Tuesday, February 01, 2005

Rear Suspension

I intend to throw either a Duratec or Rover K-series at the Spitfire at some point. I have several issues about the rear suspension. Mainly the camber change, the rear end grip is way to changeable due to fluctuating contact patch as the axle swings. The solution to this is usually to just bump the car on its arse and stiffen the dampers, so limiting the effects, through limited movement.

Also its fragile, the UJ's are part of the suspension so are always wearing out.

Anyway not liking the GT6 rotoflex either I took to copying it but making is completely tuneable. Rod-end links on all points, swinging A arm and jointed radius arms. I will run this with the spring as normal, see how much better it is, if I feel its moving about I'll add an upper radius arm, dump the spring in favour of a trackrod and run coil overs, the classic lotus 25 style.

It should be a rock solid triangular structure only movement will be the same as normal in the spring, twist, not that cross axis flexing on springs accounts for much movement. I feel the system will be a marked improvement as it offers 0 degree camber change through the suspension from static ride camber to full realistic bump. So set it with 2degrees of static negative camber it will hold that camber all the way up. You need some camber growth to match body roll inorder to maximise the contact patch at all yaw angles, so you would need to dial in some camber growth which is done by adjusting the height of the lower wishbone inner link up and down in the 4 holes....With these holes I can gain no camber, or masses of camber, or anywhere inbetween. I just need some CV driveshafts that cope with the plunge and also the angles of working, I feel UJ style twin yoke sliding shafts would moan more about being run at excessive angles.

Anyway I have done half the job, and will see whether it needs to be taken all the way with coil overs etc.

Also in need of a LSD, quaiffe or plates this is the question...

Currently the rear end runs standard Mk3 suspension which copes well with the engine but its ultimately pretty crap even in its best form. The uprights have the top hole where the spring bolts through redrilled 3/4" inch lower down as to lower the car and also gain bit more negative camber.. worthwhile mod, gives loads more rear end bite, adds stability and dependability. Does make the car lurch over bumps a touch (this is on the limit driving), only on swing spring as it makes the car skip a bit when the bump makes the swing spring, swing, and puts pressure on the wheel that didnt hit the bump...causing a slight lurch to one side, or buck a bit, the swing spring is prone to bucking on uneven surfaces but its worse with these lower holes. All in all a worthy mod though.

Spec for fitment.

Rod ended joints all round, multihole pickups
Canley Alloy uprights (ok bar the top holes are too big and need sleeves or something)
Cv driveshafts (maybe this century)
Fixed type Mk3 spring maybe swinger, is a big roll centre good?

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