC 83 in rear I believe.

Cheers,

Jeff

Yeah, I would go with the 97s (I did).

Andy's right. 1, they don't have the 01 compound available for your car, and 2, you'll like the 97s a lot more than 80 or 83. 97s all around will be great on your car.

I just installed PF97s for the first time in my 944S2 for the track. Though they had lots of bite and a suprisingly good pedal (firm, low effort), I got shuddering in my first session with them once they warmed up (and in subsequent sessions when hot as well). When my brakes cooled, the shuddering went away. BTW, I didn't go through any particular break in process with these pads -- I've never had a problem in the past with Porterfield R4S pads that I've run many times on the track. The rotors on my car are not new and should probably be replaced, but they have never shuddered in the past with the Porterfield R4S pads. Anyone have any ideas what happened?

if your rotors should probably be replaced... I'd look there first. a shudder under braking is usually a warped rotor. I couldn't see brand new pads causing a shudder, unless they're getting the rotors hotter than the previous pads... I've used Porterfields on my WRX and wasn't too impressed with them, maybe the PFCs are working your rotors more, even though they're pretty rotor friendly, especially the 97s.
I suppose there's some chance it's an alignment issue... and it's not so much a shudder as a shimmy in the wheel.

I'm pretty sure PFC pads are shipped "race ready" in that they shouldn't really need a true bedding in period. Still, I usually do one slow session and let them cool off before really using the pads.

It sounds like your pads weren't bedded-in properly and pad material was deposited unevenly on the rotor.

READ THIS: Bed-in precedures from Stoptech

http://stoptech.com/tech_info/wp_bedincontents.shtml

Because the PFC 97 pads come "race-ready" I only do one set of stops outlined below in the "Club Race or Full Race" section (ten partial braking events, from 60mph down to 10mph, followed immediately by three or four partial braking events, from 80mph down to 10mph). I've never had a problem with PF97s using this procedure.

Thank you, Cory and Andrew. The Stoptech articles are very interesting and informative. Sounds like I have a classic case of improperly bedded in brakes. It seems that in my case the issues is the rotors, not so much that pads, and that I likely have an uneven transfer layer on the rotors from the new pads. If they were new rotors, I'd drive them around on the street and hope to scrub off the uneven transfer layer at low temps, then go through proper bedding in to recondition the rotors. But because I should probably replace the rotors anyway, I think I'll just do that, then bed in the new brakes -- for the benefit of the rotors. I hadn't understood how important the bedding in process is for the rotors; I thought it was entirely for the pads.

Rob,
Don't get confused here... there is definitely a "bedding" in process for pads as well... it's just not as important as with rotors... sort of. We usually tell customers that on a set of street pads, you can have the pads bedded in after like 50 miles, rotors more like 200 miles. You're not really bedding in your rotors, that is for pads (and it's incredibly important for metallic, or ceramic pads), but you can't just take a brand new rotor and bring it up to 1000 degrees F it's first day on the job and expect it to last. The same is true of your pads PFCs specifically, are better about this, than say a ferodo street pad.

Whatever rotors you get, I swear by, and only run frozen rotors, but some people don't like them, I don't know why, but... anyway, regardless of the transfer layer, it's heat cycling, you have to get the rotors and pads used to heat. That's why you're supposed to brake in new pads with used rotors, and new rotors with used pads. You're not worried about improperly heat cycling both, and you can concentrate on just one.

Even on my track rotors, I drive them on the street for 200 miles barely using the brakes. Over the next 50 I gradually build up the heat, until I do one really hard braking event from like 60 down to 20. Then I get to the track and do one slow session, and let them cool off. Most guys don't do this, but my last set of cross drilled rotors lasted my 2400 race track laps, plus 5000 street miles, so I swear by that process.

Andrew,

Thanks for your suggestions.

I'm aware that there's also a "bedding in" process for pads, it's just that I figure by now my PF97 pads have been sufficiently heat cycled (one full track day) to qualify as bedded in. But if I now replace my rotors, which I plan to do, I will be focusing on heat cycling the rotors in order to establish a transfer layer on them.

