Bike Fitting has received a lot of attention this year and for good reason; proper bike fitting yields positive results that can be measured.  Even more important is the exposure bike fitting has received as a benefit to every level of rider.  If you’ve been checking in with some of our blogs, and I hope you have, you’ll find perspectives from riders new to cycling to seasoned veterans getting back on the horse again.  My flailing knee style I developed on a mountain bike was quickly corrected when I experienced the benefit of a fitting and now I am able to push out 30+ mile rides under physical comfort.  When it comes to bike fitting, one is bound to discover many theories about how to attain proper measurements.  Measurements that may ultimately result in selecting the right bike and making adjustments that will improve the rider’s experience.  To the innocent bystander the instruments and tools used may look a bit medieval and strange as to how they work.

So what are the three essential tools that every fitter needs? In my survey of fitters almost all of them settle on the X/Y Tool, the goniometer, and the plumb bob.  Many fitters are quick to note the importance of utilizing a whole gamut of tools, including the fit bike, but these tools are where the basis of fitting starts.

#1 The X/Y Tool

So let’s take a closer look at each tool and why fitters consider it to be essential.  According to Bob Seastrom, a certified fitter, the Purely Custom X/Y Tool is a great way to document a customer’s bike.  This tool is able to give you X/Y coordinates on a lot of different areas of the bike quickly and easily, it is quite accurate and is able to make it very simple especially when you are trying to duplicate a bike and have that next bike feel exactly like the last one.  One of the features is when you’re doing the handlebar measurement it has an adapter to fit a 31.8 handlebar or you can actually flip the attachment down and it converts it to a 26.0.  If you want to do stack and reach, you can flip the attachment up and now you are able to measure stack and reach on the bike.  Having just one knob makes it very simple to be able to move the measurement bars up and down and with a little tension, it will actually hold in position while still able to be moved.  When you get it in the right position, turn the knob a little more and it will lock down and you are able to read your measurements on the tool.  It does have one other measurement as well on it if you are doing nose to saddle to center of the bottom bracket, this scale comes into play.  There are two different pieces that go into the crank, one that actually fits into a standard shimano crank arm and then there is also a more universal tool which will fit into and center in on everything else.  This is a very nice tool, very easy tool to use, wonderful for documentation.  It’s able to make your fits very, very accurate and very easy to duplicate.

How To Use the X/Y

In a little more technical explanation of the X/Y tool, Paraic McGlynn, founder and chief technologist for Cyclologic,  the Purely Custom X/Y Tool allows the fitter to take an accurate X/Y coordinate of the position of the center of the rails of the saddle in space.  This allows the fitter in conjunction with the saddle angle to very accurately position that saddle in space relative to the bottom bracket.  Each of the sliders on the X/Y Tool move vertically and they also move horizontally so you can adjust them back and forward.  So every type of bike, be it road, mountain, track, or time-trial can be accurately measured.  The X/Y Tool has two sets of levels that allow you to increase the accuracy of your measurement.  The X/Y Tool is invaluable for taking data off a bike and comparing that data to either an existing fit or transferring that data to an existing bike.  The X/Y Tool can be used to mimic a person’s bike on the size cycle. So if a client came in for a fit, taking the X/Y coordinates of the bike allows those X/Y coordinates to be transferred to the size cycle more accurately.  Once those dimensions are transferred to the size cycle you can analyze the current position and you can make sure you understand what is happening on their bike currently.  With a bike that has adjustment issues, i.e. there isn’t enough stem, length, or angle, or space or combinations to get into a certain position, taking that X/Y position off their bike could be a good starting point to get going on the size cycle.  The X/Y tool also contains a variety of different pins to suit different bottom bracket configurations.  The dimensions are taken from the non-drive side of the bike and these different pins facilitate the compatibility with different types of crank and bottom bracket configurations.  When beginning to take an X/Y measurement, the first thing to do is to select the correct attachment to interface with the bottom bracket.   Once the X/Y Tool is placed into the bottom bracket with the appropriate adapter then navigate the tool so it is exactly in the right place to document the center of the handlebar.  Once the X/Y Tool is in the approximate correct position, adjust the pressure on the spring washer and the tool will allow you to make some small adjustments.  If the spirit levels are not level, work on the vertical column until it is aligned and straight, then work on the horizontal column using the spirit levels.

Tighten down the center knob to hold the measurements, remove the X/Y Tool from the bike and read the measurements off the bike.   Read the Y measurement below the arrow on the vertical bar and the X handlebar position next to the arrow on the horizontal bar.  That gives you the X/Y coordinate of the handlebars in space relative to the bottom bracket.

#2 The Goniometer

The goniometer is an innovative tool in the assessment of range of motion.  Its telescoping arms can extend to 28 inches to measure large joints and retract to 8 inches to measure all but the smallest joints.  Paraic also explains the goniometer:  A key part of a static bike fit is to establish the relationship between key landmarks on the body.  We use the goniometer to establish the key landmarks on the bike for leg extension, for torso angle, and several other things during the fit process.  The Purely Custom goniometer is special because of two major reasons.  One, the arms telescope which allows you to reach right out to anatomical landmarks, and the second feature is that it is color coded for leg extension so that when you get it into the correct range which would be between 25 and 35 degrees,

in the viewing window you can see exactly when you’re in the right range.  Using body target stickers to note anatomical landmarks marks the points to lineup your goniometer and measure the interaction between the hip the knee and the ankle.  Extend out each arm of the goniometer so it is long enough to reach the landmarks, then site the knee and adjust the hip first and then the ankle and then take the reading from the window on the goniometer.  If the goniometer reads within the range then we know the saddle is at the proper height.

#3 The Plumb Bob

The Purely Custom Plumb Bob is our third essential tool, sometimes called the “sexiest” plumb bob and although Paraic has no comment about that aspect he does emphasize the plumb bob is a key piece of the fit process when doing a static fitting, and for establishing where the tibial tuberosity is relative to the center of the pedal axle. Using the Purely Custom plumb bob that is weighted to the lower portion with a brass tip allows the plumb bob to become steady and gives the fitter a clear view of what is happening relative to the pedal axle.   In some cases it is nice to use the plumb bob where you can really see the position relative to the pedal axle.  It’s helpful for the fitter to be able to see the pedal axle and also where the plumb bob falls.  As the cyclist changes their position you can start to see the plumb bob either shifting toward the pedal axle or further back.  Throughout the process the purely custom plumb bob is designed to remain steady.  There are fitters out there known to use things like a socket on a string and other interesting means, but when you see how stable a good plumb bob becomes stable, there just isn’t any comparison.

So those are your three essential fit tools, the basis of a fitting and of course they are all available through Purely Custom.  Purely Custom also offers three different Fit bikes including the Fit Bike Pro 1 that is used to fit some of the top cyclists in the world.  If you’re looking to enter into the world of bike fitting, we would encourage you to invest in your education as well.  Cyclologic offers several levels of education which are essential to how to use fit tools properly and the proper measures to accomplish the best bike fitting possible.