289 rear spring

[mloy]

Originally posted by Rick 427 Cobra


Proper gauge material! Now you really have my attention. This is one of the things that McCluskey mentioned when I called him. He was talking about going to England for springs. That's key to spring rate. Properly tapered and end treatment?
Do you have any drawings for a rear? My drawing calls out 41.5" c/c, spring " flat". 40" c/c with 4.75" c/l to bottom spring relaxed.
All leaves .219 with a taper to .156 at the ends. 7 springs total.
Alcan's price sounds good for the correct spring.

Interesting, very interesting.

While the AC Cobra Chassis manual states the 41.5" eye-to-eye dimension on the rear spring, it does not clarify whether or not it is along the spring itself or eye-to-eye across when “relaxed.” The plans I have show the 41.5” dimension eye-to-eye when relaxed and not the distance along the spring. The dimensions were supposedly taken off an original Cobra back in the seventies. I have twice thought that the dimensions shown on other items on these plans were incorrect only to be proven wrong both times. That is not to say that these dimensions shown cannot be wrong, however. The plans I have also show 7/32” spring material for the rear leafs, which is .219” in thickness. The issue comes with the front spring which has (by my plans) the main leaf at 7/32” in thickness and the rest 3/16” which is supposedly not available anymore. This stands to reason why pictures of SAI and Kirkham cars have fewer leafs shown on their front springs.

Since I have an original style front upright, I can plot the camber curve for different front spring dimensions and see what is what for that spring. I, at this time, cannot do it for the rear as I do not own the rear uprights.

I am inclined to believe that the 41.5” dimension is eye-to-eye when measured with no load on the spring (relaxed) for an original car. If someone can provide good solid tech why this is not the case, I am all ears.

Now with all this being said, a shorter spring would seem to benefit the car as I understand that negative camber was hard to come by on the original cars. How much shorter, I do not know at this time.