Anti roll bar sizing, hollow V solid.

[Chris Wilson]

Dunno if this is of interest, I posted it to another forum, then thought it may be of use here:

 

For the same outside diameter, a hollow bar is softer than a solid one. A hollow bar can provide the same stiffness as a solid one, with less weight, but the outside diameter has to be bigger.

 

 

Other things being equal, a hollow bar has higher stresses than a solid bar. If the bar is short, or the arms are short, in some cases the bar needs to be solid to avoid stress levels that would cause the bar to take a permanent set or fatigue prematurely. Short of this point, there is some reduction of longevity with a hollow bar. The bars on a Skyline go all the way across the car, and have long arms, so hollow bars should work fine.

 

 

To give you some idea of what diameter you'd need with a hollow bar to equal a solid bar, if you had a factory rear bar 5/8" in diameter, a ¾" O.D., .060" wall hollow bar would be about the same stiffness. A ¾" O.D., .090" wall bar would be about 30% stiffer.

 

 

If you have a 1 1/8" solid front bar, then a 1 ¼" O.D., .156" wall hollow bar, or a 1 5/16" O.D., .120" wall hollow bar, would be about the same stiffness. A 1 3/8" O.D., .120" wall bar would be about 20% stiffer.

 

 

If you buy bars by an advertised rate in lb/in at the arm end, be aware that there are two ways of expressing this rate, and not all manufacturers use the same convention. The more common method is to rate the bar like a ride torsion bar. That is, one end is moved a known linear amount and the force per inch is computed. This gives you rate in pounds per inch per end pair: the force when each end moves half an inch, meaning there's an inch difference between the two ends. Some manufacturers prefer to double this figure to get the catalogued value. This method gives you the rate in pounds per inch per end: the force when each end moves an inch, meaning there is 2" difference. This method has the advantage of being easier to equate to a change in ride spring rate. Neither method is more correct than the other, but you do need to know which method a manufacturer uses, if you want to make comparisons based on rate.

[Pete]

You really need a website to store all these gems on.

[bignum]

Good info there, is it worth changing antiroll bars for improving handling?

[spidermonkey]

Very interesting info, i changed my anti roll bar recently and it has made quite a difference - i'm still not sure if it's better or worse:search:

[spidermonkey]

By the way it's nice to see people using imperial units, far to metric normally