[Triathlon 2013]

I acquired a vision fitness T8100 treadmill last year. We have had to replace the belt--and adjusted it accordingly. Now the treadmill has this "thumping" noise when I run on it. My husband thinks it is from bearings in the rear roller going bad. I haven't been able to find a rear roller for this treadmill and have been searching pretty dilligently. Does anyone know if the whole roller has to be replaced as a whole unit or if the bearings are replaced separately--or if this doesn't sound like a bearing issue.

It is part number Z81TM06-009 Rear Roller Set.

Thanks! Triathlon 2013