What's interesting is that I ran hundreds of laps on the track over several years with Porterfield R4S pads in my car, with those same old rotors, and never had a shuddering problem, and never bothered to formally bed in the pads. During the first session with new Porterfields, they'd always give me some green fade and there was visible smoke (and noticeable smell) from the brakes as they first reached high temperatures, but once that occurred, they were stable and predictable, with no shuddering. But as I've gotten faster, I have exceeded the limits on the Porterfields and found that I was wearing them out too quickly, and I would also get some loss of effectiveness at higher temps. That's why I decided to try the PF97s.

Do you know if PF97s are particularly susceptible to this phenomenon? I've also wondered if I just drove around on the street for a while, at low brake temps, if I'd "clean off" the uneven transfer material that'a likely causing my problems. Then perhaps I could go through the proper bedding in process and achieve better results, even with these rotors.

I don't know what to think of frozen rotors. I've never tried them. The word I hear from my circle of track junkies is that there's no noticeable benefit from them, but no loss either (other than the cost). I'd also never heard that it's good to break in new pads on old rotors and new rotors on old pads. Looks like by dumb luck and default, that's exactly what I'll be doing!

Regarding your rotor break in procedure, I'm not sure what the purpose of 200 miles with little or no braking would do. Seems to me that if introducing little heat is the goal, then leaving the car parked would be sufficient! Do you disagree with the procedure listed in the Stoptech site? That's what I plan to follow at this point. I don't really want to drive 200-250 miles that I don't need to be driven. And I'd also like to avoid driving a slow session at the track just for brake bedding -- if I can bed them in on the street safely (and I think I can), I'd rather do so and get that process out of the way so I don't have to think about it on the track, when time is fleeting and precious.

Rob

Rob,
I very much disagree with most modern break in proceedures, be they for brakes or engines... lol, and I'm 22 so that should mean something. I'm just throwing out advice, don't take it as the best advice, you should always ask around, and take everything with a grain of salt. In all fairness, in many ways I'm still a Porsche newbie, but I've worked in a Porsche race shop prepping cars for 4 years, with former 962 crew chiefs, 965 can-am crew chiefs etc... and usually they're right about things like this. I've installed a lot of custom brake systems on race cars, and this is what I run on my own car, that's how much I believe in it. Seriously... the kind of longevity that I get out of my brakes is astounding, by breaking them in the way that I do. So much so that Frozen Rotors has used my car as an advertisement and sent me free stuff for it. 2400 laps on a set of cross drilleds is unheard of.

I don't understand people who don't like Frozen rotors... I think they don't break their rotors in like they're supposed to, or use horribly abbrasive pads that are incorrect for their application or something like that. When I was working at Rennsport Charleston, we noticed a 400% increase in rotor life by using them. Again, we're good about breaking in the rotors.

You have to understand that what stoptech is talking about has nothing really to do with getting your rotors prepared for the track, just bedding in the pads, those are two completely different things. You need to get the pads hot to bed them in, which as I said is very important when dealing with metallic or especially ceramic pads (you shouldn't mix the two on the same set of rotors btw), but you can't get new rotors hot. That's the point of braking in new pads on old rotors, and vice versa.

You need to brake new rotors in easily. Ok, so you don't want to drive on them for 200 miles, fair enough, but at least put like 50 miles on them, with light braking, and for gods sakes, do one slow session! Lol, ever buy a set of carbotech pads? They even say that in the instructions. I can't stress that enough. You can't take a new rotor to the track drive 10/10ths and expect it to last, it's just not going to happen. I've seen a friend of mine in an '84 carerra warp a set of brand new rotors in 1 day by doing that.

The point is to slowly work up the amount of heat your put into the rotors, and this should be a relatively slow process... IMHO, anyone who says otherwise is simply wrong. I'm sure I'll catch some crap for saying that, but I'm trying to offer you the advice that was given to me and has served me well.

Anyway, good luck... lol, sorry, I wasn't trying to lecture.

Rob, I didn't do anything special with my new 97s, though the rotors had already been broken in with other track pads. I didn't do 100% braking on the first couple of laps, but I normally don't anyway.

No problems whatsoever. I really like the 97s.

97s Good enough for pro-racing in piggy Audi S4s, and good for DE in piggy 951s as well. Good grip, long life (for a track pad), and good heat management.

Regarding shudering when hot and not when cold this makes sense based on the way brakes work.

