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Wind Tunnel Time: Is the Wahoo ELEMNT BOLT actually the fastest bike computer?


When it comes to companies making marketing claims about all sorts of devices, most shy away from specifics.  They’ll use terms like ‘better than’ or ‘faster than’ – without numerical qualifiers, or they’ll use other terms that imply greatness but stop short of giving you concrete details.  In most cases, that’s because it protects the company in case someone finds a way to call them out on being incorrect.

So when Wahoo made two specific claims upon launching the Wahoo ELEMNT BOLT earlier this year, I immediately started plotting on how to put them to the test.  Specifically, they claimed two core things:

A) The BOLT was the fastest bike computer against the “leading competitor”

B) The BOLT would save you “12.6 seconds in a 40KM time trial”

Those were pretty specific claims, which can be found on their website and in a slightly more detailed blog post of theirs:




The above screenshots were taken on May 4th, 2017, though the wording Wahoo has used has remained consistent since launch in numerous documents (their website, press releases, media kits, etc…).

Wahoo argues that their new mount is designed for the BOLT and thus designed to be more aerodynamic out of the gate.  So this is as much a test of the entire mount/computer as it is of anything else.

The real question is – is all the above true?  Well, I set to find out.  On the way to the annual Sea Otter cycling event this year I took an early exit off the highway to hit up the Specialized Wind Tunnel.  We’d test all the most popular bike computers out there and see if the claim holds true.

The below video covers everything from end to end: What we tested, how it was tested, and the results.  It’s like this entire post in one nifty audio video extravaganza:

Video not your thing? No worries, continue on!

The Win(d) Tunnel:


As noted above, the test was done at the Specialized Wind Tunnel, about an hour south of San Francisco.  Technically it’s called the ‘Win’ tunnel, and not the ‘Wind’ tunnel…but…ok.  This is actually the second time I’ve been to the tunnel; the first was about 18 months ago when I did a similar spate of tests.

In that previous visit, we tested a pile of bike computers and action cameras, as well as mounts – looking to see how they tested out aerodynamically on your bike.  We even tested my normal power meter accuracy testing getup – with four bike computers and an action cam!

Rather than re-doing the massive behind the scenes section I did within that post, I’ll just refer you to that bit of awesomeness here.  I cover how the tunnel works, and all the coolness within it.

IMG_8022 IMG_8026

IMG_8048 IMG_8044

Very little has changed since then in terms of the tunnel itself – so all of that still applies here.

Do note that in the case of Wahoo’s claims, they actually didn’t test in a tunnel. Rather, they worked with Dimitris Katsanis of Metron Advanced Equipment to perform the tests within computers using CFD (Computational Fluid Dynamics).  There’s nothing wrong with that per se, but the reality is that it’s not…well…real.  Metron’s own site explains a bit on how they do this.  Which isn’t to say it’s not valuable – it certainly can be.  But since Wahoo paid Metron to do these tests, that makes our visibility into those results limited to what Wahoo decided to release.

The Test Setup:


At the media event back in March they noted that the ‘leading competitor’ was a Garmin device, but didn’t specifically call it out at the time.  So in order to ensure I covered all the possibilities, I brought a crapton of units into the wind tunnel:


Prior to doing the test we didn’t know that the results were based on the ‘stock provided’ mounts, meaning the things that came in the box.  This meant either the out-front handlebar mount or the rubber-band mount (such as on a bar stem).  So we brought all of those too.


In total the following units were tested, all with their stock mounts:

Garmin Edge 520
Garmin Edge 820
Garmin Edge 1000
Polar M460
Polar V650
Stages Dash

In the case of the Edge 520, we ran tests on both the stock out-front mount as well as the rubber band mount attached to the stem. Again both in-box.  In the case of the M460 and V650 from Polar, we used Polar’s new metal out-front mount.

Next, the bike. Specialized provided the bike, which was set up to be pretty darn aero.  The components are listed in the report from Specialized below:


Then there’s the on-bike and tunnel setup.  Prior to starting the test, we did three runs of the bike in the tunnel without any bike computers on it.  This was to ensure a consistent baseline and that the tunnel had stabilized.  The platform that holds the bike automatically moves to provide a number of yaw angles during the test.  Each test run includes tests at the following yaw angles: 10°, 5°, 0°, –5°, –10°.  Yaw angle means how offset the bike is compared to the headwind.  This nifty little 46-second video from last time shows how the whole thing moves:

For all of the bike computers, we placed them at 0° to the ground, meaning perfectly horizontal.  If you remember back to last year’s post on this, it was actually a really big deal that the units were flat.  When tilted upwards, it was a huge penalty in terms of aero.  We initially wanted to use a physical level to do this, but the smallest level we could find was a meter long, making it impossible to use on the bike mount.  Instead, we just used a phone app (which we double-checked against the physical level too).


