Re: [CR] Frame stiffness; Was: Phil disk brake, Vitus 172


Example: Framebuilders:Jack Taylor

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References: <8098104.106281.1278338642931.JavaMail.root@vms069.mailsrvcs.net> <08E1D97A-259C-4719-A42D-A59E61F0CA7E@mac.com> <DD4CC34FA0C344B9864304842BF815ED@D8XCLL51> <AANLkTimU4JVKLavQGUh3P2Id5ecTZVBPeusQ0kwVeDxk@mail.gmail.com>
Date: Mon, 5 Jul 2010 21:43:18 -0700
To: Jim Merz <jameshmerz@gmail.com>, Harry Travis <travis.harry@gmail.com>
From: Jan Heine <heine94@earthlink.net>
Cc: JB Froke <jbfroke@mac.com>, hmsachs@verizon.net, classicrendezvous@bikelist.org
Subject: Re: [CR] Frame stiffness; Was: Phil disk brake, Vitus 172


At 8:06 PM -0700 7/5/10, Jim Merz wrote:
>frame getting "soft" from use [...] old wife's tale. The benefit
>from using a very high
>tensile steel such as 753 is that a strong rider can flex it quite far
>without yielding it.

I have yet to see a rider strong enough to flex a frame made from 531 to the yield point...

I believe that the myth of high-end steels being stiffer came from two observations, none of which actually relate to stiffness:

1. The super high-tensile strength steels are much harder to cold-set. So builders often thought they were stiffer, when in fact, they just required more bending until they took a set.

2. Many riders prefer flexible frames without knowing it. When asking these riders, they'll often tell you that their new frame is "so stiff, it accelerates wonderfully," even though when measured, the frame is much less stiff than their old one that felt "dead." So when the super-high tensile steel frame with ultra-thin walls "felt stiff," it contradicted the fact that thinner walls make a tube more flexible. The only way around this conundrum was to reason that the new super-high tensile steel must be inherently stiffer, which more than makes up for the thinner walls.

We have documented in double-blind tests that more flexible frames can accelerate better for some riders. It's too involved a subject for this thread...

As for frames going soft, the French never heard of that one, otherwise, they wouldn't have reconditioned decades-old favorite frames... I don't know whether Italians believed this, so the only place where I have seen this concern documented is Britain, and from there, it seems to have migrated across the English-speaking world.

Jan Heine Editor Bicycle Quarterly 2116 Western Ave. Seattle WA 98121 http://www.vintagebicyclepress.com --