I: [CR]Bottom Bracket Cutouts

(Example: Framebuilding:Tubing)

Date: Sat, 31 Aug 2002 02:12:20 -0500
From: "The Maaslands" <TheMaaslands@comcast.net>
Subject: I: [CR]Bottom Bracket Cutouts
To: Classic Rendezvous <Classicrendezvous@bikelist.org>


> TomWitkop wrote first:
>
> Bottom bracket cutouts on steel frames-pleasing to the eye or invitation
> for internal rust (probably both)?... (snip)
> Any suggestions regarding keeping the elements out when there are cutouts
> in the bottom bracket?
> ------------------------------
> Bob Hovey wrote second:
>
> Bottom bracket cutouts are supposed to let moisture out as well as in... (snip)
> If you plug those holes with foam, something similar will probably happen
> inside your BB shell. Best thing is to leave things as they are and just
> make sure that your BB bearings are properly sleeved
> ---------------------------------
> Mark Agree added:
>
> This makes sense to me except for one detail: If there are no cutouts in
> the shell, will stowaway water not sit at the base and still cause
> deterioration anyway? Is there a prevalence of non-cut out shells corroding
> under normal all weather use?

Mark, Bob and Tom,

It is my personal experience that having or not having cut-outs make very little difference. I am basing this on what I have seen on old bikes I have observed and on my own personal riding experience, which included many years of riding trikes through the snowy and salt-laden roads of the Canadian winters. If you don't have any cut-outs the water usually doesn't get into the frame in any large amount, as the places where water can enter are very limited: a) passing through headset up/down the head tube to the vent hole where the down tube is attached b) through the threaded BB c) through the space between the seatpost and seat-tube d) through the vent holes in the stays. Water is not supernatural and always goes the way of least resistance,so huge amounts of water are needed before appreciable amounts of moisture will ever enter any of these passages. None of these occurences are readily possible under normal riding conditions. Even in the extreme winter conditions that I submitted my trikes to could not allow any appreciable amount of moisture in. You must also understand that the spring slush of Canada exposes your bike to a quantity of salt that would make the sweatiest rollers racer blush. In bikes with cut-outs, the inevitable water that does get in through the cut-out also goes out of there, so you once again do not have any problem.

There are however a few provisos (I suppose the plural should actually be provisi): a) when stored, the bike must be kept in normal riding position, with the BB being the lowest part of the bike. Any moisture will therefore collect there. Normal maintenance will reveal any undue rusting of the BB shell well before it is too late. b) a sleeve should always be used, whether with or without a cut-out. This is not only to protect the BB axle from moisture but also against the sand from sand-blasting, possible bits of loose flux... c) the bike must be used regularly. If not used regularly, normal maintenance will not show the wear d) lastly, if the bike is used as a 'rain' bike, it should have mudguards.

Steven Maasland Moorestown, NJ

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