B6/HR spring refresh. Missing bump stops and bellows on my 964. Top hat question too.

[jibmaster1]

Hello. I am tackling some suspension refresh stuff on my 90' C4. I am throwing on some B6/HR springs. I have a low mileage set of B6's/HR springs which I am using for the fronts, and new B6/HR springs for the rears. I notice there are no bump stops or bellows on both the used set I have, AND none on the factory Boge/Springs still on my car. I do see bellows/bumps listed in the PET schematic. Should I buy new bumps and bellows all four corners or leave out? Also, I purchased the Rennline rear top hats/strut bearings for these new B6's. However, the HR springs appear to need a upper spring seat adapter to work--I see the Elephant Racing ones for stock shocks which I believe would work. Has anyone here done this set up? Rennline didn't seem to be of help when I reached out.
My thinking is buying ER upper spring seat kit and install below these upper top mounts.
Thanks for any advice in advance.

[Cobalt]

The B6/H&R should work with the factory top hat and should use the bellows and bump stops.

Similar setup using all factory parts but the H&% Bilstein HD (similar to the B6)



What year is your car as you know the rear shock and top hat design changed in IIRC 91.



Later rear shock left earlier to the right. Ignore the MCS Stock top hats and bellows should work.

[jibmaster1]

Thanks Cobalt for that info. So I figured it out: Rennline rear upper top hats only work with KW v3's, or Pss10/9's and require a 62mm upper spring seat adapter (due to the smaller diameter spring on these type of coilovers). Factory springs do not work. However, I'm using a HR Sport springs/B6 set which have stock sized coils. You can only use either factory top hats, or ones from Elephant Racing who carries their own version of this same top hat--but offers an optional stock spring seat adapter for about $200. I found a used set of ER top hats lightly used which essentially paid for the new spring seats I needed. It should handle nicely when all said and done. I hope RL can update their description commenting their product does not work with stock sized coils.

[Cobalt]

I don't understand if you are using the B6 H&R setup why would you not just use the stock parts? adding monoballs to these is pointless and will only make the ride more harsh. I would stay away from them unless you want a very precise handling car added negative camber and using a more advanced shock spring setup.

I run MCS 2WNR shock as shown above with 2.25" dia springs. Full ERP/Tarrett top hats and associated parts. (BTW these parts are all knock offs of the factory motorsports parts with some changes) A shorter stiff 400/500 pound spring with 225 tenders. This is not for most drivers but handles as well as a 964 can.

I am assuming you have these?https://www.rennline.com/rennline-rear-monoball-strut-mount-sealed-sku-sb69-74/

I wouldn't bother and stick with your factory parts. The H&R's will work fine with them.

If you are talking this part?
https://www.rennline.com/rennline-rear-monoball-strut-mount-sealed-sku-sb69-74/

This is a copy of the factory RS rear top hat. This is similar to what is used on the back of the 3.6RS. I just installed these on a US spec cup car. The spring dia should be the same as the stock units and H&R should be as well. The only reason they won't work is the RS springs are cut flat vs round at the ends so the factory parts will be needed for H&R.

RS springs vs stock. H&R should be similar.

[Cobalt]

I figured i would add this.

Standard style shock with H&R style springs in same Dia using factory perch's

[Ralph3.]

Don’t B6’s in front have internal bump stops?

[jibmaster1]

Originally Posted by Cobalt

I figured i would add this.

Standard style shock with H&R style springs in same Dia using factory perch's

Cobalt. Appreciate the info. My car is a 90 c4 btw. In retrospect I should have just purchased new factory rubber top mounts. I bought the Rennline rear monoballs last year and can't use them with my HR Springs. I now have a set of the ER rear shock mounts with the spherical bearings and their spring seat adapters which allows you to use factory springs or these HR springs I have. (Pic Above). My earlier style factory shock mounts were toast and decided to go this route. I was going to likely set ride height at RS +10, get a more street performance alignment done and hope the ride is not overly stiff. I fixed some leaky oil hoses/tank hose leaks today and pulled the rear shocks out. Waiting for some bump stops and bellows as I pull stuff off the car.