beasters

my 996 has a very unstable feeling rear end when going over bumps. It's such a strange feeling. Like you have no control over the car for a moment. I have replace rear lower control arms and alignment adjusting bolt. Just had the car aligned but I wondering if the unevenly worn rear tires are causing this feeling. The adjustment bolt was seized and I recently got it removed so it can finally be aligned. The car has a 1" tein lowering spring it looks like. Do you think new tires will fix this or is there another part I can replace to make the rear ending more stable over bumps? Any help would be appreciated, thanks.

MoeMonney

I would say bushings.

808Bill

Motor mounts. Pretty much all the rubber bits and pieces are 17 years old and need (not should) to be replaced.

Barn996

How many miles on your Porsche? That answer may help determine what is going on with your instability.

cds72911

Deleting a post that didn't make sense after I typed it (I was thinking maybe a bump steer sort of effect in the rear of the car because of lowering).

beasters

my car has 52k miles on it.

beasters

The rear of the tires are very bad due to the previous owner never getting it aligned properly because one of the rear camber adjustment bolts were seized into the rubber bushing. I got that taken care of and the car can finally be aligned now. It still has this weird feeling of the road inst perfectly flat. Seems as if the steering wheel goes on a slight angle while this weird feeling happens. The front are pirelli tires dated from 2005... the rear are not that old but the poor alignment has caused these tire to have very bad inside wear. I guess the best thing to try first is new tires but I'm wondering if it could be due to being lowered. The car drive great except for when going over bumps or imperfections. This sensation happens at 20-40 miles per hour all the time. Hate it

cds72911

Okay, so I'll just throw this out there, although it may not be right.

When you lower any car you change the angles of the suspension components. One potential result is called "bump steer", that could explain what you are feeling in the steering wheel.

Lots of stuff out there that can explain it better than me, but this Rennline product description does a good job while keeping it simple: http://www.rennline.com/Rennline-Fro...ctinfo/S75.10/

If someone lowered the car by just throwing on springs or springs and shock/struts and not thinking holistically, they may have introduced this behavior.

The good news is that if it is a bump steer issue, it's fixable.

You might want to take it to someone who has more experience with suspensions on lowered cars? Or find someone local who races or does DE in their 996, maybe?

rogazilla

If front is from 2005 and the rear is more than 5 years old. Go ahead and change out your tires then work on everything else afterwards.

808Bill

You'll be amazed at what good/new tires will do, assuming your all aligned now.

beasters

Yeah, I think I'll at least replace my rear tires which are the worst as far as wear goes. Let me know what options I have please. The custest tires on my car are 285/30R18 93y bridgestone (Rear) and 235/35 ZR 18 86Y (Front). Are these the most cost effective/ performace effective tires or should I look at different options based on price?

sammaw

I had this on my 2002, it was the rear shocks. would bounce, jump sideways on the expansion joints on the motorway. as for tyres I like the PS2. I find them ok on wear, and good for road noise and rain.

Norcal_996

First thing would be to get all new tires of the same brand and tread. I find it hard to believe it would be a bumpsteer issue. My control arms sit about 3" off the ground and I have stock tie rods and rear links still and the bumpsteer isn't anything like what you're describing. Motor mounts made the biggest difference in my car, it felt especially unstable during hard acceleration.

5CHN3LL

I have no idea what those tires you mention are appropriate for - are you looking for a UHP summer tire, an all-season performance tire, a "touring" tire? The tire you buy only because it's what was in stock is almost guaranteed to be a disappointment.