Saturday, August 20, 2016

When 54 Does Not Equal 54: Part 2

A while ago, I posted some thoughts regarding the variation in the sizes of bikes that are labeled as being the same size.  Many manufacturers offer bikes in sizes like 51, 54, 56, 58, etc., but that doesn't really paint an accurate picture of how well the bike will actually fit you.  As an advocate of a "fit first" approach to buying a bike, I feel it is important for my customers to understand that if a size 54 from Brand X fits them, that doesn't necessarily mean that a 54 from Brand Y will work, too.  A different model from Brand X might not even fit.  So, in this "Part 2", I thought it might be helpful to look at some actual data.

I maintain a list of bikes and all of their geometry information and use this data when helping customers find the right bike for them.  The bikes in this list include most of the bikes available from several of the local bike shops in Indianapolis.  There are currently 14 brands represented, and I am always adding more as new models are introduced and time permits.  The 2017 models are starting to be introduced, so it's time to start hammering away at adding more to the list.  This is what bike geeks do for "fun."

The purpose of this exercise is to get a visual of the range of bike sizes that exist within a given size label.  Using a designation such as 54 just doesn't give us the best picture.  The better picture is painted using stack and reach, a concept developed by Dan Empfield and which has gained traction with the manufacturers over time.  Most of the manufacturers now publish stack and reach numbers on their websites.  I've actually run into a couple who still haven't jumped on board with this, and it makes it very difficult to compare two bikes.  I love the simple elegance of stack and reach.

We will pick on size 54 today, since it is fairly common.  Bike sizing conventions introduce a lot of variables.  Some manufacturers might opt for a different naming convention such as XS, S, M, L, XL.  Some brands may have only a handful of sizes per model, while others, like the Trek Madone, can have up to 9 sizes.  We also have the concept of geometric classifications such as "endurance", "race" or "women's" geometry.  These exist based on the intended use and market, and other classes exist based on the type of riding, such as gravel, adventure, or cyclocross.  These are all essentially drop bar road bikes.  We'll look at these by their intended use/market, and then see what happens when we combine everything together.

Road Race Bikes
We'll start with the classic race geometry.  These are the Trek Madones, Cannondale SuperSixes, and Specialized Venges that you see under the Grand Tour riders.  These are the bikes you might think you can't ride because you're "too old," "too inflexible," or "want something more comfortable."  The reality is, these could fit you, but you won't know until you are properly sized up.  Let's see what happens when we plot these based on their stack (Y) and reach (X) numbers:

Road Race Geometries
(click on the image for a bigger view)
Before getting too deep, let's define what we're looking at here.  The X axis of the graph (horizontal) corresponds to the reach of the bike, which is also the X axis of the bike.  As you move to the right, the bike gets longer, while moving left, the bike gets shorter.  The Y axis of the graph (vertical) corresponds to the stack or vertical height of the frame.  as you move down, the bike is lower, and as you move up, the bike is taller.  So, the term "shorter" is a bit confusing, but I will use that to refer to the length of the bike rather than the height.  Additionally, these aren't necessarily scaled perfectly where one mm of stack is perfectly aligned with 1mm of reach, but I hope this will give an idea of the ranges involved.

Looking specifically at the race geometries, we can see quite a bit of variance.  Looking first at the horizontal differences, we have size 54 road race bikes that have a reach of as short as 376mm and as long as 390mm - a range of 14mm.  This is where you might find some overlap with sizing up or down - that shorter bike in a 56 might still be shorter than the longer 54 bike.

Looking at the stack, we have even more range - the lowest bike has a stack of 526mm, while the tallest bike has a stack of 565mm - a difference of 39mm.  That's pretty significant.  We can see that we have some bikes that are long and low, which is what you might expect from a road race bike, while others are tall and short.  In this case, the longest, lowest bikes are the Trek Emonda H1 and the Felt F1 (the two dots down in the lower right corner of the graph).  The tallest bikes aren't necessarily the shortest, with the Scott CR1 being the tallest in this group, with the Jamis Xenith being the horizontally shortest of the group.

Endurance Bikes
Next up are the endurance bikes, the geometry that I have more people specify they "need" than any other.  Marketing has led us to think that upright = more comfortable, but once again, this is where a proper sizing may change your mind.  Nonetheless, let's take a look at our selection:

Endurance Bikes
(click on the image for a bigger view)
Here, we can see quite a range, both horizontally and vertically.  Horizontally, the reach is as short as 362mm and as long as 385mm - a 23mm spread.  Vertically, the stacks vary from as low as 552mm and as high as 597mm - a difference of 45mm.

