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


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Date: Tue, 6 Jul 2010 07:28:45 -0700
From: Jim Merz <jameshmerz@gmail.com>
To: 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


My wording was not correct, you made it clear. However, a heavy, strong rider using a frame made with 531SL can stress the tubes to cause early failure. In this case the much higher tensile strength of 753 makes for a much longer lasting frame. I agree that the ride is very nice also.

Jim Merz Big Sur CA

On Mon, Jul 5, 2010 at 9:43 PM, Jan Heine <heine94@earthlink.net> wrote:
> 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
> --