ce_hensley

My 95 C2 feels wobbly around 50mph +/- 3mph, but fine at all other speeds. Seems like my last 95 C2 had the same thing. Anyone else?

rcwelch

Not me...rock steady. Check alignment,...balance issue?

cabrio993

Pirelli tires? Has the car been sitting for a while? low air pressure? Does the vibration goes away after you warm up the tires?

95 C4 993

Rotors and pad replacement fixed that issue I (once) had. Went from Zimmerman to Genuine Porsche and problem fixed. The Zims warped after about 23k.

Edward

Actually not all that uncommon. Mine is at that speed, as well. Others have reported that a good wheel balance from a good shop (with a Hunter machine) will help or cure it. I think I recall one having had to go to one of those "balance -on-the-car" type deals to get it right. It may have to do with bushings wearing on higher-mile cars, or also tires wearing down. I've heard various "reasons" for this strange wobble that a regular tire balance doesn't seem to be able to address. FWIW, my car has 106+K miles (though the bushes seem fine to my eye) and the tires are greater than 60% worn down, so maybe it's a combination of things. Another thing to check is inside the wheels ..make sure you didn't pick up anything that stuck itself to the inner wheel to cause a small imbalance. I guess it just doesn't bother me enough to do something about it.

Edward

tj90

Callas tech session taught us to check the front bushings on the A arms. This is tale-tale sign that the rubber bushings are cracked. Jack up the car and insert long screwdriver to wedge between frame and a arm. Puttension on bnushing by prying a-arm in the axial direction toward the front rims. - if the rubber is cracked you will see it. Be ready these bushings are only sold with the A-arm - $500-1000 a side!

gjtrek

Mine had an identical issue at around 60 mph on light to medium braking. I got new tires, had the wheels balanced to a gram, eyeballed the control arm bushings(they looked okay) and changed the tie rod ends. Finally, micrometer to the rotors. No warped rotars BUT, BUT...on the left front rotor the rotor faces were not parallel with one another. Swapped out a different rotor on the left front and the wobble disappeared. Tried to get the stealer to provide new rotor (old one had about 4K miles on it). Local Stealer declined. With one new rotor purchase all is well. What a great feeling.

This challenging problem diagnosed by Pacific Power Motor Sports in Concord. No Affiliation, just satisfied customer.

Regards, Gary

Jack of Hearts

My car also has a tiny SW shimmy at 55 mph. never was there until I replaced stock (original?) front roters with Zimmerman. By 58 mph shimmy is gone so not worth chasing. Next time I'll go back to Porsche stock rotors....apparently balanced better. I'd argue that control arm bushings would not cause a 1-2 mph-specific shimmy that then disappeared at higher revs. (All respect to Tony, though.)

geolab

Is it wobbly while braking? or wobbling while cruising?
If the latter, you have to balance your front wheels.
Make sure that you place the anti-theft lugnut OPPOSITE the valve when tightening the wheel.
If wobbly at 100mph, then its your rear wheels that need balancing.
Some said alignment , but I am sure they meant wheel balancing.
If wheel balancing does not cure the whoble, rarely, then try the above solutions

sidned

You might want to try cleaning out the holes in your rotors. They can get clogged and a good jetwash to clear them out can sometimes work. It doesn't cost you anything, so give it a go and see if that sort your wobble out. Make sure you go for a drive straight after or the rotors will rust very quickly and may cause the pads to stick.

TomF

Steve W. mentioned to me that over-torqued lug nuts can cause a similar symptom as a warped rotor. With factory wheels, if they are over the factory specs, it can cause the wheel to distort imperceptibly. Re-torque to the correct specs and they are fine.

Also, check your tie-rods ends. As I have mentioned many times before, these darn things fail slowly and are really hard to diagnose. They fail more often than people realize and cause all sorts of issues. Most p-car owners don't realize that the inner ends have a rubber isolator that fails...

alpinadvl

You didn;t say where you are from.... but....

JUST A SUGGESTION for us WINTER DRIVERS : sometimes snow will lodge behind the wheels... and create a shimmy / wobble / shake at a specific speed ....had this happen to me after driving through some snow today. Cleaned out the caked on / compacted snow....and got rid of the shake

2ndof2

I'd check for the following:

1. poor wheel balance
2. uneven torque on lug nuts
3. bad tie rods or bushings
4. worn shocks/struts
5. uneven tire wear

Those seem to be the most common explanations for what you are experiencing. My car did the same thing. Never heard of Zimmermans not being that well balanced, but I mistook them for OE and have em up front. I've had no problem since I replaced the tie rods and put in new bilsteins so I think its probably unrelated to rotor balancing but you never know.

cabrio993

Check your tire pressure, it could be as simple as under-inflated tires. Also, some brands of tires can flat spot easily if thet sit in the garage for a day or two.