[Mountain]

Originally Posted by Mountain

...Looking at some SS MRC cars, their ride height looks to be the same as non-MRC, stock for stock. I can see the MRC front strut package being 0.20-0.25” taller just looking at pictures of the two struts side by side. GM likely compensates with a slightly shorter spring. The rears suspension uses the same upper spring insulator between MRC and non-MRC, but the lower insulator is different. Other than that there shouldn’t be anything to change ride height back there...

I'm finding that this is incorrect. It looks like I got confused. Re-checking parts catalogs, there are specific part numbers for left and right side lower insulators. I think one of the catalogs I was looking at didn't have that in the foot notes and just showed just one of the part numbers, which was 20767136, on the NMRC, and only the other part number, 23427528, on MRC. Multiple other sources are showing those two parts on NMRC and MRC, but as left and right. Unless someone can find something different.

With this in mind, along with the results of my measuring of other cars and the results of other members lowering FE4 suspension cars with springs designed for FE3 suspension SS's, and getting effectively the overall drop from a SS's FE3 standpoint, I'm going to say there is nothing in the rear suspension of MRC cars that is different. This is, of course, outside of lower height springs for FE4 equipped cars.

There is something going on up front, though, that causes MRC cars to not lower.
-It doesn't seem to be the strut's lower spring perch.
-I have to then question the top mounts between NMRC and MRC. The lower and upper spring insulators are the same part, I've noted the same exact springs between MRC and NMC on cars, and the upper seat is the same part. The top mounts are different parts.
-Or... the actual machined stop on the strut pistons are different between NMRC and MRC.