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Following up on the same bike as my previous question, we were able to get it cleaned up an running very well at the end of last summer.

Original bike Final bike

My brother has been riding it for a few months now and the main issue is that the SunTour friction shifter for the rear derailleur doesn't hold tension and frequently shifts to the smaller cogs on its own.

I bought a set of SunTour LePree downtube shifters to replace the shifter that's currently on the bike.

SunTour LePree shifters

I plan on installing a clamp with shift bosses like:

28.6 mm diameter clamp with shift bosses

However, there are no cable stops on the bike. The housing has been clamped like below and the shifter housing runs right up to the current shifter.

Cable housing clamp

The new shifter doesn't have a cable housing stop and so I'm considering using a clamp-on cable stop on the downtube closer to the bottom bracket.

Clamp-on cable stop

Am I on the right track or is there a better way?

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Back circa 1975, when the shift from stem to downtube shifters first started, it was pretty much the norm to have the shifters and the cable stops clamped to the (bossless) downtube. –  Daniel R Hicks Jan 9 '12 at 19:46
    
(But if your intent is to be "authentic" the clamps should be slightly corroded stamped steel, not neatly machined stainless.) –  Daniel R Hicks Jan 9 '12 at 19:49
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(Although on slightly fancier bikes they would forgo the cable housing almost entirely, and run the cable through a guide under the bottom bracket and then just have a housing about 8" long at the derailer.) –  Daniel R Hicks Jan 9 '12 at 19:53
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That seems like an awful big reach to the down tube. I seem to recall down tube shifters being more common on bikes with drop bars, short stems and short head tubes. –  Glenn Jan 9 '12 at 22:03
    
Yes for the drop bars. But I've seen them on some pretty tall bikes with long head tubes. –  Daniel R Hicks Jan 10 '12 at 1:40
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1 Answer

up vote 3 down vote accepted
+200

For downtube shifters, I prefer to run as little housing as possible. Your best bet is to look for some new old stock (NOS) vintage parts. You need two bits: a chainstay-clamping housing stop for the short housing loop to the rear derailleur, and a downtube-clamping cable guide for making the cable bend at the bottom bracket up towards the front derailleur and back towards the rear derailleur along the chainstay.

A quick search of eBay shows both available pretty readily. Several manufacturers make the chainstay clamp, but the Campagnolo 636 is representative. The best downtube clamp for both a front and rear derailleur looks to be the Campagnolo 626/A double guide, though Huret, Suntour and a few others also made them.

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That's actually a perfect solution. I picked up those two adapters and so we should be good. Thanks! –  fideli Jan 27 '12 at 16:27
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