WHen your brakes are cold the main stopping power comes from friction. The pad material working against the brake disc. Once the brakes heat up, friction is not as much of a factor. Instead the braking force comes from the molecular bonding between the pad material in the pad, and the pad material deposited into the brake disc.

If you have uneven deposition of pad material in the brake disc (caused by improper bedding among other things), then when the braking switches from friction to bonding, you will get shudder because of uneven braking force across the "length" of the stopping surface.

To combat this, burnish the brake disc with an abrasive pad (like scotchbrite) really well then seat the pads again to redeposit material evenly.

Chris,

Interesting. Do you think that I can revive these rotors? Have you had luck doing this?

I was planning to replace them anyway, just because they're very old, but now I'm sort of interested in using them to test this theory. Would Scotch Brite really be aggressive enough to get to the bottom of the (uneven) deposition of material on the rotors? I thought I'd read that even turning the rotors may not bring them back.

Maybe it's a matter of degree. It's my understanding that the uneven deposits can cause shuddering, and stick-slip-stick friction cycling causes damage to the rotors through localized overheating and formation of cementite at the locations on the rotor where friction is highest. In short: shuddering begets more shuddering. But perhaps I haven't run them long enough in this condition to cause such damage. Any thoughts on that?

Also, if I just drive it around on the street for a while, using the brakes but keeping them cool where the frictional mode is abrasion more than adherence, might I just "clean" the brake rotors through normal use? And then I could go through the bedding in process properly? Problem is, I use the car on the street once in a while, and I certainly drive it to the track. I'd hate to think that the bedding in process has to be redone every time. And how would I know when I have to re-bed the brakes? It's not likely that I can tell by looking at them or by the way they feel when I drive the car on the street.

I'd guess this is a dilemma for many people like me who track their cars once in a while and drive them to and from the track on the street. It's not a simple problem. Even changing pads at the track may not fix the problem, because the street pads may have wiped off the deposits necessary for the track pads to work properly, requiring bedding in at every event.

Ah, the life of a dual purpose car...

You certainly can revive the rotors....


Couple of ways.

1) Use an abrasive pad on a drill.... You've probably seen them in brake shops on the small air-gun used for cleaning off rust. You can do the same thing with the scotch-brite ones that will go on a drill for paint stripping.

2) have them skimmed on a brake lathe...

3) What I used to do was put on some SUPER aggressive and abrasive pads for a few laps, then switch back when this happened at the track.

The first option ends up working best... A few sessions with the uneven deposition didn't seem to hurt the discs at all, so you should be okay.

:( that is not recommended by any race shops that I know of

That's kind of a broad statement, which of the three I mentioned? Which race shops?

I'd be interested to hear your reasoning behind that statement. All three methods will successfully clean off the uneven deposition from the discs and allow for a successful re-bedding of the original pads without reducing the life of the disc appreciably.

Well, I'm specifically talking about any of the shops I've worked in, and a few others that I know well.

It has nothing to do with acceptable methods for resurfacing brake rotors... I guess it's a general policy that most people might think is just an excuse to charge a customer for a set of rotors, but the general philosophy I've always been taught is that if rotors need to be resurfaced, rotors need to be thrown away, no exceptions. It's a safety and a liability issue. I want my rotors to last as long as the next guy, in fact longer, but once they reach a point where there's any chatter, or shudder under braking, or they're wearing badly, they've had it, it's time to get new ones. It's not cheap with Big reds, but I'd prefer to live through the next DE or race.

Besides, why does he need to re-bed the pads?, or even switch them?, it's not like he's switching between Ceramic and Metallic pads, where you really can't run them with the previous pad deposits... heck, the PFC-97s are a damn good street pad anyway, they last forever, and are easy on rotors... sure they make noise, especially the rears for some reason, but you don't really need to change them out if you don't want to. Changing pads constantly is what leads to rotor problems requiring them to be resurfaced, etc... I think rob's getting scared over nothing. Put some new rotors on the car, leave the 97s in and forget about it. Drive and be happy.

Andrew,

So here's my experiences in this area...

I've had Brand New rotors experience this problem... Sometimes it just happens. Rarely with PFC-97's but often with other brands, particularly Pagids... If I were to replace them every time this happened when I was running Pagid's I'd have spent $4-500 every race weekend on rotors.

