jhg41977

96 993 C4S lowered, not sure on what yet. I get a steady pulsing vibration between 75 and 90 mph. Comes from everywhere, seats, steering etc. The speed it begins and ends seems to vary but is always between 75 and 90. Have driven at 80 with no vibration. Occurs under acceleration, deceleration and constant speed. Any thought on where to start?

ehanauer

Could be driveshaft.

e9stibi

If you still have the original lower control arm bushings, you should do a search for "Chris Walrod bushings".

P-daddy

^What he said, and wheel/tire balanced?

Stealth 993

Before you do anything else, check your tire pressure. Then have your tires rebalanced. After that have a shop check it out.

jhg41977

Going for an alignment tomorrow (hopefully) since the rear tires are junk after the ride home. Ill have them rebalanced the fronts while there and then new ones for rear.

FisterD

Had the same issue at 80mph (not that I ever drive that fast ). Bad rear tire. It has a bubble on the inside throwing the balance way off. It happened when I got a flat and damaged the sidewall internally. 2 new rear tires, no more vibration.

doberdog

Start with the simple stuff like tire pressure balance and then move to bushings etc.

jhg41977

I bought the car in WV and drove home to NH (800 miles or so). The rear tires had maybe 60-70% of tread remaining when I left. Not any more. Tires are JUNK. almost no tread remains on right rear, left rear is not much better. Glad I did not take the scenic route home!

Pulled the rears off to poke around. Did not see anything odd. Pulling the wheels side to side and up/down did not show any movement. Everything underneath looks original exception for the coil overs. Tire pressure was ok. A little uneven from tire to tire but all between 35 and 40.

Looks like Im heading to a shop. Any suggestions for a shop in NH area?

timothymoffat

Just curious, did you get a PPI?

Sounds like the car needs some suspension work if you "ate" a tire in such a small distance. 993s can eat rear tires (8K miles isn't out of the ordinary on rears though 10-15K seems average) but not that bad. Alignments should be checked whenever you change tires IMO and get the shop to check all suspension related components. Might be a good time to check the tires' age as well.

BobbyT

Am I reading this correctly? The rear tires wore more than 50% of tread depth in 800 miles?

If so, you have a VERY spirited driving style, or the rear alignment is way off. To get the rear alignment correct, you need a shop with some special equipment and techs that know how to use it. Maybe someone in the NH area can chime in here...

Ed Hughes

You've got a problem with alignment. You need to get new tires and get the setup correct. Then, we'll see if you have the issue still. Tires and wheels would always be the first place to look at, for such a problem as you describe.

I was on a 2500 mile long weekend trip with several P-cars a few years back. One was on new tires and fresh alignment. On the way back from our event, we stopped for lunch and saw that his rear tires were CORDED-we'd done the Tail of the Dragon, but c'mon, corded in about 1800 miles at that point? The person who did his alignment, shouldn't have. We rigged up strings in a Sears parking lot on a Sunday afternoon, while we waited for their parts runner to pick up a pair of like-sized tires from another location, and aligned his car-pretty darned good, as I recall-so we could finish our journey.

jhg41977

Yup, 800 miles and about 50% wear more or less. Back of the car is covered in tire dust. I spoke with the mechanic that the PO takes the car to. He answered all my questions and such. I elected to not do a ppi myself. Many will think that is dumb, and maybe it was. I got what I consider to be a great deal, so I am happy. I knew the clutch and rms needed to be done and I figured on some paint work for the bumpers and extra to cover the unknowns including potentially needing tires soon (not this soon). Im not concerned about having to get new tires, just want to get any potential issue worked out so I dont burn through a new set.

The PO is a member on the board and I want to be sure nobody thinks I am upset or that he mis-represented the car.

jhg41977

Someone mentioned 'spirited driving' Yeah, had a few moments of that, but nothing that should have worn the tires that quickly.

jhg41977

Theres a Sears down the road and a craftstore next to that.......