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Type A vs. Type B Down Tube Shifter braze-on bosses

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Type A vs. Type B Down Tube Shifter braze-on bosses

Old 09-16-23, 03:42 PM
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Type A vs. Type B Down Tube Shifter braze-on bosses

I have been trying to find a simple photo that can be easily used to identify the difference between a Type A and Type B braze-on.

in addition, A uses a 5mm screw while a B uses the narrower, uncommon 4.5mm screw.

Note: top frame is Type B, bottom is Type A

I hope this helps




Last edited by Het Volk; 09-17-23 at 10:36 AM.
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Old 09-17-23, 01:19 AM
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All I know is that the red frame's Type A shifter doesn't play well with others and is on a Schwinn Voyageur circa 1984-1985, which is a big reason why I didn't buy such a frame recently (didn't want to bother filing things).
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Old 09-17-23, 10:36 AM
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Originally Posted by RiddleOfSteel
All I know is that the red frame's Type A shifter doesn't play well with others and is on a Schwinn Voyageur circa 1984-1985, which is a big reason why I didn't buy such a frame recently (didn't want to bother filing things).

I am going to make an edit because the Top frame is a Type B while the bottom is Type A
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Old 09-17-23, 10:56 AM
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Wait, which is which? Video says 'Type A' but shows the one on top (maybe that is just an unintentionally misleading still frame), whereas you mention the top one (red frame) being type B. But thank you, didn't even know different types existed. So the goofy, non-square one is type B?
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Old 09-18-23, 11:36 AM
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Originally Posted by AdventureManCO
Wait, which is which? Video says 'Type A' but shows the one on top (maybe that is just an unintentionally misleading still frame), whereas you mention the top one (red frame) being type B. But thank you, didn't even know different types existed. So the goofy, non-square one is type B?
Yes. Top one is the Shimano Type B which was I guess, done for certain early 80s bikes using specific Shimano group sets.

The bottom frame is the more common Type A.
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Old 09-18-23, 05:59 PM
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Originally Posted by Vintage_Cyclist
A commonly posted issue. There are multiple threads about this, with solutions ranging from hunting down the parts, modifying the keyhole shaped mounts and threading, and converting to brifter or bar-end shifters. I did the latter with my 85 Centurion Ironman.

Here's a list of related threads:

Modification: Old style Shimano downtube shifter mounts to later style - Bike Forums

Shimano 600 shift lever woes on a Centurion - Bike Forums

Do I have "B" Style Shifter Bosses? - Page 2 - Bike Forums

Shimano 4.5mm Type-A Shifters / Downtube Braze-ons - What are my options? - Bike Forums

Help Me Out With Shifter Boss Covers on This Miiyata 912 - Bike Forums

cable stops for unusual downtube brazeons - Bike Forums

Downtube shifter boss compatibility - Bike Forums

https://simplicityvintagecycles.com/2...aga-continues/

There's an online vendor called Loose Screws, which used to be bike oriented, but has shifted to firearms. They still have old bike stuff for sale though, including stuff that might work for you.

Shimano Dura Ace 4.5mm Downtube Shifter Screw w/D-ring - I used these to get cable stops on my shifter mounts, for use with bar end shifters. I removed the D-rings by putting the screws upside down in a vice and tapping them with a hammer to pop-off the D-rings. Having the screws is half the battle. These are them.

Shimano Z-401 Friction Downtube Shifter Set - can't vouch for these and the description incorrectly describes them as "Italian type", which they're not.

Shimano Dura Ace EX Downtube Friction Shifters Set - another bad description, but looks suspiciously like the correct shifters.
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Old 09-22-23, 05:08 AM
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These can be handy: https://www.mcmaster.com/products/sc...ead-size~m4-5/
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Old 10-07-23, 05:19 PM
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Type A components (Shimano Z series)




Last edited by brewerkz; 10-07-23 at 05:38 PM.
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Old 10-08-23, 08:17 AM
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Originally Posted by Het Volk
I have been trying to find a simple photo that can be easily used to identify the difference between a Type A and Type B braze-on.

in addition, A uses a 5mm screw while a B uses the narrower, uncommon 4.5mm screw.

Note: top frame is Type B, bottom is Type A

I hope this helps



RJ the Bike Guy - Shimano Type B shifter boss
I have a recently acquired Cilo frame with the type B bosses and the links posted above were very helpful. I think I am going to modify cable stops since I want to use handlebar mounted shifters but Im still deciding between bar-ends or brifters. Either way, I need cable stops.

If one chooses to stick with downtube shifters, the only 3 options are clamp-on shifters (aesthetically unpleasant to my eyes) or the other 2 varieties you can find in the links above which are specific to these bosses.

The most extreme but effective solution is having the more common bosses brazed on but that would involve refinishing the frame.
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Old 10-08-23, 09:53 AM
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Originally Posted by Het Volk
I have been trying to find a simple photo that can be easily used to identify the difference between a Type A and Type B braze-on.

in addition, A uses a 5mm screw while a B uses the narrower, uncommon 4.5mm screw.

Note: top frame is Type B, bottom is Type A

I hope this helps



RJ the Bike Guy - Shimano Type B shifter boss
No, the one on top is an "A-type" boss; the one on the bottom is a Campagnolo-type boss. "B-type" bosses are completely different:
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Old 10-08-23, 02:36 PM
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I guess I was in error. I read the round bosses were the B and the normal/ Campy bosses were A.

I dont internet well
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Old 10-08-23, 03:43 PM
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The Campagnolo style of boss dates back to 1953, I have an Italian frame that had them as original.
they were not used frequently.
I also have an Ideor that employs them. It dates from 1958.

Braze-ons were an active argument regarding frame strength and durability for a long time.
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