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Old 07-05-2009, 09:54 PM   #1
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Default good autox tire setup

So I *may* be able to buy a set of dedicated autox wheels/tires here soon. Maybe. One thing I notice is that for a 15" wheel (8 or 9 inches wide), I can run from as skinny as a 225 to as wide as a 275 (with a few mods to the fenders), but the tire companies I'm looking at on tire rack only seem to offer 225s and 275s, with no middle ground in a 15" diameter tire. I'm looking at DOT slicks (Hoosier A6, Kumho 710, BFG R1, etc.)

So, my questions:

- Is there any good reason to run a 275 for my use versus a 225?

- Has anyone found a 235, 245, 255, or 265 width DOT slick in a 15" diameter?

What I decide for tires will ultimately impact my wheel choice, since if I find there's no reason to run a 275, then there's no need for a 15x9 wheel, I can save the cost and weight over the equivalent 15x8.

TIA
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Old 07-05-2009, 10:09 PM   #2
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emilio talked me into the 9'sfor the track because the contact patch is better and there's more grip than with the 8.

I wouldn't want to pull fenders to get huge 275's on an NA.
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Old 07-05-2009, 11:56 PM   #3
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Only reason to spend over 1k in tires is if you are building a SSM/CSP car to be competitive...those hoosiers are not cheap.

Or you just have the money to spend.
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Old 07-06-2009, 02:14 AM   #4
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225 or 275 are pretty much it for 15" rims unless you are interested in 13" 255s. Be careful about running slicks, they put you into the EM and XP class where you must have an approved rollbar installed.
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Old 07-06-2009, 02:33 AM   #5
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Hustler - Interesting. Even for 225s?

Mania - If I'm going to have dedicated tires, they're going to be grippy. I miss my 13x8 225/45 Hoosier S03 days, when I was turning faster times with an n/a car! 3 times the power with 1/3 the grip isn't as much fun.

EvoRoadster - You can run DOT slicks in SM2 in SCCA and clubs who've adopted their rulebook. Not sure what it's like on the islands but that's how it is here.

Last edited by kotomile; 07-06-2009 at 01:04 PM.
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Old 07-06-2009, 09:16 AM   #6
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I'm running 215 wide 17" V710s and am plenty competitive in SSM (was SM2). I don't think you'd have any problems on a 225 15"
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Old 07-06-2009, 11:20 AM   #7
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the latest GRM has a tire test on an RX8 using super wide vs. kinda wide tires. their results show better times with the narrower tires. you'll have to find the whole article to find out why since I didn't take notes when I read it.
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Old 07-06-2009, 11:53 AM   #8
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225/45R13 Hankook Z214 FTW.

Name:  z214miata2.jpg
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Name:  6-6-09autox1.jpg
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Old 07-06-2009, 12:36 PM   #9
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I run 225/50/15's on the factory 6" wide wheel. My tire guys love me (not). Convential wisdom is to run a 205/50/50 in cstock but I find that the i'd rather have the grip afforded by the larger tire.

Like someone said what are you going for. Are you looking to be competitive or just to have fun. That will tell you how much to blow and what is a good combo or not. SSM can get pretty crazy in the $$$ department
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Old 07-06-2009, 01:16 PM   #10
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y8s & Dopplesmoker - Thanks, I think that seals it. 225s it is.

budget racer - Your pics bring back memories! Like I mentioned above I used to run 225/45/13 Hoosiers and loved them (everything but their breakaway characteristics) and want to get back into a similar compound (A6). I don't really want to go back to 13s though, since the extra gearing is not something I need anymore and there is a brake upgrade in the future.

Pitlab - I want to be competitive and have fun! To me the two aren't so unrelated. Wondering at the end of the event how I'd have fared had I had better tires is getting old. I'm currently placing mid-pack in SM2 at the tight 510-club autocrosses and at yesterdays Corvette-club-style autox I don't know how I did in SM2, but I was 3 seconds behind a SC'd Elise on good tires (on a 46-second course). I wonder how much faster I'd have been if I'd had better tires...
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Old 07-06-2009, 01:21 PM   #11
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Quote:
Originally Posted by kotomile View Post

Pitlab - I want to be competitive and have fun! To me the two aren't so unrelated. Wondering at the end of the event how I'd have fared had I had better tires is getting old. I'm currently placing mid-pack in SM2 at the tight 510-club autocrosses and at yesterdays Corvette-club-style autox I don't know how I did in SM2, but I was 3 seconds behind a SC'd Elise on good tires (on a 46-second course). I wonder how much faster I'd have been if I'd had better tires...

