Brake hubs and grease

[bwoodtx]

Is there any justifiable reason to pack the center cavity full of grease when doing a repack and brake job.

Seems like a waste to me.

[r carl]

Its a waste unless you have a boat trailer with bearing buddies.

[Inland RV Center, In]

Originally Posted by bwoodtx

Is there any justifiable reason to pack the center cavity full of grease when doing a repack and brake job.

Seems like a waste to me.

That's not only a waste, but that would also create a huge problem, by destroying the effect of the brake shoes.

Some grease would slip out and get on the brake shoes. Then, NO BRAKES.

Cleaning the shoes with a grease solvent, is also a waste of time. If that was done, the very first time the lining got hot, more grease would come to the surface, again and again.

Ask those that tried it.

Andy

[bwoodtx]

That's what I thought, but I just wanted confirmation. Thanks.

[ROBERT CROSS]

Disclaimer.....I know nothing.




If the cap has grease in it.....the grease in the bearings has no place to go.

Bob

[dznf0g]

Likewise for the hub. Doesn't have to be completely full, but make a "dam" so grease in bearing has nowhere to go.

[Redleger]

When packing bearings, regardless if you do the hand or press method, at the put a thin layer all the way around the inner and outer circumference. That all you need. Slide the inboard bearing into the hub and replace the seal. Slide the hub onto the spindle and the the outboard bearing, washer, locking nut, snug up and spin the hub by hand. After your satisfied that you have it tight enough install the cotter key and dust cap. Use a rubber mallet to install the dust cap.

Hope this helps

Tony

[dznf0g]

Boy, I guess my automotive school was way wrong...as well as my employer!

[Action]

The purpose of coating the inside of the hub is only to prevent moisture from creating rust on the inside of the hub. Otherwise there is no reason for grease to be inside the hub. Grease was made to be in the bearings. Having more grease in the hub does not make the situation better. It only creates a mess and possibility of retaining heat in the hub.

>>>>>>>>>Action

[ROBERT CROSS]

Originally Posted by dznf0g

Boy, I guess my automotive school was way wrong...as well as my employer!

Mine also.... We must have gone to different 'schools' together with the same instructor.

Bob

[dznf0g]

Originally Posted by ROBERT CROSS

Mine also.... We must have gone to different 'schools' together with the same instructor.

Bob

Funny part is it has been multiple instructors. Guess they all be dumb. Although, to be fair, today's high temp SYNTHETIC bearing grease doesn't thin out and run out of the roller area as badly as petroleum (non-synthetic) grease does.

But, I still maintain, a "dam" of grease around the inside and outside of the cups is cheap insurance. Gosh a tub of grease that lasts several years must cost ...what $6?

[Action]

I am not sure the type of grease matters.

http://www.brakeandfrontend.com/whee...what-when-why/

Heat does matter.

>>>>>>>>>>>Action

[mocus]

You guys have been a wealth of knowledge to us all. One question, if I may.....How often do you grease bearings. Sorry for butt-in.

[dznf0g]

Originally Posted by mocus

You guys have been a wealth of knowledge to us all. One question, if I may.....How often do you grease bearings. Sorry for butt-in.

I don't anymore! AS has Nevr-Lube hubs and disc brakes and I just sold my last vehicle with old fashioned bearings.

But previously, I packed trailer every 10K miles or 2 years, whichever occurs first. Still inspected, cleaned and adjusted brakes annually.

TV, every 15 - 25K miles

[n2916s]

Most of us will pull the hubs annually to inspect the brakes and do a repack then. I just replaced all my brake assemblies and installed new bearings in new hubs so I will inspect next winter but probably not repack unless there is something amiss.

Mike

[Jacob D]

Originally Posted by bwoodtx

Is there any justifiable reason to pack the center cavity full of grease when doing a repack and brake job.

Seems like a waste to me.

Industrial maintenance experience and articles by bearing manufacturers, lube manufacturers etc, have convinced me that a big reason for rolling element bearing failure is over lubrication. As the bearing turns, heat is generated and the grease needs room to expand. Too much grease in a closed environment like a wheel with a cavity between two bearings, which are also between a seal and a cap may generate excessive heat as the grease is "churned" by the moving elements. If it can't expand it may "cook" and harden and/or cause the seal to fail due to pressure build up. Seal failure can save the bearing but a mess ensues. My practice is to clean and repack the bearings every two years, clean and wipe the inside of the hub with grease to prevent corrosion and monitor the temperature of each wheel immediately at each stop. I also raise each side once a year, adjust brakes if needed and check each wheel for in/out slack and any grating noise when rotating the wheel.

[dznf0g]

Originally Posted by Jacob D

Industrial maintenance experience and articles by bearing manufacturers, lube manufacturers etc, have convinced me that a big reason for rolling element bearing failure is over lubrication. As the bearing turns, heat is generated and the grease needs room to expand. Too much grease in a closed environment like a wheel with a cavity between two bearings, which are also between a seal and a cap may generate excessive heat as the grease is "churned" by the moving elements. If it can't expand it may "cook" and harden and/or cause the seal to fail due to pressure build up. Seal failure can save the bearing but a mess ensues. My practice is to clean and repack the bearings every two years, clean and wipe the inside of the hub with grease to prevent corrosion and monitor the temperature of each wheel immediately at each stop. I also raise each side once a year, adjust brakes if needed and check each wheel for in/out slack and any grating noise when rotating the wheel.

