Wednesday, January 23, 2013

Dr. Aerolove or How-I-Learned-To-Stop-Hating-The-Bike

*this is purely a hypothesis based on personal opinion and rudimentary knowledge, SO YEAH BRO!

    For a while I have been thinking the bike. More specifically just the hardware (mostly the frame, however I will dabble into the wheels and drivetrain) and its influence on our PB over a set course. Specifically a Sprint 20km or Olympic 40km distance bike in an ITU format race.  Now you're probably thinking "oh yeah I know, I read the (insert aero brand bike here) article on their website".
 Well that statement has me ticked a bit.

-Can we trust that it is fully unbiased and fair for other brands?
-Does it take into account circumstances seen in real world aerodynamics and not just wind tunnel jaunts?
-Are these gains with aero frames really the Be-All End-All solutions? 

    Well lets break down WHAT ARE the requirements of an ITU bike? I like to think of these requirements being split into two categories. The first being 'rule requirements' which are stringent and do not lend easily to being broken (nor should some of them be broken) and 'personal requirements' which do lend themselves to change easily. The rule requirements are pretty straight forward, based off of UCI rules they make the system (as in the bike) clean, and efficient to maintain with different manufactures. The latter categories is what I'll be focusing on. 


Aero frames. I have an aero frame. I love it to bits. BUT I think aero is a gimmick. 
why? YOU. 

    Aero Frames are excellent and cutting through the air and reducing drag, and some of them are pretty trick. who doesn't start dripping from the mouth for a Cervelo S5, or an S-Works Venge? But the gains are insignificant to how aerodynamic you can be. 
    Air is pretty easy to work with. Like most fluids it mostly cares about simple things. One of those is Frontal Area. take for instance a door stop, slanted at one end, flat at the other. but when you look head on at it for either end it has the same area blocking the wind. Now you can tweak the design at either end to make said shape more aerodynamic but at the end of the day it will have finite results UNLESS you lower its frontal area.
    This relates to a bike because a bike is only ~15% of the frontal area the wind sees. 
Now you can go off and get a frame that is say 5% more aerodynamic to your last set up but when your talking 5% of only 15% is chump change (A-Russ got me saying chump a lot, I like it) 
    You know what really is going to make a difference? lowering your upper body by an inch and a half.
    Now you are actively changing your frontal area, and thus making yourself more aerodynamic, and a hell of a lot more then an aero frame can do for you.


Air flow. Wind tunnels are great for data, and weight weenies but where can you find a wind tunnel? Rarely on a race course..

    In ITU Chances are you're going to be in a pack, you're going to be at the front for very short amounts of time, and you're going to be changing pace A LOT.
This is where I argue that a very Stiff, lightweight, non-aero frame is your best bud. Three reasons why.

- Air flow in a pack in going to be 90% of the time turbulent, with 10% clean laminar flow (at front). This laminar flow is where you aero bike is going to shine, but in turbulent flow it really doesn't matter much because. You're probably sucking wheel, and this turbulent flow off of the rider in front of you has swirling currents that help you draft. At this point it is preferable to get as low as possible. Any part of you that breaks the boundary layer and is in the laminar flow is going to see an increase in drag. 

- Lightness. Chances are on an ITU course you're not only going to find corners but hills, and not just little sissy hills, big mother-truckers that make you hurt. a light stiff bike is going to keep you at the front. As you climb a hill and your speed drops you are going to start fighting the hill more then the air. lightness wins this battle.

- Stiffness is going to keep you in the game. ITU racing is loops, lots and lots of loops. this means holding the racing line and keeping you speed up. Unfortunately Bikes, along with racecars suffer from a lack of ABS (them because of rules, us because it just isn't practical). Thus we have to rely on threshold braking and the racing line. 
The racing line is not the shortest line in a corner but the one with the fastest corner exit speed. This is where threshold braking plays a big part. Ideally you want to come into a corner as fast as possible, brake as late (and as little) as possible, and accelerate as soon as possible.  A stiff frame is going to help by giving feedback through the structure as when the brakes lock up. As well as to put as much power to the ground through the rear triangle and drivetrain to the wheel. It's a win win.

(I want to add at this point wheels are also key, deep dish wheels are pretty good but they are not all equal. I don't want to dive too far into this topic because it could easily double the length of this post. however in short the ideal wheels would be ones that are as stiff as possible and with the least amount of weight contained in the rims. They are easy to spin up to speed, and react well to changes in velocity and direction.)


Small bits. When you get the big things down right, it's the small things that make you faster.

     You're Drivetrain has a lot between you and the wheel. not only that but you are putting a lot of power through a small area. parts in this location have a lot of engineering in them but thats not to say you can't improve this. With aerodynamics put aside your next biggest enemy to speed is mechanical resistance. namely all the moving parts in your drivetrain. Solutions to this can be as simple as lubrication of the chain and hubs. 
    Next up on the ladder is tires. rolling resistance is an amazingly big force, sometimes a set of race slicks can outdo the improvements of a pair of race wheels. This is tricky subject up to this point as the lower your rolling resistance is chances are your grip is also decreasing. Remember that you only have two contact patches between you and the bike that is roughly 2x2cmx6cm. Roughly put you have 24 square centimeters to accelerate, brake, and turn with, and there is a finite limit to how much this 24 can handle (Don't keep braking through a corner, your tires are dealing not only with turning but braking as well. Remember you are on two wheels, they will not give you much warning before they snap out from under you. Cue the sad panda here.)
    Near the top of the ladder is bearings, specifically ceramic bearings. Material engineering is spectacular and ceramic bearings are a star in their class. rounder then steel variants, as well as tougher. These units greatly decrease mechanical a cost.

Now you might be wondering "hey this is great and all (you jerk) but how can this all help me be faster? I'm not made of money after all (you jerk again)"

It's OK I don't have money either but as for the best Bang-for-Buck improvements would be a bike fit (lower the frontal area, improve you aerodynamics) and tire (lower rolling resistance can be as good or greater then a set of new wheels). These small changes are what I believe can overcome even the best aero frame out today.

So there is my rant. A little hard to follow maybe, but I am happy to get it out of my head and out into the world. Remember this is all personal opinion, read with an open mind. don't believe everything you read, and don't believe everything you think :) 

Until next time. 

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