Trying to pick a set of wheels to work with my stock tires. But I'm confused what size of wheels would actually work. For example, wheels with FRONT 17x7.5 +48, Rear 17x8.5 +45, people say use 225 tires front and 255 rear. Also, sometime people say use 215(f), 255

 

The guide gives you a range to work with. If you want to know the "ideal" rim specs, then that would be the OEM specs:
Any divergence from this and you have to do the math to visualize what the set up would look like. For example, using your specs:
For the front, you would have 1/2" more width than OEM, so the edge of your rim/tire would come out 1/4" more than stock, BUT, you also have 7 mm LESS offset, so you can add another 0.28" (~1/4") that it will stick out, so a TOTAL of about 1/2" more that it will stick out.
For the rear, since it's the same width rim, you only need to look at the offset. Your example is 20mm LESS offset than stock, so it would stick out about 0.8" further than stock.
If you increase the width of the tire, you so by your own choice and you must understand how this will affect the handling and balance of the car because of the difference in the amount of rubber on the ground. For every larger size tire (10 mm of width of tire), half of that will protrude further to the outside and the other half to the inside.

It's not rocket science, but you have to use your head and do the math.

 

Thanks for the write-up. So let's see some real cases. For example:

WedsSport SA-90

17x7.5 +50, 17x9 +55, tire size should be 225/255 right?

Prodrive GC-07c

17x7.5 +48, 17x8.5 +54, tire size should be 225/245?

Work Emotion Cr Kai

17x7 +42, 17x8 +47, tire size should be 215/235?

Again these are all under the assumption that I want to keep stock handling and I do have stock suspension setup.

Thanks

 

How accurate it is it? It doesn't have nearly enough information to be complete. It misses at least three major factors that decide if a wheel will rub or not. It's ok for a very conservative estimate, but just because your wheel offset doesn't meet it's specs doesn't mean that you won't fit. Also just because your wheel does fit its specs doesn't mean that it will fit.

For many cases it is an ok estimate but by no means is exhaustive. It's better than nothing but there are just too many variables for any one guide to account for.

 

No, those are not quite right. You need to go back and look again. I think I've given you enough of a trial run for you to figure this out on your own.

 

Like you say, it's better than nothing. It's only a "guide" and not a "bible". Things will vary depending upon the alignment used (which end of the normal range the car has) and any odd sizing that a particular brand and model of tire may exhibit. We've seen that some stock cars will sit slightly different than another stock car, so a "guide" is about all it can ever be. A few millimeters one way or the other may be of no consequence or it could mean all the difference in the world.