In the case of the Wahoo ELEMNT BOLT, we actually did three tests:

Test 1: Wahoo BOLT at 0° flush
Test 2: Wahoo BOLT at 6° up
Test 3: Wahoo BOLT at 0° flush (again)

We did the last test at the end of all testing, just to ensure the results were consistent.  Again remember that for each bike computer we did multiple yaw angles (to simulate a crosswind).

Finally – some will ask why we didn’t use a rider.  The reason is simple:  The tolerances/differences we were looking at here are just so darn small that adding a rider wouldn’t likely be consistent enough test to test to ensure valid results.  Further, in the case of this specific test (an out-front mount), a rider is unlikely to impact the test results.  Whereas if you were testing helmets or some other component of the bike closer to a rider, it may.  Additionally, a rider would likely impact all these items equally, so it would cancel out.

Also – we didn’t spin the wheels (though it’s possible).  The reason is that doing so would reduce the accuracy of the test data, as it impacts the force sensing plate a bit.  Given we wanted the most accuracy possible and given it would likely have no impact between each of these units – it was excluded.

The overarching theme to remember coming out of the setup section is this: The differences between each mount were expected to be incredibly small, and thus we needed every last ounce bit of accuracy in the ‘full tunnel system’ in order to measure them.

The Results:


Since watching wind move through a tunnel is actually really boring (Pro Tip: You can’t see anything), we’re going to jump straight to the results.

First up is how each unit fared compared to the bike by itself.  The taller the graph column, the more drag the computer is producing (increasing CdA – the Drag Coefficient and Area).  But really – do keep in mind that these differences are astronomically small:


So as you can see right off the top of the bat – the Wahoo BOLT is actually imparting the least amount of additional drag over the base bike alone.  So, that’s a good start to their claims about being faster than the competition.

Speaking of which – going into the tests we didn’t actually know what exactly the competition was.  When I had asked various Wahoo folks previously, they declined to provide an exact model.  But after the test I followed up again and got them to spill the beans and confirm it was indeed the Garmin Edge 520 in the stock (provided) out-front mount configuration.

Notable take-aways from the above chart is that the Edge 1000 is the slowest (something we somewhat already knew from last year).  Also, you see the rubber-band Edge mount configuration on the stem is actually faster than the out-front mount.  This is because it ‘hides’ behind the stem a little bit, taking it out of the wind.

So let’s dive into the main claim – which is that it was 12.6 seconds faster than an Edge 520.  The below chart compares everything against the baseline of the Edge 520 with an out-front mount at 0-degrees flat (shown below in the center-right at ‘0’):


As you can see, going back to the bike alone would have saved you 3 seconds.  And swapping the Edge 520 out for the Wahoo ELEMNT BOLT? That’d have saved you 1 second.  Putting the Wahoo ELEMNT BOLT at –6° instead of the Edge 520 flat? That’d have cost you 3 seconds.

And this gets to the meat of their claim: Yes, the Wahoo ELEMNT BOLT is faster than the Edge 520…but it’s not 12.6 seconds faster.  It’s 1 second faster.

In discussing this with Wahoo a bit more after the test, they pivoted slightly to claim that it was really the Edge 520 at 6° up versus the Wahoo BOLT at 6° up.  Their thinking being that most people turn up their bike computer mounts to make it more readable (which is true), and that the BOLT is more readable at 6° up while also being just as aerodynamic.

And in fact, there’s some truth to that second claim.  For example, you can see that the BOLT tested at 6° up is equal to that of the Edge 820 while flat.  And we know from last year that increasing the drag upwards could see 4-8 seconds of increased time (or decreased, depending on how you look at it).


But really – all of this sidesteps something that a few people have wisely brought up: It probably doesn’t actually matter.

Why’s that?!?!

Well, because quite frankly nobody is doing a time trial on a road bike.  They’re doing them on time trial/triathlon bikes.  And those have a dramatically different set of conditions.  Even further – Wahoo doesn’t even make a BOLT aero-specific time trial bike mount for its computer.  So in many ways all of this is for naught.

Which isn’t to say there aren’t aero advantages on a road bike, of course there are. But as most of us know, it’d be incredibly rare for this to make any meaningful difference in a road race given the dynamics of pack riding.

Further – the differences here are really just very very small.  I wouldn’t get too caught up in one unit being a few seconds between the Edge 520 and Wahoo BOLT.  And even if you compare against the Edge 1000 or Stages Dash (closing in on 10 seconds slower) – you end up back in the same conundrum of whether or not it matters in a road race.  But, that’s for you to decide.

