[boblaps]

Wheel bearing question: what type of solvent works on wheel bearings to clean out old grease before applying new? Tips on "how to" would be helpful. BL RV-7A

 

[videobobk]

I have always used gasoline. It seems to do the job with little cost/danger and I have watched A&Ps do it for years. Let them soak for a while, then swish them around and rotate them. Rinse-repeat (I read that somewhere.)

Bob Kelly

 

[gasman]

Wheel bearing question: what type of solvent works on wheel bearings to clean out old grease before applying new? Tips on "how to" would be helpful. BL RV-7A

Cleaning solvent works like gas just safer. a gallon of solvent will last for about 10 years of cleaning bearings on your RV. Kept in a small bucket with a secured lid. Clean them in the bucket. The dirt and grease will settle down.

I have also used GUNK engine cleaner. Best to take a paper towel and wipe off as much grease as you can. With GUNK, you rinse with water so you will want to dry with hot air and re-grease right away.

Don,t forget to inspect the bearing and the races. You should find no pits or flaws.............. if so, replace. They are cheap and can be purchased at any bearing house.

The grease that I have used for the past 30 years is from NAPA AUTO PARTS. The brand is STA-LUBE and it is for boat trailers!!!!! Amazing grease. You will understand when you pull the bearings to clean them for the first time. I have never had to replace a bearing....... three aircraft..

 

[RV10Man]

Cleaning solvent works like gas just safer. a gallon of solvent will last for about 10 years of cleaning bearings on your RV. Kept in a small bucket with a secured lid. Clean them in the bucket. The dirt and grease will settle down.

I have also used GUNK engine cleaner. Best to take a paper towel and wipe off as much grease as you can. With GUNK, you rinse with water so you will want to dry with hot air and re-grease right away.

Don,t forget to inspect the bearing and the races. You should find no pits or flaws.............. if so, replace. They are cheap and can be purchased at any bearing house.

The grease that I have used for the past 30 years is from NAPA AUTO PARTS. The brand is STA-LUBE and it is for boat trailers!!!!! Amazing grease. You will understand when you pull the bearings to clean them for the first time. I have never had to replace a bearing....... three aircraft..

Used the same bearings on all three aircraft? Amazing......Just kidding.

Marshall Alexander

 

[Bob Martin]

Solvent

The solvent I use is Mineral Spirits....you can find at most any paint dept, aviation isle.
I really like the idea of using a seal-able can and reuse the solvent!

 

[turbo]

i use a different approach. i wipe them off, inspect, then push new grease thru with a bearing holder that accepts grease thru a grease nipple. wipe off excess and install. latex gloves work best for the hand mess. go fly. still using same bearings after 3,800 hours. brake discs replaced a couple tears ago.

 

[islandmonkey]

---snip--- brake discs replaced a couple tears ago.

Yes, the cost of new discs on my Cub made me cry too.

 

[JonJay]

Yep, just make sure you use the same grease,

i use a different approach. i wipe them off, inspect, then push new grease thru with a bearing holder that accepts grease thru a grease nipple. wipe off excess and install. latex gloves work best for the hand mess. go fly. still using same bearings after 3,800 hours. brake discs replaced a couple tears ago.

...or compatible base....

 

[Rick6a]

There is a school of thought out there that asserts deep cleaning a bearing with a solvent prior to repacking it with new grease is actually worse on the bearing than simply displacing the old grease with new. I am inclined to agree but with only 300 hours of operational service on the original bearings fitted to my -6A, I have no long term experience to back that opinion up with. So I ask this....giving periodic repacking, how long can one reasonably expect a set of bearings to last?

 

[John Clark]

Bearing life

So I ask this....giving periodic repacking, how long can one reasonably expect a set of bearings to last?

With a little maintenance, the life of the airplane. In a previous discussion of wheel bearings I did a little math and found that my airplane averaged something under 150 miles per year rolling on the gear, or about 10% the average distance traveled by an automobile. When was the last time you serviced the wheel bearings on your car? The only difference is the ineffective felt seals on most aircraft wheels that can let moisture in (and a little grease out.) If there is no sign of contamination like water of grit, inspect and repack 'em and go for another year.

John Clark ATP, CFI
FAA FAAST Team Member
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA

 

[gasman]

There is a school of thought out there that asserts deep cleaning a bearing with a solvent prior to repacking it with new grease is actually worse on the bearing than simply displacing the old grease with new. how long can one reasonably expect a set of bearings to last?

Instead of a SCHOOL OF THOUGHT, how about some facts........

