I think he's borderline of what the computer will accept in the front/rear bias.
Tire Size Change - Traction Control Issues - 2007 C6
Thread Starter
1st Gear
Joined: Sep 2013
Posts: 1
Likes: 0
Tire Size Change - Traction Control Issues - 2007 C6
Hello,
I recently changed my rear tire size to 305/30/ZR19 from the stock 285/35/ZR19. Ever since this change the cars traction control system comes on at 100MPH. Can you change a setting in the programming to allow for this tire size change? I am somewhat confused that this happened given that the change is minimal (.65"). When you shut the traction control system off it works fine but that really isn't the answer. Any advice?
I recently changed my rear tire size to 305/30/ZR19 from the stock 285/35/ZR19. Ever since this change the cars traction control system comes on at 100MPH. Can you change a setting in the programming to allow for this tire size change? I am somewhat confused that this happened given that the change is minimal (.65"). When you shut the traction control system off it works fine but that really isn't the answer. Any advice?
Team Owner
Joined: Sep 2005
Posts: 20,352
Likes: 568
From: Ventura County, Calif
If in fact the diff is .65 it "might" be too much. And are you certain of the spec? Are you using a general diameter for that tire size or the actual manufacturer's spec for that specific tire? Tire sizes do differ from brand to brand for any given size.
This tire size and front/rear stagger stuff makes my head hurt so I don't try to keep up. I'm sure others will come by with help today so be patient.
For now I'll offer these quotes that might help get you started. Obviously ignore the specific sizes being discussed:
This tire size and front/rear stagger stuff makes my head hurt so I don't try to keep up. I'm sure others will come by with help today so be patient.
For now I'll offer these quotes that might help get you started. Obviously ignore the specific sizes being discussed:
Wolfdogs, I'm getting different numbers than you are. I'm showing a difference in diameter of .9" front to rear and a tire to tire difference of .300"
The OEM stagger is 1.2" with your new size tire you have dropped that to .9" (generally right around 1.1" wouldn't cause the problem). My recollection is that the EBCM has an allowance of 5% to accomodate tire wear. In making the change you have also changed the revolutions per mile. Above 70+ may be the sweet spot to aggrivate the wheel speed sensor calculations. Under normal circumstances with stock tires, your front tire would rotate 33 more revolutions than the rear in a mile. With your new size it is only rotating 24 times in that same mile.
The OEM stagger is 1.2" with your new size tire you have dropped that to .9" (generally right around 1.1" wouldn't cause the problem). My recollection is that the EBCM has an allowance of 5% to accomodate tire wear. In making the change you have also changed the revolutions per mile. Above 70+ may be the sweet spot to aggrivate the wheel speed sensor calculations. Under normal circumstances with stock tires, your front tire would rotate 33 more revolutions than the rear in a mile. With your new size it is only rotating 24 times in that same mile.
Tech Contributor
Joined: Oct 1999
Posts: 41,055
Likes: 9,817
From: Charlotte, NC (formerly Endicott, NY)
The stock rear tire diameter is 1.0466 times larger than the front diameter. Assuming you have a stock GY EMT on the front its diameter is 25.7 inches. Stock rear diameter is 26.9 inches. If you took .65 off the stock diameter that leaves you with 26.25 which is just 1.021 larger than the front tire. You are lucky that it only cuts in when you hit 100. If it was any smaller it might cut in as soon as the car starts to move.
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Programming a different tire size into the ECM may change your speedo and odometer readings but will not affect the EBCM which is the module that decides whether the wheels are spinning too fast or not. There is nobody outside of GM or their Supplier who can adjust any of the programming in the EBCM.
Bill
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Programming a different tire size into the ECM may change your speedo and odometer readings but will not affect the EBCM which is the module that decides whether the wheels are spinning too fast or not. There is nobody outside of GM or their Supplier who can adjust any of the programming in the EBCM.
Bill
Team Owner
Joined: Sep 2005
Posts: 20,352
Likes: 568
From: Ventura County, Calif
The stock rear tire diameter is 1.0466 times larger than the front diameter. Assuming you have a stock GY EMT on the front its diameter is 25.7 inches. Stock rear diameter is 26.9 inches. If you took .65 off the stock diameter that leaves you with 26.25 which is just 1.021 larger than the front tire. You are lucky that it only cuts in when you hit 100. If it was any smaller it might cut in as soon as the car starts to move.
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Programming a different tire size into the ECM may change your speedo and odometer readings but will not affect the EBCM which is the module that decides whether the wheels are spinning too fast or not. There is nobody outside of GM or their Supplier who can adjust any of the programming in the EBCM.
Bill
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Programming a different tire size into the ECM may change your speedo and odometer readings but will not affect the EBCM which is the module that decides whether the wheels are spinning too fast or not. There is nobody outside of GM or their Supplier who can adjust any of the programming in the EBCM.
Bill
Nice clear, concise explanation and my head doesn't hurt after reading it.
A generic version of that should be a Sticky or clearly available in the FAQ's.
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
Keep in mind that the size stamped on the tire isn't exact. It's as though each manufacturer had a different size ruler when they measured. A 245/40/18 from one manufacturer may measure @ 25.7" but the same 245/40/18 from a different manufacturer will measure as small as 25.5" or as large as 25.9. Since the calculated diameter is determined from the sidewall width measurement the diameter changes also.
There is no consistancy in reported sizes of tires.
There is no consistancy in reported sizes of tires.
Melting Slicks
Joined: Apr 2007
Posts: 2,987
Likes: 16
From: Phoenix
That's why I like Tire Rack's website. They list the manufacturers specs for all the tires they sell. I run a 305/30-19 rear with a 265/35-18 front. They are Michelin PSS's and I have no issues with traction control. If you have the stock width wheels I would recommend a 225/40-18 for a front tire. You may be able to get away with a 235/40-18 front, but it may still mess with your traction control. If you have at least a 9" front wheel, go with the 265/35-18.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
I've been running 265/35/18's front and 305/30/19's rear for quite some time. Hankooks on both ends. Never had a problem with numerous strip passes and Mexico runs well in excess of 130 mph.
Racer
Joined: Jul 2006
Posts: 348
Likes: 3
From: Toronto Ontario
The stock rear tire diameter is 1.0466 times larger than the front diameter. Assuming you have a stock GY EMT on the front its diameter is 25.7 inches. Stock rear diameter is 26.9 inches. If you took .65 off the stock diameter that leaves you with 26.25 which is just 1.021 larger than the front tire. You are lucky that it only cuts in when you hit 100. If it was any smaller it might cut in as soon as the car starts to move.
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Bill
To solve the problem you need to go to a smaller diameter front tire or replace the rear tire with the proper diameter. Remember the 1.04 ratio between front and rear. As long as you keep that ratio it doesn't matter what size tires you put on as far as premature activation of TC or Drag Control.
Bill
I was looking at running C5 rims with snows
225/50R17 fronts & 255/45R18 rears difference 1.18 ratio
That was the closest I could find (prefer going down the 1" to the 17s and 18s for the snow)
I used http://www.sizemytires.com/calculators/compare
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