Torsion Bars
 

I have been sorting out my new car and I have a torsion bar question. The rear is a little soft but I don't know why. I have Koni adjustables in the front with 350 lb springs and a 26.8mm sway bar. In the rear I have Bilstein HD, an 18mm sway bar and what I guess is a stock torsion bar for an 86 turbo. I figure I need a bigger torsion bar (corrected) and was wondering if a 31mm would be too big. I want to buy used and there is a pair of 31 for sale. If possible I'm looking for a neutral to understeer feel because I'm new to rear wheel drive and I don't want to spin the rear in a corner.

Thanks!

Ryan, I'm assuming that you're talking about 31mm hollow torsion bars (the springs) rather than sway bars. If you're looking at hollow bars, note that the "31mm" size they claim is usually their effective rate -- if you were to measure that bar in the middle, it would probably be a millimeter or two thicker than that. If not, then stamped somewhere on the bar will either be a model number, or its effective spring rate, since the effective rate is different when the bar is hollow.

Your setup right now should have plenty of understeer.

I think you are confusing the sways with the torsion bars in the rear. The torsion bars come in 31mm hollow or 30mm solid. That would be the correct torsion bar to use with you front spring rate if you want to get to neutral handling.

Yes I meant to say torsion bar. I have too much understeer right now and the rear sags a bit during excelaration and I want to balance the car out. The torsion bars that are for sale are the equivilant of 31 solids. I don't have the budget to go to coil overs so a pair of used torsion bars would do the trick for now.

Hi Ryan,

I think your on the right track here, your stock T-Bars are WAY too small to work with 350lbs front springs. The factory torsion bars would be 23.5 mm, and by checking the chart below = 126 lbs/in. This is why your car would have huge understreer. Again, by checking the chart below, you should use a bar with close to the front springs rate, a 30 or 31mm T bar. Note this is valid only for solid T bars, hollow ones need the manufactures specs to see their spring rate.

Diameter - Spring Rate (lbs./in)
22.0 - 97
22.5 - 106
23.0 - 116
23.5 - 126
24.0 - 137
24.5 - 149
25.0 - 161
25.5 - 175
26.0 - 189
27.0 - 220
28.0 - 254
29.0 - 292
30.0 - 335
31.0 - 382
32.0 - 434
33.0 - 490

I've just done this, 250 lbs on the front and new 28mm t bars in the rear. Now just waiting for the snow to disappear to see how the car works.

cheers,
Gord.

I sent an email to Christian to see what the pricing is on the torsion bars. Ideal would be 30mm, but if the price is right for the 31mm I'll go for those. I still have a couple months of snow to work on the car.

I run 350 lb springs up front and 30mm solid bar in the back. You could probably go to 400's up front if you used the 31mm, but your tire selection would also come into play

I've got some torsion bars for sale...Went coilovers in rear...call me

Do you have to reindex the rear suspension if you replace the torsion bars?

Yes because you have to remove the old bars.