madpogue 

Who knew? Both these bikes came with Suntour top mount shifters with braze-on mounts. Same year. First one is an '84 Miyata Seven Ten. Second one is an '84 Schwinn Le Tour.



A shifter mount for the first type will obviously not fit the second type of boss. Square peg in a round hole, literally. It looks like MAYBE a mount from the second type would fit the first type of boss.

Question is, why? The Miyata was no doubt a more expensive bike BITD than the Schwinn, so presumably it got a higher-end version of the shifters. So was it intentional not to allow someone to mount a higher-end shifter on the lower-end frame?

I guess it's obvious that my only option for the Schwinn, unless I do something drastic like round off the corners of the mount, would be to find a mount with a square cavity. I guess I'm just wondering what the rationale for this would have been.

noobinsf 

Symmetric shifters had the cam auto front trim mechanism, the second boss type.

RobbieTunes

I think the first one tended to twist, and counted on the concavity backwards tube-grabbing principle, which was less than satisfactory. So they went square. Then Klein really tossed a wrench into it.

Shoulda bought an Ironman.

madpogue 

Yeah, I think I see that in a pic of one for sale on the 'Bay. How well does that system work, BTW?

Yeah a square mount does make sense, in that regard.

Um, I did. In fact, the day I picked up the IM, the shop dude talked me into buying three old frames, including the LeTour.

noobinsf 

It's actually effective, and the shifters themselves are pretty smooth. If you come across a spare set of shifters, you can butcher them to make a cable stop and mount bar ends or brifters, and there is a thread on these forums to show how. The only drawback is that the mounting bolts for the shifters are hex bolts, not d-rings, so you have to have a tool with you to adjust tension lest they loosen.

79pmooney

I am pretty certain the Miyata is for a Superbe shifter, the Schwinn for the auto-trim. My custom has a boss for the Superbe. (It doesn't look quite like either because the builder simply made a titanium boss to fit the shifter I gave him. He didn't go on-line to see what it was "supposed" to look like. (It's been rock solid for 12 years so I'm not complaining.)

This isn't about Miyata and Schwinn, Each just built their bikes to accommodate what SunTour made. This is one of the very few times when I wonder "what was SunTour thinking when they designed those shifters to different mounts?

Edit: I've used both shifters. The auto-trims are sublime in feel. The front derailleur cable pull acts like the Simplex Retro (?- I never had thenm and forget what they are called) with the opposing spring in the lever. Very little pressure needed to shift in back. That is as nice as the auto-trim, The Superbes are just the finest straight friction sifters ever made.

Ben

seedsbelize 

I have a small collection of symmetric shifters. I'll have to dig them out and look at the mounts.

noobinsf 

Oh, and if you think you can mount Shimano top-mount shifters on the square boss... the Shimano square boss of the era has different dimensions, about a mm smaller on each side. I think these aero mount shifters simply didn't have the chance to mature and drift toward standardization since other ideas came along. They just petered out instead.

Miele Man

Shimano downtube side shifter brazeons were also different from Campagnolo and Suntour at one time and thus the shifters weren't interchangeable. On top ofthat the Shimano ones used a 4.5mm bolt instead of the more common 5mm bolt. Then Shimano finally got on board with what Campagnolo and Suntour were using.

Cheers

The Golden Boy 

Wasn't there also a top mount shifter boss that the shifters threaded into? it kind of looked like a Miyata rack eyelet- but where DT shifters would be.

madpogue 

Yeah, I knew it wasn't about the bike brand, that was just for context. I just posted because I had the same thought -- what were they thinking?

Interesting, thanks for the feedback (pun slightly intended).

cudak888 

Word to the wise about the Symmetric mounts (#2), especially on Schwinns: They weren't always brazed to the frame well. This problem is compounded as Schwinn did not drill the frame tubing below the boss. Any bolt substitution in excess of the factory Suntour length (the Suntour bolt may even be an issue) may bottom out on the frame, causing the braze-on to get pulled up as if it were being jacked up from the bottom, and possibly snap.

If I seriously considered keeping any frame with this sort of braze on, I'd drill a hole a few sizes smaller through the tube (being super careful not to nick the threads), then file it open until flush with the threads - at which point I'd then tap the whole thing, fairly confident that it wouldn't pop off during the tapping.

-Kurt

madpogue 

Picturing this .

79pmooney

Or - measure how deep the bolt hole is, shoulder to tube, then how long the bolt is. Maybe file a little bolt off if it is close. (I've never run into this and didn't know it until now. My Symmetric was on a clamp band and my Superbe is on a custom where the builder had it in his hand when he made the mount. (And it's welded titanium, I doubt its going anywhere.)

Ben

Last ride 76 

Having spent a looking afternoon last week figuring out that Suntour "endless band" friction shifters have some parts which make some of the shift levers not interchangable and on the aero version, even the bodies cannot be swapped without doing some "modification".


Perhaps a highly developed sense of irony was intrinsic to what made Suntour engineers so unique. Or perhaps it was Suntour's marketing department, frustrated with the way their brilliant engineers would create a marvelous product, and them add another layer of complexity, one only appreciated by fellow engineers.


SYMMETRIC Shifters? HA, HA... That was a long afternoon, I didn't get the final adjustments done in time for a test ride! All I wanted was to use the light and elegant 2 hole regular shifters on the rounded, less clunky looking, endless band, aero body (from which they had incidentally removed the word "symmetic"). No, then no again, not my second choice combination, then not the third either. Finally, "success" on itteration #4 .

Then all I had to do(realizing that if I didn't, when I went to use them next, I would have forgotten what went with what), was reassemble the others and put them away. At least this went smoothly, having become recently familliar with their differences,,,

cudak888 

I've had it happen happen once.

Notice that the square is brazed only on the left and right edges, not the center. The example above isn't even brazed up to each end.

-Kurt

Ex Pres 

Is this the one you're thinking of?
https://www.phred.org/~alex/pictures/bikes/shiftboss.jpg

The Golden Boy 

Yes!!!

noobinsf 

Hmm, I guess if I ever wanted to remove it...

cudak888 

I learned the hard way about involuntary removal of that specific braze-on.

-Kurt