A chain is the cheapest part of your transmission setup. The more worn the chain, the faster it is likely to wear your expensive chainring and sprocket. This leads to the standard advice, applicable to derailleur bikes, to change the chain before it reaches 0.75% elongation to protect the sprocket and chainring from excessive wear.
However, on a Rohloff-equipped bike (all those without derailleur-type chain tensioning devices, which are the majority) there is the complicating factor that the manufacturer advises that the chain be run slack.
So, in theory, you can run the chain on a Rohloff transmission without reference to the wear, until it lies down and dies, adjusting it when it become grotesquely worn by the eccentric bottom bracket on the Thorn and by sliding slots for the axle carrier on bikes with the factory-designed frame ends; you tell whether the chain is grotesquely worn by it skipping and/or falling off the sprocket or chainring. If you do this, don't be surprised if your sprocket and chainring wear faster than normal. However "faster than normal" is a relative matter as the Rohloff sprocket is very long-lasting indeed, and it is easy to get a long-lasting reversible chainring like the Thorn ali ring or the Surly stainless ring.
You can run a sprocket and chainring until their teeth are hollowed out on one side, then turn them so the straight side of the teeth are presented to the chain, and run them until only little nubby teeth remain. Photographs have been published on the net of amazingly worn gear sets which still worked.
As I say, you can do it, but whether you
should do it is a matter of personal choice.
Instead, I proceed from my opening statement, that chains are cheap in relation to all other components, and that my personal choice is for zero service. I run KMC X8-93 chains on the factory lube inside a Hebie Chainglider chain case and never service the chain. Read that again: I add no lubrication to the chain during its entire life. But my chains now last at least twice as long as less competent chains (Shimano Nexus), lubed with white wax, lasted inside Dutch chain cases on my Shimano hub gear box bikes.
The way it has worked out on my Rohloff bike, I've been running the chains up to about 0.5% elongation, which may sound wasteful, but the upshot is that after 10,000km/6000m there is no visible wear on the sprocket. The chainrings were changed for aesthetic and component-matching reasons, and I routinely fitted a new chain each time I fitted a new chainring, but none of the three chainrings on the bike in that time show any wear at all.
At a guesstimate, the chains I took off could easily have been run up, in my system of hub gearbox/fully enclosed chain/factory lube without anything ever added/steel or stainless chainring, to 1% wear without operating trouble, though, possibly, with accelerated wear in the latter part between 0.75% and 1% wear. That would depend on the beneficial effect of Rohloff's unusually slack chain and absence of jockey wheels, about which we do not know enough to pontificate.
If you're running your chain open, I'd suggest that the maximum wear should be the traditional 0.75%, and that you may wish to consider the longterm cost-saving of changing chains at a lower elongation of say 0.5%, or, even better, getting a Hebie Chainglider and running the chain on the factory lube for its entire life, to achieve over time not only a cost saving but a major time saving in chain cleaning. If you want to know more, there's a couple of articles on chain cases on the forum, and a lot of reported experience with the Hebie Chainglider, and articles on the savings available in running the chain inside a Chainglider on the factory lube.
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I'm not sacrificing a favorite sprocket and chainring combo, which at the cost of an extra chain or two removed a bit early will see me out, to discover whether in the overall scheme of things, looking at the three components of the primary transmission sequence (chainring, chain, sprocket), I could have saved 0.3 pennies per mile. Someone else can take one for the team. If there are no volunteers, Dan will appoint someone to volunteer.
Andre Jute
