|Measuring Chain Wear||PdxMark|
Oct 2, 2002 11:32 AM
|Sheldon Brown explains chain wear or "stretch" very well:
Cyclists often speak of chain "stretch", as if the side plates of an old chain were pulled out of shape by the repeated stresses of pedaling. This is not actually how chains elongate. The major cause of chain "stretch" is wearing away of the metal where the rivet rotates inside of the bushing (or the "bushing" part of the inside plate) as the chain links flex and straighten as the chain goes onto and off of the sprockets.
And then explains how to measure it:
The standard way to measure chain wear is with a ruler or steel tape measure. This can be done without removing the chain from the bicycle. The normal technique is to measure a one-foot length, placing an inch mark of the ruler exactly in the middle of one rivet, then looking at the corresponding rivet 12 complete links away.
Here is the issue:
Sheldon points out that alot of wear occurs between the roller and bushing, not a stretching of the link. However, his mesurement wouldn't seem capable of detecting wear between the roller and bushing. The rivet-to-rivet distance measured by a ruler won't tell you about gaps between rollers & bushings. According to Sheldon, it seems that there will be more slop between rollers and bushings than stretching of or between links.
In contrast, the Park Chain Checker puts pins between different rollers in the chain to measure the "stretch" between them, which includes gaps between rollers & bushings (2 of them anyway) plus stretch between rivets.
Here is the question:
Can a ruler actually measure the roller/bushing wear that Sheldon identifies being the most significant type of chain stretch? If so, how can a ruler on the rivets measure that wear? Or, for the daring, is Sheldon wrong about chain stretch?
|maybe misunderstanding Sheldon?||DougSloan|
Oct 2, 2002 12:03 PM
|From what I can tell, what he describes would result in the chain stretching. I have clearly seen chains stretch, too; a Wipperman stainless chain I had earlier this year stretched over half an inch over its length, and was shifting like total crap.
In this photo, you should be able to tell that the dent in the rivet would cause the inside plate to be further away from the next one to the left, which would elongate the chain:
|OK, I was thinking the rivet divot would hit the roller nm||PdxMark|
Oct 2, 2002 12:33 PM
|Does it matter?||Spoke Wrench|
Oct 2, 2002 12:15 PM
|The traditional standard for chain replacement has been when two rivets measure 12 1/8" apart. I assume that replacement point has been chosen because experience has shown that it produces economical results. In this case, I define economical results as not replacing your chain excessively but also not allowing excessive wear to occur on the cassette. When you have a system that predicts this point reliably, it would seem to be foolish to be hasty in discarding it.
Even granting that this method of measurement overlooks some of the wear characteristics, that doesn't change it's history of good results.
I have sometimes referred to the Park Chain Checker as the "Chain Seller." The ones that I have used have tended to indicate that a chain was ready for replacement quite a bit sooner than other methods of estimating chain wear. I have less confidence in this tool than I do in measuring 12" of chain.
|Probably not, just trying to understand and to avoid...||PdxMark|
Oct 2, 2002 12:37 PM
|replacing a cassette almost everytime I replace a chain... or I should say, when the LBS does it. I do almost none of my own bike maintenance, other than cleaning & lubing chains. So I decided to keep better track of chain wear and wanted to understand it.
As an aside, it seems that my 10sp Campy cassette/chain seems to hold up better than my older Shimano ultegra stuff, but the sampling size is too small to be sure.
|You're all misunderstanding...||C-40|
Oct 2, 2002 2:10 PM
|As a mechanical engineer who specializes in manufacturing, I'd wager that a chain seldom "stretches", if it's defined as the side plates acutally becoming permanently longer (plastic deformation).
Chain "stretch" is nothing but normal abrasive wear on the pins and rollers. As the pins and bushing wear, the chain actually becomes longer, but nothing stretches.
It only takes a little over .005 inch wear per pin and roller to add up to 1/8" stretch in 12 inches of chain, or 1/2" over it's entire length. For reference, a human hair measures about .003 inch.
When using a scale to check chain wear, it's easier to measure from the left edge to right edge, rather than center to center (it's the same distance). If the chain exhibits any significant wear, the pin edge that should be entirely covered by the end of the scale will "peek out" beyond the end. Pitch the chain when the wear approaches 1/2 the pin diameter. The chain can be checked on the bike, while it's under tension. If it's off the bike, it must be pulled tightly to get an accurate measurment. A 12 inch machinist's scale works great for measuring chain wear.
