DFWdude

The OEM tires on my 2016 are 245/40 R18 97V, non staggered. I am a long way from needing new tires, but I'm starting to consider if there is a reason not to go to 245/45 R18s. 110mm sidewall vs 98mm sidewall. 10mm is barely 4/10 of an inch.

I don't care at all for the 20" wheels on Rubber band tires set. Imma think the 45 Aspect tire on my keeper stock 18" wheels will give slightly better ride, minimal/no impact on odometer(?), and better resistance to bent rims.

Go ahead, tell me I'm stupid. In 68 years, it would only be the second time for me.

Arrie

In my car there is very little room between the tire and the bottom spring support. Mine is an AirMatic so this room may be different in your car. Other than that it makes speed meter error about 3.7% but that can be handled by driving a mile or two slower by the meter.

I purchased 17” rims and tires thinking it would soften the ride but I could really not tell any difference compared to the original 18” setup.

KEY08

You may not have as wide of a selection at that aspect ratio, but it should work. Seriously doubt if will provide any better protection however.

mo11

Nope, not stupid at all... I can totally understand wanting a more comfortable ride. However, instead of raising the aspect ratio of the tire with the same width, you can go with a wider tire with the same aspect ratio like 255/40 18. If your wheels are 8.5” width, you can fit this size tire and have a wider contact patch and gain more sidewall height. Difference in diameter is less than 3% of your original tire, which would also be a closer ratio on the speedometer. This is how I’d solve the ride issue and clearance in case you don’t have enough front suspension arm space.

kajtek1

Don't use generic calculators for tire matching as tires are manufactured with loose tolerances and you can make up to 5% error.
Go to tire manufacturer site and compare rpm.
Now talking about idea of higher tires, I keep extra set of 16" I have left from W211. Once 18" tires will wear, I rather put 16"

cetialpha5

Well the 17 rims had 245/45/17's on them. The 18 inch rims on my W211 have had bent and cracked rims. On the 17 inch rims, so far I've only had bent rims, none cracked yet. Speedometer will also be off if you use 45's instead of 40's on the 18's. Should be the same with the 17 inch rims with the 45's.

DFWdude

This is a different way of looking at it, thanks. 255/40 will add only 4mm to the sidewall height, to 102mm. This might not affect speedometer much?

How does increasing sidewall measurement affect the odometer? Will any of these solutions cause the ODO to add miles faster? I'm more concerned with odometer behavior than speedometer readouts.

KEY08

I think the 255/40 will rub up front.

kajtek1

Not likely.
My monoblocks have few mm bigger offset than original wheels, what puts the outer edge even farther where 255 tires with correct offset would put them. Visually it is close, but still plenty of clearance.

mo11

It depends on the % difference. If you max out at +/- 3%, then that would be the difference in mileage. Of course, this is just simplifying calculations to have a rough estimate. If you travel 100mi then you could be off by +/-3mi, at 1000mi it’ll be +/-30mi...

Arrie

I my car the rubbing would happen to the strut, not the fender. I’m pretty sure 255 with added width and diameter would be a problem in my car but again, Airmatic strut clearance to tire may be tighter than conventional spring has it.

mo11

You shouldn’t have any issues. A lot of w212 forum members with Airmatic have 20’s with larger diameter tires than a 255/40 18. I used to have a w211 with Airmatic, and I had 245/35 20 up front on that with no issues. I doubt the Airmatic suspension changes from the w211 to the w212 are that much different.

Arrie

I have my 245/45-17 tires on my car right now. I measured 5/8” = 15.9 mm room between the tire surface and bottom of the spring support on the strut.

My tires are half worn meaning that the new tire is 4 mm bigger in radius. The original 245/40-R18 is another 0.5 mm bigger than my 17” tires in radius so these together mean that with new original 245/40-R18 the room between tire and the strut is only about 11.4 mm.

245/45-R18 is 12.3 mm bigger in radius so in my car it would rub on the strut.

255/40-R 18 would fit as there seems to be more room for width and it increases radius only by 4 mm so that would not be a problem. But if the OP wants the change for softening the ride the wider option would not do anything.

All I”m saying is that the OP would really need to check it out carefully before buying these tires for front.

mo11

My reply to you was regarding your concern about rubbing. All I’m saying is it won’t rub on the base of your Airmatic strut, as pretty sure as you were it would because of the added width and diameter.

Arrie

No.

aquinob

I went from staggered 18's to 17" rims and a 45 aspect tire. On that year (2010) 17" rims were standard. No issues at all and rubber is cheaper and better able to handle bumps and potholes. I picked up the rims off CL from someone that "upgraded" theirs, so these were almost new MB rims. Waited about 3 years to be able to use them, but eventually I did. Handling is fine. I'm not a fan of larger size rims in general, they are mostly for show, not go.