| Best frame material |
Steel vs Aluminum | Check
for wear | Choosing a tube set | Tubing manufacturers
Here are a couple sources of information and commentaries on bicycle frame
building and metallurgy related to bicycle frame tubing.
Maintenance and Building. Several books pertaining to designing and
building bikes are included. Unfortunately most are not easy to find.
(2) The page Bicycle Science, Engineering and
(3) Frame builders archives:
(4) What is the best material for a bike frame?
There is no absolute answer. It boils done to the engineering of the fame
and the personal preference of the user. By choosing different tubing
(tube diameter and wall thickness) and frame geometry, a skilled frame builder
can make a soft or stiff frame out of steel, aluminum or alloy. It is not
so much a matter of the material, but how it is used that determines the ride
characteristics of a bicycle. It is a mystery what determines every
individual riders personal preference. For articles on choosing a material
search for "metallurgy" and "buying
bikes" in the archives of the
Adventure Cycling magazine on their web site:
. Many of these articles were written by John Schubert, Technical Editor,
Adventure Cyclist Magazine. Here is a sample of his insight, specifically
touring bike frames:
Out of steel, aluminum, titanium and carbon fiber frames, my favorites are
steel and aluminum, but intellectual honesty demands that I point out that
other well-informed people will have different preferences. My reasoning:
Carbon fiber needs to be babied -- cleaned after every ride, stored in a nice
place, washed and waxed from time to time, and protected from even the
slightest abuse, which is inconsistent with most touring. A
good steel bike offers a great ride. Aluminum can be (and these days it
customarily is) designed to be lighter and stiffer than steel.
However, these properties (strength and stiffness) depend on the entire
bike design. The material selection is only the beginning.
Metal matrix allows some improvements in the bulk properties of aluminum
that mere alloying cannot achieve. It's on the order of magnitude of 10
improvement in stiffness and/or strength.
Some manufacturers have embraced metal matrix. Others haven't bothered,
saying it's not worth the bother to get that fairly small improvement over
aluminum (which basically has terrific bulk properties for bicycle frame
Since I at least try to speak with scientific rigor, and not throw out slapshot
opinions: Whether metal matrix in general, or "X" design in particular,
translates into an improved bike frame, and how that would compare with other
good bike frames of other materials, would be a good topic for a master's
thesis. However, no one who is interested has the combination of time, money
and skills to do the complex research required to really answer the question.
You won't find any meaningful published test data to compare
different frames. The commercial magazines have all descended into the "like
wow dude" level of un-sophistication in road tests, and aren't about to get
serious. Adventure Cyclist has neither the money nor the inclination to try.
Manufacturers' literature is usually skimpy and occasionally inaccurate,
because their goal is to sell, not to write a thesis."
I'm not as enthralled with titanium because it's an expensive way to get a
bike slightly lighter and not as stiff as an aluminum bike. And frankly, I
haven't kept up with the latest carbon fiber designs enough to have a well
Getting back to various steel bikes, if all the frame dimensions were the
same, the metallurgical differences would be invisible to you as a rider.
Every kind of steel "feels" the same to the rider with two caveats:
Better steels are stronger (more crashworthy), and hence they allow the
bike designer to use thinner-wall tubing to save weight. This also makes the
bike less stiff. So yes, the most expensive steel bike will not be as rigid as
a lesser-priced steel bike. However, the differences are minor.
A saying among people who write road test articles is "My favorite
bike is the one I just finished riding." Whatever the differences are,
they're small enough that one can fall in love with any of them.
Comfort differences among road frames are tiny, because every road frame is
a rigid truss structure that has very little "give" in the vertical
The best way for you to ensure your comfort is to get a bike that accepts
larger tires. The air volume of good-size tires absorbs far, far more road
shock than the tiny differences among frame materials. To get this kind of
bike, insist on a touring bike that will accept tires at least as large as
700x32C, or preferably 700x35C. If you get such a bike, you can always put
skinny tires on it -- in which case it will handle just about identically to a
racing bike (which couldn't accept the more comfortable touring tires).
Not all bike shops stock touring bikes, and some would be unwilling to
order them for you, but such bikes are made by Trek, Cannondale, Jamis,
Raleigh, Bianchi and numerous smaller companies. Don't let someone sell you a
"racing bike with three chainwheels," though -- such bikes, which
are more common in the bike business, can't accept the larger-diameter tires
and therefore won't have the comfort for touring."
