Skylaw

I wrote the following for the W220 forum, but it has wider applicability; so I am posting it here, and invite any experts to add to the knowledge base.

It may help to discuss many of the sorts of things that can cause vibration - some of them will be common, and eliminating them is the only thing that will help. This list doesn't cover every possibility, but it hits some common causes of vibration.

1. Balance, which can be affected by -
a. Improper amount of weight. Neither tires nor wheels are usually perfect, and need balancing whenever tires are changed, and periodically (for wear) after. If permitted to remain long enough, will cause flat spots in the tire, which will then always vibrate. Static balance just won't do - you need to have tires dynamically balanced, at the speeds you drive. Also, if the wrong type of weights for your wheel type are used, they are likely to come off, giving you an instant balance problem.
b. Poor quality tires or wheels. An indication of either is use of a lot of weight. One reason I have liked Michelin and Pirelli is because with quality wheels, I have rarely had to use more than 1/2 ounce of weight on a wheel. Continentals have always required much more weight in my experience, and maintaining balance has been tougher. Tires of inferior quality may also have poorly aligned belt and tread layers, and may simply be out of round. Damaged tires may have similar problems (a broken belt from a pothole will result in a lot of bounce because the tire cannot stay in round).
As an aside, if you see a lot of weight, first be sure the mechanic removed all weights before balancing. I have personally never had a wheel using more than 1-1/2 ounces balance satisfactorily. Last year I put new Michelins on stock M-B wheels; noting a tickle driving home, I checked and found approximately 3 to 4 oz on each wheel! When I had the weights stripped and re-balanced, I had no more than 1/2 oz on any wheel; and the balance is still nearly perfect after 12K miles. Balance is dynamic; unless it is perfect, the forces acting on a wheel are different at different speeds. The chance for error increases with lots of weight.
c. Not balancing the tires the way you will run them. Don't add heavy pressure indicators or valve stem covers, caps, etc. after balancing. Balance with them on (yes, the decorative M-B valve stem caps will give you a tickle at 60-70 if wheels were balanced without them. Trust me).
d. Uneven tread wear, which itself has a number of causes discussed below. It will obviously affect the weight distribution of the tire, and it will also cause other problems; feathered or uneven treads will cause vibration even beyond that caused by balance. Tread wear from balance problems tends to be flat spots; alignment problems cause different tread wear patterns.

Improper alignment-
Improper camber will not cause a vibration per se, but can cause uneven tire wear that eventually affects balance and smooth running of the tire. Mechanics insist that improper toe will not cause vibration by itself, but I remain skeptical; even if not, it certainly causes rapid and uneven tire wear, which in turn affects balance and smooth running. Improper caster has no effect on tire wear; it can affect steering (the rate of return to center coming out of a turn, as I understand it). Bad alignment is the cause of many tread wear problems that will create vibration even if the wheels are perfectly balanced (and with wear problems, they probably won't even stay balanced for long).

Improper inflation-
Causes a different type of tread wear problem than alignment, but the results over time are the same.

Suspension wear-
Causes tire wear problems discussed under alignment, because it may make maintaining proper alignment impossible. It may also cause other problems not related to wheel balance and wear.

Damaged wheel(s). 'Nuff said.

Mismatched tires-
Not with respect to front & rear sizes, but rather tire design, tread pattern and rubber composition. It is possible for a mismatch that is severe enough to set up a dynamic coupling effect that also makes the car hard to control. Short of that, it can cause vibration and other problems.

With wheel balance problems you will usually feel some shaking in the steering column (especially if the problem is on the front tires); and you may see the passenger seat shaking (so is the driver's seat, and you can probably feel it) - especially if the problem is in the rear tires.

Wheel balance problems usually appear at one or two narrow speed ranges (of 5 to 10 mph, such as between 60 and 70), and decrease significantly or disappear outside of those ranges. Vibration from tire wear problems often appears over broader speed ranges, and tends to get worse with speed. The worse the wear, the broader the speed range. "Wobbles" at low speed can be caused by bent wheels, shifted belts ("runout"), suspension/steering problems, and road surface conditions unrelated to the wheel or tire.

I have never experienced the driveshaft problem or an engine mount problem in a Mercedes, but with those I would anticipate a higher-frequency vibration showing up in the transmission shifter, where a wheel balance problem usually doesn't cause this. The rate of vibration from driveshaft or engine mount problems will likely follow engine speed (decreasing after shifting gears, then accelerating again as engine speed increases).

The harmonic balancer problem that is subject of recall can cause a vibration in the engine, which will probably be felt in the steering wheel and possibly in the shifter - but all I can say there is it won't feel like a tire bouncing. It will follow engine speed, not vehicle speed. If your car is subject to this recall get it into the shop quickly, especially if you feel engine vibration. If the balancer separates, it will cause much more engine damage.