Chainwear indicators/measuring tools

[Danneaux]

so its not necessary to get the rohloff specific chainwear tool?

I would say it is important to have some way of measuring chain stretch over time so the chain can be replaced before it wears and elongates enough to cause damage to chainrings and cogs/sprockets. For many years, I used a ruler with some care and came out fine.

I recently bought a chain checker for convenience (quick checks at home) and to take along on lengthy tours where my ruler method is not so wieldy.

There's many good chain checkers available, and all give some fairly consistent indication of chain wear. However, the method by which they work (and the amount and kind of wear they indicate) can vary, so it is a matter of choosing one you are comfortable with. Some fail to take bushing wear into account, others do. Some indicate an early need for replacement (thus sparing the more expensive parts of your drivetrain), while others allow you to maximize chain life (thus saving on chain replacement).

As mentioned above, a good treatise on the different types and dis/advantages of each can be found here:
http://pardo.net/bike/pic/fail-004/000.html

In my opinion, the Rohloff chainwear tool is a well made, precision instrument that can be regarded as reliable. I simply chose a different model that was better suited to my needs as a high-mileage cyclist, where I would like to maximize chain life without risking the rest of my drivetrain unduly. Because I paid less than half price, it was a good value for me. I will use it on my derailleur as well as Rohloff drivetrains (and will also check using my trusty ruler at larger intervals). As far as chain checkers go, you can choose pretty much any model that appeals, but keep in mind the two different designs give different indications of wear. Unless dropped, damaged, or unusually worn checkers of the same type will give a consistent result, but measurements made with two different types will not give comparable indications.

Best,

Dan.

[ají]

thanks, Dan!

[Javier]

At Ł29.99 the Shimano TL-CN42 Chain Wear Indicator might be an investment for a bicycle workshop that checks in a hurry thousands of chains a year (and by then it could be worn out), but for me it is a waste of my money, when I can use a proper measuring tool, a caliper. I use my trusty Mitutoyo caliper to check the chain wear, nothing more accurate if you know what you are doing. If I had not had one I would buy on ebay a $10 digital steel caliper made in China that are reliable enough for this sort of accuracy, and as a bonus you get a multi-task tool that can be used for a plethora of other measurements, for example, to check how accurate are any chain wear indicator tools in the market. The only use of a chain wear indicator is checking chain wear and taking space in my tool box.
Just my humble opinion.

[ají]

recently bought a chain checker for convenience (quick checks at home) and to take along on lengthy tours where my ruler method is not so wieldy.

How do you check your sprockets, Dan?

[Danneaux]

I use my trusty Mitutoyo caliper to check the chain wear, nothing more accurate if you know what you are doing.

Yep, a precision instrument. I use mine regularly for a variety of tasks. Sure, it will work fine for checking chain elongation if you already have one. I like my Starrett inside, outside, and vernier calipers for some uses, also. They're nice for checking dropout spacing when I build frames.

At Ł29.99 the Shimano TL-CN42 Chain Wear Indicator might be an investment for a bicycle workshop that checks in a hurry thousands of chains a year...

I guess I got a bigger bargain than I thought, as mine was 19€ postpaid, little enough for me to take the risk so I'd have a quick-checker to carry on multi-month tours. I have a weakness for tools and comfort myself with the knowledge this one can be used on all the bikes in my fleet -- and twice on my tandem.

How do you check your sprockets, Dan?

I make a couple checks:

• What I first look for is shiny wear marks and any early signs of "tooth hooking" in the cog/sprocket drive faces when I clean my chain.

• I then use my fingernail(!) as a gauge. If my nail snags at all or slows as it approaches the tooth end when moved from base to peak, it is time to reprofile or replace the cog. The worn tooth will look a bit like this, but less exaggerated: )\

If the tooth profile is sound, my nail will slide right off the tapered peak, which will look like this:  /\

• Since I already have a digital caliper, I also measure between the tooth faces across the wear points to see how much they vary from spacing at the valleys. I used to keep a small section of chain made up from the trimmed ends of too-long chains. I'd wrap it 'round a cog and shine a light behind to see if there was space between the rollers/teeth and where. It was a quick check to see if old chains had worn the cogs at a larger diameter. I stopped using this method because any wear visible this way was already obvious by other means.

I can avoid replacing cogs/sprockets for a long time if I am careful to replace chains before the chains become too worn. Because they are larger and turn 'round less frequently, my chainrings tend to outlast my cogs, even though they are usually made of aluminum instead of steel (I use a stainless steel chainring on my Nomad. The triple crankset on my rough-road randonneur uses middle and inner chainrings made of steel to compensate for their small diameters). I still check them for hooking at every chain cleaning, just as I do my cogs.

On my Nomad, the sprocket and chainring can both be reversed to present fresh tooth drive faces to the chain.  I'm not so lucky on my derailleur bikes, because the cogs and chainrings cannot be reversed for longer life. On those, I use other means to extend drivetrain life...

Most of my randonneur bikes and the tandem are still equipped with 5-, 6-, or 7-sp freewheels, which are fairly thick and have proven long-lived in my use. All my rando bikes are setup with half-step and granny gearing and so my most-used cruising gears run as much in a straight line as possible, with minimal deflection. I use physically large chainrings and cogs in these gears, and that distributes wear over a greater number of teeth...usually a 50/45/24, 48/45/24, or 46/42/24 chainset coupled with 18-24t most-used cogs. My fast, light cadence makes up for the low gearing in these combinations and I typically cruise at 17-21mph/27-34kmh in 58-62 inch gears with a cadence of 110-120rpm. I find this comfortable and it eases the strain on knees damaged in a youthful car crash. I also think spinning (fast, light, round even pedaling) is easier on drivetrains than mashing (low-rev, cyclic pedaling with high periodic torque loads).

At the first sign of hooking on the teeth of my most-used freewheel cogs I pull them, clamp them front-to-front (flat face to flat face) against my new reference cogs, and use a high speed die-grinder to reprofile the worn teeth. This is possible because my freewheel cogs have simple, fairly thick teeth without the kind of contouring or twisting you see on cassette cogs. Occasionally -- depending on how much the cog has worn -- I will reheat the reprofiled cog with my torch and quench it in oil to heat-temper and harden the surface. So long as the tooth profiles can be re-established, the cogs can be reused. Eventually, I replace worn cogs with my spares. Replacing my chains before they stretch too far minimizes wear on the cog/sprocket teeth and extends their useful life. See "Sprocket Replacement and Restoration" here: http://www.sheldonbrown.com/freewheels.html

On my cassette cogs, I simply replace the entire cassette when the teeth on my most-used cogs show wear. Early cassettes were bolted together and individual replacement cogs were available but alas, those days are gone. I used to grind off the rivets of worn cassettes and store the "good" cogs for later in case I needed them...but never did, because those weren't the cogs that wore out first!

Sheldon Brown's site also contains a useful treatise on chain wear written by the late Jobst Brandt: http://www.sheldonbrown.com/brandt/chain-care.html

Best,

Dan.

[ají]

thanks Dan, very informative.