Baptizo

I've been doing some searching about using coilovers with the factory 25.5 mm torsion bars on my '86. I'm planning on doing some DE's but this will be a street-driven 951 so I don't need anything overly stiff for the street.

I have found a few old threads that discussed the pros and cons of keeping the TB's as well as a formula to figure out an ideal setup which I thought took into account keeping them installed. But, after going through the numbers I'm not sure if it's for keeping the TB's. I also have two different #'s for the oem TB's effective spring rate, 126 (23.5 mm) & 175 (25.5 mm), respectively.

Examples:

Setup # 1:

F 200 * .94 = 188
R 300 * .42 = 126
F-R ratio = 0.67

Setup # 2:

F 300 * .94 = 282
R 450 * .42 = 189
F-R ratio = 0.67

I'll also be using RE lower rear mounts based on recommendations in numerous threads.

If I choose to keep the stock 951 25.5 mm TB's (effective spring rate @ 175), do I go with a 100 # rear spring rate with a 250 # front spring? How do you factor in the oem TB's @ 175 #'s into the equation for the rear spring rate to get an ideal effective F-R ratio in the 0.6-0.7 range?

Or would it be more effective to delete the TB's and be done with the TB nightmare?

schip43

I'll let others deal with numbers. As far as the TB's go they are only a PIA if you screw with them! You can just go with them if you have rear coil overs and live within the limitations, which in the real world really is'nt much.

If you track the car primarily and "need" the additional range for lowering, then ditch them. Other wise just leave'em and base your calculations on them being there. ( as you seem to be doing).