I'll NEVER use Pagid's again because of this. The instant I switched to PF97 the problems went away. I went from 3 events on a set of rotors to 2 SEASONS on a set. (20 events per season)

Burnishing the disc with a scotchbrite pad or agressive brake pad certainly doesn't take any material off the disc appreciably. So there's no safety aspect there... And taking off 2 thou with a lathe doesn't either... That's all I'm talking about. You just want to remove that bond at the very surface. It's 2% of the acceptable wear on a disc. (2mm = 80 thousandths)

I think throwing them out, especially on a dual purpose car is overkill.

I run 97's on my 78 SC.

Fronts - 0045.97.15.44
Rears - 0031.97.15.44

EXCELLENT pads, no noise, no weird bedding in ritual, just work great (stock rotors)..

Chris and Andrew,

Interesting exchange. I'm certainly willing and ready to replace the rotors, and I may do that. And I'm glad to hear, Andrew, that the 97s are likely to work fine from that point forward and that you've find they work well on the street. I assume, though, that I'll have to bed them on any new rotors I install.

But I'm intrigued that my rotors might be revivable, per Chris, and I'm interested, as an experiment, to see if that can be done. If it means taking them off to a shop with a brake lathe, that may not happen -- once there's a significant cost and bother involved, I'll lose interest. But the Scotch Brite thing may work. I have one of those Scotch Brite wheels for my die grinder and I can try it.

What concerns me, Andrew, is that per your advice, once a rotor starts shuddering, it need replacing. Is that always true? It seems that if my shuddering was caused by deposits, then that could happen to a new rotor as well as an old one, and if it happens again right away, I'll be a lot less enthusiastic about replacing them.

I understand that it's generally not a good idea to take shortcuts with brakes, and as a shop, I might not want to take on the liability for brake rotor turning or other forms of revival. But in this case, I'm curious about using my old rotors as test mules to see if Chris's theory is true. If so, it may be a valid method to use if this problem occurs with brand new rotors.

I'm still wondering if I just drive it around on the street for a while if the rotors might clean themselves.

Chris,

Some of my above post is redundant with yours. We made the same points. You just typed faster than I did.

Which Pagid pads, specifically, had the rotor deposit issues you refer to?

The idea that the rotors need to be thrown away when they start to shudder stems from the belief that the rotors are warped, and once they are warped and delvelop hot-spots they will immediately warp again when at operating temperature regardless of turning them on a lathe. This is one of those things that has been repeated several times so it is automatically believed to be true, it is very convinient for the shops that are selling you rotors.

According to Carol Smith, rotor don't warp at all, and the vibration are due to pad deposit only (article on Stoptech site). I haven't done any scientific study on it personally and since I properly bed-in my pads and rotors I don't ever really experience the vibrations either.

Assuming the vibrations are due to pad deposits there is no logical reason why turning them (a couple thousandths) or cleaning them with an abrassive set of brake pads wouldn't work, obviously if they are warped this won't do the trick. I don't really like the scotch brite idea because there is no way to control the flatness of the disc, you could just end up making the vibes worse.

I've run PF97's on the street and they are okay, in fact they're on my car now because I've got an event this weekend, you need to be aware that they aren't great for your first couple stops in the morning when cold. Also, the dust will destroy the finish on your wheels pretty quickly, so if you are concerned about that use a different pad on the street and clean your wheels well after track days.

Performance Friction makes great pads, in my opinion they are better (and cheaper) than the Pagids that many people are running. I have run PF97s and Pagid orange back to back and I prefer the PF97s. I maintain a few track cars and buy enough pads that I recently became a dealer for PF, Hawk, and Porterfield.

What is my special Pelican price for a set of PF97's for my 1993 964 C2?
:D

I am definitely not theorizing here...

For those that don't know me, I've been racing 911's for 6 years with a fair degree of success. (3 yr. running MCSCC Champion in GT-2) and do specialty racecar work. (see website below).

Anywho... I used Pagid Orange early in my 'career' and was laboring under the warped rotor delusion the whole time. I had a standing account for brake discs... Untill I did some research and figured out what the problem is. I saved many of those old discs and use them now. I've used all three methods successfully.

I'd start with the scotchbrite method, or better yet use something a bit more abrasive like the pads used in your local shop... If this doesn't work, then take a few thou off with the lathe. I'd avoid cutting them unless necessary, it does take some life off the disc. (though not much)

GaryR,

PM'd you