The older style bikes ran with hollow seat posts with no seal at the top. OFTEN when riding in rain, the rear wheel would throw up water under the seat and it would wash down through the seat post... to the BB shell.

I've had it happen on various older bikes. The move to seat posts that are basically sealed where the seat clamp fits in has overcome some of this, but there are still other places where water can make its way into the frame, ostensibly through the headtube bearings.


The air relief holes used at the ends of the chainstays also can be a place where water can enter, especially as the rear wheel does throw up a fair bit.

There are issues other than the old style of cup-and-cone bearings not liking to run in a water/rust bath. If the threads on any type of BB (cup-and-cone, cartridge or external sealed) have not been properly prepped with a coating of grease (at least) or thread prep, rust will work its way through the threads and seize the lot together.

Where I come from, condensate is diesel fuel. Condesation is water formed from vapour in the air. If water cannot get into a bike frame, humidity-laden air is unlikely to get in there as well... so condensation is not really the issue.

Perhaps, but then it would drain out, gravity being what it is.

Rowan, excellent answer thank you. I can see the prudence in giving trapped water somewhere to go, but a hole that large could also let in the gritty, rain-with-snow-sand-water mix stuff that our local roads are covered with nowadays. Water is one thing, but all the grit I think would promote faster corrosion inside.
Thanks everyone for your replies.

I have a different idea.
Not drainage, but a convenient way to get oil into the BB before a race.
And the thread lock nut says "do not disassemble"
Just spray some teflon spray oil in there at the start of the race.
I really like that idea, I think it could win a race.

Air vent for the welding process? We would drill a small hole when welding on a sealed section of roll cage for a race car to stop air pressure build up, and ruining the last weld.

perhaps that could have been done 'back in the day' but the OP's bike have a uber fancy high tech sealed BB bearings. there would be no place for the oil to go

as discussed earlier this is something that was done on highend bikes for identifacation.

[IMG]file:///C:/Users/K/AppData/Local/Temp/moz-screenshot.png[/IMG][IMG]file:///C:/Users/K/AppData/Local/Temp/moz-screenshot-1.png[/IMG]http://bikeforums.net/attachment.php...hmentid=181740

If Colnago does it, it MUST be brilliant.

Those look like Hollowtech II cranks, they don't have a traditional bottom bracket, just two sets to sealed bearings that thread into the BB shell, I don't think moisture will really hurt them.


http://www.bikeforums.net/attachment...1&d=1291387287

Not likely. There are open ends to prevent pressure build up.

Personally I think it's a design flaw. Someone tried to get too fancy. I can maybe see a 1/16 inch drainage hole, but this thing is just inviting water and grit to get into the bearings.

I can tell you why I build bikes with a cut out in the BB. It's NOT to make it lighter, give it my trademark, allow bees to escape, hide my doobies, allow brazing gases to escape or anything like that. The holes are at the lowest part of the frame so that any moisture, whether it be from condensation or water entering from somewhere, can run down and out of the BB rain hole. There is no issue with stuff going in the other direction and getting into the hole because of the hole's location and the fact that if anything did get in it would of course get right back out again.

The reason the holes are often large, like the one pictured, is that when the bike is in motion it will cause a constant air flow through the frame to evaporate any moisture that was in the frame. Remember that there are breathing holes from all the main tubes into the other main tubes. On most frames the seat stays are sealed but the chainstays and all the other tubes are open in some way to one another. These openings do a very good job of allowing airflow from tip to tail on the bike. It's very rare that any quantity of water gets into a frame but condensation (sort of a light dew) is a constant on all frames and the airflow takes care of it.

BB drain holes have been used for a good 100 years now because they work very well. Its one reason why steel bikes can and do last a lifetime.

The cable running directly on the paint is something I'm not a huge fan of. I always use a teflon liner tube over the cable so it will be slippery and allow for the best shifting. I don't worry at all about the paint here as it will take a very long time for the cables to wear through - I just think it shifts poorly with the cable dragging on the paint.

The orange bike pictured looks like a Pegoretti. Does anyone know if it is?

That's all I got.

Dave

It's a Motobecane.

It is an escape portal--to insure that no evil spirits are trapped inside the frame.:eek:

Build detail .. needs you to take some of the Teflon-plastic cable housing
liner tube,
and run that thru those cable guides and run the wires thru those
Tubes , to lower friction.

the feature is part of a BB shell of better than run of the mill quality.
a throwback to friction shifting traditional bikes there It wasno issue lever pulled one way return spring pulled it back , that trifle of drag was not significant.

Indexing systems are fussy about friction in the cable run.

condensation happens.. thats why it needs a way out..

sorry to drag up an old thread, came across this while looking for something else, but I was installing a Campi Centur BB in an old Bianchi the other day. while skimming the direction I saw something that caught my eye. the directions actually call for a hole in the BB to drain water.

Thanks BG.

THAT hole is rather large for a drain, but the idea of a drain hole is a sound one.

Did a teardown/rebuilt on an old HT frame a few years ago, the water I POURED out of the BB shell was positively RANK!

a 1/8" hole is plenty......

I assume that with aluminum and titanium frames, holes in adjoining tubes must be placed, for venting the welding gas - argon gas in the case of titanium bikes - and circulating it while welding. My GT Xizang is all titanium, and I haven't found any holes open to the outside world - in the bottom bracket tube or anywhere else. And last summer I had a custom rear rack built of titanium tubing by Black Sheep Cycles in Ft. Collins Colorado. I don't see any holes open to the outside world at all. I assume all the tubes are still full of argon gas. Would that be the case?