another CDX diagnosis
 

Maybe this will help someone in the future... I just picked up a new Gates system, and came across a problem I hadn't seen mentioned here before. I measured both distances to centerline and got them matched up. There was a periodic buzzing as the cranks were rotated, so I thought that maybe it was the old non-centered chainring bolt problem. Tried to address that with some folded paper shims between the crank spider and chainrings. Chainrings looked good after that but still buzzing. I finally noticed that a chainring was wobbling side to side. Took it off, laid it flat on the counter...looked good. It turns out that the crank's spider had a bent leg that wasn't really noticeable with the chain drive. Bent that back into line and the belt is now smooth and quiet. Hopefully I can get it out for a test ride in the near future. Seems pretty sweet so far!

what brand, model, year cranks are they?

How did you bend it back inline?

The cranks are a mystery FSA Octalink compatible model. (The last thread I started wad actually in regards to ID'ing them.)

To straighten the bent leg, I passed a screwdriver through the cut out in that leg (with the chainring removed) and pryed it back straight again. It was probably about 2mm out to start.

Glad you were able to straighten that spider arm, but the crank sounds a bit sketchy to me. Is it alloy or carbon sandwich?

The "buzzing" as you called it can be reproduced with any new CenterTrack install that is more than a couple millimeters out of alignment between the front & rear timing rings, or as in your case with a bent spider arm.

The arms are carbon sandwich. The spider is aluminum and removable via two screws. I wouldn't say there's anything sketchy. It probably just took a ding at some point in its history.