Custom Rohloff Downtube Shifter Mount
[John Peterson came up with the following method for mounting a Rohloff shifter on a downtube shifter boss. —ed.]
The Rohloff shifter is designed to work with mountain bike bars. If you want to run a Rohloff hub with drop bars you have a problem. Sheldon Brown describes what appears to be a good work around by mounting the shifter to the stem. There is also a bar extension called the HubBub that allows the shifter to mount off the end of the drop bar. Go here for more info on both.
I would not claim to have discovered the ideal solution for everyone but for my purposes mounting the shifter on the down tube, in the “traditional” position, has worked out pretty well. One drawback to this mount is that I can’t see what gear I’m in most of the time because the angle is wrong making it hard to see the markings on the grip. That is a very minor issue. A huge plus is that the shifter does not rotate with the bars which allows for a shorter, more direct cable run.
The basic mount is a slightly modified Greenspeed long computer mount. The length and diameter of the mount match the Rohloff shifter perfectly.
I needed to “machine” the mount to fit the radius of the frame tube. I did that with 120 grit adhesive backed sandpaper stuck to an appropriate diameter of PVC pipe clamped in a vice. The alloy Greenspeed uses for the mount is quite soft and sliding it back and forth on the sandpaper cut the needed radius quickly. I cut a rubber gasket to put between the shifter mount and the frame. I put a washer (or maybe two) on the bolt inside the mount as a shim so that the mount is tight against the shifter boss at the same time that it is snug against the frame to maximize the strength and minimize strain on the boss. I used blue loctite on the threads to keep it all snug.
I was concerned that I would drop the bike or bump a doorway and damage the frame. The reality is that when the bike is all assembled the clutter of the pedals and handlebar protects the location pretty well. I have close to 4,000 miles since I put this together and no problems yet.
I chose to run the cables under the bottom bracket and along the chain stays. I have to push them pretty wide at the bottom bracket so they don’t rub the 700-37 tires I’m running. I like having the cables out of the way but I have considered running them to the top tube and then down the seat stays. Either method of cable routing would work with this mount. With Cross Check frame I was able to utilize the down tube frame boss for the shifter. I think a person could make this work on a frame without a downtube shifter mount by modifying the Greenspeed circle clamp that comes with the mount. —John Peterson
9 Responses to “Custom Rohloff Downtube Shifter Mount”
Nice work John!
Of course this points out the flaw in the Rohloff drivetrain … they can design and manufacture an outstanding internal hub drivetrain, but they can’t make a shifter for road bars? C’Mon!
Sorry for the rant, but I was wondering if anyone could enlighten me about this? What am I overlooking about their design that limits the shifter options?
I agree completely that Rohloff is missing a market by not providing a shifter for use with a drop bar. There are two German market products that I’m aware of that solve the problem. One is a two piece bar so you can insert the shifter, then re-assemble the bar. The other is a multi piece shifter that will slide around the curves on a drop bar. Both of these would let you put the shifter near the center clamp on the bar which seems ideal to me. Both of these are quite expensive even for people willing to fund the hub in the first place.
My point is that there is no apparent limitation of the hub design. I guess my second point is that there are better solutions than mine but for me the cost/benefit ratio doesn’t make sense.
John
I went with the more traditional HubBub Rohloff mount and like it for the most part, but I agree it would be very nice to see a real road shifter, or even an STI shifter…
The main reasons for the difficulty in developing an alternative shifter for the Rohloff hub are the amount of cable moved and the dual cable pull-pull design of the shifting mechanism. A full range shift low to high pulls almost 4″ of cable. An average Shimano rear derailleur pulls about .7″ over the full shift range and needs only one cable due to the spring loading of the derailleur.
Another difference is that for a derailleur the indexing is in the shifter while for the Rohloff hub the indexing is done in the hub itself. This makes for a very simple and reliable twist shifter as currently used.
A very different mechanism would be required for a brifter for the Rohloff hub or the shifting mechanism in the hub would need to be totally revised. Also due to the number of patents Shimano and Campy have on brifter mechanisms a new design which does not infringe on patents i not easy. It took SRAM a long time to manage it and they are far larger than Rohloff.
Thanks for the explanation — it’s very enlightening.
Perhaps one way of dealing with the issue is a redesigned (optional?) click-box, where there was a fairly powerful return spring and a pulley system with reducer gears. This would allow the same effective action, at least for speedhubs with the external clickbox.
No doubt it would be bigger, heavier, and less reliable, but by varying the gear ratios and spring tension you could adapt it to work with pretty much any linear indexed shifting system I would think. Then again, there are probably things I am overlooking.
For now, the twist shifter on the hub-bub works for me.
Dolan;
The indexing is I believe in the hub itself, not in the internal or optional external shifter box.
I have the Civia Hyland Rohloff bike with flat bars and like it but I also have two other IGH bikes I have made up with drop bars. One uses the latest Shimano Alfine hub and the Jtek bar end shifter. The other uses a SRAM P5 hub and a Hubbub adapter for the rotary shifter like your Rohloff setup. Both work well IMO.
As for using another shifter with the Rohloff please show me a 14 speed indexed shifter. I am afraid that any solution is going to need to come from Rohloff or a independent maker such as Jtek.
Another problem few are aware of is that derailleur indexed shifters are not linear in their cable pull. They pull considerably more cable at the low and high ends than in the middle gears on the casette. This is due to the geometry of a parallelogram rear derailleur.
I have started a IGH bikes Yahoo group for anyone interested. Click on my name to visit and consider joining.
[...] is another option, although very ugly! http://www.ecovelo.info/2009/02/22/c…shifter-mount/ I hope someone develops a nicer shifter for the rohloff soon, heard its very tricky but hopefully [...]
With regard to the downtube Rohloff shifter option I was intrigued to see if I could come up with a way of getting the shifter up to the bars. I am currently building up a speedhub bike as a tourer and will be using drops. Anyhow I have come up with an adjustable system which places the shifter to the left of your brake hood on the right side of the handlebar, around the position that a suntour command shifter would be. It is fully adjustable in three aspects and can be built for around $50. Cheaper if you have parts lying around. In my opinion it is elegant and useful as a computer and light mount aswell. I have just subscribed so do not know how to upload picturesd etc, as in this feed. If anyone is interested I would be happy to supply the info.
Cheers
Jon;
Definitely interested in seeing your design but you provided no contact information in your post. Click on my name in this post heading to visit the Yahoo Geared Hub Bikes group that I am founder and owner of. I can be reached through it or email me at astronut1001 at yahoo dot com.