Board logo

Suspension help
sammy - 15/9/07 at 09:51 AM

I am at the stage where I am ready to mount the brackets for the shocks, so I am looking to get some shocks.

What is the best way to work out what length dampers to get?

I assume that under normal load the bottom wishbones, both front and rear (IRS), should be horizontal.

So I was thinking that if I position a wheel so that the bottom wishbone is horizontal, then move the wheel down 1 inch (more?), and take that as being the position where the damper would be at it's maximum (open) length.

Does this sound OK for working out the maximum open length needed for the damper? How much sag is needed (front and rear) to allow for roll during cornering?

Cheers,
Sam

britishtrident - 15/9/07 at 10:21 AM

The wishbone level thing is a bit of a fallacy.
Depends on tyre height
Usually the inner wishbone pivot should be slightly higher than outer --- say 1" to 1.5"

mark chandler - 15/9/07 at 12:25 PM

I,d block the chassis at the height you want, stick on the wheels and let them rest on the floor, now measure the distance between the shock mounts.

This length is now halfway between fully opened and fully closed on whatever shock you need.

My shocks have I think 4" of travel, this is more than enough for a locost, infact I really need to fix bump stops and restrict droop.

Regards Mark

omega 24 v6 - 15/9/07 at 12:44 PM

quote:

This length is now halfway between fully opened and fully closed on whatever shock you need


Not necessarily. I believe that the fully extended shock should be the physical stop for the suspension on full droop. This is so that the ball joints on the suspension do not take the axle/ wishbone loads. In that case you need to build the front and rear suspension up and then work out what the absolute longest shock you can use is. Then fully compress the suspension and work out the size for the shortest closed unit you can use (taking into account a bump stop of usually 1 inch). In reality all builds are different but only by about 1.5 inches maximum at the front.