Rear Suspension Brace Upgrade

[Sky Hi]

Apparently there is some flexing in the rear suspension mounts when pushing the stock Kappas. GM engineers have confirmed this and several aftermarket companies are offering braces to stiffen things up. I know DDM and Kappaphere have offerings. I would like to hear feedback from anyone using these products. Are you seeing improved control while accelerating through turns?

[Kappa Fan]

Originally Posted by Sky Hi

Apparently there is some flexing in the rear suspension mounts when pushing the stock Kappas. GM engineers have confirmed this and several aftermarket companies are offering braces to stiffen things up. I know DDM and Kappaphere have offerings. I would like to hear feedback from anyone using these products. Are you seeing improved control while accelerating through turns?

I *know* that if your truly want to see a difference in how your car handles then you should order the Rear Suspension Support Crossmember part #25877302 that is used on the Solstice GXP ZOK. This part can be ordered thru gmpartsdirect.com for around $257 plus shipping.

Here is an excellent article that talks about the new crossmember - go to paragraph 5. Automobile-Heinricy_Win_on_Sunday_Fix_GM_on_Monday

[puggsleyssky]

Does the car really need the brace if one doesn't race it? Are we just adding unnecessary weight to the rear end?

[Jay_Sin]

Originally Posted by puggsleyssky

Does the car really need the brace if one doesn't race it? Are we just adding unnecessary weight to the rear end?

If you don't use your car to handle corners like it was designed to, then you probably are not going to notice much from this addition.

[KimberlySky]

My front end is awesome I feel a complete difference in the car how she handles on curves, turns and straights.

[LongSky]

Originally Posted by KimberlySky

My front end is awesome I feel a complete difference in the car how she handles on curves, turns and straights.

What are you talking about KimberlySky?

[Leather]

New bra maybe?

[clif]

Originally Posted by Kappa Fan

I *know* that if your truly want to see a difference in how your car handles then you should order the Rear Suspension Support Crossmember part #25877302 that is used on the Solstice GXP ZOK. This part can be ordered thru gmpartsdirect.com for around $257 plus shipping.

Here is an excellent article that talks about the new crossmember - go to paragraph 5. Automobile-Heinricy_Win_on_Sunday_Fix_GM_on_Monday

From the article I am guessing that the part mentioned is a REPLACEMENT, for the stock crossmember, not a bolt on stiffener? If so, oit is out of my capacity as a mechanic because it would probably lead to the necessity of a 4 wheel alignment after installation. Are there any photos of the part either in or out of a vehicle?

Thanks,
Clif

[Mandi]

Were does this crossmember attach to? I'm hoping its runs from rear bushing to rear bushing of the rear control arm......they are kinda just hanging out there.

[Kappa Fan]

Originally Posted by clif

From the article I am guessing that the part mentioned is a REPLACEMENT, for the stock crossmember, not a bolt on stiffener? If so, oit is out of my capacity as a mechanic because it would probably lead to the necessity of a 4 wheel alignment after installation. Are there any photos of the part either in or out of a vehicle?

Thanks,
Clif

Sorry, I could not find a picture. But, according to the article this is a NEW addon. There is no "stock" crossmember currently on anything except the GXP/Redline ... there WILL be in 2009 on the NAs, but not now.

The engineer that pointed me in the direction of the part and the article would have mentioned the need for alignment if it would have been required - of that I am certain.

[clif]

Originally Posted by Kappa Fan

Sorry, I could not find a picture. But, according to the article this is a NEW addon. There is no "stock" crossmember currently on anything except the GXP/Redline ... there WILL be in 2009 on the NAs, but not now.

The engineer that pointed me in the direction of the part and the article would have mentioned the need for alignment if it would have been required - of that I am certain.

I see. Do you know if it is a replacement for the crossmember on the GXP/Redline? That is what I meant.

CLif

[Kappa Fan]

Originally Posted by clif

I see. Do you know if it is a replacement for the crossmember on the GXP/Redline? That is what I meant.

CLif

It is my understanding (again from reading the article and speaking with an engineer) ... that the crossmember on the GXP/Redline was still 'flexing' on the T2 race Solstice and was replaced with a stronger crossmember.

Therefore ... I would say YES ... it is a replacement for the one currently on the GXP/Redline.

[clif]

Originally Posted by Kappa Fan

It is my understanding (again from reading the article and speaking with an engineer) ... that the crossmember on the GXP/Redline was still 'flexing' on the T2 race Solstice and was replaced with a stronger crossmember.

