sk1er17 said:
Im pretty sure it doesnt work out like that. Like 4.56 is a ratio, but dividing the circumference of the tire by it doesnt give meters per drive shaft rotation.
um, by definition it's impossible for that not to work...
the 4.56 means the drive shaft spins 4.56 times to spin the tires once
the distance the tires roll in one revolution is the circumferance
so 4.56 driveshaft revs turns the wheel once, and assuming no sliping, you travel the distance equal to the circumference of the wheel
so therefore if you divide the circumference by the revs to rotate the wheels once, you get the distance the wheels travel for one driveshaft rotation.
now if you multiply that by engine revs you get how far you would travel if the drive shaft were connected to the crank shaft.
now when you divide the calculated distance by the distance you actually travel you get the od ratio.
I wasn't far off I was off by .026 or 2.6%... here are the new calculations
km/h - wheel circumference in meters - Diff Ratio - OD Ratio - rpm
110 -- 2.23 -------------------------- 3.73 ------ 0.79 ----- 2427
110 -- 2.47 -------------------------- 3.73 ------ 0.79 ----- 2191
110 -- 2.64 -------------------------- 3.73 ------ 0.79 ----- 2050
110 -- 2.79 -------------------------- 3.73 ------ 0.79 ----- 1940
110 -- 2.23 -------------------------- 4.1 ------- 0.79 ----- 2668
110 -- 2.47 -------------------------- 4.1 ------- 0.79 ----- 2408
110 -- 2.64 -------------------------- 4.1 ------- 0.79 ----- 2253
110 -- 2.79 -------------------------- 4.1 ------- 0.79 ----- 2132
110 -- 2.23 -------------------------- 4.56 ------ 0.79 ----- 2967
110 -- 2.47 -------------------------- 4.56 ------ 0.79 ----- 2679
110 -- 2.64 -------------------------- 4.56 ------ 0.79 ----- 2506
110 -- 2.79 -------------------------- 4.56 ------ 0.79 ----- 2371
110 km/h = 69 mph
2.23m = 28" tire * 3.14
2.47m = 31" tire * 3.14
2.64m = 33" tire * 3.14
2.79m = 35" tire * 3.14
since the 110 km is comming from actual distance traveled, if you pick a tire size and ratio that results in rpms that are close to the results of stock ratios and tire sizes, you might not even have to re calibrate your speedo
Can people who have different gears and tires compare their RPMs and speed to this chart?
If the torque converter doesn't lock up, then there could be some variation depending on load