09 GL-450, I purchased new set of tire, Nexen Roadian HP SUV 285-50-20 from tirebuyer.com.
- 11/9/12 mount & balance, wheel alignment at the MB dealer
--> car body shakey at 65~70 mph
- 11/30/12 re-balanced at the MB dealer
--> still shakey
- 12/15/12 went back to the dealer, asked to check any bent rim or tire defect,
the tech. said no bent rim and no tire defect, even the tech. checked the tires
with the road forcement. Also the tires are well balanced. The service advisor told they are assuming the problem is caused by cheap tires and they are not the recommended size by MB.
--> since the last visit the dealer, my car is still shakey.
My old tires are Good Year Run flat 275-50-20. I did not have any shakey problem before.
Any advice or idea? Thank you in advance.

My car used to get 17 miles/G with old tire. Now only get 15~15.5 miles with new tires. Is it due to the tire size?

 

I have 285/50/20 and no shaking at any speed. Your cheap tires might be the problem. Make sure they use Hunter RoadForce 9700 balancing machine to balance your tires. When I bought my Hankooks I had the same issue until I used this machine.
You can find who has these machines here : http://www.gsp9700.com/

 

The MB dealer has same machine and they balanced my tires with it.
I purchased the Nexen tires for good price and lots of positive reviews from customers. What brand of tires with 285/50/20 you have?
Thank you.

 

I have Hankook's and bought it here :

http://www.performanceplustire.com/p...reDataID/26954

 

When we got our truck, it would vibrate going over 70mph. I took the wheels to the shop and I knew the person who owns/runs it. The person is a friend of mine that I could trust. The wheels were "balanced" alright. As if somebody on purpose messed with balance. They were way off. Got them balanced. No issues.
I would not be surprised if dealers "balancing" wheels so you can come back soon for a new balance or new tires.

 

Thank you for your input.
That case is possible. But, the dealer charged me just one time on the first visit.
They did not ask me to pay for 2nd and 3rd visit.
I'm not sure the tirebuyer.com would exchange or accept the trade in for other brands since they are already used.

 

The dealer's hunter dsp is in need of calibration. Take your balancing needs elsewhere equipped with hunter dsp