Road Bike Crank Test
As a lot of you tuning in already know, we’ve been working on our in-house road crank tests for the last 7 years, with our updates posted alongside all the previously tested cranks. One thing we’ve come to realize is that while some cranks have obvious changes over the years, others have quietly evolved behind the scenes. Because of this and a desire to build a new testing fixture, particularly one that would handle BB30 cranks as well, we decided it was time to retire the old tests and start again with a clean slate. Please note that because of the new fixture and testing loads, results from this and future tests are not comparable to results from previous tests. Being that only 2 of the first 12 cranks tested in the last round carry over from previous tests we felt this was a good time to make the change.
Luckily, Jason Krantz is back as our resident data-cruncher (Jason is an experienced mechanical engineer with a strong background in both finite element analysis and composite materials.) We’re always happy to have him work with us on our tests and place a high value on his contributions.
Disclaimer: A lot of typing and numbers have gone into this article and we apologize in advance for any typos, but would warn that the possibility of mistakes is present.
About the testing method: Each arm was preloaded with 50 lbs of weight, then all calipers and load cells were zeroed out. Another 150 lbs was added and the difference was measured in mm. Each arm was tested three times and an average of those measurements is the result. A lower number represents a stiffer crank. These will be labeled as Deflection-D(Drive side deflection) and Deflection-ND(non-drive side deflection) . This method uses a total load of 200 pounds, in comparison to the old test which used a total load of 250 pounds. Further more in previous tests a large solid rod was used to simulate the pedal and load was applied 60mm from crank arm. With the new fixture, we’ve switched to using actual steel pedal spindles removed from a set of production pedals. The loading has also been moved slightly inward toward the crank arm.
Stiffness/Weight: Is determined by: (1/average deflection)/weight)x10000
Notes about stiffness: According to conventional wisdom, the more pedaling stiffness the better. Stiffness implies efficiency, along with the notion of a stiffer bike inspiring confident and responsive handling. As desirable as those traits are, and even after a crank’s stiffness is proven empirically, the outcome still seems subjective—we are simply going by how many people feel more efficient on a bike with a stiff drivetrain. But it’s far from clear whether that tactile, from-my-quads-directly-to-the-road sensation is actually faster. This is the question: is a stiffer drivetrain actually more efficient, or does it just feel that way? Looking at the numbers, we can see that average deflections range from roughly 0.20 inches to 0.30 inches. From this, we can generalize and say that the most flexible crank is about 50% more flexible than the stiffest crank. It’s easy to imagine that the stiffer cranks feel better, or have better “power transfer,” which is a particularly vague and ill-defined concept.
So how can we move beyond “feel” and attempt to quantify whether a stiffer crank is better? The answer is, strain energy. Strain energy is simply the energy stored by an object as it is loaded. Quantifying how much energy stored by a given spring under a particular load is a basic problem that works perfectly well for understanding whether a stiff bicycle crank is better than a slightly less stiff crank. That is, you can think of a bicycle crank as a very stiff, oddly-shaped spring. The equations for calculating stored energy in a beam under bending are fairly simple. The following figure is taken from a Creative Commons-licensed engineering textbook by Piaras Kelly at the University of Auckland:In the equation above, U is strain energy, M is applied moment (torque), L is beam length, E is the Young’s modulus (stiffness) of the beam material, and I is the moment of inertia of the beam cross-section. A crank is somewhat beam-like, but it’s not really a beam. And we’re not applying a pure moment but rather a force at a distance that creates a moment. This bending example is somewhat close, but it’s still not a very good approximation of a crank on a bicycle. We can get a very good approximation of a crank on a bicycle by using finite element analysis (FEA). To find out how much strain energy a typical crank stores, we can solve an FEA model to find the strain energy of each of the constituent elements. We can then add up all of those strain energies to get the strain energy of the whole crank. This strain energy can then be converted into absorbed power by assuming a cadence; we used 100 RPM for this example. In this way, we can determine exactly how much power goes into crank flex, which can then tell us how much crank flex matters to total power output. We used ANSYS, a well-regarded FEA program, to model a generic aluminum left crankarm (172.5mm) and half an attached 24mm steel bottom bracket spindle.The remote force works out to 250 pounds of force (lbf), and it is applied 60mm to the outside of the center of the pedal threads. This simulates applying the force through a pedal.
