Test Engineer John Laidlaw built our test apparatus.
The cranks on your bike are the
biggest things you turn to make it go forward (besides the
wheels). They translate force to your drivetrain. In the past
three years a significant number of new designs and manufacturers
have emerged in crank production. With this influx of newer
names and models and materials is the obvious question: How
good are they, how do they compare?
The apparatus was designed to simulate "real world"
pedal forces and measure crank flex.
That is a simple set of questions
with possibly complex answers. First of all, what makes a
crank "good" or "better" to begin with?
In our definition we want the crank to be reasonably light
and reasonably stiff. And we want those two attributes to
be in some sort of reasonable relationship to one another,
whatever that may be. I use the word "reasonable"
intentionally. Crank stiffness is a minor factor in ride quality.
Excessively stiff cranks may make your ride quality (or comfort)
decrease so that, depending on your weight, you feel the road
surface to a greater degree. Excessively light cranks may
have more flex under pedal load and be susceptible to a shorter
life span before failure than a heavy, more durable crank.
Industrial Education teacher Mark Trzeciak install a crank in
the test apparatus.
We set out to conduct a better
test for our customers and ourselves than just restating the
sales literature we are provided with. We read the information
that comes with the products we sell. A lot of it is useful
but some of it is very sales oriented, slanted toward singing
the praises (real or contrived) of the product it accompanies.
For this reason we set out to do something more independent
and hopefully less slanted.
Click
to Enlarge Click to get a closer look
at John Laidlaw's test apparatus and how it works.
It's important to realize we
are amateurs at this. Good amateurs, but amateurs nonetheless.
Engineering tests are not our business. An experienced cyclist
and an accredited engineer who earns his living building test
fixtures for one of the Big Three auto companies built the
test apparatus. John Laidlaw has been riding bikes for years
and is a talented time trialist and officer in a local bike
club. He became interested in our project when we mentioned
it to him three months ago and described our frustration at
not being able to get good product information. John looked
at the problem of generating usable test results from a real
world perspective.
Whether the test results we generated
are relevant or not is up to you, but the results we generated
do indicate some differences between these cranks within the
parameters of our test. And, this test does mimic closely
the manner in which drive forces are applied through a pedal
spindle to a drive side crank arm and into the bottom bracket
spindle by a cyclist pedaling.
John Laidlaw and Colin
"Calvin" McMahon on test day.
Due to time constraints
when the tests were conducted we only tested drive
side cranks and only Shimano compatible models.
We do have the capability to test the newer ISIS
drive bottom bracket cranks and also non-drive
side crank arms. Initially, we wanted to get some
type of test done to see if it was a worthwhile
project to continue.
The test apparatus itself holds
a bottom bracket spindle in a static position.
A crank is bolted to the fixed bottom bracket
spindle the same way it would be when mounting
on an actual bicycle. A pedal spindle, taken from
a pair of pedals, is bolted into the crank arm
in the same manner it would be on a bike.
An air ram then applies load
to the pedal spindle, via a special fixture simulating
pedaling force, then the test crank arm in increments
controlled by a regulator. As the load begins to accumulate
a gauge on the crank arm measures the deflection or flex
of the crank under a given load. Simple. Then we weigh
the cranks. Simpler.
One thing that was brought
to my attention by a reader on the Slowtwitch.com forum
that is worth mentioning about this test: This test only
measures the stiffness of the crank arm itself. Not the
entire crankset. Differences in the stiffness of the crank
spider could affect the overall performance of the crank
when mounted on the bike. If anything, this only points
out how truly difficult it is to quantify the very, very
small differences there are in performance between these
cranks.
What this means in the real
world is we wanted to find the lightest crank that is
still stiff. Since each of these cranks are production
cranks and we've used them all operationally we can deduce
that they are all "stiff enough for normal riding
and racing". In other words, they all work. And,
having said that, the fact that we had to develop this
elaborate test to figure out the difference between them
speaks to the probability that the differences are so
small they probably don't influence your performance or
enjoyment of your bike.
Each
crank was weighed to compare flex to weight ratios.
All these cranks work. But,
if you're a technophile and enjoy such "technotainment"
well, here you go…
We tested the Shimano Dura-Ace,
Shimano Ultegra, FSA Carbon Pro Team and Ritchey Pro all
in 172.5 mm length and drive side arms only.
In a nutshell this is what
we discovered:
The FSA Carbon Crank is the
lightest in the test at 252 grams, 9% lighter than the
heaviest crank in the test (Shimano Ultegra). The spread
from heaviest to lightest was 22 grams, less than 1 ounce.
To put that in perspective a pair of Oakley Twenty sunglasses
weighs 24 grams. So, switching from an Ultegra crank to
an FSA Carbon Pro Team crank is about the same as taking
off your sunglasses.
The FSA Carbon Pro Team crank test the lightest but most
flexible, although stiff enough for Tour de France riders.
