Divadtri

Wonder is 20 inch wheels or 21 inch wheels for summer tire , witch is more handling and comfort and better ?thank for advice.

Serhan

Mine came with 21" Conti Sport Contact 6 summer wheels, not very comfortable with AMG suspension... There are not many choices also for 21" tires. There was no all season and hardly any winter tires in stock. I went with 20" Michelin Alpin 5 UHP for winters and car rides much more comfortable... It might be 2 reasons. First, more side wall is better for comfort and Michelin tires might have softer sidewall compared to Conti. Second is softer rubber and tire sculpture for snow performance that is able soak up small imperfections in many roads; it doesn’t get transmitted to the carcass of the tire. That is why I am switching for 21" Michelin all seasons for other 3 seasons:
https://mbworld.org/forums/glb-class...son-tires.html

For tire size, you can see thinner profiles give best performance for dry roads, but reverses in wet/snow:

Divadtri

I just install 20x9 inch aftermarket with tires 235/45/r20 alls season tire Pirelli p zero , am notice driving was not very comfortable as 235/50/r19 tire there given me MB.
Performance a little good then 19.
is there possibly change larger tire on the same rim 20inch ?
like less bumpy more comfortable 245/45/r20 or 235/50/r20 bigger ratio of height with any cornering issue?
Or not i have spare money to buy new mag am gonna lower back to 19
inch…

Serhan

You can go wider tires up to 265mm with 20x9's. Usually they recommend to keep it within 3% of the diameter/height of the original tire. Any more than this and you have the risk of brake failure.

Assuming that you had 235/50R19 on your GLB 250, you can have 245/45R20 that should give 1.5% reading error and should help on cornering and comfort with higher sidewalls. You can change the sizes if I am not correct:
https://www.willtheyfit.com/index.ph...8.5&offset2=51

255/45R20 will give you 2.7% error in comparison to 235/50R19:
https://www.willtheyfit.com/index.ph...8.5&offset2=51

GLB 35 comes with 255mm tires with 20 & 21 inch rims, so 255mm wide tires should not be a problem with clearance and if you want max corner grip as long as you are good with your aftermarket wheel offset.

Divadtri

You think is better change tire size 255/40r20 will help for improve on Comfort side ?or is just improve on handling and performance, or i should stick with 235/45r20 for the comfort side? .
or just change two tire 255/40r20 on the back ? Witch is better?
or 245/45r20 ?

Serhan

They are close, higher wall will give you better comfort for the same tire...
255x0.4=102mm wall height
235x0.45=105.75mm wall height

However there is differences btw tires, eg in below video you can see how soft the touring tire compared to summer tires, but touring tire lags on performance in comparison to good summer tires. It is a compromise between comfort and performance, where you can live with... The problem is it is hard to guess unless you try the specific tire + wheel combo with your car. It is not just the tire size alone... You can read the tirerack reviews, but even those user reviews changes a lot for the same tire depending on where the user previous reference is...

I don't know why you change 2 back tires to different size, esp. when GLB is front biased. Also traction / stability control may give errors with different size tires... It is good to have 4 same size tires for rotation....