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Old 10-26-2004, 09:23 PM   #1
Greg - LI
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Default AutoX Tire/Wheel Question

Though I have an 01 RS as my street car, I plan on autocrossing my NA 89 RX-7 this up coming season. I am looking for opinions as to which of 2 tire and wheel choices would be most beneficial. I'm not interested in being in a particular class, just my time vs. others. I don't care about classification rules.

Choice 1 : Stock 15*6 (16 lbs) with 225/50/15
Advantages: Lower gearing due to smaller diameter
Reduced tire weight
Disadvantages: Narrow wheel


Choice 2 : SSR 17*7.5 (14 lbs) with 225/45/17
Advantages: Larger overall contact patch
Less wheel weight
Wider wheel
Shorter sidewall
Disadvantages: Taller gearing
Higher tire weight

I think the reduced weight and lower gearing of the 15" combo is my best bet despite the narrow wheel. Tips? Advice? Thanks in advance.
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Old 10-26-2004, 10:55 PM   #2
gregr01
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You haven't provided enough information to make a good recommendation, but...

Tire selection makes a bigger difference than 15/6 or 17/7.5 option, and driver ability makes a bigger difference than tires.

Go with the 17s and put a 235/40 R-compound tire on them and have at it.
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Old 10-26-2004, 11:19 PM   #3
Greg - LI
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OK. What more information do you need? Assume the same R compound tires in either scenario. I'm thinking of Toyo RA-1 or Kuhmo VictoRacers, though the price of the Falken Azenis Sport makes them ver attractive as well. I'm not sure 235 tires will fit in the front. If they do, it will be very tight. Thanks for the suggestion.
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Old 10-26-2004, 11:48 PM   #4
gregr01
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I used to flog an 86 RX-7 with 225/50/16s and no rubbing. 25" o/a diameter, so a 235/40/17 at about 24.5" o/a should be okay, depending on offset (which is very positive on the gen-2 7s, iirc). You might want to check on the RX boards for first-hand experience with that size, though.

You say you're not interested in what class you'll compete -- just what your time will be against others. Well, that doesn't make a lot of sense. If you have a bunch of mods, you'll be competing in a class where you're likely to get spanked. If you compete on R tires, you'll be competing against others similarly shod and likely to get spanked.

If you just want to be sure to beat your friends' times regardless of where that puts you in your class, then R tires it is. RA-1s, VictoRacers, V700s... they're all expensive ways to try to best your pals, but R tires are the fastest way to cut autox times--other than improving the driver.

Why not go out for an event or two on your daily driving wheels/tires and see where you end up? You'll have a lot better idea of what you need, what others are doing, and where you fall in against the competition--whoever that may be.
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Old 10-27-2004, 08:45 AM   #5
Greg - LI
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225/50/16 would be my first choice, but I'd have to get another set of wheels then. The front of the FC chassis has very small wheel wells and I'm almost sure that a 235 will rub the spring with my +42 offset wheels. There is also virtually no negative camber available up front with out using camber plates and coil overs. Right now the car is on Racing Beat springs with 0 camber.

I've run many events with my car on its street tires (205/60/15) and while I have a blast, the complete lack of traction is killing me. I just need more grip. The modifications already done to the car make me completely uncompetitive in any class. Running in the stock class isn't even an option anymore.

I'm just looking for the tire and wheel setup that will give me and this car the fastest possible time regardless of class. Plus, I'd like to do it with one of the wheel sets I already have if at all possible.
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Old 10-27-2004, 10:05 AM   #6
ratt_finkel
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Where don't you have traction? And yes, that size tire does seem small. What class are you running? Are you trying to be competitive, or just go out there and have some fun?
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Old 10-27-2004, 07:54 PM   #7
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I ran my lowered Miata on 13 inch rims, down from 14 inch rims this year. The gearing change helped acceleration, but it also caused me to have to shift into 3rd or beat my rev limiter on the longer courses. The net effect, to me was zero. The time I picked up with acceleration was lost upshifting and downshifting.
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