SC v Carrera Rotors Calipers

[Superman]

Let's talk about this. SC rotors are 24.5mm thick, right? Carrera rotors are 24mm? A difference of 3.5mm?

Carrera calipers are similar to SC calipers except the spacer between the halves is 3.5mm thicker on Carrera rotors? Pistons are larger?

Carrera front rotors/calipers have less heat trouble, and make a nice upgrade on an SC, generally. Right? With this upgrade, is there anything else that must/should be done?

[175K911]

SC rotors are 20.5mm
Carrera are 24.0mm

Carrera front calipers are the same as SC except for being spaced wider for the 24mm rotors, both use the same 48mm pistons.

SC rear calipers use 38mm pistons
Carrera rear calipers use 42mm pistons
Carreras have a pressure limiting valve in line with the rear brakes to reduce the pressure to the larger rear pistons under threshold braking.

[Superman]

Oops. I typed. Thanks, Ed. I am trying to also create a searchable thread with data, so your post works nicely here.

[piscator]

Thanks for posting this topic. I'm about to buy rebuilt calipers for my SC and wondering if carrera brakes might be a worthwhile upgrade. Looking forward to seeing everyone's opinions.

Robert

[cfassett]

I'll be following also. Will be needing get to rebuild the calipers on myour 77, and was wondering if anyone upgrade would be good.

[IROC]

I did this a long time ago on my car. I was experiencing a spongy pedal after DE sessions even after adding cooling, etc. The stock brakes still stopped the car adequately, but the brake pedal was unnerving. Moving to the Carrera calipers essentially solved the problem. It's not a night and day difference, but if you need just a little more thermal capacity, the Carrera brakes are nice.

I did not add any sort of proportioning valve and didn't suffer any adverse consequences.

[175K911]

Originally Posted by IROC

I did this a long time ago on my car. I was experiencing a spongy pedal after DE sessions even after adding cooling, etc. The stock brakes still stopped the car adequately, but the brake pedal was unnerving. Moving to the Carrera calipers essentially solved the problem. It's not a night and day difference, but if you need just a little more thermal capacity, the Carrera brakes are nice.

I did not add any sort of proportioning valve and didn't suffer any adverse consequences.

PCA Club Race E-Stock cars all run stock Carrera brakes, with different pads and fluid of course. Plus lots of fresh air cooling. And removal of the proportioning valve, which was probably something the Porsche attorneys made them put in. And they hold up.

I think the combination of thicker front rotors for better heat sink plus the bigger rear pistons to move some of the braking action to the rear is a nice step up in overall braking.

[Bill Verburg]

Not sure where the 20.5mm # comes from current spec for '69-83 911 front is 282x20 w/ an effective diameter of 282mm
anyhow here are the specs


here's a measure of brake stress for a single high G stop which is the cumulative interaction of weight and speed potential, time would also also affects this but that's a lot more difficult to quantify.


While it's a laudable endeavor to get the rears to do more of the work, pre '84 911s are already close to ideal unless a lot of effort is made to set the car up for more rear brake.

'84 -89 are way too much rear biased and need a very intrusive p/v, the result is less than ideal. While A/Xer's often remove the p/v to help rotate the car, this isn't a recommended path for street or track use.

BTW this has all been previously posted numerous times

[Superman]

Translate for me, Bill. Are you saying that putting Carrera calipers and rotors on an SC, without any additional changes, is a step in the right direction?

[Bill Verburg]

Originally Posted by Superman

Translate for me, Bill. Are you saying that putting Carrera calipers and rotors on an SC, without any additional changes, is a step in the right direction?

yes, as is weight reduction.

The main issue wrt to 911 brakes is the heat generated in multiple hard stops, this occurs most often during track days,

changing an '83 or earlier to '84 -89 front caliper and rotor is small step toward better thermal performance It does not affect bias or single stop performance in any meaningful way.

what you do not want to do is also change to the 3.2 Carrera rears.

Other steps to enhance thermal performance
lose weight
provide a better convective process for the fronts, 993 scoops are magic in this regard
use high temp fluid
use track pads

For street use it's highly unlikely to be necessary to do most of this

[Bob Kontak]

Originally Posted by 175K911

And removal of the proportioning valve, which was probably something the Porsche attorneys made them put in. And they hold up.

I remember reading in Frere's book (I think) that Porsche had to release the brake manufacturer from liability for the 356 brakes (possibly one of the racier street versions) because they were too powerful for the application.

[G450X]

Thanks for the advice Bill, sounds like a nice little brake boost that should suffice for spirited driving without resorting to the budget busting 930 set-up.

[Tbone1209]

Originally Posted by Bill Verburg

yes, as is weight reduction.

The main issue wrt to 911 brakes is the heat generated in multiple hard stops, this occurs most often during track days,

changing an '83 or earlier to '84 -89 front caliper and rotor is small step toward better thermal performance It does not affect bias or single stop performance in any meaningful way.

what you do not want to do is also change to the 3.2 Carrera rears.

Other steps to enhance thermal performance
lose weight
provide a better convective process for the fronts, 993 scoops are magic in this regard
use high temp fluid
use track pads

For street use it's highly unlikely to be necessary to do most of this

Bill- You lost me when you said making the change to Carrera fronts would reduce weight. Wouldn't adding the larger front Carrera calipers and rotors ADD weight? Of course thermal efficiency would increase but looking at weight alone...

[G450X]

I’m pretty sure Bill was not referring to the Carrera brakes being lighter, but that dropping the entire vehicle’s weight would lessen the braking burden and thereby increase braking efficiency.

[Bill Douglas]

It doesn't make the brakes better. It just makes them the same for longer.

[Bill Verburg]

Originally Posted by Tbone1209

Bill- You lost me when you said making the change to Carrera fronts would reduce weight. Wouldn't adding the larger front Carrera calipers and rotors ADD weight? Of course thermal efficiency would increase but looking at weight alone...

The carrera 3.2 front rotors weigh ~13% more than the previous fronts and have ~20% more volume. Both increase the ability to convert KE to heat then dissipate it while keeping temperatures at levels that don't hinder function.

To reduce the thermal stress on brakes; lighten the car, increase convective cooling, increase temperature red lines