Bearing lubrication: re-packing the hub?

[Hanno Spoelstra]

I am in the process of taking off the rear hubs of my F15A to change the wheel brake cylinders, relubricate the bearings and replace the seal.

According to the MB-F1 maintenance manual the bearing assemblies should be cleaned and repacked with wheel bearing lubricant every 5,000 miles. But under the "Front Wheel Bearing Lubrication" paragraph the manual states: "Do not pack the hub between the inner and outer bearing assemblies with grease as this excessive lubrication would result in the grease working out into the brake drums and onto the linings". Under Rear Wheel Bearing Lubrication no recommendation is made.

There was grease present in the rear hubs, very thick and dark. I thought it was old grease, but a friend of mine said it could have been a grease especially for that purpose.

What would you advise to do? Follow the manual on the front hubs, and repack the rear hubs with regular wheel bearing grease between the bearings?

Thanks!
Hanno

[Alex Blair (RIP)]

Hanno..
This is true..The heat build up will be excessive if you over grease the hubs and then it will come out all over and in extreme cases bulge out the complete seal..
I personally use aircraft wheel bearing grease..pack it once and it is done for life..
You only put on 5000 KM max in a year on a CMP unless it is a daily driver..
I used a Texaco Wheel bearing grease for aircraft but all the company's make it..It is still out in the shed and I can't remember the number but here is a great Shell grease.
You may pay a few extra bucks but you will only pack them once in your lifetime..
Especially good if you are Fording water areas.
Enjoy..

Mobil Aviation Grease SHC 100
Synthetic Aviation Grease
Product Description

Mobil Aviation Grease SHC 100 is a supreme performance synthetic grease which combines the unique features of a polyalphaolefin (PAO) synthetic base fluid with those of a high quality lithium complex soap thickener. The thickener system provides a high dropping point, excellent resistance to water wash, and a tenacious structural stability. The unique physical properties of the synthetic base oil, combined with selected additives, provide outstanding protection against wear, rust, corrosion, and high temperature degradation. The wax-free feature of the synthetic base oil allows for low-temperature mobility/pumpability and low starting and running torque values. Also, the traction property of the synthetic base fluid is considerably lower than mineral, allowing for temperature reductions in the load zone of rolling element bearings. Mobil Aviation Grease SHC 100 is the product of choice for aircraft wheel bearing applications.
Features and Benefits

A key factor in the development of Mobil Aviation Grease SHC 100 was the close contact between ExxonMobil product engineers and key OEMs to ensure that the lubricant would provide exceptional performance in aircraft wheel bearings. This work has helped to confirm the results from ExxonMobil laboratory tests showing the exceptional performance of Mobil Aviation Grease SHC 100 including long grease life, enhanced bearing protection and bearing life in aircraft wheels, and wide temperature range of application.

To combat high thermal exposure of the oil, ExxonMobil product formulators chose proprietary synthetic base oils for Mobil Aviation Grease SHC 100 because of their exceptional thermal/oxidative resistance potential. A state-of-the-art lithium complex thickener technology was developed and used specific additives to enhance performance.

Mobil Aviation Grease SHC 100 offers the following features and benefits:
Features Advantages and Potential Benefits
High viscosity index (VI) base stock with no wax content
Outstanding high temperature and low temperature performance Wide application temperature ranges, with excellent protection at high temperatures and low torque, easy start-up at low temperatures.
Thicker fluid films protecting against wear of equipment parts operating at high temperature
Excellent protection against wear, rust, and corrosion Reduced downtime and maintenance costs because of reduced replacement of equipment parts
Excellent structural stability and oxidation resistance Long intervals between re-lubrication and improved bearing life
Outstanding structural stability in the presence of water Excellent grease retention on parts in hostile wet environments
Low volatility Little loss of lubricating oil


Applications

Mobil Aviation Grease SHC 100 is recommended for aviation applications which need a lubricant that can perform normal functions, yet go far beyond in terms of high and low temperatures and long-life performance. It is a NLGI Grade 2/ISO VG 100 grease having the cold-temperature pumping resistance of most mineral-oil NLGI Grade 0 greases. It provides outstanding protection at operating temperatures from –54 ºC (-65 ºF) to 177 ºC (350 ºF).

Mobil Aviation grease SHC 100 is recommended for high speed, heavy load applications such as wheel bearings, as well as for slower speed, high load applications such as landing gear bearings, slides, and joints.

Mobil Aviation Grease SHC 100 is approved as a wheel bearing grease by all major aircraft wheel manufacturers.
Specifications and Approvals

Mobil Aviation Grease SHC 100 Approved as a wheel bearing grease
ABSC (Meggitt) X
Dunlop (Meggitt) X
Goodrich X
Honeywell (formerly AlliedSignal) X
Messier-Bugatti X

[Phil Waterman]

Hi Hanno & Alex

Good question and point about repacking the front steer drive ball and hub. When I'm working with a clean one for a complete repack I go with the amount listed in the manual or drivers hand book which for C60S - C60L as being 4.5 lbs of wheel bearing grease (listed in capacities section) while in the Handbook it says 2.5 lbs each. So much for clarity.

Now as to over greasing my long term driving experience with my HUP is that the outer grease seal is stronger than the axle side so that if too much grease is pushed in over time it goes in the axle tube and just sits there.

I add 5-10 squirts of wheel bearing grease into the center of the ball each spring. See http://canadianmilitarypattern.com/Tools.html about half way down the page for how. This can be done through the plug hole on the ball. I like this method of put a little new grease in each year because it gets the new grease into the center of the steering balls.

Cheers Phil

[rob love]

Grease does not flow around like oil. You pack the bearings with grease, but in the cavities and on the spindles, you only have to put enough grease to prevent surface rusting from any condensate that might form. In other words, just smear a thin coat on the surfaces. There is no reason to fill the cavities with great globs of grease. While grease will not flow like oil, it will spin centrifugally. As a result, overpacking can result in blown wheel seals, and contamination of the brakes. The heat will not transfer through grease, and it can turn to a liquid.

I have seen some bad results from certain aircraft lubricants. A plane really only does short distances at high speeds, so that is not really relevant to a CMP. My own recommendation is to use a good quality automotive synthetic grease. They are usually very temperature stable (important to those of us on the prairies) and are good from -50° to somewhere in the 200°C range.

In the military, we used to use a GAA (grease automotive artillery) which was very old spec grease. Around 1990 we went to a synthetic mil spec (MIL-PRF-10924) grease which totally changed my mind re military grease. It strongly resists mixture with water (including salt water), does not turn rock hard in the winter, and does not leak all over the place on a hot day.

At the Shilo museum, that is the only grease I am currently using, which is especially important on a vehicle that may not be re-opened for another 20 years. I just recently had to replace some wheel cylinders on a chev 15cwt that I had rebuilt back in 1996. The bearings and seals were still in perfect condition, and I did not even have to touch them other than to re-adjust the rears on re-assembly.