Bicycle Mechanics - Why do frame builders do this?

http://www.yellowjersey.org/ynaga7.jpg

to prevent overheating of the bottom bracket

LOL j/k

It lets condensation drip out.

I haven't seen that done since the '80's. Back then they were drilling out everything they could in an effort to save weight. Should've just put down that 4th slice of pizza!

L8R

My GOD MAN, that is a least 4 grams worth of machining!

What's wrong with you? :p

Nagasawa?
Weight, moisture, and it looks real purty.

It lets condensation drip out.

Hmm.. Was this a climate specific concern in passed days?

Nagasawa?

Yes, you are correct.

Depends on the builder. Some put their "trademark" on the frame, i.e. clover, heart, etc. I think it looks great and adds a clear touch of class. Probably hell on the bearings if you ride in the rain much, but still it gives it soul.

Dave

I wouldn't think that it would be a good place to have cut out, I have all kinds of dust and dirt flying up in that area, even on a dry summer day, probably wreck bearings in a hurry.

They do it so that you cannot lie to your friends about having the lightest and most expensive titanium bottom bracket made. Everyone will know that you are running a UN-52. LOL.

I think it was done, as MichaelW says, to let the condensation out. Back in the day, Campy used to sell a plastic sleeve that covered the BB to reduce the amount of moisture, dirt, and grit that collected in the BB shell area.

I really have no clue what so ever, Im thinking along the lines of custom building, and design. And I also think dirt would get in in a FLASH. CrAzY :p

Its to let moisture and water out. Custom frame builders figured as long as they were making drainage holes we might as well cut it to look like our trademark. Surprisingly if you use the plastic sleeve that comes with the frame/bottom bracket the bearings stay relatively clean. Without the sleeve its pure torture on the BB. I've pulled out BB's on frames that werent cut out and water would run, not drip, out of the BB shell. We regularly drilled them out.

Colnagos have/had pretty cool 'clover leaf' cut into them.

well, i drilled two holes there, when I made my last frame.. I didn't have the tools to "Pizza Cut" it.. ;)

To let moisture out of course..

Wouldnt it be better to just drill one hole and put a grease nipple there? You could then keep the BB well lubricated and force crap out of it with the addition of new grease. A little like the gold something or other hubs from the UK.

People! People! People!

Its for grating cheese ya dummies!

MOISTURE! Honestly.......tsk.

I can't think it was done to let moisture out. That would be one hole.

I can't think it was done to let moisture out. That would be one hole.
might need two holes-ever punched one hole in a can and tried pouring?

when you ride in the rain, rain water goes inside the frame, with that hole at the bottom bracket the water will just drain out in that hole

when you ride in the rain, rain water goes inside the frame, with that hole at the bottom bracket the water will just drain out in that hole
How does water get in the frame?

the fork has a hole, so when you ride on a paddle of water the water will splash uplward and gets inside the frame

the fork has a hole, so when you ride on a paddle of water the water will splash uplward and gets inside the frame
I notice this thing back 20 years ago, I used to hang my bike in the ceiling rears wheels first, I was riding my bike and it suddenly rain, so when I reach my house I was soaking wet, I dried my bike in the garage and after that I hang it, I took a shower after that I notice that my bike was dripping water, after a close look I notice that water was inside the frame, I took it from the ceiling and started shaking the bike and I can hear that water was really inside, so what I did I just let the bike hang rear wheel first and the water dried after several minutes, with that expirience, I would avoid riding my bike when its raining, or I would stop when it starts to rain and seek cover (never seek cover under a tree, you're also liable to get hit by lightning)

Places where water can enter and end up in the bottom bracket:

1) Seatpost clamp area.
2) Bottle bosses
3) chain stays... This is typically only from steel frames where the chain stays had holes near the rear-dropouts for welding purposes.
4) Not the fork as stated above, the hole in the fork goes all the way to the top of the stem... Instead, around the outside of the stem or around the bearings. Typically they are sealed with an over/dust-cap but heavy rain could penitrate. This water would then travel down the down-tube into the BB.
5) And this is the most dangerous and main reason (and the reason you only need one hole)... Condensation.

#5 is the main reason esp for steel bikes... Not sure how important this is for Ti and AL bilkes. Don't see these holes on carbon bikes... Althought parts like seatposts, BB cups, bottle cage bolts and stuff could still get enough condensation on the inside of the frame to corrode in place (unless you grease them one every year or two like you are suppose to!)

[QUOTE=prestonjb]Places where water can enter and end up in the bottom bracket:

14) Not the fork as stated above, the hole in the fork goes all the way to the top of the stem... Instead, around the outside of the stem or around the bearings. Typically they are sealed with an over/dust-cap but heavy rain could penitrate. This water would then travel down the down-tube into the BB.
5) And this is the most dangerous and main reason (and the reason you only need one hole)... Condensation.

PrestonJB,
that practically answers Williams, question, I maybe wrong but then I think it also goes inside thru this thinng (fork).
why if you take out the fork, the head tube has two holes one for the top tube and one for the down tube, the steerer has a space between the steerer and the head tube, I thinks the water goes between this space and ends up inside the down tube of the frame.
again, I maybe wrong.
oscar