Figuring Instant Center on an IRS ???

[4pistons]

On an IRS suspension does the forward mounting point of the center section have any effect on anti-squat? How is Instant Center calculated on an IRS?

On our DSMs the mount is bolted right through the center section itself. But on C4 Corvettes they use a long torque arm to move that forward mount up near the center of the car. There must be a good reason for it. If it was a solid axle, like a Camaro, it definitely has an effect and I know how to calculate the IC when there are control arms on a solid axle but I am unsure how the IC is calculated on an IRS.

Can anyone with suspension experience, preferably racing, give me some insight?

Rick - '91 GSX

 

[Defiant]

Crap. Robert Bently publishes a book on Sports Car Chassis and Suspension Design, but my copy's not here. Sorry.

 

[zephyr_8]

check out Carrol Smith's books. Mine are in a box, otherwise i would go read ya some of it.

 

[4pistons]

I haven't read those books. Do they go into any detail on the subject?

I have read Herb Adams Chassis Engineering from cover to cover. But he only briefly glosses over an IRS's reduced anti-squat capability but never gets into the geometry or how to maximize it.

Rick - '91 GSX

 

[wret]

How to Make Your Car Handle by Fred Puhn is a good one. He spends several pages on the subject with several detailed drawings. You will need to make or obtain an accurate sketch of your suspension and follow his instructions to map your roll center and instanaeous center.

 

[jtmcinder]

For the instantaneous center you can ignore the trailing link and just extend the upper and lower control arms until they meet. The angle of the trailing arm only plays a major role in setting the amount of anti-squat.

- Jtoby