----- Original Message -----
From: "David Lieb" <dbl@chicagolandmgclub.com>
Subject: Re: As the wheel turns
> If anyone else is willing to duplicate this ...
All I know is that bicycle speedometers want you to mark where the wheel
touches the ground on both the wheel and the ground, roll it forward with
your weight on the bike until the mark touches the ground again, mark it and
measure between the marks. Talk about begging the question!
******************************
Something Paul Tegler said helped me figure out why the loaded circumference
of the tire does not correspond to the distance the tire rolls in one
revolution.
Say, for example, you have an unloaded tire with a circumference of 80
inches and, when the tire is squashed by putting the weight of the car on
it, the contact patch takes up a length of the unloaded tire's circumference
of 8 inches -- or 1/10th of the total circumference. Now, since the 8 inch
arc of the tire is now in a flat, straight line where it contacts the
ground, it takes up less distance -- the shortest distance between two
points is a straight line not an arc. If that flat contact patch is now
only 7 inches long rather than the 8 inches of arc when unloaded, then the
sum of the 10 contact patches going around the tire is 10 times 7 inches or
70 inches. So the 80 inch circumference tire in this example will travel 70
inches in one revolution.
Larry Daniels
79 MGB LE
72 Midget
58 Bugeye
"You only need two tools: WD-40 and Duct Tape. If it
doesn't move and should, use the WD-40. If it
shouldn't move and does, use the duct tape."
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