Yeah, a few things here:
1) There is still a LOT of airspace in the hub when just a dam is used.
2) We're talking about a relatively low speed application...roughly 550 revs per mile...at 60 mph that's 550 RPM.

A healthy bearing and hub ( and one that is loaded below specs) doesn't get very warm under normal circumstances....unless you ride the brakes. If that's the case, you got bigger problems than how much grease you have in the hub, and any seal failure is due to the loose nut located 2 feet behind the steering wheel.

[Action]

Any grease located outside of the bearing cage will never find it's way into the cage. Grease is designed to stick to metal surfaces. So the grease in the cage stays there and the grease in the hub stays there.

The only time the grease in the cage would come out would be a petroleum based grease that has been in way too long and has lost it's modifiers & stabilizers. The grease then looses viscosity (thickness) and will run out where ever gravity pulls on it. Centrifical force may sling some back, however the point is the grease has been in service too long and should have been replaced.

If you ever get to look internally at a non-failed sealed bearing you may be surprised at how little grease is in there. These bearings are designed so zero foreign material gets inside and the grease inside is a synthetic.

Nearly every serviceable roller bearing failure is due to incorrect servicing because of -
Not a totally clean bearing - introduces debris which will damage bearing and/or seal
Incorrect seal installation causing distortion or damaged seal
Re-using seal causing distortion or damaged seal
Incorrect bearing installation which causes damage to cage
Incorrect pre-load - either too tight or too loose will cause excessive heat
Too much or too little grease - both will cause excessive heat

The last one is owner neglect not servicing bearings based on manufacturers intervals.

It is because of these factors automotive manufactures have gone to sealed wheel bearings in two wheel drive applications for the last 25 to 30 years. It takes a lot of grief off of vehicle ownership and reduces the required maintenance schedules.

This technology exists and can be easily applied to trailers that are not subject to water immersion. However the RV industry has been slow to adopt this and other "higher tech" solutions for running gear.

>>>>>>>>>>>>>>>>>>>Action

[dznf0g]

I agree with Action;

My training was way before synthetics were around.....but some of the old petroleums would thin and run out of the rollers with no abuse and in less than the 15K maintenance interval.

Old habit die hard. Since synthetics, the grease stays put in the dams I build up. No slinging, no "churning" and not even flattening out across the inner hub surface due to small centrifugal forces.

Action is probably right that with synthetic grease the dams aren't necessary...but that's how I was trained....what can I say. But, like i said above, and Action iterates....I don't have to worry about it anymore, as all my "stuff" now has sealed bearing sets.

[Boxite]

Originally Posted by ROBERT CROSS

Mine also.... We must have gone to different 'schools' together with the same instructor.

Bob

+3

Synthetic lubricants are not the "magic" elixirs some folks believe and repeat.
Synthetics were invented due to shortages of the "real thing" and just because the label states "synthetic" does not equate to "better" in all cases.

The usual advantage modern synthetics have are tenacious long-chain molecular structures which do not break down from shear and pressure as quickly as petroleum lubricants. But that does not mean they don't suffer from the same problems of contamination, heat, and mis-assembly.
So if you don't plan to regularly inspect/repack your bearings such as is annually recommended, then synthetic grease is a good thought. However regular mx will be served just fine with ordinary NLG#2 grease.

I believe Bruce was inquiring as regards the large empty space between the inner and outer bearings.... as opposed to some answers regarding the hub CAP... which is a dust-cover for the outer bearing.

The answers which mention light application of thin coating for purposes of rust-prevention are not wrong. That is a valid reason to lightly coat the hub cap...as well as the axle between the two bearings.
However some applications require more than a thin coating on the inner axle spaces, as the grease in the roller-cage-cone will liquefy at running temperatures and circulate among the rollers, and centrifugal force will sling it out of the cup unless cooler/thickened grease retains it within the bearing.

I was a rear-axle technician with Gulf States Toyota in the early '70s and I was taught to fill to 3/4's point the hub over the inner axle area and lightly coat the running-surface of the seal-landing-area of the axle, as well as all the axle and the inner surface of the hub-cap. We were also taught to lightly pre-load all cone bearings such that zero end-play existed. (as opposed to those that teach backing-off the bearing if the cotter does not match the locknut area.) The theory was taught that the cup and hub would expand if excess temps develop which would then adversely affect the rollers which would "chatter", and then air would whip the grease into froth (some call it "churning") which then deprives the rollers of cooling...and the ever-increasing damage occurs to the point of failure.

I've always repacked bearings as I've just described I was taught and I have never had any sort of failure.

But I've certainly repaired a number of bearing failures of others who did not subscribe to that technique.

It is indeed true that this is a subjective matter... OVER packing with grease can escape and ruin brakes... so certainly don't do that. But I add a generous amount of grease to the inner axle area as I've described.

(Think about this: if a generous amount of extra grease in the inner axle area is harmful.... then why don't "bearing buddies" and similar products fail regularly?)