Hi List,

I took my car out and was doing some freeways runs.

I have some shakes about 80 to 100 mph, but they seem to be reltated to load. They seem to kind of come and go.

Any suggestions on sources of vibration. MM, Wheel balance and alignment done within the last 1000 miles.

Torque tube? trans mounts? I think my rotors are a bit warped. could that cause vibes at higher speds.

LO

 

i believe most places that balace your tires do it to 60-75 or something, since that is the speed limit.

 

Tires - Flat spots from sitting too long? Cupping from being previously out of balance? How old are your tires? Could you just have old ones or a tire that was out of round from the factory?

Everything underneath the car secured tightly? I've heard stories of vibration being caused by something coming loose under the car. Commonly this doesn't cause any problems at low speed, but as speed increases, the increased airflow causes the problem.

 

Vibration that changes with load (not with speed...) is a driveline problem. Two options: Torque tube, where the center shaft spins at engine speed. If the vibration and noise change with engine speed rather than road speed, look at the torque tube bearings. Option two: CV joints, which turn at wheel speed. CV joint vibrations change depending on whether you are on or off the throttle, at least early in the wear. Realistically, they fail only if they are operated with the boots torn and the grease dirty or missing. Crawl under the car and see if all four boots are intact. Grab each driveshaft and move it in a radial motion to determine play. If you can feel play at either end, they probably need attention.


All that said, most speed-related vibrations are due to tire problems of one kind or another. Foolproof diagnostic method is to borrow a set of known good round tires/wheels to try out for a short drive. You'll quickly confirm or eliminate tires as a possible problem. Some tires with internal damage may "balance" OK, but still vibrate. There are 'road force' balancers that can simulate the weight of the car while spin-balancing the tire. This will help identify flat spot damage, as suggested by others, and can also help spot other internal cord damage or bruising.

Your warped rotors are typically only an issue when you apply the brakes. Pulsing pedal is the symptom.

 

I've had a weird, subtle vibration that came and went with a 10 second period. Happened twice after new tires. Rear tire balance (1 tire off an ounce) both times. Speed but not load related, as dr. Bob says.

 

Hi All,

I just drove the car a bit. To Palo Alto and back.

I wanted to try 280 out which is the smoothest road within 20 miles of me.

It seems to be a wheel speed thing that may be worse under load.

The smoother road does seem to help. but the tire idea has me thinkng.

the car is really smooth at 70 to 75, about 80-85 it starts coming on. at 95 it is annnoying

I am not running the front spoiler ... have not yet put it on.

I just put in my 8" lights though... they look sweet... so I will feel good abput my weekend efforts...

missed bill's fun ride .

need to try and get this car presentable for Sharks in the park...


LO

 

Loren, that definitely sounds like tires. Take it up to 95, let off the gas, put in the clutch and put it in neutral. This will eliminate TT, engine, etc as possible causes. If it still vibrates, it's almost certainly tires. You could try re-torquing lug nuts, pulling off the wheels and looking for small foreign objects on the mounting faces, etc but it sounds like what you really need it to have the balance checked. Maybe it's nothing more than a wheel weight gone astray since they were last balanced.

 

Like Dave ,my guess would be (rear) tires - thinking of the speed - maybee a balance "block"( don't know the US term - Pb) has come off . Flatspots due to long stillstanding should go away after a short while......

 

Get the tires Road-force balanced! Not only will the machine give the proper tire balance, but it will match the tire to the rim and measure later and radial runouts on the wheel (measure it's trueness and roundness). If all checks out, then you can begine to look at other factors.

 

Thanks all,

I will look into balance options in my area. Dave any suggestions?

I have an almost new set of yokohama AVS sports 16 X 7" on right now.

Thay are glass smooth until like 80 to 85 then it goes downhill.

Thanks

LO

 

I had mine mounted and balcanced at Devek. I had one tire from my previous set repaired and balanced at America's Tire Co. No issues with balance in either case, but the guys at ATC had to be told NOT to put the car on their big flat lift that lifts on the underbody of the car. They would have done some serious damage if I didn't stop them. Balancing is not rocket science IMHO. You should be able to get a good spin balance at any number of reputable tire shops, just watch how they lift the car. If you find a place that does road force balancing locally, please share your experience...