Sunday, February 14, 2016

When 54 Does Not Equal 54

As Spring approaches, some of us might be itching to get a new bike.  As the rule states, the number of bikes you need is N+1, where N = the number of bikes you currently have.  Before you rush into the local bike shop, I'd encourage you to consider getting sized up for your new bike by a reputable fitter.

Bicycle retail is undergoing a lot of change.  The days of walking into a bike shop, having somebody look you up and down and say, "yeah, you're about a 54" are over.  Well, they should be, anyway.  A 54 from Brand X is not going to be the same as a 54 from Brand Y.  With better tools like fit bikes at our disposal, finding the perfect bike for you based on comfort rather than a guesstimate is much easier to do now, and we should be doing this.  More retailers are taking a "fit first" approach to selling you a bike and this is a good thing.

Bike manufacturing is also evolving.  While bikes are often sized by the length of the seat tube (i.e. a 54 is a 54cm seat tube) starting at the center of the bottom bracket, that length varies greatly from manufacturer to manufacturer due to the style of the frame, etc.  Some are a virtual 54cm (aka "effective seat tube length") based on where the seat tube would end if it were essentially a horizontal line from the top of the top tube, while others will be actual measurement to where it stops (often referred to as "Center to Top" or "C-T").  For example, in my bike database, I have 9 brands of bikes that offer a size 54 (other brands might call it a "Medium" or something similar, while other brands might offer a 53 or 55).  The seat tube length on these range from 481 to 570 mm C-T.  That's quite a range for something called a 54.

I often have customers come in thinking about buying a new bike.  If they are happy with their bike, they think they need the same size.  If they are not happy, they think they need a different size.  They could be right and they could be wrong.  Sizing varies too much to be able to provide a definite answer to this question.  There are also road race geometries, endurance geometries and variations on those that make it even more confusing.

So, back in the early 2000's, Dan Empfield (pictured above) came up with a better way of describing bike sizes - stack and reach.  Stack refers to the vertical distance from the center of the bottom bracket to the top center of the head tube.  Reach refers to the horizontal distance from the center of the bottom bracket to the top center of the head tube.  If you want to get into more detail on this, the best place to learn about it is from Dan himself.

With stack and reach becoming the new standard by how bikes are measured, we now have a better way of finding what size bike works for you.  This is what I can do for you during a sizing session.  We start on the fit bike and run you through a few trials to find the position you like the best.  When you are free from the constraints of an existing bike (within reason), you might be surprised as to what works for you.  We have conventions that we can adhere to use body angles and other ways of confirming the fit, the fitter knows what to look for, and you know how you feel.  We can focus on your comfort and find the edge - once we go too far, we'll know it, and we can go back.

From this process, we derive a new pair of numbers: your handlebar X and Y coordinates.  With these, we can then reverse engineer a bike for you based on different stem solutions to find the stack and reach that works best for you.  We can make a lot of bikes "work" with the variety of stem lengths and angles available on the market today.  Of course, we can also put you on a screwed up setup that will handle poorly.  We need to take handling, balance, and aesthetics into account.  We are looking for elegant solutions.  Often, the bikes that come to me that haven't been pre-fit or sized up prior to purchase are not the most elegant solution, but we'll make it work.

After a proper bike sizing, you may be surprised what fits you.  A 56 with a -17 degree 90mm stem in one brand might work, while another brand's 51 with a -6 degree 110mm stem might work for you just as well.  You might think you want an endurance bike, but the most comfortable bike for you might not be an endurance bike.  Stack and reach, along with the stem dimensions, help us put all of this together.

Manufacturers have adjusted their sizes accordingly.  You can tell which bikes have been designed with stack and reach as inputs to the design process rather than outputs from the design process.  Many manufacturers will give more dimensional information on their websites, including the selected stem lengths, handlebar reach (we'll talk about handlebars in a future blog post soon), and crankarm lengths per size.  This helps in making a better decision as to which bikes will be the best out-of-the-box solution versus which ones might need a stem or bar swap right away.

The size variation is not limited to just manufacturer's differences.  Your morphology will also affect your bike size.  Using myself as an example, I might walk into a bike shop and be told I should be on a 56 or maybe a 58.  But, they might not notice I have short legs and long arms (I'm apparently more closely related to apes than most folks).  My long torso and arms makes it kind of hard for me to find a bike - I need a long and low bike with a -17 degree stem and no spacers under the stem.  That's just the way I'm built.  That might mean that I need a smaller bike (a 51 or 54 might work) to get low enough, but might have to have a longer stem (120mm or so) to make that bike long enough.  Bikes with "endurance" geometries don't work for me.  Long and low is my endurance geometry.  I'm an individual, just like everybody else.

So what size do you need?  It depends!  When doing a bike sizing at Vector Cycle Works, you'll leave with a list of bike solutions that will fit you so you can find a bike at one of the many bike shops here in the Indianapolis area.  Even though I can get you Dimond, Ceepo, Chromag, or Liteville bikes, I am not biased towards any brand and only want what works best for you.  Come on in and schedule your sizing session at Vector Cycle Works at soon!

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