dwbitt

So my new Madone 6.9 (SRAM Red) has 5200 miles on it, Trek shipped it with a DA chain that lasted about 2500 miles (Use a Park CC-2 chain checker) a bit of a surprise since my Ultegra 9 speed chains lasted about 4000mi. Replaced it with a SRAM 1090 hollowpin chain. Must have gotten lax checking wear, after 2600 miles it was at/beyond the 1.0 limit on the tool. I probably rode it for a few hundred miles that way. Put a new SRAM 1090 chain on and found the cassette (11-26) was worn! Only way to stop the chain from skipping under power was a new cassette. Question for the experts here: is this the wear to be expected from SRAM? I spoke to a Tech guy there and he said "you did good to get 5000 miles out it". Afraid i'm spoiled, the 9 speed Ultegra I was riding has a cassette with 18,000 miles on it and it's still in service. My plan is to be more anal about checking chain wear this time, but would like any input on what to expect from the cassette.

Thanks

andr0id

I have heard 1 cassette = 2 chains. I agree with the tech guy. 5000 miles is pretty good and if you got a bit more that speaks well for your diligent attention to chain lubrication.

DaveSSS 

Here's a few facts. A park chain checker does not measure elongation, it measures elongation, plus the wear on two rollers. Some chains will show .25% wear when new, but this is not wear, it's the normal difference in roller diameter and clearance that exists between brands. This false wear should be subtracted from any future reading. Even then, the tool will always gives exaggerated readings. A precision scale is the only practical tool for measuring elongation.

5,000 miles from a very expensive cassette and two chains is not much life at all, but it does depend on the riding conditions. As others have pointed out to me, some people often ride in rain (not me). I ride in dry but dusty conditions. If you want to get more life from your cassette, measure the chains for real elongation and if they have not reached, .5%, I'd keep using them. You could also get a new cassette and use it with a new chain for perhaps 500 miles. The partially worn chain could then be removed and used on the old cassette for the remainder of its life.

Regardless of the conditions, if you want to maximize cog life, I'd use at least three chains in a rotation and never leave one on for more than its half life. If you get that third chain into use with no chain skip, you can continue using the cassette for the entire life of all three chains and never encounter chain skip.

When you're on the last half of all three chains, use a scale, not a Park chain checker to get the true elongation. Place the end of the scale on the edge of a pin. When the pin at the opposite end of the scale exposes nearly half it's diameter, you've reached .5% elongation.

If you use Campy chains and lube them adequately, they will never show this much elongation, but they will wear out, just not as fast. With a Campy chain I have to rely on checks of the roller spacing to know when the chain is shot. Even then, the amount of wear to consider as worn out, is somewhat arbitrary. I toss mine when the roller spacing is .035-.040 inch greater than a new chain. It's takes me up to 6,000 miles to reach that point. The elongation is still a fraction of the "allowable" .5% after 6,000 miles. IMO, the chain was shot due to the roller wear and the side clearance increasing to almost twice that of a new chain.

If you leave a single chain in use on a cassette for 6,000 miles, it is likely to cause chain skip on one or more cogs, but it depends on which cogs are most-used and how well the wear is spread among the cogs. I use the 19-21-23 a lot for climbing and the 19 was the first to go. I found this out by following the mistaken advice from some "experts" who claimed that you'd never get chain skip if the chain was not elongated by .5%. I proved this to be wrong a second time with Ti cogs and a chain with only 4000 miles on it. That chain had almost no measureable elongation, but still wore out the 19-21 cogs. Ti cogs last about half as long as steel, so I've never bought another Ti cog since then.

dwbitt

Thanks for the in depth reply Dave, I think I'll try rotating 3 chains and see if that gives some more life to the cassette. Good point on chain wear, have to work on that too.

Dave