Replacing a V-belt looks simple, and it is, if it is done in the right order. Most early belt failures we see trace back to the fitting: a belt pried over the flange, one new belt in an old set, or a drive that was never re-aligned. This procedure takes a little longer and gives you far longer belt life.
Isolate the drive, slacken the motor, remove the old belts, inspect and clean the pulleys, fit a complete matched set by hand without prying, align the pulleys, set tension, and re-check tension after the first hours of running. Never fit a single new belt into a set of used ones.
Loosen the motor mounting bolts and move the motor toward the driven pulley using the adjusting screws, until the belts are completely slack.
Lift them off by hand. Keep one old belt for comparison.
Move the motor in far enough that the belts slip into the grooves without force. Never pry or roll belts over the pulley flange with a screwdriver or bar: that breaks the internal cords, even if the belt looks fine.
On a drive with several belts, replace them all at the same time, with belts from one matched set. Belts in a set must be very close in length, otherwise the shorter ones carry the load and fail early while the longer ones slip.
Misalignment is a leading cause of belt wear and turn-over.
Move the motor out until the belts reach the right tension, then tighten the mounting bolts and re-check alignment. Use the deflection method in our V-belt tension guide, setting new belts toward the upper end of the range.
Refit the guards, remove locks, and run the drive. Watch and listen for flapping, squeal or vibration.
New belts settle into the grooves quickly. Re-check tension after the first few hours or the first day of running and adjust. Check again after a week.
Note the date, belt code, number of belts and tension. It makes the next replacement faster and shows whether a drive is eating belts.
| Mistake | Result |
|---|---|
| Prying belts over the flange | Broken cords, early failure |
| Replacing only the broken belt | New belt overloaded, old belts slip |
| Skipping alignment after moving the motor | Side wear, turn-over, noise |
| Re-using worn pulleys | Slip and glazing on new belts |
| No re-tension after run-in | Squeal, slip and glazing within weeks |
Keep spare belts in their packing or hung on wide pegs, in a cool, dark, dry store away from motors, welding sets and direct sun. Do not hang them on nails or tie them tightly, which can kink and crack them.
Should all V-belts be replaced at the same time?Yes, on multi-belt drives. Used belts have stretched, so a new belt would carry most of the load. Fit a complete matched set.
Can I roll a V-belt onto the pulley?No. Rolling or prying a belt over the flange can break its internal cords. Slacken the drive and fit the belt by hand.
How do I align V-belt pulleys without a laser?Use a straight edge or a tight string across both pulley faces; it should touch each pulley at two points. Adjust until it does.
How soon should new belts be re-tensioned?After the first few hours or the first day of running, and again after about a week.
Replacing a multi-belt drive? Send us the section, size and number of belts, and our team will supply a set for your drive.