wenter

Hello all,
Recently I got myself a 2007 GL450. One of the previous owners have installed 22x8.5 rims with Nitto NT420s tires in 285/40 R22. When I got the car it had 40.5psi at the back and 39.5psi on the front. The ride was very bumpy. I have deflated tires to 32psi and ride is a little better. 2tires are bad and needs to be replaced soon. 2 tires are ok. I am trying to decide my course of action.
Option #1 - get myself 2 new Nitto tires of the same size and call it a day
Option #2 - replace all 4 tires with new Nittos
Option #3 - purchase stock 19" wheels and go for a different size
Option #4 - switch to 265/40 R22 tires and go with Pirelli Scorpion Zero or Hankook Ventus or Toyo Proxes
Option #5 - switch to 275/45 R22 Hankook Ventus

I was leaning towards the Option #4, but after little more research I think Option #5 is the most attractive at this time.

What do you guys think?

BlownV8

If bouncy, you have shock/strut issues. 22" tires should not cause your issue.

wenter

Car was bouncy on 40psi. On 32 psi it is much better.

BlownV8

32 PSI on 22" wheels + Mercedes GL = bent wheels. If bouncy, there is something wrong with your suspension. I'm not saying that it didn't improve the ride; rather, if it did, your suspension needs work or your wheels are crazy heavy cast wheels and your shocks/struts are fried.

Miguk_Saram

Are you referring to the air struts? Wouldn't symptoms of bad air struts be obvious in other ways? eg. sagging on the side of the bad strut?

I have no idea nor expertise regarding the bent wheels aspect; however, if it's just the ride quality, then, I am inclined to side with the OP: tire pressure issue.

That notwithstanding and to answer the OPs question: if you can get your hands on (or borrow) some stock rims (option #3), then that might provide insight as to BlownV8's suspension concern; otherwise, I too would go with Option #5

BlownV8

There is a shock/air spring setup in front and in back. Sometimes, the air spring is good but the strut/shock is bad so you get a bouncy and or car that has a lot of sway. The rear shocks go out every 80 to 100k miles and the fronts tend to fail more often. A sunk car is typically caused by a bad air spring and is not the same as the shock. Air spring controls height and the shock controls the bounce/suspension rebound speed. Leaking internals on a shock will cause a bouncy and uncontrollable ride and that's what I think is happening to the OP's car.

wenter

Have some info that might be valuable for someone.

I have installed 275-45-22 tires on my truck and those tires are too big for the front. They rub against the wheel well liner. One day after I got the new tires I discovered that I have a long crack along one of the wheel seams. Took off the wheels with tires.

Got myself a set of wheels and tires off 2012 X166. They fit nicely. Ride quality is much better. Tires are Nitto Motiva 275/55/r19

Bottom line for me: original wheels and tires works best.

I have some oil swelling on the rear shocks. They are going to be replaced in near future with Bilsteins. As for the front - I have ordered a microphone with a long cord, will zip-tie it to a front strut that I suspect makes sounds and will see if it is bad or not. If bad - will get new Bilstein front struts with air springs. Previous owned had replaced the air springs on the front and back with cheap China springs.