Looks to me that the 17's would be better???

The Diameter of the 18 inch wheels are

245/35/18=24.5 inches dia
245/40/18=25.3 inchesdia

The 17's are

245/45/17=25.3
255/45/17=25.9

if you could squeeze the 255 on the rear you would think the car would be closer to the stock gear ratio. stock rear dia = 26.6"


??????????

 

The rears on my car are 8.0's.

front 7.5/17

rear 8.0/17

Just what I have read, I have not confirmed by measuring...


It would still be close.

 

You probably have more options in 17" sizes, with the choices being Kumho V700 Victoracers in 245/45/17 or 255/40/17. The Hoosiers come in 245/40/17. The Kumhos are a little bit smaller in overall diameter than the stock 235/50/17's, by about 4-5%. The Hoosiers are even smaller, about 6% smaller than stock. The resulting shorter gearing will help acceleration, but I think you'll run out of 2nd gear on some courses.

For 18" sizes, it's either Kumho V700 Ecstas in 225/40/18 or 265/35/18. Both are smaller than stock diameter, by roughly 5-6%. The Hoosiers come in 245/35/18 and that's about 7% smaller than stock. There's also a 275/35/18, but that might be pushing it for a 8"/8.5" rim. Then again, the 265 Kumho might be too wide for an 8" rim as well.

 

The tire recommended by most is the Kumho 700, the best is to get the regular tread for life, the shaved would be best for grip but you would wear them out quick. The tires should last a season of autox, just keep track of your heat cycles, not too relevant in autox but more so if you also do the time trials where you run a little longer and tires get hotter, that way you get familiar as to when you need to replace them. It is also suggested that they be stored best covered up.

The best choice is to get 17", in which case the closest match for diameter in the 45 profile would be the 245 in front and 255 in back as mentioned, the problem is that the Kumho's only come in the 245 not the 255 in a 45 profile, they come in 255 with 40 profile which would about 1 inch too small in diameter or you could squeeze a 275 with 40 profile it will probably fit but with some sidewall bulge.

So the question is since they will only be used for autox and speedometer not much of a concern we could go with 245/45 all around, the question would be does this affect the steering since the current tires are different in width??? Anyone???

 

Not in my experience:

1. Kumho Ecsta V700. A controversial tire, with several different generations of compounds already. Many folks consider them to have an inferior construction to the Victos. I think they grip well, but wear not much better than a Hoosier. They feel great on the track though.

2. Shaving. For dry track use, particularly on a heavy car such as the Z, shaving actually increases tire life by reducing tread squirm, heat buildup, and heat cycling. I've overdriven the Ecstas in 20 mins. on the track at full tread depth. They also don't like to come back. These characteristics are in direct contrast to the Toyo RA1.

3. 255's are a horrible fit on an 8" rim. I've run 255 R comps on a 17x8.5" rim, and definitely would not go any smaller than that. OTOH, Kumho 235/40 Ecstas worked great on 8.5" rims. Very little sidewall movement and laser like turn in.

jeff

 

Well, looking at TireRack it does not look like there are a lot of choices out there. BTW, a smaller diameter wheel/tire combo is generally preferable in autoxing as it gives better acceleration. The downside is if the final gearing with the shorter wheel/tire means that you would have to shift into 3rd to reach 60mph, which is generally the limit for most low speed SOLO II style events.

Anyhow, it looks like these are the choices (prices in full tread; add $20 for shaved):

17"

VictoRacers

225/45ZR17 ($137)
245/45ZR17 ($138)

or

245/45ZR17 ($138)
245/45ZR17 ($138)

or

245/45ZR17 ($138)
255/40ZR17 ($139)(tight but might be the best choice)

Ecstas
235/40WR17 ($132)
235/40WR17 ($132)
Since there is no 245 or 255 Ecsta in a 17 this is not going to be the best choice.

Hoosier (no shaving required)
245/40ZR17 ($204)
245/40ZR17 ($204)
=======================
18"

VictoRacer
NONE IN THIS SIZE

Ecstas
225/40WR18 ($175)
265/35WR18 ($185) (but will they fit??)
This combo would be push city!

Hoosier
245/35ZR18 ($236)
245/35ZR18 ($236)
Man, that is $1000 in tires right there. But for 18" wheels this is practically the only choice.
======================

Personally, I think I'd try this VictoRacer combo:
245/45ZR17
255/40ZR17

One other comment about the SCCA SOLO II rules; you can't legally run the Track with the 17" wheels since the 17's are not an option on that model. This is also true for the Performance and the 6MT Touring if the rules are strickly read. That means the 18" Hoo$ier$ are the only decent and legal choice for those cars. That sucks.

 

negcamber or anyone else,

Do you know how to get a hold of the SCCA rules without paying their $20.00 fee. So far the only information on the websites is that you must run stock wheel sizes, but I've seen a few of you mention that you must run the sizes that were stock with your package, and not just stock with the model. This doesn't make much sense if all 350Z's will be in the same class. Of course, I also realize that logic rarely plays a role in the decisions of large organizations, so that's why I wanted to check out that section about the wheel sizes myself.

Also, I've autoX'd once at a local club, and I definitely noticed some understeer. I'm thinking that wider front tires would help eliminate that, but I've heard some people say that wider front's won't help. Does that make sense?

In any case, I will probably end up going with the following:
245/40/18 in front - stock is 225/45/18
245/45/18 in back (same as stock)

Stock Performance wheels are 18X8 all around.

