Downtube shifter bosses, have they changed over time?

[fatboy]

I have recently fitted 7-speed Shimano 600 downtime shifters and they don't go fully home (so much so that I damaged the thread). I have taken the Dremel to the shoulders on the boss and this has improved it a bit but it's hardly ideal. This got me thinking if my shifters (eBay purchase) are funny ones or whether there was a change over time (the shifters are probably 80s or 90s and the frame is about a year old)?

[531colin]

There is a square bit of the downtube boss measuring just a shade bigger than 12mm square if my recollection is correct. The shiny washer thing has a matching square recess which (should!) fit this. This is the essential bit of the "fit". I don't think its changed ever. (There used to always be 2 flats on the top of the centre spigot, originally to fit friction downtube levers, these have been redundant for years I think.)
The shiny washer things have a curved face to fit the downtube, or a flat face if they are bar end levers.

[fatboy]

Doing some googling and found this image

It looks like I've got spacers for band on (i.e. 18 in the picture) rather than the downturn ones. Anyone know where I can get the correct spacers?

[Samuel D]

Is this what you’re looking for?

https://www.sjscycles.co.uk/gear-spares ... oy-frames/

That’s for SL-6400, if that’s what you have (you show an exploded view of a Dura-Ace part). I think there is another sort for frames with narrower down tubes.

[Brucey]

as noted by others the 12mm square base of the boss should fit into the shiny bezel piece. There are different types and thicknesses of shiny bezel piece including ones which work only with bar end levers, or bosses that are used on aluminium frames. Not all the swaps that you might think ought to work will do, and furthermore some bezels look very similar to others and yet won't work.

SL-6400 (downtube levers)
https://si.shimano.com/pdfs/ev/EV-SL-6400_6401-0845B.pdf

do need the flats on the centre part of the boss, for the LH lever.

Do be aware that if you start taking more than paint off the frame bosses (esp the 12nn square base), you may make it difficult or impossible to satisfactorily fit gear levers to the bosses subsequently.

Can you manage photos of the parts you are working with?

cheers

[nsew]

Above is the flat shaped base for fragile alu frames, bar end shifters & thumbie conversions. OP requires the standard curved down tube fitment. Pictured on right.

[nsew]

There were four different attachments for SL 6400 (from Velobase)

SL-6400-FCAI - Downtube Braze-On A-Type / M5
SL-6400-FCBI - Downtube Top Mount Braze-On B-Type
SL-6400-BCAI - Band A-Type
SL-6400-FAI - Downtube Braze-On A-Type / M4.5

A modern bike should have standard (FCAI) bosses. It’s not uncommon for used levers to be messed with. There’s a tiny internal spring in the 6400 front lever that if you’re lucky enough to find after it pops out, is reportedly stupidly difficult to install. I dont think 8sp upwards had this. So don’t open up. Rear of shifters should be identical to these, notice the differing front and rear internals. If all is well then you just need to locate the curved bases which are identical.

[Brucey]

….. It’s not uncommon for used levers to be messed with....

understatement of the century...?....

cheers

[fatboy]

Ordered some Sundance ones for 11 quid!

[Brucey]

Ordered some Sundance ones for 11 quid!

SunRace….?

cheers

[fatboy]

Ordered some Sundance ones for 11 quid!

SunRace….?

cheers

Bloody auto correct!

[Gattonero]

Back in the day there used to be a specific reamer for the round part of the boss where the shifter lever would fit. The height of the round part can vary, I've seen this many times and had to file down and carefully re-tap to make sure the shifter would stay in place correctly. This would be very important on friction shifters.