Downtube bosses - a unique arrangement?

[David9694]

Closer up

D374A67F-AC1F-4A33-82E6-3F910B7D2A93.jpeg (52.03 KiB) Viewed 639 times

Not seen this arrangement before - can anyone shed any light?

Bidding starting at £200 - I don’t think so!

[londonbikerider]

Timetrial frame with internal cable routing?

[stevegreen]

Suntour used to make a pair of downtube levers that were on the same bracket that bolted onto a boss brazed on the top of the downtube, similarly to the photo. But that was a long time ago....!

[Brucey]

I think it is a suntour 'symmetric' bracket onto which ergo bosses have been grafted.


IIRC these levers have an unfeasibly cunning mechanism inside them which adjusts the FD trim with every shift on the RD. More here including a photo of all the bits inside;

http://www.velobase.com/ViewComponent.aspx?ID=4cb7e658-e09e-4950-a283-2787beac2bb0
https://www.bikeforums.net/classic-vintage/514867-test-your-wits-suntour-symmetric-reassembly-challenge-pics.html

circa 1983 these were popular

cheers

[David9694]

I think it is a suntour 'symmetric' bracket onto which ergo bosses have been grafted.


IIRC these levers have an unfeasibly cunning mechanism inside them which adjusts the FD trim with every shift on the RD. More here including a photo of all the bits inside;

http://www.velobase.com/ViewComponent.aspx?ID=4cb7e658-e09e-4950-a283-2787beac2bb0
https://www.bikeforums.net/classic-vintage/514867-test-your-wits-suntour-symmetric-reassembly-challenge-pics.html

circa 1983 these were popular

cheers

Close, but no cigar. Apologies - I’ve edited the picture to give a better look on here than before - seems to be expecting brifters or similar.

[foxyrider]

whilst its been bodged to take Ergo/Sti adjusters, it originally did have a similar arrangement to Brucey's pic, part of the mid 80's aero fad - as others have said, quite common on pre tri-bar tt bikes of the day

[colin54]

Another not quite (?) on Shimano Dura-ace AX, originally part of SL-7321, closer to the shape on the Raleigh perhaps.
http://velobase.com/ViewComponent.aspx? ... 4abfaba7e7
Pictured on 1981 Lotus (Tsunoda) Super Pro Aero in this article.

http://www.ipernity.com/doc/286349/36249870

[Brucey]

SL-7311 is slightly different and has a curved base which fits to round tube (unlike SL-7321 which is shaped for aero tubes).

http://velobase.com/ViewComponent.aspx?ID=1d4a375f-f62a-4310-9f07-01ee42f346c4

I agree the shape of the top is more like the OP's picture though; thinking about it the clever mechanism in the Suntour levers can only work if the lever pivots are offset from the frame boss, so it can't be the suntour lever I pictured .

cheers

[colin54]

I wish I had your eye for detail Brucey !

[Trigger]

I think the 1987 Road Ace specifically had this 'on top' style fitting, before and after that it's back to the normal position. Shimano also did a 600ax aero groupset with the same 'on top' levers along with everything else that was smoothed out for that 80s aero fad.

The extremely rare Columbus Air teardrop tubing also had an 'on top' style braze on for downtube levers. Either that or you could just get your frame builder to put one on.



Seems they were before their time given how everyone has gone aero mad in the past couple of years!

[alexnharvey]

Bidding starting at £200 - I don’t think so!

I think you're misunderestimating the market.

[colin54]

Shimano Technical Document
https://si.shimano.com/pdfs/ev/EV-SL-73 ... -0443D.pdf

[David9694]

On the SL 7311 it’s the threaded axle component (14) that helps the arrangement the vendor has got to make some sense.

It’s an ‘80s fad, no longer made, but I’m struggling to see any weight or aero advantage here.

[David9694]

Bidding starting at £200 - I don’t think so!

I think you're misunderestimating the market.

He’s back on, relisted :

https://www.ebay.co.uk/i/264733080490

Mind you, a garage find Gran Sport went for £180 yesterday. I’d expect something rideable at that price. I just want to borrow one to get a colour match from.