Author Topic: Rohloff hub, 26" to 700c rim  (Read 1705 times)

Tiberius

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Rohloff hub, 26" to 700c rim
« on: June 13, 2019, 01:14:49 PM »
My Rohloff hub/wheel is currently built with a 26" rim. I'm thinking about building a Thorn Mercury which will obviously mean rebuilding the hub with a 700c rim. The hub is 36h.

I seem to remember reading that this was not recommended by Rohloff, that if the hub was (say) built with a 26" rim then it should always be built as a 26" rim.

It doesn't sound right to me and I can't see the logic. I guess it's something to do with stress on different parts ofthe hub?

I have had a look around but I can't find where I read it.

Is this true, is this rubbish or did I dream it ???

PH

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Re: Rohloff hub, 26" to 700c rim
« Reply #1 on: June 13, 2019, 01:38:19 PM »
You are right it isn’t recommended, not just for a Rohloff, it’s true for any hub.  The change in the way the spokes fit in the hub weakens it.  I Changed mine from 26” to 700c and a couple of years later had a spoke pull through cracking a the hub.  Rohloff wouldn’t replace foc as they would have if I hadn’t changed sizes, for various reasons Thorn kindly did it for me as a goodwill gesture, though you shouldn’t expect that.  Worst case scenario, I would have had to buy the shell which I think at the time (3 years ago) was £125
What is the hub now?  A Mercury is better disc and requires internal shifting, if you need it adapted you could find out the difference to include the complete shell.
I’ve had my Mercury about 18 months, bought the frameset, had the hub adapted, upgraded a couple of parts, replaced what wasn’t compatible... If I was doing it again I’d buy a complete bike and sell what I already had, there wouldn’t have been much difference in costs.
« Last Edit: June 13, 2019, 01:42:51 PM by PH »

martinf

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Re: Rohloff hub, 26" to 700c rim
« Reply #2 on: June 13, 2019, 08:16:00 PM »
I've done rebuilds with different sized rims several times with other hubs and got away with it so far.

I don't reckon it is a problem with steel flanged hubs (old Sturmey Archer and SRAM) but it is definitely not recommended with aluminium alloy flanges.

But I have done some, including a Nexus 7 (initial build on a 16" rim, final build on 26"). A Nexus 7 is similar in dimensions to a Rohloff, although I don't think I would risk it with the much more expensive Rohloff hub.

AFAIK the reason is that the steel spokes "bed" into the softer aluminium alloy flange.

Just as bad or even worse is changing the spoking pattern when rebuilding with the same size of rim. I once made a mistake and built a wheel with spokes crossing over the valve hole, leaving less space to fit a pump. Rather than risk weakening the flange I left the wheel as it was rather than rebuild it as it "ought" to have been done.

Tiberius

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Re: Rohloff hub, 26" to 700c rim
« Reply #3 on: June 14, 2019, 08:30:43 AM »
If I was doing it again I’d buy a complete bike and sell what I already had, there wouldn’t have been much difference in costs.

Thank you for the replies gents, enlightening stuff.

PH...That bit of info' quoted above is very interesting and something that I need to think about.

Pavel

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Re: Rohloff hub, 26" to 700c rim
« Reply #4 on: December 27, 2019, 04:47:48 PM »
I wonder how complex a job it is, to replace the Rohloff shell?  I further wonder if it would be possible, and practical, to remove the Rohloff innards, leaving the shell laced in place, and sliding the innards inside of another shell, laced up with a different size wheel?

Think of the savings, when experimenting with other frames and wheel size combinations, if not yet sure that a second Rohloff is the best choice, or if unsure of say, A Nomad, is best with a 26" setup versus 650b or 700cm.  Hmmmm.


Danneaux

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Re: Rohloff hub, 26" to 700c rim
« Reply #5 on: December 27, 2019, 05:26:20 PM »
Quote
...I further wonder if it would be possible, and practical, to remove the Rohloff innards, leaving the shell laced in place, and sliding the innards inside of another shell, laced up with a different size wheel?
Like most things in cycling, "it's been done already". ;) In this case, by Kindernay:
https://kindernay.com/

Discussed earlier here and elsewhere:
http://thorncyclesforum.co.uk/index.php?topic=12060.msg87701#msg87701
http://thorncyclesforum.co.uk/index.php?topic=13366.msg100363#msg100363
https://www.cyclingabout.com/kindernay-xiv-hub-14-speed-internally-geared-hub/

Best,

Dan.

mickeg

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Re: Rohloff hub, 26" to 700c rim
« Reply #6 on: December 27, 2019, 06:31:47 PM »
If you decide to convert your existing hub to 700c from 26 inch, if you do not have the reinforcing rings for the flanges, you might consider adding them at that time.

