Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

Downtube shifter bosses with small square - Possible to mount indexed DT shifters?

Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

Downtube shifter bosses with small square - Possible to mount indexed DT shifters?

Old 07-25-18, 03:26 AM
  #1  
TallRider
Senior Member
Thread Starter
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,454
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 128 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
Downtube shifter bosses with small square - Possible to mount indexed DT shifters?

I'm building up a 1981 Nishiki International as a vintage-y allroad bike. 33mm 700c tires with fenders.
Was planning Shimano indexed downtube shifters for initial build. But turns out the shifter bosses differ from standard (edit: Type A) shifter bosses. The bosses are very similar, with the same diameter (~9mm) and thickness of the flattened section (~6mm).
But the raised square at the base of the shifter boss is a different size. On standard type-A shifter bosses, that is 12.2mm square. On this Nishiki, the base is 10.2mm square, and also doesn't stick out quite as far from the frame. The boss takes 5mm screws (like standard type-A bosses, but with slightly different threading pitch), not 4.5mm screws like the Shimano type-B.

edit: Note that this is different from the type-B shifter bosses that Shimano used in the early 1980s - those had a curved base and a tab toward the front.
These bosses came with Suntour friction shifters, and are probably Suntour bosses. That would have been a better subject-line term.

The only ways I can think of to mount Shimano indexed downtube shifters are
a) find some holy grail curved baseplate designed to seat on these bosses. I doubt this was ever made.
b) use clamp-on DT shifters and leave these bosses hanging out ugly and naked.
c) use Suntour power rachet shifters that match/fit the bosses. Not indexed, but easier to use than traditional friction.

The better solution is probably just use bar-end shifters, as I was considering anyway. I'd need to find an appropriately-threaded screw to hold cable stops on.

The following photos show a standard shifter boss with 12.2mm square, and odd shifter boss on the Nishiki with 10.2mm square, and the original friction shifters that came on the Nishiki.




Last edited by TallRider; 07-25-18 at 12:53 PM.
TallRider is offline  
Old 07-25-18, 04:11 AM
  #2  
CycleryNorth81
Senior Member
 
Join Date: Jun 2014
Posts: 877

Bikes: custom Cyclery North (Chicago), Schwinn Circuit

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 350 Post(s)
Liked 202 Times in 117 Posts
Maybe this link will help:
Shimano A Type boss coversion index shifters
CycleryNorth81 is offline  
Old 07-25-18, 05:10 AM
  #3  
rccardr 
aka: Dr. Cannondale
 
rccardr's Avatar
 
Join Date: Jul 2009
Posts: 6,539

Bikes: Lots. Just...lots.

Mentioned: 184 Post(s)
Tagged: 0 Thread(s)
Quoted: 1555 Post(s)
Liked 1,002 Times in 468 Posts
1) Cut a narrow 1mm thick shim and glue it to the four sides of the square mount = 12.2 mm base. Try a hobby shop for flat stock of the correct thickness.
2) Tap the existing threads to 5mm using a bottoming tap.
__________________
Hard at work in the Secret Underground Laboratory...
rccardr is offline  
Old 07-25-18, 01:23 PM
  #4  
TallRider
Senior Member
Thread Starter
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,454
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 128 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
Originally Posted by CycleryNorth81 View Post
Thanks. I've worked with the Shimano type-B shifter bosses before (curved base and tab pointing toward the head tube). I was repainting the frame, so I ground down the boss (careful to avoid the tube) so that a typical downtube cable stop would fit over them, and then just affixed them with a 4.5mm screw. Reading these helped me get the terminology of Type A and Type B (and their histories) correct.

These bosses on this Nishiki are different. More visually similar to Campy type-A standard. I edited my original post to include proper terminology.

These bosses came with Suntour friction shifters, and are probably Suntour bosses. They match the mounting structure for some Suntour stem shifters that I have sitting around, too. I could also use Suntour power rachet (non-indexed) downtube shifters.

I could only find two threads where it appears someone is dealing with Suntour type of shifter boss, and there's nothing systematic contained in either thread. Thread 1. Thread 2.

