Shaking Off Numb Hands

First published in Cycling Utah / Cycling West August 2017

So far this year the most common issue I have encountered as a bike fitter are cyclists experiencing numb hands. Many of you will have experienced occasional numbness or tingling while cycling, but for some of you this is a recurring, persistent experience that detracts from your ability to go the distance you desire or enjoy your riding as much as want to.

If you are frustrated with regularly having to change hand position, or shake out your hands to restore feeling and circulation, some insights into the contributing factors may help you find relief. Numb hands are common to both road and mountain bike riders, and a rarer condition in tri /tt riders who are in the aero position. As a fitter, sometimes I am able to resolve the issue immediately, and sometimes it takes multiple trials and tries.

Which part of your hands go numb, whether it is one or both hands, how long it takes before the onset of tingling or numbness, what of riding terrain it occurs on (pavement, dirt, uphill, downhill) and how long before the issue resolves once you are off the bike are all important clues for exploring and solving this problem. If the numbness is intermittent, takes a few hours of riding before it commences, and/or quickly resolves once you are of the bike, then this is a mild case and probably requires only a small change to be eliminated. However if you get hand numbness within an hour of riding; it occurs on every ride; and/or doesn’t resolve for a few hours or even until the next day, then you are at high risk of developing long term nerve damage (peripheral neuropathy) and there is something significantly wrong in your bike fit position, or riding technique.

Preventing hand numbness requires problem solving back up through the cause and effect chain. You experience the effect. The cause of hand numbness is nerve compression. There are 3 primary nerves servicing the hand (radial, medial and ulnar), and the area of the hand that experiences numbness is a clue as to which nerve or nerves are involved.

The cause of nerve compression is excessive and sustained pressure on the nerve. As supporting weight causes pressure, the problem is rephrased as “what is it about this cyclist’s position that is resulting in the hands bearing too much weight?”

The 3 primary reasons are:

1/ a handle bar too high and/or close to you.  Your upper body wants to be more forward and down to stimulate core muscle and back fascia engagement to set up for generating power, but is prevented from doing so.  Your hands are pushing back against the bars to counteract the forward forces of your torso.  Most likely the bars are too high in relation to your saddle. Often hand numbness goes hand in hand with shoulder tension in this situation.  Flip your stem down and/or move spacers from under the stem to the top. You may also need a longer stem. This will give your upper body more space to function in.

2/ the saddle is too far forward in relation to the bottom bracket.  Without your hands on the bars to hold you up you would topple forward off the saddle.  Too much of your weight is being transferred to the handlebars for support, instead of being directed through the saddle and your legs. This creates unnecessary weight and compression on your hands.  You need a “lighter touch” on the bars. Move your saddle back (even 10mm can make a big difference). Can you ride with no hands without tipping forward off the saddle?

3/ Handlebars too far away or too low. This is the opposite of number 1, and similar to number 2 but for a different reason. Too much of your weight is being transferred from the saddle to the bars and you are having to “hold yourself up”.  Often hand numbness is combined with neck tension in this situation. To transfer weight back into the saddle and legs you may need a shorter stem; stem with a steeper angle; more spacers under the stem; or a handlebar with a shorter “reach”.

In addition to these 3 primary causes, there are several smaller adjustments that can also have a big effect – for the better.

3 secondary factors:

1/ saddle tilt angle.  A saddle that is too “nose down” serves to transfer load to the bars as you subconsciously push back on the bars to prevent yourself from sliding forward on the saddle.  This may also cause some IT band inflammation as the legs are also being called upon to snap you back into place on the saddle. Even half a degree of saddle tilt adjustment can fix this. It’s not to say your saddle should be perfectly level (this depends on you and the saddle type), but it will usually be close to level.

2/ bar ergonomics. The rotation of the handlebars, the position of the hoods or grips, and the in/out rotation of hoods all affect weight distribution and pressure on the hands.  A small tweak to any one of these can have a nuanced but profound effect on pressure distribution and therefore nerve compression. You should feel even pressure through your hands, not have it concentrated in one area.

3/ getting gripped.  If you are novice rider on pavement or trails, you may be feeling nervous on descents, and that can manifest as a death grip on the bars. You are creating pressure and nerve compression from muscle tension that is excess of that needed to control your bike. You need a grip on the bars, but not a death grip! This can also happen to habituated and experienced riders, perhaps more so on steep climbs. Cycling safely and comfortably requires many skills, and one of these skills is learning how much grip you need on the bars in different situations, and being able to relax your hands while still maintaining control.

