Tri-Bikes/Time Trial

How to Fit a Tri-Bike or Time Trial Bike

Triathlete being fit with front view 


This article is focused on Tri- bike (TB) and time-trial (TT) bike fitting.  It is not intended to be a resource for bike sizing. Often these two descriptions become intertwined. However, anyone with interest in bike fitting or sizing should understand the differences. With that said, fitting a tri bike works best when you start with the right size tri bicycle frame.  At a minimum, a frame should be close enough to your correct size. Also, the position on the bike we will most often be talking about is with the cyclist sitting on the saddle in the aero position- forearms are sitting on the armrest and the hands are at the end of the aero bars (extensions) or what is often referred to as “in the aero bars.” This does not mean fit on the base bar or cow horn section of the bars is unnecessary.  On the contrary, consideration should be made in this area as it is the connection for starts, climbing, cornering and where most brake levers are found. We want to be able to help guide you to a position that you will, hopefully, ride almost all of the time- in the aero bars. If you are not able to ride in this position comfortably, we are going to suggest you need to change the fit.


Illustration 1 – Tri-Bike with the “target” connection points highlighted.

One thing we will not focus on in this article is whether you should be riding a tri bike vs. a road bike. For many, a road bike might better serve you and there is nothing wrong with riding a road bike in a triathlon.

When necessary, we will specify TB or TT bike for distinct or modality specific descriptions/reasons.  Most of the time we will use “TB.”  

Like all cyclists, athletes who participate in Triathlons, Duathlons and Time-Trials want to be comfortable on their bikes. However, unlike many road cyclists, the triathletes and time-trialists are rarely seen sitting up and relaxing…or are they? Hopefully not.

The geometry, and thus positioning, on a tri-bike is often quite different from a road bike. At BikeFit, we've developed our bike fitting curriculum to address a Duathlete’s and Triathlete’s specific needs. We do incorporate some of the protocol, especially with regards to hip angle, developed by Dan Empfield at SlowTwitch/F.I.S.T.  This is, of course, in addition to what we do for a typical fit (foot/pedal interface, seat height, stance width, front view, side view, etc.).

To provide some background, I draw from my years hanging around the “funny bikes” used in the ’84 Olympics when I lived and trained at the Olympic Training Center.  This was, of course, prior to the advent of “aero bars.”  Race Across American (RAAM) then showed what was probably the first version of an “aero bar.” Yes, it was the RAAM guys that really kick started this aero bar craze- not the triathletes as many folks like to think.  Several morphologies occurred as the tri folks picked it up. Shortly thereafter, a guy by the name of Boone Lennon came along and built a set of “areo” bars for a guy that raced in the Tour de France. This publicity really helped the “aero bar” become well received by ALL cyclists- not just the crazy long distance guys and the early tri folks. Then John Cobb helped me write what may have been the first published bike fitting manual for TT and TB in the 1990s, “The Bicycle Fitting System,” co –authored with Vint Schoenfeldt, PT. Today, I now also teach at SlowTwitch, a fabulous bike fit education program run by Dan Empfield who has taken the side view and put it into a much easier to digest format. Dan has put more time into tri bike fitting than anyone on the planet. It is important to note, Dan sticks to the side view perspective but also does a great job in helping fitters generate the best size frame (bike sizing) for their clients. Together SlowTwitch and BikeFit offer the most comprehensive Tri Bike fit in the world. Bike fitting that considers only the side view is like building a house and setting it on the ground with no regard to the foundation.  Fitting only the feet is like building the foundation but stopping before putting up the walls and roof.

 Illustration 2 – the early days of aero bikes

The illustration above is an early version of a time-trial position. This is also fairly indicative of tri bikes at the time that went for the aero position. In this photo is Chris Kostman of Adventure Corps- Today Chris is promoter of the Furnace Creek 508.  He is also one of our BikeFit Pros. You can bet he does not fit people like this today.

So, what are some of the differences with Chris’s fit and a tri fit today? For one this was before we really started looking at the foot-pedal interface.  Chris would point out he was at the forefront of setting the cleat further back on the shoe than most prescribed. I would argue he did it before shoes were ready for that change. With the advances in cycling shoe technology, indeed cleat position changed. More on this when we talk about the foot-pedal interface below.  

Two BIG things should come to mind when we look at Chris: hip angle and shoulder angle. The saddle is further back than most tri bike fits today. This results in a more acute hip angle which is exacerbated by the extra-long reach to the bar.  Also notice the shoulder angle. This is WELL beyond the typical 90 degrees or so we like today.