This is how i've been. I'm running crappy tires at autox and i'm behind stock power miatas with good tires :(

I have RS2s being delivered today, hopefully that helps. I just cant do the slicks yet...need to be a better driver first.
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Old 07-06-2009, 07:16 PM   #12
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Quote:
Originally Posted by kotomile View Post
So, my questions:

- Is there any good reason to run a 275 for my use versus a 225?

- Has anyone found a 235, 245, 255, or 265 width DOT slick in a 15" diameter?

What I decide for tires will ultimately impact my wheel choice, since if I find there's no reason to run a 275, then there's no need for a 15x9 wheel, I can save the cost and weight over the equivalent 15x8.

TIA
In SSM (used to be called SM2) you need 275 to be competitive. Dont even bother if you dont have LSD and 275s. You wont hold up well against the Z06's and Elise.

You need much larger tires in auto-x than road racing because the vehicle operates in completely different ranges there - the tires have little time to heat up, and are subjected to substantial amounts of slip as the car is thrown around the ridiculous transitions that some courses have.

If you're getting 275 and have a budget like mine then just buy the cheapest 15x10 you can find (aero race and diamond make some affordable large wheels), I doubt you'll regret it.


I am not serious enough to get DOT R-compounds, so I just bought a set of 16x7 Rota RB's and threw on 215/45-16 Kumho Ecsta XS. Best investment I ever made.


Last edited by The_Pipefather; 07-06-2009 at 07:29 PM.
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Old 07-06-2009, 08:05 PM   #13
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The competitive guys at the autox around here seem to praise the Dunlop Direzza Star Spec's. I'm currently running 225/45/16 RS2's and they're ok, but I'm hoping that going to the direzza or similar soon will give me that extra bit of grip needed.

Michael
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Old 07-06-2009, 10:06 PM   #14
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goodyear cantilevers
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Old 07-06-2009, 11:37 PM   #15
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Hoosier makes a 255/40-13. That's what I'd run if I were getting serious about SM2 and didn't want to flare my car (you need to flare it to fit the 275s).
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Old 07-07-2009, 12:41 AM   #16
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Quote:
Originally Posted by The_Pipefather View Post
In SSM (used to be called SM2) you need 275 to be competitive. Dont even bother if you dont have LSD and 275s. You wont hold up well against the Z06's and Elise.

Depends...regional he might be just fine on 225's. For Nationals..275s or GTFO.

Quote:
Originally Posted by TheBandit View Post
The competitive guys at the autox around here seem to praise the Dunlop Direzza Star Spec's. I'm currently running 225/45/16 RS2's and they're ok, but I'm hoping that going to the direzza or similar soon will give me that extra bit of grip needed.

Michael
In SSM, we can run much stickier tires like the A6, V710 and R1.
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Old 07-07-2009, 01:19 AM   #17
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Well the autox i go to is just a Porsche club event. No classes, just run what ya brung. I'm definitely interested in some seriously grippy tires, but they have to be able to be driven on the street when I feel like taking the car for a drive. I've heard mixed opinions on whether to get a r-comps or just stay with quality street tires. Maybe some opinions on that would help us in this situation.

Michael
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Old 07-07-2009, 07:37 AM   #18
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Quote:
Originally Posted by TheBandit View Post
I've heard mixed opinions on whether to get a r-comps or just stay with quality street tires. Maybe some opinions on that would help us in this situation.

Michael


aaaaaaaaahahahahhahahahahhaha

Never listen to any of the people who suggested street tires to you ever again. Autocrossing a turbocharged Miata on street tires is like running in socks on a freshly cured hardwood floor.
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Old 07-07-2009, 11:05 AM   #19
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Quote:
Originally Posted by Savington View Post
aaaaaaaaahahahahhahahahahhaha

Never listen to any of the people who suggested street tires to you ever again. Autocrossing a turbocharged Miata on street tires is like running in socks on a freshly cured hardwood floor.
maybe a few less H and A sav, even GRM is suggesting that the gap is narrowing between street tires and DOT-R tires in terms of the compounds available and ultimate grip. and keep in mind the heat cycles on an autox course are less extreme than on a track.
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Old 07-07-2009, 11:35 AM   #20
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narrowing the gap =
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