There was a fairly long thread on the rings.  I added the rings to my wheel, described it at this post.
http://thorncyclesforum.co.uk/index.php?topic=11802.msg99847#msg99847

You will notice in that thread that apparently there are rings that the shop can add to a hub using heat to get a tight fit.  That might be a better option for you if you make the switch.

Tiberius

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Re: Rohloff hub, 26" to 700c rim
« Reply #7 on: December 28, 2019, 01:03:07 PM »
Just to add an update to my original post.

Despite being advised not to do it I did it anyway (I'm like that) I had the 26" rim and spokes removed and had a 700c rim built onto the Rohloff hub. As 'mickeg' pointed out above I had the flange support rings fitted at the same time. The work was carried out by an official UK Rohloff main agent (not SJS) and they didn't bat an eye when I asked them to do it.

All good so far but I haven't really done enough miles on the build to know if all will be well long term.

Whatever, it's now done. If/when the whole thing flys apart you guys will be the first to know.... :D


Pavel

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Re: Rohloff hub, 26" to 700c rim
« Reply #8 on: January 29, 2020, 05:15:20 PM »
Keep us posted Tiberius, and I for one would be highly interested in your thoughts in regards to the differences in feel as you perceive them between riding a 26 Rohloff versus on 700cc wheeled one.

I have a Thorn RST, and judging by the tubes, I wonder if it's not the equivalent of the new Mercury, with only the wheel size as a difference.

Tiberius

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Re: Rohloff hub, 26" to 700c rim
« Reply #9 on: January 29, 2020, 06:50:02 PM »
Pavel

I will do.... ;)

martinf

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Re: Rohloff hub, 26" to 700c rim
« Reply #10 on: January 29, 2020, 11:10:43 PM »
I have a Thorn RST, and judging by the tubes, I wonder if it's not the equivalent of the new Mercury, with only the wheel size as a difference.

I reckon the Thorn RST is more or less the old equivalent of the Mercury.

I can see two main differences on the RST compared to the Mercury:

- 26" tyres, which might become a problem in a few years time.
- V-brakes and no possibility for disc brakes.

I bought a Raven Sport Tour frame when SJS were selling them off at a discount after the introduction of the Mercury.  I don't reckon I need disc brakes, especially on a reasonably light bike that is used mainly on good road surfaces. And at the time I thought it would be better to have 26" rather than 700C as all the recent large-wheel bikes I maintain are this size, so if necessary I could swap wheels between them.

The Raven Sport Tour also cost me about half the price I would have paid to build up a Mercury with similar components.


PH

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Re: Rohloff hub, 26" to 700c rim
« Reply #11 on: January 30, 2020, 10:59:14 AM »
I have a Thorn RST, and judging by the tubes, I wonder if it's not the equivalent of the new Mercury, with only the wheel size as a difference.
I went 26" to 700c and although the bikes had other differences it was IMO wheel size that made the biggest. 
Of course there's always the perception v's reality, I have no idea how to separate them, I just know I much prefer riding 700c bikes.

geocycle

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Re: Rohloff hub, 26" to 700c rim
« Reply #12 on: January 30, 2020, 04:50:33 PM »
I have a Thorn RST, and judging by the tubes, I wonder if it's not the equivalent of the new Mercury, with only the wheel size as a difference.

I reckon the Thorn RST is more or less the old equivalent of the Mercury.

I can see two main differences on the RST compared to the Mercury:

- 26" tyres, which might become a problem in a few years time.
- V-brakes and no possibility for disc brakes.

I bought a Raven Sport Tour frame when SJS were selling them off at a discount after the introduction of the Mercury.  I don't reckon I need disc brakes, especially on a reasonably light bike that is used mainly on good road surfaces. And at the time I thought it would be better to have 26" rather than 700C as all the recent large-wheel bikes I maintain are this size, so if necessary I could swap wheels between them.

The Raven Sport Tour also cost me about half the price I would have paid to build up a Mercury with similar components.

That's pretty much where I am now.  I built up an RST from an RT.  I have nothing but praise for the RST, a fantastic bike for multiday tours and my gravel track commute.  My only concern is being overtaken by the fashion for 700c and disks.  If the mercury were not £3.5k I would probably upgrade, or  more likely buy a frame and re-purpose the rohloff as others have done.  TBH I feel an irrational connection with my hub that has carried me 40,000 miles or so!
 

Pavel

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Re: Rohloff hub, 26" to 700c rim
« Reply #13 on: January 30, 2020, 06:59:16 PM »
C'mon you all. We aren't thinking ahead properly.  We've all seen the bicycle game and how it's played.  Never sell your 26" wheeled machine! By 2034 they will be the hottest ticket around and we can mount those new tubeless and tyreless, air-only 26" hover-wheels, on again, and fly up those hills.

By then, my RST will be like a rare Rene Herse. My future grandkids will think me wise for such a special gift, one near impossible to find in ANY barn!