So I have a Surley LHT. Original drive train. I used the go/no-go Park Tool chain wear indicator to measure my chain stretch. I'm between the 0.75 and the 1.0. I will replace my chain. Everyone says the casette wears out 2-3 times faster than the chain ring (at least that's what I found at the Bike Forums archive via Google), but when I discern my drive train I notice that my chain ring is at least as worn my casette. No shark teeth, but some of the teeth are chipped (not badly, but enough to remove the precise pyramid shape at the top of the tooth when the chain ring is new), and others look like they're wearing normally, i.e., on their way to shark teethdom. I bought my LHT complete stock, so it's the Sugino XD600 crankarms. It's a daily commuter/everywhere bike, my commute alone being ~14 miles round trip for the first ~1 year, now ~7 miles for another ~0.5 years, San Francisco hills included the entire time. My questions:

1) Why are my chain rings seemingly wearing out at the same rate as the rest of my drive train? Am I being too picky?

2) Do the chain ring teeth mildly chip before they round off into shark teeth, i.e., should I slap a new chain and casette on it and call it a day? Or should I replace the pricey chain rings?

3) I don't use panniers, just a messenger bag; do you think when I balance/slightly push forward at intersections, I'm overloading my the chain ring teeth?

Preemptive thanks to all the gurus out there who know way more than me!

-Johnny

I think you are seeing how the chain ring teeth are shaped and not any kind of real wear... pictures are almost mandatory around here.

I won't use the Park chain checker since it is not accurate... a 12 inch ruler does a much better job and if you are really anal... precision calipers can be used.

Sixty Fiver is probably correct that what you are seeing is the intentional shape of the chainring teeth. Modern chainrings have some "shaped" teeth to improve shifting and they will look different from the rounded pyramide shape of the rest of the teeth even when new.

Unless your chainrings are skipping under load or are shifting poorly, they don't need to be replaced.

The Park chain checker (and all the others too) gives mixed results. Using an accurate ruler to measure the distance between the centers over a 24 pin span is a more accurate method for most chains. If it measures 12-1/16" the chain is marginal and your cassette may work ok with a new chain. If it measures 12-1/8" or more, replace the chain and the cassette.

Unless you have allowed the chain to wear far past the 1/16" mark you don't need to replace the cassette.

Yep use a ruler, my chain wear tool says both my chains are heavily worn to the point of also damaging the cassette. The ruler says no wear at all - I know which one I will believe!

Check out your chain ring teeth exactly 180 degrees from one of the "chipped teeth". My bet is you'll find one exactly like it. If that's the case, you are looking at a "shifting aid" that's deliberately designed into the chainring to make it easier for the chain to move from chainring to chainring.

Chainrings will last a long time before they need replacement. My description of worn chainrings is they look "pointy".

Exactly. My son-in-law did in fact wear out a 52T chainring to the point that it looked exactly like an aluminum circular saw blade. It took over 25,000 miles and he is a very strong rider.

This is not an absolute. If someone only used a few of the cogs on their cassette during that time, especially if they mostly used the small cogs, it's very possible to have a chain that doesn't show much wear but a cassette that slips with a new chain.

joe - I see a lot of this at the shop as there are a lot of folks who ride SS without realizing it... most worn cassettes do not have even wear and it is usually a few cogs that get worn out.

Generally... road cyclists wear out the smaller cogs, commuters wear things out in the middle, and mountain bikers frag the low end.

I have taken to salvaging old cassette cogs to build up a supply of replacements as sometimes I can rehab a cassette by only replacing a few cogs or customize an existing cassette.

I run far more (quality) steel chain rings than aluminium as they wear far longer and if they do take a hit can be straightened whereas a bent Al chain ring is only good for recycling. I have put 10's of thousands of km on chainrigs before they have needed to be replaced and like cogs, smaller chain rings wear out far faster than larger ones since they are subjected to higher loads run at higher rpm.

Update!

The ruler method shows my chain has little to no wear; 24 links for 12" matched up perfectly (as far my eyes could see). I could see this making sense since I clean/lube my chain fairly frequently.

But, I also analyzed my 50T chain ring, and yes, it's wearing down, and yes, some teeth are lightly chipped, and no, they're not shifting aids. The chips are uneven and the top of the tooth looks like it broke off. Further, my mid and small chain rings which I use much less also do not show such signs of wear.

Considering that everyone says chain rings last a long long time, and considering the wear I've seen on my 50T hasn't caused me any noticeable problems, I think I'll just KEEP RIDING! Over time I think I may just have to replace my large chain ring sooner than the others, but a cursory price comparison shows that one 50T chain ring is 35-40% of the entire crankarm set. What's with that?

You can often buy entire cranksets for less than a set of rings which are often really overpriced... mind you... think about what a chain ring has to do and the stresses it has to handle and you will understand why great ones cost serious $$$.

While you may not believe that someone could possibly design a chainring to look like that, what you are seeing is intentional manipulation of the chainring teeth to aid in shifting. If it helps to see it with your own eyes, go to a LBS and check out some of the new bikes. Guaranteed you'll find the same "wear" on those barely used cranks.

For lower end cranks, it's often not worth replacing chainrings because of the price of a single chainring. However, your 50T chainring will likely outlast your love affair with your current bike so you'll never need to feel the pain of replacing it.

All this does make sense. Thanks for the great advice!

And for really low end cranks replacing the chainrings isn't even a possibility since they are riveted together and swaged to the crankarn rather than bolted on.

When I did wear out a modern Shimano chain ring the chain would climb the ring and slip off, endangering 'nads. That was the only way I could tell it was worn out. Visually there were no obvious telltales like shark teeth.

So if it's not doing that, it's not worn out.