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Aero helmets

hi all,
heres a question for you,
Aero helmets, how much benefit do they give over a standard one, read some articles saying they can give minutes worth of difference!!!
Is this true???
They seem a cheapish way of saving time on tt and tri bike legs


  • JulesJules Posts: 987
    Get one, they are fantastic.

    You can get a big time benefit. Also, I find if I am motivated to push harder on the bike as well - to avoid looking "all the gear and no idea" in my silly hat.
  • I don't own one myself but an aero helmets can certainly make you ride faster, providing you maintain a decent average speed to begin with. I'm sure i read somewehere that the average, middle of the peloton, rider maintains an average speed of around 18mph+. If you can't maintain that sort of speed, an aero helmet won't do much for you. If you can though, it's one of the cheapest ways to notice an immediate increase in speed.

    Alternatively, use the Fabian Cancellara method of speed increase and hide an electric motor in your downtube (allegedly)
  • I know what you mean, my gf is always saying how stupid they look!!!
    I can manage 20mph average on a 25miler
    Actually did 21 mph for tatton olympic on sunday!!

    So would a helmet benefit me do you think???#

    Really would like the proper tt bike but too expensive at present for my budget, and credit is a long time paying for it!!!!
  • ZacniciZacnici Posts: 1,385

    I've posted before on this, could only find this one

    Can't find my best ref as I have some of them bookmarked (sad git I am ) but also here:
    http://www.pponline.co.uk/encyc/cycling ... mina-33073

    Get a pointy hat
  • My mrs calls mine the Ailien helmet!

    I may be wrong but shouldn't the helmet
    Benefit The slower rider more as a percentage
    Gain over time because they are gaining aero
    Benefit over a longer amount time?
  • ZacniciZacnici Posts: 1,385
    Trisurfer you are quite correct. Aero advantages such as pointy hats, bars etc do indeed afford a greater time saving for us mere mortals than for elites due to the speed they travel at and the sheer amount of air that they have to cleave through.

    Again I posted on this a couple of times but can't find my links now - sorry

    Another link
    http://www.cyclingtipsblog.com/2010/04/ ... equipment/
  • being a sad geek, I've tried to get into the math around friction a few times, but haven't quite nailed it...probably because there's so many different formulae, and apparently the only real way to know is to use a wind tunnel... however I'm pretty sure that it's a myth that aero equipment benefits slower riders as much as faster ones, and here's my logic.

    Friction, or more correctly drag, is inversely proportional to velocity for low viscosity fluids (eg air)...I think the key factor being that it increases by the square of the velocity, or in plain English as speed doubles, the drag quadruples.

    Therefore at low speeds the amount of drag impacting the rider is much lower than at higher speeds, so although the rider will take longer they won't gain as much benefit. In fact due to the proportional nature, if you're really slow, then aero equipment may not benefit you at all, as the actual resistance (drag) is minimal, therefore any percentage gain is negligible.

    ...but having said all that, some equations for drag state it's proportional to velocity, which changes everything, and the actual improvement for aero stuff is usually given at a set speed, or it's a flat percentage gain...neither of which help work out what the real world benefit would be.

    So all in all, I think there’s a benefit regardless of your speed, but it becomes more important the faster you go.
  • OK, finally found a formula, and it does back up Zacnici, as although your power output goes up by a cube factor, drag remains a constant increase. Based on which it means you get the same percentage improvement from aero equipment regardless of how fast you're going...which just starts to hurt my head...use aero kit, fast riders get a greater speed increase, but slow riders get a greater overall gain

    However what it doesn't take into account is the friction of the bike (rather than wind resistance). So I think at low speeds there's still less of an overall advantage due to inherent friction, but so far I'm not sure how low those speeds need to be...
  • JulesJules Posts: 987
    This article would also appear to back up the suggestion that aero helmets (and other aero equipment will assist slower riders more than fast ones.
  • ZacniciZacnici Posts: 1,385
    I've lost my links on this but as far as I can remember at 15mph aerodynamic drag exceeds the rolling resistance and at 20mph the rider is displacing 1,000lbs of air per minute and the problem presented is not only cleaving your way through this but also trying to ensure the 'smooth reassembly' (nice phrase) of air behind or to minimise drag.

    Again as I remember the problem is not only the friction caused by air passing at or close to the surface but of the turbulence caused by non streamlined objects hence dimples etc to create near surface drag - laminal flow is that the term? - to slow down the air and reduce turbulence

    Drag does not have a constant value in terms of watts required but does have a fixed coefficient (unless the body changes) and the power output required to overcome it increases at the square of velocity as I recall and the power output required at any velocity is the cube.