Let’s not clobber Chris too much.  Remember, this was the early years. Lucky for most of you, this position is a thing of the past. People ahead of you suffered so that today you should not have to. A good tri fit should be comfortable for as long as you need to be on the bike. Of course a good comfortable bike fit will help you generate more power and you will be more efficient.  In the end, you should then be on the bike less J with a faster split.

What makes a road bike different from a tri bike?

From Dan Empfield   “The reason is that the forward position places the rider over the cranks further and puts him/her in an aerodynamically sleek position. The position also saves key muscles for running. Road bike seat tube geometry is geared toward making efficient use of all leg muscles, especially the hamstrings, which is an important muscle to save for the run. Tri-geometry makes more use of the quads to generate power.”

I do believe most everyone agrees with Dan's first statement- this forward position "places the an aerodynamically sleek position."  It is Dan's second statement where I've found some disagreement among professionals.  Some studies have indicated there is little to no noticeable change in physiological measures between a shallow seat tube angle and a steep seat tube angle. This was done by Ben Reuter and David Pascoe and published in 2006 ‘Medicine & Science in Sports and Exercise.’  Is that the same as saying “key muscles?” You can decide. I think most professionals agree with the use of the forward (aero) position.  However, I’m not sure all are in agreement as to its exact benefits.   However, I think before we get to that part of your triathlon (the third event), a good tri bike position should also be comfortable for someone just getting out of the water and onto the bike. I never hear this talked about. All the chit chat is about getting off and having to run. Yes, that is important.  However, the run is a long ways away from when you get on the bike and start doing the highest speed section of your race. Let’s endeavor to place the athlete in the most comfortably aerodynamic position.  In the end, what is the point of improved aerodynamics if you are unable to generate an ounce of power?

I’d like to suggest when getting on a tri-bike fit, swim as close as possible or just prior to your bike fit. There are actually a few places on the planet that will set this up for you. Ask if this is an interest but know places like this are few and far between.

The tri position tends to be more static then a road position. In other words, the cyclist spends less time adjusting or altering their body position while riding.  So the main focus is, for the most part, focused on one position on the bike. Dialing in this single position actually becomes a bit easier than a road fit. Yet, people sometimes suggest a tri-fit is more difficult.

Sizing a TB is also not as complicated as you may have been led to believe.  However, TB sizing may take a slightly different trained eye than road bike sizing. Fitting a tri bicycle comes down to the contact points (connection points) between the cyclist and their bicycle. These NINE contact points (yes there are nine places you touch a TB) are: right and left pedals (1,2), the saddle (3), right and left forearms (4, 5), right and left extensions (6, 7) when in the aero position and right and left hands (8, 9) when upright in the base bar or cow horns. So even if your bike is not the correct “size,” as long as you get the connection points in the ideal place you can still achieve a good and comfortable bike fit. Sizing on a TB, however, probably needs to be more precise than sizing on a road bike. The choices, although many, in TB accessories can be a bit more limiting in adjustability.

A proper bike fit has more to do with the saddle, handlebars, brake levers and hoods, stem and, most importantly, shoes, cleats and pedals than the actual frame.

Illustration 3 – Tri Bike with the “target” connection points highlighted.

As long as you get the equipment within the target range you can achieve a proper and efficient bicycle fit.
Keep in mind selling bicycles is the business of a bike or tri shop and their focus is typically on the bicycle and bicycle frame. This is not necessarily a bad thing. Sometimes bias can enter the picture. Hopefully this bias does not have a negative influence on the bike fit.  If the shop you are choosing to purchase your bike from is not well versed in fitting (or positioning), we strongly suggest you connect with someone who is before making your purchase. A good fitting bike may cut more time in your triathlon than any other adjustment you may make (proper training notwithstanding

The core business of BikeFit does not rely on selling you a bicycle. Rather, it focuses on a great bike split.  Our unique position enables us to give you an unbiased opinion of the bicycle (brand, model, etc.) you ride. We just care that your bike fits you.

Bicycles are symmetrical (other than one crank sometimes being a little wider-from-center than the other) whereas the human body is not. That means getting the connection points into the target range is just a start to the bike fit. Not only do these points need to be in the correct area but you need to fine tune each specific connection (hit the bull’s eye). You need to assess and fine-tune the location of the bike part as it meets your body.  For example at the hands, just because you may have the correct length and angled stem does not mean you have the right shape and size of base bar or elbow rest and extensions, the proper bar tilt/rotation, and/or brake levers and their location on the handlebars. Or for the feet, because you set the cleat fore/aft position does not mean its rotation, tilt and stance width are also correct.

