How to Identify Matching CIM Motors

We received 2 brand new CIM motors in our KOP this year (as did everyone this year) and we have 2 totes worth of graciously donated CIM motors. Some of which are used, and possibly some of which may be brand new.

We’ll almost certainly use 4 CIMs with the Toughbox Mini gearboxes on a kit chassis (2 motors per gearbox).


  1. Is it alright to pair a brand new CIM with a (to some extent) used CIM in the same gearbox?
  2. Besides visually inspecting the motors and seeing which ones look newer, what would be the best way to find equally performing motors? I’m thinking some kind of non-destructive torque test.
  3. Am I overthinking it?

look at the date codes?

Robots don’t seem to care too much about mixing up CIMS in the drivetrain. Yes, you’re over thinking it.

edit: from the AndyMark web page for the motors:

Motor Etching

Logo: AndyMark Logo
Voltage and Name: 12VDC 2.5" CIM MOTOR
CCL part number: PM25R-45F-1003
Manufacturing date: MMDDYY
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Hi, welcome. I hope your build season is going well.

  1. Cims are tough. As long as a motor hasn’t been excessively stalled I would pair a new with an old without hesitation.
  2. I don’t know there’s probably some kind of electrical test you could do but I wouldn’t worry about it. As long as you run the motor up and it sounds good I would say it’s probably good.
  3. Yes probably are.

We have successfully done that multiple years in a row.

We mount them in a makeshift plywood motor mount, run them for a few minutes at full output both CW, and CCW.

Then, we pair each motor with it’s closest performer.

There’s a difference between perfect pairing and good enough pairing.

We have typically gone with the good enough approach and our drivetrain is usually the most robust and reliable part of our robot.

Thanks everyone. We’ll probably just go with a visual inspection.

Just curious, do you measure speed/number of rotations with an encoder or listen to which sounds best?

I suppose you could stick two older CIMs in the same gearbox, but turning in opposite directions to stall each other.
Whichever way the gearbox turns determines the stronger CIM.
The winning CIMs get to play with the new CIMs.


horrible, horrible impact driver noises from AvE


If the donated CIM motors have pinion gears installed on them, make sure they have the same tooth count and are the same diameter as what you will be using on the two new motors. I think we may have installed an old motor with a different pinion in 2019 and the robot path always curved to one side whether it was going forward or backwards. It drove the programming team crazy.




CD actually stopped me from posting because:


Thanks, love you too.

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I wouldn’t worry about it. The cims are built ford tough and the design spec hasn’t really changed. I would suspect any combination of old and new motors would perform reasonably (ie within mfg tolerances) close to each other. As long as it isn’t so old that the brushes are gone (hint: it isn’t) I would still use it. Def have used newer and older cims together in gearboxes before with no appreciable issues.

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