Technical Is it possible to overgrease a bearing?

Well , my first intention on this post thread was about the bearing it self! I used my experiences that actually were in lawn mower blade spindles, as I used to sell zero turn mowers.
But bearings are bearings.
Then it morphed into trailer spindle adjustment and also into contamination of electric motors and brakes.
These are all factors in “ too much grease?” mind you and good information.
I am hoping that some gurus here might chime in with some facts.....to prove me right or wrong.
This thread was posted for fuel for thought,my bearing problems are in the distant past.
There is a thread on here at this time that was talking about bearings and got me to thinking about bearings this morning. I didn’t want to hijack his thread,so I started this one.









Bones

 

Good process for tapered roller bearings. But, let's not forget ball bearings, angular ball bearings and straight rollers. Each require a different settings and some are much more sensitive to grease type and application.

For instance, older GM angular ball bearings require preload and seem to like fibrous grease rather than 'normal' grease. Regular ball bearings have no adjustment, and should never be installed so that lateral movement of either race is allowed. Those are the ones that I've read can be caused to slide rather than roll with the wrong or too much grease.

 

Bones,,,you are right.
I have seen several new sealed bearings fail because they were dry,,,,almost no grease at all inside.
I always remove at least one seal and check,,,if need be,,I add more.

Many years ago I saw a do***entary where they were having trouble with grease.
But,,it was in a mining company in Siberia,,,the huge trucks would experience bearing failure because the grease would gel up.
It was like 35-50 below zero there,,,,the wheel bearings on those big rear dumps,,,,the grease looked just like jelly out of a jar,,or jello in a bowl,,,,big clumps of it.

Tommy

 

Good call on adjusting Bones. I had a design of light load equip, that could succeed if, we bought $$$ roller brns, And set shaft dia's & preloads to be near spot-on.
In the front spindle wheel brn setting, I've always channel-lock drawn up till no visible lash (squashed the grease-film) then backed off to the closest nut-slot. Never an issue even at 100k on the first Coupe.

 

Depending on the degree of difficulty and application - it probably a good idea to inspect any “ new pre-packed bearing “.

My example of a bearing was to point out that you can cause damage by “ over greasing “ a wheel bearing.

When I do a front brake job on my tow vehicle - I replace the front rotors & bearings & seals along with the pads.

I drive a 96’ F350 CC 2WD 7.3 PSD
so the parts are relatively inexpensive.


Jim

 

I like the thing that fits over the nut and gives you more selections than 60 degrees. That’s the problem I just encountered on my friends trailer the other day when we repacked his bearings. I tighten up the nut with my channel locks and backed it off to my liking.....right in the middle we’re there was no hole! Back it up.... felt too loose for me! Tighten it to the next hole... too much pre load for me! I backed it off, it’s just a trailer. But I don’t like that on a car! I want it perfect! That’s were those little tin things really shine! I think they break it down to 15 to 20 degrees! I can live with that!





Bones

 

I like to snug the nut up with a pair of channel locks then back off until hub spins free. Also I would have wiped some grease on the axle surface. Also if I removed the seal I would replace it with a new one. I like to pack the rollers on the bearing as well.


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Boneyard, yur talkin' about a 'hat'
or perhaps a 'nut' hat! They help.

 

If you want it perfect use a dial indicator and measure end play. Usually around .0015" max.

First try a different nut. If that doesn't help, then simply install a thin shim (washer) or two under the nut as required, there are also "peelable" shims that are made for the purpose. The cotter pin hole will line up for you.

This is one reason why specs are in a torque range, various stackups of shims would be used to allow for a cotter pin hole to line up within the range. Tie rod ends for example. This way everything can line up and the torque spec is still held within range.

If you dig into the tapered wheel bearing manufacturer docs, they mention that typically bearings are usually installed in the field slightly "too loose" in technical terms. This affects how long they will last. But as everyone knows, a little loose is a whole lot better than even a little "too tight". A new bearing set needs a little more juice on the nut than a used bearing set.

 

Well, you might find this hard to believe, but bearing manufacturers say more bearings fail from over greasing than from under greasing. Excessive amount of grease for the bearing will cause increase in temperature, leading to failure. But this is typically the case with industrial applications, fixed equipment, pillow block bearings, electric motor bearings, etc. For automotive applications, such as wheel bearings, you typically pack the bearings completely full on ***embly. I was taught back in the old days to do this by hand, before we had the fancy smancy bearing packers. The old guys preferred to do it by hand, as they learned back in the day. But if you pack the rollers full there is no need to add more to the hub or to the cap, that is a waste and accomplishes nothing, IME.

 

I am doing research on grease for an investigation.
Over greasing may cause a rapid rise in temperature particularly at high speeds because the rolling elements (bearings) have to push the grease out of the way. This leads to churning in the grease(aeration), which produces heat. Same thing as running an engine with too much oil.

 

The increased heat apparently also increases the rate of oxidization of the grease. We had this discussion at work and the research I did agrees with over greasing is a problem


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I never use the EZ lube zerc I think it just disturbs dirty grease and pushes it in and around the bearing

Norb

 

Both the bearing manufacturers docs and the shop manuals specify to fill the wheel hub to a level even with the bearing race, which is quite a lot of grease, though I've never heard it explained why. Grease doesn't really move, so it isn't "extra" for the bearing. They wouldn't specify that though if they didn't think it important. The only reason I could ever figure is it prevents the cavity from holding water after fording a stream or something like that.

