Allowed Rear Upper Shock Mount

#1

I’m very new here, in the early stages of building up a SpecE30, and I’m looking for a clarification. The only reference I see to the rear upper shock mounting in the rules is:

9.3.8.12. Solid rear upper shock mounts are permitted.

Can someone tell me exactly what that means? Maybe a few examples of what’s permitted? It would seem that OEM would be allowed, and I would think that polyurethane is allowed by 9.3.8.8 (Suspension bushing material replacement is permitted). Are spherical bearings allowed? For example Turner Motorsports part# TSU9906SM1 ? I might consider it solid since there’s no flexibility built-in, but due to the bearing, it’s not exactly solid either…

Thanks!

#2

Don’t get distracted by the bushing material paragraph when it comes to upper shock mounts. The key is solid shock mounts are ok, and also highly desireable.

#3

I’m not sure that “solid” means “spherical bearing”. I may be wrong and I know that solid bushings are allowed except for motor and transmission mounts but if solid=spherical I’m going to start to develop my spherical bearing trailing arm bushings.

#4

How could you mount solid the shocks, the angle change when the suspension travel, no? :unsure:

#5

There was a thread on this a year or two ago. In order to get more information I started threads at bf.c and e30tech. The guys that have done this sort of thing said it can’t be done w/o modifying the trailing arm and/or subframe. I don’t know any of this first-hand mind you, but apparently the trailing arm gets modified in order to attach the spherical bearing and the subframe’s ears gets modified to handle the additional stresses associated with the non-compliant bushing.

We’re already modifying the subframe ears so maybe that’s not much of a cultural stretch, but all the pics I saw of trailing arms had them pretty seriously modified.

That thread was really about keeping one’s rear alignment because a couple of us were having a problem with our alignment settings changing. There were interesting discussions of what causes stresses big enough that rtabs move in undesirable ways. The theory that won had to do with our rear springs that are almost fully compressed. We found out why the springs are designed that way and what might be a better spring solution for us.

http://www.spece30.com/forum/10-steering-and-suspension/58378-rtab-bushing-that-wont-stay-put

#6

I think there is a difference between mounts and bushings. I take the rule to mean that you can do anything with the shock mounts spherical bearings included. The rules don’t allow for modifying the trailing arms.

Whatever you get needs to be heavy duty. I think the only performance difference between the different types is that broken ones suck. I’ve been using bilstien sport for 11 years. First I got replacements then the hd convertable ones and I’ve been using the billet/poly IE mounts ever since.