Tire size VS. Wheel size
 

does anyone know what the effect of varying ire size vs wheel size? EG - how is handling/response/whatever changed by mounting a 225 series on a 7" rim versus mounting a 225 on a 9" rim. the sidewalls will be angled very differently with these two combinations and i'm sure it affects handling somehow.

You're exactly right in your assumptions. A gentleman from the Tire Rack answer tech questions every month in Grassroots Motorsports and I specifically remember this one coming up recently; I will try and find the article.

If I remember correctly (I may be off) in most cases you want to keep wheel width within about 10% of tire width. A too wide tire for a given rim will result in the sidewalls not maintaining support for the tread because of their "stretch" to the wheel bead. The increase in rubber width will give no more or (usually) less grip then the correct tire width for the wheel would. For weight reasons you would like to run as narrow a wheel as possible, but still one wide enough to support the chosen tire size adequately.

There are some exceptions to this rule, namely cantilevered tires. These are tires that are designed to be mounted on narrow wheels and the rubber overhangs the wheel bead by inches on each side! Many times rules limit wheel width, so the tire makers designed tires to hang off the wheels to get lots of rubber on a narrow wheel. The tire has to be much heavier with much more structure in it, but the increased tread width outweighs the negatives. I have only seen it done on very lightweight racers, a heavier car would destroy the things easily. Keep in mind this is a solution driven by comeptition rules, the ideal solution would still be the correct width of wheel.

another side of the coin i've been wondering about is when people mount a tiny tire on a wide rim - (205 on an 8") i see this a lot in drifitng, and race cars seem to always have a wider wheel than the corresponding tire. does this affect breakaway, overall grip, yadda yadda

225 is not that much of a squeese on a 7 and 205-215 is not that bad of a stretch on a 8 inch tire (im running both for my 2 sets drift rims). I'm not sure how this really effects gripping but as for drift, its not really easier to kick out a 205, its more about the tire compound and thread pattern and tire pressure. if you do decide to stretch a tire, make sure to keep the tire pressure up. also it might be bad to stretch a 225 on a 7 inch tire but when you go thru a set of tires in about 5-10 mins while drifting hard, it does not really matter (i can't go thur them this fast but my friends can :D, it ususally take about a week or so to go thru mines depending on how long i can keep going at it before the cops come running :D)


BTW: I have seen 195's mounted on a 10 inch tire, now thats a stretch!

In this photo I had 245's mounted on 17 x 10's :) now I have 275's.... the fronts are 235's on 17 x 9's

Wow I didn't you could stretch a 245 to fit on a 10 wide! Same with 235 on a 9 wide!

thats a 9 inch wheel on the front? (silver FC) i thought 8 was about as wide as you could go... or is that just without coilovers. im planning on 245 front and 275 rear, but i gotta figure out what size wheels i want