Street Tire Class 2013

JamesShort · **Posted:** Thu Jun 06, 2013 1:47 pm

Steven Carter wrote:

....and recall that the M3 that won STU in 2013 was cammed, and no one protested. I think that says something. Not sure what exactly, but that was interesting to see.

And he probably did midseason tire testing with Pirelli too....

Ryan Holton · **Posted:** Thu Jun 06, 2013 2:07 pm

Steven Carter wrote:

....and recall that the M3 that won STU in 2013 was cammed, and no one protested. I think that says something. Not sure what exactly, but that was interesting to see.

That's pretty bold to make that claim

Steven Carter · **Posted:** Thu Jun 06, 2013 2:55 pm

Ryan Holton wrote:

Steven Carter wrote:

....and recall that the M3 that won STU in 2013 was cammed, and no one protested. I think that says something. Not sure what exactly, but that was interesting to see.

That's pretty bold to make that claim

Correction. "Rumored to have" cams, according to those at the event. And some who weren't, apparently, on re-reading the source material. :stick:

BriceJohnson · **Joined:** Thu Apr 13, 2006 7:33 am **Posts:** 2230

JamesShort wrote:

Steven Carter wrote:

....and recall that the M3 that won STU in 2013 was cammed, and no one protested. I think that says something. Not sure what exactly, but that was interesting to see.

And he probably did midseason tire testing with Pirelli too....

lol

JamesMilko · **Posted:** Thu Jun 06, 2013 11:04 pm

Bill Aycock wrote:

Lots of good stuff here!

Generally speaking, I am concentrating on raw times, as they are certainly a better gauge of whether or not i am improving, and its true, going against solid competition is a good motivator. I am, however, enjoying the PAX element of TIR as it seems to allow for a large number of competitors in different kinds of cars, and there are numerous good drivers in TIR setting a high standard.

What I tend to do is find a class that has good consistency and cars that drive similarly to yours. When I was running the GTO I used F Stock since Rodney/Art/The Westerfields were pretty consistent as a group. Now a days I use STR since there are a bunch of good drivers in that class which makes it pretty consistent overall for comparison.

Brett_Murphy · **Joined:** Thu Jan 12, 2012 2:02 pm **Posts:** 355

I think STX is getting more people. I was running in STX with a stock and worn out RX-8 with 500 wear tires because that is where the other novice driving an RX-8 was. I don't care if I win at this point, I'm just in it to have fun right now.

Once I get the car running again, I'll be back in STX, but I'll probably have different tires and a suspension that doesn't have 160k miles on it.

With that car down and the rallycrosses getting cancelled, I've been tempted to bring my rallycross car to an autocross to see how incredibly ridiculous it would be. I think it would be in STU. It is a 2004 Forester XT with stiffer springs and a different rear sway bar running on street tires.

BriceJohnson · **Joined:** Thu Apr 13, 2006 7:33 am **Posts:** 2230

Wouldn't be the first (or even second) Forester I've seen at autocross. Go ahead!

JamesMilko · **Posted:** Tue Jun 11, 2013 11:24 pm

Spinning a stock Forester is terrifying FYI.

Brett_Murphy · **Joined:** Thu Jan 12, 2012 2:02 pm **Posts:** 355

Spinning is terrifying only if you're in danger of hitting something. Otherwise, it's invigorating. I did an accidental spin a the last rallycross. I think I yelled "Wheeee!" as I was going around.

Jordan Normark · **Posted:** Thu Jun 13, 2013 5:14 pm

Brett_Murphy wrote:

Spinning is terrifying only if you're in danger of hitting something. Otherwise, it's invigorating. I did an accidental spin a the last rallycross. I think I yelled "Wheeee!" as I was going around.

I think fear Milko was referring to was of hitting the ground shiny side down, at least that's what I would be thinking about.

jeremy gast · **Posted:** Fri Jun 14, 2013 8:30 am

You all need to quit bashing foresters. There is nothing like the feeling of "jumping" one of those big pigs!!!!! and I have pictures to prove it!!!!

Brett_Murphy · **Joined:** Thu Jan 12, 2012 2:02 pm **Posts:** 355

Pre-2009 Foresters are Impreza wagons with a little taller suspension. They don't have a rollover warning like an SUV would (at least mine does not). Yeah, if you put R-comps on one with a worn stock suspension, you might roll it if you do something crazy. You might also roll a stock Impreza if you just stick R-comps on it the same way.