Of course I see there aren't any in that size at this time, but maybe that will change by the time I have enough money to do anything. Oh yeah, the only reason I wasn't thinking about those Hoosiers was because they'd be quite a bit shorter than the stocks. I guess that wouldn't really be a problem for just AutoX and track use though.

Any comments?

-D'oh!

 

D'Oh,

Yeah, some of the rules are available here:

http://www.moutons.org/sccasolo/index.html

Specifically, the rule that makes the 17's illegal on a Track is 12.4, which states:

12.4 Standard Part
An item of standard or optional equipment that could have been ordered with the car, installed on the factory production line, and delivered through a dealer in the United States. Dealer-installed options or deletions, except as required by factory directives, no matter how common or what their origin, are not included in this definition. This definition does not allow the updating or backdating of parts.

This rule with 13.4, which only allows wheels with standard diameter and width means the 17s are illegal on the Track since you can't get the 17s on a Track from the factory.

The rule is there so that competitors can't pick and choose the best parts of a model line. For an extreme example consider that without this rule a person could take a very light Base model put the Brembo's on from the Track and the taller final drive from the 5AT (which allows him to stay in 2nd at a speed where you would have waist time to shift to 3rd). This is an exaggerated example for the Z, but not unrealistic for some other model lines of cars.

 

Thanks for the quick reply.

I guess it comes down to what you mean by "the car". Since it seems very likely that "the car" will mean your particular model, and not just the 350Z in general, I can see why you were saying that mixing and matching parts isn't acceptable. It also makes sense considering your example.

Ahh well, that's life.

Thanks,
D'oh!

 

Also, consider how close they actually look at the car, when I went they didn't look that close or verified what models were there, but if the rules are there and you **** a competitor off he will probably bring it to someone's attention.

 

Usually, local folks won't protest...they might "educate" you on the rules and ask that you run in another class. But if you try to compete at a Divisional or National level, you can bet that a fellow B-Stocker will protest if you are running visibly illegal stuff. And it is amazing how quickly competitors learn about what is and isn't legal on new models.

 

D'oh,

Unless Nissan changed the specs of there cars since I last checked...the Performance you mention does not come with 8" all around. There are 7.5" up front and 8" in back just like the 17" wheels on the base model. Just thought I'd let you know in case this changes your logic in final tire size selection.

 

Hey Driven,

Where did you find that info. I was looking in the owners manual and what I see are the following options:

Front = 7.5 X 17
Front = 8.0 x 18*JJ

Rear = 8.0 x 17
Rear = 8.0 x 18*JJ
Rear = 8.5 x 18*JJ

The *JJ indicates an option (but the manual doesn't say which one). Therefore it looks like the Performance has 8.0 x 18 all around, while the Track has 8.0 x 18 in front and 8.5 X 18 in back.

Anyhow, let me know where you are looking, cuz maybe the manual is out of date or I am misinterpreting the info.

-D'oh!

 

D'oh,
You may be on to something here...but I'm not sure. Here is the deal: Everything I've read about the width of the wheels supports my statement about a 7.5" up front on the Performance and Touring. I get the information from my limited edition Z cards (#06031/10000) and even have it spelled out on the CD ROM disclosing the specs. Additionally, it only makes sense that Nissan would have a .5" variation in each of the models due to the staggered setup they run on each one. However...I don't have an answer for you on the owners manual. Quite frankly, I'd give less credence to it than the references I've mentioned. Best is to grab a calipers and check it out first hand! I have been doing some checking to find a replacement cost on one of my front wheels due to damage in a car wash and the dealer can't even quote me a guaranteed price because they say somehow it matters where it was manufactured? One place they mention is Taiwan and the other??? Anyway, I thought this may just have been due to them wanting to be sure to match the paint perfectly...if they had certain wheels made in place A and others in place B...then possibly the paint used varied slightly, and they don't want to listen to me ***** if I get an unacceptable variation. I don't know...but now you have me wondering if some of our Performance Z's or Touring models are set up with different width front wheels? I find that hard to believe, but maybe they changed manufacturers part way through???? Anyway...all I know is until I measure them myself...I believe them to be 7.5 and 8.0 front to back respectively.

Let me know if you can prove otherwise.

 

Driven,

I double checked my cards and THEY DO say 7.5 F and 8.0 R. My 2003 Z Brochoure and the owners manual say 8.0 F and 8.0 R. One of them is wrong, so you are correct about getting out the calipers. Dammit, why is life never easy!

On the other hand, how do you feel about 245 on 7.5" rims (if that is indeed what they are)?

Eh, whatever, it's not like I can afford new tires for a while. I want to upgrade the brakes first anyway (probably Stoptech 13.2")

-D'oh!

 

Well, if you're planning to burn those cruddy tires you were given with your car up anyway...go for the brakes. Personally I am going for new wheels and tires before any other pricey purchases. As far as the 245's on 7.5" I don't think it would be a problem. Now I am basing this not on a great deal of tire knowledge, but if the wheel we currently have is truely a 7.5" and it has a 225 on it...well, there is NO buldge and I don't think the addtional 20mm would be unacceptable. Hell, if you are getting the inner tire wear I am on my fronts, you may WANT a budge in order to use at least half your tread to it's fullest potential. I'll get slammed for that comment...it was more of a joke on how these current tires are crap and/or the unadjustable camber!

 

not unless you enjoy losing, IMO the 350Z needs the widest wheels available above all else to carry all that weight.

 

Unfortunately, SCCA SOLO rules don't let you run a wider wheel for stock class...unless you enjoy getting disqualified.