    Found this
    http://www.mne.psu.edu/lamancusa/ProdDi ... ecalc1.htm

    I used settings of:
    Gear ratio .269 14/52 (unrealistic I know but closest I could get)
    Air Resistance Full Crouch 0.0032
    Rolling resistance .004 racing clinchers

    So little old me at 20mph needs 144.12watts, 76.007% (109.45w) of which is to overcome air resistance and 18.992% (27.37w) to overcome rolling resistance.

    The elite at 25mph needs 261.24watts, 81.902% (213.96w) to overcome air resistance, 13.097% (34.21w) rolling resistance

    Let us say my pointy hat saves 10 watts at 20mph that equates to me having the equivalent output of 154 watts and achieve a speed of 20.52 mph. The elite rider at 25mph to get the same increase in speed to 25.52mph needs the equivalent of 276.34watts or a 15.1watt saving. The elite therefore needs to achieve a 150% saving over my 100%

    My brain now is about to explode so can someone step in to finish this off (where are those damn links??)

  • Interesting reading this guys so keep it coming...

    After posting a 1hr 7 minutes at Allerthorpe tri last month on a std road bike with no aero helmet, no carbon aero wheels, and no tri bars fitted, im interested on how much time i could save. Obviously with a few tweaks without buying a TT bike (yet) i should save time but im not sure how much?
  • ZacniciZacnici Posts: 1,385
    This link is pretty typical; aerobars £30-£60, pointy hat £80 will give good time savings yet I still see many people shun the pointy hat cos they think they will look a t##t and then spend mega loads on bling wheels
    http://www.cyclingtipsblog.com/2010/04/ ... equipment/

    Ah here we go, very own 220 mag
  • Aero helmets are no doubt quicker but yes you do look a bit of a knob.

    You will loose all the advantage if you tip your head forward too often. On a hilly course consider the extra weight. You also need to be careful you do not overheat.
  • front page also confirms that aero helmets arent for everyone or even the best....lol
  • Right again Zac.

    There's a good calculator here http://www.exploratorium.edu/cycling/aerodynamics1.html that you can plug figures into.

    Overall it's basically down to the law of dimishing returns, ie the faster you go the less actual time savings you get.

    Simplifying things, the two factors that will reduce the power required/ increase speed (however you want to look at it...) are the surface area and the drag factor. Both work in the same way in the calculation

    So to maximise your speed, reduce your body's frontal area as much as you can (free), and then it's down to the bling/ pointy/ dimpled things to reduce the drag afterwards (expensive).
  • Finally got my head round this, and what it boils down to is, at any speed you get a percentage aero saving. For slower speeds this gives you a greater time saving over the same distance, however the reason why this feels wrong, is due to the power output at the various levels.

    You still get the same percentage power saving regardless of speed, however as the power output goes up by the cube of your speed, the power saving in terms of raw power increases drastically. That's why it doesn't feel like aero stuff benefits you at lower speeds, becuase the watts saved are low, however the faster you go the greater the watts saved are.

    Hope this helps someone else get their head round it...it's been bugging me for ages!!
  • Excellent thread guys makes for good reading.

    For me getting 6KG's off is far more important than a pointy hat, no matter how much aerodynamics i got on me noggin carrying too much weight is no goood

    so i may invest once i get the weight off and get over the OMG!!! i look like a cock factor.

    But awesome thread and obviously a lot of time spent on research for this nice one guys.

    Zac you must be single
  • ZacniciZacnici Posts: 1,385
    Blaze - correct although only in last 6mths - and no nothing to do with tri - in fact my ex and I both did the Clumber Park 10k yesterday - anyway ...

    Good luck with the weight loss. Just before I started out 4yrs ago I was about 13st - 82Kg and now 66kg and most of that happened in 18mths - had always been active but just crept up

    Good luck and get a pointy hat.
  • talking about weight?
    I gave up smoking in jan when i decided to train properly for my first year of tri's.
    I have gone from 13.5 stone to just under 15!!!!!
    Try carrying all that when cycling up hill and running, not good!!!
    I know some will be muscle as hadn't done any real training of any kind for years, just hoping i can lose it again for next year!
  • Got you all beat...I was close to 18st when I started tri, after 4 years I'm down to about 15, but it's slow as a lot of it's muscle (I did body building for years). I'm planning a lot of endurance stuff over the winter to try and drop some muscle mass.

    If I can keep my power output, and drop weight, which will also reduce my frontal area, then I'll be unstoppable on the bike next year....
  • Actually i got you all beat i was 18stone 7 and lost 6 and half stone in six months. Spent 5 years lifting weiths and putting weight on in the gym and now back down to 82 kg's

    Muscle atrophy is hard work.
  • How the hell did you lose 6.5 stone in 6 months??? I lost about 1.5-2 in the first year, but it's been a long slow process since then (Ok so my weight usually creeps up again over Xmas etc.). I've just about got my 6-pack back, and still somewhere about 15.5st
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