My Piper Warrior that I purchased in 1983, was sold last month with the same bearings that it came to me with. During the first annual that I owned it, my mechanic told me to clean the bearings in solvent, blow dry with compressed dry air, inspect all rollers and the two races. Then he said PACK THEM WITH STA-LUBE BOAT TRAILER BEARING GREASE!!!

The plane was always hangared. Never on dirt, Never in the rain. I would service the bearings every two years........ and the grease would look like new. Most of the dirt around the felt seal was brake pad dust. Never found any in the grease.

If you want to kill a set of bearings, let the aircraft just sit.

STA-LUBE is a NAPA part. Test the grease with the grease that you are using. Dab some on the end of your finger, touch to your thumb then pull apart. You can then see why it will stick in place.

p.s. If you don't clean the bearing well, you can't inspect it well. I would like to test a bearing to failure (well almost) by never touching it till I could feel the roughness of the bearing as I pull the RV from the hangar. I would bet it would take years.................

 

[Rick6a]

......how about some facts.....My Piper Warrior that I purchased in 1983, was sold last month with the same bearings that it came to me with.

Well, per your request, here are some facts. I purchased the C-150 in July 1988 and sold it in Dec. 2006. Parked outside (albeit with a roof over its head) and exposed to the elements, unlike your Warrior the 150 often operated off grass, experienced some rain and a lot of dirt. Those things being said, over the years the bearings were occasionally deep cleaned and repacked and sometimes the old grease displaced with new. In the end and consistent with your Warrior experience, the airplane sold with the bearings I bought it with. It did just fine never having seen a drop of STA-LUBE BOAT TRAILER BEARING GREASE.

When I built the -6A, I decided to routinely displace the old grease with new rather than go the deep cleaning route and it is THAT decision I have no long term experience with.

 

[rv8or]

Bearing Packing

Bearings fail in a number of ways: 1. Overload, This will happen if you over tighten the adjustment. (Overheat burn lubricant cage break end of story). 2. Dirt in grease acts like a grinding paste, high wear on cage, rollers and tracks. 3. Fatigue failure. This is the most common, not reaching the design fatigue life. It is this reduced fatigue life that causes most failures. So what causes reduced fatigue life. DAMAGE TO THE ROLLING ELEMENT SURFACES, (i.e. rollers and tracks) creates a high stress point and this dramatically reduces fatigue life.
1 Damage during installation. Unless you know what you are doing hammers and bearings do not mix.
2. Environmental:- MOISTURE
Moisture is the big killer, and this is the main reason you repack bearings.
Have you seen those little black lines on the cup of the bearing at roller spacing, this is moisture created rust lines which are high stress points.
So how does the moisture get in. Purely and simply pumping action. Ride the brakes wheel gets warm air expands exits wheel, wheel cools and it sucks it back in again. Any moisture or water vapour in that air sucked in will be attracted to any cold bare surface. As the wheel heats up it might not be hot enough to vaporise the moisture on the bare surface. Many cycles later and droplets will form run down into the bearing and if parked for a period create those little rust lines. If you don't believe what I say run your hand on the inside of the hub next time you repack your bearings and see if it is wet, you might just be surprised.
A couple of simple precautions can reduce this effect. As mentioned by other people on this thread a good water pump grease helps and the second and most important is to coat the inside of the hub infact everything inside the seals with a very thin layer of grease so that any moisture does not have a surface to adhere to and eventually create droplets.

These are my opinions from a former bearing engineer
Rob

p.s. I know there are many other forms of bearing failures but these are the most likely in this application.
pps. Less standing around helps = More flying.

 

[gasman]

Well, per your request, here are some facts.

Rick, sorry for the misunderstanding, I was not asking for some facts........ I was giving them! sta-lube is a very sticky grease used in small diameter wheels that get spun fast and get sent under water. It is easy to purchase at any Napa autoparts. It was just my choice.

Most bearings in small aircraft are over cleaned, and over inspected. Clean them when you change tires....

Again, this is just MY opinion.

 

[Walt]

i use a different approach. i wipe them off, inspect, then push new grease thru with a bearing holder that accepts grease thru a grease nipple. wipe off excess and install. latex gloves work best for the hand mess. go fly. still using same bearings after 3,800 hours. brake discs replaced a couple tears ago.

I'm with Turbo on this one, unless the bearing is contaminated there's really not much to be gained by performing a "deep cleaning". I wipe off the bearing, clean the races and hub, inspect and re-pack.