Wheel Bearings and IPC Error

[GAHorn]

Wheel Bearings are made up of "cones", which contain the rollers and cage.. The "cone" mates with a "cup", which is usually pressed into the wheel-half and semi-permanently remains there.

While reversing my tires to obtain more even wear, and re-packing my wheel bearings I noticed one of the cups had small "marks" that indicated something very hard had contaminated the bearing and left a series of scratches in the cup. Therefore I decided to replace both that cup as well as it's mated bearing-cone. (They should always be kept as matched pairs once they've been run-together.)

MVC-029S.JPG

MVC-028S.JPG

MVC-027S.JPG

This is how I discovered that the Illustrated Parts Catalog (IPC) has a typographical error. Early IPC's only describe the bearing cups/cones as Cessna Part Numbers, as does the Cleveland catalog which only offer a "Cleveland" part number. But the B-model IPC does indeed offer the genuine Timken bearing part numbers....unfortunately the IPC gets the CUP part number WRONG!

The IPC describes the CUP as Timken PN 13830. But the CORRECT Timken Part Number (for Cleveland conversions) is 13836. *

They describe the cone correctly as PN 13889.*

(And if you obtain these from an aviation supplier you will receive a genuine FAA-PMA part, priced accordingly. Cup is about $25 and Cone is about $40. The same Timken PN's from an auto-supply or bearing supllier is about $11 and $16 respectively. For folks horribly bothered by wheel-beaings without paperwork such as BluEldr,.... the FAA-PMA paperwork can be downloaded from the Timken website for free.)

I use Marine Grade waterproof wheel-bearing grease on my airplane (Cessna Service Manual 100 Series 1962 and prior approves that), but whatever you use be certain to remove all traces of old grease and NEVER mix different types of grease.

* Althought the IPC illustrates an original Goodyear wheel, the Cleveland conversion kit for our 170's convert the airplane to the same wheels/brakes as used on the C-172, which is a Cleveland 40-97A wheel. These use the same wheel bearings as original wheels.

[ronjenx]

Were those the only three marks?
They look more like corrosion pitting where three rollers may have sat against the cup for a long time.

[GAHorn]

There were two others at random locations. There was no sign of rust or corrosion. I believe a metal fragment must have gotten imbedded onto a roller and made the marks because they are exactly spaced the length-of-travel of one roller.
They may have been there for some time, as it's been almost a year since they were last repacked, and there was no sign of any contamination and no roughtness of the bearing at all. No marks on any of the rollers either.

I"m familiar with water-marks. These are not watermarks. They are scratches with actual metal upset.

[ronjenx]

I wasn't thinking they were water marks. They looked like they had depth, with pitting in the bottom.
Hard to tell from a low pixel web photo.

[GAHorn]

No pitting that I can tell (pretty small). They are exactly as if they were made by a very tiny chisel.