Noticable side to side rocking"
 

recently, I've noticed that my car seems to have lost dampening when subjected to side to side undulation of the road. the car response with much greater rocking in response to quick left-right-left motion of the steering wheel.
My car is a 01 box, standard with 126K miles, no accident or "damage".
new Michelin Super Sport tires, all four in April, 18 inch wheels with 36/32 psi f/r pressure.
changed out sway bar drop links 2 years ago and checked the bushing.
the car does "klunk" over speed bumps and rough road when warm and driven slowly.
engine mount 2 years ago.
shocks have not been changed.
maybe the lower arm to the suspension subframe is worn and is sloppy?
any thoughts - greatly appreciated.

Tad

Most likely cause is worn out shocks. The stock shocks typically lose a lot of their dampening ability by 100K miles.

New tyres, contrary to belief, will infact give more compliance on the side walls than an old and worn tyre will. The extra tread will give a floating effect when rocking the steering slightly from left to right at higher speeds, most noticable beyond say 50mph. It can actually feel quite worrying at first but give it say a few thousand miles and it will be far less obvious.

The knocking you are talking about, I would be 95% sure (if its coming from the rear and below say 30mph on cobbled and slight bumps) would be your rear fork control arms. This will not show any signs of play and will require replacement arms to fully remove the noise. Very audible inside the cabin due to the arms attaching at the firewall behind the seats.

Gaz

I second all the advice you have gotten so far in this thread. I will add that the MSS tires have amazingly soft sidewalls so add 4psi to the rear tires & see if you like it better.

thanks for the many response.
I'll pump up the rear tire and see. but I fear that shock replacement i$ most likely needed.

I haven't had any issues with a lack of stiffness on PSS tires (18's). They feel very responsive with factory tire pressures.

I would have thought that 32lbs in the rear is too low. I would run 36 square with your set up.

I feel like you have never driven your car hard...

Boxster's understeer like crazy. The quickest, "remody" to any balance issue is tire pressures. Factory pressures are 29/36 Front/Rear. 36 square is ridiculous in my honest opinion.

However, for the original post's question. Shocks/struts are most likely your problem, as previously stated. Best of luck!

Happy Boxstering,
~Brad

OK Brad, you run yours anyway you like. Hope to see you on the track someday.

To the original poster 29f / 36r is a long way from 36f / 32r. Brad may be right about struts etc. but I would make sure you are not leading yourself astray with your tire pressures before you start spending thousands on replacing.

It's a long time since I've run stock tires on a BOX. How does everybody else feel about 36f/32r?

Front 32 / Rear 36

Would probably be better. But that's not what Sb01box stated at the outset (36/32 f/r) which is why both I and BYprodriver suggested raising the rear pressures.

Sorry Dave, I just realized you were answering my question and I took it as correcting my prior post.

went out and checked the tires this morning. at about 6:30 am, the temperature (per the boxster instrument panel) was 58F.
tire pressures were 32/30 front/rear.
got it pumped up to 34/36. could not notice any difference.

as for the tire pressure, I should have really measured it before posting. the numbers were from when the tires were installed back early this year.

Next thing I would do is get under the car with a set of wrenches and a pinch bar and make sure everything is snug, that none of the rubber bushes are obviously damaged (ie you can't use the pinch bar to shift up or down across the direction of normal rotation) and that nothing is broken. When you are confident that all is in order I'ld be think new shocks time.

I've run those pressures on the track and it definitely dials out some of the understeer. For the street,I run 36 square.

To check the struts, stand int the frunk and trunk and jump up and down to get the suspension moving. It should stop as soon as you stop moving.

I've got into the front trunk and jumped up and down. the shock appears to be doing it's job. solid dampening.
I'm going to go slow ($$ wise) will check and most likely replace the sway bar rubber bushing as a starting point. will check the drop link as well.