ieandro

Anyone here drill a drain hole under the BB shell?
Drilling it would leave raw, unprotected steel and being in the worst area to pick up water and gunk, how could you protect it from being a primary jump off for rust?

ChromePista

Water can get into a frame through various places, but it can collect in the BB shell (frame) and not get out. I have drilled a drain hole on multiple bikes that collected water and it solved the problem completely. This works for steel and aluminum framed bikes. I do not advise drilling a carbon frame.

1. Remove crank, BB cartridge/axle, BB cups
2. Clean water and rust out of the BB shell (frame), using old tooth brush on BB shell threads
3. Turn bike upside down with the BB shell up
4. Stuff BB shell with paper towels to catch drilling shavings
5. Mark best site to drill (the very bottom, dead center)
6. Use a center punch to put a dimple in the metal. If you skip this step as most novices do, the drill bit will "walk" and make a mess. It must be a center punch designed for this purpose. Must people don't have one in their tool box, but it is a "must have" for this procedure to be successful
7. Using a fresh 5/32" drill bit, drill the hole. This is the easy part. The stuffed paper towels catch shavings and prevent over drilling
8. Clean off any metal shavings and burrs inside and out
9. Clean and degrease the hole
10. Apply clear nail polish inside and outside the hole. This seals the bare metal and prevents rust in steel framed bikes. It is not so important for aluminum framed bikes
11. Use a toothpick to pop any "bubble' in the nail polish that might block the hole and defeat the purpose of drilling the drainage hole
12. Cut a 3/4" piece of electrical tape and it fold over on itself in such a way that there is a sticky end and a non-sticky flap. Apply the sticky end just in front of the hole so that the non-sticky flap covers the hole. This prevents water from splashing up into the hole, but does not impede drainage at all
13. Make sure BB shell is clean, reinstall BB cups and cartridge with grease, reinstall cranks

I did this modification to an aluminum framed commuter bike that I rode in many downpours. It was amazing how much water was trapped inside before the drain hole was drilled. Much later after I did this mod, I was switching out BB cartridges to change my chain line and noticed the inside of the BB shell was completely clean and bone dry, so the mod worked as planned. I recently did this mod to my chrome Pista which had dampness and early rust inside the shell. I am confident it will help prevent problems in the future.

AfterThisNap

done

mander

What's the big deal?? The genius of a drain hole is, it's self-draining. If water goes in it will get right out again in a hurry, unlike water that enters an undrilled bb shell.

You should rustcheck it when you're finished, but that goes without saying for any place where you can access the inside of a steel frame.

Six jours

Think about the underside of your fork/steerer tube. Many/most steel bikes leave that part unsealed and unprotected, and I've never seen anyone die from it. Back in the day, some folks would seal up the hole with a cork or something, but would then discover, upon removing the cork, that water had become trapped in there and caused rust. Some folks then began drilling a small hole in the cork to allow water out. This always seemed like a long and stupid line of thought to me, and I always expected to someday see someone with a plug in the cork hole, itself drilled with a smaller hole. Etc.

Personally, I'm going to continue spending my time worrying about more important things, like how many beer caps I can stack up before they fall over.

ieandro

Well have fun with your bottlecaps, but i believe my question was answered with the whole nail polish thing. I was merely asking how to protect the raw hole and not how a drain hole works or why people would cork a hole in their fork.
Thanks for the replies !

ChromePista

I think your original question is a valid one. Drilling a frame is not to be taken lightly. There are definitely right and wrong ways to do it. I think I covered most of the bases.

You did not give me credit for the tape flap. It acts like a semi check valve. Water can go out but cannot easily get in. A true check valve would function in total submersion.

ieandro

Oh hey sorry about that.

mander

FWIW and in all seriousness, when I look at my year old drain hole i see clean, raw steel. I rustchecked it when i first drilled it, and it probably gets a little of the grease my bb is covered in wept on it. I don't think you need a fancy valve on it or anything, but perhaps time will tell. Just use a center punch for sure.

waldner

This is an interensting topic. My track frame (which I rather use for city riding) has two parallell slots in the BB shell. For track use this seems reasonable, as it would let any entering water escape straight away.

However, my main concern is not for water but for any dirt, gravel or whatever that might stick in the (non-cartridge) BB grease and cause premature wear. To prevent this, I covered the holes with a piece of duct tape, much like described by ChromePista above.

Does this make any sense to you?

IMG_0125.jpg

ChromePista

If I am not mistaken, old Colnago road bikes had the three-leafed clover logo cut into the bottom of the BB shell, which served both form and function. That was well before the advent of sealed BB cartridges. The standard fitment was a genuine Campy plastic sleeve which had an accordion waist. It would fit between the BB cup and protect the axle.

The BB slots in that track frame are enormous. Could they have been designed for weight savings? I would not be surprise if that bike whistled at full speed.

AfterThisNap

framesaver and forget it.

Six jours

Oh. Well then screw you too.

andypants

I just took apart my bike to get it painted and had quite a bit of water come out, and it hadn't rained in a week or so. Needless to say, I drilled it before dropping it off.

LanceW

I think alot of it depends on your bike. If you bike has a tendency to collect water then drill it. Other wise don't. My had his drilled and his BB was rusty as hell when we replanced it last week. I replanced mine at the same time and it was fine nice and clean.

roadgator

None really. Aside from a track frame on the street, you should at least use a sealed BB. Problem solved, no tape required.

roadgator

My guess is that it was for oiling, since track riders have been said to use light oil instead of grease for lower friction. You could squirt in a little oil before a race without having to open the BB. Track bikes aren't meant to be ridden in the rain...