TiHabanero

Any issues with putting bottle bosses in the center section of a down tube? This is the thinnest wall section of the tube. Does it make a difference? Going on a touring frame.

Andrew R Stewart 

Hopefully a touring frame isn't a stupid light .5mm wall... While I have seen and read of tube cracks at the DT bottle bosses the numbers are extremely small. My take is that as long as you do nice brazing, use silver filler, don't push the wall thickness thing too far, don't do heavy finish filing there should be no problems. I have mounted 1.5 liter cages (all be it with three bosses) on .6mm thick seat tubes also with no issues. For under DT bosses I use SS hour glass rack mounts acting as a stand off as well as a cage mount. The shift cables clear the cage/bottle (under BB routing) better and the DT has no holes drilled in it.

If you're a belt and suspenders guy the placed those star shaped reinforcements under the bosses. Just don't have the points really sharp... Andy

TiHabanero

True Temper RC2 tube with .6mm wall. Not a boss reinforcement guy, nor a brake bridge reinforcement or brake blade "stiffener" guy, either. More along straight up well built-functional frame type of guy.

unterhausen

bottle bosses take a lot of repetitive stress and I think it's worthwhile to put reinforcements on them. People have posted pics of busted bottle bosses that were not reinforced.

I don't use any other reinforcements.

But to the original question, I don't see how you can get the bosses on the butted section of the tube. Probably why most builders have used reinforcements.

dsaul

I don't see any way to get a functional bottle boss anywhere other than the thin section of the tube. I've never used reinforcements and I haven't had any problems, but I've only built 18 frames over the last 8 years.

Nessism

A reinforcement is not a decoration, although sometimes they perform a dual purpose. A reinforcement reduces stress in the frame, which is a good thing.

Andrew R Stewart 

But is it (a reinforcement) a needed addition? I suggest the test of real life says for other then stupid thin walls (.4mm and maybe .5 for some cases) bottle boss reinforcements is not "needed". There are LOTS of frames with .6mm walls that have seen many thousands of miles with no issues. The number that have had cracks is a very small number. Of course we never hear about the frames that don't crack so our perception is rather skewed by the reporting.

Of course this is loading dependent. A 225lb guy riding a few thousand miles of gravel a year with a Salsa Anything Cage loaded with 5lbs of tools might consider a .6mm wall kind of thin. A 140lb spinner who never ventures off smooth pavement and only uses 21oz water bottles might consider a .5 wall kind of thick. Andy

A note about decoration. Back in the day these little star like reinforcements (and even more so the curly ones found on Hetchins and the ilk) were only thought of as decorations. Again our perceptions change over the years. The vast majority of hand made frames of that era used .6mm walls, and many (likely most, being mostly Euro made) used brass for the filler. Again we didn't see any significant (perhaps even noticeable) number of cracked down tubes.

unterhausen

This is a weird hill to die on, people can do as they please. Maybe it's overkill, and there are plenty of bikes that survive without them just fine. I have seen broken frames that didn't have reinforcements. I ride on rough roads a lot and use large water bottles. I reject the notion that it is simply a decoration (not that there is anything wrong with that) or some kind of cover up for sloppy work. It's just good, solid, conservative framebuilding. Lots of people like avoid conservative practices with their builds, but I'm not one of those people. I guarantee with a full water bottle on a 9/6/9 tube without the reinforcement, the frame is flexing quite a bit side to side on a rough road. Best be very sure of your brazing and get a good fillet on the inside of the tube. For me, I'll take the minuscule hit on weight.

I have a set of 8/5/8 2OS tubing and it's really heavy. After Mike Reed's thread about getting thicker than advertised tubing, i went and measured, and my tubing is really 8/5/8. I somewhat regret buying that tubing because the frame is going to be heavier and probably stiffer than I want. I would have preferred 7/4/7 1OS tubing instead. I don't think that is a particularly thin tube to use in a frame, even for rough roads. I'm not sure anyone makes heavier than 9/6/9 any more, but I don't want frames that stiff or heavy. .6 and .4 are not really all that different as far as flex at the water bottle cage, they are both pretty thin. And I certainly am not going to use a heavy tube so it can carry a water bottle safely without a reinforcement at the boss.

Andrew R Stewart 

Eric- No deaths here. I'm comfy with my approach and understanding. Just wanting to add that to the discussion. I do try to do some qualifying to these types of things. We live in a shades of grey world with little hard edged drop offs (at least in frame building, riding is another topic) and I'm reluctant to place "must dos" or "have to or elses" when gaging the situation and more data is still needed. Hence my reference to how different riders and situations might see different solutions to the, otherwise, same tubing.

My reference to reinforcements being decorations was to be taken in the context of that past era. But I did extend the decisions made back then into the future with my comments of a lack of failures being common. Sorry if this was confusing. Andy

fietsbob

I built my light touring frame of 0.9mm wall Aelle , not butted, bottle bosses I got back then , came with 4 point stars, to btaze on with them,

those would be useful in reinforcing the thinner center in butted tubes.. which is likely why they included them..







...

TiHabanero

Thanks to all for the discussion. Since I have several bikes built from Reynolds 531 using 9 6 9 tubing it seems to be OK to place the bosses in the middle of the down tube. Never had a tube crack at a boss, so I am sure it will be just fine.