Most of the action is happening on the inside of the crank; the interior elements report a higher strain energy value than the external ones do. But things get a lot more interesting when we dump the strain energy values for each of the elements to a spreadsheet. By summing the elements’ strain energy values, we can get the total strain energy for the entire crank and half BB spindle. The total strain energy of this crank under a 250-lb pedaling load is 4.604 Joules. As a unit, Joules don’t do much for most cyclists. We can convert them to a more useful unit by assuming a cadence of 100 RPM. At that cadence, this half-crank soaks up 7.67 Watts. The right-hand crank is usually stiffer than its left-hand counterpart, so it stores correspondingly less strain energy. So rather than doubling the left-hand figure, we’ll round down a bit to 14 Watts for the entire crank/BB axle system. 14 Watts might sound like a lot, and it is. But let’s keep in mind that this is a 250-lb force applied 1.67 times per second. A rider applying this force over 160 degrees of crank rotation produces an average power of 880 Watts, which few of us can sustain for long. And 14 Watts out of 880 is 1.6% To put this in perspective, if you were pedaling along at a steady 300 Watts, your crank would be absorbing 4.8 Watts of your effort. But those 4.8 Watts go into winding up your crank “spring,” which will spring back with nearly all the energy that was spent winding it up. Some of that spring-back energy probably helps turn the drivetrain while some of it may behave in a negative manner. However, there’s a fair amount of debate about how much energy is returned. The answer to the energy-return question involves kinematic analysis far outside the scope of this article. For now, we’ll assume that all of those 4.8 Watts spring back in a way that doesn’t help turn the drivetrain nor hinder it. As mentioned before, the most flexible crank in this review shows about 50% more deflection than the stiffest crank. Our FEA crank is quite flexible, and it absorbs 4.8 Watts of a 300-watt effort. Strain energy, roughly speaking, is inversely proportional to stiffness. We can use these relationships to calculate that at 300 Watts, our flexible crank absorbs 4.8 Watts, or 1.6% of total power output. Meanwhile, a 50% stiffer crank absorbs 3.2 Watts, or 1.07%, in strain energy (technically, strain power). That’s a difference of 1.6 Watts (or 4.7 watts at our tested 880 Watts). And remember, this assumes that no strain energy is returned to the drivetrain. That’s not to say that crank stiffness is irrelevant, there is a measurable difference. It also provides all the psychological and “feel” benefits described at the beginning of this section. A stiff crank also incrementally improves efficiency by keeping bearings aligned, keeping the pedals more directly beneath your feet, etc. Keep in mind that this 1.6% calculated strain energy absorption represents an upper bound of energy dissipation—that is, the maximum possible energy loss due to crank flexure. Real cranks are much stiffer than our modeled crank and therefore store less strain energy. Moreover, a great deal of that stored strain energy is likely returned to the drivetrain. The real-world losses to crank flexure are, in all likelihood, a fraction of that number.
Things get slightly more complicated for carbon cranks. Composite materials really do damp vibrations better than most metals, and cyclists treasure this property to ease their stinging hands as they hammer over Belgian cobbles and hop curbs on their way to the local coffee shop. But damping is just another word for energy absorption, and a carbon crank certainly absorbs and dissipates more energy than a metallic crank. Modeling that dissipation requires, among other things, intimate knowledge of the crank’s construction (“laminate schedule,” in the argot of composites engineering) But even if we can’t quantify carbon crank losses due to damping, are they worth worrying about? Almost certainly not. They are a tiny addition to the already-small losses in a metallic crank.