This thread is limited by the lack of clarity in my subject line, because I didn't know how to describe the bosses when I wrote this. If discussion doesn't take off here, I may write another post later about Suntour shifter boss standard.

Originally Posted by rccardr View Post
1) Cut a narrow 1mm thick shim and glue it to the four sides of the square mount = 12.2 mm base. Try a hobby shop for flat stock of the correct thickness.
2) Tap the existing threads to 5mm using a bottoming tap.
The shim might help, but I don't think it would work to tap 5mm threads over to a slightly different 5mm thread pitch. Tapping 4.5mm threads (for Shimano type-B bosses) to 5mm would probably work because you'd be widening the hole in the process, but there's no extra material to wrk with in this case. But I can just use the bolts that came with these suntour shifters (or find something matching at a hardware store).

Last edited by TallRider; 07-25-18 at 01:29 PM.
TallRider is offline  
Old 07-25-18, 01:37 PM
  #5  
Mr. Spadoni 
Senior Member
 
Join Date: Jan 2015
Posts: 556
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 208 Post(s)
Liked 124 Times in 71 Posts
Would it be poor form to ask about your plans for the friction levers that you are removing ? Not sure of the etiquette on matters like this.
Mr. Spadoni is offline  
Old 07-25-18, 02:51 PM
  #6  
gugie 
Bike Butcher of Portland
 
gugie's Avatar
 
Join Date: Jul 2014
Location: Portland, OR
Posts: 9,471

Bikes: It's complicated.

Mentioned: 1033 Post(s)
Tagged: 0 Thread(s)
Quoted: 3409 Post(s)
Liked 1,916 Times in 938 Posts
Originally Posted by Mr. Spadoni View Post
Would it be poor form to ask about your plans for the friction levers that you are removing ? Not sure of the etiquette on matters like this.
I think the etiquette would be a PM to the OP.

(Private Message to the Original Poster)
__________________
If someone tells you that you have enough bicycles and you don't need any more, stop talking to them. You don't need that kind of negativity in your life.
gugie is offline  
Old 07-25-18, 06:03 PM
  #7  
Mr. Spadoni 
Senior Member
 
Join Date: Jan 2015
Posts: 556
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 208 Post(s)
Liked 124 Times in 71 Posts
Originally Posted by gugie View Post
I think the etiquette would be a PM to the OP.

(Private Message to the Original Poster)
Thank you. The feedback is appreciated. If only Emily Post had your skills with a torch.......
Mr. Spadoni is offline  
Old 07-25-18, 10:55 PM
  #8  
CycleryNorth81
Senior Member
 
Join Date: Jun 2014
Posts: 877

Bikes: custom Cyclery North (Chicago), Schwinn Circuit

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 350 Post(s)
Liked 202 Times in 117 Posts
Originally Posted by Mr. Spadoni View Post


Thank you. The feedback is appreciated. If only Emily Post had your skills with a torch.......
+10
CycleryNorth81 is offline  
Old 07-27-18, 11:37 AM
  #9  
madpogue 
Senior Member
 
Join Date: Jan 2004
Location: Madison, WI USA
Posts: 5,495
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1802 Post(s)
Liked 848 Times in 642 Posts
Originally Posted by Mr. Spadoni View Post
Thank you. The feedback is appreciated. If only Emily Post had your skills with a torch.......
How do you know she doesn't?......
madpogue is offline  
Old 07-27-18, 07:50 PM
  #10  
Reynolds 531
Senior Member
 
Join Date: Oct 2014
Location: Reno nevada
Posts: 483

Bikes: 4 Old school BMX, 6 Klunkers, 5 29er race bikes, 4 restored Sting Rays, Now 3 vintage steel bike being built up

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 216 Post(s)
Liked 70 Times in 43 Posts
This is what 3d printing is for. You may even know somebody who has one.
Reynolds 531 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
spacelahana
Classic & Vintage
5
02-16-19 12:36 PM
DIMcyclist
Classic & Vintage
2
02-21-18 08:30 AM
vtchuck
Classic & Vintage
1
06-12-17 09:11 PM
r0ckh0und
Classic & Vintage
12
12-15-14 06:56 PM
OldRoadman
Classic & Vintage
1
03-13-10 06:42 PM

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.