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N999BT

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Does anyone know how often the wheel bearings should be greased? Is there a regulation that addresses this? Annually, every 100 hours, every 250 landings? I downloaded the maintenance manual from Cleveland but I can't find a reference to the timing.
 
Appendix D

N999BT said:
Does anyone know how often the wheel bearings should be greased? Is there a regulation that addresses this? Annually, every 100 hours, every 250 landings? I downloaded the maintenance manual from Cleveland but I can't find a reference to the timing.
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FAR Part 43 Appendix D (e) 7 states:

(7) Wheels- for cracks, defects, and condition of bearings

So, I suppose that it depends on how you determine the condition of bearings. could be that you take the bearings out, inspect, and repack them, the usual procedure. Or, give the wheel a spin and pronounce them inspected :rolleyes: Seriously, I have always done, and will continue to do, the real inspection but I suspect that annually is bit of overkill in most cases.

John Clark
RV8 N18U "Sunshine"
KSBA
 
At the conditional inspection.

I inspect every year and replace the grease every other year.

If I flew more then maybe it would need it more often.

Kent
 
actually, I'm interested in what people find as experience for usage. Because I fly about 300hrs a year. So a once a year might not be good for me, may need sooner.
 
allbee said:
actually, I'm interested in what people find as experience for usage. Because I fly about 300hrs a year. So a once a year might not be good for me, may need sooner.
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After 2,225 hobbs hours over almost 12 years (1st flight Sept 1997), I only repack my bearings when I change tires. I DO NOT solvent clean them just repack with clean grease. IMHO, the once a year bearing inspection can be done without solvent cleaning. Others will have different opinions. Yes if there is something that I question during the inspection, I will solvent clean them to get a better look. So far, I have only solvent cleaned them once after sitting outside in the rain over a two-week period. They had spots on them and were replaced. I could see the spots without solvent cleaning but solvent cleaned them to get a better look. They looked usable but were not good enough for me. Bearings are cheap compared to the entire airplane.
 
thanks gary. I would think things should go a long time, after all, we should be in the air more than taxi on the ground.
 
Seals

The wheel bearing service issue is all about the sealing (or lack of) in the usual Cleveland wheels. Most cars, with modern seals almost never need, or get, service because the seals effectively keep the grease in, and more importantly, the crud out . So when did you last service the wheel bearings in your car? Anyway, we need to look now and then because of the stone-age felt seals.

John Clark
RV8 N18U "Sunshine"
KSBA
 
Every other year

kentb said:
I inspect every year and replace the grease every other year.
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This is my routine as well. When I do my every-other-year repack I like to clean them with solvent first for a thorough inspection first, just makes me feel better.
 
Wheel Bearings

20 plus years ago I worked in the wheel and tire shop at O'hare for the "then largest airline in the world" Tires were good for about 30 to50 landings and the bearings got cleaned, inspected, repacked with each tire change. I think we tore down and built up about 150 per week.

tidbit...almost every tire in the fleet was a retread. 747 all wheels&tires the same( including nose gear) 737-300 main gear tires wheels same as 757 only 1/2 as many

I clean and inspect and repack every other year or if I change the tires. I fly out of a high hot airport and the little wheels spin up pretty good. If you do alot of T/O and Landings you should adjust your mx schedule.

cm
 
John, years ago I would have agreed with you on how often do you grease your vehicle's wheel bearings. But the newer vehicles now have to replace their bearings fairly often. My van has had all bearings changed about three times so far (2003) , probably next time they go , it will go. My pickup has had the bearing replaced and it had less than 40,000 miles on it at the time. This is the first batch of vehicles I've ever had wheel bearing problems. Either GM or the bearing people are taking short cuts now.
Ron
 
Ball Bearing aren't good for thrust loads

Ron B. said:
John, years ago I would have agreed with you on how often do you grease your vehicle's wheel bearings. But the newer vehicles now have to replace their bearings fairly often. My van has had all bearings changed about three times so far (2003) , probably next time they go , it will go. My pickup has had the bearing replaced and it had less than 40,000 miles on it at the time. This is the first batch of vehicles I've ever had wheel bearing problems. Either GM or the bearing people are taking short cuts now.
Ron
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Most FWD cars now have ball bearing instead of the older style tapered roller bearings. Ball bearings don't take steering/cornering loads as well as tapered roller bearings. Tapered roller bearings on my 1994 Ford Ranger wen't 180,000 miles before being serviced. Ball bearings (lubed for life? - not) went out on my 2001 Impala LS at 72,000. Don't know about your truck. Could have been underdesigned by the "fresh boys" that the bean-counters hired because all the grizzled old experienced engineers were too expensive.

