2.8 RSR spring question
 

I'm researching the spring size and rate for the auxiliary springs fitted to the 2.8 RSR.

Does anyone 1) know the answer or 2) know where I might be able to find the answer?

I've used John Starkey's R to RSR book to get me this far, but it doesn't go into quite enough detail about rates and dimensions.

Weren't some of them pure bar cars, and some coil only? I'd like to know a bit about this, too. time to dig in the books.

Looking in Barth's "The Porsche Book", it was similarly vague. I did note in the section on the RSR 3.0's that it said "Auxiliary coil springs were available for racing, there being a choice of steel or titanium springs, the latter costing just DM 1,000 each. When titanium springs were fitted, they went with light allow dampers".

This leads me to believe that there was no 1 spring rate specified, but that it was assumed that they were changed based on the track and condition. I'd start with calculating the spring rate of the spec'd 26 mm rear T-bars, and then add a coil spring of the rate needed to get the total wheel rate that you want. Note that you'll most likely need to have your shocks valved to the combined wheel rate rather then just the stock setting.

Great info John.

I'm so new at this, I don't even know what wheel rate to start with, which is why I'm trying to find a generic baseline from which to experiment.

Here's a bit of info; I have a 2.8 RSR parts list for the first cars, dated Feb 1973. It lists 19 front and 26 rear torsion bars, no coil springs. I've seen a set of coils for AJ's RSR strut they are 450# rear and 300#front, I assume for use without any bars. I've been told that the size of the t bars was reduced on the coil cars, but that the coils were primarily for easy height adjustment without affecting other factors as much. Here are three good sources for you.

James Cox coxmotorsports4u@aol.com Kansas City

Dave Banazak dart auto Colorado n www.dartauto.com

Steve Kemp Mayo performance Dallas

David,

You are the man! Great info...

Gunnar racing restored a 2.8 RSR, and their pictures showed coil springs, which is what really piqued my interest.

Thanks again.

I've read that the reason for this was to exploit a loophole in the raicng rules -- the coilovers counted only as auxillary springs and wer thus allowable.

Today one would go with pure coilovers.

That's exactly how they are described in John Starkey's book - auxiliary springs.

I'm trying to recreate the feel of driving one with torsion bars and all. Eventually I may go to pure coilovers, but it will depend on which series I eventually race (which will be a while, mind you).