[timyoyo104]

my car is 225 40 18 front. and 245 35 18 back.
if I go square with stock rim. what's the best size.
my thoughts is 235 40 18 .
any advise?

[aerobod]

The maximum tyre size for the OEM front 7.5” wide wheel is 225/40-18, 235/40-18 requires an 8” to 9.5” wide wheel.

[Jnat]

Originally Posted by aerobod

The maximum tyre size for the OEM front 7.5” wide wheel is 225/40-18, 235/40-18 requires an 8” to 9.5” wide wheel.

I think the 235/40 18 would be fine on the 7.5 inch rim, IMO...

[aerobod]

Originally Posted by Jnat

I think the 235/40 18 would be fine on the 7.5 inch rim, IMO...

It will fit, but it is not an approved combination by the tyre manufacturers. The tread will be more rounded, the risk of popping a bead due to the sidewall being angled beyond design limits and excessive centre tread wear are all possibilities. Grip compared with a 225/40-18 may be no better and may be less due to the tread not laying flat enough on the road with the pinched sidewalls.

Overall the answer is to use the designed rim width for the tyre, as specified by the tyre manufacturer.

[Maynard]

No reason to not just do staggered for the snows too, if you are going to dismount and replace summer tires. But repeatedly swapping tires onto rims can cause a lot of wear and tear to the tires. Best in the long run to get a dedicated set of winter wheels/tires in a narrower square setup (if not using the staggered ones - the diff in width isn't worth a new set of wheels)