I just purchased that Bob Jackson frame from ebay. I looked up Reynolds tubing types on their web site and could find no reference to 653 tubing which this bike is. Is there a comprehensive site for tubing types somewhere or does anyone know how 653 fits into the Reynolds line up. A secondary question. I see a lot of emphasis on 531 tubing almost like it is the Holy Grail of bike tubing. Yet I see that is has been around since 1935 and surely metallurgy has progressed since then so why the fascination with this tubing. Since I am still new to the lightweight world this may seem like a stupid question but that never stopped me before.