Shimano SL-BS50 bar end shifter 6 spd adapter
 

Previous old post and new responses re: Shimano SL-BS 50 bar end shifters in Bicycle Mechanics this week revived an earlier search of mine. I am in search of this (see title) shim like adapter (Shimano Part #66C-1500)that allows the right indexed 7 speed bar end to be used as a 6 speed indexed. I have only seen this in Shimano late 80-90's small parts catalogue, and I did see it in a NOS Ebay offering some time back which was the whole SL-BS 50 pkg. The BM forum was responsive and indicated the part is dark grey and fits in the cable slot to reduce cable pull allowing the 6 speed shift. And is possibly 30 years old. Other than contacting Shimano (did 12/13/AM no joy discontinued in 2002)or posting to the C&V and Touring forums to see if there might be someone who knows something.I know can friction shift, but like the index option. Thanks in advance for any info.

Curious bump.

It’s a dark gray crescent shaped plastic bit that snaps into the cable groove to alter the cable pull. I have one (and only one) for the OP; sent pm.

How bout a pic?

[QUOTE=texaspandj;20052156]How bout a pic?[/QUOTE

https://farm5.staticflickr.com/4595/...383b26a5_z.jpg

^^^interesting, thanks.

before you send it out, is there any chance you can get accurate, well lit pictures of it next to a mm ruler? if it's easy enough, maybe it can be 3-D printed for people who would want it in the future (but seriously...it's 6 speeds. friction shift it.)

Sorry, too late on this end. I leave it to the new owner.

Fixed misspelling in thread title

Ultegra 7 speed DT shifters came with a similar part. It makes the shifter barrel bigger. It would not be that hard to make something like it out of copper wire.

I did the opposite and "respaced" a Sachs DT 8spd shifter to Shimano cog spacing by filing the cable slot deeper.

Thanks to all
 

Good morning,
My quest is complete. Many thanks to all who responded for their info, direction and help. Best.

FWIW, SiS 6-speed is my go-to system for my commuting bikes. I appreciate the robustness of the wide-spaced 6-speed layout, and being able to leave the shifting accuracy to SiS when I'm biking to and from work, day-in and day-out under all conditions, including my own state of mind (e.g. fatigued, sleepy, distracted, etc)
All my recreational bikes have friction shifting, well, because it's part of the fun when I'm riding recreationally. :)

Reviving this thread from the dead...

Calling on anyone who has this to take a picture of the bar end with the adapter in place. Also, could someone mic it for thickness? I like the idea of making one out of copper wire.

I posted an NOS set of SL-BS50 6/7 speeds shifter set on the for sale forum and mountaindave asked me if it had the 6 speed adapter clip (the purpose of this very thread). I looked it over quite carefully and didn't see one yet the bags seemed unopened. I did remove the actual shifter set from their bag but didn't disassemble them as I wanted to keep it unblemished.

Does anyone know if the adapter came already mounted within the shifter or did it come as a separate piece??

If anyone actually bought a set brand new with the adapter still in it, could you look at my photos and see if you recall where the adapter was stored?

My sale is here https://www.bikeforums.net/classic-v...d-barcons.html

I can’t say for sure but it sort of looks like it is sandwiched between the two shift levers.

Can someone explain how using this 6-speed adapter/limiter is different from simply using the limit screws on the rear derailleur to restrict cable travel? Is it simply extra insurance against the user attempting to shift further beyond 6 speeds?

The spacing of 6 and 7 speeds differ so the insert changes the amount of cable pull to suit.

Oh wow! My brain thought "it's probably more complicated than that", but then I've seen some bizarre contraptions that serve very trivial purposes.

I take it that the shim effectively changes the diameter of the shift lever cable track in order to mimic the cable pull of 6-speed cog spacing, correct?
In order to go from 5mm cog spacing to 5.5mm (10% increase), and assuming the length of cable pull is linearly proportional to the cog spacing, the shim will effectively increase the shift lever "cable wrap" radius by 10% as well. I can't imagine it's very difficult to measure that from existing levers.

The real challenge comes from trying to fabricate a shim (a), whose effective thickness when in position adds exactly 10% to the radius, and (b), stays in place over thousands of shift cycles. If someone decides to fabricate something like that (3-D printed or otherwise), I'd be in the market for one.

ps: might it be possible to achieve the same effect with the SL-BS64 8-speed shifters in order to use them with 7-speed? The increase from 4.8mm to 5mm is very slight at only 4.2%, which might pose a serious materials engineering challenge.

Thanks @WGB for this awesome photo of how the insert works!

https://cimg6.ibsrv.net/gimg/bikefor...d4a31e544e.jpg

the SL-6400 DownTube shift lever also used this same "C-clip" cable slot adapter. If I ever find a clean example in my stash (MIGHT happen) I will make exact detailed measurements so somebody can 3-D print them. it would be an easy part to duplicate that way.

I think you've got the idea, but you may now be overthinking it. ;)

The amount of cable pulled per shift is 2.9mm for 7-speed and 2.8mm for 8-speed, almost the same. Before pondering 3D-printed anything, try hooking it up and seeing if you can get it to index as-is. Rather than "a serious materials engineering challenge", I'd bet that a piece of tape wrapped around the barrel would be sufficient if you want to achieve the ideal cable pull. :)

You’re underestimating the thousands of man-hours spent by 3M employees developing that tape! 😁

Good idea about the tape though...