Brake upgrade - need help. What will be best and fit under 15" Fuchs?

[Danish Dynamite]

I am doing an ST-project based on my 1972 911S. The end result should look like this - same color - Hellgelb:



The car is beeing installed with ST-steel rear flares and ST/RSR fiber glass front flares. I have aluminum trailing arms from an SC rear and front struts with 3.5" caliper spacing front.

I am going to run original 9X15 Fuchs rear and 8X15 Fuchs front with a wheel spacer.

I sold my old brakes, so I need a complete new setup.

Whatever setup I choose, it must be possible to fit under 15 inch Fuchs, but there is room for a spacer up front - possibly up to 1"

I have bought a pair of used front 930 floting rotors with seperate hats (304X32) and a 23.81mm master cylinder.



Option 1 is to get a pair of 930 rotors 309X28 for the rear and find a complete set of 930 calipers. I know they will fit under 15" Fuchs.

Option 2 is to get a 993/928S4 caliper for the front with an adapter and use that on the 930 rotor. I would go for a 965 caliper rear and use that with the 930 rotor. The caliper needs to be machined for radial mount and installed with an adapter. The question is: Would a 15" Fuchs fit over these? Under the ST/RSR front flare, there should be room to fit a 8X15" Fuchs with a 1" spacer.

Option 3 is 964 calipers. I have a set of them on hand. They are machined like VCI does - 911 Brake Upgrades using 964/944T calipers for radial mounting. I would need adapters for them. My 930 rotors are too wide to fit in these calipers, so I would need to run 28x299 rotors from the 1986 944 Turbo front and probably 290X24 Carrera 3.2 rotors rear. The question here is the same: Would this setup fit under 15" Fuchs?

The car would be a dedicated track car but also to be driven on the street. The engine is a 3.0 liter 260HP MFI.

It seems like option 1 is the most expensive and it seems like option 2 has bigger brake pads and I guss more stopping power - at least up front. Option 3 would be the cheapest, but I am worried that I will not get the amount of stopping power I need and runing on less thick rotors. I will run brake cooling up front.


What setup would the experts find to be best?

[KTL]

Honestly, for a light car like that, I would put front Carrera brakes, SC rear brakes and call it a day

But to answer your questions:

Yes you know Option 1 will work. It'll also work your wallet BIGTIME

Option 2 will not fit under 15 in. Fuchs w/out a spacer to clear the wheel barrel. The 993 caliper is too darn big unless you use spacers. I ran a 951 16x7 Fuchs with the 993/Wilwood combo on the front of my '87 and the fitment was TIGHT. So tight that the rubber bleeder nipple caps would touch the wheel. Remember that the 951 16x7 has extra hub depth to allow for larger brakes, as that's what prompted it's creation- use of the small Brembos on the '86 951.

The 965 rear setup also needs a spacer to get clearance from the wheel barrel, similar to the front.

Option 3 is a nice one. It'll clear the fronts with a small spacer if I recall correctly. Do a search for VCI circa 2005 or 2006 and I recall we had a lengthy discussion.

The rears are a bit of a compromise with the pad overhang, despite VCI's best attempt to get the caliper down onto the rotor. Problem is the rotor used (Carrera 290x24) doesn't have enough diameter.

My opinion on the VCI setup is it's very nicely created by juggling factory components and using the necessary adapting hardware. That said, I think the VCI rears are unnecessary. You can use Carrera rears (both the caliper and the rotor) for a clean fitment in the rear. They are a better match bias-wise to the VCI front setup. I and a couple local friends have run this setup and it is in my opinion the best bang for the buck in cost and performance.

Lastly, you'll have enough stopping power with any of the above setups w/out question. Pad size is more a function of heat abatement than it is stopping power. Stopping power is determined by master cylinder size & how much pedal force you can apply, along with caliper piston sizing, the rotor size/leverage and the tires you use. My non-expert opinion is the 930 and 993/965 are a bit overkill for a light car like yours.

Incidentally all the options you mention require the 930-size 23.8mm master cylinder to be installed. The VCI/Carrera "custom" setup I mentioned can get away with the SC/Carrera 20.6mm master.

