spring rates

jason lycett · 09-09-03, 05:48 PM

Can anyone suggest spring rates for a road going GT40 with a Ford 302. I have a car with a tendancy to lock the front wheels too easy, I have 350lb on the front and 475lb on the back. I think these are too much.Any suggestions?

PATGT40 · 09-09-03, 08:52 PM

I just checked out the front springs on my CAV and they are 277 lbs/in. according to a spring manufacturer. Don't know about the rear.

Eric · 09-10-03, 12:54 AM

I remember a thread about this awhile ago with alot of different people saying what they used, try the search and find it, i bet there is something there to help you. Spring rate depends on alot of stuff, shock angle, weight, weight bias being some of the major factors, plus intended use etc.

Paul Bearman · 09-10-03, 04:48 AM

Hi Eric,
I think 275 front & 350 rear is pretty standard, assuming you have standard uprights & brakes otherwise as Eric said a lot will depend on the unsprung weight etc etc.

Lee · 09-10-03, 06:12 AM

Haven't measured the rears but my fronts were 450lb. Too much roll so replaced with 500lb. With rear antiroll bar fitted now corners reasonably flat. Tried it out at Castle Combe weekend before last. Very satisfactory. [img]/ubbthreads/images/graemlins/grin.gif[/img] Also still fine to drive on the road.

Has to be said though that maybe mine are inclined at a different angle to the GTDs.

Malcolm · 09-15-03, 08:47 AM

A general rule of thumb is that to reduce roll you may be better off increasing anti roll bar stiffness and not just spring rates. I did the spring rate option by itself and some times in road use, the car will just bounce in a scary manner. I run 500 lbs rear and 450 fronts on a GTD. I plan to reduce these spring rates when I increase the anti roll bar stiffness. Having been in cars with what I consider to be the better solution for reducing roll, although not as easy as swapping springs, the ride is definately much better. On track a go kart ride quality is fine and that is where mine spends most of its time now. On the road it may leave you in a dodgy situation.

Malcolm

40 Bud · 09-16-03, 01:59 AM

It sounds to me like you have something other than a spring rate problem. The numbers you gave should be more than adequate for a road or track car. The old GTD brake set up using Granada fronts and Merkur Scorpio rears was under braked for serious driving. That said, my feeling is that the car was also overbraked in the front and underbraked at the rear. You need to correct the bias as well as the overall braking. Good luck and search the forum for more answers on changing to better brakes.