birzman fender aerodynamic faster (3)

We’ve come to expect an array of beautiful tools from Birzman, but fenders? That’s a new one. But of course it’s not just any fender. No, that would be way too boring. Instead it’s a fender that tackles a problem most people don’t even consider. As soon as you slap a fender onto your bike, the aerodynamics take a huge hit. If you’re going to run a fender, why not use something that actually makes your bike faster?

Sounds crazy right? But it’s true – Birzman’s new fender is not only a faster fender, but it’s also proven to be faster than certain deep dish aero wheels and they have the wind tunnel testing to prove it…

birzman fender aerodynamic faster (7)

birzman fender aerodynamic faster (16) birzman fender aerodynamic faster (9)

Calling it the first aerodynamic fender, the AeroGuard comes from the same mind that brought us the Crankpump co2 inflator, as well as Birzman’s new M-torque wrench multitool. After designing the fender with extensive CFD testing, the finished prototype was taken to the Southampton University wind tunnel to test it against various wheels and other fenders. The results prove the fender to be 2 to 3 times more of an advantage over 50mm toroidal shaped deep wheels with drag numbers of 0.077 for a normal wheel, 0.076 for a deep wheel, and 0.074 for a normal wheel plus Aeroguard at a steady 30 mph over real world yaw angles (up to 12 degrees yaw which is the maximum at Southampton). Birzman’s testing goes into much more depth, but the take away is that the Aeroguard would indeed make your bike faster.

birzman fender aerodynamic faster (12)

birzman fender aerodynamic faster (11) birzman fender aerodynamic faster (10)

Currently limited to just a front prototype, eventually a rear will be made as well as long as there’s enough interest in the concept. But since the front makes up 20 to 30% of a bicycle’s drag, the front was the place to start to prove the function. Weighing in at 200g, the fender is a one piece polycarbonate design that pops into place with the front wheel off. Production fenders would be mounted in place would either zip ties or Velcro, with the thought being since the fender makes your bike faster you would leave it on regardless of the weather. Designed around 25 mm 700c tires and standard road brake calipers, Aeroguard should fit most road bikes.

If there is enough interest, Birzman is looking at a larger 29 mm version and a disc brake model as well. Still just a concept expect to see this hit production next year.



  1. Veganpotter on

    Gotta throw these on the TT bike WITH the aero wheels:) Who knows how true this is but I think fenders are better unseen unless you’re riding a vintage style bike…I’d be happy to give up a bit of drag, not for good looks but less ugly looks

  2. anonymous on

    Jan Heine, with his crazy opinions, already tested fenders in a windtunnel and found if you pick appropriately sized fenders, they have a negligible impact on aerodynamics because they shield the spinning tire from the air.

  3. Garth Magee on

    Extending the fenders below the level of the axle actually slows the vehicle. Lower wheel surfaces are moving forward slower than the fender, and are at a mechanical disadvantage to propulsive counterforces applied at the axle (equivalent to frame drag leveraging). Thus, lower wheel surfaces should never be faired. CFD models that do not consider this system drag relationship on wheeled vehicles will be inaccurate. More explanation can be found in our Drag Reduction flyer, or in our pending patent application.

  4. Chris L on

    Velcro??? Tell me that’s a joke. I also worry about clearance around the brakes/crown. Most carbon forks these days can barely clearly a 25mm tire so there’s no way you’d have enough clearance tonsafeky run these on most road bikes. Do hope the concept moves forward to the point that fork makers get behind it and design forks to take these. Here in the PNW fenders are pretty much a necessity unless you enjoy destroying your drivetrain and riding alone.

  5. Mo on

    Unbelievable keen. The whole ‘a proper road bike cant be aero without fenders’ is old fashioned bs. Would love to see some of these in the TdF on a rainy day!

  6. The Boss on

    I’ve got fenders on two of my bikes and I still can’t get over how ugly they look. Ideally I want someone to produce invisible fenders, they would sell like hot cakes.

  7. Durianrider on

    Ive been using Crud Road Racer fenders since 2010 and rate them. They also fit most road disc bikes with a bit of tweaking.

    Id buy a set of these though to try em out.

  8. preston on

    Very interested in the development of these. I run fenders full time and spend a lot of time thinking about how much drag they must create.

  9. Will on

    I love this! Even if it doesnt make you faster – because you’re riding in the rain and not full throttle – its aeroness at least helps to negate its own weight! Great idea, make the rear too, lots of people like me have Domanes etc with fender mounts and do road rides.

  10. ProphetZarquon on

    2021 says hello. These fenders are not available, nor are the other brand of aero fenders promoted around this time.

    Ebikes are exploding in popularity, & I have to believe that on an 80lb, full-suspension 750 Watt mid-drive bike, some aero would be worthwhile.

    I’ve never been a touring bike guy & have no lycra in my wardrobe, but I have always loved the old streamliner look. Due to crosswinds, full-fairing & velomobile are usually used only with recumbents & trikes… On touring bikes we get components that look like rounded blades… But on ebikes its slimline or fat pig with seemingly nothing in between!

    Where is the high power streamliner with a bit of functional aero? Surely these fat tires they’re all running would drag less with just the right fender over the top?


COMMENT HERE: (For best results, log in through Wordpress or your social media account. Anonymous/fake email comments may be unapproved or deleted. ALL first-time commenter's posts are held for moderation. Check our Comment Policy for full details.)

This site uses Akismet to reduce spam. Learn how your comment data is processed.