# Thread: how worn is this drivetrain? (pics)

1. ## how worn is this drivetrain? (pics)

About ten years ago, I used to ride religiously. Around 1997 I started slowing down, and pretty soon my bike was hanging up where it still rests today. I had a Mag 20 fork when it was still considered cutting edge, if that tells you anything.

Enough backstory. I picked up a used bike to use for commuting and some relatively light trail riding. Having been out of the cycling game for a while now, I'm a bit rusty on, well, everything. This new-to-me bike is XTR-equipped (shifters, brakes, derailleurs) and is very smooth, but the chain skips on some of the larger rear cogs. Based on these pictures, how worn does everything look? Do I just need to do a little adjustment, or do I need to replace the chain and cassette? Click for full size images.

3. ## Cable adj. might get you a few more miles out of it.

The barrle adj. @ th' h-bars or th' rear derailluer might give you a coupl'a hundred miles out of that drive train... Learnin' how to adj. will save you some \$ too.

4. There is a quick way to determine how much wear your chain has. You need to measure how much your chain has 'stretched'. Actually, your chain doesn't really stretch--the pins and related parts wear down due to friction. Anyway, each set of 2 chain links is 1" (inch). Thus, from the edge of one pin to the edge of the corresponding pin two links down the chain, should measure 1".

You need to measure 1 foot of your chain (you should be able to do this while it is on your bike). Start AT the front edge of a pin and measure TO the front edge of a pin 24 links (i.e., 12") away. If the distance is more than 12", than you chain has wear. The general rule of thumb is:
- Between 0 and 1/16" - OK
- Between 1/16" and 1/8" - replace the chain
- Between 1/8" and 1/4" - replace the chain & cassette
- > 1/4" - replace chain, cassette and likely the rings

I picked up a used bike and first took it by my LBS. I was told that there was some wear and should replace the chain & cassette, but I could wait. I waited 6 mos., and then tried the above measurement. My chain had 'stretched' 1/4". I had planned on replacing the cassette & chain, but ended replacing the rings too (I may have been able to get away with just replacing the granny & middle rings, but I replaced the set as I decided to upgrade my cranks at the same time).

Here is a link to a site that has pictures to illustrate the above:

5. Since my LBS is within walking distance, I rode down there this morning to get a professional opinion. He measured the chain and said that it was pretty new. He said that it was difficult to tell how worn the cassette is just by looking at it, but that it should be good for a little while. He adjusted the rear derailleur hanger, which he said was bent a little bit (probably happened in shipping). Now everything rides smoothly, with the exception of the third largest cog, which still skips around a little under power. Hopefully I can remedy this with a little bit of barrel adjustment.

Thanks for the advice. Time to start riding now.