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post #1 of 14 (permalink) Old 01-25-2007, 12:40 PM Thread Starter
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AutoX / twisties driving...

Wanting everyone's opinion on autocross and roadrace driving. I am wondering if it is better to have all 4 tires the same, or a staggered setup. What would you do for competition? I want to stick with an 18" wheel. Here is what I am thinking...

18x9 on all 4 corners, 245-45-18

OR

18x8f, 245-45-18 and 18x9r, 275-40-18

Educate me.

-Joel

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post #2 of 14 (permalink) Old 01-25-2007, 03:15 PM
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From my experience in i guess you can call it "spirited" driving on various cars (mostly rear wheel drive). I am talking about street driving not ACTUAL AUTOX. Having a staggered setup (assuming larger tires in the rear) tends to push or understeer. The understeer becomes very apparent in short sharp turns or turns that require a quick change of direction. Sweeping turns the difference in understeer i would say is minimal. My advice to you is to get the same size tires on all four wheels. Good luck
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post #3 of 14 (permalink) Old 01-25-2007, 07:26 PM
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Ok, first, Ed N. is probably one of the resident experts on this subject.

With that in mind, what I've found and how Ed directed me was that if you are going to autocross or road race these cars you need plenty of grip. I currently am running a setup of P245/40-18's on the front and P275/35-18's on the rear. The result was that I couldn't hold my lines coming into the turns because I didn't have enough grip in the front tires. Ed explained that since the majority of the weight of the car is up front and that it shifts more toward the front when you brake coming into a turn.

So, I would recommend running P275's all the way around. I also recommend that if you are going to race on them that you don't get anything that has a treadwear rating over 200 or so. Otherwise they just get more slippery as they get hot and that's not a good thing for a day of racing.

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post #4 of 14 (permalink) Old 01-25-2007, 07:33 PM
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Let me know when you get the tire thing worked out. I plan on making as many trips to Salina for Solo II autocrossing as possible this summer. (Soon as I get the springs, shocks, sway bars, etc. from the LE onto the LX )


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post #5 of 14 (permalink) Old 01-25-2007, 07:49 PM Thread Starter
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How the hell do you fit a 275 up front?!

-Joel

Previous MN12s:
'95 Thunderbird 4.6L V8 - Performance White
Bought 01/12/08 w/ 33,000 original mi. Big plans, little execution. Sold as a fallen victim to life's happenings.
'95 Thunderbird 4.6L V8 - Performance White
Leaky shifter @ 137,441; what a good ride. Gone to the crusher, but not forgotten... moth and rust doth corrupt.

'13 Mustang GT Premium 5.0L V8, Auto, Brembo, Black - Daily Dark Horse
'11 Edge SEL AWD 3.5L V6, Loaded, Black - For the Misses
'98 F-150 XLT RegCab 8'Bed, 4.6L V8 4x4 ORP Oxford White - Work Truck

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post #6 of 14 (permalink) Old 01-25-2007, 07:56 PM
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Quote:
Originally Posted by GODSPEED
How the hell do you fit a 275 up front?!

-Joel
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post #7 of 14 (permalink) Old 01-25-2007, 08:45 PM Thread Starter
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Uh... spell it out for me, I dont get it.

will a 275-40-18 fit on an 8.5 nicely?

-Joel

Previous MN12s:
'95 Thunderbird 4.6L V8 - Performance White
Bought 01/12/08 w/ 33,000 original mi. Big plans, little execution. Sold as a fallen victim to life's happenings.
'95 Thunderbird 4.6L V8 - Performance White
Leaky shifter @ 137,441; what a good ride. Gone to the crusher, but not forgotten... moth and rust doth corrupt.

'13 Mustang GT Premium 5.0L V8, Auto, Brembo, Black - Daily Dark Horse
'11 Edge SEL AWD 3.5L V6, Loaded, Black - For the Misses
'98 F-150 XLT RegCab 8'Bed, 4.6L V8 4x4 ORP Oxford White - Work Truck

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post #8 of 14 (permalink) Old 01-25-2007, 09:04 PM
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big ****in hammer.