To Wahoo’s credit, it is clear that if you tilt up your bike computer – then the BOLT does indeed save a fair bit of time.  There’s very little penalty on the BOLT for doing so, whereas we know from last year it’s considerable to do so on the Edge (or any other bike computer).  Their integrated mount system and overall design does seem to help considerably here.

With that – hope you enjoyed!  And thanks as always to the Specialized crew (Cam Piper in particular) for their time in letting me take over the wind tunnel for a morning.  Their playlist here of all their test videos is awesome for aero geeks.  Further, you can find the full PDF report here with all of the data in it, as well as below in a mini-gallery:

(P.S. – In case you’re wondering why we did or didn’t test XYZ bike computer as well, this was mostly about choosing the most popular ones out there, plus some uniquely new ones I just happened to have with me – like the Polar M460 and Stages Dash.)

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  1. Andre Lemos

    Fasted is right! Not sure if pun, or typo 🙂

  2. Adriaan

    So, at the end who won the tunnel? Was it Dire Straits with the Tunnel of Love?
    I was wondering if you could do similar test with wet suits. We can call it Float in Moat…
    Seriously. How much seconds will save you a 1000 EUR wetsuit vs 150 EUR wetsuit on an Ironman distance of 3800m.

  3. Tim Grose

    Very very marginal gains then! Not surprising but nice to know there is not much to worry about here. I can see you losing that one second should you want to change the screen you are looking at. Also if you are on a course you don’t know and don’t have a map view to hand then those 10 secs might be lost very quickly… There are some road bike TTs – indeed I was talking to the organiser of one just yesterday and there times in many group rides/races where you might “TT” for a while to get chase back on or zip off the front. Rarely 40K though.

  4. Bob Goodman

    Great article! This should be the start of a series of articles testing the many claims various manufacturers have about cycling products.

  5. Chris

    Where did you get that shirt? Did you release this on May the 4th on purpose?

  6. Thijs Rieken

    Testing claims like a boss! I really enjoy and applaud this particular angle of testing. It’s a bit like Mythbusters, or our Dutch program “Keuringsdienst van Waarde”, who set out to test claims and commercial lingo, like what does “natural flavor” actually mean (quite disturbing episode).

    I would like it if you would feature this kind of article more often. This one was great 🙂

  7. Morgan Styer

    Is it reasonable to assume that a Garmin 520 on a K-Edge mount that places it in front of the bars instead of elevated like the Garmin stock mount would be even faster?

  8. likepend1

    So that means i have to invest into a BOLT to be home 2s faster from my 80km ride (& 5k bike). sounds reasonable.

    thanks for doing those tests!! love reading them!

  9. Ian S

    Excellent!!! I’ve been wondering how tangible the difference was ever since Wahoo launched. Thank you for quantifying, great read.

  10. Like 99% of the world, I think I’d save more time off a time trial by eating one less snack. Sigh.

  11. legstrong

    This is a great effort to prove manufacturers’s claims. These days many manufacturers claim this and that without any test results backing them up. Even if they did, they were done in a much controlled environment.

    My concern though, was the iphone the only angle meter used in the study? I had an experience using an iphone (never dropped) for that purpose and I found out that it was off ±2° max. I use a digital angle meter since then (double check with an analog one if precision is critical). In this case, precision is a must.

  12. Liam Nicholson

    After watching the video, it looked to be as much of a test of mount design/aerodynamics as it did of computer aerodynamics.

    The Wahoo was sitting in front of the stem, whereas other brands were often mounted proud above.

    The stock Garmin mount is awful. An edge unit on something like a K-Edge out front mount would be a whole different ball game.

    Wahoo’s claim is very shaky, and I suspect plainly false once mounting has been controlled for.

    • Remember that Wahoo specifically designed the BOLT mount to be more aerodynamic, so that’s as much a piece of their product line as the computer itself. Other companies are free to do so.

      Of course, if you were to test on some random 3rd party mount, you’d likely get different results. But that’s not what Wahoo is claiming, and thus less interesting.

    • Liam Nicholson

      I semi agree.

      Obviously there is a valid point to be made about Garmin etc lacking in the mount design sept.

      However, I think that the real consumer interest here is which computer to buy if they want to be as aero as possible.
      Putting aside the point that it’s unlikely to make a difference anyway, surely there is value in testing these computers in a configuration which an aero weenie would find acceptable?

      I’m relatively (but not massively) aero conscious with my cycling. I took one look at the standard mount that came with my Edge 1000 before going online and buying a K-EDGE

    • Paul S.

