tifosiman

On my early offset car, I have S4/951S calipers mated with a custom set of rotors from Coleman ($$$). While my rotors are in good shape still, I ran acrossed something that makes me wonder if the next time I need rotors I have another option.

The 930 cars used the same diameter rotor as the S4/951S on the front (304mm). Here is a shot of one.



Based on my experience with the front hubs of 911's of that vintage, they are almost the same as the 83-86 944 (and 86 951). With that in mind, has anyone ever attempted to use a 930 front rotor with a S4/951S caliper on an 86 951? Does it work? Is it the same thickness as the S4/951S rotor (I couldn't find the specs on that).

If it works it would make brake upgrades for 86 951's a little less prohibitive due to the cost factor of the rotors.

sweanders

The 993 C2 and C4 use 304mm rotors as well and IIRC several people run them on 951's.

tifosiman

Hey Anders, how are things?

On late offset 951's I assume, correct? Do you know the rotor thickness, and also the thickness of the 930 rotor?

The only question/concern would be the way the 930 rotor mounts to the hub on the 86 cars. I have a feeling the thickness is the same, the mount would be the bigger question.

PorscheDoc

I have some brand spanking new cross drilled 930 rotors laying here if you want dimensions.

tifosiman

Of course, if it is not too much trouble! Thickness, and dimensions on the hub mount area (photos if possible too!)

Thanks a bunch~

PorscheDoc

I suppose i could slap my car on the lift tonight and see if the 930 rotors fit.

sweanders

From memory the 993 rotors are 304x32 mm. Same as on 928GT/S4.

fast951

I run the 928S4/951S calipers on the 930 with stock 930 rotors. An adapters were used to mount the calipers. Not exact application requested, but will give you an idea..

RajDatta

I think the offset and thickness are the big questions that would determine this.
Raj

PorscheDoc

Front 930 rotor measures: Inside diameter of hub is 106.9mm. Thickness of rotor itself is 31.9mm. Overall thickness of the entire rotor from inside of the rotor, to outside of the hub is 56.7mm. Worldpac lists the 930 rotors as 304x32mm. They list the 86 951 front rotor as 298x28mm. Worldpac also lists the Turbo S front rotors as 304x32mm, which is the same as the 930, but different part number. The 951S is 928.351.043.60, and listed as fitting the 32V 928 as well, but not the 930, though they are not crossdrilled like the 930's i show, so maybe that is the difference. It doesnt list the size of the 993 rotors, and unfortunetly i don't have any laying around. Its a start.....

tifosiman

Perfect, great info. I need to compare the measurements you gave to those on the hat of my 2-piece Coleman rotor. If you have a chance to do a test-fit right there and then on your 86, that of course would be the real-world knowledge that would give the definitive answer on this.

Thanks a bunch!

pete95zhn

BTW,IMHO this page contains pretty accurate info on Porsche brakes:

http://www.pelicanparts.com/MotorCity/wmv/brakes.htm

DAR951

This may not be the direction you are looking for, but I've been running the S4 calipers on my '86 with the stock 951S rotors... All that's needed is to slightly turn down (1-1.5mm at most) the outer circumference of the hub to match the 951S hub diameter and fit inside the stock rotor. That, and the proper adapters (don't know if they're different from what you already have, but (shameless plug) I'm about to sell mine) and you can use the relatively inexpensive, one piece 951S/968 rotors...

PorscheDoc

Well, i went to pull my car in tonight and put it on the lift, and wouldn't you know, out of the blue it decided it doesnt want to start. Spent most of the evening trying to troubleshoot that with no luck, so maybe tomorrow morning i will go in early and swap a rotor while i still have it on the lift. Stupid car.

tifosiman

Hey, no problem. Sorry to hear that!

There is no rush, this is just some info that would be good to know and helpful for all in the future.

Thanks again~