But that's somewhat irrelevant since your '72 has the master mounted in the floor. The later 20.6mm SC/Carrera master mounts up above in the trunk floor on an aluminum support in a different bolting manner. But I figured it was worth saying since the SC/Carrera master is much more commonly available master. Just takes some work to swap pedals and set up the mount in the trunk. Most people say screw that and get the 930 master that was a Mercedes truck application.

Again, i'm not an expert. Just fiddled with a number of these setups over the last 12 years.......

[Danish Dynamite]

Thanks for the reply, Kevin.

I have heard of the pad overhang when using the 964 rear calipers over the 290X24 Carrera 3.2 rotors. I am thinking this could be solved by using a set of (used) 930 309X28 rotors and have a machine shop take some of the thickness off so they became 24mm and some of the diameter too so they became 299mm. Then I guess the caliper should fit perfectly?

/Christian

[KTL]

The pad overhang can be fixed by using the Carrera rear caliper. Yeah, I know it's not a fancy Brembo aluminum caliper (much lighter than the iron Ate caliper, despite being much larger than the Ate) but the fitment and piston sizing is VERY good for track use. Rotors are cheaper too. Plus the non-drilled rotors have a bit better life span in track use

Turning down the diameter is not uncommon. It's done on front 993TT rotors for some custom installations. But I would not recommend using the 930 rotor in a reduced thickness. It starts at 28mm and min. thk. for replacement is 26mm. 24mm is WELL below that. Not to mention a perforated rotor is going to be more crack prone, and even more so when you remove all that thermal mass to make it 24mm. I would venture to guess that a 930 rotor doesn't have much wall thickness left after being cut to 24mm. This is because the air gap between inside of the rotor faces is fairly large.

[Danish Dynamite]

Thanks again, Kevin

That is well worth taking into consideration.

Do you or anybody know, if the 964 caliper in my option 3 would fit a 15" Fuchs? I know I might need a spacer, but would the diameter of a 15" wheel clear the caliper?

/Christian

[KTL]

Christian,

I did some searches in past topics I participated in and couldn't find mention of 15 in. Fuchs used with VCI small Brembo kit. I'll keep looking to see what else I can find.

[GaryR]

I know someone that is selling a full set of 930 calipers, come with rotors and pads, PM me if you want his contact info.

[mpetry]

Honestly, for a light car like that, I would put front Carrera brakes, SC rear brakes and call it a day

+1 on that. One of the nicest things about those early cars is low unsprung weight. Unsprung weight affects handling, braking, and "feel".

Properly rebuilt SC or Carrera calipers with some brake ducting for cool air should be more than sufficient for this car. Bigger brakes will dissipate heat from repeated decelerations from high speed, but they won't stop you any quicker.

Pelican Bill Verburg is the resident brake expert here - I would not try to add anything to to what he's written - while 6 piston big reds may look cool at the coffee stop, they are way overkill - in my opinion. I would avoid any setup that required adapter plates, BTW

[GaryR]

Sell those rotors/MC and go 100% bone stock new SC calipers and rotors (not drilled or slotted). SC brakes are more than adequate for a full weight SC, let alone a lightened one..

[Craig_D]

You could do what I'm doing on my SC, upgrade to front later Carrera (Wide A) calipers and rotors, with rear SC calipers/rotors. The later Carrera calipers are the same as the SC, except they are spaced slightly wider for the Carrera rotors which have wider rotors to dissipate heat better.

For a really trick set up, you could send them to Eric and PMB Motorsports to be restored with the beautiful replating, and add the lighter stainless steel pistons.

[winders]

Originally Posted by Craig_D

You could do what I'm doing on my SC, upgrade to front later Carrera (Wide A) calipers and rotors, with rear SC calipers/rotors. The later Carrera calipers are the same as the SC, except they are spaced slightly wider for the Carrera rotors which have wider rotors to dissipate heat better.

This!

All you are going to do with bigger brakes is add a lot of unnecessary unsprung weight to the car.

Scott