rpenmanparker 

Thanks to all who provided advice in the thread I started yesterday regarding a new chain that is skipping on an old cassette. I ordered a new cassette, and all should be hunky-dory soon enough. BUT always thinking, perhaps a little too much, I came up with a heretical question.

Consensus here seems to be that if one is diligent about replacing chains on schedule, one's cassette will last for about 2-3 chains before becoming too worn to work properly with a new chain. Renewing the chain increases the life of the cassette. Now in my case cassettes cost very roughly about 2.5X the cost of a chain and last just about that multiple of chains.

SO why not wait to change the chain until it no longer works on the cassette and both are fully worn out, and then always change both at the same time? I had no problems with the chain I just replaced. Shifted fine and was quiet. Why should I have not just kept using it? One thing for sure, with that method one would always get perfect performance from the new chain-new cassette combination. Or in fact now, why should I not just dig around in the recycling bin, get out the old chain, and put it back on. I could keep the new chain for a later time, and I would save the cost of a new cassette, at least for now. I can't say how long the combination would go before both had to be changed due to malfunction, and the actual economic comparison of the two maintenance practices is a bit murky in the absence of hard data. But I surely know that right now the cheapest thing for me to do is put the old chain back on. And as a purely recreational rider, I am not going to lose a race due to my chain-cassette combination malfunctioning. What's the downside?

Comments?

datlas 

Some folks rotate out older chains with older cassettes.

Seems like a hassle to me. And also risks wearing out your crank's chainrings, which are generally much more expensive.

I just replace chain every 3,000 miles or so...and replace cassette when it is worn (skipping) which is about 12,000 miles.

I believe there are plenty of variations and depends on your comfort level and how involved you want to be with your bike.

rpenmanparker 

Ok, your point about the chain rings may be the definitive answer. How could I have overlooked that?

I should mention that so many folks talk about their mileage. I have absolutely no idea. Three bikes changed out indiscriminately, and I keep no records. Mostly I just don't care about accrued mileage, but I this case I guess it would help to know.

RollCNY

Chain failures tend to be when under load, and are often catastrophic. So people change chains well before reaching that.

You yourself commented that most of your cassette wear is in the middle cogs. Even if chain stretch matched those cogs, it would be horribly mismatched in smallest cogs. Since a chain is a series of linear cords, its growth does not create even mismatch in all sizes.

New shiny chains are sexier than new cassettes, and your bike is worth it.

rpenmanparker 

You're right about that. Another good point, though I wonder if old chain, new cog isn't more forgiving than new chain, old cog. I don't seem to have any trouble on any of the cogs with the old chain even the little used ones.

canam73

My two main bikes each get about 2500 a year and I replace the chains each spring with a new one. Usually a KMC sl10 but I'm not that picky, I'll use SRAM too. I just buy them when I see a good deal. Cassettes get changed when they skip but I ride multiple wheels on my bikes and each has it's own cassette so they a last several years.

My method on the chains works well for me because I don't ever remove and clean my chains, I just wipe and lube. But I for about $60 a year (including lube) I get good performance and have not had a chain failure.

rpenmanparker 

You say, "when they skip". You mean upon replacing the chain, right? The don't just start skipping with an old chain installed, do they?

canam73

I have had an older combination start skipping. It was a Sram "Open Glide" cassette and it never shifted great to start with though. It was my first 10 speed cassette, and it always seemed like one of the spacers in the middle was too wide. I took it off and re-ordered the spacers and also made sure all the cogs were flat but never found anything a-miss. At the end of it's first season it didn't like to stay much in any gear so chucked the set and started over.

For a while after that I only used Shimano cassettes and had no problems. But I needed a climbing cassette a couple years ago and I liked the ratios on a Sram PG better than the Shimano equivalent and gave them another try. This one has worked out so far.

