For machines that have been essentially unchanged for the past several decades, bicycles suffer from a remarkable amount of planned obsolescence. Today's case in point: the threaded headset.
I've ranted about this in the past, the fact that most of the bikes I see in use on the street have threaded headsets, yet most bike shops don't even keep them in stock. The industry prefers that you buy a complete new bike with a 1 1/8 threadless headset and abandon your aging-but-otherwise-serviceable ride. If your headset has ball bearings and the bearing surfaces aren't damaged, you can renew a tired headset with a fresh set of balls and some grease. If your headset has cartridge bearings, you may not be so lucky, but there's still hope. Here's how I went about it:
My gently-used Breezer Venturi road bike, circa 1995, still had its original 1" threaded carbon fiber fork and Shimano 600 cartridge-bearing headset. I decided to retire the OE fork due to suspicious surface crazing and my general distrust toward carbon of advanced age and unknown provenance. While swapping on a replacement fork, I found the cartridge bearings were lacking a bit in the smooth department. Actually, the top bearing still felt pretty silky, while the bottom cartridge felt downright crusty-- not surprising given the added load and dirt the bottom end of a headset sees on a fender-less bicycle.
A few days of searching showed the bearings to be made of high-grade unobtainium, although there were a few complete new-old stock 600 headsets to be found. While I was chatting with the mechanics at the Bicycle Cellar, one of them suggested that I might be able to pry apart the cartridges and repack them. He was right!
|Top left: complete cartridge. Everywhere else: races and retainer from disassembled cartridge.|
I started by gingerly prying the assembly apart with an old, well-worn putty knife. This revealed within each cartridge 18 balls held in place by nylon retainers.
Removal of the bearings/retainers revealed very slight pitting (shiny spots, really) on the bearing surfaces-- and also cracked the retainers. I mitigated both problems by installing loose bearings without retainers. I learned this cheapskate trick from Sheldon Brown-- the lack of retainers means you can install more ball bearings and that they will no longer line up with the tiny dents in the old bearing cups. It's technically not quite like new, but I couldn't tell the difference once it was back together. Most 1" threaded headsets take 26 5/32" balls per cup. You want a little bit of play between the bearings.
In this case, the bearings were identical top-to-bottom. With both cartridges repacked, I reinstalled them in the opposite locations from whence they came, so the former road-dirt-eating bottom cartridge can enjoy its golden years in the sheltered luxury of the top cup. I figured this overhaul would be a stopgap measure until I found new bearings, but I'm thoroughly happy with the results and don't feel particularly motivated to change them again. For under $6 in grade 25 loose ball bearings, it feels great.