Tires

If the car is new and the tires are still within warranty, they will replace your tires for free of cost... the labor you might have to pay is the mount and balance. If the car is still under warranty, the dealer should investigate and see if anything needs to be repaired to fix the problem.

I'll contact them tomorrow. they're some distance away. I know I can Google til the cows come home but may not find informative first hand info. So here's a second question about tires. The tires on the C63 are definable inadequate as far as size. Anyone put a wider tire on the stock 18" rims and fit in the confines of the fenders etc?

On what basis do you think the tyres are "inadequate"?

DAS

Since buying the car I've been looking around the internet for info on it. Seems grip, from rear tires is perhaps not as great as it should be. I know that other cars with this much output capability many times have more rubber or wider rubber, on the road, like Michelin or Goodyear Super Car tires. The rims, on the C63 perhaps would handle one size wider tire though? Tire life is not great with them though. The Michelins on our little SLK were wider than these tires. I don't remember the size right now.

e "inadequate"?

Tires could be the reason, but quite new Continentals? I'd doubt that.

More likely it is alignment of the suspension. Are you sure the car did not have an accident before you bought it?

"inadequate"?

Fifty miles on the od. I would have preferred to see none of course. Don't see any evidence of it. Right rear wheel has a paint smear from one shade to the other. I think I'll ask for that to be replaced. Alignment shouldn't cause that sensation. A bent or warped rim or a tire not exactly right, especially ones without a center rib, or a worn tire with the belts out of whack. Maybe some other things. I hat to have to have to fool with things like this on a new car.

res are "inadequate"?

Of course you should look for wheels/tires before anything else,

If it is wheels/tires, it would be some unbalance in front wheels. Your can try to swop rear wheels with front wheels to veryfy this. If problem persists, it is unlikely that you have same problem in both sets, and the problem should be looked for in the steering/suspension.

Wrong toe could definately cause your symptoms. This is easily verified and adjusted at any service station. If adjustment is wrong, the question is how this happened, therefor my question of possible accident.

Difference between wheels in caster angle could also cause the symptoms. Caster angle is not adjustable, and wrong caster angle can only be caused by mecanical deformation. That's the second reason for the question.

If the problem is in the steering/suspension, you still have the dealer to return to.

tyres are "inadequate"?

quoted text -

On a brand new car there is no question what I would do. I'd take it right back to the dealer. No reason the steering wheel should be shaking from side to side above 70 mph on any new car. And I would not assume it's the tires. I once bought a new Ponitac and every start from a dead stop, I'd here a metalic snap, metal hitting metal. They tried to deny anything was wrong, but I got the service mgr into the car and finally convinced him something was not right. Turns out they used bolts that were too long to secure the whole engine/trnasaxle to the body. So, every time you started out, the whole thing moved 1/8" or so causing the noise. Which shows you sometimes something can be very wrong with even a new car.

The Continentals, on the new Merc do just fine until you get to about 70 mph. They shake the steering wheel side to side. Should I talk to the Dealer or just buy new tires? if I talk to the Dealer and they agree, they will probably want to replace them with the same brand. Might not be a bad idea but I think differently. What tires are quiet, stick like chewing gum and last many miles? I had Michelins on the last one: all seasons (Y) rated.

Possibly they just need to be balanced?

jas

I assume that Continetals in US are the same as in Europe, and here they (SportContact2) are considered as being among the better (and more silent) in the class. I drove them myself, and my only complaint is that they wear a bit too fast (because the prioritize other parameters higher).

The shaking around 70 mph is because this is where the whole steering is in resonance. Any imbalance will be felt most at this speed.

Deformed and/or unbalanced wheels/tires are the first things to suspect.

Next is suspension alignment.

The geometry of the wheels is constructed as a balance between easy handling and stable straight driving, where the speed of the vehicle will tend to straighten out the course. This balance is usually optimized at a point, where only little force is required to turn the wheel but enough force is applied to keep a steady straight course. If this alignment is not right, the balance is moved, and if it is moved toward less force on the steering, the steering will tend to oscillate. Again felt most around 70 mph due to the resonance.

Even a small accident (like hitting the curbs hard) may deform steering/suspension parts (or worse the chassis) causing misalignment.

Play in the steering balls can amplify the symptoms, but I would not suspect that on a relatively new car.

Probably some experienced guys can tell the difference between unbalanced wheels and misaligned suspension, but I cannot.

I have a chassis, that is slightly deformed, so I could not get caster angle into specs. Instead I adjusted both sides to be equal and gave a little more toe-in than specified. That solved my problem after having gone through a lot of pain and expences trying different tires/wheels.

I suggest you look into Tirerack.com... they got great customer reviews there. Since it is C63. I believe you won't be driving in the winter without snow tires... so it is best to look for Ultra High Performance Summer tires only.

The Continental you have may be All Season High Performance Tire... which is completely different than the strictly summer tire only and a major improvement in traction... on same size tire. Tirerack will list any other size tires you can install on your car.