SRAM road bike shifter to mountain bike derailleur parts

thingiverse

This is a new gear ratchet and cable spool for SRAM road bike shifters. It is designed to shift a mountain bike derailleur and 11-speed cassette. It has been tested with an 11-speed SLX derailleur with a Sunrace 11-speed cassette. The cable spool can probably be resized to shift a 12-speed or even 13-speed cassette, but I do not have the proper parts to test that. Shifting works well with the derailleur clutch disengaged, but not so well with it engaged. The setup can use more refining- replacing the cable housing and using high quality cable can probably improve the shifting. I have included two diameter spools, and honestly, I forget which I have on my bike now. You can also change the diameter in Fusion 360 file. I apologize for what a mess the file is, it's been development for more than a year. Both diameters have a kludge version where I compensated for my 3D printer making the insides of holes too small. The non-kludge versions have no correction. I have also included two different gear ratchets. One is flat on the bottom which lends itself better to 3D printing. No, you don't want to print it in plastic, but even some metal 3D printing processes work better with flat bottomed parts. The version with the endstop- not the flat bottom- is more designed for multi axis milling, but the endstop might be slightly off at the wrong angle. If worse comes to worse, you either have to file it down a bit, completely remove it, or deal with the extra bit of stroke shifting from the highest gear. The gear ratchets are provided as both .STL files and .STEP because most metal 3D printing or milling places will prefer the .STEP over .STL. One obvious weird feature of the gear ratchets is that there are two rows of gear teeth. One is offset from the other by one degree. This is to get that extra little bit of travel with the existing pawls in the shifter. That may not be so important for 12 speed, but it makes 11-speed shifting possible, though 10-speed needs even more cable travel. This design also allows a little bit of overshift when shifting to lower gears. This is helpful because stiction causes a bit of sloppiness. Even with this built in overshift, it may still be useful to overshift by pushing the lever an extra few degrees to make sure the chain completes its shift. An obvious weird feature of the cable spool (yeah, I sometimes refer to it as a pulley too) is that the cable port is much lower than the stock part. This allows the cable spool and gear ratchet to turn farther than they would otherwise be able to. This is how it is able to with with the longer cable pull of mountain bike derailleurs. This is also designed for 12 or even 13 speeds by simply replacing the cable spool since it is easier to make that part home. If I did not make it clear, the cable spool can be made on most home 3D printers. The gear ratchet more likely needs to be made of steel, most likely by some professional vendor. Metal 3D printing is less expensive for just one or two parts, but it has poorer tolerances and the surface finish might not be all that kind to the pawls sliding against it. CNC milling is more expensive, but some Asian vendors have relatively reasonable rates that get more economical when buying more than just one piece. If getting the gear ratchet CNC milled, normal medium tolerance is good enough, except the center hole should be higher tolerance for a good fit on the center shaft- 4mm +0.03/-0mm. Directions for disassembling SRAM shifters can be found online, or some of my other projects have brief overviews.