1 hidden cause

If it is none of the above, then the cause may be a pinched nerve up in your neck. Yes, the main nerve that serves an arm exits the spinal column near the neck.  If you have had an injury to your neck, shoulder or collarbone, then this nerve may be compromised. Relief may be obtained by treatment from a chiropractor or PT, or a more thorough neural assessment may be needed by a neurologist.

The Wrap

As you can see there are many potential factors that can result in numb hands, and it can take some Sherlock-like skills to sleuth out the true culprit. Often the secondary evidence of “what else hurts” can provide a clue to the fundamental and underlying cause. In the absence of clues a trial and error approach may be needed to achieve the reasonable expectation that you can go riding without your hands going numb, and not have to shake them out for relief.


Getting started in triathlons – what bike do I need?

first published in Cycling Utah / Cycling West, July 2017

Of the 3 sports that comprise a triathlon, the cycling leg requires the most technical equipment, and is arguably the more intimidating sport because of this, particularly for competitors who come to triathlon from a running or swimming background. But cyclists are also faced with equipment questions and conundrums when considering participating in a triathlon. Do you need a special triathlon bike, or will any bike serve the purpose? And what’s with the low and stretched out position anyway?

The bike leg is in essence an individual time trial, followed by a run! Because competitors are not allowed to draft behind other riders and save energy, the way to go faster and have energy for the run is to reduce your wind resistance by riding in an “aero position”. This requires a different riding position, which means either a triathlon- specific bike, or modifications to an existing road bike. The longer the event, and/or the more competitive you want to be against yourself or others, the more significant this aerodynamic advantage becomes.

If you don’t have a tri bike, but are wanting to participate in a triathlon, here are some things to consider before investing in a tri bike:

Event Distance

Triathlons are generally classified by the total distance as either Sprint (12.4 mile bike), Olympic (24.8 mile bike), Half / 70.3 (56 mile bike) or Ironman (112 mile bike). Short distance events like the recently held Daybreak Tri and Dino Tri are popular for experiencing a triathlon and testing fitness, equipment and strategies. Unless you have your sights set on the podium, any bike you can put your hands on will be fine for these shorter events, even a mountain bike!

Your Motivation and Goals

If your aim is to do one triathlon and check it off your list, then there is no need to invest in special equipment. But if this is a sport you plan to repeatedly go in, and you want to be competitive, then having the right tool for the job is going to help.

Current Bike

If you have a road bike, you can use that for any triathlon, but you wont be as fast as someone with the same cycling fitness who is on a tri bike, especially in longer events. But many people do their first long event on a road bike just to make sure they are “hooked” before getting a tri bike.

Other Cycling Pursuits

A tri bike is usually a poor choice for group rides, club rides, non tri cycling events, and riding up and down canyons, due to the gearing, riding position and steering. If most of your cycling will not be training for or participating in a triathlon, then you probably don’t need a tri bike.

Time and Money

Triathlon is not a cheap sport. Entry fees, travel, training, and equipment all consume time and money. If you’ve got the time and money to go for it, then you probably want to maximize your enjoyment by having the right gear, and that would include a tri bike.

Converting a Road Bike to a Tri Bike. It’s not just a matter of slapping on aero bars. The frame geometry and riding position for a tri bike is quite different to a road bike. It’s difficult to have one bike optimized for both styles of riding. There are horses for courses, so don’t expect any old mustang to carry you to a triple crown. Which is not to say you can’t enter the race. Give tri a try.

Tips from the MOC Bike Fit Symposium

This article was first published in Cycling Utah/Cycling West September 2016 issue.

The annual Medicine of Cycling Bike Fit Symposium took place at the USA Cycling headquarters in Colorado Springs in mid August, bringing together a highly regarded group of bike fitters from around the USA, and further afield.

Presenters included sports medicine and bike fit advisor to Specialized Bicycles, Andy Pruitt; sports medicine and bike fit advisor to Trek Bicycles, Mark Timmerman; strength and conditioning coach, Greg Choat; Physical Therapists, fitters and educators Curtis Cramblett, Greg Robidoux and Brian Adams; Bike fitter since year 1, Happy Freedman; Californian fitter of note, Steve Carre; and the legendary John Cobb. Topics covered included overuse injuries of the lower limb; foot evaluation and intervention; pelvic, trunk and core assessment, influence of crank length on aerodynamic positioning; case studies and more.