      But clearly the answer is “none”. If you’re really an “aero weenie”, don’t use a head unit.

  13. Steve

    Ok so a more aerodynamic head unit/mount causes less air resistance I get that … but you say the rider makes no difference, I challenge that. Without a rider yes the units will affect airflow past bike differently, but if a rider is on bike that’s a far larger object on the same airflow direction/path which has to cancel out any gains at the middle of the handle bars?
    So only real test is to have a perfectly static body (so consistent between tests) ie dummy on bike to see real affect of airflow.
    But then again there are far more important things to worry about 🙂

    • Su-Chong Lim

      I have to agree with Steve. The testing of the small differences in drag from a computer mounted in line with and ahead of where the rider would be, but who was not actually there during the test would be meaningless to a real life situation. The small efficiencies in decreased drag when testing in isolation with no rider are achieved by decreasing frontal area and by smoothing out the turbulence and minimizing the region of decreased pressure behind the computer.

      All this becomes problematic when you compare the real effect you want to measure — the increment if any of drag from the addition of the various computers mounted in front of the rider (who would have a huge CdA in comparison to the CdA for the computer). In effect you start with the known CdA for the rider, and see how a given front mounted computer changes it. Conceivably, a poorly rated (when tested in isolation) computer might enhance i.e. decrease CdA of the Rider + Computer Unit by helping to smooth out air flow in front so the flow is more laminar around the rider. and behind, or at least increase the CdA by the lesser amount.

      I’m not sure the lowest drag for a computer when tested in isolation means anything or if the data can be extrapolated at all to help a decision regarding the real-life (with rider) situation.

    • The rider would have likely impacted an equal difference across all units in this case, but would not have been consistent enough for us to make any determinations for certain.

      The study I linked to talks about this in detail actually for this portion of the bike.

      Moreover though, I find that when I’m working with folks who spend their life in wind tunnels (as Cam and others do), they tend to know most about testing gear in the most accurate way possible. Between the two options of having a rider there would undoubtedly would not have been perfect enough, or having no rider but getting perfect data. Seems pretty obvious…

  14. Sebastien G

    It would’ve been nice if you had included the original Elemnt, but interesting nonetheless.

    Thanks !

    • Yeah, I actually had it on the table to bring with me before I left for my now 3+ week trip. And then as I was packing everything up later that night I stupidly removed it (along with a few other things I wanted to test). Was tired and couldn’t figure out why I had set it aside.

  15. tim

    where can I buy one of these new aero rubberband mounts?

  16. Wahoo’s claims are inconsistent. Image 2 says it will save time in a 40k TT @ 21 km/h, where image 4 says it’s at 21 MPH. I’m sure it’s a minor mistake, but it gave ME a double take. At 21 km/h you could be riding with a cow on your back and it would have little-to-no aerodynamic effect!

    • Andrew

      And a 40km TT will always take the same amount of time at 21 whatevers/hr…

      Ray you say “saves one second over a 40km TT”. What is the other variable? I presume at a certain wattage.

    • Phil

      You’re missing the point: they are being inconsistent. And when it comes to tech, a company ought to be fastidious.

  17. Even discounting the factor of the tilt, I’m confused by the speed used in testing. If Wahoo claimed 12.6 seconds saved over 40km averaging 21kph and the Win Tunnel results claim 1 second saved over 40km averaging 50kph, they don’t necessarily contradict each other. The longer the time it takes to complete the 40km, the more time you are going to save from decreased aero resistance. Combine that with the tilt, and it is possible that its actually more than their claimed 12.6 seconds. Perhaps someone more knowledgeable than me can calculate what the results mean if slowed down to 21kph instead.

    • Keith Wakeham

      Except that drag calculations for aerodynamic power is to the power of 3, so the slower you go the effect becomes more and more negligible. So if you half the speed (0.5^3), the effect is 1/8th, so it drops from 12.6s to 1.575s advantage, but now over twice as long you get 3.15s… for double the time. Exponents!

      This math is exponentially more fun the faster you go. This is also why a car can do 300km/hr with < 300hp but to do 400km/hr it needs over 1000hp normally.

  18. Tom

    You also debunked a third alt-fact from their marketing material:

    “If you tilt the ELEMNT BOLT (not that you need to because of its curved design) the air resistance does not change or affect the overall performance.”

    Your data shows otherwise. Tilting the Bolt from 0 to -6 deg added more drag than the device at 0 deg alone.

  19. Greg Franks

    If you collected data over 30 seconds and used the average, then you could also calculate the variance and find the confidence intervals of the results. I don’t want to rain on your parade, but perhaps it’s all statistically insignificant. However, I do believe you can conclude that Wahoo’s claims are busted. Now, does something blow up?

