...so I'm putting Sierra rear suspension into my Fug4 to take the output from the mid mounted R1 engine (sounds crazy - but hey - it's a challenge!). For the rear suspension I was thinking of coilovers but can't seem to track down any that aren't car make specific. Any ideas where to look? Also - any ideas on alternative set up as coilovers look to be fiercely expensive!
Next question - does anyone know how you calculate the spring rate? The rear of the Fug will be much lighter than standard as the engine/gearbox is no longer the VW lump and it is much further forward. Must be a calculation based on the weight sitting on the rear wheels I guess.

Any help appreciated.

Paul

I've just done this on mine (see gallery)

You need to be in a position to measure the corner weights, with everything in place. Once you have the weights you will have to work out the leverage on your trailing arms (where the pick ups are for the coil overs in relation to the pivot points, in relation to the wheel hub centre. This a simple moments calculation.

coil rate (in lb's) = wheel rate x suspension leverage squared


There are no cheap coilovers, and you pay for what you get, but hopefully you will only buy them once. I've used GAZ, but Merlin Motorsport do AVON's which are also excellent quality, expect to pay £200+ for a pair + springs :ph43r:

Great stuff Tigger. Thanks.

"Wheel rate" is just the corner weight modified by the leverage factor (ie the moment calculation) yes??

Getting hung up on the jargon here.

So if in theory the coilover sat at the very end of the trailing arm and therefore the leverage factor was 1.0, then the spring rate (in lbs/in) would equal the corner weight in lbs. Is that correct or have I missed something?

Paul

...oh yes - meant to ask - what length coilovers did you use. They look quite short.

P.

You could also check out the Rally Design website (www.raldes.co.uk) and go to the online shop. They sell the GAZ dampers in a variety of lengths and with different ends (rod ends or bushes) plus a good selection of springs to suit. The direct link is
http://www.rallydesign.co.uk/product_info....roducts_id=5309

Costwise about £65 each and springs on top of that....

Yes absolutely.. you have it :D

I used a fairly standard set up in the end, the coils are rated at 275 lb's and are 9 inches long. When I spoke to Merlin Motorsport (where I bought the springs) the proven way to find the correct length is to set the (coil free) shocks up on the car and to measure the 'fitted' length between the collars, that is to say support the rear on a jack and let the car down onto its wheels until you reach the desired height. Note this length and add an inch for compression, this gives you your coil length...it works B)

Thanks chaps

P.