Rohloff hub

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crossy
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Rohloff hub

Post by crossy »

If I bought a bike with a 26” Rohloff wheel and could I take that Rohloff hub out of the bike and build it into a 20” wheel. Or do you need a special hub for a 20” wheel? I’ve seen a Rohloff hub for a 20” wheel but is it really necessary?
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PH
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Re: Rohloff hub

Post by PH »

crossy wrote: 21 Mar 2023, 8:55pm If I bought a bike with a 26” Rohloff wheel and could I take that Rohloff hub out of the bike and build it into a 20” wheel. Or do you need a special hub for a 20” wheel? I’ve seen a Rohloff hub for a 20” wheel but is it really necessary?
There isn't a specific hub for a 20" wheel. so yes it'll be the same hub and you could. Whether you should is a different question, there is a risk when changing wheel sizes. The spokes will have settled into the hub flange, this happens with all hubs it isn't Rohloff specific, and changing the spoke pattern will disturb that, Rohloff recommend not doing so.
How much of a risk I can't say, neither can I say if it's worth taking it. It depends in part how much the hub costs. I have a Rohloff that started in a 24" wheel, was transferred into a 20" wheel, where it wasn't used much, then came to me and was built back into a 24". So far so good.
If you do proceed, make sure the hub has flange support rings and if not add them. All new hubs have come with them fitted for a number of years.
Keezx
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Re: Rohloff hub

Post by Keezx »

IMO the only potential problem when building a hub in another rim is the nipples will likely not be correctly aligned in the spoke holes in the.rim...especially in small rims like 20"
So rim holes must be machined with a matching drill, otherwise you will encounter spoke breakage...
cycle tramp
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Re: Rohloff hub

Post by cycle tramp »

...rolhoff do advise that once the wheel has been built, to keep with the same spoke pattern and rim size.... it may be worth asking rolhoff if they could fit the same internals into a new hub shell..
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PT1029
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Re: Rohloff hub

Post by PT1029 »

+1 for Rohloff say not to change wheel sizes once a wheel has been built. I forget if this is a recommendation or a void the warranty issue.
Occasionally the flanges break, new hub shells can be fitted to the internals at Rohloff (and possibly at Thorn in Bridegwater?). A friend did this himeself in a hotel room in Thailand.
If not already got, add flange rings for stronger flanges, which ring is determined by the hub serial number.

I think Rohloff only deal with hubs registered with them when purchased, as an anti theft measure.
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simonineaston
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Re: Rohloff hub

Post by simonineaston »

Not mentioned yet but do recall that all other things being equal, the over-all gear range will be lower in the 20" rim than it was in the larger rim. Sheldon's gear chart will show the differences.
https://sheldonbrown.com/gear-calc.html
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pwa
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Re: Rohloff hub

Post by pwa »

simonineaston wrote: 22 Mar 2023, 7:04am Not mentioned yet but do recall that all other things being equal, the over-all gear range will be lower in the 20" rim than it was in the larger rim. Sheldon's gear chart will show the differences.
https://sheldonbrown.com/gear-calc.html
Probably much too low unless a very large chainring and small sprocket are used.
Galactic
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Re: Rohloff hub

Post by Galactic »

PT1029 wrote: 22 Mar 2023, 6:58am I think Rohloff only deal with hubs registered with them when purchased, as an anti theft measure.
If the hub hasn't already been registered then you can register it any time on their website (needs photo of original receipt or similar). You can also check whether the hub has been registered on their website, and if I remember right, there are instructions of what to do if you want to register an already registered second hand hub.
Norman H
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Re: Rohloff hub

Post by Norman H »

I'd be inclined to give it a go, fitting the flange support rings would be a wise precaution, and if the worse happens a new hub shell can always be fitted. Another problem you will face is the 20” wheel will need to be built 1X, although this may work in your favour as the spoke angles at the flange might not be too different from a 26” 2X wheel.

