What are the reasons for selecting an 18" wheel versus a 17" wheel?

I haven't been able to come up with a good way to search on this question, and what I've received from friends is none too helpful.

I have weighed a set of MR BBS (17x8) wheels with 245/45/17 Hankook RS-2 and a set of Prodrive GC-06H (18x8.5) wheels with 245/40/18 Falken RT-615. Both sets of tires are at about 2/3 life and similar rolling diameter. The BBS combo weighed in at 42lbs and the Prodrive combo weighed in at 45lbs. Both are wonderfully light, forged wheels with relatively heavy tires. I, unfortunately, haven't had the opportunity to weigh the wheels alone, but the tires come in at 28lbs.

I sacrifice 3lbs per wheel to run the 18s. Is there any reason why I should take that weight penalty just for the sake of the larger diameter wheel? I know there is an extra .5" wheel width in there, but I'm not convinced that accounts for the extra weight. SSR, for example, lists their Type C RS 17x8 and 17x8.5 at the same wheel weight.

The huge negative, beyond the weight, is tire price. It is another $30-50 PER TIRE to go with the 18" street tires (Neovas, RT-615, RE01-Rs). I have heard the 18s offer better tire selection, but at 8/8.5 wheel widths, the sizes are quite abundant. Bumping up to an R-compound there is a little variation in what companies offer the correct size in 17" vs 18", where I might choose a Victoracer on a 17" wheel and a Toyo on an 18" wheel.

Some people have said tire feedback is better on the 17", where you can feel it better. Oh, whoops, another ding against the 18...

Any thoughts?

-Jon

 

Most of us who compete and runs 18s are only running 18s so that we can fit a wide tire. 285/30-18s have a low enough diameter for us to fit without fender modification, whereas a 275/40 is too tall to fit without rubbing. It's an unfortunate limitation, because everything costs more with 18s, and we add some weight.

When I decided on my race setup, I wanted a 17X9.5 Enkei RPF-1 with 275/40-17 V710s, but I found through research that it wasn't going to fit too well. I then moved up to 18X9.5 Enkei NT03+M with 285/30-18s, and they fit wonderfully with fender rolling. My lap times are a testament to this setup working, but I don't have a comparison on my car using 17s with 275s...

 

the reason for many is running throw away hoosiers (if you can get them) for cheap, from the grand am guys. they run 18's.

on an evo, it doesnt pay, imho, unless you are running slicks.

If youre running lots of power, a big wide tire is great, but if you're moderate to low power, you may find yourself running faster laps on smaller tires.

(i did.)

 

good question, more input please!

 

I just swapped back to my 17x8 wheels for the autocross this weekend and I have a bit more perspective now: sidewall flex.

There is an appreciable difference going from 18 to 17. While on the freeway, jiggling the steering wheel with the 18s shows an IMMEDIATE repsonse with little to no wallowing. Take the same steering input, but this time with the 17s, and the car will hesitate slightly and wallow around slightly. I'm not talking about a huge difference like going from a Camry to an Evo, but it is there. I don't know what is actually a better feel, but I personally like the feel of the 18s when doing that specific test. I didn't once notice the wallowing while autocrossing today, however, so it may just be an inconsequential difference.

I just thought of another reason to go with an 18" wheel, though it is, perhaps, less applicable to the Evos: brake fitment. Guys out there doing the ultra-huge brakes need a wheel to go around it. I say this is less applicable to the Evos since they have a very capable brake system right off of the showroom floor. For a Le Mans car, though, they would be hard pressed to fit their brakes under a 17" wheel.

-Jon

 

I've heard this from many different guys running wider slicks. They say wide sticky tires kill their topend.