Chain lifespan

[kgreene10]

I got 11 months and probably 6k of riding out of my first DA chain when I bought my 7800 group last year. I replaced it with another DA chain and only have two months on it with perhaps 1k of riding at best, but the chain tool says it's very close to worn out. What gives?

[mflaherty37]

I dunno. But possibly a worn cassette and/or chainring would stretch the chain faster. Do you chainrings looks repitched or sawtoothed at the 9 and 3 o'clock position vs. the 6 and 12 o'clock positions, (where 6 and 12 o'clock would be where the crank arms are and the pedaling torque is low)?

[Ken Robb]

I dunno. But possibly a worn cassette and/or chainring would stretch the chain faster. Do you chainrings looks repitched or sawtoothed at the 9 and 3 o'clock position vs. the 6 and 12 o'clock positions, (where 6 and 12 o'clock would be where the crank arms are and the pedaling torque is low)?

I never thought of this way of checking teeth but I think it's a dandy technique. Thanks.

[Dave]

A Park Chain tool combines any actual change in length with the wear to the rollers at each end of the tool, so it never truly measures elongation, which is the change in the length of the chain, or change in pitch.

Unlike the chain pitch, which must be very accurate, the diameter of the roller and amount of clearance between the roller ID and the "shaft" that it rolls around (formed into the inner plates) can vary significantly between brands.

A new Campy chain may measure .200 inch between the rollers when new, while a Shimano or KMC may measure .210 inch. This can cause the Park chain tool to show that a new Shimano or KMC chain is elongated by .25%, even when new, but of course that is not true. If you measure the center to center distance between the pins, over a length of 12 inches or more, you would find the length to be perfect. Measuring over 48 inches, you might find it to be slightly shorter than the nominal 48 inches for 96 links.

At the minimum, you have to consider the new reading to be the zero point. If you want to change the chain at .5% elongation then wait until the tool reads at least .75%. Even then, the reading won't be correct, since the wear of the rollers at each end of the tool can be quite large and exaggerates the wear reading. You'll get a more reliable reading with a precision 12" scale. Lay one end on the edge of a pin. If the pin at the other end exposes nearly half the pin diameter, you've reached a true .5% elongation.

In my chain wear tests, I've seen Campy chains elongate about 1/4 as much as a DA chain, but that does not mean they last four times longer. The rollers still wear and the side clearance also becomes greater. Since elongation is so small, I use roller wear to determine chain life and toss a chain when distance between rollers increase to .235-.240. That might be another 30% more mileage than you'd get from a DA chain.

My other comment is if you got 6,000 miles from a DA chain and then installed a second chain on the same cassette and got no chain skip on any of the cogs, then you were very lucky. Leaving a chain mated to a cassette for that long is very risky. I've worn out Ti cogs, using a single chain for only 4,000 miles, but I was using a 28T little ring that produces a lot of chain tension and doing a lot of climbing, so the 19 and 21 tooth Ti cogs saw the greatest use.

[mflaherty37]

distance between rollers increase to .235-.240. That might be another 30% more mileage than you'd get from a DA chain.

Interesting. I don't understand the final distance between rollers though. If the chain starts at 0.2"/link and you want 0.5% elongation then you would get to 0.201"/link, no? Did you mean 0.235-0.240%?

[Dave]

Interesting. I don't understand the final distance between rollers though. If the chain starts at 0.2"/link and you want 0.5% elongation then you would get to 0.201"/link, no? Did you mean 0.235-0.240%?

The roller dimensions have no affect on elongation. Elongation is due to wear between the pins and the bushing formed into the inner sideplate. That wear is extremely small compared to roller wear. .5% wear is .0025 inch for each pin/bushing pair.


Roller wear does not make a chain longer. A really worn roller may have up to 10 times that amount of wear, split between the roller OD, ID and the "shaft" it rolls on. When you measure between rollers, you get all three wear areas times two. A really worn roller might be .005 inch smaller on the OD and .010-.015 inch larger on the ID.

[mflaherty37]

The roller dimensions have no affect on elongation. Elongation is due to wear between the pins and the bushing formed into the inner sideplate. That wear is extremely small compared to roller wear. .5% wear is .0025 inch for each pin/bushing pair.


Roller wear does not make a chain longer. A really worn roller may have up to 10 times that amount of wear, split between the roller OD, ID and the "shaft" it rolls on. When you measure between rollers, you get all three wear areas times two. A really worn roller might be .005 inch smaller on the OD and .010-.015 inch larger on the ID.

