I recently discovered water-spot-damage on one of my wheel bearings, specifically on one of the cups. Looking at the IPC, I found the req'd part references Timken PN: 13830.
As I wanted to fly right away, rather than order the bearing, I called the local airport mx shop and asked if they had this part in stock. After some delay, they asked: "Do you mean PN 13836 ? ... We don't show a 13830 to fit any of the Cessna's."
This prompted me to actually remove the "cup" from the wheel rather than rely on the IPC...and sure enough.... the Timken part number etched on the back of the cup was "13836".
"YES", I told her when I called back. "I need the 13836, I'll drive right over to get it."
I decided at the time that my copy of the IPC must have made a typographical or printing error to make that final digit "6"...appear as a "0"....they seem pretty tiny in the illustration, etc etc.
Then it hit me!
Our airplanes left the factory with Goodyear wheels and brakes. Most of the fleet have converted to Cleveland (and a few have converted from the junkyard-inventories to McCauley.) So I began research on these bearings. Here's what I found:
Cleveland does not use the Timken PN for their own Part Numbers, even tho' Timken is their official supplier. When the conversion kits are installed the WHEEL supplied is Cleveland PN 40-97A )(or 40-09701) ...both of which use the same CONE bearing as the previous Goodyear wheel (Timken cone PN 13889).
However there is a minute difference in the CUPs of the two different wheels, and this is NOT EVIDENT because the measurements are so close as to allow both cups to be installed.
BUT.... the Cleveland wheel actually requires a larger Outside-Diameter Cup, which has a thicker wall! The Goodyear wheel req'd cup's OD is 2.5000 while the Cleveland cup OD is 2.5625. Their respective ID's are 2.36 and 2.40. This difference could mean that the 13830 cup installed in the Cleveland wheel will be LOOSE and not properly pre-load, while the 13836 cup installed in a Goodyear wheel might crack the wheel.
See the actual differences in the two illustrations below, obtained directly from Timken.
Bottom Line: Do not use the Cessna IPC to order bearings for your converted airplane. Doh.
(If you have Cleveland wheels, your CUP should be Timken PN 13836. See your Cleveland Wheel conversion documentation which came with your STC to be certain...and Mark your IPC accordingly.)
- GOODYEAR: click to ENLARGE, click AGAIN to ENLARGE FURTHER
- CLEVELAND: click to ENLARGE, click AGAIN to ENLARGE FURTHER
