Ok so here is my situation... I am looking at rims and I have found a bunch of them, but my question is in regard to tires. What on earth do these mean:

1.) 225/45/18

2.) 215/35/18

3.) 225/40/18

Someone help me please by explain the numbers, the differences, and the best choice to make.

Thanks a lot,
The Doctor

 

Here is a nice tool to use that helps explain this madness with a visual of the difference in tire sizes. Plug in your stock size and the sizes above and you will see the result in the difference in sizes. Otherwise, to me there is no way to visualize this in your head. It all has to do with the varience in heighth of the side wall and width of the tread and some percentage part.

http://www.1010tires.com/TireSizeCal...?action=submit

 

OK, the first number is treadwidth, the second is profile and the third is the wheel diameter.

Now, to make things even more difficult, if you are wanting to change wheels, there is also the offset factor. This determines how far your wheels stick out from the hub, there are negative and positive offsets.

Here is another tool that will help you with this part: http://toy4two.home.mindspring.com/offset.html

I hope these help. :D

 

Exactly the link I was gonna post! Best tire size calculator I've seen.

But basically, the first number is the tire width in mm, second number is the height of the sidewall as a percentage of the width, third number is the size of the wheel.

So to take the third choice as an example...

225/40-18
225 mm = 22.5 cm = 8.86 inches width
(225 mm)*0.4 = 90 mm = 9 cm = 3.54 inches sidewall height
all on an 18" wheel.