so am I reading correctly that max tire size is still only 255's for STR but STX (2WD) max tire size is 265? Kinda confused, but man I just bought 265's this year!

This class would defintely be good for us street tire guys.

 

bump for anybody thinking of STR......

 

255 is still the limit for STR as far as I know.

BTW, I just got home. Are the results up yet?

*EDIT* They are up!

 

Yes, 255 width tires and 9" wheels are max for STR.

With those kinds of numbers and the other ST allowances, it's going to be a game of lightness, meaning the Z is at an inherent disadvantage (compared to the NC Miata, S2000 and MR-S) from the outset. But it's what I own and what I fit into physically, so it's what I'm prepping.

For reference, my car (2003 enthusiast) with a suspension and 17" SSR wheels/trunk/spare/tools stripped, custom Y-back (very light, basically a straight pipe) and 1/4 tank of gas weighs in at 3,108lb.

Still have battery, I/H/E, cats, maybe a few other weight savers. Will be very lucky to get it below 3,000lb. Going up against 2400-2500lb miatas, 2600-2700lb S2000s, etc. Could definitely use another 30mm of tire, even on a 9" wheel.

 

yeah. I'm thinking of STR as well but that means I need to get a whole new set of wheels and tires (17's) which will be $$. But depending on the driver I've been able to hold miata's and S2K's in my region so I'm game.

There's a thread over on scca talking about this as well:

http://sccaforums.com/forums/thread/370380.aspx

Guitarist keep us updated!

 

Will do...I have my first autocross in mostly STR trim this weekend. Will report on general feel, relative times to the STU crowd (which is pretty big locally, and a decent rabbit for STR raw times), and relative times to any street-tired S2000s/Miatae that show up.

That's my thread over on SCCA Forums, and it's pretty much dead, so if anyone else has suggestions/is working on a 350Z STR setup, post up, maybe we can save each other some development time/$$$.

 

curious to what wheel/tire setup you're running? Shocks/springs?

Well, what's your setup lol.

And I'm wondering if there's anyway to protest for a 265 max width? So I don't have to buy new tires

 

This question may be a bit nieve, but why not run squared 17 x 8.5 if youre limited to 255 tread width? 255 fits no problem onto an 8.5" wheel and save weight to boot.

 

Doesn't sound nieve to me... assuming that these wheels will be dedicated for AutoX and only for STR use.

My only issue is I hate to buy stuff that is less than optimum and can only be used successfully in one dedicated place.

 

The 255s would work better on a 9" wide wheel and some with section widths over 10" would work a bit better on a 9.5" wide wheel (depending on actual tread width), but that wheel width is not legal for STR RWD cars.

 

Well, for better or worse I'm running 17x8.5" SSR Type C-RS wheels because I got them on a killer closeout at TireRack. ~17lb each and wide enough to make use of the 255/40/17 Kumho XSs I have on them.

Shocks are TrueChoice Koni DAs up front with plain ol' Koni Yellows in the rear. Springs are 650lb/in front, 500lb/in rear, with the fronts being coilover and the rears on adjustable spring perches.

Stock ride height (this may change, but right now, it looks like the suspension will work better at this height and I'm not convinced the lower ride height will make significant advantages to center of gravity or roll center. People forget you change the effective wheel rate a bit when you change the suspension's starting point because the lever arm is already part way through its range of motion.

Anyway, this is just a baseline setup. I still need to get weight out, add some power, tune the car to bump rev limit to 7,100rpm or so, find a way around the retarded throttle cut under left foot braking (other than pulling the brake fuse), and do a few other things to make it max prep.

Also looking into aero somewhat, though this is sort of a black art in solo, and it's also kind of frowned upon by the powers that be. Whatever, if the rule book lets me do it, I'd be dumb not to, right?

 

Honest question, how would they work better on a 9 vs an 8.5 if youre within the tires recommended wheel widths?

Is this a stretched tire vs muffin top debate or just differences between tires recommended specs?

I run 245/255 on my stock wheel which is why I'm curious.

 

Another good choice for 8.5" wheels...2 sets of Rear 03-05 Track wheels...

 

That's also what I'm looking at (except in a 17x9) as a different option than the Enkei's. I'm also looking at MB motoring wheels which would be significantly cheaper (but about 4 lbs more per wheel).

That's what I'm running now. But if I need new tires, might as well downsize and get new wheels as well to save mass and cost. Then I'll sell my current wheels to recuperate some money since it's harder to piece together 2 sets of rears.

 

Before my ABS control module chewed through a large chunk of my savings, I was looking at the 9" MB's too.

I still might sell one of my SSR sets and get them anyway.

 

Per Jeff Speer at Hoosier Tire (and a couple other tire engineers I've talked with over the years) a radial tire will provide its best grip and response when the wheel rim is equal to or at most 1/2" wider then the actual, measured tread width (not what's printed on the tire - there's a difference).

There are some specific exceptions to this (cantilevered slicks for example) and bias ply slicks work better on a rim that's a bit narrower then the actual tread width.

The "recommended" rim width range you see in the tires ads and specs are a DOT standard based on safety, not performance.

 

Did anybody else notice that in order to run 255's on 17" wheels, our cars will be 3.85% off with a 255/40. For it to be close to stock it'd have to be a 255/45........

That means I may have to stick with 18's just to keep my gearing and speedo correct.

 

The gearing change might be an advantage and you don't need a speedometer on an autocross course. :-)

 

Not when you're already bouncing off the rev limiter at every event. Smaller dia tires will give me higher revs right?

Plus I'll probably only have 1 set of wheels/tires so I don't need the extra miles when driving on the street.

 

shorter tire will equal LESS revs meaning less speed in each gear
you're effectively running a shorter final drive ratio by running a shorter tire, and those with the DE engines def. do not want tha