Downtube pip

[Mac_Mwnci]

Re:

I've decide to pose the question directly to Bob Jackson, after all they should know 100% right? I'll update on here once I have a reply (regretting not having bosses brazed onto the frame now...)

 

[Mac_Mwnci]

Re: Re:

It looks to be pretty central. Just as I finish tightening the left side lifts a little. BTW, I usually tighten parts like this by feel, but recently bought a torque wrench (for one of my other bikes, a Croix De Fer 30). According to the Shimano docs, band-on mechs should be tightened to 5-7 N-m :shock: This feels like a lot when torquing so I'm so for 4 N-m. Any opinions?

The issue isn't whether it's central or not, it's whether it will stop the band sliding down the tube when the cables are tensioned, especially if something goes wrong and you put more tension on the cables than you would in normal shifting, i.e. pressing hard at the end of travel, or if something gets stuck. When that happens the band can jump over the "pip" and make a mess. If the band is not flush against the pip you are asking for trouble, IMO.

I suppose a cable stop is under less stress than a pair of band-on shifters, but saying that I have had similar problems with similar stops sliding down the tube on hub gear setups... and having had problems before I always make sure this sort of thing is done up TIGHT.

That's my experience, but it's your bike. If it were me I'd think about flipping it 180 degrees and having the bolt at the top. Or even better use this sort of thing, much more secure, if a little modern looking:

https://www.ebay.co.uk/itm/On-Frame-Cab ... SwSQFaQ2-9

Yes, I think it'd be better if the pip were on the top side of the downtube, like the one in your pic earlier. I've actually got one of those modern clamps, unused, somewhere, they just don't look that nice and you can't add the Shimano barrel adjusters to them either. Same for flipping it: it would look pretty awful, in my opinion.

"I suppose a cable stop is under less stress than a pair of band-on shifters"


Agreed.

How tight is 'tight' though? That's the question.

 

[Captain Stupido]

Re: Re:

How tight is 'tight' though? That's the question.

When it's tight, it's tight. I'd say that as long as you don't strip the thread or chew up the head, it won't be too tight. Personally I think marking the paint is probably unavoidable and would second comments re not bothering with PVC tape - it will help things to slip about and also can take paint with it anyway when it's ultimately removed.

 

[Mac_Mwnci]

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ok..so I've just slackened both fitted gear cables now coz I've got the absolute fear and I'm pondering whether to even go on with the project :? Is this why band-ons were superseded then? I mean, if it's that risky?

Let's see what Bob Jackson have to say tomorrow...

 

[Midlife]

Band ons were real popular in the 70's as there was a fad for no braze ons. My 70's Falcon San Remo has none! If the band on was tight nothing moved, a little pip was icing on the cake

 

[Mac_Mwnci]

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Had a very quick reply from Bob Jackson and they've stated that the band-on's been fitted 'perfectly'. Good news! I can carry on with my build now

 

[Captain Stupido]

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Excellent. Apologies if I amplified your worry unnecessarily.

 

[Mac_Mwnci]

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Not at all! I can understand from your past experience that you'd want to be 100% certain a band-on doesn't slip. Me as well, which is why I posted the question. It's always great to get some advice on here. I feel I can go on with the project now. Even though the differing opinions are always valid I'm happy that Bob Jackson's advice will be spot on in this instance