ghoffman

On the rear of C5's and C6's the lower rear shock is mounted to the LCA with a humongous M16 bolt. People torque this to approximately 4-5 giga ft-lbs of torque which binds up what should be a pivot. We had a set of rear Penskes destroyed by this. My personal car has the setup in the pic below and I have 2 years on this aluminum pin.


Now, for no extra cost when you by a set of Penskes from us, this will be standard and if there is any demand, I will offer it as a separate item. It is way lighter and obviously, quick release.


No shock of any brand should be constrained at either end. Some brands of aftermarket bushings allow for rotation which is a good thing. For those that have stock bushings in the rear LCA, this is for you. Either that, or just slightly torque that ridiculously oversized bolt and put a cotter pin through it or "locktite" it.
BTW, I took this pic with the camera on my Blackberry, not bad for a camera phone? The new Droid is way better than this I hear.

mgarfias

Speaking of the LCA shock bushing, who makes one? If not, you should. That thing has to move around as much as the rubber top mount.

froggy47

Rear shock absorber

Lower mounting bolt

Factory spec with stock h/w & bushing is 162 lb ft.

That's what I am using right now, not knowing any better (than GM).

I love your replacement setup, but what torque setting would you shoot for if you are still stock setup?

Second question, is this LESS a concern if you are running springs vs. coil overs?

Solofast

Some folks want to make their car a lot more like a race car and they take out flexibility that was designed into the car in some of the joints and it results in binding or loads that were never inteneded. Just becase somebody makes an aftermarket part that doesn't necessarily mean that it works like God and GM inteneded. And just because there isn't any rubber in a joint doesn't mean that the suspension will move freely and the car handle right.

Shock top mounts, and the ball joint mount that Gary makes for them are another example of this....

worldsaway

I ordered a set of Gary's sperical shock mounts. I think the rubber bushings are fine for the street, but the cars I've autoxed or tracked all did better with sphericals. It's one less compromise. The thing that makes racecars fast work, but aren't necessary for street. Unless I'm missing something, sphericals are an improvement on shock mounts.

ghoffman

No, my stock rear shocks that came on the car have evidence of severe side loads, i.e. blue shafts. One thing you could do with stock stuff, is raise the suspension to near ride height, then torque the mongo bolt. At least this way, it is starting at a neutral point. It has a smashed nut on it, so I doubt it will fall off at 20 ft-lbs, but what is the "correct" torque, who knows? When I don't like something, I just design a solution. It is so over sized, if you put the entire mass of the car on this (double shear) joint, you have only about 5-6K PSI of stress on it. The steel bolt is a grade 10.9 which is good for about 150K psi and the aluminum pin above is good for about 36K psi. I am baffled why they put in an M16 here, an M12 would be more than adequate here, the front stock "T" bar is single shear and is about 15mm.

froggy47

So what I am understanding is that with the stock setup, you crush the steel/rubber bushing on @ 162 # and the rubber twists/deflects and takes care of the necessary movement & keeps the noise/harshness to a minimum.

With other poly/delrin/full race setups you really don't need all that 162 # and you may even cause binding if you go that tight.

That right or no?

I had also thought that the axle was "located" by that connection, hence why it was so massive (the bolt). Maybe that's not the case?

Still learning.

ghoffman

So what I am understanding is that with the stock setup, you crush the steel/rubber bushing on @ 162 # and the rubber twists/deflects and takes care of the necessary movement & keeps the noise/harshness to a minimum.

With other poly/delrin/full race setups you really don't need all that 162 # and you may even cause binding if you go that tight.

That right or no?

Yes, correct on both.



I had also thought that the axle was "located" by that connection, hence why it was so massive (the bolt). Maybe that's not the case?

No, it is not like a strut, it should be free to rotate on both ends, regardless of brand or coilover or leaf.

Still learning.
As we all are!

0Randy@DRM

We decrease the bolt size and torque value on our Mono-ball setups.

Randy

froggy47

Thanks guys!