How much margin is there in tire diameter size for the AWD TT's
04-12-2008, 12:14 AM
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How much margin is there in tire diameter size for the AWD TT's
Just wondering if the TT's are designed to run with a specific tire diameter in order for the traction control and ABS and PSM to work right. I've noticed that most "N" rated tires for the 996TT are around 25mm give or take .4 mm. Does running a wider and taller tire affect the cars electronic control systems at all?
06-20-2009, 08:44 PM
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Perhaps you mean 25" tire diameter rather than 25 mm. I don't know anything about TT's, but I think the general rule of thumb for us slow pokes is staying within about 4% of OEM tire diameter. That's about 1" more or less diameter. I've run about an inch shorter in the rear, and now have about .33" taller than OEM with no problems. I don't think different widths confuse the sensors.
06-21-2009, 04:15 AM
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Doh! you are right, 25" not mm. I guess the only difference would be the TT's AWD system but the PSM and ABS should be the only two systems that would be more finicky about overall diameter right?
06-21-2009, 01:15 PM
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I think you're right about only PSM and ABS being finicky about tire diameters. Of course, speedometer and odometer will also over or under measure with shorter or taller tires, but they don't seem to mind.
AWD systems (which I also don't know much about) may have more constraints than RWD systems, so maybe you should post the question on the TT forum. The 996 and 997 AWD systems may be somewhat different as well.
AWD systems (which I also don't know much about) may have more constraints than RWD systems, so maybe you should post the question on the TT forum. The 996 and 997 AWD systems may be somewhat different as well.
07-04-2009, 02:36 PM
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I believe that by the time you get to around 7% difference, the AWD system will basically lock up front to rear. 4% is the safe number to stay within. ABS shutting down is very annoying, so you'd rather be well under the 4% figure.
The 997 models are all different -- this info is for 993/996. The 997 platform electronics and AWD want a difference of about 1" front to rear (a bit over 25" front, and a bit over 26" rear).
Wider is OK for dry track, taller is not OK. Watch out for the turbo outlet hose clamp on the left rear tire. A good friend did a double 360 at Daytona after cutting down a tire on his 996 GT2. Yes it was expensive, but nowhere near as bad as it could have been.
The 997 models are all different -- this info is for 993/996. The 997 platform electronics and AWD want a difference of about 1" front to rear (a bit over 25" front, and a bit over 26" rear).
Wider is OK for dry track, taller is not OK. Watch out for the turbo outlet hose clamp on the left rear tire. A good friend did a double 360 at Daytona after cutting down a tire on his 996 GT2. Yes it was expensive, but nowhere near as bad as it could have been.
