Strange misalignment / tensioning issue on Y-rails

I noticed as I was fast moving along Y that the cutter frame would “tilt down” when moving forward (negative Y). Upon further inspection, I noticed that after a jog forward, the front part of the belts would be very tight (like a drum), while the rear were normal / looser, and that three of the four wheels on the Y rails would rotate freely. When I jogged backward (+Y), two of the wheels made solid contact (diagonal to each other) and both the front and back belt would be normal tension.

How should I resolve? Just release all four holds on the belt, let the frame rest solidly on the rails, and then re-tension all four belt points?

Hi @sdrevik,

It sounds like your wheels eccentric nuts should be adjusted such that the wheels all contact the rail at the same time, regardless of movement direction. The belt issue is very likely just a side effect of your vwheels not being quite like they should.

There’s a great video on, “Getting Started With Shapeoko” section, chapter 04 Checking Machine Assembly. At 05:21 in that video, @KevBarn14 goes over how to adjust the vwheels on a Shapeoko3/4

I would suggest you un-tension both Y belts, proceed to tune the nuts on the 8 vwheels (left and right Y axis), and then only proceed to retension the belts.

If you continue to have trouble, you can also contact


Yes, thanks, that did it.

While working with the adjustments, I also found that one of the four screws holding the wasteboard to the frame had come loose and one corner was significantly higher, so I got that fixed as well.

Two things to put on the ‘regular maintenance list’ for the SO3.