JeremyR

I just took a 200 mile drive on 95 and the whole time it felt like the rear end was going over a series of small bumps. Nothing that felt dangerous or out of control, just a constant bouncing that seemed to increase with speed.

Figuring that the 911 may be more sensitive to out of balance rear wheels with all that weight back there but wondering if there is something else that I should be looking in to...

chuck911

Assuming it was not just on the 95 where you felt this then you may have bent a rim or thrown some weights. Grab a flashlight and go have a look.

Team Plutonium

Wheel weights, loose wheel in general, tire pressure (although that is basically idiot proof in a Porsche), suspension issues, etc... I'd say take her in, put her up on the lift. Def not normal.

JeremyR

Agreed, although I see a "felt fine to us" in my future.

Team Plutonium

LOL! Yup, been there, done that. Good luck!

worf928

How many miles since delivery? If very recently delivered make sure the shipping blocks have been removed from the springs.

If new behavior, then looking for wheel balance issues, as above is good advice. Also:

Are your tire pressures set correctly?

If your's is PASM-equipped did you accidentally put the car in sport or sport+ mode?

JeremyR

Its 13 months old with 8500 miles so its not shipping blocks. Pressures look fine on all 4 wheels.

It has PASM and PDCC. Put it in sport and sport+ (and hit PDCC separately) and it didnt seem to make a difference with this, so it seemed like an out of balance wheel to me too

chuck911

So, back to post numero two-oh. How'd the wheels look?

JeremyR

Nothing looked odd. No obvious bent wheel or missing weights. The winter wheels/tires are stored over the summer though and it wouldnt surprise me if they lost a weight or just need a balance

Pcar991

Examine the tire closely. Could also be a nail or screw in it. Run your hand over it all around.

worf928

Yup. If all the simple, obvious culprits are innocent then wheel balance is the next most likely culprit.

drmatara

does it happen on other roads as well, or is it specific to 95?

JeremyR

Well, at the very least it seems more noticeable at speed and in the monotony of 95, but I doubt it was the road itself as I drove on the NJ Turnpike and 95 through Delaware and Maryland which each have different surfaces...

drmatara

The reason I asked is because I do feel similar bouncing on some specific roads here in SCAL, but I'm not worried because I drove various Porsches over the years and all did experience pretty much same behavior, also I noticed it more with tire inflated at full spec. Did you drove your car before on this particular road and it was ok? If so, yeah check the balance of the wheels and the tire pressure, if that does not help, take it to the dealer for inspection

JeremyR

I took the pressures down to the comfort spec when I put the winters on. I so rarely drive it for as long (and as straight at constant speeds) as I did today that I really cant say if it is truly new or I just noticed it. I am going to take it in...have some other stuff for them to take care of anyway