    • That’s already done. 😉

      Each yaw angle is held for 30 seconds.

    • Wolfgang

      Look at the bar charts, the confidence Intervalls are there…
      OMG you guys really think you are smarter than the Specialized guys working the wind tunnel every day?!?
      Go get a life…

  20. Andrew

    ‘Nobody is doing time trials on a road bike’

    I must be imagining my clubs road bike only tt series then? Flippancy aside, my experience of time trials is that there are at least as many, if not more, road bikes than tt bikes at club level mostly due to affordability/ease of use.

    Not that i actually think getting a more aero computer is of any importance in this scenario, but i felt the above statement to be very fair!

  21. Nic Zuraw

    Faster still with it in your back pocket!

  22. Eagle Jackson

    I have a Bolt. I really like it. It’s replaced the Garmin Edge 520 and 820 I have. It’s just a nicer bike computer to use than the Garmins. Setup is a breeze, the buttons work great (820 touchscreen is awful imo), and it is reliable (Garmin sw quality is notorious). Using the smartphone for setup dramatically simplifies and cleans up the device UI. The included out-front mount is very nice, too — I like it better than the K-Edge and Barfly I have.

    I don’t quite understand why Wahoo is anchoring its marketing around aero. The aero claims are at best a stretch; they just don’t pass the smell test and your review confirms how flimsy the claims are.

    It’s a great bike computer. I hear it’s selling very well. It is probably making Garmin nervous.

    There’s so much to like about the Element Bolt. So why market the least believable thing about the device?

    • Ross

      I couldn’t agree more. This is a marketing issue more than anything else. Don’t buy a Bolt for aero benefit. Buy it because it is the most intuitive, reliable, and thoughtfully designed bike computer on the market. The software is robust, but incredibly simple to use. It reminds me of the first time I used an iPhone. Wahoo should focus on these points rather than questionable aero data.

    • Eagle Jackson

      Yes it’s all that — in a great sized package. The original Element was just too big; the Bolt is about 520/820 size and that’s a winner. I guess Wahoo couldn’t figure out how to make the message of “most intuitive, reliable, and thoughtfully designed bike computer in a great sized package” stand out and grab your attention. Their “aero and performance” message might stand out but it’s not particularly credible.

      I read a comment similar to your a couple of weeks ago that said, “If Apple were to design a bike computer, the Wahoo Element Bolt is it.”

      They really did a nice job with it and their introduction of increased features at a rapid (while still reliable) pace is impressive. (My Garmin surely would have bricked multiple times with so many rapid updates).

      There are lots and lots of reasons to buy a Bolt. Aero ain’t one of them.

  23. Antonio Bošković

    so i’ll just make suremy humble polar m450 is perfectly level and save ton of money

    • Ross

      Well, a new buyer wouldn’t be saving much. Out-front mounts aren’t free and are not included with the m450/m460, as they are with the Bolt.

  24. Slartiblartfast

    Unfortunately the post test conversation with Wahoo means that to verify their aero claim it would be necessary to go back and test the Wahoo Bolt tilted 6 degrees vs the Garmin 520 tilted 6 degrees.

    • We know from last year that the difference between tilted and non tilted isn’t 12.6 seconds, but in the case of the much less aero Edge 1000 was about 4-8 seconds.

      I do agree that in a best case scenario we’d have known to do that side by side. But of course, Wahoo’s claims on their site say nothing about that…which is kinda a really important thing to note.

  25. Jac

    Love the post! Really interesting collection. Would love a follow up to see if the theoretical results pan out in the real world. i.e., do you actually get those seconds theoretically predicted or are the benefits so far in the noise that they don’t give any actual advantage. That’s my hunch based on the relatively small magnitude of change.

    If there are any Specialized folks monitoring the thread, would like to get some clarification on the bow wave. I don’t doubt their assessment that it is negligible in his case, but the article looked like it attributed most drag to vortices caused by flow separation off the hips. Very cool study…especially since I’d be one of the AIAA geeks in the target audience. How far ahead of the rider are now wave effects seen? Is there any area of the bike where this dominates over equipment drag? Just a very interesting topic.

  26. Dimitris Katsanis

    By Dimitris at Metron A.E.

    To start with, I am quite happy that the general prediction from the CFD that the ELEMNT BOLT computer is better than the competition, holds true.
    I would say that the general setup used in the wind tunnel testing was good and most of the differences come from the different setups between CFD and wind tunnel.
    I hope the following can help clarify where the differences come from.

