Tire sizing...

Post by **Mill3niumThr33** » Mar Tue 04, 2008 2:27 pm

What will the difference be between 235/40/17 and 225/45/17? Will the 235/40 setup be more rounded on the sidewall or will it be a more 90 degree angle sidewall like the 225/45? I suppose it depends upon the tire design but I am just trying to picture what the difference is. Which would you choose to run Joe?

Post by **ValveFloat** » Mar Tue 04, 2008 2:29 pm

Mike, I think you are confusing width and diameter.
245-40-17:
17 is the diameter of the wheel in inches
245 is the width of the tire in millimeters, it represents the width of the tire as viewed from the front or rear.
40 is the sidewall height in percentage of width, so 40% of 245 = 98mm.
The overall diameter is determined by adding the two sidewall hieghts to the wheel diameter.

So, when you go from a 225-45-17 to a 245-40-17, the overall diameter is about the same but you gain 20mm (0.787") in width.
More info and an image.

What width wheel you put the tire on will effect the actual tread width of the tire some. Like putting a 245 on a 9" wheel will put a little more of the tread width on the ground than a 7" wheel will. But in the end, if you compare tread width of a 245 vs. a 225 on the same wheel, the 245 is going to have more tread width, which means a wider contact patch, which, everything else being equal, means more cornering grip.

Post by **ValveFloat** » Mar Tue 04, 2008 2:39 pm

Mill3niumThr33 wrote:What will the difference be between 235/40/17 and 225/45/17? Will the 235/40 setup be more rounded on the sidewall or will it be a more 90 degree angle sidewall like the 225/45? I suppose it depends upon the tire design but I am just trying to picture what the difference is. Which would you choose to run Joe?

That is kind of a tough one.
For a 235, the minimum wheel width recommendation is 8", not that that would stop me from putting them on a 7.5.
The 235 is going to look slightly more "chunky" on the 7.5" wheel than the 225 will, if you know what I mean.
On your car though, as low as you are, the slightly (very slight .25")shorter sidewall, and extra width might look better.
What offset are your wheels? Any concern with tire to front fender contact?
If that is tight, the 225 might be better.

:edit: Another reason to go with the 225-45 is its a more common size, more choices, cheaper...

YouTube · Post by **Mikewire** » Mar Tue 04, 2008 2:42 pm

See I was confused - doing the math in my head I had the width and sidewall % switched around

...yeah

. Back to wheel school for me. Thanks for clearing that up for me, and hopefully that tells Wade what size to go with if he wants "more" tire.

Post by **Mill3niumThr33** » Mar Tue 04, 2008 3:08 pm

I think I will end up with the 235/40/17 BFG KDW2's. I originally ran 225/45/17 with no fender or strut contact issues whatsoever and I was under it quite often. I am running 35 offset 17x7.5 with 205/45/17's right now so it will be a huge difference to me. They were free so I couldn't turn them down but the runflat aspect and how teeny they are is getting to me now. Not to mention one of my tierods needs replacing and did a number on my front left before I got around to doing it.