Notes about Crank Length: Over the years a lot of different arguments have been made about the benefits of longer/shorter cranks. None of which has really been thoroughly tested until Jim Martins study. Martin showed that length didn’t statistically matter when it came to power, once power was averaged around the entire pedal circle and not just in the forward position, it turns out that shorter cranks (down to 145mm) produced more average power than a longer crank. This conclusion however considers only average power and not other factors which definitely have a bearing on real world use. Damon Rinard followed up the Martin study with some of his own testing comparing the aerodynamic differences in crank length. In almost every case there was an aerodynamic improvement with the shorter crank and without a loss in power. So the power advantage and aerodynamic advantage, combined with shorter cranks generally allowing for a more aggressive or more comfortable position on the bike and less chance of repetitive motion injury we feel that shorter cranks are something most people should consider. We’re not saying they’re right for everyone, but if you’re on the fence as to which size is best for you, we suggest that you go for the shorter. If you’re interested in more on crank length we suggest reading the above articles as well as this article written by Frank Day for USA Cycling.
Notes about weight: Some cranks claimed weights include rings and bb in their complete weights while others do not. To have a level and fair comparison all cranks in this test will be tested and weighed with their stock bsa bottom brackets, and any crank that does not include rings will use our Praxis rings and KCNC alloy chainring bolts.
Notes on prices: Prices are MSRP for the U.S. and include rings and bottom bracket.
We do plan on adding more cranks to the review as they are released and as testing is completed. In choosing the cranks to start the new review with we listened to feedback from previous tests. We went with the most popular cranks as well as some of the lightest options. One suggestion that kept coming up in past tests was that people wanted to see how an older square taper crank did, so in this test we’ve included one.
Note that in comparison to square taper all the external-cup type cranks are worlds stiffer.
Now Onto the Results
|Manufacturer||Model||Weight (g)||Price (USD)||Spindle (mm)||Average Deflection (mm)||S/W|
|Campagnolo||Record (2006)||894.7||Not current model||Square Taper||7.21||1.550|
|Campagnolo||Comp Ultra (2015)||669.8||1050||30||5.40||2.764|
|Campagnolo||Record UT Carbon (2014)||674.8||756||25||5.67||2.615|
|Campagnolo||Super Record (2015)||678.3||1165||25||5.5||2.680|
|FSA||Kforce Lite (2015)||672.3||699||30||5.42||2.747|
|FSA||SL-K Light (2015)||651.6||649||30||5.51||2.784|
|Lightning||Lightning Carbon (2015)||548.2||860||30||6.36||2.870|
|Shimano||Dura Ace 9000 (2014)||698.0||640||24||5.83||2.460|
|Thm||Clavicula Classic (2014)||540.8||1550||30||5.42||3.410|
|Thm||Clavicula M3 (2014)||579.9||1250||30||5.80||2.972|
** Fits only BB30/PF30 frames.
Graphs? Yeah, sure, why not?
Thoughts on Each Crankset
Campagnolo Record (2006) Square Taper Alloy
- Complete Weight: 894.7 Grams
- Price: Not current model
- Spindle: Square Taper
- Deflection-D: 8.18 mm
- Deflection-ND: 12.60 mm
- Average Deflection: 10.39 mm
- S/W: 1.076
The Campagnolo Record square taper crank was considered to be one of the top cranksets for many years. We’ve included it in this test just for comparison’s sake. The results were pretty dramatic, revealing the differences between this crank and all the other tested cranks. It was significantly heavier than all the other cranks and at the same time not nearly as stiff. This of course resulted in it having the worst stiffness to weight of any crank in the test.
Campagnolo Record UT Carbon (2014)
- Complete Weight: 674.8 Grams
- Price: $756
- Spindle: 25 mm
- Deflection-D: 4.3 mm
- Deflection-ND: 7.04 mm
- Average Deflection: 5.67 mm
- S/W: 2.615
The Campagnolo Record UT crank ranks better than mid-field in pretty much across the board. 10th out of 15 in terms of weight. 11th in deflection and 11th out of 15 in stiffness to weight. A nice looking crank with good shift qualities. BB variations in the past left something to be desired with the PF30 BB version having migration problems, but with the introduction of the Overtorque model this is no longer as big of a concern. My opinion of the non-standard bcd of the 5th bolt still hasn’t changed and I find it quite annoying, as it does seem to be more about removing compatibility with aftermarket rings than improving performance. Overall though this still a very nice crank.
