Shock aborber length

Can anyone advise how I work out what length of shock absober to order for the front suspension on my KVA.
The wishbones are modified, so 'standard' measurements ( if there were such things for KVA's ! ) probably won't be right.

Measurements between the top mounting bracket on the chassis, and the bottom mounting on the wishbone are:

at 3" bump - 10"
at 2" bump - 10.5"
at 1" bump - 11"

AT REST i.e. AT NORMAL RIDE HEIGHT - 11.5 "

at 1" droop - 12.5"
at 2" droop - 13"
at 3" droop - 13.5"

The easy measurment is the 'AT REST ' one, but the shock companies want to know the 'fully open and 'fully closed' lengths and my problem is that I'm not sure what the normal range of bump at droop is.

Also, what effect does the bump stop have on the measurements?

Thanks in anticipation.

Can not advise how to really determine optimum length, but for ref. I have Koni 3012 shocks,1615 BA23(front)Max Length 339, and 1621 BA22 ( rear) Max L.369. But this is on a GTD!!Hope this is of some help!

Generally you want your ride height to be at 1/3 of the shocks travel from full extension. In other words from ride height you want one third of the travel to full droop and 2/3 to full compression. The typical front coilover has about 3" travel.

So with a typical front shock, say an Aldan,

with about 3" travel and your ride height of 11.5"

you would be at 12.5" at full droop

and 9.5" at full compression.

There is no Aldan that is this length so an Aldan wouldn't be optimum. You can go in the direction of having ride height at 1/2 the shocks travel.

The AS 656 Aldan would work in this case with a 10" full bump, 13" full droop with your 11.5" ride height right in the middle.

On most GT40's I've seen the coilover shocks act as the bump stop. Look at your clearances, turn the steering both directions all the way and raise and lower through your full expected travel to make sure nothing is hitting. You can even get a piece of 1" sq thin tube and drill holes where you want ride, full bump, and full droop to bolt to the shock mounts and hold the suspension in place while your turn the wheel and check for interference.

Chris,
I had to go the custom-made route. Measure where the wheel hits the bodywork, and the suspension arm bottoms on the chassis, deduct 10mm for safety and there you have the max & min. The longer you can make the damper body, the better. The bumpstops are added after. When I had my AVO shockers made, the engineer asked whether I wanted single or double bumpstops, but these bumpstops are not in any of the calculations. They are added after all else.
Tony.

Thanks Tony
I measured the ones already on the car at ride height (13.5" ) and then went and bought what the guys on the AVO stand recommended which were 12 - 15 I think . They have huge bump stops though!

They advised 10" springs which I will be ordering form Merlin.

Chris,
You might like to try Rally Design for springs...
Working on the basis that the first 2 sets of springs are going to be wrong, cheapest is best.
Tony.