Stack and Reach

Purely Custom's sweet X/Y tool

Understanding stack and reach is critical in comparing and finding the ideal frame size but there still seems to be a cloud of mystery around what those measurements are and how they are determined.  While it is true that you don’t necessarily need to know the stack and height of your handlebars to be dialed in on your bike, but knowing those numbers can be critical in matching your position on a new bike, choosing the optimal frame size, or understanding how changes in components will alter your position.

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What is stack and reach?  Frame stack is the vertical distance from the bottom bracket to top of the headtube.  Handlebar stack is the vertical distance from the bottom bracket to the center of the handlebar.  Frame reach is the horizontal distance from the bottom bracket to the center of the headtube.  Handlebar reach is the horizontal distance from the center of the bottom bracket to the center of the handlebar.  We can also determine saddle stack and reach in the same manner.  Essentially this is establishing an X/Y grid on the bike where the axis is at the bottom bracket.  This grid method gives us a very precise manner in determining where the contact points in space are going to be.

Why is this better?  It gives us a better understanding of how the bike we will positioned to your body.  For example, seat angle and saddle fore aft can affect reach drastically.  Stem length can equally adjust reach.  It is possible to run a 56cm and 58cm frame with the exact same reach but the weight distribution of the rider (essentially where the bike will sit underneath them) will be in distinctly two different places.  One may be more optimal for how that athlete is going to be using the bike and without comparing stack and reach measurements we won’t have an ideal picture of what those differences will be between the two different frame sizes.

How do we physically measure stack and reach?  The cheapest way is to put your bike in the corner of a room with the rear tire against one wall and the bike leaning against the other.  You can then measure from the wall that your rear tire is touching to the bottom bracket and then to the center of the headtube.  Subtract the measurement headtube measurement from the bottom bracket measurement and you will get frame reach.  You can then measure from the floor to the center of the bottom bracket, and the floor to the top of the headtube.  Subtract the floor to bb measurement from the floor to top of headtube measurement and you get frame stack.  A similar process works for saddle and handlebar positions as well.

In the fit studio we use a tool from Purely Custom to make the measurements quick and easy.  These tools are expensive, but are invaluable for the numerous bike fits we do weekly at the fit studio.

Purely Custom's sweet X/Y tool

Purely Custom’s sweet X/Y tool

Cervelo created a cool graphic showing the value of stack and reach measurements.  They graphed out the relative headtube stack and reach position of numerous bikes and brands to show how they change through a size range.  Any one brand isn’t necessarily better than another, but it is important to know what changes when going from one size to the next for any given brand.


Aero is Everything


The office for the day.

In 2012 Specialized broke new ground for a bike company in building a brand new, state of the art wind tunnel specifically built for cycling.  With aerodynamics being one of the strongest driving forces in cycling product development, it made sense for the big “S” to build testing grounds in their own back yard.  I had the pleasure and privilege to spend a few days there over the last few years and each time it has been enlightening.

Both of these shapes have exactly the same drag even though the shape on the left is 20 times larger than the one on the right.

Both of these shapes have exactly the same drag even though the shape on the left is 20 times larger than the one on the right.

In January of this year I spent a day working on TT positioning and aerodynamics in the wind tunnel with Sean Madsen (bike fitter to all Specialized ProTour teams), and Chris Yu who runs the high-tech wind tunnel at Specialized.  While it is true you can’t generalize anything without testing in terms of aerodynamics, there definitely are a few general trends we were seeing and some interesting results with differing equipment.

  • As seen in many, including my own TT bike fit, a 1 inch handlebar height difference can be as much as 91 seconds difference in a 40k TT. Even more interesting, about 50% of the time lower was slower.
  • Even a slow position in the aero bars was significantly faster than road position or having your hands on the base bar. If you can’t maintain your aero position for 99% of your race than you need to change your position.
  • We looked at a lot of helmet configurations and a rider’s head position was the biggest determinant to what helmet would be faster. It was almost 50% that were faster in an Evade helmet versus a full TT helmet.
  • Getting narrower often didn’t change overall aerodynamics.
  • Head position seemed to be the biggest driving force in aerodynamics. A position with higher bars but allowed the head to drop below the shoulders was almost always faster than a lower bar position and higher relative head position.  The same goes for narrow, wider was faster if allowed the head to be relatively lower.

We used the Retul Muve bike to quickly move through multiple setups.

This only scratches the surface to what we saw and learned in one day in the tunnel.  Having the ability to quickly move from one position to the other and see objective results is huge.  We are all a snowflake, and no one will see exactly the same results with the same changes, but following the above guidelines is a great place to start and what we use with our aero bike fitting process.


Interbike 2015

Getting up early in Vegas is always a bizarre experience.  There are the guys cleaning floors, the bachelor party slowly walking back to their room after a night of debauchery, and in mid-September a bunch of bike geeks heading to Mandalay Bay Trade show floor to check out the latest from the cycling industry.  After a sufficient amount of coffee, we stumbled into the trade show with an agenda filled of appointments, seminars, and vendors to visit.