Campagnolo Comp Ultra (2015)
- Complete Weight: 669.8 Grams
- Price: $1050
- Spindle: 30 mm
- Deflection-D: 4.15 mm
- Deflection-ND: 6.66 mm
- Average Deflection: 5.4 mm
- S/W: 2.764
The Comp Ultra is Campagnolo’s foray into a 30mm spindle crank and was done quite successfully. They opted to go with a universal 386 design rather than a restricted BB30. The Comp finished mid field in weight, slightly lighter than the other tested Campag cranks. In terms of deflection it was 3rd out of 15 which landed its stiffness to weight at 7th overall. The Comp Ultra has a wide range of bb options including bsa. The biggest drawback to it is that it doesn’t have the same simple installation as the UT cranks and does require special tools for installation and removal.
Campagnolo Super Record (2015)
- Complete Weight: 678.3 Grams
- Price: 1165
- Spindle: 25 mm
- Deflection-D: 4.1 mm
- Deflection-ND: 6.9 mm
- Average Deflection: 5.5 mm
- S/W: 2.680
We had hoped to see a bigger change with the new Super Record from the previous Record UT, but it just wasn’t the case. Weight, deflection and stiffness to weight were all almost identical to the results from the UT Record crank. This crank has a more polarizing look, for most people it’s either love it or hate it. The new spider and chainrings do however seem to make a difference in shift quality. So all things being equal this crank is an improvement.
Cannondale SISL2 (2015)
- Complete Weight: 609.4 Grams
- Price: $1185
- Spindle: 30 mm
- Deflection-D: 4.25 mm
- Deflection-ND: 6.91 mm
- Average Deflection: 5.58 mm
- S/W: 2.943
The SISL has been the most requested crank for us to test so needless to say we were excited to see how it would do. Of course we already knew the crank was light, at 609 grams it was the 4th lightest crank in the test. It was also on the top end of price spectrum. In terms of deflection it ended up just lower than the middle at 9th out of 15 which put its stiffness to weight at 4th. Having a shorter spindle than most other cranks in the test should have improved its weight, which it clearly did. The shorter spindle should also have resulted in better than standard non-drive deflection but in this case we didn’t notice that. The SISL2 is in our opinion one of the nicest looking cranks in the test, particularly with the tested spiderweb chainrings. However being that it is a true bb30 crank its use is restricted to frames with bb30 and pf30 shells only. We’d still love to see them do a 386 version.
FSA K-Force Light (2015)
- Complete Weight: 672.3 Grams
- Price: $699
- Spindle: 30 mm
- Deflection-D: 4.24 mm
- Deflection-ND: 6.6 mm
- Average Deflection: 5.42 mm
- S/W: 2.747
For the K-force Light we tested the 386 Evo version with a threaded bsa spindle, 386 has compatibility with every bb standard we can think of except for bb90. Overall the finish on the crank is very nice. In terms of weight it really wasn’t a standout being 9th out of 15. However this extra weight translated to extra stiffness. In deflection testing it finished 4th out of 15. That stiffness helped to lift its stiffness to weight ratio to 9th overall. Shift quality has definitely improved over the years as has the finish and build quality. Considering its $600 price tag ($699 with ceramic bb) and that it is also available in a Campag specific version, it’s definitely a well rounded crank.
FSA SL-K Light (2015)
- Complete Weight: 651.6 Grams
- Price: $649
- Spindle: 30 mm
- Deflection-D: 4.33 mm
- Deflection-ND: 6.7 mm
- Average Deflection: 5.51 mm
- S/W: 2.784
The SL-K takes the K-force up a level. Being 20 grams lighter the SL-K was the 5th lightest crank we’ve tested so far. Deflection suffered a little from the K-force putting this one at 8th out of 15. Overall stiffness to weight ratio was up to 6th overall. Same nice build quality, good selection of lengths (165+) and good looks as the K-force and with rings that shift very well. Also like the K-force this SL-K is a 386 Evo standard which gives it compatibility with just about every bottom bracket standard on the market.
