Larry Weinstein

I'm in the process of installing delrin spring plate bushings on my turbo S race car. I noticed that my spring plates do not appear to be positioned at exactly the same angle. I believe at some point the bars were removed and possibly reindexed/replaced by a previous owner.
Should I try to reindex them (it's not a big difference)or do the helper springs in the rear
compensate in setting ride height. I had the rear Bilsteins rebuilt with spherical inserts so the car needs to be cornerweighted/aligned. Do the torsion bars play any significant role in the turbo S suspension? Thanks.

Russ Murphy

The difference in angle between the two spring plates could be the result of the eccentric adjustment between the two halves of the spring plates is not equivalently set between the the two or the indexing of either end of either torsion bar is altered. I'd make sure the factory ride height eccentrics are set the same and then consider messing with the torsion bars, but aren't you installing new spring plate bushings? You'll be messing with the indexing anyway. I'd set them the same and rely on the factory eccentric and the helper springs to get the corner weights right.
Make sure you can get the car low enough with whatever torsion bar index you use. <img border="0" title="" alt="[Wink]" src="wink.gif" />

Russ Murphy

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> Do the torsion bars play any significant role in the turbo S suspension? Thanks.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">I'm not sure what you mean specifically. Yes the play a significant role. They 're the spring for the rear suspension. They also contribute to the lateral stiffness of the trailing arms by bolstering the spring plates ability to resiste deflection, something you'll have helped as well by installing the delrin spring plate bushings.

Larry Weinstein

Russ,

I know Lindsey sells a replacement rear end that eliminates the torsion bars...that's the reason I questioned how necessary the torsion bar is to the turbo s suspension. If you can adjust height using the spring perch on each side, is the torsion bar redundant? Or should the car be lowered/leveled with the torsion bar indexing and just corner weight adjustment done with the spring perches?

Larry Weinstein

Russ,

When I removed the torsion bar to install the new Delrin bushings, I marked it's position in the carrier and I maked the angle of the spring plate when assembled. That made it possible to reinstall the torsion bars in the original position when evrything was reassembled.

Russ Murphy

Larry,
The spring rate your car requires at either rear corner can be supplied by the torsion bar only,
a combination of a coil/helper spring, or solely from a coilover with the torsion bars removed (with or without the "Lindsey" (Kolkeln) rear end. In PCA club racing I beleive you must retain the torsion bars, but can use helper springs in conjunction with them. If you remove the torsion bars the bolt at the lower end of the shock will no longer be sharing bump force loads with the torsion bars, a potential problem for streetdriven cars (potholes). That's why Racer's Edge makes those super high quality standoff bolts for the shock to trailing arm juncture. There's also the lateral rigidity issue I talked about before. If you ditch the torsion bars you'll most likely want to replace the rubber trailing arm bushing with something stouter like the Racer's Edge bearing. So, yes, in conjunction with a helper spring the torsion bars are redundant, but there are other synergies involved. I'm by no means an expert, I'm regurgitating the things I've gleaned from folks like Karl @ Racer's Edge and I'm in the middle of removing the torsion bars and replacing the spring plate, the trailing arm and the torsion bar carrier bushings.

DanD

Russ pretty much nailed the rear suspension options. You need to have one of these options.

Torsion bars - Many run bigger ones up to 31mm
Torsion bars with helper coil overs shocks
Coil over shocks.

Corner balancing with just torsion bars can be achived with just rear high adjusters, (if it's not way off). Height adjustment same thing. If it's to the end of the adjustment ann it's still needs to move more, then you get to learn the wonders of torsion bar reindexing.

I went with stock torsion bars indexed real low and coil over shocks.

Clarks write up on this might help a bit.
<a href="http://www.clarks-garage.com/shop-manual/susp-06.htm" target="_blank">Clarks Garage Torsion bars doc</a>

<a href="http://members.rennlist.org/dan10101/docs/S_TORSON.doc" target="_blank">Renegade Archives doc</a>

Here's some more light reading if you're inclined.

<a href="http://members.rennlist.org/dan10101/car_math.htm" target="_blank">More bits of information.</a>

Larry Weinstein

Thanks Dan. My high school geometry is a bit rusty but I think I can follow.

I was warned installing the Delrin bushings would be a pain!