dgeesaman

iTrader: (7)

I've been puzzling over the tire size calculator and tirerack. Whenever I find a wheel/tire size that makes some sense, the tires don't exist.

Since I'm a cheapskate with tires, I want to end up with as many tire models available as possible for my wheels. R-comp takeoffs are my bestest friend. But on the other hand the point here is to cram more rubber under the wheelwells.

What have you had good experience with in 17" and 18", 9" to 9.5" wide? (I have unrolled fenders, stock shocks and trailing arms BTW). How much does overall tire diameter matter when you're on the track?

Dave

Mahjik

iTrader: (1)

Dave, I think it really depends more on you and your car. I don't plan to run more than 245 -255's on the track with some 17's. I'm just not that serious about it that going bigger is going to give me any more enjoyment. I was looking to run some Kumho V710's at 245/45ZR17 this year.

dgeesaman

iTrader: (7)

Actually the issue of wider rubber is autocrossing more than track use. I just feel I'm wasting money if all I get is a 255 width tire after spending $2k. Better to have a fresh set of 245/45R16s for half that price. I also don't plan on going big brake.

But since I get my v710 takeoffs from guys who do serious SCCA and NASA track races that's why I asked.

Dave

ptrhahn

iTrader: (9)

A 255/40/17 on a 17x9" wheel should be an upgrade over a 245/45 on 16x8" wheel. It'll be a bit bigger.

The two more popular upgrades as far as size are 275/40/17 all around, or 285/30/18 all around. I've used both (actually all four). Observations:

1. 285/30/18, while wider, may be less likely to catch your unrolled fender lip, but on the 18x10" +50 wheel you'll need, you'll need trailing arms at the rear.

2. My 275/40 setup was on 17x9.5 +42 wheels, which will work with stock trailing arms, but may be very likely to catch your unrolled fender lip.

3. Not 100% positive both won't require 2.5" coilovers.

Without all of that, a 17x9" +45 w/ 255/40/17 might be the ticket. Nothing much larger is going to happemn without compromise. I guess you could run the 255/40/17 front with a 275/40 rear and not be able to rotate all four corners.

dgeesaman

iTrader: (7)

Thanks Peter.

Since I don't want to hassle with things that may/may not clear, it seems that 255/40/17 is my next step up. Unfortunately that size isn't available in the autocrossing compounds (v710, A6) so I might need to stuff on a 275/40/17 instead. I think that *would* be plenty of rubber. My springs aren't set really low so hopefully the rolling is unnecessary, but it's hard to say.

Dave

Josh18_2k

iTrader: (3)

if you're autocrossing, 285/30/18 is probably your best bet. its about an inch shorter than 275/40/17, so you get a lot better clearance with things like fender wells and lips.
18x9.5 +45 is the common choice there. (not sure about trailing arm clearance..)

Mahjik

iTrader: (1)

I had to roll my fenders for 17x9 +43 with 255's. Granted, I'm lowered quite a bit but make sure you get some decent offsets if you don't want to roll your fenders. 275's should be fine with the stock trailing arms and without 2.5" coilovers. When I was doing similar research a few years back, 275's seemed to be the limit before needing some stock suspension parts changed out.

gracer7-rx7

iTrader: (16)

I currently run 17 x 9 +45 offset SSRs with 255/40/17 all around. Many years ago, I ran stock wheels with 245s. I have also run a variety of suspensions back to back ranging from stock to coilovers and everything in between. I have run both stock trailing arms and Rotary Extreme trailing arms. My fenders are untouched.

This wheel tire setup fits very well and does not normally rub when used on race tracks or on autox courses. Doesn't rub on the street either. The only time I have ever gotten any rubbing is when the car hits a BIG dip in the road and the suspension compresses bigtime. This happened driving in the Santa Cruz mountains near my house exactly 2 times. It never happened on track or on autox. My ride height is a hair over 25.25" up front and I'm running 450# springs up front on my Koni/GC coilovers.

My car puts down about 300 rwhp and I have not needed more grip than 255s provide but I'm not at all serious about autox

A friend of mine used to rub on autox courses on the front fender on a similar setup (unknown springs) running a 40 offset 17x9 rims.

Another friend of mine (speed of light) is currently running the same SSRs that I am but a 275 tire all around. He rubbed big time on worn stock shocks and springs. He now runs Tokico shocks with stock springs and fresh rubber bushings. I haven't spoken with him in ages but I understand that the fresh suspension pieces helped the rubbing on street use. I haven't followed up and don't know if he has rubbed since. he does not autox. The 275 look big on the car and look like they would rub up front but I don't have personal experience with them.

The 17s make a bit of a difference in transient response on street tires - most likely associated with a smaller sidewall and wider track.

In the end, its up to you and your priorities. The 17s sure do look cooler. 16" tires are definitely cheaper though.

Mahjik

iTrader: (1)

Dave,

Another option would be getting a custom steel wheel made (I'm thinking about this as well):

https://www.rx7club.com/suspension-wheels-tires-brakes-20/15-3rd-gen-694952/

They aren't going to win any trophies at a car show, but they look like a good track wheel (depending on the pricing). You can stay at 16" and just go wider.