88rxn/a

ive tried online calculators with no luck!!
im trying out a friends Xcal3 to see if i like it but i cannot figure out the tire revs per mile!
the tires are:
mastercraft courser C/T
33X12.5X17

ak_cowboy

I googled diameter to circumference. A 33" tire will have a circ of 103.7", which equals 8.64 ft. 5280ft/mile -----> 611.1 revs/mile.

let me know if I screwed up, but I believe it's right.

Here's a site I just found.
http://www.gordon-glasgow.org/tirecalc.html

kozal01

iTrader: (2)

theres a couple different ways of doing it. this one will get you close, assuming the diameter of the tire is close to the actual size of 33". multiply 33 by pie and the number comes out to 103.67 and some change which is the circumference of the tire inches, now divide one mile up into inches which is 63,360" and divide 103.67 into that and you get a rounded off number of 611 which would be your revs per mile. a more accurate way would be to wrap a measuring tape around the circumference of the tire with the weight of the truck on it, take the measurement in inches and divide that into one mile converted to inches and youll get a more accurate tire revs per mile measurement. hope that helps, im no math major but thats how i figured it out on my X-cal.

shotgun

Keep in mind that the 33" is unloaded. Accounting for squish, the actual revs/mile will be between 630 and 642.

ak_cowboy

^ Good point.

O.P. Why do you want to know revs/mile anyways?

kozal01

iTrader: (2)

the X-cal uses that info to correct the speedo for larger tires and/ or different gearing.

ak_cowboy

Gotcha.

Kattumaram

Jack up a wheel and put a tape measure around the tread at the center. Whatever that measurement is is the distance the tire will travel for each turn. Whether the tire is loaded or not that distance doesn't change.

shotgun

Unfortunately that's not true as the tire compresses as it rotates (when it's loaded).

The other way is to mark a spot on the tire and on the driveway. Drive forward or backward one full tire revolution. Mark the driveway. Measure the distance between the two marks.

S13minus1

a circle isnt going to stretch or shrink. it will compress, but the compressed distance is still in contact with the road.