Doesn't different tire size require programming ECM for correctiveness?
Thread Starter
Corvette ***** OG
Joined: Oct 2003
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From: Charlotte NC
St. Jude Donor '05
CI VI Veteran
Doesn't different tire size require programming ECM for correctiveness?
I actually started posting this in a thread that was already started about me buying wider wheels but I think my new question would be better asked here.
I putting on wider wheels on the rear. Obviously, I'll have a different tire than stock...
So, I called More Performance and asked them when they made changes to the ECM for the supercharger, if they wouldn't mind changing the parameters for the tires to the new tire size... that being, 315-3-/18's from the stock 275's.
I was told that they didn't have to do that because the reading comes from the ring gear and it'll compensate by itself.
Has anyone heard of this? I always thought if you changed tires or gear ratios, you still had to change the ECM.
My car is a '98, does that make a difference? I know the 98's are different in wierd ways from the 99's and up.
Anyone?
Thanks,
Mark
I putting on wider wheels on the rear. Obviously, I'll have a different tire than stock...
So, I called More Performance and asked them when they made changes to the ECM for the supercharger, if they wouldn't mind changing the parameters for the tires to the new tire size... that being, 315-3-/18's from the stock 275's.
I was told that they didn't have to do that because the reading comes from the ring gear and it'll compensate by itself.
Has anyone heard of this? I always thought if you changed tires or gear ratios, you still had to change the ECM.
My car is a '98, does that make a difference? I know the 98's are different in wierd ways from the 99's and up.
Anyone?
Thanks,
Mark
Safety Car
Joined: May 2000
Posts: 4,827
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From: Albuquerque NM
They told you wrong. For a 6 speed you don't need to reprogram for a ring and pinion change, but for any tire size changes reprogramming is required for the speedo/odometer and to get an auto to shift correctly. Depending on how large the change in tire diameter is, you may not want to go through the trouble.
Thread Starter
Corvette ***** OG
Joined: Oct 2003
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From: Charlotte NC
St. Jude Donor '05
CI VI Veteran
Thanks, that's what I thought. I called back and politely suggested they rethink their decision.
As far as going through the trouble, they're installing a supercharger now and since they're going to have to dyno tune it, I thought this would be the ideal time to change tire sizes in the ECM.
Mark
As far as going through the trouble, they're installing a supercharger now and since they're going to have to dyno tune it, I thought this would be the ideal time to change tire sizes in the ECM.
Mark
Team Owner
Joined: Apr 2001
Posts: 54,204
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From: S.W. Ohio. . . . . . NRA Life Member
The Width isn't going to make a difference
instead of thinking in tire and rim sizes... the important measurement is total tire heigth.
Only a change in rear tire "heigth" will induce speedo error.
Race Director
Joined: Oct 2002
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
315/30's are significantly shorter than the stock 275's...so if they are tuning the car anyways, it's a simple matter to input the new rear tire size.
The change will only affect is the speedometer reading. If not done, not a big deal really, you'll be going a little slower than you think you are, the "safe" side to err on. The difference is slght though, most people don't bother with it and never notice a difference.
The change will only affect is the speedometer reading. If not done, not a big deal really, you'll be going a little slower than you think you are, the "safe" side to err on. The difference is slght though, most people don't bother with it and never notice a difference.
Race Director
Joined: Mar 2001
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From: Bonneville Salt Flats
Right, depends on the difference in tire circumference from stock. Small changes can be tolerated since normal wear also changes the specs slightly. Also, Z06 tires are a bit different than runflats. I do not know what the parameters are for codes. Maybe someone does. Of course, speedo will also be affected.
All the best.
All the best.
Thread Starter
Corvette ***** OG
Joined: Oct 2003
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From: Charlotte NC
St. Jude Donor '05
CI VI Veteran
Thanks guys, that's what I thought, I don't know why they said it will compensate for itself, I know it never has for any other tires I've used.
Mark
Mark
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Thread Starter
Corvette ***** OG
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From: Charlotte NC
St. Jude Donor '05
CI VI Veteran
Originally Posted by Mike Mercury
let me interpret: "We really don't know"
Mark
Tech Contributor
Joined: Mar 2003
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From: Colorado Springs, CO
St. Jude Donor '08-'09-'10-'11
In LS1 EDIT there is a calibration tab that asks for tire diameter....the ZO6 is 26.1 and the C5 is 26.7. As the tires in the rear wear out, the traction control/active handling will trigger for no apparent reason. It is actually that if you are 3/4 tread bald the tires are 1" or more shorter than new and adjusting the diameter in edit fixes this. I did this to my own car and it isn't second hand hear-say. I switched to running the ZO6 wheels and tires at one point and had to do this. If you go with Pilot sports that are 26" tall.....enter 26".
Good luck.
Good luck.
Race Director
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From: Gone
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St. Jude Donor '03
Originally Posted by SpinMonster
As the tires in the rear wear out, the traction control/active handling will trigger for no apparent reason. It is actually that if you are 3/4 tread bald the tires are 1" or more shorter than new
Most tires come with 10/32" tread on them. That's .3125". Even if you wore them down to totally bald (not recommended), you'd lose .625" (5/8") diameter. If your tires are sized correctly in relation to the fronts, this shouldn't present a problem, plus keep in mind your fronts wear down too. This is exactly why there is a decent tolerance built into the TC/AH programming.
Further, the rear tire size setting in LS1-Edit only changes the speedometer. it does NOT recalibrate the TC/AH program.
Advanced
Joined: Jan 2003
Posts: 77
Likes: 0
From: Seattle WA
Here's a good website for a tire size calculator for comparing bigger tire sizes to your stock 275's. www.1010tires.com It will provide the diameters of original and replacement options. It will also provide a % difference in speedo readings and actual mph differences at 60 mph. The only thing it won't tell you is what the maximum tire is that will fit in the well without clearance issues. For that your forum buddies will have a wealth of experience.
Burning Brakes
Joined: Apr 2003
Posts: 908
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From: TROY MI
I have a 02 Vert.Last May I installed 275/40/17 BFG DR's on it for the summer.This Changed my speedo readings.The DR's are one inch shorter than the stock tires.I used my predator to change the tire size in the ECM and my speedo reads dead nuts on.Also my front and rear tires are now the same diameter and I have not had any problems with AH. The tires are still on the car and everything is working great.
Le Mans Master
Joined: Feb 2003
Posts: 6,683
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From: Memphis Tennessee
Originally Posted by Mike Mercury
instead of thinking in tire and rim sizes... the important measurement is total tire heigth.
Only a change in rear tire "heigth" will induce speedo error.
Safety Car
Joined: Jul 2001
Posts: 4,661
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From: Ocean Springs MS
Originally Posted by allegro
Very close.... but the impotant measurement is rolling circumference.
c5, ca, ecm, forums, mountain, performance, programing, programming, reprogramming, size, tire, tires, view, wheels, wrong