99Klein 

As chains wear, so does your entire drivetrain. Replacing chains before they start to wear everything else is much less expensive in the long run. Have you ever broken a chain? That's some bad stuff and the biggest reason I replace mine as recomended. I also use a lot of different cogs so I can go quite a few chains before they start skipping. I also have multiple wheels/cassettes that I run different times of the year or for no reason at all, so I don't have many cassette issues.

Carbonfiberboy 

Cassettes vary in price a good bit. Ebay has them from $25 to $230. With cheap cassettes, the OP's point is well taken.

rpenmanparker 

No argument, but I essentially only use my 39 tooth small front ring, and I can get a replacement FSA ring for $20 or so. My Red cassette costs $140 as a deal on ebay, and then only if I get the older original version. When those are gone, Red cassettes will be an arm and a leg. It sucks to think you are just going to replace the chain and then find the new one skips and you are out big bucks for the cassette. I was riding along fine before I bought the chain checker. LOL

The only other contact points are the derailleur pulley wheels. I don't think they are going to wear to a point of being unusable, but I could be wrong. In thirty years I have never had a chain fail, so I am not too worried about that. I am really tempted to just keep on grinding on an old one as an experiment.

Keep the advice coming. I am learning a lot. Thanks.

canam73

I have had Rival jockey wheels give out at the bearings. Hasn't ever happened with my 7700 DA, and I think the rest of shimano uses bushings. A Rival/Force replacement set is $20-30, don't know about Red.

rpenmanparker 

That's one area I might not be too rigorous about matching groupset identity. After all, what's the big deal?

Carbonfiberboy 

I've been using VO jockey wheels. Sealed bearings, and seem to last very well.

robbyville

Me too thanks!

Robert, don't mean to derail the thread but just a quick question... you mention that everything was fine until you checked the chain length. So do most people really just change out the chain before they find any problem? I have over 3k miles on my current chain, was not even thinking of it since all is shifting perfectly, should I be swapping it out? I'm not a super strong guy and don't have a gage available, is it mileage related or strength? If a chain stretches can't you just remove a link or is it more that the chain wears in such a way that it could mess up the other components?

canam73

When a chain stretches it is the individual plates that start wearing so the pin to pin pitch is off. Removing a link isn't the problem, it is that the chain pitch becomes longer than the cog pitch and the teeth can't mesh tightly into the chain causing the chain to skate over them. You could check a length of your chain with a measuring tool, but personally I just replace them at 2500-3000 miles and move on.

robbyville

Thanks Canam, guess I better order a new one, I had been waiting for shifting problems to occur. I assume the 2500-3000 mile distance to prompt change is the same even of higher end chains (I have DA 9000)?

rpenmanparker 

Yeah, the amount of stretch is really tiny, less than 1%. And it all occurs within each link, so it isn't the kength that is the problem, it is the fit of the individual links on the cog teeth. Of course overall length is used to see the problem, but it isn't really the problem. The two reasons the change the chain out are to protect the other drivetrain parts from being worn by the poorly fitting links and to avoid a catastrophic failure.

RollCNY

I just looked for a resource I found recently, but can't find it. It was a webpage from I believe Rexnord that gave great diagrams on how pitch elongation and tooth wear causes skip on cassettes and chain suck on cranks.

Quick synopsis on the cassette: the chain is pulling the sprocket tooth, so the load is on the back of each tooth, and the chain departs each tooth under load, so wear tends to round the teeth. As the chain elongates, each pitch behind the loaded tooth starts to ride up the front face, and it gets multiplied by each number of pitches. So one pitch back from the loaded tooth rides up one x elongation, two pitches away is 2 x elongation, 3 pitches is 3 x elongation, etc. Eventually, this cause the chain to ride up high enough that it doesn't catch a rounded tooth, and the chain jumps ahead a pitch to catch the next tooth. Hence, "skip".

