z99

Need opinions regarding potential cause. I had H&R coilovers and sway bars installed a few weeks back. No problems. Last week I had a Das Bar with Recaro poles installed. First thing I noticed was noise from rear suspension that vibrated though he bar (DAS bar connects to rear strut mounts). Then at the bottom of a hill just prior to elevation change I nailed the throttle. The car bounced back and forth side ways. Like a bad case of wobbling. Scared the #@# out of me. The same think happens coming out of a turn when feeding heavy throttle. In other words, outside rear being loading. Finally, in big dips or bumps in the road, I hear a loud clunk. This is all new after bar installation. Installer thought it might be sway bar links needing tightening. Does not feel that way to me. The clunk sounds and feels like up towards the strut mounts. Something is not right back there. Any ideas? Under load it feels like the wheels are all loose and ging all over the place. Never had a car bounce back forth sideways. You have to hang on and hope you end up on right part of the black top.

Thanks

Land Jet

Adding the bar has added torsional rigidity to your car and this has changed how your car is handling. If I were you, I'd take it to a shop that is into racing and ask them to sort it out. Don't take it to the dealer or just a tuner shop. You need someone who really understands suspensions. Your sway bars probably need to be re-adjusted and maybe you will want to install stiffer motor mounts and transmission mount to better control weight shifting issues. Where are you located?

The clunk is something that I cannot answer but qualified people should be able to. Maybe look at this link because the Das bar may have exaggerated this condition.

https://rennlist.com/forums/996-turb...from-rear.html

Joe Weinstein

I will bet the bar has nothing to do with it, and doesn't add appreciable stiffness
either. There's something wrong with the rear suspension. Either a part went
bad, or got installed wrong or loose or went out of alignment during the bar install.

Y65MPH

I cant believe you have never felt this condition before. Quite typical of the 996tt/GT2/GT3. You need to change out the control arms and while you are at it get rid of the stock engine mounts and go with a solid or semi solid mount. You will be blown away with how well the car handles with just these simple mods.

1AS

A simple place to start is make sure your tires are torqued properly. A loose rear wheel could do that. If you can't find something loose, then something broke. When you say "HR coilovers", do you mean HR springs, or HR springs and shocks? I have the HR springs with stock shocks, and feel they are poorly matched to shock valving at the rear. The rear also sits a bit too low, and bottoms the suspension over some bumps. I have just received the Bilstein PSS10 components from Tirerack, and will be throwing away the H and R's soon. They seem wrong for the car. AS

Land Jet

Joe is probably right. Still advise you to go to a suspension specialist.

Page

My car has the same symptoms as yours, but mines has H&R springs installed on stock shocks (car came with these). Personally think they are NG. Very scary when not expecting it. Steps out over bumps and if I drive over 80mph it gets very floaty and I think I'm going to loose it.
Did you have your car corner balanced when you had the coil overs installed. You might have to go back and re do the corner balance since your roll bar added weight (~50lbs) to the back of the car. That would be my guess. Also I would upgrade the rear suspension bits as mentioned above. Dog bones, control arms and rear adj toe link. Maybe go with the bump steer version if your car is low.

Let us know what you find out.

Joe Weinstein

The worst bouncing I ever had turned out to be one gas shock that had lost
all pressure and some oil. Needed a rebuild.

Hoosier_Daddy

Have you inspected the rear shock tops since mounting the harness bar?

dantzig

The DAS bar mounts to the top of the rear struts, as you noted. The three bolts have to be taken loose, there is a collar inserted, then they are replaced. This could be that the nuts aren't tight. That would make the shock not work right, and also produce some clunking. It's not easy to get back in there to check them, but that is where I'd go first.

This is essentially what Hoosier_Daddy said too.

-JD

theporscheguy

I have H & R's on my car and it is super solid.

z99

Thanks everyone for the responses. I did have car corner balanced and made sure all the wheels were torqued properly. I have the H&R "Street Performance Coilovers". The problem was discovered. The sway bar brackets that connect to bottom of struts had twisted. This caused the
rear sway bar to move upwards. More on one side versus the other. As a result, I believe the control arm was hitting the sway bar. Suspension travel was altered in unequal amounts on the two sides. The clunk was the sound of this contact. The brackets were twisted back into place. They installer told me that they put on some kind of bonding agent to prevent them from twisting again. My guess is that this happened during bar installation. Took it to the track this past Saturday and everything was fine. It was first time that I have tracked this car.

Off topic, but car was fast. We rented some track time at Beaver Run and had the head instructor with us. There were two 2010 GT3s. My car (X50) has Fab Speed full exhaust, intake, AWE tune, H&R coilovers, H&R sway bars, and Pagid yellow pads. I ran with 19 inch OZs and PS2s. I was over 2 to 3 seconds faster then the GT3s. I even had faster time then instructor driving one of the GT3s. Wish I could take credit for it as driver, but I think it was mostly the car. This is only my second season of tracking cars. That said, I think my current suspension is too soft and the PS2s were not the best choice (but best choice I could find for 19s). I rode in the Gt3s. They seem much more at ease at the limit. There was a whole lot of weight transferring and tire squelling going on with my car. Still, my car managed to stay with the GT3s in the corners and the straights were a big difference. The PS2s were shredded in the back after a long day. They were new with maybe 50 miles on them.

Will use the OEM 18s next time with stickier tires. Also, looking for a solution to stiffen suspension without buying another set of coilovers. Springs?

How much will the solid engine and transmission mounts cost installed?

z99

Joe Weinstein, you were right.


Larry, I am in the Philadelphia area.