There are two issues to look at: material properties and tubing design. In materials, both steels (531 and Mangalloy) are very similar. The most important material property in terms of ride properties is the modulus of elasticity. This parameter characterizes the springiness of a standard sample of the steel, how much it flexes when a given amount of force is applied. Stiffer materials flex less. The important thing about this is that all steels used for bikes, current and historically, have just about the same modulus of elasticity.
Next issue is tube design. Tubes with thicker walls or with larger diameter will be stiffer. The most important of these properties is diameter, though the effect of wall thickness is very significant and noticable. The 1983 Trek brochure shows the wall thicknesses of the tubes they used. The top tube thichnesses are (Butt area/ middle area/ butt area in mm):
753R: .7/.5/.7 531C: .8/.5/.8 501: .9/.6/.9 Tange: 1.0/.7/1.0
Note that the Tange is the thickest. Given the same tube lengths, tube application, and joining quality, the Tange-tubed frame will feel stiffer and presumably harsher. It will also be heavier, since the densities of all these steels will be identical. It might be marginally more efficient, but that's not a matter for simple analysis like this.
Ken Freeman Ann Arbor, MI USA
On Mon, May 25, 2009 at 1:45 AM, Bruce Jaffe <brucejaffe@earthlink.net>wrote:
> I wonder if any list members could comment on the kind of differences in
> performance or ride that might be experienced riding two lugged steel
> frames
> made by Trek in the early 80's. Both frames share the identical
> "sport-touring" geometry. The only difference is one frame is made from
> double butted Reynolds 531, while the other is made from double butted
> Tange 2001 mangalloy.
>
> Thanks for any insights you can provide.
>
> Bruce Jaffe
> Irvine, CA