Factory winter tire setting throws off 4WD?
08-02-2003, 09:55 AM
#1
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Factory winter tire setting throws off 4WD?
The owners manual says 265/35 R18 for winter tires. Comparing to the stock 295/30 R18 it is a good 8.5mm larger in diameter.
Here is how I calculate the difference.
295mm * (30/100) = 88.5mm
265mm * (35/100) = 92.75mm
(92.75 - 88.5) * 2 = 8.5mm
For each revolution the distance difference would be 8.5 * 3.14 = 26.7mm
Would the 8.5mm throw off the 4WD system or the odometer a bit?
Or it's within the tolerance? If so, anybody know the what the tolerance value would be?
Here is how I calculate the difference.
295mm * (30/100) = 88.5mm
265mm * (35/100) = 92.75mm
(92.75 - 88.5) * 2 = 8.5mm
For each revolution the distance difference would be 8.5 * 3.14 = 26.7mm
Would the 8.5mm throw off the 4WD system or the odometer a bit?
Or it's within the tolerance? If so, anybody know the what the tolerance value would be?
08-02-2003, 10:31 AM
#3
Burning Brakes
ypshan,
I assume your reference to the owner's manual is correct. Assuming it is, it looks like you did the math right. Although that is what it is all supposed to mean, tire manufacturers do not always meet the aspect ratio/tread width criteria to a T. You really need to obtain the specifications for the actual tire you are planning on using and compare it to the actual stock tire. That said, a change in diameter will most certainly affect your odo/speedo. That is not the end of the world. The important thing, however, is that the front and rear wheel diameters be within about 1/4" of each other's overall diameter so as not to overtax the viscous coupling. The greater variation in front to rear tire diameters, the greater amount of heat needs to be dissipated by the viscous coupling.
I assume your reference to the owner's manual is correct. Assuming it is, it looks like you did the math right. Although that is what it is all supposed to mean, tire manufacturers do not always meet the aspect ratio/tread width criteria to a T. You really need to obtain the specifications for the actual tire you are planning on using and compare it to the actual stock tire. That said, a change in diameter will most certainly affect your odo/speedo. That is not the end of the world. The important thing, however, is that the front and rear wheel diameters be within about 1/4" of each other's overall diameter so as not to overtax the viscous coupling. The greater variation in front to rear tire diameters, the greater amount of heat needs to be dissipated by the viscous coupling.
08-02-2003, 12:28 PM
#4
Nordschleife Master
http://www.tirerack.com/tires/Spec.j...em+Asimmetrico
A 295/30 R18 has a diameter of 25", a 265/35 R18 has a diameter of 25.1"
A 295/30 R18 has a diameter of 25", a 265/35 R18 has a diameter of 25.1"
08-02-2003, 03:20 PM
#6
Rennlist Member
I don't see how the math can be right. The aspect ratio applies to the ratio of the height of the tire road-to-rim/ overall height of tire. The section width is an unrelated measurement, as far as I know. Please enlighten me if I'm wrong. AS
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08-03-2003, 02:12 AM
#8
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Alexander,
The math seem right acccording to the example below.
http://tirerack.com/tires/tiretech/general/size.htm
The math seem right acccording to the example below.
http://tirerack.com/tires/tiretech/general/size.htm
08-03-2003, 02:26 AM
#9
Burning Brakes
Alexander,
A tire's aspect ratio theoretically pertains to the the sidewall height divided by the tread width. Some tire companies take liberties in both directions. That is why I suggested looking at the specifications for the tires.
A tire's aspect ratio theoretically pertains to the the sidewall height divided by the tread width. Some tire companies take liberties in both directions. That is why I suggested looking at the specifications for the tires.
