Mower Deck Belt Keeps Breaking?

Need some help because your lawn mower deck belt keeps breaking or wearing down? Let us help. Keeping your lawn mower deck belt in top working condition is important to keep your machine running smoothly. It is good practice to replace your belts yearly, to check belts regularly, and fix any issues that arise to keep your mower at its best. If you need more help diagnosing and fixing your issue, bring your mower into an authorized dealer.

Below, we have listed common problems with the most likely cause of the problem. We also have provided more information regarding maintenance and the design of John Deere V-Belts. If you need more help, leave us a comment, or use our Live Chat during business hours on!

Troubleshooting Your Belt Breaking

To diagnose your belt, read our information below.Cracking in the base with little side wear is probably due to a defective belt. The best solution to this is to simply replace the belt. Base Cracking with badly worn sides is probably due to a damaged belt. The best solution to this problem is to simply replace the belt. If problem persists, there may be a bigger problem. Fabric Rupture is typically caused by prying the belt onto the sheave, worn sheaves, or the belt being too tight. To solve this issue, you will need to replace the belt. Before installing the new belt, loosen the belt tighteners. Then, be sure not to tighten the belt too much. A belt that is “cover torn” is coming into contact with some part on the machine. To solve this problem, you must find the interference and eliminate it. Once you have solved the issue, replace your belt. A V-Belt with slip burn is typically caused by a loose belt. When operating under load, a loose belt will grab and snap. To solve this problem, replace your belt, and tighten the belt properly during your next install. A belt with gouged edges has been damaged by the sheaves or has had interference from some part of the machine. Check the conditions of sheaves and check for interference. When you have corrected the problem, replace you belt and watch for more signs of wear. If problem persists, consider bringing your mower into your local Authorized Dealer.

View Mutton Power Lawn Mower Service information if you live around Fort Wayne Indiana. Ruptured Cords on a V-Belt is probably caused by the drive sheave locking and burning an area of belt because the belt would not rotate with the sheave. Replace your belt, then avoid overloading the drive. Also, lubricate the bearings to prevent bearing seizure. Worn sides on a V-belt is commonly caused by long operation without enough tension. Regularly check the v-belt and tighten it if needed.

Shop our John Deere Belts or Exmark Belts!


TENSION—Too little tension causes slippage or slip-and-grab, causing the belt to break. If the belt does not break, slip will cause excessive cover wear, burned spots, and overheating.

Too much tension causes belt overheating and excessive stretch as well as damage to drive components, such as sheaves and shafts. The extra tightness will also place heavier loads on the bearings.

Remember that V-belts should ride on the sides of standard sheaves, not on the bottom of the groove.

WATCH THE TENSION ON A NEW BELT DURING THE FIRST 24 HOURS OF OPERATION—This is when the initial seating and stretch occurs.

ALIGNMENT—Sheave alignment is important. Be sure that the shafts are parallel and the belt aligns with each sheave.


The illustration below shows important areas of a typical V-belt cross section. Each area plays an important role in belt performance. The top section of the belt is the tension section. It is rubber and stretches as the belt forms around the sheave.

The bottom section is called the compression section because it compresses when wedged into and shaped around the sheave.

The center section of the belt is the strength section. It neither compresses nor stretches, but the cords located in this area give the belt its tensile strength. Without these cords, a V-belt would be pulled apart.

The complete belt is covered by a tough fabric and rubber which protects the inner parts.

NOTE: Some V-belts have a corrugated underside for greater flexibility.

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