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At the recent Tandem club rally in Germany we had a talk from a representative from the Rohloff company.
One of the things discussed was of course spokes and it turns out unsurprisingly that you need special spokes for a Rohloff hub.
It would seem that the Rohloff needs spokes with a neck length at the bend of 2.9mm which was the standard for spokes back in the day.
This neck length has been reduced for modern day spokes to 2.6mm I believe though this is hard to verify.
According to Rohloff the 2.9mm spokes should be available from their distributors or from Rohloff directly.
So if you order spokes for your wheel you need to check that you are going to be supplied with the right ones.
I understood from the many online reports years ago that the many failures where the flanges broke around the spoke holes was the problem with early Rohloffs used on tandems.
For a while after the initial crop of flange failures SJS sold 48 spoke tandem Rohloffs achieved by drilling spoke holes between the existing 32 holes and fitting 16 radial spokes. Of course as the major seller of Rohloff equipped tandems at the time they did that because obviously there was NO PROBLEM with the Rohloff hub being used on tandems.
Next sales pitch about the frequent broken spokes was that 32 spokes were OK but the fault was poor build as rims needed drilling at the right angle for a Rohloff hub, impossible to alter if you want a double eyeletted rim. Maybe they now use Sapim Polyax nipples which allow for such extreme spoke entry angles. Strangely the nipples pictured on the Rohloff website look very like the polyax. I was also intrigued by the flange supports available as "spares" from Rohloff. I don't think I have ever owned a hub that needed a flange support.
Any reasons given why the OEM Rohloff "specially bent to fit" spokes keep breaking as in the two recent reports on this forum of 5/6 spoke breakages on a wheel ?
Did the Rohloff salesman say who was making their spokes for them ?
I use a DT tensiometer when wheelbuilding and it is amazing the difference in maximum permissible tension between different makes and styles of spokes.
Did the salesman reveal the recommended build settings so the wheel can be tightened to the specific tension for their special spokes ?
He did not say who was supplying the spokes.
The minimum tension recommended for the spokes is 1300N according to their literature
One thing he did say was to re check the spoke tension after the tyre has been fitted and inflated to the required pressure. You should have a minimum tension of 1000N with the tyre inflated.
Build instructions here
Interesting stuff and thanks for the prompt reply. Reading on only recommended for complete spoke-speak nerds.
I would comment that 130kg would be the maximum tension as well being the minimum. Over tightening is as bad for the durability of the whole wheel as being under tensioned IMHO.
The Rohloff Australia link you provided does not reveal the spoke manufacturer recommended by Rohloff, however I can only find a reference to
I am afraid experience tells me that any rear wheel with only 32 or 36 2/1.8/2 spokes will flex and fail in use if I ride it - so I will stick by my view on Rohloffs for tandem use. I was also shocked to see that 1/3 of the Rohloff wheelbuild instructions are illustrating reasons why flanges crack and break. I have never seen another manufacturer include this topic in their hub instructions.
The importance of who makes the spokes and what they are made of is illustrated here, a follow up article to his wheelbuilding book by RM detailing why he now uses a DT Tensiometer , as I do.
Check out the link RM provides to the Sapim factory provided recalibration of a DT Tensiometer. The charts show the ratios at 130KG load (1275 kN), a deflection of 20% more on a 1.8mm spoke compared to the 2.0mm I use.
2.0mm mid 240
1.8mm mid 202
1.7mm mid 181
The full chart link is below. There is a copy n paste error, the Sapim strong numbers should equate to the 2.0mm spoke not the adjacent 1.5mm laser column.
I use Sapim strong spokes for everything except solo front wheels, for which I use Alpina 2.0/1.8/2.0, but not many riders are 130kg solo and a 190kg plus bags tandem team so I understand I am in a very small section of the market.
Thinner spokes may be as strong or last longer (CXray) but they FLEX laterally under load far more than thicker spokes which I found through personal experience caused rapid wheel failures. I have 20ish years of Sapim strong building and so far have broken only one S/strong spoke, on the drive side of my "lightweight" a campy record small flange 32 hole 700c where the non drive side were Alpina. In fairness I had hit a pothole at 40+mph on a Peak district descent when loaded for overnight stop, I was avoiding my mate who was tankslapping past me at the time just before exiting into the hedge and the pothole seemed the better option to me.
I note that the Rohloff AUS website states that using thicker than 2.0 spokes will increase the likelihood of flange breakage on a Rohloff so no way for anyone to build their hub into a stronger wheel.
Enough for now, my dear wife is threatening me with a bike ride, the sun is shining and she thinks we should go out riding the tandem instead of polishing the spokes again.
I also went to the talk by the Rohloff rep at the Rally in Germany last year. What I heard was that the early flange breakages were traced to a rough cutting edge created in the process of forming the spoke head of a particular make of spoke (don't remember what make). This cutting edge or burr acts like a hacksaw cutting into the flange and over time creates a crack. As Stuart says he also emphasised the importance of the correct spoke head length.
We have a Thorn tandem with a Rohloff with 36 spokes and in 10 years including some fully laden touring we have had no trouble of any kind.
(definitely not a spoke or wheel expert!)