    Engineering approach.
    The approach by Metron and Wahoo was to deliver results that are relevant to the average customer who is purchasing a cycle computer.
    So, 21Mph was the speed that results were reported from the CFD as opposed to 31Mph (50Kph) used during the testing at the Specialized wind tunnel. 31Mph is an average speed that a World Class rider can achieve which is way beyond most of us.
    Regarding the inclination, actual measurements indicated that users were positioning their computers on an average inclination of about 6 degrees, primarily to improve readability. Therefore, 6 degrees is the reported angle, not flat.
    Please note that both speed and inclination have a strong effect on time savings.

    Aerodynamic testing.
    Metron works with world leaders in Computations Fluid Dynamics (CFD) to deliver aerodynamic performance improvements to its customers. Our experience shows that the general trends predicted by CFD do hold true when tested in a wind tunnel, while the magnitude of the improvement may vary. So, if CFD say that there is an improvement, you got one.
    Please keep in mind that you will always have differences between CFD and wind tunnel testing. As you will have differences between different setups e.g. the same computer but with different stem or handlebar behind it, will give different results.
    Each method (CFD Vs Wind tunnel) has its pros and cons as well as its limitations. Also, different wind tunnels as well as different CFD codes, will give you slightly different results.
    Aerospace and F1 are big users of CFD and it is accepted as a reliable development tool.

    The effect of tilt
    As said before, 6 degrees was used as it is a realistic tilt. In this case, the bulk of the wind tunnel tests were with the computers flat. Only the ELEMNT BOLT was tested at 6 degrees and again it was found, as CFD predicted, that the penalty was very small Vs the flat position.
    When testing the computers flat, (mounted on an up-front position), this will naturally give the lowest drag for each computer, therefore it diminishes the advantage that the ELEMNT BOLT has in the real world. DC Rainmaker admits that in a previous test “When tilted upwards, it was a huge penalty in terms of aero”. You will therefore expect that if the rest of the computers are tested in the more realistic, slightly inclined position, the ELEMNT BOLT will extend its lead. How much? About 4 to 8 seconds according to the text.

    The effect of test speed
    This is a peculiar one and it took me several attempts to understand it initially. In simple terms, if you get, say, 10% improvement in the time to cover a set distance at a set speed, when you are going slower, that 10% equates to a larger number. In other words, if it takes you 100 seconds to cover a distance then your 10% gain is 10 seconds and if it takes you 200 seconds your 10% gain is 20 seconds.
    In this case, the difference in speed is about 30% slower (World class Vs average customer), i.e. spending about 30% more time on the road, therefore increasing the gain by that amount. This will be true to an extent, because you will have Reynolds numbers effects kicking in if the speed difference is too great. (Note: the drag coefficient, in general is increasing when the Reynolds numbers [in simple terms: speed] are going down)

    Adding up
    Adding these effects together (tilt plus lower speed plus increasing drag coefficient) and based on the findings of this test, as well as the mentioned ones about previous experiments with tilt, the CFD prediction of about 12.6 seconds faster is close to what wind tunnel is telling us.

    TT and road events
    The results will hold true for both road and TT bikes. I cannot see why a rider on a road bike will want to carry extra drag.

    I always try to equate this to pulling a parachute behind you. O.k. in this case it is a pretty small parachute, about the size of a postage stamp, but would you do it?

  27. Robin Perkins

    All this doesn’t make much sense to me. The aero differences in bike computers is such a small factor, the time savings claims are not believable. What really counts is mostly the rider and then the bike.

    • likepend1

      & the clothings! Huge factor!!

    • Phil

      Is it? All bikers clothing looks the same to me. Just a different print. I would presume there is hardly any difference between Alexander Quintana his jersey and the outfit from Wout Poels.

    • Clothing makes a huge difference in a time trial, less so in a road race where pack dynamics are more important.

    • Robin Perkins

      Yes, Buy say “Rider” I meant everything the rider wears. Shoe covers would make more difference than the computer.

    • True, it likely would. But the goal of improved aerodynamics shouldn’t be either/or, but rather ones hope to make as many adjustments as possible to reduce drag.

      Now if Wahoo had a TT variant of the mount, then the conversation would be more intriguing.

    • Phil

      Comparing a TT versus a road race will surely make a difference. But is there a difference in comparing one TT riders’ clothing versus another TT riders’ clothing? One would presume not, hence my previous assumption (Quintana vs Poels – or whoever, point being two riders in the same race).

    • It’s hard to say, I’m not sure how much public data is out there on that. Certainly many teams to go both wind tunnels as well as places like ERO sports* to test out their kits.

      Btw, I found one of the older Specialized videos on aero gains with clothing: link to road.cc

      *Link: link to dcrainmaker.com

    • Phil

      1) thanks for linking those articles, took a gander and am going to read them both now.

