As I mentioned in the other post I'm dropping my car before I lay out $$$ for rims and tires. I want to be sure of my clearances.
But if you're buying wheels this week this is what I would do. Take your car to level ground and crank the wheel all the way to the right. Measure the inner fender well clearance remembering to realize that you're lowering the car later on. Then crank it the other way and measure again. Then double check all measurements.
Now you have an idea of what you have to work with. Now go to one of these websites and play around with wheel and tire combinations. Remember that the diameter has to stay close to factory or your speedo won't be calibrated correctly.
Tire Rack
Tire Size Calculator Program
Remember tire diameter has to be really close. They also use a measurement of revolutions per mile which is more acurate. The second website will actually tell you by how much your speedo will be off by the differance in diameter or revs per mile.
So now you have an idea of what you can fit. Take the clearances you wrote down and throw out all the numbers but the smallest. This is your tightest clearance and is what you will work off of. Now subtract the minimum clearance you want to remain(I used 1/2" when calculating mine. A 40 or 45 series tire will lean over alot less than a 60 series). The tire that you want can be twice the remaining clearance wider than you currently have???
{EXAMPLE: Your closest measurement was 1". You want 1/2" clearance minimum so you're left with 1/2". You multiply 1/2" x 2 and you get 1". A 1" wider tire will have half of the added width to the inside and the other half to the outside. So your new tire can be 1" wider than your current tire and it should fit safely.}
So go to TireRack and find your old tire specs. Find the section width. Now add your allowable width addition to that exsisting width. All tires are not equal, those with the same sizing are close but not equal. I looked over a bunch of tire specs and found that it could be as much as an inch wider or narrower. The sizing standard probably allow for up to 1/2" so one manufacturer goes 1/2" smaller and the other goes 1/2" bigger and there is now a pretty sizeable differance in widths. Now look over the available tires and check they're specs to see that it's within your allowable width range.
Also remember the wheel offset. From the Ultimate Camry FAQ I saw that your wheel offset is +38mm. If you get a wheel with a different offset it will alter your calculations. Getting a larger offset will allow you to have a wider tire. Getting a smaller one will cut in to your clearances.
Remember just because a 245 40-18 fit on another guys gen 4 doesn't mean it will fit on yours. Maybe his 245 40-18 has a section width of 9.5 and the 245 40-18 tire you buy has a section width of 10.5 inches. Or maybe his rim is narrower than yours thus bringing down his section width. Or maybe his offset is 50mm and yours is 38mm. Remember every one and they're momma can give you suggestions, but you have to make the Ultimate decisions.
Good Luck,
Mike
Whew,,,,,, I've been looking into my wheel and tire mods and my brain was getting over loaded. It always feels good after a nice purging. Hey,,,,, my head feels lighter.
Oh Oh,,, what's my name??? I think I purged too much......
18" Rims.....on Gen 4.5 (tire/rim width on the front)
Im goin 245-40-18 in the back for sure, gotta measure the front, nothin smaller then 225 tho 
Linear Mode