(5) Steel vs. Aluminum for chopper bikes / art bikes: Chalo, a long time custom bike builder and friend of IBF, gives the
For amateur chopper construction, steel is a much better material than
aluminum for several reasons.
Steel can be welded without significant loss of strength. Aluminum requires
expensive heat treatment to restore its strength after welding.
The equipment and inert gases required to weld aluminum are much more
expensive and elaborate than necessary for steel.
Steel can be brazed with brass, silver, nickel-copper, or other filler
alloys. Aluminum cannot be brazed in the conventional sense. There are aluminum
solders, but they are too weak to be useful for bicycles.
Steel can be drilled and bolted without unusual risk of cracks propagating
from the drilled holes. Aluminum will often generate cracks starting at holes
drilled in stress areas.
Steel can be formed (bent) to a greater degree before significant strength is
lost, compared to aluminum which only forms well in its annealed (soft and weak)
When a chopper's design is insufficient to cope with the loads imposed upon
it, steel is more likely to bend rather than break off completely when it fails.
Add to all these reasons the much lower cost of steel bike frames and raw
materials of any given quality, and it's pretty easy to see that steel is a
better material for chopper building than aluminum in most circumstances. A few
exceptions to this general principle are as follows:
Parts machined from solid blocks are better made from aluminum, because it is
lighter and easier to cut.
When a commercial bike frame is to be used without modification, and when the
parts attached to it do not add unusual stresses above those expected from
normal use, then an aluminum frame may be used.
When very fat tubes and parts are desired which would be too heavy if made
from steel, aluminum may be used. The rule of thumb is that you should use at
least the same weight of aluminum that you would steel, about 3 times more
volume than a comparable steel part.
(6) Do frames fatigue, wear out and fail?
As you might imagine, frames vary tremendously. So many millions of
frames have been built, in so many thousands of designs, that some are going to
be more failure-prone than others.
To generalize, aluminum is fussier than steel. Aluminum has a finite fatigue
life; steel doesn't. That's what the textbooks say. But some steel frames manage
to crack too.
Similarly, titanium is supposed to be just about crack-proof, but there are
exceptions to that too. And carbon fiber's structural integrity depends heavily
on the quality of the design and workmanship.
An aluminum frame subject to repeated heavy loading (being bashed in hard mountain bike use) may last a few years.
At the other extreme, an aluminum frame that is not stressed (ridden gently on the
smooth road) may last for decades.
At appropriate intervals all frames should be inspected from nose to toes for small cracks. Small
cracks grow; they never shrink. So when you see one, take it to your dealer, who
will probably tell you the frame is toast.
Cannondale Bicycle Corporation has posted a discussion of this topic in their
online Owner's Manuel,
http://www.cannondale.com/Asset/iu_files/116376.pdf. Go to section D,
"Inspection for Safety" and take particular note of "Fatigue 101," in Part II.
Gary Klein discusses some quality issues of aluminum frames starting on page
5 of the PDF document at
"Aluminum Time Bomb" in the May 1995 issue of
Mountain Bike Action magazine also
address this issue.
(7) How do you choose an aluminum tube set?
Despite what the advertising tells you, the specific alloy of aluminum used
is one of the least important factors in determining ride characteristics.
All alloys of aluminum have identical weight and stiffness. Where the various
alloys differ is in their yield strength (which determines crashworthiness, not
ride qualities), resistance to fatigue, and stuff that affects manufacturing
processes (how to weld, how/whether to heat treat, etc.) This is largely
academic for the end user because all high end bikes will be designed to have
acceptable crashworthiness and fatigue qualities.
The physical dimensions of the frame -- tube diameter and wall thickness --
determine the ride quality, which is the factor I would base my buying
decision on. However, there is no way to tease that information out of the
sparse information the manufacturers provide. They generally don't publicize
enough information to plug into the finite element analysis program that would
be necessary to even try to calculate this.
So we're back to test rides. Find a shop that allows good test rides, do an
A-B comparison, with the tires pumped to identical pressure. And if you find you
have trouble telling the difference, don't be surprised. The differences in
riding qualities among many, many, many bikes are so minute that you might as
well pick the paint job you like the most.
John Schubert, Technical Editor, Adventure Cyclist Magazine
(8) Bicycle tubing manufactures:
Return to the Library