Attendees encompassed bike shop owners, physical therapists, orthopeadic specialists, independent bike fitters, athletic trainers, and cycling coaches, making for a diverse gathering with a common interest. And that common interest is helping you – the cyclist – have a positive relationship with your bicycle. This relationship encompasses everything from injury prevention to aerodynamic advantage, including comfort, efficiency, power generation, and bike handling.

Here are a few notes of interest and relevance to share, to encourage you to think about your own bike-body relationship.

Saddle. You can’t fire a cannon from a canoe. Generating force and applying it to the pedals can only happen from a stable foundation, and that foundation is the bicycle saddle. If you are not stable and well supported by the saddle, you are not able to effectively generate power. Although force is applied at the pedals, it starts at the saddle (and with the core: muscles and fascia). A bike fit is saddle specific.  If you change your saddle to a different one, you have just changed your fit position.

Shoes. The only place you are mechanically attached to the bike is at the pedals. Shoe selection, in-shoe support, and cleat position are all important for not just foot comfort, but also knee protection. The number one issue with cycling shoes is their width, or lack of. Cycling shoes need to be wide enough for your feet, and sized for your arch length. The correct in-shoe support (semi custom or custom cycling orthotics) can do wonders for both foot and knee comfort by securing, stabilizing and supporting your foot in the shoe, resulting in positive effects up the kinetic chain. Insoles for cycling are not the same as insoles for running or hiking. The biomechanics of what the feet are doing are very different, and the support requirements are different.

Hands.  If you get numb hands riding, and the numbness goes away after the ride, it’s due to temporary nerve compression from too much weight on the hands. This can be from bars being either too far away and too low, the opposite! Aim for a light touch on the bars so that you are not being held up by the bars, nor pushing yourself back off them. Handlebar width is more critical for woman than men, and generally woman are riding on bars too wide. Shopping for gloves? Foam padding is better than gel padding for comfort, even though gel padding is marketed as being superior. Same for cycling chamois selection.

Fitness. Your overall strength and conditioning can be limiting you a lot more on the bike than you think. Improving core strength, range of motion, and stability (control through motion) off the bike all help when you are on the bike. Deadlifts are superior to squats for developing cycling power. You can’t stretch the IT band, but you can strengthen your glutes.

Aerodynamics. For TT riders and Triathletes, aerodynamics is very important, and a lower torso is generally more aerodynamic.  However the ability to get lower AND maintain power generation is constrained by the hip angle (femur to torso).  If you get low but lose the ability to generate power in doing so, you may in fact be going slower. The best way to get low and keep an open hip angle to generate power is to use short crank arms E.g. 135mm – 155mm.  When changing to significantly shorter cranks, increase the size of the chain-rings to maintain pedaling load feedback.  There is no evidence to suggest a correlation between a cyclist’s height and their crank length, and there is no correlation between crank length and power output. A side benefit of shorter cranks is to reduce the development of external iliac arterial fibrosis – a condition causing pain and weakness in one or both legs that has ended the career of quite a few cyclists.

Read another article on this topic by Mark Deterline, published in Cycling Utah here.


cleat adjustment

Bike Fitting for Mountain Bikers – Part 2

The following article was written for and published in Cycling Utah / Cycling West July 2016 edition.

This month I am going to delve into the primary bike fit adjustments on a mountain bike and offer up some do-it-yourself guidance for checking and adjusting your setup. Most of this is geared toward your cross country, endurance (not enduro), and trail rider, but much is applicable for any bike.

Foot to Pedal: If you are riding on flat pedals, then your foot is going to find its own position on the pedal, and mostly likely your foot will be further forward on the pedal than if you were clipped in.