Campy recommends that chains be changed when the chain measure 12-1/16" stretch between 24 pins. I've measured as little at 1/16" stretch over 48 inches of chain, after 3500 miles of use. Just because the chain is not stretched to the limit, doesn't guarantee that it will perform well. Bike chains suffer from side wear too. Side wear can cause excessive sideways flex and poor shifting. I prefer to change the chain at 4000 miles or annually to insure optimum shifting performance and reduce tha chances of an unexpected failure. $30 per year is pretty cheap, compared to the cost of most tires.
As for changing cassettes, it makes no sense to change a cassette until the chain starts to skip on one of the cogs. Most often this will occur immediately after installing a new chain. If it does, the skipping cog(s) are shot. Only the worn cogs could be changed, but this approach may not be a lot cheaper than changing the entire casssette.
|Thanks... more comments & questions...||PdxMark|
Oct 2, 2002 3:16 PM
|Also from Doug's comment & Sheldon's photo it seems that pin/rivet/bushing (maybe inner plate?) abrasion accounts for most "stretch." It seems that abrasion on the rollers would not affect stretch as measured because the rollers are floating on the pins/bushings and wouldn't show any stretch in a rivet-to-rivet measurement.... right?
Does a cassette wear out if chains are replaced on time? How many well-maintained chains can folks usually run on a cassette?
The 1/16" wear limit from Campy matches Sheldon B's advice & Park Tools advice, but Spoke W (a very knowledgable guy) says 1/8". Do other folks use 1/8" or 1/16"?
|Doh - ok... 1/8 over 12 is 1/16 over 6.... ok - got that one...||PdxMark|
Oct 2, 2002 3:50 PM
|1/16 vs. 1/8||Kerry Irons|
Oct 2, 2002 5:29 PM
|The old rule was 1/8" per 24 links (12" orignal length) and that worked quite well for 5/6/7 speeds. In my experience, that also required replacing cogs, but I ride on the flats a lot and so only 3 cogs get all the use. With a 9 or 10 system, the recommendation is 1/16", and I find shifting deteriorates after that point. I find the need to replace cogs even at the 1/16" elongation point.|
Oct 3, 2002 8:28 AM
|As long as you understnd that abrasive wear makes the chain longer, that's a sufficient explanation.
Yes, a cassette will wear out, even if the chain is changed frequently. Frequent changing will help lengthen the cassette life, but if you change too frequently, the cost of the chains will exceed the cost of a new cassette. I would expect to get at at least 10-12,000 miles from a cassette or at least 3-4 chains.
Personally, I would never allow a chain to stretch even 1/16" per foot. In my experience, the side wear makes for crappy shifting before this point, and it would take about 8000 miles, maybe more, for my chains to stretch this much.
|re: Campy 10 chain||tarwheel|
Oct 3, 2002 7:01 AM
|If you are using C-10, learn how to replace chains and cassettes because the maintenance costs will eat you alive. It's expensive even if you do it yourself. I have found that the C-10 chain wears a long time, but it can also wear out your cassette if you keep it on too long. It also seems to wear out more in side-to-side movement rather than from stretch. |
My original C-10 chain lasted 5100 miles before the Permalink broke. Before then, starting around 3500 miles, I had brought it into my bike shop several times to have it checked for wear because it was starting to shift a little sloppy. Every time they checked, my LBS said it was fine. When it broke, I was alone on a ride 5 miles from home -- and it was only 3 days after my LBS had checked it last.. After this experience, I decided to replace the chain myself and ordered a Wipperman nickle chain. Like Doug, I experienced very poor wear from the Wipperman chain -- it stretched more in 1500 miles than the Campy did in 5000 miles. Foolishly, I had bought two Wipperman chains at the same time, and my second one wore out in less than 1000 miles. The Wipperman chains also wore out my new Campy cassette I installed with the first chain, after only 2500 miles of wear. An expensive lesson.
So, I am back to using the C-10 chain and my bike shifts great again after suffering through sloppy Wipperman shifting for 3 months. I am, however, using the Wipperman/Connex superlink, which is a huge advantage over the stupid Campy permalink or whatever they call its replacement. The Wipperman link seems to hold up well, is very easy to install, and relatively inexpensive ($5). It's well worth the hassle and expense of buying a Campy chain tool and using their cumbersome link.
|re: Campy 10 chain wear!||Bikez|
Oct 3, 2002 9:15 AM
|I just replaced my C10 chain after 3700K, and my Rohloff chain wear ndicator was showing abit more than 50% wear(I place the rohloff on the chain, and if the "hook" portion goes halfway into the chain, time for a new chain!)
The new chain shifts very well on the cassette, and this method will let me keep my existing cassette/chain rings for quite awhile longer!
I also have been using the Wipperman Connex link, in lieu of the Campy permalink, or now the new pin that campy has come out with. The durability is excellent, and it allows easy chain removal for cleaning!