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Crank Test.
By Tom Demerly, John Laidlaw,
Mark Trzeciak, Calvin McMahon & Seth Kirkendall.

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.
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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 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 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.
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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?

© Tom Demerly, Bikesport Inc.
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