If you are using cleats, then there are three positional adjustments:  forward/back, in/out and rotational alignment.  A general guideline for forward/back position is to locate the first and fifth metatarsal heads  (ball of foot for the big toe on the inside and the little toe on the outside), and to align the cleat bolt holes between these, or biased towards the 5th met-head. This gets you off your toes and moves the cleat contact pressure back under your foot for extra stability. For in/out, most riders will center their cleat between the lugs. That’s sound, but if you are large framed you might prefer a wider pedal stance, so move your cleats toward the inside in order to move your feet outward. You may feel more stable and balanced over the bike. Vice versa also applies. If you are slender you may want your feet closer together, so move the cleats to the outside, which moves your feet in. Rotational Alignment is the most subtle adjustment. If you are riding Crank Bros then there is so much float it’s rarely an issue, but SPD’s can be sticky and self-centering. If the cleat rotation is not ideal you could transfer stress up the leg into the knee. When riding you should have enough play to move your heels both inward and outward (to the point of release) equally.  i.e. when the cleats are centered in the pedals, the shoe angle should match your natural cycling foot angle, with no crank-arm interference. Check that the sole lugs are not impeding pedal entry and exit. You might have to shave off a bit of lug rubber to improve pedal engagement and release.  When the cleats are set properly, clicking in feels natural and automatic, and you don’t have to hunt around to engage in the pedals.

Butt to Saddle:  Always a potential sore point!  Firstly your saddle should be wide enough to support your sit bones. Sit on your saddle and prod a finger up into your glutes to find your sit bones.  They should be just inside the edges of the saddle, not on the edge or hanging off so that you are supported by perineal soft tissue. After width is profile. Your butt should automatically snuggle into a “home” position on the saddle that feels supportive, and not be squirming around trying to find the sweet spot. If you are squirming around, you may have the wrong saddle shape. If you have a flat saddle, try a semi-round. Saddle tilt will also affect comfort on the saddle, and to the bars. The general guideline is for a saddle to be level from nose to tail. On a hardtail a level saddle becomes nose down due to front suspension sag, so you might want to angle it up a degree or two.  On a full suspension bike a level saddle often becomes nose up if the rear suspension sags more than the front.  XC riders may want to then tilt their saddle down a touch, as there may be too much soft tissue pressure when climbing, but riders focused on the down usually prefer a nose up saddle to reduce the propensity to slide forward when descending.

Hands to Bars: I’m referring to direct contact here. i.e. the grips. Getting numb fingers or hands? That’s from compression of blood vessels and nerves in the hands.  If you are newish to mountain biking you may be too tense and “gripped”. Think about relaxing your hold on the bars a little bit, while still maintaining bar control. Consider ergonomic grips instead of standard round grips. They help spread out your hand pressure over a larger surface area and stabilize your wrists.  It may take several attempts to get them rotated to an ideal position, so be prepared to stop and adjust them on your first trail ride.  Hand discomfort can also be from bars that are too wide, bars too high and close to you, or bars too far out or down, and this will be usually indicated by the addition of arm, neck, shoulder or back tension and fatigue.

Saddle Position: Setting saddle height can be a compromise between optimizing uphill climbing power, and bike control and handling in technical terrain and when descending. If you have a dropper post, you can have it all.  Set the saddle height for climbing, because you can easily drop the saddle to lower your body mass, increase control and reduce the chance of being catapulted off the bike. Without the benefit of a goniometer or 3D motion capture system to assess leg angles, a DIY guideline is to be able to have your heel touch the pedal with your leg straight and knee locked out, without having your pelvis either drop down (saddle to high) or tilt up (saddle too low) from that position. This should result in a modest knee bend when clipped in. Riding on flat pedals? This method may leave you a bit too high, because with a mid foot pedal position you are operating a shorter lever from pedal to saddle.

No dropper post? If you are a non-competitive rider, the $20 alternative is the quick release seat post, which will enable you to enjoy good leg extension for ups, flats and rolling terrain, but lower your saddle for greater control and safety on technical descents. You are probably not sitting on the saddle during these sections, but this quickly gets it out of the way, with a bonus rest stop. Once your ideal climbing saddle height has been determined, mark the post at the top of the clamp for reference. Lightly score an alloy post, or use a colored nail varnish or grey sharpie marker on a carbon post.

Saddle forward/back should never be adjusted because of an issue with reach to the handlebars, although it directly affects that. This adjustment is about finessing your knee joint angles for wellbeing, being balanced on the bike (while seated), and attaining biomechanical efficiency for pedaling. The simplest DIY approach (which requires a second person) is the well known “knee over pedal spindle” method. It’s not an end in itself but is an indicator about these other factors, and a good starting point.

