Jasko

I need some help guys. I'm trying to build a RS replica for Club Racing, based on the C4 body. Have full weld in cage, seam welds so far. Conversion to C2 a few months ago.

Now trying to upgrade to RS parts at front spindle and rear control arm.
Currently running Cup brakes front, using C4 front spindle and adapters.

Can anyone tell me the difference between the C4 front spindle and the RS spindle. From the looks of it, the RS uses the same spindle as the 3.3 turbo 965 341 655 19 while the C4 part is a different number. The 3.6 turbo part is different too - 965 341 655 21. I'm assuming that the difference in spindle must be at the caliper mount support, but are there more differences as well (such as hub height likeon the GT2 EVO spindle).

Also, any difference between the rear trailing arm ? C4/2 part is 964 331 021 00 while RS part is 964 331 021 70...

Tks
Dave

Geoffrey

The difference in the rear is just bushing stiffness.

The "spindle" as you call it is the upright and the RS uses a Turbo upright which has the caliper mounts in a different location and orientation and you no longer need the adapters.

Jasko

Thanks Geoffrey - Any different between the 3.3 upright (965 341 655 19) and the 3.6 upright (965 341 655 21).

Also - I thought that I had read somewhere that the rear bushing was reoriented about 8-9 degree to account for the lower ride height in the turbos. But I can't find that reference now...

Geoffrey

I have not seen that reference before.

I don't know the difference between a 3.3 and a 3.6 turbo upright.

Bill Verburg

The 3.6t and 3.3t uprights are different, I presume because the 3.6t has the taller Big Red caliper w/ the same 322mm rotors that the mounting face is lower than on the 3.3t

Cupcar

Actually the Turbo 3.3's S4 caliper and the Turbo 3.6's Big Red caliper will bolt to either Turbo upright and work with their respective disc, the difference is in the caliper mounting surface.

Porsche came out with a technical bulletin advising against 18" wheels for the 964 chassis not so equipped. The reason given was structural failures.

Thus I have wondered if the 18" wheel equipped 3.6 Turbo upright is reinforced compared to the 3.3 Turbo/RS upright--anybody know?

This might imply that the 3.6 Turbo uprights were used on the 18" wheel equipped 1993 Carrera Cup cars.

Bill Verburg

You are right, I keep forgetting about the raised mounting bosses on the RS & 3.3t calipers

When all other possibilities are eliminated, .....

reinforcment seems the likely answer

the bolts used to hold the carrier to the strut are also different
the 3.3t uses 2x 12x1.25
the 3.6t uses 1x 14x1.5 and 1 12x1.25
the 993 uses 1x 14x1.5 and 1 12x1.5

Jasko

sounds like either turbo upright would be accurate for a 964 RS replica. Just trying to make sure that the car is properly updated . I would like to get the car into H class as a RS

38D

Just a reminder that suspension is basically free in the stock classes, so you can use basically any shock/strut.

Cupcar

I hope somebody can say what the reinforcements are, if any, in the 3.6 Turbo upright, It would be funny if it were just a 2 mm bigger hole for the larger 14 mm diameter bolt!!!

If this was the case, it also raises the question if this would be a simple modification in 3.3 cars with 12 mm bolts (although this may be an answer to a problem that does not exist since I have never heard of a 12 mm bolt breaking) ?

Jasko

Colin - I had looked over the rules a few times, and figured that while the struts and shocks and springs are free, the wheel carriers would be a required update, esp since an adaptor is required to mount the correct brake calipers. But that was just an assumption on my part, and may not be an accurate one. I sure would appreciate your, and any other scruts input on this matter. Sure would be easier (and cheaper )for me to keep the C2/4 wheel carrier, although not as historically accurate.

Of course other parts issues remain, such as the brake booster/ master cylinder difference between the C4 and the RS.

I have discussed this briefly with Donna Amico, and she is getting back to me next week.

thanks,
Dave

Geoffrey

You will want to speak with Donna Amico regarding the "updating/backdating" rules. It is not easy to EXACTLY, IN EVERY WAY, replicate a Euro RS. You'd need an RS wiring harness, seam weld the chassis in the correct spots, RS gearing in the transmission, no sunroof, etc.

38D

I'll give you my view, though you should still check with Donna.

You do need the correct turbo parts so that the calipers don't need adapters. One area I don't think you need to replicate would be the mag hubs, as they are too soft and have long since been replaced by anyone tracking the car. When I was talking about free shocks, I was meaning to say you didn't have to run a stock shock that is revalved, but would run a JRZ, JIC etc (but the turbo/RS version). As Geoffrey said, duplicate in every way is extremely difficult to do correctly. You absolutely will need the correct braking system without a doubt.

Jasko

Thanks advice guys. I'm sure it will take a while to get things going. I have a source on turbo uprights at local salvage yard.

Dave

myturbo36

I have an extra set of Turbo 3.6 uprights if anyone is interested...can also take some measurements if any needs them.