Bearings: Flatbed Trailers


There are many questions when it comes to the bearings of flatbed trailers. No matter the style of flatbed trailer, we have you covered! Below are the answers to some of the most frequently asked questions.

What Can Cause a Bearing to Fall Out of the Hub?

The most common reason a bearing falls out is the diameter of the hub bore being wrong. Another reason is that the spindle being too long, which can cause the nut or cotter pin on the end of the spindle to push against the bearing piston (when the grease level is low, forcing it to eventually fall out of the hub. Also, wearing down of the bearing caused by excessive removal and re-installation can decrease the interface fit between the bearing and the hub bore. Bearing torque that is out-of-balance can cause excessive wobbling of the wheel and thus cause the bearing to work its way out of the hub.

How Do I Determine Replacement Wheel Bearing Sizes?

All types of trailers wheel bearings, including flatbed trailers, are specific to the spindle that is installed on the axle on your trailer.

To determine the wheel bearing size, you will first need to safely support the trailer. Once you’ve done this you can remove the wheel and tire, then the grease cap, the cotter pin and washer that secure the spindle nut and then the spindle nut itself. Then you will be able to remove the hub from your trailer.

Once you’ve done this, you can get the part numbers from the inner and outer bearings to determine the correct replacements parts for your spindles.

How Do I Check the Grease Level in the Hub?

Grease can be added to the hub through the center of the bearing piston. The lubricant level can be checked by pressing on the edge of the piston. The hub is properly filled if you can rock or move the piston. If not, grease needs to be added until the piston moves outward about 1/8 inch. Use a hand grease gun when adding grease because an automatic grease gun will destroy the inner seal of the hub.

How Do I Install Bearings for Flatbed Trailers?

Whether you are installing or replacing your flatbed trailer bearings, you will need a pair of pliers, a lug wrench, a hammer, a flathead screwdriver and the necessary means to jack the wheel up safely. Start by loosening the lug nuts with the lug wrench. Once the wheel is safely up in the air, just follow these simple steps.

Once you have completely removed the lug nuts and tire, follow by removing the dust cap or, if you are using one, the bearing protector. The dust cap can be removed by using a screwdriver to pry it off, but a bearing protector will most likely require a few light taps with a hammer. The cotter pin that holds the castle nut in place will need to be straightened out and removed to gain access to the bearings. Then the castle nut and washer can be removed.

The next step is the removal of the wheel hub, which can be done by simply sliding off the central spindle. Once this is done, pull the outer bearing off the hub. If the outer bearing is stuck you might have to rock the hub or tap it with a mallet. Next, lay the hub down with the outer bearing facing up. Then remove the outer bearing and spindle washer, and set them aside so you can then pry off the inner seal and remove the inner bearing.

Then, you will want to take the inner and outer bearings out to clean them and remove as much grease as possible. This can be down with rags and washing them with a solvent or degreaser and set them out to dry. Inspect the parts once they are dry to make sure there are no signs of rust, corrosion or other visible damage. Once you have cleaned and dried the parts appropriately, you can apply some fresh bearing grease and pack the bearings with as much grease as they can hold. This can be done by hand or with a bearing packer. Be sure to also grease the spindle. Once the bearings are packed, insert the inner bearing and seal, followed by the outer bearing and seal. Then the washer, castle nut and dust cap or bearing protector can be installed. Put the wheel back on and jack trailer back down once you completed the installation.


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