The ultimate result between the bike and your connection to it is when the bicycle basically disappears. Once you no longer notice the bike and the only thing on your mind is your ride, the scenery and/or company, only then do you have a good bike fit. Similarly, while a triathlete may not care about the scenery, they do care how fast they are going. When a triathlete is not conscious of their bike (it disappears), they are experiencing a great bike fit.  Don’t fight with your bike!  Use your motor to tear up the course.  I guarantee you if your bike “disappears” during your triathlon, the transition to the run will go much more smoothly.
















Getting Started

As previously mentioned, the (cyclist’s) body contacts the bicycle at 9 points:  hands (4), forearms (2), pelvis (1), and feet (2).  The location of the feet, pelvis, forearms and hands dramatically impacts comfort and efficiency on the bicycle. There are several pieces of equipment on a bicycle that are used or adjusted to find your ideal position on your bike:

  1. Pelvis – saddle selection, height, fore/aft, tilt and sometimes cycling shorts.
  2. Hands and forearms – base bar, forearm pads, extensions, brake levers and shift levers, which are all connected to the bike with a stem.
  3. Feet – pedals, cleats, cycling shoes and occasionally crank arm length.


Saddle Selection
Rarely do bicycle fitting articles mention saddle selection. The reality is this is the first step before making any adjustment to the seat height, tilt or fore/aft position. Riding with the wrong saddle can compromise your ideal cycling position dramatically.

As simple as it sounds, the best way to find the most comfortable bike seat is to sit on it. The problem is switching saddles is both time consuming and difficult.

Changing a saddle can take up to 15 minutes per seat which means most people make a seat choice by pressing a finger into it to test its firmness or softness. Another option is simply choosing a saddle based on what is advertised. Some saddle manufacturers have done a nice job with their design and a fabulous job with their marketing.  Unfortunately, this still doesn’t tell you which saddle is ideal for you.  Fortunately, we have solved this problem. At BikeFit we built a fitting tool called
SwitchIt™ that quickly and easily allows you to test as many saddles as you’d like by sitting on them:


Not all shops have SwitchIt so you’ll need to ask for it or find another bike shop that does. When you find a shop with SwitchIt, try to set the position on their sizing bike or stationary bike that has the SwitchIt mounted it to a similar position as your tri bike.  Try as many saddles as you like until you find the one that fits best before you make your purchase. It may come as a surprise that the seat you currently ride is not really the best saddle for you. Let your tush be the judge!

Beware of other ways a bicycle dealer may guide you in your saddle choice. Some bike shops may have you sit on a device that takes an impression of the width of your sits bones. If this device actually works, the best information it ‘suggests’ is how wide or narrow of a saddle you ‘might’ like. Unfortunately we can share with you story after story where this device does not provide information for a good saddle choice.

Illustrations 4 - As you can see sitting on bike is not like sitting on a box

As mentioned, a saddle that is not right for you can compromise your position on the bike and, of course, be uncomfortable. Click
here to see just how much a difference in saddle choice can make.

As you try to find the right saddle, keep an open mind. Some shops may start you down a saddle choice path by pointing out saddles designed for triathlon or for men or women specifically. However, some triathletes find a road saddle more comfortable and some men may find a so-called women’s saddle more comfortable or the other way around. Either way, please be ready and willing to try ALL kinds of saddles.

Are seats with a cutout good? It depends. It seems that in the past some seat manufacturers added a cutout to make up for their less-than-ideal saddle design. Many saddles did not offer the ideal support in the right area. A good-fitting saddle may not need a cutout if the support is in the ideal area for you. Where is the ideal area? It varies from person to person.  In general, for most of us (male or female) it means not too much pressure in the front or in the center of the saddle.  For some, sitting slightly off to one side may be the answer.  Bike fitter extraordinaire John Cobb often recommends positioning the nose of the saddle to one side.









Illustration 5– tip of saddle rotated to the right. To see more about John Cobb today:


Ultimately a cutout seat may prove the most comfortable. But don’t discount those saddles without a cutout before trying them first. You may surprise yourself as to which feels best.

