very good answer.
I just clicked on tire rack's site, which I have been to many times.
find a tire in the stock size, and look at it's "specs" link. Overall diameter is quite crucial...as is the section width.
then look at a "plus 0" size which means same size rim, different size tire. The first number is the tread's section width...the second number is the aspect ratio(a % of the width = the hight of the sidewall), and the third number is the wheel's O.D.(overall diameter)
so...a 215/50-17 has a tread width of 215mm. the aspect ratio is 50, meaning 50% of the tread width is the sidewall height, and the 17 is the wheel size.
select a 215/50-17
the look at a 225/50-17
you will find differences in load capacity, as well as overall diameter.
the two tires I looked at showed a O.D. of 25.5 for the 215/50 and the O.D. of a 225/50-17 is 25.9
therefore, a 225/50-17 tire has a O.D. that is .4 taller than the 215/50-17
that is measured without any load on the tire, inflated to specs, and set for 24 hours.
Now, if you load the tire(on the car, under weight) the O.D. will be reduced by 50% due to what is referred to as "static loaded radius"...the bottom half of the tire...the part that is actually under "load". The top half of the tire will not affect ride height because it has no load on it.
therefore, if the O.D. difference is advertised at .4, then the SLR or 'static loaded radius" is 1/2 that... or .2
so, a 225/50-17 is only .2 taller than a 215/50-17
it is also only 3/10" wider, which...isnt much.
hope that helps.
My next set of tires will most likely be a 225/50-17...larger footprint(3/10ths), but barely any taller, so fuel mileage, and final drive gearing wont be affected too much, if at all.
*Former Owner* of a 2006 DSM 2LT
*current owner* of a 2009 Victory Red SS