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post #9 of 14 (permalink) Old 01-25-2007, 09:30 PM Thread Starter
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Ah, yeah I got a couple of those. Working in construction leaves you with a lot of badass tools. Back on the subject... 275-40-18 on 8.5 for competition? What offset for a 8.5" rim with that tire for the front?

-Joel

Previous MN12s:
'95 Thunderbird 4.6L V8 - Performance White
Bought 01/12/08 w/ 33,000 original mi. Big plans, little execution. Sold as a fallen victim to life's happenings.
'95 Thunderbird 4.6L V8 - Performance White
Leaky shifter @ 137,441; what a good ride. Gone to the crusher, but not forgotten... moth and rust doth corrupt.

'13 Mustang GT Premium 5.0L V8, Auto, Brembo, Black - Daily Dark Horse
'11 Edge SEL AWD 3.5L V6, Loaded, Black - For the Misses
'98 F-150 XLT RegCab 8'Bed, 4.6L V8 4x4 ORP Oxford White - Work Truck

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post #10 of 14 (permalink) Old 01-26-2007, 05:08 AM
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If you can fit the 8.5" wheel up front then you can fit the P275 tire. I'm running 9" wheels all around and I'm not having any problems. I am running a wheel spacer but only because PWO didn't make sure of the backspacing on my Cobra R's. The spacer I'm running is 3mm thick so it's not much. I'm not running that because of the tires but because of the wheels.

"When the only tool you have is a hammer, suddenly everything looks like a nail."
"Nothing is foolproof because fools are so ingenious."
1992 Ford Thunderbird SC

Coast High Peformance 347 Stroker
-Low Tension Oil Rings, Zero Gap Seconds
-10.5:1 Compression Ratio
Trick Flow Twisted Wedge heads
Trick Flow Stage 1 cam
Trick Flow Street Heat Intake
Mac 1 5/8 long tube headers
FRPP 42# injectors
3.27 gears
Custom aluminum driveshaft
M5R2
Burned Chip for SN95 T4M0 ECM
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post #11 of 14 (permalink) Old 01-26-2007, 07:01 AM
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MaddMartigan - where did you get those spacers in case I need them with the new wheels? I think I am going to a 275 now because I can get a better tire for cheaper than 255's according to Tirerack.

-Miller

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post #12 of 14 (permalink) Old 01-26-2007, 07:14 AM
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Quote:
Originally Posted by miller1995
MaddMartigan - where did you get those spacers in case I need them with the new wheels? I think I am going to a 275 now because I can get a better tire for cheaper than 255's according to Tirerack.

-Miller
I got them on Ebay. They are relatively cheap. Obviously no spacer is ideal so the thinner the spacer you can get away with the better.

"When the only tool you have is a hammer, suddenly everything looks like a nail."
"Nothing is foolproof because fools are so ingenious."
1992 Ford Thunderbird SC

Coast High Peformance 347 Stroker
-Low Tension Oil Rings, Zero Gap Seconds
-10.5:1 Compression Ratio
Trick Flow Twisted Wedge heads
Trick Flow Stage 1 cam
Trick Flow Street Heat Intake
Mac 1 5/8 long tube headers
FRPP 42# injectors
3.27 gears
Custom aluminum driveshaft
M5R2
Burned Chip for SN95 T4M0 ECM
OMGHI2U

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post #13 of 14 (permalink) Old 02-02-2007, 06:30 PM
 
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I autocross on 255/45-17 Hoosiers. I run the same size on all four corners so that I can rotate the tires to any corner depending on how they wear. On street tires, though, I think wider rears would be helpful to tighten the car up a bit--mine tends to rotate a bit too much on street tires.
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post #14 of 14 (permalink) Old 04-01-2007, 11:05 PM
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Square sizing

Off topic but nice mag merctio.

I agree the bigger you can run in the front is good.
Changed to 25.5x13x16's from 23.5x12x16's on my roadrace car and what a difference.
Depending on how bad it's pushing you can change tire pressures or even sway bars to help fix it.
A driver can also alter his/her corner entry to help reduce the push.
Smoother into the corner if possible.
Too much (getting greedy) throttle right after turn in or in the middle of the corner will also exagerate the push.
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