chamois

iTrader: (2)

I have a set of 05 enthusiast 17" rims and the current set up is 225-50-17 F and 235-50-17 R. I have been using these rims as my winter wheels for now but as winter is coming to an end I wanted to use them for Auto X, what would be either a good set up for racing or what is the widest set of tires and and the side wall size i can get w/ these rims?
Thanks, Jim

sk26dett

iTrader: (16)

I've ran a 245/45/17 up front and a 255/45/17 in the back with no problems. Depending on the type of tire you could maybe run a 265 out back but it's not "recommended". Since your gonna auto x on them i wouldn't go too wide and risk having a problem. I would run the 245/255 set up, or maybe 245's all around.

dkmesa350z

iTrader: (41)

+1 I was going to suggest 245/45 255/45, that is probably ideal

z-u-later

iTrader: (43)

For autocross, I've mounted 275/40s on four (4) 17x8 stock rims. If you still have the 17x7.5 in front, you can mount 255/40 on them without issues. With the 275s, I had plenty of grip but the tires with stock rims were heavy. If you want to go faster, mount 245/40s on all four rims and call it a day.

chamois

iTrader: (2)

Would a size 40 side wall be too small to run? btw i have stock suspension height.

terrasmak

iTrader: (8)

Why would you care about the tire looking small, function > looks.

chamois

iTrader: (2)

Im talking about would a smaller side wall lower the car too much??? i really dont care how it looks im just trying to find a set of R comp tires that will work with 245 and 255's

SniperHunter

iTrader: (9)

Wrong.

Going from a 225/50-17 to a 245/40-17 would give him an enormous error of 4.4%. Going from a 235/50 to a 245/40 would make it an error of 5.8% - and that is grossly out of spec.

You are not supposed to be more than 1.5% out of OEM spec with tires.

The correct tires to upgrade would be:

225/50-17 -> 245/45-17
235/50-17 -> 255/45-17 or 265/45-17

All with less than 0.8% error.

TheBlackPearlZ

iTrader: (15)

can you really get a 265 on the rear of the oem 17 inch wheels??
that would be awesome

SniperHunter

iTrader: (9)

You can, but I wouldn't suggest it. 265mm = 10.5 inches on a 7.5" rim. Ideally, you'd want to stick within, I believe, 1.5 inches when widening tires.

terrasmak

iTrader: (8)

Doesnt really matter, you also kinda have to base yout itred decisions on what you can get for R compounds when your running a roadcourse or autocross. Big difference between the street.

z-u-later

iTrader: (43)

No, you're wrong. Quit freakin' giving advise (I've read your posts all over this forum and you're a joke), especially if you do NOT have any experience on what you're talking about. OP wants advise for an autocross setup and I gave him one BASED on experience. You're post is based on your opinion (and that's all it is), NOT on experience.

I have a set of 275/40s mounted on 17x9 rims with no issues. I also have a set of 245/40s mounted on 18" track rims with no issues. I've driven both sets on autocross and on the road with no issues. And my Z is lowered and is about 3" off the ground. Again, no issues.

chamois

iTrader: (2)

ok so i should try to find a tire w/ a 45 side wall or can i go with 40? im thinking i wanna go somewhere around 245 and 255 or 265 with the width.

Spike100

Your first message (Post #4) on this thread states:
You didn’t mention that your 245/40 tires were on 18” rims. I think that is the issue Arnie is addressing. I was confused as well since this size would be so wrong for a 17” wheel.

--Spike

Spike100

I think you are still confused on what the 40 or 45 value signifies.

The metric tire sizing system represents a tire size as:
[section width (mm)] / [aspect ratio] - [rim diameter (inches)]

For example: a tire size 225/45-18 is 225mm wide, has an aspect ratio of 45 and fits an 18" rim (wheel).

The aspect ratio (the second number) is not a measurement. The aspect ratio represents the tire's sidewall height as a percentage of the tires width (section height divided by section width). In the example above, the sidewall height is 101mm (101/225=45).

The aspect ratio is important since that (along with the wheel size) determines the overall diameter of the tire allowing you to match your stock overall tire height (diameter). For example, a 225/45-18 tire's sidewall height is 101mm, and a 245/40-18 tire's sidewall height is 98mm. So, both tires have nearly the same overall diameter.

Arnie tells you the correct tire size for your 17x8” wheels.
I’m not sure that you can find a 265/45-17” tire though.

--Spike

SniperHunter

iTrader: (9)

We were talking about 17" rims, and now all of a sudden you say that you had that tire size on 18s? Make up your mind. Autocross or not, an error of ~5% is still huge.

Spike100: Thanks. And yes, you're correct, 265/45/17 doesn't seem to exist. 265/40 does, though. Heh.

terrasmak

iTrader: (8)

Error doesnt matter as long ast its the same front to back on a VDC car. Even with a VDC or TCS car, it gets turned off at the track anyhow. I run 275/40-17's in the rear with 255/40-17's on mine. The smaller tire actually helps acceleration, and i dont car about the error for autocross or roadcourse.

Spike100

I think part of the confusion here is the OP asked about tires for autocross. That makes his question very different than if he asked about tires for street use (which is the basis of your advice for correct sizing according to Nissans’ specification).

I realize that the responses from terrasmak and z-u-later may sound incredulous to a “civilian” who doesn’t track their car. But, in fact, these guys “break the rules” looking for best results on the track. They were answering the OP’s question which was selecting tires for autcross or roadcourse.

terrasmak points out an important consideration: You may need to deviate from Nissan’s recommended tire size when going for optimum tire construction and tread design.

z-u-later points out that tires for the track might be sized very differently than stock tires (height and widthwise). Guys who track (like z-u-later and terrasmak) look for different characteristics than we want for street use. They experiment with various sizes to gain things such as better turn-in, improved acceleration out of turns, etc.).

--Spike
_________________

EDIT: terrasmak, just saw your last message above the one I was busy composing in answer to Arnie's comments. I believe Arnie was talking about street use, but that really isn't the OP's question (which is what you and z-u-later answered). Did I get it right?

davidv

iTrader: (2)

I think the tire compound would have a greater benefit than an additional 10 or 20 mm.

SniperHunter

iTrader: (9)

Spike100: You know, I just realized the OP said AutoX. The Smart Ad feature on the forum separated "Auto" and X, and I just thought he wanted new tires for his auto (car). My bad.