Why Sealed Bearings Fail Prematurely

[exotion]

Bearings fail prematurely because of heat, heat is the enemy of all things lube.

Even sealed bearings can be greased, they make needle attachments for grease guns. Granted it will no longer be sealed however I have needed to do this before. Easiest way to check is get a mechanics stethascope with the long needle on the end listen to the bearing as you spin it you shouldn't hear anything except the grease moving around.

Friction causes heat, engines cause heat, and outside air is heat. All things put together and bearings get hot and they are made for it however the constant heat up and cool down takes it toll

 

[Carscw]

I just remove the seal and pack the bearings then put the seal back on.

For spindles with zerks I use bearings with a metal seal to let grease in.

 

[SeniorCitizen]

View attachment 23767View attachment 23768 These spindles are rebuildable with the same bearing used to rebuild trailer axles, very cheap $11.00 per spindle. The races are just taped in like you do front wheel bearing or an older car/truck. They have grease zerks so I can keep the dirt and water out by adding grease about every 50-100 hours. Most of the stuff you get today are throwaway unless you install your own zerks in the aluminum spindle housing. I have never tried to rebuild them because the shaft or housing was damaged and it just isn't worth my time to do it. Cheap junk. I do know that adding a grease zerk makes the cheap made junk not cheap priced spindles last much longer.
The design that Senior Citizen is talking about is a poor design unless you do what he does to fix and overcome it short comings, but most folks don't see the flaws in the design and think thats how long the bearings are supposed to last before repairing or replacing the spindle.

Do you torque the castle nut on the car spindle the same as you would the nut holding the mower blade on?

 

[gfp55]

Do you torque the castle nut on the car spindle the same as you would the nut holding the mower blade on?

No, the shoulder on the shaft of the spindle shaft stops you from over torquing the nut and putting too much pressure on the bearings (the shoulder stops the inner bearing races so when the blade nut is torqued its tight) now if the shoulder on the shaft is worn or damaged and you tighten the blade nut it will bind and put too much pressure on the bearings and will heat up and fail. You can tell because the after you torque the blade nut and try to turn the shaft it will not spin easy and you can feel drag. You know how it feels when you change or repack front wheel bearings on a car, when you tighten the castle nut, you turn the wheel to get the right preload and you either tighten the more or you loosen so it has the correct preload so the bearing don't overheat and fail prematurely. I hope I said this so folks can understand me and I also hope I answered your question SeniorCitizen. If not let me know OK

 

[SeniorCitizen]

So if the shoulder on the shaft acts as a stop for both bearings the mid section's function is the same as the spacer on sealed bearings.

The only difference I can see between the two different set ups is the type of bearings ( sealed or tapered roller ) and the tapered roller bearing system will need several precision machined components opposed to very few with the sealed bearing system. The greater number of precision machined parts of the tapered roller system could very well be the reason for the sealed bearing system.

 

[gfp55]

Yes sir, you could right on.