Ok,
Gates apparently does not have nearly cautious enough lawyers. Talked to their techincal support person, and he said that the skipping was unlikely to have caused a problem to the belt.

In Gate's experience, skipping only causes damage to the belt if it rolls off in the process, which ours hasn't done.

So for now belt No 2 is not skipping even under heavy load, and is acceptably quiet, so we'll keep running it and see how it goes.

One other tihng I learned talking to Gates is that the system is now available with 69 tooth rings (as oppossed to the original 71 teeth). This is intended to make the belt easier to install, given the tight clearence on Co-Motions, even with the eccentric at its minimum distance.

Being a Beta tester with the first production lot can be a PIA. I'd lobby WebCyclery or Co-Motion (who ever you bought the kit from) for some swag as consideration for your field work on the belt.

Anyway, the 69t pulleys sound like the right approach based on all of the feedback thus far.

So my tandem racing friends with the Gates belt just finished an LD race. The captain got taken out with a stomach disorder at about 220 miles. He was picked up by the support crew, while stoker jumped one seat forward. She finished the last 60 miles of the race, solo. Time was good, and the Gates belt worked fine. Aren't tandems great?

Latest update: I've got the belt tensioned about as tight as it can be. It's not skipping, and its running quiet. I'm knocking on wood as I type though.

As large toothed belts can flex backwards as well as forward, proper tension is critical. If too loose, it will skip... one tooth flexes back, sending the force to the next & so on. This results in the entire crank jumping ahead. If it's too tight, the teeth will be pulled out of normal configuration, causing noise as they engage & disengage, this will wear the teeth out over time & could lead to cog wear from everyday grit & debris getting in there.

I love the idea of belt drives, but you really do need to maintain the tension correctly.

- Andy

Just to update this, this thread relates to the original Gates System.

We're now running the center track sytem, which we've had fewer problems with, and is discussed in other threads.