Why dose one side of my drive train is much harder to turn than the other

We have tried loosening and tightening everything and were stuck

Kitbot? Have you checked that the gears are in the right way, so the raised edge is against the bearing? That would cause that egarbox to turn much more difficult than one that’s properly assembled.


Are you using NEO’s? We had a similar problem last year and our solution was that the spark max motor controllers were in two different drive modes.

It could be only one motor connected on a side. Make sure your motor controllers are all blinking appropriately.

Check drive controllers are all in same brake/coast mode. Usually they are in brake mode for a quicker stopping action on the robot but it makes them hard to turn manually. Try putting them in brake mode when enabled then switching to coast mode a few seconds after they are disabled.
The time allows for braking action if the robot is moving when disabled and you can turn them easier manually.

You need to be systematic about solving the problem. In particular, isolate the cause.

Start by swapping motor controllers with the other side (leave the motors where they are), and see if the problem switches sides. If it does, then you have a problem in your motor controllers or software. If not, then it’s in your motors, gearbox, belts or bearings.

So, I’d pull the motors, get your programmers to spin them slowly in the same direction and make sure that they’re spinning at the same rate in the same direction. With the motors pulled, spin one of your wheels by hand and try the same on the other side (again with motors pulled) – is there more resistance? Assuming there is, disconnect belts and/or chain, and spin each wheel by hand, doing the same comparison – is one of them hard to spin or binding? If not, then re-attach belt/chain one wheel at a time and see what happens.

We’ve seen similar problems with bad hex bearings, overly-tight belts/chain, misaligned shafts, one motor not actually connected.

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I don’t think this sounds like the OP’s problem, but I wrote up instructions on how to do this.