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Bike Fit and Aerodynamics

Not All Bikes Are Created Equal

Bike fit is as hotly contested as the global warming debated. Forums, social media, local bike shop, and every cycling blog you can find is filled with bike fit debates.

Roy Foley
January 29, 2018

The Great Debate

Bike fit is as hotly contested as the global warming debated. Forums, social media, local bike shop, and every cycling blog is filled with bike fit debates. Aeropro has decided to weigh in on the great debate with a series of articles that will shine the light on bike fit and clear up the poor advice being thrown around.  

Direct To Consumer

Recently several customers have come to us with bikes purchased directly from bike manufacturers. The latest business model has some of the most prominent brands offering customers the option to order directly. For consumers, they save money and time shopping multiple bike brands.  But, the problems start when the bike does not fit properly. Three of the last five people recently fit had the wrong size bike.  Most of the new bikes these days have gone to customized integrated parts. leaving the only option for our clients is packing up their new bike and shipping back.  What was once a time saver, less expensive and hassle-free experience turned into a nightmare? What went wrong?


Taking static body measurements do not account for a cyclist's riding asymmetries, ankling range or lack of flexibility, to name a few.  If a rider's measurements are not taken simulating real riding conditions, there is a high probability they are not correct. Cycling is dynamic with several variables such as riding style, body morphology, ankling, injuries, mobility and we are just scratching the surface. One sign your bike fit is going in the wrong direction is when measurements are taken from a static position.

 Bike fit needs to be dynamic, under real riding conditions and measured using tools that provide for accurate motion capture. We use Retul, but there are several products on the market that can provide motion caption data. Retul does not inform a bike fitter what to adjust.  It does provide several body measurements that a qualified fitter can exam and make corrections based on a cyclist's needs. Let's address some common questions we encounter on a daily basis.

Bike Size

 What is my correct bike size? There is no easy answer, but we can say with 100% certainty it is not always your standover height. For the $150 recreational bike standover height works 90% of the time.  But for those who are riding 1 hour or more or spending over $1000 on a new bike, you require more.  How tall are you? Or, What's your inseam?  Does not cut it. Let's take a look at one reason why static measurement does not work.


All Riders Are Not Created Equal

Below we have three different riders types.  For this example, let's assume each rider is relatively the same hight.  The first image the rider has a neutral torso length.


This image the ride has a shorter torso.


The final image the ride has a long torso.  


Based on rider height each would ride similar bike sizes. But, based on dynamic fit measurements bike size can vary greatly. The long torso rider will need a longer bike while the short torso rider will want something not as stretched out. Now, what if they all have different ranges of flexibility?  Maybe the long torso rider has limited flexibility reducing extension towards the handlebars. This would require a shorter reach that would not be addressed by standover or height. Now, throw in different saddles, and everything goes to crap!  Yes, different saddles will change fit drastically. Your inseam length will not account for these types of variances. If the water was not muddy enough add in bike sizing is not standardized.

Trek Bikes

Select To Setup Appointment

Stack And Reach

The chart above is for Trek road bikes and we will focus on the stack and reach. Stack and reach represent the height and length using the bottom bracket as the reference point. Stack and reach provide for a more standardized approach to measuring across bike frames/brands. Notice in the above image we have the same bike manufacturer but different bike frame measurements for the same size. Check out the two size 56 bikes highlighted and you can see them very greatly. The TOP 56 is longer with a reach of 395 and lower with a stack of 549 compared that with the LOWER 56.

Stack and Reach

Not all bikes are created equal, meaning a 56 Trek is not the same as a 56 Giant.   So, let's assume you are fit correctly to your current Trek 56, and you want to purchase a Giant.  Simple right? Do you buy a 56 Giant?  NO! Each bike brand has their bike geometries and designs that set them apart from everyone else.  So, your 56 Trek might be a 54 Giant.    How do we select the correct size?   During a proper bike fit you should come away with a stack and reach that best meets your needs.  Using these numbers, you can cross-reference against all the major bike brands.  By using the stack and reach as a starting point you can make a highly educated decision on bike size.  If you are using standover, inseam, and height you are taking a stab in the dark.  Aeropro's fit service assist the customer in making the right choice on bike size and setup. One BIG PLUS for Aeropro is we are not tied down to one specific brand. Our recommendations are solely based on the riders best interest. 

Giant Bikes


These are just two examples of why getting a custom dynamic fit is important and will save you a lot of money in the long run.  A professional bike fit should feel like a 1-on-1 coaching session. Riders should come away with a customized fit, educated on changes and why, a good feel for proper bike form and bike measurements for future use. Our next article will address your bike measurements and how you can use for future bike purchases or take with you on your next bike trip. So, if you travel by your bike or plan to attend a bike tour stay tuned and we will show you how to make sure things measure up.

Future Article!

Bike fit is a process that requires fine-tuning, coaching and the experience to work with athletes to find your optimized position. The images below show Aeropro's work as we transform this rider's position optimizing power and comfort first. The final step in the process is aerodynamic tuning with the leader in the industry, THE AEROPRO! Our experience in getting the most out of a rider's position is second to no one. We will share with you how we go from average riders to improving every time you race. This series of photos speak volumes and his results are outstanding.



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