Tire sizing with active handling ?
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Joined: Feb 2003
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From: Cape Cod Ma
Tire sizing with active handling ?
I have a 2000 FRC with stock tires (245/45/17 fronts : 275/40/18 rears) and have purchased Z06 rims to up grade. To conver to Z06 sizing it will be 265/40/17 : 295/35/18) on the Goodyear super car tires. But, if you want other tires the 265's are not available. You may have 255's or 275's.
275/40/18 are 26.7" diameter (stock)
295/35/18 are 26.1" diameter ( no one makes a 305/35/18)
.6 difference
245/45/17 are 25.7" diameter (stock)
255/40/17 are 25.0"
.7 difference
275/40/17 are 25.7" diameter (same as stock)
Stock set up has a 1" difference from rear to front in diameter or size. When converting to other sizes will the active handling be effected if the 1" difference is not maintained ? Would it be better to keep the front set up the same and have the rear be .6" lower ? Or would that be effected ? Am I spending to much time on this ? Does it really matter ?
:banghead: :steering:
275/40/18 are 26.7" diameter (stock)
295/35/18 are 26.1" diameter ( no one makes a 305/35/18)
.6 difference
245/45/17 are 25.7" diameter (stock)
255/40/17 are 25.0"
.7 difference
275/40/17 are 25.7" diameter (same as stock)
Stock set up has a 1" difference from rear to front in diameter or size. When converting to other sizes will the active handling be effected if the 1" difference is not maintained ? Would it be better to keep the front set up the same and have the rear be .6" lower ? Or would that be effected ? Am I spending to much time on this ? Does it really matter ?
:banghead: :steering:
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From: Gone
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St. Jude Donor '03
Re: Tire sizing with active handling ? (BillFRC)
I'd go with the 255/40/17's for the front if you can't get the 265's in the particular tire you want.
The 275's might work, but that's cutting it very close to the computer's tolerances...you might not have problems, but it would be an expensive error if you did.
Generally people report no problems as long as the f/r stagger is 1/2" or more. The 275/295 combo would only be .4" difference. It's better to err on the side of more height difference than less.
Lastly, yes it really matters, and no, you're not spending too much time on this. Too many people don't do the research and run into problems after spending big $$ on new tires.
:cheers:
The 275's might work, but that's cutting it very close to the computer's tolerances...you might not have problems, but it would be an expensive error if you did.
Generally people report no problems as long as the f/r stagger is 1/2" or more. The 275/295 combo would only be .4" difference. It's better to err on the side of more height difference than less.
Lastly, yes it really matters, and no, you're not spending too much time on this. Too many people don't do the research and run into problems after spending big $$ on new tires.
:cheers:
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From: Gone
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St. Jude Donor '03
Re: Tire sizing with active handling ? (CapeCodCoupe)
Would there be any negative effect to running a 255 tire on the front rims built for 265mm width?
I checked a couple tires in the 255/40/17 size, and they are recommended for a 8.5-10" wide wheel. I'm assuming he has a 9.5, so it's a very good fit.
:cheers:
Team Owner
Joined: Mar 1999
Posts: 28,753
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From: San Jose/Bear Valley CA
CA Events Coordinator
Re: Tire sizing with active handling ? (BillFRC)
The thing to try to duplicate on new tires and wheels is keeping the 1" diff between the front and rear. The Car monitors wheel speed at all wheels with the EBTCM. Having a wheel speed variation of 9mph or more at any given wheel at any given time, a code will set and disable your ABS, TC and AH. Some cars are a little more touchy than others regarding this rule than others though.
Personally I have had 285/30/18 on the front and 335/30/18's on the rear as well as 265/35/18's front and 295/35/19's on the rear. Neither have given me trouble... I also run some Goodyear Racing Slicks which are very close to the same size without any problems too... That will not work on all C5's we have found
Just try to keep the fronts as close to 1" smaller than the rears and you should be ok. :)
Best of luck to you in your mod decisions. :blueangel:
vetterdstr :cheers:
Personally I have had 285/30/18 on the front and 335/30/18's on the rear as well as 265/35/18's front and 295/35/19's on the rear. Neither have given me trouble... I also run some Goodyear Racing Slicks which are very close to the same size without any problems too... That will not work on all C5's we have found
Just try to keep the fronts as close to 1" smaller than the rears and you should be ok. :)
Best of luck to you in your mod decisions. :blueangel:
vetterdstr :cheers:
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From: Gone
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St. Jude Donor '03
Re: Tire sizing with active handling ? (426 Hemi)
There will be some error, but very slight. (maybe 1mph off at freeway speeds).
Some of the programming tools out there allow you to enter the new tire size into the car's computer. This will calibrate the speedometer only, the t/c and a/h logic will be unaffected.
Going to a smaller dia tire will make the speedo read slightly faster than your actual speed. Most people will call this a safety margin. :D
:cheers:
Some of the programming tools out there allow you to enter the new tire size into the car's computer. This will calibrate the speedometer only, the t/c and a/h logic will be unaffected.
Going to a smaller dia tire will make the speedo read slightly faster than your actual speed. Most people will call this a safety margin. :D
:cheers:
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Safety Car
Joined: May 2003
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From: Dearborn Heights Michigan
Re: Tire sizing with active handling ? (Y2Kvert4me)
If the ratio of overall diameters between front and rear is less than 96% there could be a problem with traction control and ABS. Greater is OK, read this in one of the Corvette Magazines a while back. I have 265/35/18 frt and 295/35/18 rr with no probs.
Fred K.
Fred K.
Drifting
Joined: Aug 2002
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From: South
Re: Tire sizing with active handling ? (FKING1)
I was thinking of getting 2 sets of 17" wagon wheels and running 275/40/17s all the way around at the track. How bad will this screwup the AH/ABS?
What about 265/40/17 on the front and 275/40/17 on the rears?
This is on a 01 Z06.
[Modified by silverz06vette, 8:21 PM 7/2/2003]
What about 265/40/17 on the front and 275/40/17 on the rears?
This is on a 01 Z06.
[Modified by silverz06vette, 8:21 PM 7/2/2003]
Instructor
Joined: Sep 1999
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From: Cave Creek AZ
Re: Tire sizing with active handling ? (silverz06vette)
Ok if the tire size on a Z06 is 265 40 17 and 295 35 18 with front diameter of 25.4 and the rear diamater of 26.1 that ratio is already 97.3%. Is the Z06 programmed differently than the C5? Otherwise it would trip AH etc all the time? Does anyone know the tolerance on a Z06?
:cheers:
:cheers:
Race Director
Joined: Oct 2002
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From: Gone
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St. Jude Donor '03
Re: Tire sizing with active handling ? (kimvette)
Ok if the tire size on a Z06 is 265 40 17 and 295 35 18 with front diameter of 25.4 and the rear diamater of 26.1 that ratio is already 97.3%. Is the Z06 programmed differently than the C5? Otherwise it would trip AH etc all the time? Does anyone know the tolerance on a Z06?
:cheers:
:cheers:
You raise a good question though, and the Z may likely be programmed differently for the different size stock tires.
:cheers:
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Re: Tire sizing with active handling ? (BillFRC)
You should also look at the "static load radius" specs. A 26" tire on an 18" wheel will ride taller than a 26" tire on a 17" wheel ...
or even better, compare the "revs per mile"
..but if your down to those tie-breakers, it's probably a very close call.
or even better, compare the "revs per mile"
..but if your down to those tie-breakers, it's probably a very close call.
