88 Carrera rotors on a 79 SC ??

[hbkramer]

Are they interchangable?? Will they fit??

Thanks

[DW SD]

I believe so, fronts for sure, bolt-on upgrade. You would have to have Carrera calipers to go with them, since they are wider. Pads are the same. You would get a small upgrade resulting from increase in thermal mass of the larger rotor. Someone else will know about the backs.

Doug

[Vipergrün]

As far as a straight swap with Carrera rotors and SC calipers, no, won't work, the Carrera rotors are 4mm thicker... As Doug mentioned, you would have to swap calipers, either Carrera or Boxster calipers will work.

[KobaltBlau]

but Carrera calipers are easier than boxster calipers because they are the same as SC calipers except wider.

No offense to Brad but I don't understand the advantage of using the boxster calipers on Carrera 3.2 rotors. I can lock up my fronts with SC calipers and proper pads with 225 R compunds just fine.

What you're really "buying" is the added heat capacity of the thicker rotors. A better way to "fix" the hot brake problem at the track is improve your brake cooling and stick with the SC parts for less unsprung weight. I haven't tried the seine systems Ti brake shields but they are another option that doesn't increase unsprung weight.

If this is for the street only car, I believe that the stock SC setup is more than adequate.

[KobaltBlau]

Hmm, thought of a potential advantage to boxster calipers. They may be lighter than Carrera 3.2 calipers, anyone know?

still, I'd bet good $ that the boxster caliper + carrera 3.2 rotor combo is heavier than SC calipers + rotors. (the 24mm rotors are heavy compared to the SC rotors!) You just have to get enough cooling air to the brakes. Look at the PCA F and G class SC club racers.

[Vipergrün]

Andy, I agree, but with my stock SC brakes and Porterfield R4-S pads, I would get fade at the track, with the Boxter calipers and Carrera rotors and R4-S pads, I did not. No extra cooling between the two, dust shields removed in both cases. I believe the surface area of the Boxster pads are a bit larger and had a bit more grab. On my project car, we are also doing Boxster rears. No scientific data, though to prove how effective this upgrade is. However, you do get the cool "Porsche" lettering on the calipers Going from memory, I did a bog "oh wow" when holding both the Boxter and stock calipers at the same time. Do not recall weights...

[KobaltBlau]

did you have under a-arm scoops or valance inlets to rotor center hats? if not, what cooling?

[Vipergrün]

No hats, no other cooling. I have a set of 993 deflectors I hope to use with the new setup...

[Bill Verburg]

with my stock SC brakes and Porterfield R4-S pads, I would get fade at the track, with the Boxter calipers and Carrera rotors and R4-S pads, I did not

Because you have bigger rotors which can absorb more energy w/ less D T and you have pads that are designed to work at higer temps and because the pads have a better thermal barrior between the wear face and the fluid.

I believe the surface area of the Boxster pads are a bit larger and had a bit more grab.

While the Boxster pads do have a larger surface area, brake torque is independant of it. The bigger surface does distribute the heat over a larger area, which does contribute to lower operating temps and lower mechanical and thermal stress.

I have a set of 993 deflectors I hope to use with the new setup...

While the 993 deflectors are better than nothing they only cool one face of the rotor. Better is a large duct feeding the rotor eye.

[Vipergrün]

Excellent summary Bill....

[KobaltBlau]

Originally posted by bb80sc
No hats, no other cooling. I have a set of 993 deflectors I hope to use with the new setup...

I think if you had set up good cooling ducts to hats in the center of the rotor, you would have been fine with the SC brakes, and kept a lower unsprung weight.

However, the practicality of the ducts in street driving may not be adequate (i.e. if they get torn off on a parking barrier or speed bump etc).

I'm not trying to say you did something wrong, just to point out that brake cooling can "fix" this sort of problem without increasing unsprung weight, for the benefit of others considering this kind of modification.

On the other hand, if you have good brake cooling and still exceed the SC brakes, the Carrera stuff is a very affordable upgrade.

[Vipergrün]

absolutely correct, I should have started with cooling first, then upgraded parts as necessary.

[Noel]

I wonder if the Boxster calipers also transmit less heat to the fluid since they are not cast iron like the stock SC/Carrera? Any comments?

That being said, I use stock Carrera rotors and calipers.

[KobaltBlau]

Originally posted by Noel
I wonder if the Boxster calipers also transmit less heat to the fluid since they are not cast iron like the stock SC/Carrera? Any comments?

Comment: Heat will transfer from the pad to the piston pushing on it. this piston does not really touch the caliper body, so it will transfer heat to the fluid. I actually think that the boxster caliper has aluminum pistons vs the iron pistons of the 'A' caliper, so it may be worse in this respect.

On the flip side, the caliper itself may dissipate more heat that it has absorbed from the fluid because it is aluminum.

I don't have any experimental data whatsoever.

My feeling is that the added expense of the boxster calipers is not trivial vs the carrera 3.2 calipers, and the performance benefit is perhaps not proportional to the added expense. If, for example, the boxster caliper is 1/2 the weight, I might reconsider

[Bill Verburg]

Heat is mostly transfered thru the pads. All of the modern high perf pads uses some sort of thermal barrier to reduce this effect.

The aluminum calipers do have a greater surface area and will radiate heat more efficiently(especially when kept clean), but they will also conduct heat more efficiently. Neither is a major issue. You will notice that no modern street caliper is finned?

[hbkramer]

Whew !! T.M.I.
Anybody want to donate Boxter calipers for a rael Time data gathering session and of corse the subject SC would have to wear the Boxter caps indefinately
You guys are a PLETHORA of info
Tks / Rgds

[Noel]

To continue this, would there be a benefit to switching to a stainless steel piston in place of the stock pistons in the SC/Carrera calipers? Or is any benefit too small to bother. I know the correct answer is to get some even larger rotors, but I'm a cheap bastard.

[PorscheGuy79]

I am curious do SC pads work with Carrera calipers and rotors?

[hmd]

Brad,

I have boxster calipers front and rears on Carrera rotors, with a twin MC and a balance bar.

No matter how front bias I set the bar there is still a possibility of locking up the rears. I don't think using the boxters calipers all round is a good idea, it is too rear bias. You would be better off using the rear carrera setup.

IMO using Boxster front calipers is a step up BUT not very cost effective you may as well go with something bigger like 993 calipers for not much more money.

[KobaltBlau]

Originally posted by PorscheGuy79
I am curious do SC pads work with Carrera calipers and rotors?

Yep. at least some of the carreras have a pad wear sensor, but it doesn't affect pad compatibility (except of course you can't use the wear sensor on SC pads). The wear sensor is useless for those of us who check there brakes once in a while.

Originally posted by Noel
To continue this, would there be a benefit to switching to a stainless steel piston in place of the stock pistons in the SC/Carrera calipers? Or is any benefit too small to bother. I know the correct answer is to get some even larger rotors, but I'm a cheap bastard.

I don't think that would be an advantage. The material to use here would be 6AL-4V titanium for the pistons. It seems like it would be pretty easy to make up some pistons for 'A' calipers on a mill and lathe. No doubt the seine titanium shims would be cheaper, but I would think full titanium pistons would be more effective.