Drive roller shaft not fully seated in bracket - tracking issues (NordicTrack C1650)

I recently purchased a used NordicTrack C1650, ~750 miles on the machine. Overall great shape, the only thing I noticed was the walking belt was in need of lube. I did have to diagnose a motor issue (another story) so I didn't really use it before loosening the walking belt and pulling the motor. I had the unit apart for a few weeks until I reassembled yesterday.

I reassembled it yesterday and cleaned everything really well. After tensioning the walking belt and getting it to track on center, I applied 0.5oz of Icon OEM lubricant. The walking belt slides nicely and is MUCH better than before. The rollers don't slip when applying a load to the walking belt, so I believe the walking belt is sufficiently tensioned. The walking belt tracks nice and centered at all speeds (without someone on it).

I tested it out and the weirdness started when I started a light jog (5mph). I noticed the walking belt creeping/tracking to the right slowly until it got to the limit (maybe in 30 seconds or so). I jumped off and the belt slowly tracked back to center.

I believe I know what the issue is. I noticed the drive roller shaft (left side, where the drive belt and pulley is) is not fully seated within the bracket. The bracket has a slot, and tension from the walking belt pulls the shaft into the slot while tensioning the drive belt at the same time. I believe it should bottom out in the slot. Otherwise the shaft is free to move with the varying loads which will affect tracking. When I began running, the increased torque from the motor pulls the drive roller towards the motor slightly. Left side of front roller moves forward = walking belt tracks right.

Here is a diagram of what I'm talking about:

I did tension the walking belt more to seat the shaft into the bracket, but the walking belt seemed way too tight so I backed off for now. Unfortunately I didn't pay close enough attention when disassembling and this is the only treadmill I've worked on, so I don't have much of a reference for how tight the belt should be. I'm using the original drive belt, so I don't know what else could change that would affect this alignment. Unless the drive belt and walking belt just need to be stretched out again after sitting relaxed for a few weeks...

Hoping someone can send over some advice! Thanks!


  • edited March 31
    As resistance is applied to the walking belt on each step, the extra tension in the drive belt moves the shaft left (towards the motor) causing the walking belt alignment/tracking issue.

    I learned this treadmill has a stretch drive belt, as opposed to a drive belt that is tensioned by moving the motor or adjusting an idler. In this case you have to apply enough tension to the walking belt to keep the drive belt sufficiently tensioned and maintain the position of the drive roller in the bracket. Once I applied a lot more tension (I could actually see on the adjusting screws where the old position was set), this issue went away and the walking belt is tracking fine now under load.
  • whoo hoo that is great news you were able to get it fixed! thank you for sharing!
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