winspacehyper
|

Bicycle Wheel Power Data 50km/h

Over several years, bike wheels have been tested for aerodynamic performance. To date, this is the largest independent dataset available. Popular brands such as DT Swiss, SwissSide, Shimano, Mavic and Bontrager have all been tested. This dataset was originally derived from wind tunnel test data but has latterly moved over to Dinitriev number with a back calculation to give “wattage”. It is not a perfect test.

It should be noted that bicycle wheels are particularly sensitive to tire size and having a wheel and tire combination that bulges will cause a significant increase in drag. Ideally, the tire and the rim should be of the same width. These graphs are now updated on a regular basis and are plotted for interactivity. You can see some of the background for this data here.

Small differences in watts should generally be ignored as these will be affected by arbitrary things such as shoe overlap and the size of bike frame. A bigger differential will produce a bigger drop in drag but it diminishes as the wheel tends towards a disc. In general, a deeper rim will always have less drag. The spoke area which is of high turbulence is much smaller on a deeper wheel – hence the primary drag reduction.

Warning

A number of cyclists get infatuated by very small differences between the wheels. Guidance in this regard is to adopt a 2.5SF rule. That is to say that for an appreciable difference, there should be a difference of 2.5 significant figures.

eg a rider is unlikely to notice a difference between a 190W wheel and a 180W wheel (2SF). There is some error in there as well as geometrical differences based on the rider and their bike. When the difference becomes 190W vs 175W, that is effectively 2.5SF and would be noticeable.

This is a rule of thumb and requires considered application.

Similar Posts

COMMENTS! Please leave a reply to add to the discussion! NO NEED TO REGISTER!

65 Comments

  1. I’m a fourth year MEng aerospace engineering student and haven’t heard of Dnitriev number before – can you explain what it is? You have referred to it a few times but I can’t find any information on it. How is it calculated, what factors affect it, what are its advantages? I want to include it in my thesis in aerodynamics as a comparison to other methods and metrics. Thanks!

    1. It is a ratio of local vector to global vector. Dinitriev is a “trade name”. It might be called something else depending on where in the world you are. Additionally, unsteady aerodynamics is rarely taught at undergrad level.

      1. Hi Hambini,

        Thanks for the explanation, and that makes sense why I haven’t seen it at uni. Do you have any good references / textbooks that explore it a bit more?

  2. Any chance you could review the ICAN Aero wheels? Road.cc seem to hate them, but forums seem to think they’re a hidden gem. Not sure who to trust!

  3. I would like to see some data on old school wheels, how much power savings for 28, 32 vs 36 spoked wheels? Thanks!

    1. Same. How much does a modern carbon wheel save vs an old boxed style rim or even a modern alloy rim. Most of the rims in the chart above appear statistically close to one another and the scale just highlights differences that may not really exist in the real world (per@Hambini’s notes). Really trying to figure out if a wheel upgrade will make that big of a difference in my speed and if it is worth it to upgrade to a more aero carb or stick with a more reliable alloy wheel for my rim brake bike.

      1. The mavic rim is about as close to a box wheel as you will get. When the rim depth is quite shallow the thickness to effective cord ratio is quite low so you don’t get the benefit of the aerofoil shape.

        1. Thanks for the quick reply. If I throw the Mavic Cosmic Elite (30mm) and Winspace Hyper 50 number from your chart into http://bikecalculator.com/index.html, I’m looking at about a 0.9 kph (0.6 mph) increase for the more aero option, ceteris paribus. Does that sound about right?

          1. You’ll probably need to email me about this one. I can’t see any option for rim depth on the bikecalculator website. Also, take into account the spread of results that is based on. It will be a bell shaped curve albeit flat because it’s multi variable analysis.

  4. so the tri spoke is more aerodynamic than 88mm rim?. or both tri spoke and disc vs pair of 88mm rim?

  5. Reynolds wheels seems to perform quite well with more of a V profile rim. Is this because it is closer to an aerofoil shape?

  6. Have you looked at testing the Fast Forward Falcon two spoke front clincher? It would be interesting to compare the data to the 3 spoke wheels.

  7. Why the 454 performs so poorly agaisnt the same class of wheels? It’s full 11W and 13W more power absorbed against Giant SLR 55 and LightBicycle WR56.

      1. Thank you so much for all that you do! Have you seen LB’s new sawtooth rim which they claim has about 25% less drag then their traditional wheelset in the same depth. Bullocks?

    1. I think the super wide thing is a “flavour of the month”, it will go out of fashion a bit like the previous trend towards narrow axle cranksets and pressfit bottom brackets (general trend is to move to threaded). V shaped profiles verge towards aerofoil sections at the top of the wheel where it matters so they are effective. The Swissside wheels are well designed because they use a small hole and measure the width for leakage. Aerocoach which adopt a similar construction got it horribly wrong and consequently have very poor performance.