Incidentally, as I understand it the flange reinforcing rings are no guarantee against the flange cracking but are designed to contain the crack and prevent a catastrophic failure. There are two types of reinforcing rings, the DIY version are a push fit on the flange but those fitted by Rohloff or their approved service centres are heat shrunk onto the flange.
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simonineaston
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Re: Rohloff hub

Post by simonineaston »

Probably much too low unless a very large chainring and small sprocket are used.
Not necessarily so, gear range being a matter of personal preference & varying with circumstances. For example the gear range shown here would suit a lot folk fine. The sprockets in this example are readily available.
screenshot of gear chart
screenshot of gear chart
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[XAP]Bob
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Re: Rohloff hub

Post by [XAP]Bob »

cycle tramp wrote: 21 Mar 2023, 10:23pm ...rolhoff do advise that once the wheel has been built, to keep with the same spoke pattern and rim size.... it may be worth asking rolhoff if they could fit the same internals into a new hub shell..
I know they can, they did for me when they broke the old shell trying to replace the end cap.
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Lodge
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Re: Rohloff hub

Post by Lodge »

As with some of the other comments I would give it a go.

I currently have three Rohloff hubs, all of which have been transferred between machines.

The oldest has now done over 30,000 miles and is in its third machine. The first 20k were in a 26” wheel Patria tourer. Then the next 10k in an ICE trike, also 26” (but different rim). It’s just been put in a 20” wheel in my Tern Vektron ebike to replace a Shimano Alfine 11.

Another Rohloff (nice red one) started in a 24” wheel Bacchetta Giro for 7000 miles, then went to the 26” Patria tourer for a couple of thousand and then to our 26” Hase Pino for last 1500 miles or so.

The third started in a Brompton (replacing the Simano Alfine 11 which went to the Tern) and last year was transferred to my wife’s Tern Vektron. The Alfine is now back in the Brompton from which it came.

With all changes I maintained, as best I could, the same spoke angles rather than create new dinks in the flanges, even if that meant not having the valve hole in the classical position. For the more recent rebuilds flange support rings have been used although they weren’t at first. So far so good, touch wood and fingers crossed.

As may be obvious I don’t like losing Rohloff hubs but keep to replace the derailleurs that came with new bikes. The only derailleur I have (from my wife’s Tern) is now on my old Patria which is only used on a turbo trainer.
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531colin
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Re: Rohloff hub

Post by 531colin »

Keezx wrote: 21 Mar 2023, 10:19pm IMO the only potential problem when building a hub in another rim is the nipples will likely not be correctly aligned in the spoke holes in the.rim...especially in small rims like 20"
So rim holes must be machined with a matching drill, otherwise you will encounter spoke breakage...
this has come up often enough before, most recently I think here..viewtopic.php?p=1756555#p1756555

....So, same question.....
....is spoke fatigue where the nipple forms an unfortunate angle with the rim a real world problem?
I don't ever remember seeing fatigue at the rim end, where the spoke enters the nipple, but its common enough at the elbow bend at the hub end.
pwa
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Re: Rohloff hub

Post by pwa »

simonineaston wrote: 22 Mar 2023, 9:16am
Probably much too low unless a very large chainring and small sprocket are used.
Not necessarily so, gear range being a matter of personal preference & varying with circumstances. For example the gear range shown here would suit a lot folk fine. The sprockets in this example are readily available.Screenshot 2023-03-22 at 09.13.25.png
I stand corrected. 19.8 is useful for anyone who likes spinning up a steep incline. I was anticipating something below 17 for that wheel size, which was obviously a miscalculation on my part. For the sake of efficiency I'd go for the largest sensible ring paired with the sprocket that gives the right gears, since bigger sprockets work better with the chain.
wheelyhappy99
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Re: Rohloff hub

Post by wheelyhappy99 »

I have a Rohloff fitted in 20"/ 406 rims. With a 39 tooth chainring and 13 tooth sprocket the gear range is almost exactly the same as my 26"/ 559 rim with 45 and 19 teeth. About 1.38- 7.24m, or in gear inches 17" to 90".
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