Classic & Vintage - older dt-shifter braze-on - work with indexed dt shifters? (pictures)

I've got a Centurion TA Comp (http://www.unc.edu/~cupery/pics/bikes/Centurion_TA_Comp_frame/) from 1984, and am getting it sandblasted and repainted soon. The downtube shifter braze-ons are different than I've seen on any other bike, having a "stop" built into them rather than being part of the curved-spacer piece that sits between the frame and the shifter.
I think this precludes the use of indexed down-tube shift levers with this frame, because the right (rear) indexed shift lever requires a spacer that can't fit over the braze-on of the TA Comp. The bike came with Shimano 600 components including pure-friction (no racheting) down-tube shift levers, that worked perfectly well with the brazed-on shifter mounts on the frame.

I'm guessing that I can't use indexed down-tube shifters with the braze-on mounts on the TA Comp. No biggie - I'd probably have planned to use bar-end shifters even if the down-tube mounts were normal. But it's nice to know one's options.

Some pictures:
1) a normal down-tube shifter braze-on, without the curved spacer.
2) normal braze-on with the curved spacer from Shimano indexed down-tube shifters
3, 4) TA Comp braze-on
5) TA Comp braze-on with aluminum spacer press-fit over the braze-on.

http://www.unc.edu/~cupery/pics/bike_parts/IMG_7112--dt_boss.jpg
http://www.unc.edu/~cupery/pics/bike_parts/IMG_7114--dt_boss_with_spacer.jpg
http://www.unc.edu/~cupery/pics/bike_parts/IMG_6852--weird_shifter_braze-on.jpg
http://www.unc.edu/~cupery/pics/bike_parts/IMG_6853--weird_shifter_braze-on.jpg
http://www.unc.edu/~cupery/pics/bike_parts/IMG_6834--old_dt_shift_spacer.jpg

Tim,
Since you are having the frame stripped and repainted any chance of having old brazed ons
removed and new ones (standard) brazed on?

IIWM, I'd try a Shimano index shift lever without the curved spacer on that TA. It looks as if the built-in stop is in the right place to work.
Top

Well, the place doing the repaint has expereince painting bikes but isn't a frame shop. They may have the capacity to remove the current braze-on on the TA Comp, but I highly doubt they'd have the capacity to braze a new one on, let alone getting ahold of a new one. Maybe if I got ahold of "standard" bosses they could braze them on for me.
A Shimano indxed lever won't work because in order to index, it requires the toothed interface visible in the second (pink bike) photo, and you can't get that interface if you can't put the curved spacer over the boss because it's that that integrated stop on the front. I guess the dt bosses on the TA Comp were designed to be an elegant solution, but were thought of prior to the advent of indexed shifting. I'll probably just use barcons on the bike.

IIWM, I'd try a Shimano index shift lever without the curved spacer on that TA. It looks as if the built-in stop is in the right place to work.
Top

He can't use indexed with that setup - note that the 6 tabs/holes on the inner circle of the standard Shimano boss are absent on the second frame.

He's pretty much stuck using Shimano friction or the racheting Shimano Light Action friction shifters, as the indexed ones will not sit right without those 6 tabs.

-Kurt

Ah, shimano 600 braze-ons, those piss me off. I have one bike still with those and I did a bit of dremel grinding to get the tab off and lightly square the other sides so I can get the adapters on to use bar mounted shifter. Looks crude but the bike was nothing special and I could always have the braze ons removed and proper ones mounted down the road.

Ah, shimano 600 braze-ons, those piss me off. I have one bike still with those and I did a bit of dremel grinding to get the tab off and lightly square the other sides so I can get the adapters on to use bar mounted shifter. Looks crude but the bike was nothing special and I could always have the braze ons removed and proper ones mounted down the road.
That's a really good point - I need to grind these down before I get the bike repainted, so that I can at least mount the down-tube cable stops.

Are you saying these braze-ons were specific to Shimano 600 friction shifters?

Crap! My Christmas break project is stripping a Centurion Elite RS for powdercoating. Time to add the expense for removing the Shimano 600 bosses and brazing on the new ordinary ones.

My '83 Centurion Pro Tour has a Suntour Symmetrix-specific mount on the downtube for the shifters, it's not even close to anything I've seen before as far as downtube shifter bosses. I've heard both good and bad about the Symmetrix shifters, I'm going to give them a try and if I don't like them, like you, I'll just use bar ends-

That's a really good point - I need to grind these down before I get the bike repainted, so that I can at least mount the down-tube cable stops.

Are you saying these braze-ons were specific to Shimano 600 friction shifters?

The only bikes I have ever seen these on are shimano 600 equipped bikes (I have had 3). The arabesque shifters as well as the later mid 80s ones which appears to be what you have.

The only bikes I have ever seen these on are shimano 600 equipped bikes (I have had 3). The arabesque shifters as well as the later mid 80s ones which appears to be what you have.

Shimano Light Action racheting friction are also compatible with his shifter bosses.

When it comes to friction shifters, these racheting Light Actions are the best deal I've seen out there for the price. Feels different from Simplex Retrofriction, but uniquely nice to the touch all the same.

-Kurt

Okay, here's the deal: the place that's doing the sandblasting and powdercoating is going to grind down the shifter braze-on (both the forward tab and that lower, wider-radius bit) so that a downtube cable stop (designed to bolt into standard dt-shifter braze-ons) will fit over it, flush against the tube.
It's possible that in the process of grinding it away, the brazed-on piece will fall off (because the brazing material itself may be concentrated toward the outside of the interface between shifter mount and downtube) and if that happens the place will just sand the tube down so it's smooth before painting, and I'll use a clamp-on downtube cable stop.

That would have been my solution, but I wouldn't trust anyone else to do it. I'd do it myself, but that's just me and I have the tools. Good luck!