csj0952

How many miles per galon do you lose when going from 17s to 18s?

Is it worth it in your opinion?

Tsx536

If you go with a wheel/tire combo that is close to the exact same diameter of your current setup, there should be almost no difference. 235/40/R18 tire is close the the same as stock. Check the tire/wheel master guide for more info. Even if you go with a little smaller tire I would guess the difference would only be about 1 mpg at the most.

csj0952

Then i guess I can't decide if I want 18s or 17s and what rim....

all I know so far is that I want a gunmetal rim and that these will be summer tires (i have a set of winter ones already)

I have a charcoal TSX so I figure the gunmetal will look cool.

How do i decide what's best for me...17s or 18s...and then tire size...

PJS

You grow some cojones and make a decision!
Then visit www.carbibles.com/tyre_bible.html and compare the current tyre size with the planned one and see how close to stock you are. Your speedo is over-reading anyway, so don't be worrying about a -2% difference.
But, a similar + %age means you shouldn't get pulled for speeding, unless you really were hammering on.
There's a wheel gallery in here - look in there for some inspiration as well as google and various other TSX sites where you'll find a plethora of rides with one wheel or another.
There's also a big advert on the top right of the page - he sells his wheels as well as posting images of them!

VegaTSX

Remember the weight of the wheels also have a factor in loss of mpg. If you find an 18" wheel that is heavier than stock you'll definately lose some mpg. Make sure you look for a lighter weight wheel if you're going +1 or +2 over the stock 17".

PACman

http://flickr.com/photos/bussert/sets/72057594075942570

MN-TSX

I went from the stock 17s to RonJon Inspyre 18s, and went with 215/45/18 tires to maintain the stock width and diameter (wider is not better for Minnesota winters, and I run them year 'round). The RonJons are lighter, but I would say my milage has not changed a noticable amount. The Pirelli PZeroNero M&S tires actually provide both a better ride and better handling.