Hi Bill and
![](https://i.imgur.com/evDSMvT.png)
to the forum.
The maximum motor rpm is also determined by the battery voltage rather than just the maximum rpm setting.
If your 36V battery is managing 15.6mph
(~262rpm) then a 48V battery should allow you to reach 20.8mph
(~350rpm).
There is nothing wrong with your motor, but after watching your video, I would say that your tyre seems to be poorly centred on the rim.
![Wink ;)](https://goldenmotor.com/SMF/Smileys/default/wink.gif)
Incidentally, using your 15.6mph as a guide, a 26" x 1.25" tyre on rear Magic Pie Edge should produce a top speed of ~19 mph on 36V and ~25.5 mph on 48V.
Alan