The FSA Carbon Pro Team crank
was also the most flexible in the test, flexing eighty-two
one thousandths of an inch (.082) under 124 pounds of
pedaling force. The reality check on that is none of the
cranks moved enough to really be able to see the actual
movement. Also, as mentioned above, this is only a measurement
of the crank arm itself- not including the spider. Seperate
test results published elsewhere suggest that the crank
spider on the FSA Carbon Pro Team is actually substantially
stiffer than many popular aluminum cranks. Since our test
did not record this data, we cannot verify or dispute
these claims.
To me, that means all of
these cranks are stiff enough for even a pro cyclist in
the Tour de France. And, in fact, a lot of pros are using
the FSA Carbon Pro Team crank in the Tour de France and
other pro races and triathlons. The deflection to weight
ratio of the FSA cranks in our test was 8.972 micrometers/gram
according to U of M engineering student Seth Kirkendall.
This was the highest deflection per gram in our test of
four cranks. In other words, marginally these crank arms
were the most flexible, not accounting for the spider.
There is no denying the allure of FSA's new Carbon Pro Team
Crank shown here with the difficult to find Time Trial 54
tooth chainrings. This is the crank from Tom Demerly's Yaqui
Carbo triathlon bike.
A surprise of the test is
how good the less expensive cranks are, such as the Ritchey
Pro. This crank was the second lightest in our test and
the stiffest. As a result, based on the context of this
data, you could support the conclusion that this crank
tested "best" or "stiffest per gram"
of any in the test. Now consider that it is the least
expensive in the test at a little over $150 dollars (Compared
to the FSA at a selling price between $359.99-$399.99)
and it seems like a good choice. The Ritchey Pro crank
tested at 4.847 micrometers of deflection/gram. This is
the least deflection or "flex" per gram of any
of the four cranks we tested. Impressive considering their
price. Ritchey has since commented that they were not
surprised by the test results and that their more expensive
"WCS" series of cranks is even lighter and stiffer.
This crank has been used extensively by Michellie Jones.
Ritchey credited their unique four-arm design with much
of the crank's performance advantages.These results suggest
that the Ritchey cranks are an overlooked upgrade to your
bike.
The surprise of our test was the excellent Ritchey Pro cranks.
This shows you don't have to spend big money to get excellent
equipment.
There are intangibles in
this test though. As a reader on the Slowtwitch.com forum
said the appearance of the cranks is a factor in a person's
buying decision, and the FSA cranks look really cool.
I have the FSA Carbon Pro Team Issue cranks on my new
Yaqui Carbo. I also used them on my Empella Cyclocross
bike for the '02 cyclocross season. No problems. The unusual
bend of the arms made them come closer to the bony protrusion
on the side of my ankle but that has not been an issue.
The Shimano Dura-Ace crank
tested well (surprise…) but was heavier than the
Ritchey and the FSA by a handful of grams. The Dura-Ace
was the third stiffest and the third heaviest in the test.
It was also the second most expensive but does have a
beautiful finish. Dura-Ace measured 6.206 micrometers
deflection (flex) per gram. They came in "third"
in the stiffness to weight ratio test. Dura-Ace has been
an old standby and has won the last four Tours de France.
It is slanted for a major makeover in '04 that will change
these numbers.
Although Dura-Ace tested well we were somewhat surprised
it didn't test better.
Shimano Ultegra cranks are
the heaviest in our test at 274 grams but the second stiffest:
Stiffer than both Dura-Ace and FSA Carbon Pro Team. To
me, this only points out what a good group Ultegra is
for most cyclists, albeit we're splitting hairs at this
point. The Ultegra cranks moved 5.098 micrometers per
gram of weight in our test, putting them second behind
Ritchey and in front of Dura-Ace (surprisingly) in the
weight/stiffness ratio contest. Again, this confirms what
we already know: Ultegra is nice stuff.
So what does this test mean?
Not much. No doubt the companies who tested "poorly"
(realistically, no one did in this test) will dispute
the test protocols, point out the shortcomings in our
test apparatus, question the credentials of our test engineers
and basically do whatever they have to do to debunk the
results.
Mark Trzeciak calibrates the dial
indicator for another test run.
Not us. After all the money
we spent and time exerted I think this proves something
we already knew: Components don't mean much.The differences
between them are often so small they won't influence your
performance. Having a stem 1 cm. too long, the wrong seat
tube angle on your frame for your measurements or a saddle
height off by 7mm would make a much more tangible difference
in performance and comfort than the differences we discovered
between any of these cranks.
Click
to Enlarge Basically the lower the two bars
(red and yellow) the better the crank performance in the
context of our test. Click to enlarge the graph.
This only points to the shortsightedness
of shopping for a bike by components. When it takes elaborate
test apparatus and sensitive instruments to measure the
minor differences between components not even a Tour de
France professional or Ironman winner will notice perceivable
changes. I simply got some FSA Carbon Pro Team cranks
because they are the lightest in the test and plenty stiff
enough for me. I also do happen to think they look cool
and they are expensive so I'm hoping customers see mine,
want some themselves and then I sell a few extra sets
and make a few extra dollars. Bottom line, pretty simple.
It all goes back to this:
Buy your bike by fit. Buy your components by fit. Then
you will get the best performance. But didn't we already
know that?
