I'm under torsion

[Neal Colingham]

Hi, I am thinking of redoing my front suspension with Turbo tie rods and BMW brakes
I have a question about torsion bars, what are these magical things and should I replace mine with bigger and better ones ?
I just gota know !

[Dave Bell]

Neal -

I don't think there is anything "magical" about the torsion bars. Seems to me that they take up a lot less space than a spring. It does not take much increase in diameter to make a world of difference in the stiffness of the torsion bar... increase in stiffness goes something like Diameter to the 3rd or 4th power.

Best book to pick up is,

"How to make your car handle", Fred Puhn.

Ole Dave Darling turned me on to that book... it is great reading and gives you background on all the topics related to suspension and handling...I am way far from being an expert but making the car handle better is a balanced act between numerous components and settings.

Have fun,

- Dave

[Dave at Pelican Parts]

A torsion bar is simply a spring uncoiled. The bar is held at one end by the body of the car, and at the other end by the suspension arm. When the arm moves up and down, the bar gets twisted. "Torsion" simply means "twisting".

The spring rate goes up with the fourth power of the diameter of the torsion bar.

In a 914, the front torsion bars are inside the A-arms. The two "bumps" at the bottom-front of the car (the ones that scrape in steep driveways) hold the front end of the torsion bars.

--DD

[JP Noonan]

Main problem with torsion bars is that they can't be made in progressive rates that I know of. Not a big deal, unless you want a softer ride when cruising then firmer as you really push it.

Also, very rare, torsion bars break, they don't sag like coil springs.

My set up is turbo tie rods, 320i brakes, 21mm front, 165 lbs. progressive rear springs, Bilsteins F+R with adjustable perches, new ball joints, and stock roll bars...well, that's all the parts I have in my garage, only about half the stuff is installed.

If I were you, I wouldn't put in stiffer torsion bars without, stiffer (or at least new KYB's) shocks like Bilsteins or Konis (droll). Also I would put in stiffer rear springs to match or the handling will change. Too much oversteer I think.

The biggest improvement next to new shocks is a front rool bar. Then do the torsion bars/springs. IMHO

[Neal Colingham]

I have new Bilsteins on the front with a roll
bar, I have new 100 lb springs on the back
with KYB gas shocks. I use this car as a daily driver so no need to set it up for autcrossing.I just like a tight firm ride.