Installing your Cub Cadet mower belt only to have it come off again can be frustrating! Changing your mower belt can be a pretty time-consuming task especially if you need to remove your mower deck like you have to do for Cub Cadet riding mowers.

You need to isolate the main issue that is causing your belt to come off.

Your Cub Cadet mower deck belt keeps coming off because the belt is worn and stretched; the belt keepers or brackets are damaged; the bearing is damaged in a pulley or spindle housing; the debris is interfering with your belt tension, or oil has collected on the belt.

There are several items you need to check on your mower deck so you don’t have to keep replacing your mower belt. These can be checked and fixed with a few simple tools.

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Reasons Your Belt Keeps Coming Off Your Cub Cadet

Loose or Worn Cub Cadet Belt

Look at your belt and check to make sure it is fitting tight. If it seems loose, this could be a sign that your belt is getting worn and stretching from normal use.

Other indications it’s time to change your worn Cub Cadet belt is when the belt has a glazed and shiny appearance to it or it is starting to show signs of cracking.

Cub Cadet Belt Keeper Damage

Some Cub Cadet mowers use belt guide keepers on their mower decks. These are small rod-shaped posts that sit along the side of the pulleys. Belt keepers help ensure your belt stays in place.

The keepers sit about 1/8” to 1/4” away from the pulley so your Cub Cadet belt shouldn’t be rubbing against it.

The belt keepers can move out of place or become bent. This often happens with the belt has slack in it and hits the keeper. This can sometimes cause the belt to come off your Cub Cadet.

Sometimes it is easy to bend the keeper back into place using a hammer or other tool. If that doesn’t work, you should replace it.

Shredded Cub Cadet Belt

A shredded belt can be the result of your belt rubbing against a belt keeper or a bracket on the deck. Another possibility may be your belt is not actually routed around the deck components correctly.

You’ll want to confirm your belt is installed correctly and check for any parts of the deck the belt is rubbing against.

A shiny piece of metal on your deck is a good spot to check to see if the belt is rubbing against that piece. Once you find out what the belt is rubbing against, you’ll need to adjust it so there is no more rubbing.

If the part the belt is rubbing against happens to be a bracket with a bushing, you may be able to replace the bushing or you may have to purchase the whole bracket assembly.

Damaged Bearings in Your Cub Cadet Pulleys or Spindle Housings

A Cub Cadet belt that is coming off your mower can be the result of bad bearings in your pulleys or spindle housing assemblies. Take a look at each one of your pulleys.

Make sure they are running flat and parallel to the deck. They should not be sitting higher off the deck on one side than the other.

If they are not running flat, your belt can jump off the pulley. Most of the time, when you experience this in your pulley, it is the fault of a bad bearing in an idler pulley and the pulley must be replaced.

Idler pulleys have a sealed bearing so the whole pulley needs to be replaced.

Your issue may be with the spindle housing assembly. A problem in your spindle housing can cause your Cub Cadet to vibrate and knock your belt off a pulley.

To check your housing, make sure you’re wearing a good pair of work gloves so you don’t cut yourself on the sharp blades. Also, make sure the ignition key is removed and the spark plug boots are removed for safety.

Grab a hold of each side of the blade and rock the blade up and down. Listen closely for a knocking sound. You’re also feeling for any movement when rocking the blade. 

If you find either one of these symptoms of a damaged spindle housing, you’ll have to take the spindle housing apart and check for a bad bearing or other problem in the housing. Some spindle housings are sealed and the whole assembly must be replaced while others can be rebuilt.

Cub Cadet Idler Tensioner Bracket or Spring is Worn

Your mower deck will have a tensioner bracket and spring that hold the idler pulley in line. The bracket typically has a pulley on one side and a spring on the other side.

The hole in the bracket where the spring is attached can become worn or the spring itself can become worn. When this happens, a vibration is created that can make your Cub Cadet belt keep coming off.

Debris Interfering with Proper Tension on Your Cub Cadet Belt

Not cleaning a mower deck after each mowing is very common, but it shouldn’t be. Your deck needs to be kept clean of debris because the debris buildup can collect on your deck and cause your tension pulley not to move like designed.

When it’s not able to work correctly, there isn’t proper tension on your belt. Your belt can become loose and come off your Cub Cadet.

A side note: not only is it important to keep your mower deck free of debris so it works properly but keeping your deck clean can also prevent your mower from catching on fire.

When dry grass clipping, leaves, and other debris collect in the area around your belt, the heat of the belt can catch those items on fire.

Check out our articles, “How to Clean Your Lawn Mower for Best Performance” and ” How to Find & Prevent Substantial Lawn Mower Deck Problems ” to learn more on how to keep your mower clean and in good condition to extend your mower’s lifespan.

Debris in Grooves of Your Cub Cadet Pulleys

Your pulleys can collect debris, like stones and wood chips, that may get caught in the grooves or under the pulley. Something as simple as packed mud around your pulley can cause your belt to come off your Cub Cadet, or worse yet, the belt can break.

Belts can break, whether they are old or new when they are stressed by having to stretch around additional materials.

Oil or Rust on Your Cub Cadet Belt

Mowers can develop oil leaks. When that oil leaks into your pulleys and belt, the belt can come off. Oil can also cause your mower belt to begin to slip and just build heat when it is not able to grab a hold of the pulleys.

In addition to oil damaging your belt, rust build-up can also cause damage. Rust causes your belt to dry out and crack. When you notice rust or oil on your belts, you must clean your pulleys and replace your belt.

In Summary

Cub Cadet deck belts can be pricey so you don’t want to replace the belt any sooner than you need to. Following these steps will help extend the life of your Cub Cadet belt and keep it from falling off:

• Clean your mower deck after each mowing to remove debris
• Check for rubbing on deck components
• Keep oil and rust from forming on your belt
• Periodically check your pulleys and spindle housings for bearing failure
• Fix or replace any damaged brackets or belt keepers

Related Items

Change Your Cub Cadet Riding Mower Deck Belt

If you’re a little nervous about your abilities to change your Cub Cadet deck belt, I’ve written a guide to help you. Changing a deck belt isn’t as hard as it seems even if you need to remove your deck from your lawn mower.

A little bit of strength to slide your deck from under your mower and a few tools to remove some nuts and screws is all you need.

Check out my article, “How to Replace a Cub Cadet Mower Deck Belt“. This is a guide to changing a belt on a Cub Cadet riding mower.