Track Tires
04-11-2009, 03:22 PM
#1
Heel & Toe
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Track Tires
Anyone here going with 2 sizes up on track tires? I called a tire place and told them I wanted to go up 2 sizes and he recommended I stay with the OEM due to differential and tranny computer
He said the GM guys spent tons of research on the track getting those exact tire sizes and would not recommend going beyond. However, he did go on to say I could go with 305/35-18 on the rears but would not go wider on the fronts or I'd experience tire rub which does make some sense. Anyone with any advice would be appreciated
He said the GM guys spent tons of research on the track getting those exact tire sizes and would not recommend going beyond. However, he did go on to say I could go with 305/35-18 on the rears but would not go wider on the fronts or I'd experience tire rub which does make some sense. Anyone with any advice would be appreciated
04-11-2009, 03:29 PM
#2
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What size wheels are you using?
I use 18x305/30 on 18x12" rims in the front and 18x335/30 on 18x13" rims on the rear.
Do they rub? with brake ducts up front only if I turn lock to lock. So I dont turn lock to lock.
Do the rear tires rub ? Not any more? the inner wheel well line has been rub away, and what wasn't rubbed away I cut away.
Lots of guys use 315s up front.
what is the idea size? depends on the wheels you get.
What ever you wind up doing, AH / TC should be turned off.
One more thing, those tire places, unless they do track events or race themselves, take with a grain of salt.
I use 18x305/30 on 18x12" rims in the front and 18x335/30 on 18x13" rims on the rear.
Do they rub? with brake ducts up front only if I turn lock to lock. So I dont turn lock to lock.
Do the rear tires rub ? Not any more? the inner wheel well line has been rub away, and what wasn't rubbed away I cut away.
Lots of guys use 315s up front.
what is the idea size? depends on the wheels you get.
What ever you wind up doing, AH / TC should be turned off.
One more thing, those tire places, unless they do track events or race themselves, take with a grain of salt.
04-12-2009, 12:01 AM
#3
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If you are going to leave the car in Comp. mode your biggest concern is tire height. If you shut everything off run the largest tire that fits on your wheels.
04-12-2009, 12:34 AM
#4
Heel & Toe
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What size wheels are you using?
I use 18x305/30 on 18x12" rims in the front and 18x335/30 on 18x13" rims on the rear.
Do they rub? with brake ducts up front only if I turn lock to lock. So I dont turn lock to lock.
Do the rear tires rub ? Not any more? the inner wheel well line has been rub away, and what wasn't rubbed away I cut away.
Lots of guys use 315s up front.
what is the idea size? depends on the wheels you get.
What ever you wind up doing, AH / TC should be turned off.
One more thing, those tire places, unless they do track events or race themselves, take with a grain of salt.
I use 18x305/30 on 18x12" rims in the front and 18x335/30 on 18x13" rims on the rear.
Do they rub? with brake ducts up front only if I turn lock to lock. So I dont turn lock to lock.
Do the rear tires rub ? Not any more? the inner wheel well line has been rub away, and what wasn't rubbed away I cut away.
Lots of guys use 315s up front.
what is the idea size? depends on the wheels you get.
What ever you wind up doing, AH / TC should be turned off.
One more thing, those tire places, unless they do track events or race themselves, take with a grain of salt.
What does AH / TC mean?
04-12-2009, 01:16 AM
#6
Burning Brakes
AH / TC = Active Handling / Traction Control.
A "regular" C5 came with 17 x 8.5 front and 18 x 9.5 rear. Z06 has 1" wider rims f & r. You can't get a 305 on a 9.5" rear. If you have a C5 Z06 you can use a 305/30-18 rear tire with a 275/40-17 front and you will not have AH/TC problems.
If you run in comp mode (which is AH on and TC off), the tires need to be very close to stock height or at least the ratio of their heights must be close to stock or the computer will kick in AH at the wrong times. If you are tracking for the first time I highly recommend to run in comp mode.
If driving on the street with improper ratio of heights TC will kick in. I know from experience. It did so at about 50mph with a 295/30 rear and a 275/40 front.
A "regular" C5 came with 17 x 8.5 front and 18 x 9.5 rear. Z06 has 1" wider rims f & r. You can't get a 305 on a 9.5" rear. If you have a C5 Z06 you can use a 305/30-18 rear tire with a 275/40-17 front and you will not have AH/TC problems.
If you run in comp mode (which is AH on and TC off), the tires need to be very close to stock height or at least the ratio of their heights must be close to stock or the computer will kick in AH at the wrong times. If you are tracking for the first time I highly recommend to run in comp mode.
If driving on the street with improper ratio of heights TC will kick in. I know from experience. It did so at about 50mph with a 295/30 rear and a 275/40 front.
Last edited by Bimota Guy; 04-12-2009 at 01:23 AM.
04-12-2009, 03:51 AM
#7
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AH / TC = Active Handling / Traction Control.
A "regular" C5 came with 17 x 8.5 front and 18 x 9.5 rear. Z06 has 1" wider rims f & r. You can't get a 305 on a 9.5" rear. If you have a C5 Z06 you can use a 305/30-18 rear tire with a 275/40-17 front and you will not have AH/TC problems.
