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12-07-12, 10:39 AM
Inspired by Sheldon Brown’s conversion of a hybrid bike to a drop handlebar road bike with an internal hub, I set out to do the same thing with my old Trek 7000. There are a number of nuances with a project like this. I thought I‘d share my experiences.
First the materials - Shimano Nexus 8 speed hub for about $150 with the 8 speed shifter ($20), single speed Vuelta crank (new, $50), chain (8 speed SRAM, $16), Alex Adventurer rim ($30), 2 mm spokes (282 mm, $21), nipples ($10), drop bar (used, $8), Tektro linear or direct pull brakes ($32, new) and handlebar wrap ($8).
The first part of the project is to build the wheel. There are several online spoke length calculators to help determine spoke length. They all provided slightly different answers. It’s better to have spokes that are a millimeter or two short than long. In my case, 282 mm was perfect. I’ve built several wheels and have learned to lace the wheel up, true-it, and then at the very end “do the dish” by turning each of the spokes on one side the same amount – in this case one full turn was perfect.
Next is the drop handlebar. I am used to bar end shifters so like Sheldon, I decided to mount the Nexus shifter on the end of the drop bar. The shifter is built for a mountain bike bar (7/8 inch diameter) not a road bike bar (15/16 inch diameter). (I read that there are old drop handlebars that are 7/8 inch diameter but I could not find one.) I needed to adapt the diameter of the drop bar to mount the shifter. I had an old aluminum flag pole set that I was able to use. I used a flat file to reduce the diameter of the road bike drop bar just enough to slide on the aluminum pole transition joint. Then to make sure nothing moved I put in a pop rivet on each side. It may sound clunky but once I wrapped the bar you cannot tell there is a transition joint there. I am sure there are more elegant ways to do this but it works fine for me.
A note about the brake handles – your hybrid brakes are likely V-brakes also known as direct pull brakes. The cable pull on these is longer than most road bike brakes. Tektro makes a linear pull road bike brake handle set that has the necessary pull length for V-brakes. Another option is to use standard road bike brakes handles, with the linear pull adapter “wheel” multiplier.
If your hybrid has vertical dropouts, you will need to carefully choose your front sprocket size. I used one of the online sprocket calculators to determine that a 46 tooth front sprocket combined with the 21 tooth rear cog would be the closest fit. I still had to file about 1/10 on inch notch in the back of my drop outs to get the chain tension just right. This combination of gears gives me about a 1.15 gear ratio in the very lowest gear. This will get me up my 10% slope hill.
Regarding the vertical drop outs, the non-rotation washers supplied with the internal hub kit were all for horizontal drop outs. You will need the “8L (blue/green) non-slip washers for vertical drop outs.
One final tip, I used cable ties to secure the shifter cable. To ease dismounting the hub (such as to repair a flat tire) I used a Velcro closure for the tie closest to the hub on the chain stay.
I’ve been commuting to work (23 miles round trip) and am extremely pleased with the result. In an unexpected surprise, I find the angles and measurements of my hybrid conversion to be quite close to my beloved Surly LHT. Now, I have a great all-weather “rain bike” that has a familiar feel and handling characteristics.
First the materials - Shimano Nexus 8 speed hub for about $150 with the 8 speed shifter ($20), single speed Vuelta crank (new, $50), chain (8 speed SRAM, $16), Alex Adventurer rim ($30), 2 mm spokes (282 mm, $21), nipples ($10), drop bar (used, $8), Tektro linear or direct pull brakes ($32, new) and handlebar wrap ($8).
The first part of the project is to build the wheel. There are several online spoke length calculators to help determine spoke length. They all provided slightly different answers. It’s better to have spokes that are a millimeter or two short than long. In my case, 282 mm was perfect. I’ve built several wheels and have learned to lace the wheel up, true-it, and then at the very end “do the dish” by turning each of the spokes on one side the same amount – in this case one full turn was perfect.
Next is the drop handlebar. I am used to bar end shifters so like Sheldon, I decided to mount the Nexus shifter on the end of the drop bar. The shifter is built for a mountain bike bar (7/8 inch diameter) not a road bike bar (15/16 inch diameter). (I read that there are old drop handlebars that are 7/8 inch diameter but I could not find one.) I needed to adapt the diameter of the drop bar to mount the shifter. I had an old aluminum flag pole set that I was able to use. I used a flat file to reduce the diameter of the road bike drop bar just enough to slide on the aluminum pole transition joint. Then to make sure nothing moved I put in a pop rivet on each side. It may sound clunky but once I wrapped the bar you cannot tell there is a transition joint there. I am sure there are more elegant ways to do this but it works fine for me.
A note about the brake handles – your hybrid brakes are likely V-brakes also known as direct pull brakes. The cable pull on these is longer than most road bike brakes. Tektro makes a linear pull road bike brake handle set that has the necessary pull length for V-brakes. Another option is to use standard road bike brakes handles, with the linear pull adapter “wheel” multiplier.
If your hybrid has vertical dropouts, you will need to carefully choose your front sprocket size. I used one of the online sprocket calculators to determine that a 46 tooth front sprocket combined with the 21 tooth rear cog would be the closest fit. I still had to file about 1/10 on inch notch in the back of my drop outs to get the chain tension just right. This combination of gears gives me about a 1.15 gear ratio in the very lowest gear. This will get me up my 10% slope hill.
Regarding the vertical drop outs, the non-rotation washers supplied with the internal hub kit were all for horizontal drop outs. You will need the “8L (blue/green) non-slip washers for vertical drop outs.
One final tip, I used cable ties to secure the shifter cable. To ease dismounting the hub (such as to repair a flat tire) I used a Velcro closure for the tie closest to the hub on the chain stay.
I’ve been commuting to work (23 miles round trip) and am extremely pleased with the result. In an unexpected surprise, I find the angles and measurements of my hybrid conversion to be quite close to my beloved Surly LHT. Now, I have a great all-weather “rain bike” that has a familiar feel and handling characteristics.