I guess I'm saying I'm not worried, but I wouldn't try to drive it like a Lotus, either.

Arthur McDonald · **Joined:** Fri Aug 29, 2003 1:54 am **Posts:** 2052

Les Davis wrote:

I'm personally in the camp where you can't have too much tire as long as your talking about autocross compound tires on a warm/dry day. If its cold or rainy or even snowy, narrower tires could possibly be better depending on the compound. But for your typical autocross situation, wider is always better.

Sorry to resurrect an old thread, but I'm looking at alternatives for street tires to replace my A6s. The discussion about tire width vs rim width reminds me of the exact same question I faced in FS twenty years ago. I'm leaning toward the Rival, but regardless of the tire I pick (Rival, ZII, RS-3), I have to choose between a 245 mm wide tire that will easily fit my 18x8.5 wheels, or a 265 or 275 mm wide tire that is spec'ed for at least a 9" wide wheel. Mustangs are heavy cars, so I assume I'll need to run 40+ lbs all around, as I did with my 275/35-18 A6s, which might offset some of the sloppiness associated with a wide tire on a skinny rim. What's the current thinking in this regard?

Chuck Branscomb · **Posted:** Wed Jul 10, 2013 8:56 am

Art,

I'll blab my thoughts here and answer your e-mail at the same time.

The net of the answer to rim width versus section width with the latest street tires it is "I don't know." I'm not sure many really know the answer, and said "answer" is likely multifaceted -- from a performance standpoint: (1) steady state ultimate grip, (2) transient response, (3) braking and acceleration grip; from a tire standpoint: Rival, ZII, RS-3. My thinking is that it may turnout that one tire is "better" being over-sized since it gains enough in ultimate grip while still being able to boogie transients whereas another identical size tire is "better" being sized closer to rim width = tread width (in your case 275/35 versus 245/40).

The only way to know is to take the tires in both sizes and test them. Of course it would have to be a very closely controlled test with the driver blind to what's being run. Speaking of which, I assume you saw the latest GRM mag test where the Rival shined pretty brightly. Whichever tire size you decide on, I think you'll love the Rivals...more on that in a sec. Well, I think GRM will have a test in an upcoming issue changing wheel widths with rather small size tires (but I somehow do not think it will be a worthwhile example to extrapolate into larger wheel/tire sizes). Sigh...

I doubt you'll have to run huge pressures like the A6, not with the Rival anyway. The A6 is a pansy carcass and needs a LOT of air in many cases on a stock class car -- well over 40psi in some cases, heck that Hoosier guy told me on the M5 to start at 41-42psi cold and add more if I needed it (recommended 1psi/100lbs running weight cold). Something like the Rival is nothing like that at all. I run them at 37-38psi hot pressures on the M3 with good results. Their turn-in response will shock you after having run A6s on your car. Seriously, you'll love driving these things.

On the M3, I've been using 245/40-18 all around with stock sized wheels, 8.5" front and 9.5" rear. That is the stock tire size for the M3 up front while the rears are supposed to be 265/40-18. The only place where I'm losing something on the 245s is probably on track out where more rear tire should give more acceleration grip. I went with the 245s since the 275/35 wasn't available yet (is now).

So here's my dilemma for next year: go the 275/35 in the rear and keep the 245 front, run 275s all around, or continue with 245s all around? The first option might yield more understeer and kill the superb balance the car has now on course (for a stock car with just a large front bar, I'm really happy with it's handling). The second option is the one I'm leaning toward but will going to 275s all around actually be slower on an autox course? I have no idea. I really wouldn't think so, but I have no hard facts.

I do know that the 245s on the 9.5" rear wheels feel great -- taught, super controllable, nice nailed down feeling in transients as the sidewalls are stretched a good bit (you can't lay the wheel down when changing tires as it hits first instead of the tire).

JamesShort · **Posted:** Wed Jul 10, 2013 9:08 am

My limited data/experience says properly fit to the wheel street tires (even those with stiff sidewall like ZI/Z2/Rivals) are faster in terms of times. Though I've never autocrossed a car where longitudinal traction was an issue. My biggest qualms with a wide tires on a skinny wheel is the transitional response....super slow and sloppy and it seems to add up.

Like Chuck said, this question's ultimate answer is going to require a lot of empirical evidence of which most of us don't have the time or $$$ to do ourselves

.

If Chuck can tame that M3 with 245s at all 4 corners, I'd say your Mustang should be fine.

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