Fun Fact!
Tires widths are measured on the inside of the tire. The tires width number(235, 285, 305, etc) has NOTHING to do with the tread design or width of the tread.

 

I just took off the staggered amg 18s and put on radius r15 20s.
fronts 245 35 20 on 20x8.5 and 35 offset.
​​​​​23rears 275 30 20 on 20x10.5 and 30 offset.
rides very well but when laden its touching somewhere over speed bumps or on fast bouncy Country roads.
Im prob gonna have to drop front profile to 30 and rear to 25.
Just need to figure out where its touching. Hasn't left any marks as yet in first 2 days use.

 

Overall diameter mm difference between 205 /55 / 16 and 235 / 45 /17 ?

 

Here in Hong Kong the following pictures show the usual tire size for w212(1st picture) and w213(2nd picture).
The overall diameter of w212 tires is 653mm, and w213 is 678mm, the difference is 25mm(1inch).

 

W212 wheel diameter size is 653 mm.
So you've put W213 wheel size tires into your car.

 

This would be great but in the real world tyre sizes width and aspect ratio are not produced to the precise sizes.

Big variations between brands so the calculators are a rough guide .

 

Agree.
But if comparing same tire width and tire wall, 225/55/16 for w212 while 225/55/17 for 213, w213 wheel size is roughly 1 inch bigger in diameter than w212.

 

Did you find where it scratches?
Did you change to the smaller profile tyres?
What would you recommend?
Thanks!

 

I’m also thinking of getting bigger wheels (245/40R19), but I’m unsure if 5% increased diameter (1 inch) will fit since I only have about 11 mm between the current stock tyre (245/45R17) and the suspension (see picture). I think I would need 13 mm at least. 2 important millimeters 🙁 Any ideas if this could be solved. All other margins have been checked and are ok.

 

With 25.4 mm in an inch, that leaves you 12.9 mm to fit in an 11 mm spot? those look like snow tires ?

 

Yes I haven’t changed to summer tyres yet 😅 That’s why I need to solve this now 😅

 

+2% larger is generally considered not to be a problem.

 

By the math but not real world .

Always best to stick to manufacturer recommended sizes .

 

No, I don't agree. Many vehicles spec undersize tires. Here's a good example... female friend's Chevy Traxx specs an obsolete 205/65-16, last seen on Pontiac Aztek, not kidding.

ONLY old crappy models and new crappy models of Chinese tires come in that size, maybe 4-10 to choose from.

Switched to 215/65-16 there's tons of modern tires with great pricing. It rides better, handles better and will get better wear with a tire size that looks 100% correct....for less money. Her quote was $800 for Arroyo tires, I put her on Nokian One for $350....same as I'm using on my ML 350. Going back to the classic 205/55-16, like on VAG cars, but in particular the C203 4M I bought as a gift for my cousin. Spec 205/55-16 is lame and doesn't really carry the car well at all, some 215/55-16 Pirelli P4 did an excellent job, no comparison, not even close.

OE tire sizing is a compromised process. I'm surprised someone with your level of experience would think OE size is always best. I understand the theory and god forbid, failed sizes that ruin a car, but ....that 2% rule is quite sound and often advised. In my case with the C207, I think the OE sizes are optimal. There could be room for more meat, but I'm not seeing it. Our crappy roads do call for a little extra tire meat.

I guess my 2018 Metris is another example, 225/55-17 stock is weak and lame. Anyone who would stick it out with this crippling size out of deference to the mfg deserves what they get. Newer models Metris get 235/55-17 OE on the same wheels, which are ok I guess. If I cared about handling vs the ride quality, sure. I actually had a set of 235/55-17 P7 new and mounted on my Metris wheels leftover from my GLA, which I planned on using on the Metris as my next set.....but I sold them and got another set of 235/60-17 like the Firestone LE2 I have on now, I changed to a split set, mild AT Nokian Outpost on back and Nokian One on front. Sort of a winter set so I can get up my driveway and maybe some park trials out West. The Metris is all about ride for me. If it were an SUV, I might have skipped the way oversize tires for the mid size ones.

But you see...NFW OE size is perfect or desirable at all. Sure selecting a modest upsize is a specialty skill, but it's one we should adopt and use to our advantage, not dismiss it out of hand.



I tried a few sizes on my ML, 19s and 20s but it truly sucked on 20" 265s The whole experience with steering fell, ride etc was terrible. So when I decided to go to 19"s, I skipped replacing the OE 255s already on those used wheels, and got 245/55-19. A hair taller, 10mm more narrow and one load rating higher, it rides great and has the reflexes of a hungry cat. OE size was terrible

If you were a local, I'd put you behind the wheel. I don't think you would disagree.