V2Rocket

One solution that has been tried, to keep all the bits lined up, is to lathe down a torsion bar to like 10mm diameter which gives it a very low spring rate, but still allows it to sort of secure the spring plate in place on the splines.

Then when the car is sagging on the tiny torsion bars you have very little spring rate to work against with your coilovers.

I wouldn't worry about the body vs strains of coilovers, just think about how big a metal sleeve the upper shock bolt mounts into.

Van

We used to do that to comply with race rules that said coil over "helpers" could only be used *with* torsion bars.

But a "micro" torsion bar is a lot of work to make and offers no structural support - so you might as well avoid the headache and just remove them altogether.

V2Rocket

Doesn't the spring plate wiggle around a little bit without the bar giving it lateral support, locked on the splines?
Or do the solid bushings basically eliminate that?

Van

I've never seen a torsion bar delete car without either delrin or solid spring plate bushings...

But, realistically, over a nearly two-foot bar, it's providing minimal lateral support at best - even with rubber bushings.

Butters944

I recently picked up a torsion carrier that has custom welded arms on it attached with ball joints. I was told something like it is necessary when deleting the torsion bar for coilovers. Since it keeps all the geometry in tact I think I can get away with using stock rubber spring plate bushings with the coil overs, right?

Otto Mechanic

I suspected the coilovers controlled height when the T-bars were removed, what I was having trouble with was understanding how ride height was controlled in a car that had both coilovers and T-bars, which one controls height? I tried to say that in my first post but didn't make it clear. I think the problem is I'm talking about three different setups at the same time and I'm crossing over.

Just to be clear three setup options are:

1) Torsion bars and dampers

Ride height and spring rate are controlled by the torsion bars

2) Torsion bars and rear coilover struts

Ride height is controlled by ?
Spring rate is controlled by both the torsion bar and the helper spring

3) Coilover struts, torsion bar delete

Ride height and spring rate are controlled by the rear spring and threaded strut body.

Setup 2 requires using a simple calculation to estimate the effective spring rate of the two systems combined and that calculation can be found in the article Dimi quotes from Paragon's Knowledge Base. It's still a rough estimate and will require real life empirical tuning at a track to get it right.

What I'm trying to understand is how that system is initially set, and which component actually controls ride height. If, as I suspect, both the threaded rear strut perch and the torsion bar need to be adjusted for ride height, that system is the most labor intensive of all and may not be desirable for that reason.

Otto Mechanic

I can't answer your question about the bushings but do know Racer's Edge make solid billet aluminum bushings to replace the stock rubber bushings and they're about $40 cheaper than the OEM part from Pelican. They claim to improve handling by eliminating slop in the rear suspension at the cost of increased noise and a harsher ride, neither of which are important in a track car AFAIK.

Duetsche 9 sell a custom fabbed torsion bar carrier to be used on cars with a T-bar delete. The purpose is to add structure normally provided by the t-bar. It's recommended for all 944s that have a t-bar delete suspension. It isn't cheap and it's the only reason I'm considering keeping the t-bars if I add coilover rear struts.

Otto Mechanic

I couldn't talk you into posting pictures of it could I?

Otto Mechanic

Thanks for relaying that Spencer, it makes sense and I have a lathe. That might be just the solution I'm looking for. I wouldn't need a modified bar carrier and 99% of the spring rate would be controlled by the coilovers. With the T-bars lathed down to the point they weren't able to support the car, ride height is effectively controlled by the rear struts. Geometry is maintained by the emasculated t-bars.

It certainly competes with the Deutsche 9 solution. Maybe. I'd need cutting tools capable of working spring steel and I'd need to have the t-bars parkerized. But it would still be cheaper than having the carrier fabed in Germany, taxed on import and shipped to California.

Otto Mechanic

I like this idea, but I have another that I might try. If the splines were lathed off on one end and replaced with a bushing, the t-bar wouldn't have any control over the ride height or spring rate, it would just maintain rear geometry.

Van

Ride height is controlled by both indexing the torsion bar and adjusting the helper spring - this is why this is the "complicated" setup.


This is, again, why you don't want to "complicate" the setup if you don't have to (e.g. you're not trying to get around the "intent" of rules). You'll spend many hours of work, and spend money on tooling and finishing, just to end up effectively removing the torsion bars. Be smart, just remove the torsion bars and spend your time and money on another part of the car!

Otto Mechanic

Well, "again" may be too severe, I really didn't understand the first time

Yes, now that I'm clear on how the dual system really works I have to agree that the coilovers all by themselves solve the complications and difficulties of changing spring rate and ride height presented by torsion bars and are a superior design for that reason alone.

I'm still worried about compromising the structure of the car. I did listen to the comment about the carrier tube giving the car all the lateral strength it needs. Pardon me if I've been needlessly worried by vendors of snake oil, but I want to cover all the territory before firing the money gun...

mikey_audiogeek

+1
Mike

mikey_audiogeek

Here is the TUV certification for the H&R RSS coilover conversion (torsion bar removal) kit.

http://www.h-r.com/bin/RSS-37-827.pdf

TUV certification: http://en.wikipedia.org/wiki/Technis...wachungsverein

http://www.tuv.com/en/corporate/busi...ification.html

Cheers,
Mike

Otto Mechanic

Mike -

Meine Deutshe ist ganze quatch, es ist sehr alt, am 1976, und in Schweitz ja? Ich habe gearbited in Basle?

Danke sehr,

Scott.