Is the wiggling of treadmill belt alright i.e it moves like snake from left to right continuously? I am trying to buy a treadmill replacing the old one, but i have noticed that belts have slight movement in them that they shift there position from left to right and Vice versa if you look closely. Sometimes movement is very slight

It is my understanding that belt should move in straight line otherwise on high speeds it might hurt the knee because when foot is in the air and then it lands on the belt it might jerk towards the movement of the belt and there by hurt the knee in due course. I asked this question to the machine vendors they said although massive movement of this kind can be curtailed but slight to very slight wiggle will still remain

I am very skeptic about this. would some expert technician on treadmills please clarify my doubt as i am not satisfied by the answers I am getting. I would like to point out that I am aware of the belt movement towards only left or only towards right that can be set right by adjusting the belt from behind sockets with wrench key.

But I am not talking of that movement. I am asking about the movement of the belt that it moves from one side to another continuously giving it an effect as that of a wave/snake/tyre bubbling just to name a few if I am making my point clear. I have checked videos on youtube but there are not many which focus on the movement of the belt. in some that there are I can notice very slight movement of this kind if not much still. I am very confused.

  • How much wiggle do you see? 1" side to side? More?
    – rthsyjh
    May 14, 2012 at 9:54
  • @Jaydee i am unaware of the exact measurements. on a few it was significant, more than an inch. the vendors said that these need to be adjusted before delivery but the once they prepared even on them i would say it was half to one centimeter thou. some treadmills whose belts run under the curved edge of the side-stepper plate usually don`t appear to wiggle but looking under that gap one can see very slight wiggle still. thanks.
    May 14, 2012 at 11:41
  • Why do you think there's any uncertainty about this? Is it not clearly unsafe?
    – user3085
    Aug 12, 2012 at 21:08

1 Answer 1


This can be caused by a few things. Treadmills normally have leveling screws near the back roller (think pads on the bottom of a chair that screw in and out to level the legs). If the left side has more tension, the belt will slip left as it is run, same with the right side. If it is moving back and forth freely, more than likely, both leveling adjustments are a little loose and the pressure you exert on the belt left to right when you use it causes it to zig-zag.

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