I think where this gets interesting is if you combine the race and endurance geometries together into one chart to see how they trend:

Race and Endurance Bikes Combined
(click on the image for a bigger view)
Once we combine these two types of bikes, we can see that we have a wide variety of bikes called 54. Horizontally, these bikes span 38mm, with the shortest bike being the Jamis Quest and the longest being the Trek Emonda H1.  It's interesting that the shortest two bikes in each category are from Jamis.  The longest endurance bike is the aluminum Fuji Sportif.  The Sportif is a bit tall, and if you look at the Felt Z series, you will see these are almost as long as the Sportif, but lower.  You can see a pretty clear separation of the race and endurance geometries, with some bikes that cross over - the Felt Z series is longer and lower than some of the race bikes.

Women's Bikes
For fun, let's look at a few women's bikes.  The women-specific cycling industry has been on the verge of taking off for what seems like about 30 years now.  For the most part, we're still in "shrink and pink" mode - offer some smaller sizes with some pink touches, and it's good enough.  That concept isn't necessarily reflected here, since we are looking at just one size.  So, what do we see when we add in the women-specific size 54s?  Let's look at the race geometries first:

Men's and Women's Race Bikes Combined
(click on image for a bigger view)
A couple of things stand out here:  First, there are only 4 size 54 women's-specific race bikes offered by the 14 manufacturers in this list.  They happen to be from two manufacturers: Cannondale (CAAD10 Women's and Cannondale SuperSix EVO Women's) and Trek (Emonda Women's and the Trek Madone Women's).  I need to look at my list - there may be more out there, but I might not have added them yet.  I would think Liv would be listed here, and this may be an oversight on my part.

Second, with our small selection of women's race bikes, we can see they tend to be a bit more upright and shorter than the men's (or unisex) race bikes.  That is also not necessarily a bad thing when we take into "normal" human proportions and saddle issues.  But, that doesn't mean every woman has a short torso and long legs.  Nonetheless, if we look at the women's race bikes we do have, these are trending towards the endurance geometries.  So, let's look at the Women's endurance geometries and how they fit into the men's endurance bike world:

Men's and Women's Endurance Bikes
(click on image for a bigger view)
You can see a couple of things here - first, we have a few more women's endurance bikes to pick from, and second, they still trend shorter and taller than the men's versions.

That really leads to a discussion about how appropriate and effective women's bike sizing is.  That sounds like some good material for a future blog post.  From what I've seen, there are a couple of assumptions about women that lead to the trends we see here.  There is an assumption that women tend to have longer legs and shorter torsos.  I don't believe that to be 100% true or as extreme as it might be perceived, but I will need to do some research.

Another assumption gets into the female genitalia.  Part of what makes us different is why saddles cause us problems.  The pressure points that cause men and women grief are different, and in women's case, can make it more difficult to rotate the pelvis appropriately.

Let's Add Cyclocross to the Mix
Finally, let's look at cyclocross bikes.  'Cross bikes have some different considerations that go beyond the practicality of fit - we have to take into account the race format itself.  The cyclocross race format is short, intense, often muddy, requires a lot of getting on and off the bike, and involves shouldering and carrying the bike.  Speeds are relatively low compared to a grand tour or crit, so aerodynamics are less important than making power or maintaining traction.  So, the frames are a bit different.  When I fit a CX bike, the fit is different.  I will use the road sizing, but then generally take the bars up and back a bit, and maybe lower the saddle a bit for ease of getting on and off.  Overall, it's just a bit different - a few millimeters on the seat, and a centimeter or so in each direction on the bars.  We can see how cyclocross bikes look if we just mix them in with the rest:

Race, Endurance, Women's, and Cyclocross All In One
(click on the image for a bigger view)
As it turns out, our 'cross bikes seem to mix in all over the place - mostly right in the middle of the endurance geometries, with a few dropping down into the race geometries.  I'm not quite sure what this tells us, other than maybe the few manufacturers that I have in the list can't seem to decide where CX bikes live.  Maybe as I add more bike brands and new models are introduced in the future, we'll start to see a more distinct pattern here.

I don't know if this discussion will help anybody at all, but I found it fascinating to see what happens when we start looking at the variety of sizes within a stated size.  In the future, I hope to continue to look at how geometries align.  There are a few things that fascinate me about this, including how sizes may cross over (i.e. Brand X's 58 is shorter than Brand Y's 54), what the deltas between sizes tend to be, and then delving into how brands equip the bikes by size - what the crank arm length tends to be by size, handlebar width trends by size, trends over time, etc.  If you made it this far, I hope that you will consider be sized properly by a fitter before your next bike purchase.  Don't make a $5,000 mistake.

Bike sizing is available by appointment at Vector Cycle Works.  Schedule now at

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