Figuring out wheel speed

[mega2006]

Can someone help me figure out how to take me TOS speed of 2003 rpms, stock rear gears and 37's to figure out what my wheel speed was? I tracked on my GPS to be around 17 mph ground speed but wondering what wheel speed was. I should have said this was logged in my 06 5.9 in 4 low at a sled pull. Any help? :thumb_yello:

[cumminsDK]

Can someone help me figure out how to take me TOS speed of 2003 rpms, stock rear gears and 37's to figure out what my wheel speed was? I tracked on my GPS to be around 17 mph ground speed but wondering what wheel speed was. I should have said this was logged in my 06 5.9 in 4 low at a sled pull. Any help? :thumb_yello:

Pretty simple go drive on road at 2003 rpm TOS speed and check your mph (in low range)
, there will be no wheel slip on the road so that will give you true wheel mph, unless of course you want wheel speed in rpm

[WyoFreeride]

Speed = (RPM * Tire Diameter * Pi * 60) / (Final Gear Ratio * 63360)

Pi ~ 3.1415926
Final Gear Ratio is the ratios of everything after your Speed sensor multiplied together (ie, 3.73*2.72= 10.1456 maybe in your case?)
Tire Diameter is in Inches, and should be a measured value, not what it says on the tire.

For what you stated, assuming 3.73 gears, 2.72 low range and actual 37" tires, your wheel speed should have been around 21.7 mph.

-Joe

[mega2006]

Wow Joe.....thanks for the math class! I am going to go out and try the TOS speed w my GPS and see how they compare to the math you just did! Thanks for not only laying out the formula for me but plugging in the numbers as well! Much appreciated!:thumb_yello:

[joecar]

That simplifies down to this:

MPH = RPM * TD / GR / 336

(where: GR = overall gear ratio, TD = tire diameter inches)

:)