question, which is better and why, hollow or solid torsion bars?
 

I need to buy new t-bars, car has 23mm and that is too big. I will be replacing w/ 21mm. I hear that the hollow ones offer better response.

Thoughts?

I think the advantage of the hollow ones is saving you weight. If you think about the torsion taking place, the center of the bar does not get 'twisted' much and hardly has an effect on the spring rate. The outer diameter material is where the torsion takes place. That is why you can hollow the bars in the first place. E.g. weltmeister sells a 22.5mm bar being equal to a solid 22mm. Half a mm more material on the outside for a huge bunch of material missing in the center!

I am curious on what others have to say about different response. As far as I am concerned a spring is a spring and if the rates are identical, their behaviour on the road should be identical.

Cheers, George

Aigel pretty much explains it, the material in the center of the bar is pretty much along for the ride, contributing little ( none in the center) to the spring rate of the bar.

Hollow bars save weight, but you pay more for them because someone has to remove the material from the center, "gun drilled" etc.. its an extra manufacturing step.

I think the only real advantage is weight savings, of course thats not only sprung weight, but also some unsprung weight, but it still amounts to weight-loss.

Waht's the weight difference?

the transient response might be better in therory.

Main advantage is weight loss (the unsprung part). I'm not an engineer and cannot explain why, but the ride quality (comfort over expansion joints, etc.) is also better with hollow torsion bars over equivalent solid ones.