Manning

Re. the harness issue. Remember two things about them (1) They signal to a cop that you are a speed freak and (2) they are not DOT approved, therefore cannot be 'legally' used on the street.

L8 APEKS

That woudn't be re-indexing. That's simply loosening the torsion bar, and relieving tension.

When you re-index, you change the position of the bar in a static state so the tension stays the same. But if the bar stays in the same place (is not re-splined), the ride heighth is adjusted by tightening (adding tension) or loosening (relieving tension) from the T-bar.

At least...that's how every other torsion bar I've seen works. If you "crank" the torsion bar to lift a vehicle, WITHOUT re-indexing the bar, the ride becomes extremely stiff because you are twisting the bar more and making the spring rate higher. Granted, I'm used to cranking them 1.5", not 0.5"...but the principle wouldn't change.

When you change the amount of twist in a torsion bar, the spring rate is progressive - not constant.

Legoland951

I think you are thinking about preloading the torsion bar and not reindexing Sean. When you reindex, all you are doing is changing the position of the splines (thus changing the ride height) and not changing the spring preload. When you reindex the torsion bars, its always in a "unsprung" position. Even if you preload a torsion bar, it will not change the effective rate of the spring ( F = K times X where F = force, K = spring constant, and X = distance travelled by the spring) When a spring (helical torsion bar) is depressed (static preloaded), the distance (X) is changed so the Force (f) required to push the spring further is increased. It does not change the effective spring rate (K), which is called the spring constant and does not change in a constant diameter torsion bar (not "progressive") regardless of how much the spring is depressed.

Damn, that brings back too much images of the old days in dynamics where we had to use multivariable calculus and integrate in 3D the instaneous torque helically throughout a non constant diameter spring. 4 hours per problem.

Geo

No.

Yes, reindexing means changing the position. Reindexing does not add or relieve tension.

The stiffness does not change. It's the same with a conventional spring.

The calculation for a torsion bar spring rate from Petersen's 4 Wheel and Off-Road.

Spring rate (pounds per inch) = [(1,120,000) x (d^4)]/[(L) x (l^2)]

L= Torsion bar length d = Torsion bar diameter
l = Lever arm length (distance from wheel centerline to torsion bar)

Nothing progressive there.

I think you're making the assumption that because as you twist the torsion bar it gets harder to twist. This is no different from loading a conventional spring. It will compress when a load is placed upon it until it reaches equilibrium. To compress it more requires more load, but that does not make it progressive.