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2025 Range Rover, 2022 BMW M850 , 2017 MB E400 Coupe
Tire size question
Hi.
My E250 has 18" wheels with 245/40/18 non run flat tires and I'd like to change it to 245/45/18 to have a better smoother ride. I know I can do if I'll put 17" wheels, but I'd like to keep my 18"s.
Has anybody tried to put 245/45/18 tires ? It is only 5mm difference, but will it rub ?
Hi.
My E250 has 18" wheels with 245/40/18 non run flat tires and I'd like to change it to 245/45/18 to have a better smoother ride. I know I can do if I'll put 17" wheels, but I'd like to keep my 18"s.
Has anybody tried to put 245/45/18 tires ? It is only 5mm difference, but will it rub ?
Thank you.
The difference in diameter is almost 1" (or 25mm), not 5mm (25.7" vs. 26.7"). And yes, it will rub on non-airmatic W212 (like E250).
And for future reference, the 40 or 45 refers to the aspect ratio, it's not a measurement in MM. The 245 is the measurement in MM. So a 40 means that the sidewall is 40% of 245. So if you go up 5%, that makes it an extra 5% of 245 which is 12.25, double that to get the diameter and 24.5 is about an inch taller.
You can still use 18" wheels with 235/45-18 tires which will fit and will satisfy your requirements.
The OP wants taller side wall so if you keep tire diameter the same (or close to it) and the rim the same 18” going to narrower tire with higher aspect ratio does not help as the side wall will remain the same height.
17” rims will give 1/2” more rubber and I did this as I wanted to soften the ride but the difference is very minimal if at all softer. And I use the same tire from the same manufacturer on both 17” and 18” rims.
I think the extra 1/2” wall height does give some more protection for the rims though.
I think the the best way to soften the ride is to get tires with weaker side wall stiffness but this would negatively affect handling.
Then going even smaller 16” rims could help if they fit. I know 17” is smallest that fit on my E550 but I don’t know how E350 is.
The OP wants taller side wall so if you keep tire diameter the same (or close to it) and the rim the same 18” going to narrower tire with higher aspect ratio does not help as the side wall will remain the same height.
Are you serious about it? The original tires (245/40-18) are 25.7" diameter while 235/45-18 are 26.3" to 26.4" (depending on tire manufacturer). He's gaining over 6/10" in diameter or 3/10" per sidewall while retaining the ability to use original 18" wheel. While 245/45-18 would yield 5/10" in sidewall hight, they do not fit. OP knows he can go to 245/45-17, but probably prefers staying with 18s. Your reply suggests that 245/40-18 and 235/45-18 have the same sidewall hight. Can't you do basic math or you just do not know how to get to sidewall hight? FYI: sidewall hight = section width * aspect ration / 2540. Very simple.
Are you serious about it? The original tires (245/40-18) are 25.7" diameter while 235/45-18 are 26.3" to 26.4" (depending on tire manufacturer). He's gaining over 6/10" in diameter or 3/10" per sidewall while retaining the ability to use original 18" wheel. While 245/45-18 would yield 5/10" in sidewall hight, they do not fit. OP knows he can go to 245/45-17, but probably prefers staying with 18s. Your reply suggests that 245/40-18 and 235/45-18 have the same sidewall hight. Can't you do basic math or you just do not know how to get to sidewall hight? FYI: sidewall hight = section width * aspect ration / 2540. Very simple.
Sir,
i did not not do the math. Just assumed nobody would go with so much wrong size to put speedo off. Thought the diameters are the same.
But it the point is this change won’t give any softer ride. Need to go with softer side wall tires scarifying handling.
Mine is the same 245/40-18 as yours, W212, but E400. Would be identical to yours if you are also using steel spring.
This is the spring lower holder distance to tire.
No AMG unfortunately, and we'll just leave it as that
If you are still undecided, be aware that different tire brands and models will have sidewalls of different stiffness. Thus, not all 245/40-18 will ride similarly, although most will have similar fitment. Some will ride smoother, and/or quieter than others. Generally, sportier “summer” tires will be harder riding and noisier. Try reading some reviews to get a feel of what’s out there.
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