OK, I get it now. Thanks

[jasond]

So what is the best way to measure wear? I've measured the chain using a rulers and my chain is spot on after 1500 miles. How might I go about measuring roller wear? Would it be smart to invest in a good measuring tool? The only reason I ask in I was at my LBS and they were trying to tell me I should change my chain after 1500 miles. I have no doubt that chains can and do wear this quickly but I doubt mine has.

J

[Dave]

So what is the best way to measure wear? I've measured the chain using a rulers and my chain is spot on after 1500 miles. How might I go about measuring roller wear? Would it be smart to invest in a good measuring tool? The only reason I ask in I was at my LBS and they were trying to tell me I should change my chain after 1500 miles. I have no doubt that chains can and do wear this quickly but I doubt mine has.

J

I use dial calipers to measure the distance between rollers on a Campy chain, but other brands generally expire due to elongation first. A scale is the best tool for measuring elongation. To really know how much wear has occurred, you need to compare a new chain to the used one.

Shimano or KMC roller spacing is a little greater than Campy, by about .010 inch, when new.

Campy suggests changing a chain when a 5.200 inch length between rollers increases to only 5.220 inch. I might take a chain off at that point and put on another chain in a rotation of three, but I sure won't throw that chain away at that point. If you do, you're tossing about half the chain life.

On the other hand, you shouldn't use only one chain until the roller spacing increases by .035-.040 or you are very likely to get chain skip. It all depends on how well you spread the wear among the cogs.

Unfortunately, there is no single measurement limit that guarantees the maximum life from both the chain and cassette.

I know from experience that my climbing cogs get the hardest use and will expire first. I use a 3-chain rotation, so I never have to worry about chain skip and and pretty much assured the cassette will last for the full life of three chain (12-18,000 miles).

[djg21]

So what is the best way to measure wear? I've measured the chain using a rulers and my chain is spot on after 1500 miles. How might I go about measuring roller wear? Would it be smart to invest in a good measuring tool? The only reason I ask in I was at my LBS and they were trying to tell me I should change my chain after 1500 miles. I have no doubt that chains can and do wear this quickly but I doubt mine has.

J


1,500 miles is safe. If you change wheels, you will be less apt to have problems, and the price of a new chain is substantially less than that of a new cogset.

[jasond]

Thanks guys...that helps. Basically I should be looking at buying a new chain and measuring calipers and putting the old chain aside to put on a rotation. Well bright side is I need to clean the one on the bike anyway so problem solved. I like it when a plan comes together.

J

[dekindy]

If you want to maximize chain and cassette life, isn't the ideal procedure to purchase 2-3 chains and rotate them every 500 miles so that the chains and cassette wear together?

[Peter B]

I keep my chain clean and lubricated w/ Prolink and check wear often with a Park CC-2. I run 39/53 and 12/25 on my geared road bikes and ride lots of hills. I tend to get 1500-2500 miles from a chain, best guess, depending on road conditions. I replace them before they are shot, as chains are cheaper than cassettes. Been there, done that.

People talk about chain 'stretch' but I doubt the side plates elongate due to wear. My observation is that the pins, rollers and bushings wear and that the resulting excess space, or length, if you will, of link sections is what wears out cassette cogs.

[Dave]

Elonagtion is often called stretch, but what causes it is simply the wear between the pins and bushings formed into the inner sideplates. The roller wear does not contribute to elongation. When a chain elongates by 1/16" per foot, it merely means that the average wear on each of the 24 pin and bushing pairs is .0025 inch.

That park tool will report some new chains to be half worn out and later report as much as twice the actual elongation on top of that. You need to subtract the false wear, at the minimum. Better to just use a scale.

As for rotating chains, rotating every 500 miles won't hurt a thing, but it does not need to be done that frequently. The most important thing is to get some use on each of the chains before any cog gets enough wear to cause chain skip. I've rotated campy chains at 2500 miles intervals, placing the third one on at 5,000 miles and got by with it. With the new 11 speed, I'll probably cut that down to somewhere in the 1500-2000 mile range, just to be safe. There is no masterlink that's a real good fit for the 11 speed chain, but there are three that fit OK. I have one chain running a connex 10S1 with no problems so far. At some point, I'll try a SRAM 10 powerloc, Forster superlink model 4 and KMC missing link, in the Campy 10 UN model.

[jasond]

Since I'm going to buy a new chain does anyone have any experience with the new Shimano Dura Ace CN-7900 chain with the quick link?

J

[Dave]

The best bang for the buck is a KMC DX10SC, sold under the Performance Forte name or from Nashbar, but only if you can get them in the $20-25 price range.

Shimano chains wore faster than any other chain I've tested, but I never got around to trying a SRAM chain, since most sellers wanted more than the best wearing Campy 10 chain.