[Brumos RSR]

Up until this week I've trued tyres at 5V but decided to try at the lowest voltage possible without the motor stalling whilst grinding, 2.8V, keep the amp draw below 1.9A and...wait...I have to say the results are better than expected.

I was going to suggest 3 Volts, or like Kevan says slow.  I use 600 grit, 800 grit, 1500, then 2000 for a polishing.  Also don’t do this with the tire dry. Use something to keep the tires cool, water, dish soap, etc your choice.