Old Mustanger

I really do not comprehend why the springs would start at a 97#/in spring rate. That is awfully light, even for a mustang. Then progress to a 274#/in rate? That is too stiff for a mustang unless it is nearing the jounce bumper, that would be OK.
It doesn't make sense to me to have so little pre-load, there just isn't any benefit that I can see. You would get into a metal to metal condition too soon, that would add road noise, limit travel and get into the stiffer rate too quickly.

I guess it depends on what the OP means by "bouncy".

He could mean that the rear of the car bounces up & down too much which would be poor shock dampening. If the shocks are adjustable he could crank them up a little.

If by "bouncy" he means that the ride is harsh and too stiff, then he can back off the shock valving if they are adjustable of go to a lighter spring rate.

Try this:
This is old-school but easily/cheaply/quickly doable. Here sand bags are $3-4 each.
Place a couple sand bags in your trunk and see what the difference is.
If you add 100# and get a better ride, that is good info. How much does it lower the rear?
If you have to add 300# or 400# before the ride is what you want, then that is good info too. How much does it lower the rear?

If we have this info we can more accurately diagnose your issue and give you better advice.
Good luck.

chris32mil

Sounds like OP wanted to lower his Shelby but not sacrifice ride quality. I noticed he said that he had passengers in the rear getting bounced around. Sounds like the progressive springs compressed and was basically sitting on the stiffer rate due to added weight in the rear, am I correct in this assumption? Especially if that kit runs so light on the "upper end" of the spring rate.

Andy13186

did you not cut the bump stops? They may need to be cut down

tr3flip

It's just how the springs are engineered to get the progressive rate Eibach wanted. No driver will ever experience the 97lb rate because I'm sure this gets compressed at static height with the weight of the car on the spring.

I would suggest the OP to give more details on what the car is actually doing. Or, call Eibach! I'm sure their engineers can help explain what the OP is experiencing.

tr3flip

The Eibach Pro Street-S coilover is a complete kit and bump stop trimming is definitely not needed or recommended.

Andy13186

I would think they would need to be cut if they lower the car more than 1 inch or so, I Took a look at my bump stops with the stock ride height and they looked to be only about 1-2 inches from hitting. Are you sure they wouldnt need to be cut? He may just be sitting on the bump stops.

tr3flip

The OP has a coilover kit that includes the spring and damper. Unless he is lowered more than 2.5" he should not need to cut the bumpstop. If anything, he should be raising his car if he is that low.

Old Mustanger

If he has the rear shocks/springs adjusted too close to the Jounce Bumpers, that would explain the ride he is explaining.
It could make a huge difference to just raise the rear by an inch, then try it.

95beaststang

I agree ,I always replace the bumpstops when I lower the car ......JMHO