what is the different rim size between 235/40zr18 and 255/40zr18?

so it would just be 18x8?

The sizes you have here refer to tire size. You question was on rim size, and I don't no the width of the rim you are talking about, standard is 8" wide. If you are talking about the difference in tire height, just give me a minute to look it up, I have a chart somewhere.

Thanks A lot I have a 2006 lexus is 250 and the front wheel says 235/40/18 and the rear ones say 255/40/18 and my rims were dented so I need to get new ones. I just don't want to order the wrong ones.

Ok then.your rim sizes are the same, 18" by what ever wide. So the difference in tire height between the front and the back is .5 in taller in the back (1/2 in. taller in the back) You should be able to figure out how wide the rims are on your car but they are 18" diameter rims.

You need to dismount the tire and measure the wheel for its width. You may get lucky and have the width stamped of cast into the rear of the wheel. Look near the spokes. The issue is that you have a staggered tire fitment (different sizes front and rear). On some staggered setups the wheel widths are not the same front to rear. I do not know for sure if your vehicle has different width wheels.

The rear ones are 8.5j.. is that how wide it is?

Where did you measure from, I'm thinking 8". That would be from the inside of the bead side to side.

Ok, did some research for ya, and yes, that is what you will want, 18" dia. X 8.5" wide. So I assume you will use the same tires you have?

Thank You so much, Yeah the back ones are 18x8.5 and the front ones are 18x8. because the front ones says 8j instead of 8.5j

You going to stick with the same dimensions as what is on there? Or go 18X8.5 all around?