Overhauling A Bicycle Freewheel

Disassembly and service of a bicycle freewheel isn’t terribly hard, though few people seem to recommend it. Still, having done it myself a number of times, and having seen numerous queries about it online, I figured I’d do a quick post on how to overhaul one, should you ever be possessed of an overwhelming desire to do so.

Should you? It’s debatable, honestly. Freewheels aren’t particularly precise devices, and there’s no real “adjustment” to be made or meaningful performance gain to be had. What you can get, however, is a very quiet freewheel, rather than one that clicks and groans and can be heard from a block away. I like a quiet bike, myself, so I think it’s effort well-spent.

What you’ll need:

A freewheel, preferably mounted to a wheel;
A punch;
A hammer;
A pair of tweezers;
Degreaser and rags;
Lubricant;
(optional) around 50 1/8″ ball bearings, should you want to replace yours.

To get to the innards of a freewheel, you have to remove the outer bearing cone; that’s what the punch and hammer are for. It’s reverse-threaded, so you’ll want to turn it clockwise, with the wheel horizontal. Once you’ve got that removed, you’ll be greeted with something that looks like this:

This is a new freewheel; yours will probably be kind of grotty and filthy. Visible are the outer set of bearings, and their cup. Remove the bearings and store in a safe place (or discard, if you’re replacing them). The bearings in a freewheel are “the least important bearings on a bicycle”, but if they’re rusted or pitted or you just feel like replacing them, new ones are around $2. Whoo.

You’ll then want to lift the freewheel shell off of the body; do this over a container or at least a spread-out rag, as the inner bearings are likely to fall out, here. Collect and save them, et cetera. With the shell off, you’ll be greeted by the body, pawls and inner bearing cone visible:

Regardless of the brand, they all look pretty much the same. Here’s the inside of the shell, showing the teeth the pawls engage:

Clean any old lube, crud, dirt, whatever off at this point, check for any obvious problems, and you’re ready to begin lubrication and reassembly. (On a used freewheel, a little bit of wear to the tips of the pawls is normal, as is wear to the inside of the shell, where the pawls engage the teeth. Things to watch out for are broken pawls and rust on the pawl spring/springs.)

Choice of lube is kind of contentious; some people say you should only use oil, the lighter the better. Been there, done that, it makes for a pretty noisy freewheel, and requires regular reapplication, which creates a huge mess. If you are going to go that route, you probably want to use a pretty thick oil. I like grease, specifically NLGI #2 waterproof bearing grease, myself. What you really want to avoid are chain lubes of any sort, especially the ones that are wax or PTFE in a carrier; they’re even less useful in this application than oil, as they displace and stay displaced, so you wind up basically running without lube. (You get three guesses how I found this out…)

Some people have reported problems with the grease in freewheels turning hard or gummy in cold weather; I don’t think this is an issue with a good-quality grease, and may only apply to the el-cheapo stuff a lot of factories use, the thick stuff that looks like peanut butter. The stuff I use – marine bearing grease – is used by a lot of bike mechanics for axles, bottom brackets, and whatnot, and seems unaffected by at least moderately sub-freezing temperatures.

In any event, lube – lightly – the pawls and the teeth on the inside of the shell, and put a thin bead of lube on the inner bearing cone. With that lube in place, add bearings to the inner cone:

Carefully (!) replace the freewheel shell; a gentle counter-clockwise rotation will make the pawls engage the teeth, and it should slip into place. After that, lube the outer bearing cup and replace those bearings, replace the outer cone and tighten it down good (remember, reverse threaded!) and you should be good for somewhere between a couple years and a lifetime of fairly quiet freewheel operation.

Published in: Geekiness, General | on March 11th, 2011| 1 Comment »

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