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Wheel Bearing Felts

briand

Well Known Member
What are these for? Bearing preload?

Why do they need grease? Heat protection?

Can I coat them with Mobil 28 instead of the SHC 100 that the bearings come packed in?

TIA.
 
I'm going off the top of my head, but I think the instructions (either Van's or Cleveland) say to saturate them with motor oil, not bearing grease. Don't know why if this is true, and not sure what the felt seals are for to begin with (except perhaps to keep the bearing clean). Probably not much help, I know. I'm definitely interested in hearing the answers.
 
The felt is a reusable dust seal. When you go to pack the wheel bearings, clean the felt in solvent or dawn dish soap. Dry between paper towels and a heat gun or hair dryer. Then drop about 10 to 15 drops of oil, thin is good like air tool oil. then remove excess by pressing between paper towel. Good to go.

Oh! by the way, the best grease I have found for the bearings is STA-LUBE BOAT TRAILER WHEEL BEARING GREASE. Found at NAPA AUTO PARTS. The first time you use it you will understand. And when you go to repack them, you will be pleased at how the grease holds up.

And be sure to pack the new bearings before you install them.
 
I pulled the bearings and just packed them better with the grease they came with. It looked like Parker just gobbed a bunch of grease on each bearing and installed it in the hub. I would like to add a little more grease but that can be done easily without splitting the wheels again.

This is from a Parker document:
INSTRUCTIONS: At next tire change or overhaul remove and discard the grease felts. Thoroughly clean wheel assembly and completely remove the contained grease from the bearings, bearing bore and hub per Component Maintenance Manual. Refer to
AWBCMM0001, latest issue, for grease packing instructions. Pack bearings with
Mobile SHC-100. Install new felt grease seals lubricated with Mobile SHC-100.

http://www.parker.com/ag/wbd/cleveland/pdf/Product/PRM78.pdf
 
I had to install the original tires and tubes that came with the finish kit. I packed the bearings prior to installing the tires and tubes. I guess I was just trying to say its not a big deal to grease the bearings again, not that installing the tires and tubes was a big deal either.
 
I pulled the bearings and just packed them better with the grease they came with. It looked like Parker just gobbed a bunch of grease on each bearing and installed it in the hub. I would like to add a little more grease but that can be done easily without splitting the wheels again.

This is from a Parker document:
INSTRUCTIONS: At next tire change or overhaul remove and discard the grease felts. Thoroughly clean wheel assembly and completely remove the contained grease from the bearings, bearing bore and hub per Component Maintenance Manual. Refer to
AWBCMM0001, latest issue, for grease packing instructions. Pack bearings with
Mobile SHC-100. Install new felt grease seals lubricated with Mobile SHC-100.

http://www.parker.com/ag/wbd/cleveland/pdf/Product/PRM78.pdf

A close reading of this and the Parker Technical Manual show the requirement to replace the felt is refering to instances when changing the type of grease to their new recommended grease of Mobile Aviation Grease, SHC 100 to avoid contamination with previouse lubricants. They started shipping wheels in 3/07 with the new grease. They require the grease be changed to the new type at the next required exposure of the bearings. Of course, this is written with an eye to type certified equipment.

Jekyll
 
How much oil on wheel felts???

I serviced my wheel bearings for my first time (150 hrs) on my 7 and had lubricated the felts with Mobil SHC-100 as instructed. We know that grease is simply oil mixed with soap and the surface of the contact was blackened. [corrected 4.6.21 by rocketbob - some are thickened with clay] Some have noted to lube the felt with oil.

After cleaning the felts in mineral spirits via an HF ultrasonic device. I applied some 15-W50 Aeroshell to one and Castrol Syntec 10-W40 to the other. Some have noted the availability of the lip seals an they look attractive, but since the inner seal contact sleeves were spinning I decided not to add friction to that ring and make it slip more.

Not desiring to have the oil sling out inside the wheel pant and brake disc etc and gather all that dust and crud,I pondered much oil it should hold?

A test was undertaken. The slinger below was operated at equivalent of 100 mph (2500ish RPM). Too high for landing but it is an accelerated test. The felts were loaded with 1 cc of oil.

Short version - the oil came out as expected and plotting the weight loss of the oiled felt showed that it was beginning to flatten the curve at 2 min. So, a 5 min test was run for the second seal also loaded with 1 cc. The felts were loaded then heated for a few min to ensure full wicking.