      2) I understand there’s a difference (an aero difference) between the type of clothing. But if all riders have ‘the same’ clothing there wouldn’t be ‘any’ difference. That was my point.

      3) So, ≈ 37kph on the track: you go sir!

    • Yeah, was trying to find some data links on different TT clothing, but couldn’t easily do so.

      That said, if you’re on Slowtwitch, you could probably post there and my bet is that Jim from ERO sports would likely be able to give some general comments on what he’s seen with pro cycling teams coming through there (most in their TT setups), with respect to clothing.

      Here’s his Slowtwitch handle page, which you might be able to dig through and find some posts he’s commented on that may include it: link to forum.slowtwitch.com

  28. oTTo

    Finally one smart comment by Robin. This is /was simply waste of time. Other then commercial no real benefit.

  29. Very interesting contender (and very often used in the peloton) would be SRMs Powercontrol (PC8).

    • Phil

      Excellent point! Finally someone pointing to the PC8 by SRM. So many use it in pro cycling, yet we hardly ever read an article about that device. Why is that?

    • “So many use it in pro cycling, yet we hardly ever read an article about that device.”

      Because almost no real-world people actually buy it (and I think I only got two reader requests in all of 2016 to test it).

      As for including it in the testing, I did make a last minute attempt to see if a few folks in the Bay Area had one handy, but it was very last minute. Would have loved to test it – as the design isn’t unlike the Stages Dash.

    • Phil

      I indeed hardly ever so someone with that PC8. It’s a bit more expensive than a ‘regular’ Garmin, but price never stopped anyone from buying what they want. I wonder if its lower marketshare, an assumption in and on itself on my part, is due to marketing.

      Not seeing many articles on the device wasn’t limited to your website, I merely meant I haven’t seen that many articles on web.

    • I think the PC8’s challenge is that it’s in a tough fight. It’s priced much higher than competitors units, without any tangible reason for it.

      It used to be (like, 5-8 years ago), that folks went for the SRM head units due to better stability and not losing data. But these days, folks just aren’t losing workouts on Garmin/Polar/Wahoo/whatever head units. They haven’t for the better part of this decade. So that reasoning goes away. And of course, it doesn’t compete on features either these days.

      I suspect other media outlets are a lot like here: They want to write about things folks show interest in. Where there’s enough demand, then entities would write about it too. And being priced where it is, it removes many of the ‘impulse’ buyers and subsequent reviews/etc…

    • Phil

      Those are all excellent points!

      Indeed, the unit is quite old. People want the latest, if only for buying recent technology.

      I wouldn’t know on Polar, Wahoo, … but I do know, from my own experience, the head units from Garmin (Edge, but alas Oregon) tend to crash every now and then. And my ride is lost after that.

      The media indeed writes mainly on newly released devices, which makes sense. Thanks!

    • Which Edge unit?

      I’m truly curious as I record every ride on 3-4 Edge units and haven’t had a data file loss in at least 5-7 years best I can remember.

    • Phil

      I’ve used the 500 for a little under one year, and that one had the occasional crash. I kept the fw up to date. That was all some time ago. Recently I’ve tried the 1000, of which I can only remember 1 crash (actually, just stuck, didn’t respond to touching the screen nor pressing a button). Only used it for 10 days, returned it, and tried the 820. That one had old fw on it, so I updated it before testing it. Used it for 2 weeks, had 4 crashes, sorry, freezes. I used it almost daily.

      Both units had 1 second recording, display stayed on, usually trying out TBT as I wanted to test that for holiday rides in unknown areas.

      Also returned the 820 because of those freezes, and chose to order the WE Bolt, which I haven’t received yet.

      I haven’t looked at the .gpx files from those Edge devices, but did see there were less files than the number of my rides during this ≈ 3 week testing period.

  30. hansipeter

    Question (convidence intervals): comparing Bolt vs 520: going from +3.5 – 1.5s.

    why are they so huge? Small sample size? big variance? the impact really seems to be negligible!
    … when you look at the inverals there’s only the Dash & 1000 that “drag” you down.

  31. Bartus

    The large error bars suggest that there is no significant difference between any of the bike computers. Or alternatively it might suggest that the testing method was inadequate and did not met the needed precision.

    • Actually, it shows that there is a difference. Small, but definitely a difference between the various units.

      There’s really no other option for testing, besides CFD – which is more theory (not bad theory, but also not real world).

    • Lukas

      A wind tunnel experiment isn’t real world either.
      As posted above, both methods have advantages and disadvantages. Both methods create a model of reality that is simplified in a way that you hope it covers all important influences while making it possible to control.

