Author Topic: 650b v 26"  (Read 281 times)

niggle

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650b v 26"
« on: July 20, 2020, 01:43:18 PM »
Hi all, I am planning to build up a Rohloff frame for medium to moderately heavy loaded touring, but also for use on local tracks and trails, which are mainly gravel with the odd rocky stretch. I will have to build my own wheels (for which I have a fair amount of experience) as SJSC say they are not building wheels ATM.

I am unsure whether to build it with 26" or 650b rims/tyres (650b would be the Nomad Mk3, but 26" would allow me a choice of the various NOS Nomad/Raven frames that SJSC have for sale). How much difference is there really in strength, ride quality, etc. between the two? If anybody has had the opportunity to compare a Thorn 26" tourer with a 650b one I would be particularly interested in their thoughts and experiences.

I am also curious re Thorns choice of the Ryde Rival 26 rim as opposed to the Andra 35 or 40 which are available in 650b diameter (and disc specific), when Ryde rate the load capacity of the Rival lower than the Andra 35 and much lower than the Andra 40.

https://www.ryde.nl/rival-26

https://www.ryde.nl/andra-35

https://www.ryde.nl/andra-40

(The Andra 30 is not available in 650b)

Also SJSC don't list any Rohloff specific versions of any 650b rims, so is this a question of lack of availability or lack of necessity?

martinf

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Re: 650b v 26"
« Reply #1 on: July 20, 2020, 10:17:44 PM »
I am unsure whether to build it with 26" or 650b rims/tyres (650b would be the Nomad Mk3, but 26" would allow me a choice of the various NOS Nomad/Raven frames that SJSC have for sale). How much difference is there really in strength, ride quality, etc. between the two? If anybody has had the opportunity to compare a Thorn 26" tourer with a 650b one I would be particularly interested in their thoughts and experiences.

I have Thorns with 50x559 26" tyres and an old 650B bike with 50x584 tyres. In the same model (Marathon Supreme) there is very little difference between the two sizes of tyres.

At present, there is more choice of high quality tyres in the 650B size, as they have become fashionable again, while 559 26" seems to be going out of fashion. I have been using 650B since about 1983 and it had been getting progressively harder to find decent tyres until about 5 years ago.


I am also curious re Thorns choice of the Ryde Rival 26 rim as opposed to the Andra 35 or 40 which are available in 650b diameter (and disc specific), when Ryde rate the load capacity of the Rival lower than the Andra 35 and much lower than the Andra 40.

Also SJSC don't list any Rohloff specific versions of any 650b rims, so is this a question of lack of availability or lack of necessity?

Ryde Rival is much lighter than the two Andra rims, partly because it is designed to be disc only, while the Andra rims were originally designed to use rim brakes, with thicker walls to absorb wear. The Rival is also tubeless ready (another relatively recent development) which may account for Thorn choosing it.

I suspect the lack of Rohloff-specific versions is an availability problem.

PH

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Re: 650b v 26"
« Reply #2 on: July 21, 2020, 02:15:22 PM »
[At present, there is more choice of high quality tyres in the 650B size, as they have become fashionable again, while 559 26" seems to be going out of fashion. I have been using 650B since about 1983 and it had been getting progressively harder to find decent tyres until about 5 years ago.

This would be the deciding factor for me, several decent 26" tyres seem to have been dropped and I can see that trend continuing unless fashions change back and there's little reason for them to do that (In as much as there's any reason for fashion...)
As for dedicated Rohloff rims - the thing that makes them specific is the spoke angle.  It's pretty acute in a 26" rim, less so in 650B and by the time you get to 700C it isn't far off the norm.  Dave Whittle answered a query from me a while back with a diagram that showed a 1X Rohloff build in 700c had the spoke angle at the rim the same as a 3X on a conventional hub.
1X does seem to be Thorns preferred way of building, with many if not all the bikes in the current brochures also built with all the heads out.  I understand the 1 X, but am not sure of the reason for heads out.  It leaves me with a bit of a dilemma, I bought another Rohloff (Good prices currently at SJS) but my trusted local wheel builder won't consider anything other than the conventional 2X.  I might end up doing it myself, I've built a few but the Rohloff makes me nervous... 

martinf

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Re: 650b v 26"
« Reply #3 on: July 21, 2020, 11:15:12 PM »
I think the reason for all heads out is to reduce the lateral angle the spoke makes at the rim.

This angle is greater with the large flange of the Rohloff than it is with a "normal" hub. 

I think this is a very good idea with big hubs in small wheels, where the angles are much more pronounced. I intend building a Nexus 8 Premium hub onto a 16" rim for a Brompton soon (had the parts for a long time but waiting on a rear triangle from Kinetics), and I have planned to do it 1X all heads out as advised by SJS.

For 26" and larger wheels I am not sure it matters very much, several of the family bikes have Nexus 8 Premium or Rohloff hubs and none are built all heads out and there has never been a problem with any of the wheel builds. The two Rohloff hubs I own were both built 2 cross onto 26" rims by SJS a few years ago, their 1 cross for large wheels seems to be a relatively recent thing.

My first Rohloff came in a complete bike, for my second one I preferred to have SJS do the build as that gives a guarantee on a very expensive wheel and I didn't know all the specifics for a Rohloff build at the time. Thanks to the exchanges on this forum I would now feel confident enough to do the job myself if I ever get another Rohloff.

All the Nexus 8 Premium builds are my own.

niggle

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Re: 650b v 26"
« Reply #4 on: July 22, 2020, 07:37:43 PM »
Thanks all, very helpful.

I am erring towards 650b I think, maybe the Andra 35 rim as I am not keen on going tubeless on a touring bike at this stage.

Re spoke patterns I can see the sense in all heads out for a Rohloff build, it will avoid any stress on the flange outer edge, as well as the spokes being at a closer angle at the rim as martinf says (could be interesting lacing the thing though!). I always build large hubs such as IGHs with Sapim Polyax nipples as they really do align with a wider spoke angle than other nipples IME, usually with Sapim Race spokes.

PH

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Re: 650b v 26"
« Reply #5 on: July 22, 2020, 10:18:05 PM »
I always build large hubs such as IGHs with Sapim Polyax nipples as they really do align with a wider spoke angle than other nipples IME, usually with Sapim Race spokes.
You probably already know, but just in case... Rohloff specify specific spokes for building, something to do with the elbow measurement, using anything else may effect the warranty.

niggle

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Re: 650b v 26"
« Reply #6 on: July 24, 2020, 07:58:04 AM »
I always build large hubs such as IGHs with Sapim Polyax nipples as they really do align with a wider spoke angle than other nipples IME, usually with Sapim Race spokes.
You probably already know, but just in case... Rohloff specify specific spokes for building, something to do with the elbow measurement, using anything else may effect the warranty.

Hi yes I am aware of that thanks, I will be buying the Rohloff specific spokes from SJSC.