The slinger was made from a short section of 2" PVC coupling, carpet tape, the canopy cut off arbor and (yes) some aviation scrap. Epoxy is recommended for the PVC/AL bond although carpet tape worked for 15 min.

Caution - when slinging - put the device down inside a container, as it slings a fine mist of oil you won't see until it is too late. It will also serve as an explosion barrier. IMG_5705.jpg

I will return after some experience is gained to see how much oil will contaminate the wheel in real life testing. Maybe the rubber seal is the clean way to go as it seals on the OD if nothing else.
 
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Another good grease is Schaeffer 221, moly aluminum waterproof designed for wheel bearings. When you change grease you need to remove all the old stuff because some greases are not compatible.
 
McFarlane has stock for many of the felts and other parts used in the seal assembly of Cleveland wheels. the parts are FAA-PMA Approved. Keep in mind McFarlane also keeps FAA-PMA Approved wheel bearings in stock.

A note on bearings:
The bearings sold by McFarlane are manufactured by Timken. They are a Class 2 aviation grade bearing. although bearings often use the same part number they typically differ in class. In the bearing world, it's all about class. The Class 2 Aviation grade have tighter dimensional tolerances on the individual parts and the quality control that goes into each bearing is more stringent meaning you are going to get a bearing with the best steel, the best heat treatment, the closest machining which means the bearing will last longer and work better than a bearing of the same part number that is a lesser class. Wheel bearings are not "industry standard" parts. The Timken bearings are FAA-PMA Approved.

Often in the homebuilt world, wheel bearings are compared to those commonly available at the automotive parts store. A key difference in the job to be done by an automotive bearing verses an aircraft bearing is that the aircraft bearing will have to go from zero to 70 MPH instantly. This puts a tremendous strain on the the bearing, and the aircraft bearing will have to do it over and over and over again.

Also consider the diameter difference. Paraphrased from McFarlane's web-site: The result of the diameter difference is that at 70mph, a 17-inch aircraft bearing is rotating at 1384 rpm while a 27 inch car tire is rotating at only 871 rpm.
 
I'm setting here looking at a set of Timken bearings I bought for the RV-4 w/Cleveland 5" wheels. They are marked TIMKEN 08125/08231 on the box with a production date that appears to be 11/20/2018. The bearing/race is marked 8125/8321 and USA. Doesn't say anything about class.
 
The "class 2" aviation bearings are made to tighter tolerances. Their suffix is -20629 on the end of the bearing number. That said, I have never had a bearing fail or need to be replaced, including the Cub and she likes unimproved strips, wheat fields, etc. The felt pad to prevent contamination makes more sense to me than the rubber one. I suppose it may seal better but the felt pads have been around for a while.....

I would think all bearings are made to severe tolerances but would love to know the true difference. We are not landing at 180 kt and that is what they seem to stress and what class 2 bearings are designed for. Landing 0-55 or 70 or so yes. Things to ponder.....
 
I'm setting here looking at a set of Timken bearings I bought for the RV-4 w/Cleveland 5" wheels. They are marked TIMKEN 08125/08231 on the box with a production date that appears to be 11/20/2018. The bearing/race is marked 8125/8321 and USA. Doesn't say anything about class.

You may want to look up the codes and bearing identification in the timken application manual. They have tricky indicators for some features, not just numbers.
 
Since I literally just today re-packed my wheel bearings, I felt compelled to share some thoughts. While there are some areas, like engine oils and prop grease where adhering strictly to recommended lubes is the best idea, for the wheel bearings some of this discussion to me is a bit over-thought.

I have about 1800 hours and 21 years on my original set of Timken wheel bearing, on a 1900 lb. Wheeler Express, and re-pack every other annual. Today, the bearings still looked perfect, and rotated quietly. I use high temperature/water resistant non-aviation specific bearing grease, which each packing time comes out looking exactly like it was when put in there the last time (it is green). And I use a bit of it on the felts as well, no pedigree'd stuff needed. Just say'in.

The class and better tolerance consideration for the bearings, that I agree with - those little guys take a substantial load on spin up, and tighter tolerances means less chance of wear.
 
You can avoid all the tiresome wheel bearing rigmarole by having antisplataero install sealed bearings. Did it 4 years ago and never worried about the bearings again. Reduces wheel shimmy too.
 
