Most of the time its an alignment issue.
Agreed, but if after proper alignment the squeek does not go away, it becomes tough to track it down.
I have been dealing with this all year.
I have read what ever I could find about this and how to fix.
Adjusted tension at least 10 different times from min. deflection of 5/8" to max deflection of 3/4".
I have used straight edges, belt alignment tools, checked torque on motor mounts, etc.
I finally pulled the rear wheel 2 weeks ago because the noise was so excessive I was convinced that the bearings had gone bad and that could cause the wheel to become misaligned while riding.
What I found was that the bearings did not have any catch in them, belt was in good condition but the teeth on the pulley seemed all chewed up. The tops of the teeth on the pulley are flat as well. Have not confirmed if they should be rounded but I assume they should be since the belt has round teeth.
All I know is that I put some graphite along the belt and on the pulley and can not make it squeel if I tried now.
In an earlier post Dogvet said that some of the pulleys just have not been standing up.
The shitty thing to me is that I am going to end up dropping about $650.00 on a new pulley and belt to fix a squeek.
If I wasn't so embarassed I would just spend $2 on some good earplugs and not worry abut it. But I bought a BDM so people WOULD take notice of the bike. Only now they are looking for the wrong reason.