      As my numerical mechanics professor once said (tongue in cheek of course): No one has trust in a numerical simulation except the guy who has done it. But everyone has trust in an experiment except the guy who has done it. 😉

      To be clear, I do not want to criticize or doubt the test of the setup or the abilities of the Specialized engineers. As a simulation engineer in structural mechanics I just don’t like it if test rig experiments are confused with real world behaviour. The best you can do is having a team of simulation and test engineers that work together efficiently (and when that happens I like my job most).

  32. Raul Freitas

    No specific aero mount for TT/ Tri bikes?
    How come could Wahoo miss this one?
    Makes no sense to me, since by definition it’s on them that aero matters the most!…

  33. Gabe

    Here is some thought from a pro.

    link to telegraph.co.uk

    marginal gains is just bs marketing.

    lose some weight and work on being stronger.

    • Well, I’d argue that the concept of marginal gains is very much real. Meaning that saving 1% here and 1% here does actually add up.

      The real question is whether or not Team Sky actually uses said method, or relies on other options…

      (Also, I’d argue that while I suspect Wiggins is likely telling the truth in relation to Team Sky, I’d also guess he’s just as guilty as the next pro cyclist from the previous era.)

    • okrunner

      Even coming from me, a below average rider, I agree with DC, marginal gains certainly add up. I don’t dispute you need to lose weight and be in shape. However, There is a reason Phil Gaimon is cutting the drops off a 13 pound bike to capture KOMs. On the other end of the spectrum, it doesn’t take much of a genius to notice the difference between a $150 set of wheels and a new set of DA wheels. That’s a big gain, but, every little bit helps. The issue for most of us non-pros is, can we afford it. I recently purchased a top of the line shoe. Most would argue there is not much gain between a $200 shoe and a $400 shoe and 100 grams. I disagree. I damn sure felt faster and they are oh so comfortable.

  34. Eli

    So all I have to do is not be on the bike and I’ll see this…. Sure having the bike computer at an angle with cause a large cross section and be less aero on its own but if it blocks air from hitting the person riding the body in a more aerodynamic way it may have a net positive

  35. Till

    Interesting. It’s worth noting that the original claim, according to your screen shot, was 11 seconds over 40 km at 21 km/h, i.e. 0.16% time saved, while you’re seeing much less than that. One seconds over 40 km at 50 km/h is around 0.034%, or about a factor of 5 _lower_, when in fact, the drag at this higher speed should have been more than order of magnitude _higher_. To conclude, assuming that the measurements are sufficiently accurate, the claims are not just off by a little, they are off by a lot – at least by a factor of 50. Increasing the angle and therefore the overall drag on both units will also increase the difference linearly, but not by a lot.

    In other words, according to your tests, the time saved over 40 km at 21 km/h would be around 0.1-0.2 seconds.

    • Phil

      It’s difficult to state anything, since Wahoo screwed up their claim. First they say the average speed is 21kph (caption in the 2nd screendump), then they say it’s 21mph (4th screendump)

  36. Till

    And since you’re already putting all your watches on a scale, here’s another silly calculation you could perhaps do:

    The difference between a “heavy” running watch, like the Fenix 5, weighing in at 86g, and a light one, like the forerunner 235 (42g) is around 40g. Now, the extra time required for a 70 kg runner weighing an extra 1kg of weight is around 1.2%, or just over 0.05% for an extra 44g. Translate that to a 3:00:00 marathon, and switching from a Fenix 5 to a Forerunner 235 would save you around 6 seconds, whereas running watchless would save you around 12 seconds. And that’s not even taking into account the fact that a watch worn on your wrist requires a lot more acceleration…

    • Phil

      Good golly you are so spot on sir! Never occurred to me, but that’s probably because I wouldn’t be in the 3 hour ballpark of a marathon anyway. I’m way too unexperienced, and too old, for an achievement like that.

      Still, valid point. And 6 seconds is a make or break in my book, especially when it comes to running. I wonder if it would make a difference if one were to wear a running watch on the hips, instead of your wrist. Something that is impossible to test, obviously.

  37. James

    If you have more time and money to spend wisely, is it better to have your fingers lightly open giving a 1mm, 2mm, 3mm gap between fingers on the bars or fully closed for aerodynamics?

  38. Dana Rasmussen

    This has to be one of the most preposterous things I’ve ever read in the world of cycling.

  39. Darren

    What I see is a whole bunch of measurements in a distribution that’s only mildly broader if at all than the Gaussian distribution implied by the displayed uncertainties. While I think that means you may have over-analyze some of the differences (I think in an attempt to give the benefit of the doubt), in the end I think this is compatible with your overall conclusion, that this all makes roughly no difference to anything that matters.