Saddle Tilt

Is a level saddle the best position for you? It may be ideal for some but probably not for every triathlete. A lot of people tilt the saddle nose down thinking it will aid their comfort. If you must tilt the nose down more than a few degrees you may not have the right saddle and/or the overall bike fit is likely too far off. Too much downward tilt usually results in your pelvis sliding forward. This leads to hand, elbow, forearm, triceps and shoulder discomfort or pain. It sort of has you pushing your pelvis back from the bars several times in a ride. Some people will also feel like they are pedaling more with the tops of their quads (just above the knee).  While not as common, some saddles feel better with a slightly upward tilting nose. The best adjustment for your saddle really depends on you and on the saddle itself.  So don’t get hung up by someone saying it is “supposed to level” or “tilt” this way or that way.  Rather, adjust to what feels best.

Saddle Height

The starting point for most do-it-yourself bike fits is typically saddle height. Sit on the saddle with one leg hanging free and your pelvis level—not one hip tilted higher or lower. Your hanging leg’s heel should just scrape or touch the pedal when the pedal is at the very bottom (6 o’clock). Once you slide your foot back to bring the ball of your foot to the center of the pedal you should have a slight bend in your knee. 

Illustration 6 - Heel Scrape

In our experience the properly bent knee should have between 27 and 37 degrees of flexion from a straight leg. Typically, most people have greater than 30 degrees of knee bend at the bottom of the pedal stroke. The Empfield – F.I.S.T guide will suggest even a lower saddle height range. I am sure collectively we feel that almost never will you see someone needing to be taller than our ranges. Occasionally you might see someone lower but that will be rare.  If your hips rock a little when you pedal, lower the saddle a couple millimeters and test again. Repeat as necessary until you eliminate this rocking. You may be someone that just rocks.  Don’t feel like the Long Ranger.  You are not alone. This may be a point to consider shorter cranks. If you are on a fit bike with adjustable cranks, shorten them and see what happens.

While there are formulas that take into account your inseam measurement, they generally do not produce any better result than this heel scrape method.

We recommend using a
to accurately measure knee bend. Here is a goniometer checking knee flexion or the bend in the knee at the bottom of the stroke:

Illustrations 7a & 7b - Goniometer measurement and proper knee angle  

Can saddle height be set to the exact millimeter? It is worth noting that saddle height is never the same even for the same person. What do we mean by this? What happens if they wear a different pair of cycling shorts? That precise measurement is now not so precise. Does the “millimeter measurement” account for the wear and tear of a saddle that has been ridden for a long period of time? What if the rider feels tight one day, rested the next day, or they wear additional clothing to accommodate for cold weather? The list is nearly endless. Bottom line: the millimeter adjustment is not as important as you might believe.

Saddle Fore/Aft Position...
For years the common thinking for saddle fore-aft positioning was determined by the knee over pedal spindle (KOPS) positioning. The KOPS fit is done by placing one foot forward (3 o’clock) with your crank arms parallel to the ground and then insuring the forward knee cap is just over the center of the pedal (see picture below). For some riders this method will maybe work well enough for a road or mtn bike fit but that is a “maybe” at best.

Illustration 8 - Knee over Pedal Spindle alignment








Many people use a plumb bob for this measurement (we did at one time). We have found a laser to be easier and far more precise. While the right leg in the photo above is closest by using a laser the rider can spin the other leg forward and check the fore/aft on far leg as well without moving the laser. This is also a “hands free” technique.  With a laser, the fitter is able to make an adjustment or simply step back and take a look.  This is not possible with a weighted string hanging from the knee. Today we use this more to see if one knee is further forward than the other but NOT to check the actual saddle fore-aft position (especially on a tri bike fit).
Unlike road or mtn bikes, KOPS is NOT a starting point for tri bike fit. The modern method we subscribe to is a modified (but fairly close) Dan Empfield or Slowtwich approach. As mentioned above, my early influences come separate of Dan, having lived at the Olympic Training Center (OTC) in Colorado Springs when funny bikes were first being made.  I was also influenced by working with aerodynamic guru John Cobb. We put a lot of John’s info in our first bicycle fitting manual, possibly the first fitting manual on tri bike fit.  It is not that tri bike fitting was not talked about.  But finding a manual for one was next to impossible.


Illustration 9 - A bike that may have been used in the 1984 Olympics – notice the small wheels



There is an exception to the fore-aft saddle position for time-trial bike fitting-or for any bike that needs to be UCI legal. Because of this, it is actually easier to fit a time trial bike than it is a tri bike- one of the driving aspects or fit parameters is automatically set for you. I am not saying this is a good thing but rather an easier thing.