Larry Tompkins
grizzled old automotive engineer/racer/mechanic
 
Miles?

Ron B. said:
John, years ago I would have agreed with you on how often do you grease your vehicle's wheel bearings. But the newer vehicles now have to replace their bearings fairly often. My van has had all bearings changed about three times so far (2003) , probably next time they go , it will go. My pickup has had the bearing replaced and it had less than 40,000 miles on it at the time. This is the first batch of vehicles I've ever had wheel bearing problems. Either GM or the bearing people are taking short cuts now.
Ron
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Yes, GM had an issue with the early "unserviceable" (read: sealed) bearings. But back to my point, a little math. If you flew your RV 100 hours a year and the average flight was 1 hour, and your average taxi distance was two miles, that would be 200 miles of taxiing a year. So, to get to your truck's early failure point of 40,000 miles you would have to fly for 200 years. :rolleyes: I'm kidding, but the numbers are true. And yes, I service my bearings yearly.

John Clark
RV8 N18U "Sunshine"
KSBA
 
Wheel Bearing Inspection Interval

I work for largest aircraft wheel and brake supplier in the world and supply wheels from for the Cessna Mustang up to 747-400ER and A340-600. Tapered roller bearing (sets) for these applications can see 60,000 lbs axial load plus 20,000 lbs side (yaw) load. Timken is pretty much the only game in-town for aircraft quality bearings (of all sizes) and they have it figured out?

As mentioned in a prior post, commercial A/C tires are good from about 150 to 300 landings per tread life. At tire change, bearings are removed, thoroughly cleaned, visually inspected, then re-packed with Aersoshell 5 (rather old grease technology, but just fine for our GA applications), Mobile 22 or 28, or perhaps Mobile SHC-100 (note, there?s a ?aero? and ?non aero? SHC-100 out in the market). Yes, SHC-100 is fantastic grease. It?s claim to fame is overall better corrosion protection for the bearing cup & cone, but it is a pain to clean during inspections.

From my POV, any of these greases will protect the bearings used on our RVs just fine. SHC-100 is perhaps overkill. With regard to serving intervals, I remove, clean, repack, every year. After 5- years & 400 hours, the bearings look like new. Could I go to an every-other year program? Yes, I probably could.

Note, there isn?t anything especially difficult about bearing inspection. Like in most areas, common sense rules. Once you get the cone (the part with the rollers) and cup (the part that stays in the wheel hub) clean, give it a good look with bright light. Replace a cup or cone if you see any discontinuity in the surfaces. However, staining of the metal is not necessarily a cause for rejection if the surface remains smooth. Use a plastic pick or finger nail ? if you feel it, scrap it. Lastly, when you repack (never a clean job), be sure to pack grease in between the rollers so that the cage is filled. This is where the grease needs to be. Once re-installed, wipe most of the visible grease away; it?s not doing any good if it?s not in contact with the rollers.

As a final point of interest about bearing grease, over the years there have been a number of aircraft evacuations resulting from apparent ?brake fires?. More often the not, it turns out too much grease was used to pack the bearings or applied to the axle (to assist wheel installation). Needless to say, the first or second landing after the particular wheel was installed and the brake got hot, the excess grease softened the dropped onto the inner brake structure causing smoke and sometimes flame. Generally, it looks much worse than it is as the flame is short lived and the wheel/ brake assembly is tested to much hotter (rejected take off conditions) during the design & qualification phase. RTO testing is a subject for another post?

Steve Campbell
RV-6
Troy, Ohio
 
wheel bearings

Annual is the typical inspection. Its recommended to check them on 100 hr if you have an airplane on 100 hr schedule as we do. Usually we change tires a couple of times a year and clean,inspect and regrease bearings. The bearings seldom require replacement. 300 hrs a year is not going to require a bearing inspection any more than at annual inspection.
 
What kind of grease?

This has been a very interesting set of posts for me. In the past, I have just gone down to NAPA, bought some wheel bearing grease, and used that. I always thought that there is no way aircraft tapered roller bearings could be any higher stress than a car, especially an RV with a 1500 lb gross weight.

I suppose I should probably buy some "aircraft" wheel bearing grease? How important is it, really?
 
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