General Cycling Discussion - Look at the pic and explain it to me please.

180791Hey all, not sure if this is the best place for this question but...
The image here is from the BD website. It just struck me as odd that there would be a hole in the bottom of the bottom bracket housing. What is the purpose?

Drainage.

I had considered that. But I don't think that my bike has a hole on the bottom, maybe it does and I've just never noticed it. Don't know if it's normal for bike frames to get water inside them, but it seems like a bad idea especially with a steel frame.

Decoration.

...it seems like a bad idea especially with a steel frame.

Leaving water trapped inside a steel frame also seems like a bad idea. Lesser of two evils, and you are correct, not all BB's have holes in them so yours may not.

Decorative drain.

Had a high-end Miyata roadster with such holes. Old-style fixed-and-adjustable-cup bottom brackets were much more susceptible to moisture than are modern sealed units. At best, they had that little plastic cover over the spindle.
Moisture can condense inside frame tubes, and these drain holes would let accumulated water either drain or evaporate.
They were never common, to my knowledge, so there must not have been a consensus that they were a good idea.

Never mind the hole. What kind of bike would put the cables, unprotected, around the bottom bracket like that? Are they sure the powder-coating is that wear-resistant? (And slick?)

3-leaf clover = somewhat lucky

Never mind the hole. What kind of bike would put the cables, unprotected, around the bottom bracket like that? Are they sure the powder-coating is that wear-resistant? (And slick?)

My Specialized globe sport disc has the cables like that.

Yeah, I saw the lack of plastic guide thingy too, and thought the same thing.

I think it's a government plot. Maybe something to do with reducing the consumption of iron ore and steel...

I pulled apart the bottom bracket of my old 3 speed once cause of a grinding sound it kept making. Found several dead bees in there. Maybe they would have survived that. lol.

It's a BD bike, right? That hole is a keyhole. If you find the magical key that fits it, it turns into a Cannondale.

180791Hey all, not sure if this is the best place for this question but...
The image here is from the BD website. It just struck me as odd that there would be a hole in the bottom of the bottom bracket housing. What is the purpose?

Condensate drain. All metal bikes will have water inside from condensate so it's a good idea to have a drain/vent to control rust/corrosion.

Never mind the hole. What kind of bike would put the cables, unprotected, around the bottom bracket like that? Are they sure the powder-coating is that wear-resistant? (And slick?)


thousands and thousands of great steel bikes run the cables like that.

alot of great frame builders have cutouts like that. I think the whole drainage think is a legand. it was likely done more to prevent rebranding frames.

get off your carbon and smell the steel once and awhile

http://www.bikeforums.net/attachment.php?attachmentid=180791&d=1291387287

So if my steel steed doesn't have a condensate hole, should I be worried? I live in Western Washington, it tends to run on the cold and wet side around these parts. I ride in the rain/mist regularly and store my bike in the house (warm/dryish) at night. Maybe I'll pull out my seat post and flip her over.

Oh man, there was no pun or innuendo intended in the last sentence of that last post...

So if my steel steed doesn't have a condensate hole, should I be worried? I live in Western Washington, it tends to run on the cold and wet side around these parts. I ride in the rain/mist regularly and store my bike in the house (warm/dryish) at night. Maybe I'll pull out my seat post and flip her over.

Hey! There's kids on this forum!

If you're really finicky, you could strip the bike and treat the inside of the frame with Framesaver (http://www.universalcycles.com/shopping/product_details.php?id=7824). FWIW: I just got finished reassembling a 20-year-old steel frame bike after having it powdercoated. Despite several years in the Pacific Northwet, everything inside was fine.

There are people who reccomend drilling a small ( 1/8" ) hole in the bottom bracket shell to allow for drainage.

Far better than holes in frames to allow drainage: Buy a TITANIUM FRAME bike! Planet Earth will rot away before a titanium bike rusts or corrodes.

Holes for drainage? You're kidding, of course. Any hole that would allow drainage would allow things to enter as well.

I can't believe that no one has suggested what is obvious: The cutout makes for a lighter bike. Weight settles to the lowest point in the frame: The bottom of the BB is the most effective spot to remove mass from.:)

I think there is supposed to be a hard plastic sleeve over the front derailleur cable to protect the paint... I could be wrong.

Brad

The cable routing is correct for this style of BB. No plastic or chromed metal guide is used. The guides are built into the cast shell. The paintwork does get worn away. I have this style on my Bob Jackson tourer.

Drainage holes in the BB are not only to prevent the frame from rusting. They also prevent the bottom bracket bearings from running in a water bath. Many of these classic designs were built when BB bearings were 1/4" cup and cone. They had a plastic protection sleeve but otherwise poor sealing.
Cartridge style BB units (eh Shimano) do not have any openings inside the shell so water would not affect them. There are some rebuildable cartridge bearing units that would be affected by running in a water bath. Their seals are not that good.
In practice, nothing gets into the shell and if it did, it would drain out.

I think it was more an artsy thing when the Italians were doing this on the Colnogos and DeRosa's. The also had some cutouts on the lugs with clovers and spades for looks. Also there were silicon sleeves that protected the bearings when for the cup and cone bottom brackets.

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.

Holes for drainage? You're kidding, of course. Any hole that would allow drainage would allow things to enter as well.

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.

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.


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.

file:///C:/Users/K/AppData/Local/Temp/moz-screenshot.pngfile:///C:/Users/K/AppData/Local/Temp/moz-screenshot-1.png181740

If Colnago does it, it MUST be brilliant.

http://www.bikeforums.net/attachment.php?attachmentid=181740&d=1292010911

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.php?attachmentid=180791&d=1291387287

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.

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?