Geneqco

I think I'd be talking to the distributor you got the pads from.

wwinton

I tried that, they seem to think it couldn't be there pads and that there must be a problem with the car, that is why I was interested to know if many people had changed that pressure regulator, and if it makes a difference.

Geneqco

Are you using the same type of pads on the rear?

wwinton

no, I did have stock Textar's in the rear

333pg333

Well I don't know about those 'Z' pads from PFC, but I do know that the 01's and the 97's work very well in my car. Having said that, previously I had EBC Yellows and Greens and suffered sponginess and even a couple of times all the way to the floor which always gets the pupils wide open. Sounds like the front and rear pads you have are more street than track?

Geneqco

I have read that Porsche played around a little with the proportioning valve from model year to model year. According to the Workshop Manual we have a 5/18 valve whilst the one Paragon offers is 5/33. Both have a 0.46 reduction coefficient. The difference is the switchover pressure - 18 bar stock, 33 bar paragon.
In your case, assuming the pads are of good quality and not defective,
I'm just wondering if the issue may be caused by having different pads front and rear. If the front pads have substantially higher friction material than the stock rear pads, this could cause an imbalance front/rear greater than that intended by the valve.

333pg333

Sounds plausible Scott.

ninefiveone

It's not the rears. Guaranteed.

Half dozen stops from 40mph isn't close to enough to bed track pads.

You can easily run different pads front to rear and not get this problem. I've run lots of combinations without issue. Under track braking, there's so much weight transfer that it makes very little difference. Tweak rear pads and braking when you're looking for that last 2-5% of braking performance. This is not that kind of situation.

Are you getting ABS engagement? It sounds to me (others braking at 100 marker without issue) that you're not braking hard enough, braking early, and braking long. This is one of the quickest ways to pour a ton of heat into the brakes and fade them quick.

333pg333

I don't disagree with what you're saying 951, and I also think there is something not quite right mechanically, but theoretically if you had pads that were much more 'bitey' on the front isn't there a possibility of them hogging too much of the retardation and therefore drawing too much heat by virtue of their superiority? This is a late night theory which I'm not all together happy with either. Also if my memory serves me correctly this car is on pretty stock suspension which under braking will lurch forward and push more weight up front creating more heat.

ninefiveone

I hear what you're saying but it doesn't work that way (pads hogging retardation) but you're on track with the weight transfer. That's one of the reasons front brakes do almost all the work. You can increase rear braking as much as you like but long before you get substantial improvements in braking the rears will just start locking up.

If driving approach isn't the issue, then bed the pads better and go from there. If it was just happening to one corner of the car, I'd think a caliper needed rebuilidng but all four? It's not impossible but very unlikely.

I'm running quite a bit more power than stock (vitesse S3, etc) and still running the stock brakes without major issues like this. At this power level with stock brakes I'm eating expensive track pads at an alarming rate (one full set per ~2 track days at this point) but I don't get anything near the kind of rotor damage I'm seeing in the picture above.

RKD in OKC

I had front pad smoking and boiling super blue on my 88 S.

Upping the rear bias valve helped only in lightening the rear a little more for better rotation while trail braking thru corner entry. It did not help the front pad heat.

Going to slotted rotors did help bring the heat down quite a bit. Learning to brake less by scrubbing speed on turn-in helped even more.

333pg333

Lol I hear you. "Pads hogging retardation" might just get a T-shirt with that on it. Yes I'm totally with you on the front brake syndrome, it was just a late night concept. I can't see it as being the style of Wayne's braking as he would have had this issue before. Probably bed in and wrong pad + lack of cooling.

ezinternet

wwinton - in your picture of the front rotor I think I see the protective plate extending up around and behind the rotor. On my 964 I removed these with no ill effect along with other games to improve rotor cooling.

Disclaimer - I haven't had a 944 in a decade, so apply many many grains of salt.

Are people removing these when tracking a car?