KazzEvo8

iTrader: (2)

I know this gets beaten around a bit in a variety of threads, but thought I'd try to put a single post up to get this cleared up and closed.

Some of this is about inherent handling characteristics of a larger vs. smaller wheel.

Some of this is about how much contact patch can be put on the road.

In may case, there is some hesitation in rolling the fenders. I'll do it with empirical evidence to do so, of course. But what I've seen all seems anecdotal.

I'm running 17x9s and local auto-x courses are smallish, almost never needing 3rd gear. I don't foresee going national, etc. So I'll likely be relegated to this kind of setup.

I'm going road racing this year, however. I'm not afraid to get the right tools for the job should they differ. I know the rubber needs to differ, usually, but I'm more interested in wheel size in this thread.

17x9.5s can be had. 18s that don't force rolling of fenders can be had. There's some discussion that the contact patch, with the vehicle in a static state and comparably inflated tires never changes in size, just shape: the wider the tire the wider (and shorter) the contact patch.

What actually works? Personal experience preferred here, people.

Thanks!

Balrok

iTrader: (15)

Most all configurations "work"....depending on suspension setup, weather, track condition, and tires used. For most of us road racers, the wider R compounds and especially when you get into full slicks are made only in 18" sizes due to the uber car series using 18's and being sponsored by the tire manuf's. And the only way to really fit these wide rubbers is with 9.5+ inch wide wheels. So the debate then goes into straight line speed VS. grip in the corners - as you said. But again, most of us are at the mercy of the tire gods.

griceiv

iTrader: (2)

there's really only 2 choices for tires from a performance stand point.
245/40-17 or 285/30-18

245's if you don't want to roll your fenders, 285's if you do.

we could argue the merits of 255's and 275's all day but the only compelling data is that the shorter tire (245 and 285) will give you better straight line acceleration due to gearing and will likely provide better performance overall (aka lap time) than the incremental increases in lateral grip from a marginally wider tire until of course you reach the 285's which are wide and short.

Bueller

iTrader: (1)

What actually works? That depends on who you ask. You need to figure out what you want to do. Are you going to compete in a particular series? If you are, then its quite simple. Read the rules. What rules are you governed by? Are you limited to certain sizes? Its really not complicated given that perspective. I want to run in, blank. Here are the rules. This is what im limited to. Therefore, this is what i need to buy.

If youre just a weekend warrior, its a whole other story. You can go the cost-effective route and buy what you think will be inexpensive and rewarding for your needs. Then, someday you may outgrow your setup and decide to sell your wheels to buy something that suits you better. Or, you can try to think ahead and buy what you think you will need later and spend the money now. However, you may regret it someday realizing that you would have been happier with something else. You will never really know until you cross that bridge. Good luck figuring it out.

KazzEvo8

iTrader: (2)

Thanks very much, Ed! Definitely a weekend warrior for now.

Now, to the 245/40-17 vs 285/30-18 discussion: which width wheel fits each best?

Thanks.

griceiv

iTrader: (2)

up to roughly a 9.5" for a 245 and 11" for a 285. although most run smaller than 11's for fender clearance issues. we (and many others) run 18x9.5 with the 285's.

redvolution

iTrader: (3)

I disagree with this statement. The Evo is already geared too short for the 3 road courses here in NorCal and using a 245/40 only exacerbates it. I absolutely recommend a 255/40 over a 245/40 also because 255s are sometime underrated. For example, in terms of actual treadwidth, the specs for the Toyo R888 show the jump from 245/40 to 255/40 to be the same as the jump from 255/40 to 275/40.

I prefer 17s over 18s due to cost.

griceiv

iTrader: (2)

the speed difference between a 255/40 and a 245/40 is 2mph at the top of 5th gear(non mr). I'd surprised to seem many people taking advantage of that speed differential.

Bueller

iTrader: (1)

If you want to run 275s/285s, the typical wheel of choice is a 18x9.5.

boomn29

iTrader: (47)

I've been waiting to start a 17" vs 18" thread myself for the road course - thanks!

Let me throw another cog into the realm - <b>weight>/b>.

I do agree 18's give you more options, but I'm concerned about the extra rolling weight. It's easy enough to find rim weights (if they're accurate), but tire weights are difficult to find.

So far, I've only ran 17's, but I haven't made up my mind yet for 2009. I want the ability to run a 275 (NASA TTA probably) and a lot of people don't like the 275/40-17 option from what I've read and prefer the 275/35-18. Cost is a player hear to be sure in the debate.

Oh, and I have a spreadsheet with tire patch (TW, SW) put together if anyone wants it.

ForcedFedRS

iTrader: (23)

I think most road racers will take more rotational weight with the 18's in exchange for the larger contact patch. This is not true for all, but almost everyone I had talked to in the past had switched from wide 17's to 18's.

I personally find myself faster by a few seconds from my 17's to 18's, mainly because I can carry far more speed in turns without breaking the tires free.

boostdtalon

wow great thread, i've been debating this and this is the kind of information and opinions i have been looking for. ive been considering what tires and size i should get for the upcoming season. as i have 17x8's and 18x9.5's. i'm personally going to go with 245/40R17 as my fenders are not rolled.

cij911

iTrader: (14)

Why would a 17X9 have a different contact patch than a 18x9 ? Or are you saying that it is hard to find a 17x9.5, so therefore go with a 18x9.5?

I thought I was going to go with 17x9 or 17x9.5 to save weight (and cost), but am open to 18s if there is a real performance edge. Please help and explain...Thanks

Bueller

iTrader: (1)

^^^
In actuality, its quite simple. I already noted this part in my preceding post, but ill say it again. If you want to run 275/285 sized tires, the typical wheel of choice is a 18x9.5. Why? In no special order:

- Compared to 18x10s, 10.5s, and 11s, they are inexpensive.
- They are available.
- They fit with not much work.
- And if thats not enough, the real simple response is, that size works.

If youre a weekend warrior, and youre not interested in running tires in that size, and if you want to save some money, buy some 17s. There really isnt much else to it.

borievoinitialD

iTrader: (12)

good info on this thread...