      1. The Light Bicycle AR56 wheels seem to perform really well. Would you recommend them for the money (around £550 with bitex hubs)? I’ll be throwing Conti 25mm GP5k which should measure out the same as the 23mm GP4k.
        In terms of aerodynamics, they have more of a rounded V shape where as a lot of the newer wheels have a blunt U shape. In real world scenarios what effect will this have on their performance?
        I also need to get them with drain holes due to wet weather in the UK, they place 2x 2.5mm holes just below brake track at 90 and 270 deg of the valve hole. Swissside wheels also have a small 3mm drain hole on one side of the wheel just under the brake track. Would these holes affect aerodynamics? They just let water out the aero cavity if it gets in through the spoke holes.
        Finally how much difference will internal nipples make? I’m thinking of going CX-ray aero spokes with internal nipples.

      2. What do you mean when you refer to swissside and the small hole they measure the width for leakage? Are you referring to the 3m drain hole on their rim?

  8. Hi! Have you ever tested 4 spoke wheel? If not, based on your experience, what will be your guess on this a wheel with 4 vs 3 spoke?

    1. Generally a lower spoke count is better but there is also a structural trade off. For vibration issues, I’d always recommend an Odd number.

  9. Hi, very interesting!
    Quick remark for the budget oriented triathletes, what do you think performs best for the rear wheel on something like a 36-40kph effort?

    – a standard 50mm deep section wheel (bontrager aeolus, yoeleo c50, mavic cosmic pro, …)
    – or one of those home made disc wheels as made famous by GCN (https://youtu.be/qevfMwzGPmc)

    Does it make sense that I start DIY’ing? Or would you say, don’t bother with custom built contraptions?

    1. A disc wheel will always perform better but not necessarily the one from GCN. it might “Boom” too much. A cheap wheel from an online supplier would likely be fine.

  10. I do enjoy reading your articoes and based on those aero test I’m 99% into buying Hyper wheels .
    One small thing: you mentioned Hunt wheels as one of the worse performers of the aero test, same Hunt who uses the EXACT rim profile and layout as Hyper on their Hunt Ud wheels set, so now the Hunt rim is good?..

    On the other hand there are some realworld tests of the Hyper wheels downhill and it seems that somehow, at 50kmh + they tend to be less fast than Bora for exampe (you can have a look at the thread on weightweenies), maybe due to the large spokes.
    What do you think?

  11. Also appreciate all the work and time you put in to give us another perspective! Like another person asked above, any chance to look at and consider the LB “x-flow” profile? It looks like it’s kinda different from zipp sawtooth that has variable depth, opting for variable width!? I guess I could imagine maybe a crosswind buffeting benefit, but is that even real?

  12. Thanks for all the work, super helpful and entertaining!
    The U-shaped rim profile is said to be more stable in crosswinds. But after seeing your aerodynamics masterclass video I’m hesitant on them because I’m guessing there’s a major aero penalty because of the steep alpa number.
    What’s your take on U-shaped rim profiles?

    1. It’s not a question of V versus U, it’s more an issue to do with alpha critical angles. I would take a look at the aerodynamics masterclass video to take a look.

  13. How much of the saving would you estimate comes from the front wheel alone? For example if you were to have a 50mm front and a 28mm rear, how much slower would this roughly be than the 50mm as a set?

  14. Hi Hambini, thanks for this great content. What are your thoughts on why the Winspace Hyper performs so well? Their specs don’t seem to be anything vastly different than other wheels, other than the filament-wound rim instead of laminated pre-preg. They also use exposed nipples (heh) whereas e.g. enve use hidden nipples which I understand should create an aero penalty.
    Thanks!

    1. The thing they have that is majorly in their advantage are the rims are quite narrow. There is a belief that wider is faster – it isn’t. The winspace works well with the narrow wheel and they’ve lined up the geometry so the air sticks (does not detach) comparatively well.

      1. Are wider rims simply an easy solution to create a much better “flow / transition” with wider (trendier) tires?

  15. Hello Mr. Hambini. I´ve read your Articles and watched your videos about Aerodynamics and the problems of unsteady airflow. Now I´m wondering, how much difference a deep rear wheel makes at all. Your test tests the wheels isolated. But the airflow is already so much disturbed by the front wheel, the downtube and seattube, the cranks, pedals, shoes, calfs, that it is more a whirlwind than a flow when it reaches the rear wheel. A discwheel can probably reattach and „calm“ the air. But can a 60/70/80mm rim make a difference to a more traditional 25 mm v-shaped rim?

  16. so, my 50mm winspace hyper wheels will absorb less wattage with 23mm tyres ? The aero detachment point is just as effective with 23mm as 25mm ?

