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Drilling a hole in the BB

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Drilling a hole in the BB

Old 01-12-23, 01:35 AM
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Drilling a hole in the BB


I have an old steel frame without cable guides on the bottom of the BB. Would it be safe to drill a hole and mount one of those plasticy cable guides?

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Old 01-12-23, 04:12 AM
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Is there a cable guide on the chain stay and is it on the top or bottom? A lot of older frames are designed for cable routing above the bottom bracket
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Old 01-12-23, 04:53 AM
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It's safe to drill a hole in the bottom bracket. I do it on every frame that I build, to allow a way for water to get out.
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Old 01-12-23, 09:35 AM
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I drilled a hole in mine. It's no big deal. Just be aware of what type BB is in the shell and don't drill into the BB or spindle. Though if you hit it and mar it, it likely isn't a big deal either.

But be sure you know whether the cable stop on the chain stay is on the top or bottom. That will tell you if you should be using a cable guide over the BB or under the BB. My old Raleigh was over the BB and the cable guide was a clamp on.

Last edited by Iride01; 01-12-23 at 09:40 AM.
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Old 01-12-23, 11:01 AM
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A lot of cable guides were mounted with a screw through the bottom of the BB on older bikes.
It often interfered when when installing a cartridge type BB on a bike that was originally equipped with a cup & cone type.
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Old 01-12-23, 11:42 AM
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All of my bikes ('96 and mid-2000 vintage) have two holes in the bb shell. One is for water drainage and the second is threaded for a bb cable guide bolt.
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Old 01-12-23, 07:04 PM
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Originally Posted by wallHax View Post
I have an old steel frame... Would it be safe to drill a hole in the bb shell?
I wouldn't do it if it's a 1975 Motobécane Le Champion.
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Old 01-12-23, 08:18 PM
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If you do drill and mount the guide, I suggest using a stainless steel screw/bolt to secure it. Moisture will always find its way to the bottom. If not SS you’ll eventually be removing a seized screw.

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Old 01-12-23, 08:41 PM
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Originally Posted by _ForceD_ View Post
If you do drill and mount the guide, I suggest using a stainless steel screw/bolt to secure it. Moisture will always find its way to the bottom. If not SS you’ll eventually be removing a seized screw.

I would recommend that any holes drilled should be primed/painted or otherwise protected from rust/corrosion. I use Tef-Gel for all dissimilar metal joints, especially in the BB area.
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Old 01-12-23, 08:52 PM
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On my road bikes with below the BB cable guides, I always add a second hole under the rear of the guide. Then file a groove in the guide to create a channel.

This makes a drain, while effectively prevents splashed water from entering.

However, if for any reason you prefer not to drill, you can attach a guide with glue or double sticky tape since the cable tension helps keep it in place anyway.

OTOH, if the frame wants the RD cable routed above the chainstay, you can simply route the FD cable under the BB without a guide. It will not move because it can't.
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Old 01-13-23, 07:50 AM
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Use a self tapping stainless steel sheet metal screw. I would just grease it as the act of screwing it in cuts through any paint.

Double stick take might kinda work, but if you use index shifters the wiggle in the BB guide caused by changing the FD cable position is likely to change your RD cable tension.
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