Springs

[Egoracing]

spring height does not matter on a coilover. attachment point to chassis does not change.

Correct, the chassis only knows the spring location by its contact point to the chassis. On a coil over that is the bolt thru the heim, on a jack bolt it is the plate location where is contacts the spring.

[drtrkr244]

spring height does not matter on a coilover. attachment point to chassis does not change.

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

[joeltjen]

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

take your car out and put the rr coilover on upside down and run it.......see if you notice any difference ( this should change your spring height by quite a bit) now take and lower both mounting holes for your coilover by 2 or 3 inches and try it again..... tell me which one make a BIG change in handleing. sometimes a book will tell you one thing but your butt will tell you otherwise!


i'm not sayimg rocket is wrong because i haven't seen the whole program you are talking about, but i will say about 3/4 of the books i've read on calculating effective rear wheel spring rate on a swing arm car are wrong

[MasterSbilt_Racer]

When computing rear roll center/angle, you have to measure from the ground to the top of the coilover nut. If you change those with different spring heights, obviously your final calcs. will be different.

From real world experience, this is wrong. From a physics standpoint, it makes no sense either. The bolt through the bearing end is the pivot point for that coilover. The coilover unit is one compressible link. It doesn't matter if the compression takes place uniformly or all at one end.

What are you doing with the j bar or panhard bar? I have seen conflicting calculations with it. I don't think roll center calcs are really all that useful for the rear of live axle vehicles.

[dualdj1]

What are you doing with the j bar or panhard bar? I have seen conflicting calculations with it. I don't think roll center calcs are really all that useful for the rear of live axle vehicles.

Yeah, after trying to hash that out before, I tend to agree. they can get you a rough idea, but testing gives you much better information.