Lightning Cycle Dynamics (2015)
- Complete Weight: 548.2 Grams
- Price: $860
- Spindle: 30 mm
- Deflection-D: 5.5 mm
- Deflection-ND: 7.22 mm
- Average Deflection: 6.36 mm
- S/W: 2.870
While this current Lightning crank may look the same as past versions there are definitely some differences with it. Surprisingly when looking at just arms/spider, this is the lightest crank in the test. In the past it was close to the Clavicula weight but we’d never seen it dip under. This version is 6 grams lighter than the THM. However the THM is lighter as a full system because the bb is lighter. But with other cups than the BSA (as tested here), this would be the lightest. The weight savings does come at the cost of stiffness though, with the Lighting being the least stiff (with exception of the square taper Campag) but not by a large margin. The crank is quite light though which gives it the 5th best stiffness to weight ratio of all tested cranks (though two that finished ahead of it are BB30 only). BB options are as wide as a 24mm crank: BSA, Italian, BB86, PF30, BB30, Bbright, BB386, and even BB90. Crank options are also the most plentiful of all tested cranks. Matte or gloss, with or without logos and a variety of arm lengths from 160 up to 190.
Praxis / Turn Zayante (2015)
- Complete Weight: 828.8 Grams
- Price: $349
- Spindle: 30 mm
- Deflection-D: 3.96 mm
- Deflection-ND: 6.17 mm
- Average Deflection: 5.06 mm
- S/W: 2.383
The Turn Zayante crank finished the test as the heaviest of all current cranks, but also as the stiffest of all current cranks (with universal fit), and by a respectable margin. Part of the added weight comes from the substantial BB which promises to be extremely durable. Overall this is a very well thought out crank and one that we’d definitely consider as a top choice for training/daily rider crank. Good looks, great shift quality and solid function at a very respectable price. The results of this one make us look forward to what Praxis has planned for their top end crank which we hear will be coming eventually.
Shimano Dura Ace 9000 (2014)
- Complete Weight: 698.0 Grams
- Price: $640
- Spindle: 24 mm
- Deflection-D: 3.98 mm
- Deflection-ND: 7.67 mm
- Average Deflection: 5.83 mm
- S/W: 2.46
For many years Dura Ace cranks have been considered the pinnacle of cranks. That may still be the case when it comes to installation, reliability, finish and shift quality. However in the metrics we were measuring in this test the DA 9000 crank fell just short of mid field. 12th of 15 in total weight, 11th of 15 in deflection and 12th in terms of stiffness to weight. The best thing the DA crank has going for it is unrivaled shift quality, which is arguably quite important in a crankset. However it does suffer by adhering to the (now quickly disappearing) 24mm spindle size, and the lack of stock BB options (though aftermarket options are plentiful.) We’d love to see a future update of this crank with a 30mm spindle. The spindle diameter shouldn’t be underestimated. If you look at the drive side test, this crank is the 2nd stiffest of all tested. However when you look at the non-drive side it’s the worst of all the current cranks we’ve tested (excepting the 2006 square taper.)
Specialized SWorks (2015)
- Complete Weight: 663.2 Grams
- Price: $665
- Spindle: 30 mm
- Deflection-D: 4.26 mm
- Deflection-ND: 5.75 mm
- Average Deflection: 5.01 mm
- S/W: 3.013
The Sworks crank has done very well in testing. Like the SISL2 the shorter spindle of this crank should help to keep the weight down as well as improve the non-drive side stiffness. In terms of total weight it hits 6th out of 15. Its real quality though is in its stiffness with the best total deflection of any crank we’ve tested to date (as expected it did very well with nds deflection being the only crank to drop below 6mm). Mix those two attributes and the stiffness to weight ratio is great coming in 2nd out of 15. Shift quality is not the best of all the tested cranks but is certainly more than adequate. Finish is very nice as is installation and its unique preload adjuster. The biggest drawback with this crank is the restricted use to only bb30 and pf30 frames. Given its $665 price tag it could be a pretty popular aftermarket crank if it were available in a 386 version.