A note on bearings:
The bearings sold by McFarlane are manufactured by Timken. They are a Class 2 aviation grade bearing. although bearings often use the same part number they typically differ in class. In the bearing world, it's all about class. The Class 2 Aviation grade have tighter dimensional tolerances on the individual parts and the quality control that goes into each bearing is more stringent meaning you are going to get a bearing with the best steel, the best heat treatment, the closest machining which means the bearing will last longer and work better than a bearing of the same part number that is a lesser class. Wheel bearings are not "industry standard" parts. The Timken bearings are FAA-PMA Approved.

From my research, bearing classes come from the post production measurements. All of the classes are built on the same production run, but seperated based upon dimensional tolerences. The higher the class, the tighter the tolerance. Usually what one is after in tighter tolerances, is a lower TIR (total indicated runout). Industrial machines, likes lathes and Mill, are looking for a lower TIR and the bearings are the biggest contributor to TIR. My lathe has Class 3 and my mill Class 2. Better machines use Class 5 or better but tend to be very expensive, as not many coming from the run match the tolerance. There is no difference in the steel and the lower class bearings are not considered inferior quality with weaker steel and poor heat treating. At 40 years old, my mill still holds an .0003 TIR. Sure, I wish is had Class 5 bearings with .0001 TIR, but that doesn't make the Class 2 bearing bad in any way except the TIR tolerance. Clearly that tolerance was not necessary for long service life, only to provide an ability to the operator to more easily meet tolerances on parts made with it.

IMO, It is about matching tolerances to the application. Generally when matching specs to an application, I am looking for an experienced Engineer to set the tolerances for an application. I am sure Cleveland or Matco could provide better guidance on whether Class 2 bearings are required here. In my experience, tappered roller bearings can provide a long life with a great deal of clearance. Many of the old, unsealed tappered roller bearings used in auto applications are installed loose and must run from loose to tight as the heat generated by the brakes is constantly changing the bearing to race clearance. It doesn't make sense to me to have a bearing / race with very tight tolerances installed on an airplane with no pre-load. Once installed, the clearance will be 10 or 20 times greater than the tolerance. If the installation adds clearance, as I think ours does, what is the benefit of the tight tolerances? The bearings installed in the industrial machines mentioned above are all installed with a significant pre-load on the bearings. They can do that, as they don't have brakes generating 100's of degrees of heat into the steel parts. In their case, the bearing will generally not see more than a 50* rise in heat, typically much less.

I do not agree that a higher class bearing will provide better or longer service in applications designed for a lower class bearing. However, just an opinion.

Larry
 
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Switch from Felt to new grease seal

Instead of starting a new thread, I am adding to an already started thread but I may be moving it in a different direction. There is another thread on the subject but I think this was the better one to add more info to.

How many and or who have switch from the felt bearing seals to the new grease seal (or autopart counterpart)?

Does the replacement grease seal get removed, thrown away every time the wheel bearings are removed for inspection / repacking?

Is it possible to reuse the grease seal over and over like the older felt seals?

I like the idea of having a better dust / dirt seal but I am not crazy about thowing it away and buying new ones every time I inspect / relube the wheel bearings.

Do I switch or do I stay with the reusable felt seals that have worked well for me for over two decades?
 
If it ain't broke...

I like the idea of having a better dust / dirt seal but I am not crazy about thowing it away and buying new ones every time I inspect / relube the wheel bearings.

Do I switch or do I stay with the reusable felt seals that have worked well for me for over two decades?
Hey Gary - I think you just answered your own question. If it ain't broke why fix it? Admittedly my -6 has only have half the hours as yours but mine work great so far even with my misuse of grease on the felt since I didn't know about the oil thing. I re-grease every 100 hrs or so (using crummy Aeroshell 5 at that) and I don't notice excessive dirt, and the bearings are holding up great. Bottom line I already have plenty of things to overthink without adding this one :D

Don't get me wrong - this is an interesting thread and I love that people take the time to test and gather all this data. But as far as I can tell it's all about the myriad solutions to a problem that hasn't been identified.
 
How many and or who have switch from the felt bearing seals to the new grease seal (or autopart counterpart)?

Does the replacement grease seal get removed, thrown away every time the wheel bearings are removed for inspection / repacking?

Is it possible to reuse the grease seal over and over like the older felt seals?

I like the idea of having a better dust / dirt seal but I am not crazy about thowing it away and buying new ones every time I inspect / relube the wheel bearings.

Gary,
The short answer is the new grease seals are fully reusable. They do need to be removed to get the bearings out for cleaning/re-packing. Reinstall the bearings and seals, then reinstall the wheels……good to go.
 
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