From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: If the dropout breaks -- what happens?
Date: 19 Oct 1998 16:03:01 GMT

Don McAllaster writes:

> I recently noticed a crack most of the way through my right dropout,
> on the leg that attaches to the seatstay, along with a smaller crack
> on the chainstay leg, and I have stopped riding the bike till I get
> the dropout replaced. My question: if I had been riding, and the
> dropout had cracked completely through, what would have happened?
> Catastrophic failure, or would the wheel have tipped into the stays,
> slowing me to a gentle stop?

Rather than conjecture what might have happened, how about considering
what causes such failures in the first place.  Right rear dropouts
break because the axle is flexing or is already broken, held together
only by the QR skewer.  Old freewheel hubs with long axle overhang
from the bearing have been the principal culprits.  However, Hugi,
Campagnolo and other similar cassette hubs also have large bending
loads on the axles although they use a thicker axle than freewheel
hubs.  These hubs also cause flex that can damage dropouts.

Get a better hub.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: If the dropout breaks -- what happens?
Date: 19 Oct 1998 20:26:53 GMT

Tom writes:

>> Rather than conjecture what might have happened, how about
>> considering what causes such failures in the first place.  Right
>> rear dropouts break because the axle is flexing or is already
>> broken, held together only by the QR skewer.  Old freewheel hubs
>> with long axle overhang from the bearing have been the principal
>> culprits.  However, Hugi, Campagnolo and other similar cassette
>> hubs also have large bending loads on the axles although they use a
>> thicker axle than freewheel hubs.  These hubs also cause flex that
>> can damage dropouts.

> This is not necessarialy true.

> My right rear dropout broke, with no corresponding broken or bent
> rear axle.  I was (and still am) using a Shimano LX freehub
> (cassette) type hub, and the axle is still straight and intact, with
> a tight quick-release skewer.  Perhaps the axle was flexing
> somewhat, but there isn't much room for it to flex in that distance,
> and if it were, there's nothing I can do about it.

You may have had this experience but it doesn't change the fact that
the right dropout breaks from fatigue of bending from axle flex... and
it is the right side where the bending occurs.  If not, how do you
propose they break.  These failures were more common when people used
6 and 7-speed freewheel hubs.

Jobst Brandt      <jbrandt@hpl.hp.com>