Therefore ... I would say YES ... it is a replacement for the one currently on the GXP/Redline.

Thanks, I thought so. I do not think I want to try this on my back on my garage floor!

Clif

[RobL]

I changed mine (I installed the Z0K suspension package on my Sol).

It's 6 bolts to swap out plus I think I remember I had to take off a lower control arm. It's not for the non-mechanically inclined but not too difficult either.

The differences in the parts is a 1/4" C-channel that is welded to the standard crossmember and the bushings that attach to the diff are of harder material.



The main difference in the feeling will come from the bushings not from less flex in the crossmember.

[Dave@ddmworks]

Rob beat me to it, but I can add a little more to this.

The Z0K package includes an upgraded crossmember, or more accurately a welded "C" member to a stock crossmember. We had a chance to talk with a couple guys from GM performance when we were down in Florida. I told them about the brace we were developing at the time, figured might as well get some feedback and see what they had to say . We told them about our experience in the Miata community and how we would see some flex in the lower sub-frame on the earlier models that did not have the lower suspension boxed in. Simply adding a bar accross the lower suspension pick-ups in the Miata and boxing in the rear, took care of the problem, and that was the first thing we tested on Randy's Solstice. Then we told them the problem we immediately ran into on the Solstice was that the exhaust was in the way, and if we moved the brace forward or back enough to clear the exhaust, the brace was becoming less and less effective. Also our test car has clearance issues since it is lowered. We struggled with a bunch of different designs trying to support the rear suspension pick-ups on the Solstice/Sky and nothing seemed to work, it would either hit the exhaust or get destroyed by the lowered car.

So after telling all of this to the GM performance guys, we learned a little more about the GXP / Redline brace found on the Z0K package. They tested pencil braces coming up from the lower suspension of the car and it tested well, but they had clearence issues also. Also when they analyzed what was going on back there they found that the crossmember that holds the differential was actually flexing under high cornering loads. So their solution was to make a really trick "C" channel to fit over the rear crossmember. They said in testing that it provided to have the same improvement as the pencil bracing, but was a lot easier for them to install, 1 piece welded to the crossmember and that was it. I talked to them about bracing the rear suspension forward also and asked if they tested that, and they had, and found that there was no measurable improvement going forward.

Hope that sheds some more light on the subject for you guys.

[Jay_Sin]

Originally Posted by Dave@ddmworks

Rob beat me to it, but I can add a little more to this.

The Z0K package includes an upgraded crossmember, or more accurately a welded "C" member to a stock crossmember. We had a chance to talk with a couple guys from GM performance when we were down in Florida. I told them about the brace we were developing at the time, figured might as well get some feedback and see what they had to say . We told them about our experience in the Miata community and how we would see some flex in the lower sub-frame on the earlier models that did not have the lower suspension boxed in. Simply adding a bar accross the lower suspension pick-ups in the Miata and boxing in the rear, took care of the problem, and that was the first thing we tested on Randy's Solstice. Then we told them the problem we immediately ran into on the Solstice was that the exhaust was in the way, and if we moved the brace forward or back enough to clear the exhaust, the brace was becoming less and less effective. Also our test car has clearance issues since it is lowered. We struggled with a bunch of different designs trying to support the rear suspension pick-ups on the Solstice/Sky and nothing seemed to work, it would either hit the exhaust or get destroyed by the lowered car.

So after telling all of this to the GM performance guys, we learned a little more about the GXP / Redline brace found on the Z0K package. They tested pencil braces coming up from the lower suspension of the car and it tested well, but they had clearence issues also. Also when they analyzed what was going on back there they found that the crossmember that holds the differential was actually flexing under high cornering loads. So their solution was to make a really trick "C" channel to fit over the rear crossmember. They said in testing that it provided to have the same improvement as the pencil bracing, but was a lot easier for them to install, 1 piece welded to the crossmember and that was it. I talked to them about bracing the rear suspension forward also and asked if they tested that, and they had, and found that there was no measurable improvement going forward.

Hope that sheds some more light on the subject for you guys.

Any chance of pictures?

[Dave@ddmworks]

Originally Posted by Jay_Sin

Any chance of pictures?

In RobL's post you can see the brace that they add on the ZOK package. It is the extra part that is welded to the brace. You can see 1 hole through it and part of another hole. That is what is welded onto the brace to stiffen it up.

[yamatr3]

I bought the ZOK brace and posted some better pics at the Sol forum.
ZOK Rear Diff Brace - Pontiac Solstice Forum