How much distance can I put on drivetrain components?

Question

I figure the jockey wheels on my derailer will last nearly forever, but what about the rest: cassette, chainrings, and chain? How many miles, kilometers, or furlongs do they normally last?

I know that there are definite signs of worn out sprockets—what sort of mileage is typical before the point where the wear is significant enough to require replacement?

This is for a commuter/touring bike with Shimano 105 components that is reasonably well maintained. I clean & lubricate the chain every few weeks.

Answer 1

Mileage will vary greatly depending on the riding conditions and component maintenance. Personally, I've never tracked the mileage of my drivetrain components. But I do know that I replace chains far more often on my commuter bike than on my road bike.

Ok, I pulled out my copy of Zinn and the Art of Road Bike Maintenance...

Chain life: 1,000 - 1,500 miles in dirty conditions or infrequent lubrication. Lighter cyclists riding on clean, dry roads might expect 2,000 - 3,000 miles with poor maintenance and up to 5,000 miles with a daily high-quality lubrication.

Zinn also says that he gets almost infinite life out of his chainrings and cogs! He said that in the section on checking for chain elongation.

Here in Portland, commuting year round, I'm probably near the bottom end for my commuter bike.

wdy

Answer 2

Drivetrain components tend to wear in this order:

1. Chain
2. Rear cassette/sprockets
3. Front chainrings

(and the teeth on your derailleur's jockey wheels may last, but the bearings may not)

The chain is usually the culprit for wearing out the other two. As it wears, the distance between links effectively increases, and the mismatch between the links and teeth will grind away at your gears. So the key to making your cassette and chainrings last is to change the chain before it wears too much. I use a Park Tool chain measuring device -- it slots in between the pins on the chain so it's a bit more accurate than a ruler.

Keeping the chain clean will help increase its life. Also keep in mind that 9- and 10-speed chains (and perhaps 8 as well?) are narrower than the other chains. Their construction allows more gears to fit in the same space, but it also means that they wear much faster.

I've stayed with 9-speed and my chain lasts at least 1500km with a lot of riding in wet weather. Every time I've pushed it (and ignored my chain tool's advice), I've had to spring for a new cassette afterwards. I remember chains on my older bikes (7-speed) lasting much longer than this.

Answer 3

I've heard different rules of thumb (rule of thumbs?) about how much use you can get, and remember none of them. What I do know is that not lubeing a chain often enough--actually, cleaning and lubeing--will cause it to wear such that it 'stretches'. Not stretch like taffy, but gain overall length due to the pins and bushings in the links wearing down, getting slightly more room in how they link together. Once the chain stretches it wears the teeth of the cassette and chainrings much rapidly. Bottom line: lube and clean your chain often enough and everything else will last longer.

Answer 4

As darkcanuck mentions, make sure you check the chain for wear and when it gets outside of acceptable limits change it. If you don't then you'll end up having to change other components too.

I left mine too long (much, much too long) and ended up having to buy a new cassette and chainrings. The rest of the drivetrain may survive for years but only if you look after the chain properly and and replace it when necessary.