On the crank: the chain is being pulled by the chainring, so wear is on the front side of each tooth. Wear comes on this face as each tooth engages the bushing / roller, and forms the "shark tooth" of the bushing / roller digging deeper into the tooth form. Now extra elongation pushes the pin forward, which is no issue until the shark tooth gets deep enough that it exceeds the extra clearance provided by the elongation. Typically, a chain elongates faster than a chain ring wears, so a worn out chain doesn't register on the front. But a new chain on a worn chain ring means that the unloaded chain no longers clears the edge of the shark tooth, and won't release from the chain ring. Now you have chain suck, where the chain ring doesn't release the unloaded chain.

This is oversimplification, and I'm sure will cause argument. Sorry I can't find the professional explanation, with colored pictures and everything (8x10 glossies). It was specific to powered roller chain applications, but the failure modes are practically identical to bicycle sprocket wear and failure.

Kai Winters

I didn't replace my chain for roughly 10 years as an experiment...3000 plus miles per year...replaced chain and cassette...Campy Record chain and Chorus cassette for new and old...the chain was still working like new, as was the cassette...I still have them as emergency backups...going to shoot for another 10 years with my current chain/cassette.

djb

as well as the chainrings costing more to replace reason, another thing to think about (and maybe this is the tourer in me) is that if you keep and old chain and cassette going for ages, if you ever had any snafu with your chain on a trip and had to replace it, your new chain would absolutely skip on the old cassette, which could be a problem on a trip depending on what was available cassette wise.

rpenmanparker 

I like what you're saying, but honestly have to admit it is hard to tell if you are pulling our legs. Assuming candor, can you tell us how were the front rings? Did they object when you put on the new chain?

Kai Winters

Chain rings are also just fine. No problems at all with the new chain/cassette. The crankset is Campy Record as are the chainrings...50/39

Not making it up. I've worked in bike shops for 20 years, two shops, and have always built my bikes from the ground up. This particular bike is a '99 Merlin Ti with a mix of Campy Record Carbon, Record and Chorus drive train. The frame was one of the last built by Merlin in MA before they put a lock on the door and headed south. I picked the frame up at the shop and we got a call barely one week later from a friend of the shop's that worked there telling us when he arrived at work the doors were padlocked and security guards were posted refusing workers to enter even to pick up their personal stuff.

I've always replaced my chains generally twice a year, during winter tear down and mid racing season, thus I've never broken a chain nor had a mechanical during a training ride or race...other than a flat now and then. I've always wondered how long a chain would last and decided to give it a shot...why not...what worst could happen?...so I just rode...after 10 years of riding with the same chain/cassette I finally decided to swap them during my winter routine...funny thing is they looked fine and still worked great as usual.

I do take better care of my bike than the average person...this bike doesn't see wet weather and the drive train is thoroughly cleaned and lubed every two weeks or so...I think this is one of the reasons for such a long life...I'm also a spinner and have always been...plus being a smaller person 5'5" and 145lbs I don't put a huge load on the bike...I've not raced this bike either as I "retired" after 20 plus years of racing due to a bad car/bike accident that left me with many broken bones and over a year of healing before riding again...though fully healed and riding 3000 miles per year I don't put the stress on this bike that I put on my previous racing bike...Basso Ti with full Ultegra.

Believe or not...meh...don't care...just telling of my experience

rpenmanparker 

No, don't take me wrong. I certainly believe you. It's just that so often on the 41 one falls for a line of bull. Very interesting account. I am going to give it a try. All I can lose is the small front ring, and like I said, those are cheap for the FSA SL-K Light crank I'm running. Now what do I do with the new Red cassette that is on its way and the two chains I was planning to use on two of my bikes?

robbyville

Ditto! Although I ordered an Ultegra 6800 cassette for the second wheel set so I'm not always pulling the DA one off along with a new chain. Guess I'll install the new stuff and then ride for as long as I can. I'm similar to Kai albeit a little heavier, I can't see myself putting a ton of strain on the bike with the type of riding I do.