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Steel vs Aluminum Chainrings and chain wear with a rohloff.

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Steel vs Aluminum Chainrings and chain wear with a rohloff.

Old 07-20-09, 11:31 PM
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waxy
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Steel vs Aluminum Chainrings and chain wear with a rohloff.

One of the things I love the most about cycing is touring. With my love of touring comes lots of miles and lots of drivetrain wear. I'm currently building up a rohloff equipped 26" tourer so that I can get off roads and away from all the bloody cars. My question is should I use a steel chainring or an aluminum chainring with a rohloff?

All of my previous experience touring on conventional 3x7 and 3x9 drivetrains has taught me that steel chainrings make my chains and cassettes last longer. I ride my drivetrains well beyond the recommended mileage before replacing the wearable parts. What I've found when replacing chains and cassettes is that aluminum chainrings wear much faster then steel ones to the point that a new chain on a used Al ring won't mesh up well because of excessive tooth wear whereas a steel ring will still be in a good shape. Also with steel rings chain stretch is greatly reduced.

All of this leads me to believe that a steel chainring coupled with a the steel cog on the rohloff will make the chain, cog and ring last longer. However, strait unramped steel chainring are far and few between. Surly's rings are the only ones I've found thus far. There are plenty of Al rings out there some of which are nice and thick which I think is a good things since I'll be able to flip the chainring and cog once the teeth are worn in one direction.

So which is the right way to go? Steel or Aluminum? Bear in mind that the chainline will always be strait and the chain will never have to do any shifting. If anyone has any opinions of Surly chainrings or knows of any other unramped steel chainrings out there please let me know. Thanks!
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Old 07-20-09, 11:37 PM
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I guess it depends on the price If the aluminum chainring costs 3X less, but lasts 1/2 as long, it's probably worth it... as long as you don't mind spending a few minutes to change the ring when it wears out.
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Old 07-21-09, 01:35 AM
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If extreme durability is what you're after you might also want to consider using even numbers of teeth on both sprocket and chainwheel. If you also keep track of which teeth on both sprocket and ring that ends up between outer or inner plate(one tooth on each end is enough) you can keep the whole drivetrain going in synch, which is supposed to give you a bit of extra wear out of your parts before replacement will be required.
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Old 07-21-09, 07:51 AM
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Originally Posted by moxfyre View Post
I guess it depends on the price If the aluminum chainring costs 3X less, but lasts 1/2 as long, it's probably worth it... as long as you don't mind spending a few minutes to change the ring when it wears out.
Price isn't really an issue. Surly rings are a few bucks more then Blackspire DH rings for instance, however blackspire rings are much thicker. I guess part of my question comes down to whether thicker singlespeed and DH specific rings will last longer then all the narrower ramped AL rings I've use on conventional drivetrains.
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Old 07-21-09, 07:55 AM
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Originally Posted by dabac View Post
If extreme durability is what you're after you might also want to consider using even numbers of teeth on both sprocket and chainwheel. If you also keep track of which teeth on both sprocket and ring that ends up between outer or inner plate(one tooth on each end is enough) you can keep the whole drivetrain going in synch, which is supposed to give you a bit of extra wear out of your parts before replacement will be required.
I'm afraid I don't quite follow how even tooth numbering helps. Can you explain in more detail how this helps reduce wear. If it helps, the ratios I'll be using are 46x16 when not on tour and 38x16 on tour.
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Old 07-21-09, 11:11 AM
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Originally Posted by waxy View Post
I'm afraid I don't quite follow how even tooth numbering helps. Can you explain in more detail how this helps reduce wear. If it helps, the ratios I'll be using are 46x16 when not on tour and 38x16 on tour.
I read another theory somewhere that using cogs and chainrings with a prime number of teeth on each end would ensure longer life. I think it's just that, a theory.
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Old 07-21-09, 12:18 PM
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Originally Posted by waxy View Post
I'm afraid I don't quite follow how even tooth numbering helps. Can you explain in more detail how this helps reduce wear.
Get it from the source, little point in me rewriting what he's done so well. Comes with pictures too!
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Old 07-21-09, 01:01 PM
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Thanks dabac. I found that article after I responded to your post. The theory seems to make sense in my brain so I think I'll try the theory out. I'll probably go with steel chain rings as well since know one has had much to say on the Al vs Steel question.
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Old 07-21-09, 01:12 PM
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Use mudguards (fenders?) and decent length mudflaps to keep the wheel spray and grit off the chainring.

You can run the chain long past the point where it needs changing as measured for a derailleur. Thorn recommend using a quality chain and keeping it clean and oiled, or using a cheap chain and changing it more frequently.

Thorn are the British Rohloff and expedition touring specialists and they recommend, and sell, a good quality reversible aluminium alloy chain ring to work with the Rohloff steel cog.

Have fun touring.
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Old 07-21-09, 01:45 PM
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Thanks julk. I'm with you when it comes to fenders. A little more weight just means faster descents!

I'll be using a Wipperman 7r8 chain and would like to make it last as long as possible. I'm aware of the thorn ring, but getting it shipped state side isn't really worth it now that the pound has rebounded against the dollar. Blackspire's DH and Mono Veloce rings (they're identical) are similar which is why I'm down to that or a Surly ring. The surly ring isn't nearly as thick, but I've never been one to Mash up hills on tour so I'm not too worried about bending chainrings.
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Old 07-21-09, 03:51 PM
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Waxy;

The Rohloff cog is not that thick either as Rohloff states that it can be used wih their 9 speed chain. A steel chainring of a given thickness should be more resistant to bending too than an aluminum one. Another thing that can help ring stiffness is to use a crankset with a larger diameter spider. I know that my Civia Rohloff came with a 130mm BCD crankset.
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Old 07-22-09, 12:20 PM
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Originally Posted by tatfiend View Post
Another thing that can help ring stiffness is to use a crankset with a larger diameter spider. I know that my Civia Rohloff came with a 130mm BCD crankset.
Would you suspect that a steel ring that is 2+mm thick to be as stiff as a AL ring that is 4mm thick? Also, what crank did your Civia come with? Since Rohloff's require a 54mm chainline, I'm under the impression that most 130 BCD cranksets won't have nearly that wide a chainline. In the case of square taper cranks, this can be fixed at the expense of a wider Q factor.
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Old 07-22-09, 02:26 PM
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The Civia came with the double chainguard version of the Alfine 2 piece external bearing crankset, FC-S500. Per Shimano's web site the chainline is 49.2mm, just within the limits listed in the Rohloff manual of +- 5mm for the crankset chainline. Not perfect but working fine so far.

Aluminum is normally listed as 1/3 the strength and stiffness of the same thickness of steel so I would expect at least equivalent performance. Could also be dependent on the aluminum alloy used however. I am not a metallurgist.
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Old 07-22-09, 02:34 PM
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Thanks tatfiend! I think I'll stick with plan A and use the surly stainless ring. Hopefully a stainless steel ring, a stainless steel cog and a nickel plated steel chain will last a long long time.
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