  17. Hi,

    what is your view on tubular tire width vs rim width in the context of track usage? Also, what do you think about deep carbon wheels vs. 3 spoke vs 5 spoke? Planning to run 23c tubular tires on my track bike. Getting a disc wheel for the rear, but still debating the front. Notice most track racers in UCI competitions are running Mavic 5 spoke front with disc rear (except for time trial events where two discs are used).

    Thanks,

    Morten

    1. For ultimate aerodynamics disc and disc will be fastest but you will lose the ability to make swift changes in direction. Hence the move towards spoked albeit tri and 5 spoke front wheels. For tubular tires. They end up running at very high pressure and you are verging on hertzian contact so it’s aerodynamically superior to use a narrow tire.

  18. I’m trying to optimise my setup. Currently i compete in triathlons, most raced on road courses and for long distances 20-56miles. I inherited a 90mm tubular front and disk rear with 23mm tubular tyres (flush with the rim).
    I dont know if i would be better going to a slightly shallower depth eg. 60-80mm on both with a more modern 25mm tyre for our rough roads and less predictable conditions? Or should or stick with what i have?

    I raced with these wheels down at goodwood motor circuit this year woth 20mph winds, it was an handful at times but manageable when dry. I really noticed it when it started to rain and the wind was trying to push me out on the corners whilst trying to bank around the corners with less grip.

    1. If you go to a shallower wheel, you’ll lose some of the outright drag reduction but you will gain the stability. The guidance is generally to use the deepest wheels you can comfortably control.

  19. You’ve clearly advanced the public’s understanding of aerodynamics; especially related to wheels. Congratulations and thank you for that!

    My thoughts are that entirely too much time, money and effort has been wasted on this subject and it’s related wind tunnel testing.

    First is the fact that wheel drag isn’t the biggest component of overall drag, nor is it the easiest to address. Its a great way to buy something showy and spendy, but if you want to go faster, just train and watch your diet (oh, and pick your parents well).

    Second is the issue of testing versus validated design theory. I would suggest that there doesn’t really exist a body of validated design theory for bicycle wheels. Further that most of the variations in performance, as measured, are just down to dumb luck of the various design teams.

    I say this, in part, because airflow around small objects (including airfoils) at low speeds, behaves differently from large objects at higher speeds. The RC modelers who build sailplanes (where lift to drag and drag to speed are very important), know better than to use scale airfoils until their models get quite large (say 1:4 or 1:3 scale). A bicycle tire/rim is a small low-speed object, but I’ve yet to hear anyone take this into account regarding aero wheel design.

    Note also that the “airfoil” of a bicycle wheel spins through 360 degrees for each wheel rotation. Like an American football kicked for a field goal, when viewed from the side. That deep-V sometimes presents itself as a leading edge, sometimes as a trailing edge, and much of it’s time its somewhere in between. Therefore the common diagrams of airflow around a tire/rim (which ignore these different angles of presentation, not to mention the yaw effects noted in the article above) are meaningless. Bicycle designers don’t seem to consider this topic – but the presentation angle assuredly impacts separation of airflow. I there seems to be little mention of parabolic versus straight lines or constant curves ( which is to say round).

    Regarding spokes, I suspect that flattened spokes offer no aero benefits, and may induce extra drag, even under optimal conditions. Moreover, what standards or measures exist for the alignment of flattened spokes to point them into wind? How can a cyclist ensure that their spokes haven’t twisted out of alignment? Maybe we should all buy spoke alignment gauges? 😊. If I’m correct, having a round spoke profile near the rim is no worse than having a flattened profile and the round outer profile may even be better. Which is not to say a shorter spoke isn’t better aerodynamically.

    But before suggesting that shorter spokes are better, what offers the most benefit, fewer spokes or shorter spokes? How does one establish the trade offs of these alternatives and weight and wheel comfort? How do these spoke choices affect control of airflow and avoid separation across the myriad of presentation angles of the tire/rim?

    These problems are complex. With enough research we can probably surmount them. But is that a cost-effective use of resources? Clearly, even accidental aero design is a moneymaker – marketeers love it. Any doubt of this can be erased by considering the retail costs of aero-wheels. Even honest testing doesn’t slow down the marketing-juggernaut, nor does it provide consumers with any thing beyond the illusion of smart shopping.

    One other point of interest, I think that the modern interest in wider lower pressure tires began about 10-12 years ago sparked by research conducted by Jahn Heine of Bicycle Quarterly. As his research was conducted on a real bike in the great out of doors, using a constant (gravity) for acceleration, he eliminated much of abstraction of air tunnel testing. Frankly, I’d regather ride a good supple tire that was wider than its rim, than a skinny rock on the very best aero rims, and I’m confident that at the end of the ride I’ll post a better time.

