drain holes in BB shells

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Brucey
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Re: drain holes in BB shells

Postby Brucey » 3 Feb 2017, 10:53am

there are loads of places it can get in. You can get condensation too.

Obviously conditions of use will cause variable results too. If there is no drain hole you can only be sure that you don't have a problem by careful inspection inside the frame. It isn't sufficient to check the BB shell BTW; water can sometimes get into the top tube and rot that out whilst the BB shell is still bone dry.

Condensation is fairly pernicious too. I recently came to realise that you can have a frame that looks bone dry inside and it can still have localised corrosion that has been caused by condensation. I think what happens is that condensation sometimes appears in the top of every tube that is closed. For example I have seen corrosion in the top of the down tube. This is rather worrying because it is one of the most highly stressed parts of a bike frame. The only way you will see that is with an endoscope/camera.

cheers
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mig
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Re: drain holes in BB shells

Postby mig » 3 Feb 2017, 11:10am

the drain hole in my BB shell is a clover leaf type affair. i didn't ask for it specifically with the frame builder but there it was on collection. still the thing barely gets damp outside - it may suffer from some condensation in winter as the temperature in the spare room where it lies isn't overly high.
i think the worst top tube rot i had was in a bike i used for TTs some years ago. i got soaked in sweat during races and rusted significantly despite attempts to slow that down. i'm sure being later pressed into turbo trainer service didn't help. i think that experience made me treat the innards of all other frames with some oil, waxoyl, ACF50 type stuff - whichever i had to hand on those occasions.

are drain holes less common in mass produced frames?

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Gattonero
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Re: drain holes in BB shells

Postby Gattonero » 3 Feb 2017, 2:17pm

Brucey wrote:there are loads of places it can get in. You can get condensation too.
..
Condensation is fairly pernicious too. I recently came to realise that you can have a frame that looks bone dry inside and it can still have localised corrosion that has been caused by condensation. I think what happens is that condensation sometimes appears in the top of every tube that is closed. For example I have seen corrosion in the top of the down tube. ...

cheers


OTOH, you ought to have a frame that has been built with adequate venting holes. Whether is fillet-brazed, TIG welded or (what a pain must be) lugged, the fumes build up inside the tube during the joining process (temperature and volatiles from Flux and rods), and you may not get a good penetration of the brass or the weld rod :?
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

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531colin
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Re: drain holes in BB shells

Postby 531colin » 3 Feb 2017, 3:06pm

Some bikes are stored outside; some in heated rooms indoors, some in sheds/garages.
Some have full mudguards and mudflaps, some no mudguards.
Some are used when the roads are salted, and some are not.
In a lugged and brazed frame, the tubes are traditionally all completely open into the bottom bracket shell, but they may be sealed or have just a small "blow hole" at the top and bottom head lugs and the seat lug.
TIG welded frames from the Far East may have small blow holes from chainstay to BB shell and into the back of the top tube, and much larger holes elsewhere.
Generalisations are therefore difficult, except to say that its better to keep water out than to provide drainage once the water has got in.....if you are going to ride without effective mudguards or store the bike outside, take all possible steps to stop the water getting in next to the seatpost and the bottom bracket bearing. (and into the headset bearing, come to that)
In more than half a century riding I have never had either a drain hole in the bottom bracket or a frame seriously damaged by rust. I cut up an "original" 531 frame I rode winter and summer for 35 years.....the most i found was superficial rust.

Threevok
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Re: drain holes in BB shells

Postby Threevok » 3 Feb 2017, 3:43pm

Anyone one know how Tange Prestige holds up against corrosion over time?

There are holes at the ends of the chainstays and one at the wishbone, but no BB drain hole

On side note - I always thought those holes on the BB shell were for attaching cable guides, for frames where the cable(s) run under the BB shell

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Mick F
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Re: drain holes in BB shells

Postby Mick F » 3 Feb 2017, 4:34pm

531colin wrote:Some bikes are stored outside; some in heated rooms indoors, some in sheds/garages.
Some have full mudguards and mudflaps, some no mudguards.
Some are used when the roads are salted, and some are not.
In a lugged and brazed frame, the tubes are traditionally all completely open into the bottom bracket shell, but they may be sealed or have just a small "blow hole" at the top and bottom head lugs and the seat lug.
TIG welded frames from the Far East may have small blow holes from chainstay to BB shell and into the back of the top tube, and much larger holes elsewhere.
Generalisations are therefore difficult, except to say that its better to keep water out than to provide drainage once the water has got in.....if you are going to ride without effective mudguards or store the bike outside, take all possible steps to stop the water getting in next to the seatpost and the bottom bracket bearing. (and into the headset bearing, come to that)
In more than half a century riding I have never had either a drain hole in the bottom bracket or a frame seriously damaged by rust. I cut up an "original" 531 frame I rode winter and summer for 35 years.....the most i found was superficial rust.
+1
Though never cut one up!

