Join Date: Jan 2011
Location: west Texas, , USA
general math looks a little like this based on very general numbers
160-60-17( the only loose tire wheel combo I had laying around) has a circumference of 80"
One mile = 5,280 feet
5,280 feet = 63,360 inches
60mph = 1 mile per minute
Distance / Circumference = 792 revolutions per mile
Revolutions / time to cover distance
792 revolutions per mile / 1 minute per mile = 792 rpm
800rpm doesn't seem like much until you figure in wheel diameter and weight and tire weight, the numbers get pretty big pretty fast.
now lets see at 200mph thats roughly 2560 rpm the wheels are turning at,,covering approximately .27 mile or roughly 1/3 mile in 5 seconds uh uhm yeah it's already a mile BEHIND ME!
OK enough with the stupid math tricks here's the real deal wheels are rough cast for bikes. And they are not round as cast. Wheels are then center drilled for the axle next turned on a lathe(most likely a cnc) to get the wheel mounting lips and flange and outside finish areas round and centered to the axle. This process is quick simple and easy but doesn't assure static balance as spokes rim centers etc may not be perfectly centered. I discovered this years ago when polishing wheels on sportbikes became the next big thing. You could spin the wheel on the bike to polish it and it was perfectly round on the machined surfaces but when you got onto the cast areas it could be as much as 1/16th inch difference from the high to low spot!
We mount our own tires and balance them with a static manual spin balancer. Years ago I got into the habit of balancing my wheel BEFORE mounting the tire by removing small amounts of metal from the heavy area until the wheel was balanced. IF you have a wheel with a small imbalance and a tire with a small imbalance and by sheer coincidence you place the 2 together your going to need more weights!
Another fact to consider is if you have an unbalanced wheel and unbalanced tire and you mount them, the balance is off, break the bead rotate the tire on the rim and try again.
We run Pilots on Marie's Racebike and last time we went through 3 NEW tires before we found one that required very little weight to balance!.
Although your mechanic won't like it he should be able to rotate the tire on the rim to get you closed to static balance, if your doing it at home yourself balance your rim THEN mount your tire. so the numbers above tell you why we spent so much time balancing wheels but in the long run this is something that can benefit every rider on any bike if they want to spend a little time.