Before you put the tape on measure your balancer circumference to make sure your accurate. I just measured mine and it not excactly 6.75, its a 1/16 larger. So for mine it would convert from 6.8125 to 173.0375 mm X pi = 543.61332. Just saying to make sure measure the balancer diameter.
==== BOB ====
If I can't smoke the tires I want more!
1976 Chevy Nova
2007 Chevy 1500 1/2 ton
2008 Harley Davidson XL1200 Sportster