SRAM Force22 (2014)
- Complete Weight: 782.3 Grams
- Price: $390
- Spindle: 24 mm
- Deflection-D: 4.32 mm
- Deflection-ND: 6.99 mm
- Average Deflection: 5.65 mm
- S/W: 2.261
The Force 22 crank is more than 100 grams heavier than Red22 and we expected that to translate into increased stiffness
but in fact it ended up less stiff than the lighter Red22. 10th out of 15 in stiffness and 13th in terms of weight put the
stiffness to weight near the lowest of all the current modern cranks in the test so far. That said, it is still
significantly better in every category than the traditional square taper. It is a good looking crank, better than Red22 in our opinion, but with it being only slightly less expensive we feel the Red22 would be a better choice for most riders looking for a SRAM crank.
SRAM Red22 (2014)
- Complete Weight: 667.4 Grams
- Price: $490
- Spindle: 24 mm
- Deflection-D: 4.08 mm
- Deflection-ND: 6.8 mm
- Average Deflection: 5.44 mm
- S/W: 2.754
SRAM’s flagship universal fit crank Red22 comes in as one of the lighter cranks in the test, 7th of 15 and 6th in
deflection which puts its stiffness to weight right in the middle at 8th. Good shift quality, light weight,
reasonable stiffness, wide selection of stock and aftermarket BBs, and the best price of any flagship model in the
test–to us that means that this could be one of the most well rounded cranks available and a good fit for many
riders. The hidden bolt design does restrict some aftermarket chainring compatibility, but overall SRAM has to be
considered as a serious contender with this crank.
THM Clavicula Classic (2014)
- Complete Weight: 540.8 Grams
- Price: $1550
- Spindle: 30 mm
- Deflection-D: 4.39 mm
- Deflection-ND: 6.46 mm
- Average Deflection: 5.42 mm
- S/W: 3.410
THM’s Clavicula is now in its 10th year of development and refinement, and it shows. 1st in weight, 5th in stiffness
and 1st in stiffness to weight. Of course that performance comes at a cost, and in this case that cost is not
insignificant. Great aesthetic qualities and a wide range of BB choices (everything except BB90). It does lack in
length options being available only in 170, 172.5 and 175 but given that those are the sizes most people ride it
definitely covers the largest percentage of users. In recent years the weight limit has been increased to 231 pounds
which should cover most riders.
Thm Clavicula M3 (2014)
- Complete Weight: 579.9 Grams
- Price: $1250
- Spindle: 30 mm
- Deflection-D: 4.65 mm
- Deflection-ND: 6.96 mm
- Average Deflection: 5.80 mm
- S/W: 2.972
The Clavicula M3 is a newer model than the Classic, designed to be a little heavier and a bit more modular in its
design. 3rd in total weight and 3rd in stiffness to weight (with one ahead of it being a bb30) puts this up with the
best cranks. Unlike the Classic, the M3 uses a removable spider that can be swapped from standard to compact as well as
SRM Powermeters. It has a narrower q-factor than the Classic and a higher weight limit (242 pounds). Its alloy
spindle also gives it more flexibility in BB choices including direct fit plus a lower price, though the M3 is still one of the
most expensive cranks available.
Now that you’ve gotten through the entire test, or skipped to the end, we suppose you’re looking for a summary. Well, we aren’t really going to offer much other than to say that when it comes to cycling there really isn’t a universal best. There is a best for a given set of circumstances. Each rider has to decide the aspects that are important for them and their needs, be it weight, aesthetics, price, size, BB compatibility etc… Hopefully we’ve provided enough information to help each rider determine which crank is best for them.