It’s frustrating to have to stop mowing to reinstall a deck belt that came off your mower. This frustration multiplies when it continues to happen. You need to get this problem solved the right way so you can get back to mowing.
An Ariens lawn mower belt can keep coming off when the deck belt is loose, worn, or shredded; the tensioner bracket and spring are worn; debris interferes with the belt tension or sticks to the pulley grooves; there’s bearing failure in the pulleys or spindle housings, or the belt is covered with oil or rust.
Take the safety precautions outlined in your Ariens owner’s manual when working on your mower to prevent injury. Make sure your mower is unable to start while you are working on the mower deck.
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
Follow all safety instructions provided in your equipment operator’s manual before 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.
9 Reasons Your Ariens Belt Keeps Coming Off Your Lawn Mower
Loose or Worn Belt
An Ariens belt doesn’t last forever. It eventually wears from normal use and must be replaced. Look for signs of a stretched or worn belt.
A belt that is installed correctly that doesn’t sit securely against your pulleys may be stretched. A worn belt is one where it is showing signs of cracking, or fraying or has a shiny glazed appearance.
A belt that is sitting deep in the grooves of your pulleys is another sign your Ariens belt is worn. When you find any of these conditions, replace your Ariens belt.
I like using OEM (Original Equipment Manufacturer) belts. You can purchase those at your local Ariens dealership.
You can bring your belt to a local automotive dealership and have them try to match it up, but chances are you will not get an exact match. I have found these belts do not perform as well or last as long as OEM belts. Running an incompatible belt can pose safety risks.
Shredded Mower Belt
When your mower belt is shredded along the edges, you must identify the cause of the shredding and fix it. Not doing so will be costly as you keep going through Ariens mower deck belts. A shredded belt is weakened and susceptible to breaking.
There are a couple of reasons for your mower deck to become shredded. One reason is the belt has been installed incorrectly.
Make sure your belt is routed correctly by referring to your owner’s manual. You may also have a decal on your mower that shows how the belt is to be routed around your pulleys.
Another reason for a belt shredding is when a metal bracket is rubbed against the belt. Locate the bracket causing the issue and attempt to bend it back into place. Replace the bracket if you are unable to bend it back into place.
If it happens to be a bracket with a bushing, you may have to replace the bushing or bracket assembly. Still unsure which piece your belt is rubbing against? Look for a shiny smooth spot that is created from the rubbing.
Idler Tensioner Bracket or Spring is Worn
Take a look at the idler tensioner bracket and spring. You will typically find a pulley mounted to one side of the bracket and a spring attached to the other side.
The spring can become weak or fall off causing your belt to keep coming off your Ariens. Replace a bad bracket or spring.
The hole in your bracket can wear and become larger. This can cause excessive vibration. Replace a worn tensioner bracket or spring.
Debris Interfering with Belt Tension
Keep your mower deck free of debris. When debris collects in your deck and under your tensioner, the tensioner may not be able to move freely to keep sufficient tension on the belt. When this happens, your belt is more likely to fall off the pulleys.
Keep your mower deck clean and free of debris. Not only will this help keep your deck components working well, it reduces the likelihood a small fire could start from the friction of the hot belt with dry debris on the deck.
Debris Collecting in the Grooves of Your Pulleys
Debris doesn’t only collect under your pulleys and cause problems, mud can pack in the grooves of your pulleys. Small objects like stones and acorns can also get stuck in the grooves.
When your mower is running around the pulleys packed with mud or debris, it must stretch to go around additional material. This can cause the Ariens belt to slip off the pulley or break. To avoid this, clean any debris you find lodged or packed in your pulley grooves.
Bad Bearing in Your Pulley
Now that you have checked your belts as the possible cause for having to continually reinstall your belt, you need to check your pulleys. A bearing in your pulley can go bad causing your pulley to not sit flat and parallel to your Ariens deck.
When the bearing is bad the pulley can shift causing the pulley to sit higher on one side than the other. This shift can cause your belt to slip off the pulley and come off your Ariens mower.
Check each pulley on your deck checking for extra movement when the pulley no longer sits securely on the deck. Spin each pulley by hand slowly. Feel for a restriction or bearing noise.
If you notice up-and-down movement, a restriction, or bearing noise, replace your pulley. This is an indication of a bad bearing.
You will be able to replace the bearings in some pulleys. A pulley and bearing assembly must be replaced in others because the pulley contains a sealed bearing.
Bad Bearing in Your Spindle Housing
A bad bearing in your spindle housing can cause movement in the blade making it wobble when it is turned. With your Ariens deck fully engaged, this wobble can become a serious vibration that can knock off your mower deck belt.
To check for a bad bearing in your spindle housing, start by putting on a good pair of work gloves to protect your hands. Gain access to the underside of your Ariens mower deck. Grab a hold of each side of a blade. Rock the blade up and down.
If your bearing is good, you shouldn’t feel any movement or hear a knocking sound. When you do hear a noise and feel movement, remove your spindle housings and check the bearing.
The bearing can be replaced in most Ariens spindle housings. There may be some models where you must replace the whole spindle housing assembly.
Oil or Rust on Your Mower Belt
Your Ariens may develop an oil leak that can drip onto your deck and belt. Oil can cause your belt to slip off the pulleys.
It can even cause your belt to swell when it remains on it for an extended period. Find your oil leak and repair your oil leak. Clean oil off your deck and pulleys and replace your belt.
Rust can also affect your belt causing it to dry out prematurely. It will develop cracks and possibly break. When you find rust on the belt, clean your deck components to remove the rust. When the components are very rusty, it is best to replace them with new components.
Replace your mower deck belt with a new Ariens deck once your deck components no longer have rust on them.
Still Experiencing Problems with Your Ariens Lawn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your Ariens lawn mower.
You can find this guide at Common Ariens Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.
This will help you avoid personal injury or additional damage to the mower. Your local Ariens lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.