Treadmill belt keeps slidding to the side - RTO Image 15.0R Treadmill Walking Belt

The first question is whether the tear is inline with the belt rotation or across it. The second question is how the particular make of treadmill you have controls belt tracking.

In general, the "right" answer to this question is to replace, rather than attempt to repair, the belt. You will need to carefully patch the back side of the belt with at least a couple of inches' overlap on all sides, carefully keeping the tear aligned as you do so, and then ensure that the material you used will not damage the deck or rollers, or stretch or start to come loose or fold over as the belt flexes and friction heat develops during running.

Many treadmills use lateral tension in the belt to keep it centered during operation (one or both rollers are gently tapered to be thinner at the ends). Any loss of lateral tension integrity will cause the belt to continue to be separated as it passes over these, perhaps widening or distorting the area of the tear or contributing to belt misalignment or 'walkoff' -- something that the usual dodge of blocking the treadmill slightly on one side won't help.

Usually if a belt slips off the pulleys, it's because of misalignment.
The belt is not tracking true, pulling to one side.

see the video and proceed and fix it. God bless you

http://www.youtube.com/watch?v=38w4PkiWIBY

There are Allen bolts on both sides of the bottom on the front (away from the console) of the treadmill. Turn one one way and the other the other way to adjust the belt. If this does not work, your belt is probably worn and stretched and needs to be replaced. See Treadmill Parts to order a new one.

Adjust the Allen bolts on both sides of the bottom rear of the treadmill. If that doesn't work, your belt is probably so stretched that you need a new one. You can order one at Treadmill Parts.

The belt does not need to be replaced more than likely. The problem is probably because that adjustment bolt is stripped out causing it loosen and keeping it over on that side. ProForm sells star washers that help them stay steady and not slip out. I would call them and ask for a couple of star washers and a new adjustment bolt for that left side.

If the walking belt slips when walked on. Using the allen wrench, turn both rear roller bolts clockwise, 1/4 of a turn. When the walking belt is correctly tightened, you should be able to lift each side of the walking belt 3 to 4 inches off the walking platform. Be careful to keep the walking belt centered. Carefully walk on the treadmill for a few minutes. Repeat until the walking belt is properly tightened.

it is an indicator that the belt needs lubricating. turn the power off, and lift up one side of the belt and spray a small amount of lubricant underneath the belt, onto the running board. repeat this step on the other side. turn the treadmill on and run it for a few minutes to spread the lubricant. the oil light should now go off.
this should be repeated every 5-6 months to keep the board lubricated and to reduce friction between the belt and board and will lengthen the life of your treadmill.

please look under the bottom of the treadmill and be sure that your alignment brackets are not benmt/missing. (put the machine in the storage position and look about 2/3 way down the side of the belt) you should see a metal bracket on each side pressing in on the belt. They should be pressing in about 1 1/2 -2 inches to help track the belt.

A good way to test your walk belt to see if it is slipping is to stand on side rails with treadmill running about 4mph and while holding onto handrails keep one foot on the side rail and put your one foot on the center of the belt in a slight stomping motion,if the belt is loose you will feel it slip. To adjust a loose belt tighten each screw at back of treadmill 1/2 tun each until the slippage goes away. Be sure not to over tighten belt as this will cause excessive wear.If the belt has shifted to one side and you need to center it, go to the side it has shifted to and turn the screw clockwise 1/4 turn at a time until it centers.