Illustration 10 – saddle set at 5cm behind the center of the BB


For USAC or UCI races or time-trials, simply set saddle height and put the nose of the saddle 5cm behind the BB and “Voila” you have your seat position for a time-trial bike. There are other parameters to follow. Just to make things more complicated, the UCI has a jig and your bike needs to be set up within the guideline of this jig (or template). Yes, it is sort of like a template for a stock car.


To see what this jig sort of looks like here is a bike that is set up illegally for UCI/USAC racing.


Illustration 11 - The saddle is too far forward for UCI and USAC racing.

 Illustration 12 – As you can see, it does become even more involved for a UCI bike.


Additionally, not shown in this illustration are several angles and positions of the cyclist on the bike that must adhere to UCI guidelines.

Upper Body Positioning:  Pelvis – Hands  – Forearms


Upper Body Positioning

The upper body is driven by two angles- the hip angle and the shoulder angle. Get these two angles close and chances are most people will feel comfortable in a tri bike position.  Your 3 landmarks for measuring hip angle are the (1) center of the bottome bracket (BB), (2) greater trochanter, and the (3) acromium process (AC Joint).










Illustration 13 – Hip Angle





And if you are not sure where the AC joint is located, Arland Macasieb, a top triathlete and Red Level BikeFit Pro, will point it out for you.

Illustration 14 – Notice the extension arm of the goniometer tool is in-line with Arland’s finger. To see more about Arland go here:

Illustration 15 – Ken Call DPT, a triathlete and BikeFit Pro shows us a 90° shoulder angle. Ken works for Therapeutic Associates out of Kennewick, WA. Here is a link to see more about Ken:


Illustration 16 – Before and After


On the left the cyclist demonstrates a hip angle above 100° and a shoulder angle of more than 90°.  On the right (post-adjustment) you see a hip angle closer to 100° and a shoulder angle closer to 90°.  This was achieved by moving the saddle forward (also raising it a few millimeters to compensate for the forward movement- anytime you move the saddle forward you are also lowering or decreasing the distance to the pedals).  We lowered and shortened the stem, as well as, shortened the reach a little on the extensions.  This took a few adjustments to the saddle, a few at the stem and one at the extensions.


There were no changes in bars for this fit. The only new piece of equipment needed was a stem. Of course we used a sizing stem to help us get to this position. A sizing stem is a MUST when doing ALL bike fitting. If your fitter is not using a sizing bike, chances are you should be asking for the sizing stem to be used during your fit.  Keep in mind often you may need to change the bars to achieve these angles. That change may be the base bar and the extensions along with the forearm pads.


Another way to look at this upper body fitting is to think of getting the 100 and 90 set. Once set you simple rotate the entire upper body forward or backward. Perhaps this is one aspect where a fit bike like the Exit bike may make this easier.

Illustration 17 – Rotating the entire body in unison on the bike


But wait!  Empfield says the shoulder angle should be close to 80°.   This is true.  However, the protocols of F.I.S.T simply use different landmarks when measuring shoulder angle.  So yes, Slowtwitchers tend to look for 80°.  At BikeFit we use 90° for most all bike fits.  Road, mtn and tri remain consistent with our shoulder angle measurement, using the same landmarks. We do not change our number and landmarks just for one style of fit. The shoulder angle is basically the same.   In other words, we completely agree with each other.


Base Bar

Before doing all of the above you need to select a base bar. The base bar used to be referred to as pursuit bars or cow horns. In case you haven’t noticed, we use base bar or cow horns most of this time in this article.  


Base Bar Width (Cow Horns)
The easiest way to select the handlebar’s width is to pick up different width bars in a bike shop and grab hold of them. Place your hands on each of the forward “reach” areas. Try both narrow and wide bars. Once you have the bars in hand, move them down near your waist, straight out in front of you and then bring them toward your chest. Do this with a few bars and usually you’ll find one that feels better than the others. I know it sounds silly but it really is a great guide. If you are still unsure between two widths put the bars up to your armpits and choose the ones that are most closely aligned. 








More to come :-).  This is a work in progress.  If you have gotten this far, send an email to identifying the 9 contact points on a tri-bike and receive a coupon for your next order!

Ready to get your Tri-Bike/Time Trial Bike fit?