This year I’m trying something new: I replaced my chain before my cassette became so worn that it also needed to be replaced. In February one of the mechanics at Harris Cyclery recommended that I check my chain more frequently for wear. I had been taking my Long Haul Trucker in once a year for service with about 3000 miles between service. That’s too long for a chain and each time I also needed to replace a worn out cassette.
As a chain wears the rollers get farther apart due to the wear of the pins that keep the rollers in place and provide a small axle for each roller and connecting link of the chain. People refer to this as “chain stretch”, but it is not stretching. The cumulative effect of pin wear is that the chain does get longer, but this is due to the loose fit of the pins at each wear point on the chain. They can wear badly enough to fail, causing the chain to break at one of the links. You never want to let a chain get that bad.
I purchased a Park Tool CC-2 Chain Checker. They are available from Amazon for about $27. The tool features two pins that measure the distance between a set of rollers. The user fits the pins on the tool between two rollers on a taut part of the chain. I usually measure the chain above the chain stay. The next step is to rotate the indicator dial until it stops moving, which means that the pins are as far apart as they can get between the rollers.
The dial has numbers .25, .50, .75, and 1.0 on the dial that measure chain wear. I measure a new chain so that I have a baseline. The numbers on this tool are not a unit of measure or a percentage. Interpreting them is a judgement call and that’s why I recommend measuring a new chain as a baseline. For example, my new chain measures at .25. Above .50 I will replace the chain. I got about 1200 miles from my chain before replacing it. I probably could have gotten another 200 to 300 miles from it. I decided to get it done before a fall tour.
If you ride long and hard with a worn chain, it will wear the teeth on the cassette. This wear effectively increases the space between the teeth and rounds the corners of the teeth. When this happens, the cassette must be replaced together with the chain. If the cassette is not replaced, the new chain will be stressed and will fail sooner because the rollers will not make proper contact with the teeth. This misfit can cause problem shifting as well as vibration and chain jumping.
One key to maximizing the life of a chain is to lubricate it frequently. I lubricate about every 50 to 100 miles. If I ride in the rain or get the chain wet some other way such as washing the bike I will lubricate before my next ride. I use a lubricant made specifically for chains: Finish Line DRY Bike Lubricant. I’ve bee using it for about four years. Do not use WD-40 or household 30W oil. WD-40 is volatile and will evaporate, leaving the chain unprotected. Household oil may be too viscous and fail to wash contaminants out of chain when applied.
Another factor in maximizing chain life is your riding style. I try to favor the largest chain ring because that will tend to favor the larger sprockets of the cassette. This is important because on the larger sprockets more teeth will be in contact with the chain. Chain wear impacts the larger sprockets less and will help extend the life of your cassette. In practice, if you use the largest chain ring, you can achieve a comfortable cadence on a larger cassette sprocket in many circumstances. Of course, on some terrain such as hills this may not be practical all of the time.
This is the first time I’ve had a chain replacement without the cost of a matching cassette replacement. In my opinion it was worth the change at this time because the rear derailleur seems to perform better with crisp shifting up and down the range. It also gives me confidence that my equipment is as mechanically as good as it can be.