I am looking at purchasing a set of Bistein 9100 Coilovers 14" travel for use on my 75 Series landcruiser Cab Chassis (custom 4 link front 3 link a-arm rear) How do you know the correct Spring rate in lbs and the length for the upper and lower spring? Hope someone can help.

I am know techno guru so as simple an expenation would be helpfull if possible.

Kindest Regards
all 4 fun

there's a good write up on sway-a-way's site.

http://www.swayaway.com/Suspension%20Frameset.htm

-Steve

edit: can i have a shock for pointing you in the right direction?:rolleyes: :D i want some 9100s SOOO BAD

If you follow sway aways instructions for selecting spring rate and use more than 40% of the shock travel for droop the springs will become loose on the shock at full droop and can move around. If you don't want this to happen you need to use a softer spring rate or the triple rate spring system, where a very soft 3rd spring keeps tension on everything. In my opinion if the suspension is right go softer and dial in the shocks, but lots of people end up wanting stiffer springs after they first set it up following those guidelines. Maybe this is because they just guess at the vehicle weight though.

Thanks Gordon, The truck will be used in an Australian event called the Outback Challenge. The terrain in this event varries from step desert sand dunes, 100's of klm of corrugated dirt at fairly high speed (120km ish), deep mud holes and rockcrawling dry river beds. The event also has a tyre size restiction of 36x13.
Becuase of the varying nature of the terrain and the need to do some stages at speed I decided on doing coilovers (Bilstein 9100) with a four link front plus panhard bar and a 3 link a-arm rear, what do you think of this setup for the above terrain?

That sounds like a good setup. Personally I don't like the 4 link with panhard bar because if the 4 links aren't setup equal length and parallel to each other it binds in articulation. I prefer a 3 link and panhard bar. But the 4 link can definately be made to work good. Many people here will try to talk you out of the panhard bar, in favor of a triangulated 4 link or the a arm setup you are using in the rear. I think unless you go full hydro steering you should use a panhard rod, otherwise you get some bump steer. It is not bad enough that it is intolerable on the bumps, but the problem is that you can not turn lock to lock when fully articulated. Just make sure to build the panhard equal length and parallel to the drag link.

On the springs I forgot to mention, plan on buying the tender springs twice, or buy from a vendor that will let you exchange them. Also since there is some faster bumpy stuff I would not go much softer than the sway away recomended spring rate.

Thanks Gordon for that very helpfull advice. Much appreciated