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Drilling BB shells

FlipSide

Turbo Monkey
Sep 24, 2001
1,376
804
I have a new steel hardtail coming. It will be my 1st non-carbon bike in about 10 years.

In the past, I have always drilled a small hole in my BB shell (on alloy or steel frames) to let escape any water that could find it's way into the frame. Is that still necessary? I always though water was entering from the top of the seat post, but never really investigated that much. With the dropper posts we have now, I am thinking the problem may not exist anymore. On the other hand, the internal routing for the dropper may create a new place for water to get in.

What do you think? Is drilling a small hole in the BB shell to let the water escape still relevant in 2022?

Thanks!
 

gonefirefightin

free wieners
I have a new steel hardtail coming. It will be my 1st non-carbon bike in about 10 years.

In the past, I have always drilled a small hole in my BB shell (on alloy or steel frames) to let escape any water that could find it's way into the frame. Is that still necessary? I always though water was entering from the top of the seat post, but never really investigated that much. With the dropper posts we have now, I am thinking the problem may not exist anymore. On the other hand, the internal routing for the dropper may create a new place for water to get in.

What do you think? Is drilling a small hole in the BB shell to let the water escape still relevant in 2022?

Thanks!
If you service the bike enough at proper intervals you shouldn't have a need to drill anything theoretically but if you are in a predominately wet environment or know you have frequent water crossings and such it would be a prudent choice. I personally service and lube BB's at least once a year thus no need to drill anything.
 

Westy

the teste
Nov 22, 2002
54,241
20,024
Sleazattle
I ride in some really wet conditions and found that water will get into the seat tube of my steel hardtail. Even sealing the dropper cable entry with RTV.

You have to remember that when you raise/lower your post it will displace air in your seat tube and will likely suck in water when extended.
 

FlipSide

Turbo Monkey
Sep 24, 2001
1,376
804
OK, thanks a lot!

I am not really riding that much in very wet conditions, at least compared to people living in the UK or on the West Coast. I'll probably leave it like that at first and pay attention for any sign of water accumulation.

Thanks again!
 

gonefirefightin

free wieners
OK, thanks a lot!

I am not really riding that much in very wet conditions, at least compared to people living in the UK or on the West Coast. I'll probably leave it like that at first and pay attention for any sign of water accumulation.

Thanks again!
Fer sher, I would opt for keeping it water/air tight to start then adding holes if needed down the road but being in the PNW I havent seen a need to drill any of mine personally.
 

canadmos

Cake Tease
May 29, 2011
20,195
19,158
Canaderp
I once found a puddle of water in one of my frames sitting in the bottom bracket, luckily I had the BB tube greased to hell and back.

I'd say just monitor it the first season and if you have water sitting in there, do a tiny hole.
 
I once found a puddle of water in one of my frames sitting in the bottom bracket, luckily I had the BB tube greased to hell and back.

I'd say just monitor it the first season and if you have water sitting in there, do a tiny hole.
Or a hole with a removable plug for when it's stored inside - that way, less chance of water getting in during a stream crossing.
 

FlipSide

Turbo Monkey
Sep 24, 2001
1,376
804
@FlipSide I would definitely drill a hole but there’s probably already one in there. Also, spray Fluid Film inside the frame if you are worried. What did you get?
Thanks! Yes, I have some Boeshield T9 already, leftover from when I built my Voodoo frame about 10 years ago.

I got a Kona Honzo ESD frameset. I am building it with a Lyrik Ultimate 150mm, Flow MK4 on RF Vault hubs, etc. Should be pretty nice!
 

HardtailHack

used an iron once
Jan 20, 2009
6,637
5,455
I don't really think it makes much difference, only the water from the ST can drain out there, the other tubes will still sit with moisture in them.
I always end up with a bunch of moisture inside my hardtails with a BB hole or no BB hole.

My current cranks can't run a tube so the bearings are constantly damp and they are oddly some of the longest lasting crank bearings I have ever had.

One of the Syntace seat clamps may reduce the amount of water entering the ST.