If you run in comp mode (which is AH on and TC off), the tires need to be very close to stock height or at least the ratio of their heights must be close to stock or the computer will kick in AH at the wrong times. If you are tracking for the first time I highly recommend to run in comp mode.
If driving on the street with improper ratio of heights TC will kick in. I know from experience. It did so at about 50mph with a 295/30 rear and a 275/40 front.
A "regular" C5 came with 17 x 8.5 front and 18 x 9.5 rear. Z06 has 1" wider rims f & r. You can't get a 305 on a 9.5" rear. If you have a C5 Z06 you can use a 305/30-18 rear tire with a 275/40-17 front and you will not have AH/TC problems.
If you run in comp mode (which is AH on and TC off), the tires need to be very close to stock height or at least the ratio of their heights must be close to stock or the computer will kick in AH at the wrong times. If you are tracking for the first time I highly recommend to run in comp mode.
If driving on the street with improper ratio of heights TC will kick in. I know from experience. It did so at about 50mph with a 295/30 rear and a 275/40 front.
Sounds like comp mode is the way to go but what would be considered "close to stock height"? 1 size up? 2 sizes? I have the stock C5 17 x 8.5 front and 18 x 9.5 rear wheels as you mentioned above.
Last edited by Batman/theDarkKnight; 04-12-2009 at 03:54 AM.
could be
04-12-2009, 01:26 PM
#11
Burning Brakes
Unless you are getting larger rims you can't go up much. My suggestion is to calculate the ratio of heights (you can get heights off Tire Rack) for the stock tires and then the ratio of heights for the sizes I mentioned above I used with success on my Z06. In between those two ratios you will be fine. You might also chek the ratio of the stock Z06 (Supercar) tires to ensure they are close to the regular C5's ratio.
BTW, I run equal sizes (315-35/17) at all 4 corners of my race car. I turn off both AH & TC when on track. But I know I have accidently left them on and did not feel TC kick in even at fairly high speeds, but did feel AH kick in when tossed hard into a croner. But that was probably due to the car turning harder (due to stiff suspension and very sticky tires) than the computer expects it can handle, and not tire sizes or TC would have kicked in first.
04-12-2009, 04:07 PM
#13
Heel & Toe
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It is the ratio of heights that is the issue. My "failed" set of tires was taller in the front and shorter in the back. Why did this not work? Because all the computer knows is the number of rotations per unit time for each wheel. The shorter rear is turning faster than the stock tire. The problem is exacerbated by the taller front turning less than stock. Thus the computer thinks the rear has lost traction (i.e., "burning out") and TC kicks in. As I think about it, I am not sure how bad Comp Mode (AH only) would be under these conditions, if at all, because I think all it cares about is the yaw rate of the car, not wheel speed.
Unless you are getting larger rims you can't go up much. My suggestion is to calculate the ratio of heights (you can get heights off Tire Rack) for the stock tires and then the ratio of heights for the sizes I mentioned above I used with success on my Z06. In between those two ratios you will be fine. You might also chek the ratio of the stock Z06 (Supercar) tires to ensure they are close to the regular C5's ratio.
BTW, I run equal sizes (315-35/17) at all 4 corners of my race car. I turn off both AH & TC when on track. But I know I have accidently left them on and did not feel TC kick in even at fairly high speeds, but did feel AH kick in when tossed hard into a croner. But that was probably due to the car turning harder (due to stiff suspension and very sticky tires) than the computer expects it can handle, and not tire sizes or TC would have kicked in first.
Unless you are getting larger rims you can't go up much. My suggestion is to calculate the ratio of heights (you can get heights off Tire Rack) for the stock tires and then the ratio of heights for the sizes I mentioned above I used with success on my Z06. In between those two ratios you will be fine. You might also chek the ratio of the stock Z06 (Supercar) tires to ensure they are close to the regular C5's ratio.
BTW, I run equal sizes (315-35/17) at all 4 corners of my race car. I turn off both AH & TC when on track. But I know I have accidently left them on and did not feel TC kick in even at fairly high speeds, but did feel AH kick in when tossed hard into a croner. But that was probably due to the car turning harder (due to stiff suspension and very sticky tires) than the computer expects it can handle, and not tire sizes or TC would have kicked in first.
I want to stay with the stock wheels for now since I'm trying the track and see how it goes. I'm already investing in helmet, gloves tires, track fees etc. I can always buy bigger and better tires/wheels later if I get hooked on the sport.
So looks like I need to go to tire rack and figure out how much bigger tires to go with. Thanks again for the help
04-12-2009, 04:20 PM
#14
Burning Brakes
...if I get hooked on the sport.
I think I saw you posting about going to WSIR on May 1st. I hope to be there with my T1 car. Say "hello" if you see this rig...
Last edited by Bimota Guy; 04-12-2009 at 04:24 PM.
04-13-2009, 07:32 PM
#15
Heel & Toe
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04-16-2009, 12:03 AM
#16
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http://forums.corvetteforum.com/sout...r-may-1-a.html
DH
