About Steel Tubing used in Bike Frames

Someone on a mailing list recently asked about what to look for
regarding frame-tubing quality when shopping for used bikes. This is
what I wrote, and figured it might help someone else as well. Further
info and/or corrections are welcome!

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Basically, for old steel (used) bikes...

There's 2 types of steel tubes used in bike frames: "hi-tensile" and
"chrome-moly". These are sometimes also called "hitens" and "4130".
Hitens is sometimes commonly called "gaspipe".

Chrome-moly tubing is better, stronger, lighter stuff than hitens,
resulting in a lighter bike frame. That's not to say that bikes made
with the cheaper hitens don't ride well, but they're bound to be
heavier (a pound or two) than a 4130 bike.

Bike makers sometimes mix and match these two steels in budget
frames...my 1988 Nishiki Sport has 4130 main tubes
(seat/top/down/head) while the seat- and chain-stays plus the fork are
hitens. It's still a nice-riding bike!

Chrome-moly tubing can be _butted_ meaning that the inner diameter of
the tube changes over the length of the tube -- typically the tubing
near the ends is thicker-walled than in the center -- the ends where
the lugs or welded joints are is where the strength is needed.
Typical wall thicknesses of butted bike tubing are .9mm/.7mm/.9mm --
though it depends on the particular BRAND of tubing.

Some bike frames like my early 1990's Specialized Rockhopper MTB use
"generic" 4130 tubing. It's butted tubing, but there's no brand
associated with it -- doesn't make it bad stuff or anything.
Higher-zoot steel bikes (especially from Europe/Italy/USA) typically
use either Reynolds (English), Columbus (Italian), or Tange (Japanese)
tubing -- these are the most popular brands used for older road bikes.
True Temper is another brand you might see on some later MTBs.

Reynolds has made their "531" tubing for nearly forever, literarlly
dating back to the 1920s or 1930s. It's not actually chrome-moly
tubing, but the material properties are similar. 531 can be either
butted or non-butted (aka "straight gauge"). Another later type of
their tubing is 501 which IS chromoly and has similar properties
(though I don't think it's butted)...often found on lower-end bikes
but still good stuff. There's also 525 (I think) which is their
modern chrome-moly tubing that has replaced 531. 631/731/831 are
later models of higher-zoot, thinner-walled, heat-treated tubing used
in better frames. See http://www.reynoldsusa.com/english.html and
http://en.wikipedia.org/wiki/Reynolds_531

Columbus is also a long-time maker of tubing. SL was very popular in
the 80s and is similar in characteristics to Reynolds 531. SP is a
heavier-duty version of SL used for larger riders, touring or track
bikes. SLX is like SL but has internal spiral ribbing supposedly to
make it stronger. See http://www.columbustubi.com/eng/1.htm and
http://en.wikipedia.org/wiki/Columbus_tubing

Tange is a Japanese brand of tubing, and early types were rated by
number. Tange Champion #1 was the best/thinnest/lightest, Tange #2
was identical to Columbus SL, #3, #4, #5 --5 is straight-gauge hitens
tubing. See http://www.equusbicycle.com/bike/tange/tange.htm and
http://www.bikeforums.net/archive/index.php/t-116824.html

Bridgestone used Ishiwata tubing from Japan on lots of their bikes,
this is a less popular brand of steel tubing.

For more info, use Google or Wikipedia as starting points. Also
search the archives at http://search.bikelist.org (especially the
framebuilders' list)