18x8 vs 18x8.5? Need Help Understanding
 

I'm new to the realm of wheels, tires, etc - I've learned a lot from this forum and general interest, but I could use some help in deciding wheel size.

My car is primarily is for spirited, or weekend driving. I haven't found any wheels I really like yet until now (the new Gramlights 57Transcend), but they only come in 18" +

I would like to think that if I am going to buy new wheels, that I am at least gaining some small performance upgrade, and not simply a cosmetic one; I will probably still be saving weight with these wheels, but I really don't know what difference the 18x8+45 or 18x8.5+45 (same offset) would make for me, besides the 8.5 being a wider contact patch for slightly more grip (but does that come at a cost to acceleration, etc?)

Basically for a car that isn't tracked, I need help understanding what difference I could expect from the 18x8 vs 18x8.5 (again, offset would be the same as these only come in +45)

I've searched, and googled multiple times, but I haven't really found anything that specifically answer my question for someone that has only a very basic understanding of wheels, and tires.

Thanks very much for anyone that can enlighten me, and help me make a decision between those two (note: I'm not really interested in other wheels, and therefore sizing - I would simply like to understand the differences I can expect between these two should I choose one over the other).

the difference is..... half an inch.

You just have to ask yourself: what tire size do you want to run? Even 8" is already an improvement over stock when it comes to contact patch.

All else being equal, if you have a stock engine and this is for street use, 8" will be plenty wide for you.

-alex

Alex pretty much covered it. You won't feel any difference at all with the extra .5" width. On the 8.5" wheels, the flange will be closer to flush with the plane of the fender so it should look a little better. For the most part upgrading the wheels on your car will be mostly a cosmetic mod.

Upgrading the tire compound will give you a much bigger performance improvement than adding an additional .5" of width as well. You'll definitely feel sticker tires, but for a daily driver even that may not be necessary.

Yeah I would be upgrading the tires as well, I just wanted to be sure I understand what I'm getting between the two sizes, or where the "gain" from a wider wheels falls off and starts to compromise accelerating, etc if we're talking street use.

Thanks for the input guys - I do appreciate it.

There's no single "compromise" point because virtually every size will be a compromise between one attribute vs the other.

The main thing here is to figure out what you want to address and what tires you will want to go with, then go narrow down wheel width. Just as an example, off the top of my head here's the widths you can run with 8 vs 8.5":

8" - 215, 225, 235, maybe 245 if you want to go 4x4
8.5" - 225, 235, 245, maybe 255 if you are into boat racing

If you want to run a 225 tire, 8" will be best and it will be stretched on 8.5" slightly.
If you want to run 245, 8.5" will be best and 8" will make the tires bulge.

etc.

-alex

Ahah I have 245/40 on an 8" and it looks great to me. I hate stretch.

The stock tires fit on 8 but not on 8.5 if that matters (ie, tire spec I don't mean it's impossible)