Thanks to SalMaglie:

Like it's been said, no set interval. Mine lasted until about 30.000 miles. I replaced it with a Thunderbird rubber, and got a bit tighter fit than stock. There should be no play with the cush drive rubber. If there is, it could cause the chain to stretch. The Tbird part # is T2012211.

Last edited by moe; 06/22/2007 4:20 PM.
A word to the wise is not necessary. It is the stupid ones who need the advice. Pat