A question about torision bar selection
 

In selecting TB's, one must obviously consider a number of factors; e.g., vehicle weight, power, shocks, tires, use (street/AX/race) etc. Has anyone put together a gudeline for where to start when selecting TB's. From running a coil over setup on a Z car, I know that most racers (or street guys for that matter) have a tendency to spring cars too stiffly...so what are the "hot setups" for various cars/applications?

Oldie but goodie...from Rennlist

http://tech.rennlist.com/911/pdf/torsionbars.PDF

- Wil

yes, this is excellent information.

btw Wil,

Is it possible to update the model with a corner balance weight? This would define an effective spring rate value. I think the ratio of weight/spring rate would give a deflection value [lb /(lb/in) = in]. this would be very useful for people who have taken weight out of their car.

I did this exercise when I replaced most of my body panels with fiberglass. The excessive weight loss means the std ratio of spring rates does not fit properly now. I realize it is an almost over-simplicication but it works. I run 22/31 and have great balance despite the large difference in spring rates.

ThanksWil...I'd always wondered about how to calculate the effective spring rate. One of the reasons I posted this query was the difficulty of swapping TBs relative to changing coil springs out (both in terms of labor and expense) to tune a cars suspension...

I notice some suppliers have various levels of stiffness based on the application with no apparent consideration for the other factos (weigh, for example)...just looking for some directions in setting a car up for the track.

To answer some of these questions:

- the original text does indeed show you "effective" spring rate...that is....as seen by the wheel and suspension member that acts on the car. I't not simply a "raw" data point on "sping rate"...it ends up being "wheel rate".

I understand the issue of altering the weight of a car and having it impact the calcs. A lot depends "where" the weight was removed ( example--primarily front or rear)... that would complicate matters.

I guess I was aiming at one conclusion...that the oft-cited 21/27 pairing...or 22/28 pairing....can be improved by eeking-up the rear bar size 1-2 mm from these "norms". The 21/27 and 22/28 typically retain the built-in understeeering characteristics the lawyers built into these cars at the time.

an oversimplification....but you get the picture......

- Wil