 

I pack the bearing and a smear over everything else to prevent any rust and call it good. I’m not sure if the effects of over greasing would affect things in our applications enough to warrant stressing about it but the research is interesting


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I have a large air powered grease gun that uses a 5 gallon bucket of grease. And my 50 t0 70 year old stuff gets a liberal amount of greasing. a old dozer with ****on head fittings on the idlers and track rollers I would take forever to grease them with a hand grease gun. The same for all the sheaves on the cable blade. I installed a set of six lug hubs on a trailer that formerly had house trailer hubs. And the new hubs have a rubber plug and your supposed to fill them with gear lube. I packed the bearings and after installation filled them with 90 weight. Been together 5 years no problems. Ive seen failures from not enuf lube. Never seen any caused by too much.

 

Seen a car once that had zerk fittings on the dust caps.... What's up with that????.....

 

I pack and install tapered wheel bearings exactly like the Timken video that HRP posted. Knock on wood, I’ve never experienced a wheel bearing failure. I’ve also done thousands of oil bath wheel ends on semi trucks and trailers without a single failure. The .001-.005 end play is critical for longevity, it allows room for lubricant between the race and bearing at operating temperature.

 

worked at a company that used many large bearings-the bearing temp was checked a couple times a day in all the machines-a rise in temp usually meant tear down and replace-bearings were never re-used despite many of them costing in excess of $1000 each-several of the larger bearing were sent out to be rebuilt as a previous poster said-and yes over-greasing causes a rise in temp an can cause a failure

 

Timken docs mention that too much grease can cause "churning" and high temperatures as mentioned, but it isn't mentioned in the standard automotive wheel bearing applications. Cleaning, inspecting & re-packing tapered wheel bearings is probably one of the first tasks most mechanics are taught to do. Every wheel bearing I've ever seen on removal and excess grease is extruded out of the bearing. Maybe what they are talking about is sealed units, if it doesn't have any place else to go that would cause problems.

 

Here’s some really stupid stuff.
This spindle type arrangement is fairly common in many different applications. This particular one is from a mower deck but it’s no different than you’d find on many shafts.

There’s a zerk for grease,, but both bearings are sealed on both sides. You can fill that cavity with grease and pack it clear full up against the shaft and internal side of the seals and not get one lick of grease into the bearings.


Depending on how much pressure you pack grease into that cavity,, you can push the seals into the bearings to get chewed up. Then the bearings run in chewed up seal debris,,, that will wipe out the bearings. Was it TOO MUCH GREASE that caused the failure? No it’s the internal seal and a dumb *** design thought up by an over paid engineer and ***embled by non thinkers. Then the grease pressure is also tight on the shaft trying to spin in there. It’s kind of like a brake on the shaft.

So that question of can there be too much grease in a bearing ? Not exactly.
But if there’s a goofy design and improper use of seals and other things you’re unaware of then too much grease can cause you problems.

 

31Vicky, that is exactly the application that got me into this discussion. Our spindles also had a relief so that excess pressure would not blow the seals. When I would rebuild these types of spindles, I would remove the inter seals on both bearings, the pack each bearing and fill the center with a grease gun. Not all of our spindles had grease fittings, so those got the inter seals removed carefully and the bearing packed with a good grease. Then the seals were replaced and marked so that I could position the removed/replaced seals towards the inside of the spindle. Rarely, if ever, did the spindles I reworked ever fail. But I had a lot of the OEM spindles fail. ( dealing with thousands of spindles ) Just my experiences.






Bones

 

I have some farm tractors with grease fittings on the dust caps. and some have grease fittings in the hub. I try to not over grease them and blow out the seals.

 

There's something to be said for HOW a bearing will be used. An industrial bearing in a stationary setting may see more continuous, high-speed stresses but a wheel bearing on a boat trailer that occasionally is submerged in brackish water at the boat ramp is exposed to a whole different set of issues. One bearing's "Too Much" grease might be another bearing's "Just Right".

 

On equipment like you described, the typical process is to pump enough grease to purge out enough of the old grease so that the bearing surface receives fresh new grease. Those applications are not spinning like a pillow block bearing on a conveyor, etc.

 

Ok I thought I would mention on the straight axle front ends. there is a thrust bearing at the bottom between the spindle and axle. When greasing you need to jack up the axle to take the pressure off that bearing before you grease it. One old boy back in the days of the once a week saturday nite bath! This rough old guy who smelled like a billy goat ran a old cat cable dozer. he really slathered the shiv pulleys with grease. Got so much grease on the cable as it ran over the top shiv on the old 29 cable unit it slung off and coated the back of his head and neck with grease. most times when he returned to work the next day it was still there.!

 

The rear in my 37 is from a 49 Olds. I burned out 3 axle bearings which are the ball type. . They are sealed bearings . on inspection they were dry . Found out that when filling Olds. rear with gear oil level should be 1/2 inch below fill hole . when filled to hole the excess oil would travel out to axle bearings and flush out the grease , thus bearing out the bearing . Burned one out near Bardsville Kentucky , limped into town at 5 mph . Got to a repair shop , they said nobody has axle bearings for a 49 Olds. So my friend drove me to a old parts house in town ,the parts guy looked in his crossover book and said it's the same as late model Ford Torino rear and he said I have eleven in stock at $17.00 a piece so I bought 3 and they were all made in USA. At home bearings were $32.00 a piece !

 

Come clean, Hank..... what were you doing in Bardsville, Kentucky?????





Bones

 

I just completed doing my 42 inch deck on a Craftsman ride on mower. The spindles I took off, had sealed bearings, no zerk, and were in excellent condition after 5 years of use. They looked a little dry, and if I was going to re use the spindle, I would have added grease.
The new spindles have the cover removed on the insides of the bearings, and have a zerk fitting. I did add grease, knowing that if there is too much, there is a place for the grease to move to if it gets pushed out of the bearing.
I agree you can have too much grease, but I don't believe too much grease will cause the bearing to fail. The excess grease will just add heat and drag to the bearings.
Bob