How is the VDC affected by tire size changes?
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Joined: Nov 2002
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From: St.Pete, FL
How is the VDC affected by tire size changes?
Reading the threads about new wheels and tires has got me wondering about the VDC's role in tire sizes.
I know that the VCD controls wheel spin mathmatically. I suspect it calculates the tire circumference and compares it to the actual distance traveled in one revolution of the axle. ...or... If the axle rotates more that 360 degrees before the car moves forward the distance of the circumference of the tire, the VDC senses slipping and applies the brakes to the offending wheel. Or...
Several people have posted about VDC problems when changing tire sizes on G35s. What part does the VDC play in tire size selection?
Do the new tire diameters need to be as close as possible to the original tire diamaters?
Do the new tires need to have the same ratio between the old front and rear tires as the new tires have?
Maybe the new tires could be progressivly larger than the originals and still work satisfactorily.
Help...
I know that the VCD controls wheel spin mathmatically. I suspect it calculates the tire circumference and compares it to the actual distance traveled in one revolution of the axle. ...or... If the axle rotates more that 360 degrees before the car moves forward the distance of the circumference of the tire, the VDC senses slipping and applies the brakes to the offending wheel. Or...
Several people have posted about VDC problems when changing tire sizes on G35s. What part does the VDC play in tire size selection?
Do the new tire diameters need to be as close as possible to the original tire diamaters?
Do the new tires need to have the same ratio between the old front and rear tires as the new tires have?
Maybe the new tires could be progressivly larger than the originals and still work satisfactorily.
Help...
Joined: Jan 2004
Posts: 21,095
Likes: 47
From: Toronto, GTA north
A sensor picks up the rotation of the wheels,
just like anti-lock picks lack of rotation.
In fact a lot of cars use the same sensor... not sure if the G35 does or not.
In simple terms...
The sensors should all equal each other. (+-)
If they don't the system will see the difference as slip.
This in turn is used in the VDC algorithm.
So, if aftermaket tires are all the same, there is little impact on the VDC system.
If you have different sizes front & back (stagger)
then you have to be careful to select tires that match each other (circumfrence).
This varies slightly between coupe & sedan.
The sedan VDC is designed for same front to back.
The coupe VDC is factored for the OEM stagger.
This is the calculator I use to compare sizes LINKY
just like anti-lock picks lack of rotation.
In fact a lot of cars use the same sensor... not sure if the G35 does or not.
In simple terms...
The sensors should all equal each other. (+-)
If they don't the system will see the difference as slip.
This in turn is used in the VDC algorithm.
So, if aftermaket tires are all the same, there is little impact on the VDC system.
If you have different sizes front & back (stagger)
then you have to be careful to select tires that match each other (circumfrence).
This varies slightly between coupe & sedan.
The sedan VDC is designed for same front to back.
The coupe VDC is factored for the OEM stagger.
This is the calculator I use to compare sizes LINKY
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