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Old 06-15-09, 08:50 AM   #1
merlin55
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Cassette wear, how can it be measured?

I've got some 10 speed Ultegra cassettes, just wonder how I can tell which are the least worn. I almost never ride in the rain, clean and lube the chain often, thus I get about 4000 miles from DA chain (at about 0.5% stretch). How do YOU determine/decide when to replace the Cassette?
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Old 06-15-09, 09:03 AM   #2
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The only practical way is to install a new chain. Eventually, one or more of the cogs will skip under a heavy pedaling load, with the new chain. Those cogs are shot.

You'll get the most life from a cassette by alternating the use of several chains, rather than using one until it reaches .5% elongation, then putting a new one on.
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Old 06-15-09, 09:41 AM   #3
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I've never tried one of these but am curious. Any input Dave?

http://www.biketoolsetc.com/index.cg...&item_id=RO-CK
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Old 06-15-09, 09:41 AM   #4
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You'll get the most life from a cassette by alternating the use of several chains, rather than using one until it reaches .5% elongation, then putting a new one on.
Never heard this before and I'm trying to understand the reasons why this would be true. If you have any further info and/or an authoritative source that I could consult, I would appreciate it.
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Old 06-15-09, 10:08 AM   #5
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I've never tried one of these but am curious. Any input Dave?

http://www.biketoolsetc.com/index.cg...&item_id=RO-CK
I first learned of that from one of the regular posters, but I can't recall who it was.
IIRC, he had high regards for it.
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Old 06-15-09, 10:47 AM   #6
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I first learned of that from one of the regular posters, but I can't recall who it was.
IIRC, he had high regards for it.
It may have been me as I've posted the Rohloff tool before.

Ironically, all it does is what Dave suggested: it is a new section of chain and a lever. Since the chain is never actually ridden it always stays in like-new condition. Using the tool is simply wrapping the chain around the cogs and applying leverage to see if the chain engages the cogs fully. On new or barely worn cassettes the end of the chain won't rise. On slightly worn cassettes the end of the chain may be a bit loose, but on worn cassettes the chain pops off once the leverage is applied...pretty much like it would while riding.

This tool is in no way the only method for measuring cog wear. I can judge cog wear by eye as many of the more experienced mechanics here can, but what I find it most useful for is proving to a customer that a cogset is worn. If I just told them, they might suspect I'm just trying to sell parts, but when I can show them with their own eyes, they know I'm just trying to make their bike ride better. For that reason alone it's worth every penny, and fortunately it's a tool that should last indefinitely.
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Old 06-15-09, 10:56 AM   #7
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I usually get two chains worth of wear out of a cassette. In other words, after two chains, I'm prepared to put on a new cassette with the third chain.
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Old 06-15-09, 11:02 AM   #8
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I looked at Rohloff's doc, and they only talk about Shimano HG and IG.
Does it work with others such as SRAM and/or Campy, etc?
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Old 06-15-09, 11:15 AM   #9
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I looked at Rohloff's doc, and they only talk about Shimano HG and IG.
Does it work with others such as SRAM and/or Campy, etc?
Yes, any cogs made for 1/2" pitch chain.
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Old 06-15-09, 05:24 PM   #10
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I looked at Rohloff's doc, and they only talk about Shimano HG and IG.
Does it work with others such as SRAM and/or Campy, etc?
I would think you could replace the section of chain that comes with the tool with one exactly like the type you use too. My case a 7800.
Don't know if this would make it any more accurate but wouldn't think it would hurt.
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Old 06-15-09, 05:28 PM   #11
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I would think you could replace the section of chain that comes with the tool with one exactly like the type you use too. My case a 7800.
Don't know if this would make it any more accurate but wouldn't think it would hurt.
You realize you need a *new* section of chain, and that looks like a longer section than I ever have leftover, so we are talking about sacrificing a whole new chain in order to get a piece for the tool.
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Old 06-15-09, 05:31 PM   #12
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I would think you could replace the section of chain that comes with the tool with one exactly like the type you use too. My case a 7800.
Don't know if this would make it any more accurate but wouldn't think it would hurt.
You could, but I've found the Rohloff SLT-99 chain it comes with will wrap around any cog I've tried it on.

I'm also pretty sure with some Dremel work and patience, one could make a similar tool, though it might not seem as professional...which is the best use for the tool IMO: Making you look good.
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Old 06-16-09, 07:32 AM   #13
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Never heard this before and I'm trying to understand the reasons why this would be true. If you have any further info and/or an authoritative source that I could consult, I would appreciate it.
I don't know if my posts are sufficiently "authoritative", but I am a mechanical engineer who's been wrenching on bikes for 25 years.

I've read of the Rohloff tool, but never thought it worth trying. I'd rather get on the bike and prove for sure if any of my cogs skip, with the chain that I'm actually using.

The reason that alternating the use of several chains increase cassette life is relatively simple. Chain skip occurs when a new chain with a perfect 1/2 inch pitch is mated to used cogs that have become worn from use with an elongated chain. If you alternate the use of several chains with one cassette, all of the chains gradually wear with the cogs. A brand new chain is never mated with a worn cogs and chain skip will not occur. The key to success is getting the last chain in the group onto the cassette before any cog wears enough to cause chain skip. After that, regular rotation will insures that chain skip won't occur. I rotate each of three chains before any of them are more than half worn. The exact number of chains to use depends on the cost of the chains relative to the cost of the cassette. I also learend that Ti cogs last about half as long as steel cogs, so their cost to own can easily be four times as much.


I have found that it's not just an elongated chain (that has a larger pitch) that creates undesirable cog wear. I've used a single Campy chain on a new cassette for 6,000 miles. That chain only had a fraction of the "allowable" .5% elongation, but it still wore my 19T cog enough that it skipped with a new chain. Despite having a perfectly acceptable pitch, the rollers were quite worn. The original distance between the inside of any two rollers was about .200 inch. After 6,000 miles, that increased into the .235-.240 inch range, so there was a lot of roller wear and very little wear on the pins and bushings (which increases the chain pitch). A detailed check of the rollers revealed that the OD was about .005 inch smaller and the ID had increased in diameter by about .010 inch.

I still use that cassette with the worn 19T cog, but it must be mated to a chain with at least a few hundred miles of wear, so it won't skip. In practice, I use it only on my early-season/dirty-roads bike with chains that are already half worn.

The roller diameter and roller clearances are not the same for all chain brands, despite the fact they all have the same 1/2 inch pitch or center to center spacing. If you measure a Campy 10 chain, it will be have a smaller spacing of about .200 inch when new, while a KMC or Shimano chain will measure about .210 inch. I found that Campy made a small change to the 11 speed chain, with a new roller spacing of about .204 inch, but I haven't compared the roller to see why this changed. The roller OD, ID and the clearance with "shaft" that the roller spins around all affect this dimension.

Last edited by DaveSSS; 06-16-09 at 01:02 PM.
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Old 06-16-09, 07:46 AM   #14
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You realize you need a *new* section of chain, and that looks like a longer section than I ever have leftover, so we are talking about sacrificing a whole new chain in order to get a piece for the tool.
Yes I do. I have longer pieces left over from the timing chain side of my tandem left over than I usually have from my singles drive side. Either way it wouldn't bother me to spend a little for a custom tool.
It's only $30.
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