Treadmill belt slipping
Written by Jamie Miller, Founder & EditorLast checked
A belt that hesitates or lurches as your foot lands is almost always too loose.Tightening the rear roller bolts a quarter turn at a time, evenly on both sides, fixes most cases. If it slips while nobody is on it, or the machine smells hot, stop and treat it as a motor or drive-belt problem instead.
Work out which kind of slip it is
- Slips only under your weight, at foot strike. Running belt tension. The section below covers it.
- Slips with nobody on it. That points at the drive belt inside the motor cover, which is a different part and a different job.
- Slips and feels sticky rather than loose. Friction, not tension. Lubrication is the more likely cause.
Tightening the running belt
Your manual gives the correct tension for your machine and it should win over anything here. The general method:
- Unplug the machine.
- Find the two adjustment bolts at the rear, one at each back corner, usually taking an Allen key.
- Turn each one a quarter turn clockwise. Both sides, the same amount. Uneven adjustment is what sends a belt off-centre.
- Plug in, walk on it at a slow speed, and see whether the hesitation has gone.
- Repeat a quarter turn at a time until it stops. Stop as soon as it does.
Over-tightening is its own fault: it loads the rollers and the motor, and a belt you cannot lift a few centimetres off the deck at the centre is too tight. Tight belts wear bearings.
When to stop and call someone
Stop using the machine and get a qualified engineer if any of these appear: a burning smell, a belt that slips with no load on it, a grinding sound from under the motor cover, or a breaker that trips when the machine starts. These involve the motor, drive belt or wiring, and none of them is a job to work out from a web page.
What we have not established
We have not measured belt tension against slip on any machine, and we have no data on how often a slipping belt turns out to be the drive belt rather than tension. The ordering above is drawn from manufacturer maintenance guidance, not from our own testing.How we review.