As in typical years my schedule revolved around power meters, training devices, and the latest in bike fit technologies.  I am not going to do a comprehensive review on the latest in power meters since DC Rainmaker did an awesome job of that on his blog but I do want to highlight a few interesting developments in the power meter market.  First off, the Brim Brothers shoe mounted power meter is finally coming to market.  This is a system that has a force plate mounted under a Speedplay Zero cleat with an accelerometer pod mounted on the top of the shoe.  The obvious benefit of this system is the ease in switching your power meter from bike to bike without any of the compromises the left side only systems make in their data accuracy.  Even if you don’t have multiple road, time trial, or triathlon bikes the $1000 price tag, ease of use, and lightweight will make the Brim Brothers system a strong player in the power meter market.  Of course this is a first year product and reliability in the real world is yet to be determined.  Having followed this project for a while, I am very optimistic that it is going to solid product.

The other trend we are seeing in power meters is the number of single sided systems coming to market.  Garmin debuted a left side only Vector, 4iiii has a new system that can be set up single sided, Stages continues to strive in the PM market, and Rotor continues to offer a single sided option.  There are positives (less cost being the biggest) and negatives (assumption of symmetry) to these systems.  I do think they are going to be somewhat temporary as prices continue to drop, and coaches and athletes see the benefits in more accurate systems, but for now they are a good “gateway drug” into training with power.

The new Vector S offering a cheaper, single sided option in their pedal system.

This was also the first year that wearable physiological sensors officially hit the market.  Moxy Monitors has a wearable muscle oxygen sensor, and BSX Insight introduced the wearable lactate threshold sensor.  Measuring muscle oxygen concentration is relatively new and the usefulness of it is still be determined, but measuring lactate to determine fitness and relative intensity levels is very well established.  Having the ability to train by lactate levels without having to put a drop of blood on a test strip is a very interesting concept.  From a coaching perspective, having real-time lactate levels and power data would be amazing!  Not only would we get the external output of an effort, but also the internal output and be able to analyze the correlation between the two over time.

BSX Insight wearable lactate analyzer

On the bike fit front we continue to see new tools being offered by Retul, Cyclologic,, and Guru.  While there are some really flashy technologies coming out, all of those companies emphasized that fitter education has to come first and the tools are secondary to the knowledge of the fitter.  That is awesome to see that change from the industry and the desire to have athletes more comfortable on bikes.

The other awesome trend we are seeing in companies with contact point equipment is developing prescriptive processes to determine the best components for an athletes physiology.  This is primarily driven by Specialized and their refined body geometry line, but several companies have released their own systems to size saddles, bar shapes, and insoles. The most prominent company embracing the prescriptive process is Fizik.  They have a dedicated “spine system” to determine saddles and appropriate bars.  Plus you can find the animal in you…

fizik spine conceptRight now all of those systems are limited to their own brand but I wouldn’t be surprised to see universal prescriptive processes coming out to determine the best equipment from a variety of manufacturers very soon.

Check out all of our photos of the cool new shiny bits here.



Medicine of Cycling Bike Fit Symposium

Pressure mapping was one of the sweet new tools presented.

What an amazing week in Colorado. Last week I traveled to Colorado Springs for the Medicine of Cycling bike fit symposium held at USA Cycling. It was an amazing opportunity to share ideas and learn from some of the smartest bike fitters in the world. Topics ranged from the latest technologies used in bike fitting, managing knee pain, and optimal setup of contact points.  As a bonus we also got spend some time catching up with friends at the US Pro Challenge.  A good time was had, but the goal of the trip was to exchange ideas on bike fit.


Through out all the presentations there were a few common points that were continuously brought up. One of the most common was the concept that bike fit is process. It isn’t a one time deal. At a minimum, clients should expect two visits: the first initial fit and then the follow-up. This allows the client to adjust neurologically into the new position. Our bodies get used to functioning in specific patterns. When that pattern is altered it takes time for the muscles to fire efficiently again. Once the neurological adaptation has occurred we can then go back and reassess the position to see if further refinements are needed.

Some athletes also need more of an intervention than we can provide during a bike fit. Major issues may need body work done by a chiropractor, physical therapist, massage therapist, or mobility work performed by the client. For those athletes we will want to move them from an accommodated fit around their limitations, to an optimal fit after those limitations have been addressed. All fits done by Burnham Coaching include one free follow-up for this reasons.

Lots of time was spent assessing and addressing foot structure.

Lots of time was spent assessing and addressing foot structure.

One other important concept presented was the concept of tensegrity, a term coined by Buckminster Fuller. Tensegrity is a system that consists of independent units (bones) of compression connected by a net of continuous tension (tendons). Essential to this idea is the fact that changing tension on one unit will effectively change the entire system. A good analogy in bikes is that of a wheel. If one spoke looses tension than the entire shape starts to lose form. The same is true to the body. For example tight hamstrings can affect your neck or pressure on your hands; or your fallen navicular may be the cause of your sore knee. Everything is inter-related and just because you have an aching neck doesn’t mean your neck is the issue.  A good bike fit will help to isolate those issues and put you on a path to fixing them.  This is something we have addressed with athletes for years in our fit studio and important concept for athletes to learn.

Pressure mapping was one of the sweet new tools presented.

Pressure mapping was one of the sweet new tools presented.

As we go into the off-season for most cyclists and triathletes, now is the time to take a look at your position. There is a lot of time to become adjusted to changes, and adapting your bike fit to changes in your fitness. An initial fit going into the winter (and doing the necessary homework to move from an accommodated to an optimal fit) and a follow-up before the season is an ideal way to address your positioning on the bike.  Now is the time to get set up for an ideal season next year.  Contact us soon to get your position dialed.