With my Mercian, there are no holes anywhere. No blow holes in the chainstays or the fork blades.
There is a small hole (1mm?) in the top of the head tube into the top tube, but that's all, and that is covered by the quill stem shaft.
The seatpin is a tight fit in the seat tube, so there's nowhere for water to get in.

AFAIK, the Moulton TSR has no holes anywhere.
Mick F. Cornwall

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CREPELLO
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Re: drain holes in BB shells

Postby CREPELLO » 3 Feb 2017, 4:57pm

If you run a bike without mudguards, then the chance of getting water up the plug hole must be increased. Fix this with epoxy putty by making a little mudguard positioned just in front of the drain hole Image

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531colin
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Re: drain holes in BB shells

Postby 531colin » 3 Feb 2017, 6:08pm

Mick F wrote:.........
There is a small hole (1mm?) in the top of the head tube into the top tube, but that's all, and that is covered by the quill stem shaft........


It isn't, you know...... :wink:

Chainstays will be completely open into the bracket shell, as will seat and down tubes.

I wonder how long this thread will run before somebody mentions pressure washers?....oops! there i go!

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Mick F
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Re: drain holes in BB shells

Postby Mick F » 3 Feb 2017, 8:30pm

I must say, that I haven't measured the quill stem insertion with respect to the top tube hole position.
However, I reckon I'm correct in saying the the small hole in the head tube into the top tube is covered by the quill.
I would stand corrected if I'm wrong of course.

The other end of the top tube is blank into the seat tube.

Other than that small hole in the head tube, there is no other way into the frame other than the BB ............ if you remove the BB bearing assembly.

Looking into the empty BB shell, you can see up the down tube, up the seat tube, and into both the chainstays.
No holes out except for the seat tube that is sealed by the seat pin.
No blow holes anywhere.
Mick F. Cornwall

Des49
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Re: drain holes in BB shells

Postby Des49 » 3 Feb 2017, 9:27pm

A couple of my bikes have these rather nice Cinelli "spoiler" BB shells, with rather a lot of slots in them.

I try not to hang the bikes up by their front wheels if back from a wet ride, leaving them to stand on their wheels for a while first. The blue bike (from 1990) has a sealed Chorus bottom bracket and has mudguards, while the 30 yr old green bike is my racing bike and just has a plastic sleeve to protect the open ball bearings, so does get a rebuild if used in a very wet event.
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Tiberius
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Re: drain holes in BB shells

Postby Tiberius » 3 Feb 2017, 10:58pm

......the whole thing is made 10 times worse by pressure washers.......





















I tried.....I really really tried.......But I couldn't resist........ :mrgreen:

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531colin
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Re: drain holes in BB shells

Postby 531colin » 3 Feb 2017, 11:19pm

Quill stem fits into the fork steerer.....if it fitted into the head tube, you couldn't steer..... :wink:

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Mick F
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Re: drain holes in BB shells

Postby Mick F » 4 Feb 2017, 9:33am

531colin wrote:Quill stem fits into the fork steerer.....if it fitted into the head tube, you couldn't steer..... :wink:
Of course!
Stupid me! :oops: :oops:
(slaps on the wrist)
Mick F. Cornwall

mig
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Re: drain holes in BB shells

Postby mig » 8 Feb 2017, 10:25am

re. water ingress in the bike generally.

would people say more is caused by the rain falling onto the bike? or by the water splashed up by the wheels?

Brucey
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Re: drain holes in BB shells

Postby Brucey » 8 Feb 2017, 10:47am

mig wrote:re. water ingress in the bike generally.

would people say more is caused by the rain falling onto the bike? or by the water splashed up by the wheels?


by volume the former, by destructive effect, perhaps the latter...?

cheers
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