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.

Troubleshooting Your Belt Breaking

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.

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.


TENSION—Too little tension can cause 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 can cause the belt to overheat and add 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.

4 thoughts on “Mower Deck Belt Keep Breaking?”

  1. Have a JD D155 two years old. During the first year, the machine cut great. Beginning the following spring, the deck belt begin to snap off. I bought several belts, and the same thing happened. At one point I noticed a small branch flip up, hit the belt, and caused the belt to break off. I then built a guard that kept branches from hitting the belt, and all went well fit the rest of the summer. Then about a week ago, the same thing started to occur. I read up on possible causes on the Internet, ie , worn ir stuck pulleys, etc. I had mud buildup that i thought might have caused one if the pulleys to seize, so I took off the pan, scraped off all the mud, sharpened the blades, and put on a new belts. Went out for a test run, and the belt snapped within ten minutes. I would appreciate any advice, to include engineering defects or recalls.

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