17x9 -VS- 18x9 Square
 

I'm debating between these two sizes for next spring.

17x9 +35 w/ 245/40r17 or 255/40r17
18x9 +35 w/ 245/40r18 or 255/35r18

Both have their pros and cons but which one should I go for and why?

18X9 looks\performance slight weight difference.
17X9 performance

I'd say 17s, generally it will weigh less overall, and will be cheaper! But if you don't care about performance much, 18s will probably look a little better.

The 18's will look nicer, but for me, I'd go with 17's because they weigh less and the thicker sidewalls mean that road imperfections won't be as rough on the ass bones. In the end, go with what your gut tells you, you are probably leaning more towards one or the other. Go with your stomach, it's hungry.

I compared Enkei RPF1's in 18X9.5 and 17X9 and the weight difference isn't too much, a couple pounds. The size of the wheel though on the other hand creates more rotational mass which might actually make the car work a bit more to get the wheels turning. Not sure how accurate that is, but it seems to be the case.

I'd go for 18", however tires should be 245/35/18 if you want it as near as possible to stock diameter

Well, I'm all about doing things classy but functional. I'm sort of leaning towards the 17's as they'll be lighter and cheaper to run for the long term. They just don't grab your attention as the 18's do. The 18's look quite a bit nicer but at the expense of weight and the cost of tires can be signifcantly more.

My car is a daily driver that may see a small amount of lapping days per year.

This

I picked 18's because 17's don't look big enough in my eyes for the car.

I'm a meaty tire kinda guy.

It'll help a lot if you list what you plan to do with the car, and also what you feel the pros and cons are for you.

If you want pure performance for a time attack type situation, you're better off with 8" wide rims with 225's.

I'm not a fan of buying twice. An 8" width rim with 225's?! Might as well just keep the stockers lol. Sorry but that's not what I'm looking for. Even if I was time attacking with the stock car, I would just stick with the stock wheels and wrap them with sticky 225's

The car will be a DD with little track time. Eventually, it will be turned turboed so may as well go for the wheel size that'll accomidate that. Plus, 9" width on all four corners looks business. I'd rather have too much grip than not enough.

I guess I can say that the cost of tires is pretty important to me when talking long term. A 17x9 with a 245 would probably be most economical in terms of performance per dollar. But 18"s look more satisfying. That's the delimma I'm having. Aesthetics versus running costs. I may not be satisfied with the look of a 17x9; whereas, 255/35r18's can rack up a tire tab quite quickly.

I may have to flip a coin with this one. The votes so far are pretty even too lol.

^^ Wider != more grip... sticky tires need heat to generate full grip, and going too wide can actually give you less grip because they won't get warm enough. My 17x8's with 225's weigh less than stock, and are WAY stickier, plus a 225 will perform better on an 8" rim than a 7" rim.

IMO, forgetting budget, you should go for the 18's since you seem to be looking more for how they look than ultimate performance on a track.

If you want to consider the long term budget, your best bet is to get a set of 17x9's for track tires and then whatever you think looks good for the street with average summer tires. Sticky tires won't last that long at all (I'll be lucky to get two summers out of my ZII's at about $1k per set), so factor that into long term costs as well.

And if you choose a high tread life tire over 300 rating like a MPSS you'll be smarter money up front to just something else to consider either way you go.