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DIY Rohloff or Nexus Hub mount for drop bars

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DIY Rohloff or Nexus Hub mount for drop bars

Old 08-20-18, 09:54 AM
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DIY Rohloff or Nexus Hub mount for drop bars

Built up a frankenbike, Trek 7.1FX with Shimano 7 nexus IGH and Salsa Woodchipper gravel bars and had to create a DIY mount the Nexus 7 shifter. FWIW, the standard Rohloff and Nexus shifters all require a 22.2mm handlebar while most road bars are 23.8mm (we are not talking about the stem clamp area here). This makes mounting a standard Rohloff or Nexus shifter impossible without a new shifter, a specialized set of handlebar, some sort of adaptor or mount. A variety of options were detailed here but after looking up some of the prices on these, I thought I would instead create my own. Total cost for the hardware was like $7 versus the $60 for a HubBub mount.

I essentially wanted to re-create the HubBub Drop Bar Adaptor (#11 in the article above) and mount the gripshifter as a bar end shifter. Most bar end shifters are expansion/friction mounted and IMO fairly easy to recreate. Since handlebar inner diameters are not standardized and local parts availability can vary wildly, the instructions below are fairly fluid and will require some trail and error on your part. I'd recommend just taking the bars in question to the local hardware store and play around with what they have.

The basic idea was to use cut slots into an aluminum pipe and use a nut/bolt to wedge in the pipe thus forcing the slotted pipe to expand and hold in place. Sorry I don't have step-by-step pictures as I was kind of figuring things out as I went along but I did manage to take some pics. I may make another one just to take better pics.

For this, you will need:
vise or a friend to hold the pipe sturdy as you cut it
Hacksaw with fine tooth blade
Files, a half-bastard or flat and round will do nicely
Aluminum pipe - the closer you can get the outer diameter of the pipe to 22.2mm while still fitting inside your particular handlebars the better.
Allen head bolt, washer, hex nut

Step 1: go to hardware store and find the hardware. In my particular case, the closest to 22.2mm I could find was a 3/4" OD Al pipe (~19mm). A M10 allen head bolt (80mm long) and hex nut was just the right size to slip in the handlebar but also create a wedge in the 3/4" pipe. I forget the exact size but the OD of the washer was 19mm. The washer is also used as a wedge.

Step 2: Cut the Al pipe to length. You will want to cut the pipe so that you can just barely thread the nut onto the bolt when passing the bolt through the washer and pipe. For my example, it was ~3" long.

Step 3: At one end, cut four evenly spaced slots down ~1"



Step 4: At the other end, take your hex nut and mark the pipe where the corners of the hex nut will sit against. This is where you will cut slots into. The slots will act as a holder and stop the nut from spinning when you tighten everything up. I'm sure you guys will be like "duh" but don't cut the slots so far down, that you lose structural integrity of the Al pipe.

marked the corners of the hex nut for where to cut my slots

Step 5: Drill holes at the end of each slot. The hole should be larger than the slot. The hole acts as a stress relief and helps prevents the Al from cracking or splitting along the axis of the slot.

Note: one slot was not yet drilled.

Step 6: spread the arms on the side where the nut will go but don't spread them too far that you can't get them into the handlebar.

You are trying to wedge the nut into the slots like the above picture to a) keep the nut from spinning when you tighten the assembly and b) the nut will expand the arms out creating your expansion/friction fit against the handlebars. On the four slot side, the washer will act to expand the arms.

Step 7: file off all burrs from the outside, inside, tops, bottoms.

Step 8: Assemble the "bar end mount": Bolt, washer, pipe (with the four slot side against the washer) and nut. On the four slot side, make sure the washer is pressed flush into the four arms. The hex nut does not have to be pressed into the arms yet. Hopefully, when you start tightening, the arms should hold onto the corners and start pulling the nut into the arms, expanding the arms.

Slide mount into handle bar at least as far as the holes, making sure that the end with the nut goes in first. Slide shifter onto the mount, ideally, you want the shifter sitting on the slots, before the holes. once you have everything aligned, tighten the "bar end mount" with a allen wrench until everything feels tight. Depending on how close your pipe matches the 22.2mm it may take a while.

If all you feel is spinning, that means the hex nut did not engage with the slots you cut out and you should pull the assembly back out to maybe spread the arms out more or pre-tighten the assembly more. I found getting the shifter to stay tight (even after tightening the shifter clamp) was the more critical and harder one to achieve and required me to re-position the whole assembly a couple of times before I was satisfied so be prepared to set it, ride it around and test it and redo it if necessary.

Note: I had to cut about a 1/4" from each side after this pic since the pipe was too long and I was unable to begin threading the nut onto the bolt.

And I don't even have a finished photo, lol. Will have to update this later for sure.

Last edited by zze86; 08-20-18 at 10:03 AM.
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