    Consumers don’t understand that aerodynamics is not a visually intuitive subject. Many factors go into the test differences that you noted. Until research can determine which factors determined how much to each wheels results, it’s too soon to prescribe rules of thumb.

    Ok, this is a long post, but it’s the 2-cents of insight from my five-year old self.

  20. I noted the top 3 combos used a disc rear wheel, but only the Yoeleo 88mm was also tested with a front/rear combination. The absorbed power is 558W and 590W for the Yoeleo, a delta of 32W. Interpolation like this is probably not accurate, but applying the same delta to the AliExpress 3 spoke (Hed3 semi-copy) would put that at around a 583W front/rear combo. That would make the AliExpress 3 spoke front/rear combo one of the top wheelsets in the chart. Any opinion on the validity of this ballpark estimate?

    Along the same lines, do you have any plans to test other tri/quad/penta spoke wheels? The Shimano Pro 3 spoke wheel is highly used in the ProTour, but there’s limited testing of it versus other wheels. My timetrial front wheel of choice is still my old Hed3 with Continental Supersonic 20mm, both are now out of production. I’d love to see either of those wheels make an appearance in your charts!

    FWIW – your Flo results mirror my “Chung” field testing. Within the wide margin of error on field testing, my Flo60 and Flo90 front wheels tested considerably worse than the Hed3, Spinergy Stealth 50mm, and FFWD F6R using the same tire and tube. I sold both Flo wheels at a loss.

    1. It’s *probably* okay to interpolate given that you clearly understand the error margins involved at those speeds. The error on the rear is much less than the front though as the air has been disturbed by the point it gets there. Hence the benefit of a tri spoke on the rear is somewhat diminished and the general consensus would be to go for a disc wheel. I think your interpolation would work and would get you somewhere near but it does have significant scope for error.

      With regards the flo wheels, that does not surprise me.

  21. Hambini,

    Can I ask your opinion of these? https://www.elite-wheels.com/product/gravel-six-s-spoke-bike-wheels/

    I was thinking about running one of these on the front, and a 50mm Far / LB gravel rim with CTi hub and CX Rays on the rear.

    A lot of gravel I ride, or roads on the way to the gravel, are pretty exposed and can have some nasty headwinds. But when you’re not getting hammered by a headwind, speeds are frequently above 35kmh. Sometimes 40-45kmh for sustained periods on some of the gravel if it’s dry and you can weave between the potholes and ruts.

    Can’t really see the benefit of taking a 150-200g hit on the rear on a non-aero bike. But do you think these would have a significant advantage at the front? Or again not worth any aero penalty?

    I believe the only other 6 spoke gravel wheelset is the BikeAhead Composites ones … but they’re 3700 Euros. I suppose these are trying to emulate those at a lower price, heavier weight, and without the spoke offset.

  22. First, thank you for all the time and effort that you put into collecting and passing on this great information.

    Second, how much does hub design play into aerodynamics?

    Third, In regards to hub design, I would assume that straight pull spokes would be slightly more aero than “J” hooks but probably not noticeable. Would my assumtion be correct?

    Lastly, a more complicated question. If 90% of my rides are less than 6% grade what would be your thoughts be on weight vs aero? Specifically, I have been running Zipp 808s (non-sawtooth design) which are quick but slightly on the heavy side. Also, when getting out of the saddle they do flex side to side some but not terrible. Anything approaching 20mph winds becomes progressivlely more dangerous in regards to stability. When I purchased the wheels in 2019 I was of the opinion, given my typical riding terrain, that areo was more important than weight. However, technology has advanced somewhat and I am considering my options. But I’m not sure that spending the money on a lighter, shallower thus more stable, and better aero wheel set would be beneficial enough. Based on your findings the aero gain would be a slight negative (but possibly not very noticeable with some wheel choice options) in order to get a lighter weight and possiblly more stiffness with greater stability. I know you have said that you should ride the deepest wheels you feel comfortable with so it is a personal choice. But, I was wondering if you could provide insight on what factors such as weight, aero, spoke design, hub design/manufactrer, etc. might be more important to consider. Your thoughts and time are greatly appreciated.

  23. I notice some of the wheels are paired with a disk (the winners) and others don’t say “disc” I’m assuming the test was with the deep front and a disc rear ? It seems unfair to rank wheelsets with a deep rear against a set with a disc rear? I’m looking for the fastest front wheel. I’m going to use a disc always in the rear. How can I interpret the fastest front ?

    1. The tri spoke or 5 spoke front is always faster, the spoke drag is reduced. It’s not really straight forward to test a varying combination of wheels, they are purchased as a set. In this case a tri spoke front and rear disc.