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Single speed/internal gear hub chain tightness question

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Single speed/internal gear hub chain tightness question

Old 07-20-15, 06:42 PM
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Single speed/internal gear hub chain tightness question

Picture a bike with horizontal dropouts, an internal gear hub clamped to dropouts tightly with axle nuts -- not skewer -- and with a bash guard on the chainring and an anti-drop inboard on the chainring, and an internal and external chainguard ring sandwiching the cog on the internal gear hub. These guards should make chain drop all but impossible. In this situation, is it a problem to run the chain looser than one would if there were not front/rear anti-drop chain guards? Too tight damages bearings and decreases efficiency. Does too loose cause a problem (again, considering that chain drop is probably almost totally prevented by the front/rear guards)?

I ask because I seem to get some movement on the axle and therefore chain loosening despite applying the proper torque on the axle nuts. Even if I exceed the recommended torque, I get some loosening and I am not a high-watts rider by any means. The dropouts are parallel and clean, and the anti-turn washers on this Alfine 11 are clean and properly seated. The axle and nut threads are well greased, but the contacting faces that supply grip against the dropouts are clean and dry and should have sufficient bite to prevent slip, but I still get some forward axle movement.
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Old 07-20-15, 06:59 PM
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I run all my IGH bikes with a slight, barely noticeable droop in the chain. Have never once thrown a chain on any of them. The ideal tension is no tension.
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Old 07-21-15, 11:15 AM
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If the chain doesn't fall off I don't think there would be any problem with it being slack. The axle shouldn't move at all however. I'd check out this again.
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Old 07-21-15, 11:24 AM
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Are you using track nuts or serrated washers on the outside of the dropout? That will keep your axle from moving forward.

I'm with Mr. Burkhart, I run my single speed chains fairly droopy and it's still physically impossible to derail them.





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Old 07-21-15, 11:25 AM
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Originally Posted by motorapido
Picture a bike with horizontal dropouts, an internal gear hub clamped to dropouts tightly with axle nuts -- not skewer -- and with a bash guard on the chainring and an anti-drop inboard on the chainring, and an internal and external chainguard ring sandwiching the cog on the internal gear hub. These guards should make chain drop all but impossible. In this situation, is it a problem to run the chain looser than one would if there were not front/rear anti-drop chain guards? Too tight damages bearings and decreases efficiency. Does too loose cause a problem (again, considering that chain drop is probably almost totally prevented by the front/rear guards)?

I ask because I seem to get some movement on the axle and therefore chain loosening despite applying the proper torque on the axle nuts. Even if I exceed the recommended torque, I get some loosening and I am not a high-watts rider by any means. The dropouts are parallel and clean, and the anti-turn washers on this Alfine 11 are clean and properly seated. The axle and nut threads are well greased, but the contacting faces that supply grip against the dropouts are clean and dry and should have sufficient bite to prevent slip, but I still get some forward axle movement.
Perhaps your chainring and/or cog is not perfectly round, and so there is a tight spot in the crank rotation that ends up pulling the wheel forward.

If you have a derailleur bike sitting around, take a look at how much the top run of chain droops and replicate that.
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Old 07-21-15, 01:28 PM
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The only real problem with a slack chain is that it will rattle or slap in the chaincase when you go over bumps or stop pedaling. I don't think having a slack chain can increase sprocket wear or cause any other problems like that, but it can be difficult finding the balance between a too-tight chain and one that makes annoying noises in the chaincase.
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