Bar Position: This is really about upper body comfort. Firstly, bar width. Just because they come wide, doesn’t mean you need to keep the width. If you experience shoulder or arm tension and feel “stuck” on the bike, try moving the controls and grips inboard a little bit and seeing how that feels and rides. Test ride different simulated widths before cutting the bars shorter. Bar height and reach can be adjusted by changing stems and the headset spacers. There is not a simple diagnostic DIY guide for this, but neck, shoulder and upper or lower back tension and aches often originate with a handlebar position that is not ideal for you. More commonly this is from a front end that is too low and long, but it can also result from the opposite. You don’t want to be supporting your upper body with your hands (that’s what the core is for), nor stiff-arming off the bars and holding your upper body too erect for comfort. The aim is a light tough on the bars with versatility to move around over the bike and keep your weight centered when riding on or off the saddle.

Bike Fitting for Mountain Bikers – Part I

The following article was written for and published in Cycling Utah / Cycling West June 2016 edition.

Google “bike fitting for mountain bikers” and peruse some forums and the results are high on opinion and generalities and low on useful information. As a competitive mountain biker myself, who experienced a transformational riding experience as a result of a bike fit (by someone else), I’m always intrigued by the general attitude of dismissal that mountain bikers have for bike fitting. Would all mountain bikers’ benefit from a bike fit? Maybe, which is a yes for some riders and a no for others. Compared to road cycling, there are a lot more variables at play in mountain biking, and fit is only one of those. It’s probable that some of the other variables are more limiting to a rider’s experience than their bike fit, but that is not to say fit is irrelevant.

Compared to riding a road bike on pavement, mountain biking on trails:
• Is more of a whole body workout and can be a lot more physically demanding
• Requires a more dynamic riding style of being in and out of the saddle and general movement on and over the bike
• Requires a different (arguably higher) level of bike handling skill
• Alternates between efforts of low power (descending when not pedaling) to high power (steep climbs)
• Has more “bike set up” variables including tire choice, tire pressure, suspension settings, saddle height (dropper post)
All this means mountain biking is more demanding on the body, but there is often frequent interruption to a static body position and steady repetitive action that are hallmarks of road cycling, and this often serves to disguise or mask any issues with a fit position.

The primary drivers of fit on a bicycle are: comfort, efficiency, power, aerodynamics and control.
Comfort is king because if you are not comfortable riding is not enjoyable, and if it is not enjoyable, why ride? OK, some of you will say for the suffering, because you like to suffer. But there is comfortable suffering and uncomfortable suffering. Comfort also impacts all the other fit drivers. What’s comfort? The absence of aches and pains, both short term (during and after a ride) and long term (maintain healthy joints, muscles and connective tissue). Aches and pains can be a result of:
• Being out of shape for the duration and intensity of riding you are doing
• From pre – existing injuries, or functional movement limitations from modern lifestyles
• A poor boy position on your bike, creating bio – mechanical and equipment – induced stress.
If you cannot go mountain biking without a dose of Advil before, during or after, then something is up. Improving comfort may require getting in shape by not only riding regularly, but also doing off bike strength and conditioning training, which could include body weight movements, weights, yoga or pilates. If discomfort persists when you know you are in shape, then the cause may well be equipment –induced, i.e. your body position on the bike.

Power and Efficiency are going to be determined by your physical and physiological conditioning, pedaling technique, terrain reading and gear selection. If your saddle height is too low or high, then that can detract from optimal power generation, and if you are too cramped or stretched from saddle to bars, then that can detract from efficiency and comfort, but there may be a lot to work on before your bike fit position becomes the limiter.

Aerodynamics is largely irrelevant for mountain bikers, but may factor in slightly to long distance endurance racers.

Control is about being able to safely handle your bike, negotiate the terrain, and stay upright and on the trail. It’s about maintaining traction, cornering, descending, climbing, and negotiating obstacles by being able to move your body about the bike by keeping your center of mass low and balanced. Control is almost assumed on a road bike. On a mountain bike it is of critical importance, and should not be overlooked. Other than bike style and geometry, the big factors affecting control are rider skill, bike set up and bike fit.
Rider skills camps have boomed in popularity in the past few years as many mountain bikers have realized their bikes are way more capable than they are. Bigger gains can be had from learning how to ride your bike better, not by spending up on the latest heavily marketed product innovation. If control is lacking, then it is likely that riding skill is also lacking. Mountain biking is not an intuitive natural activity. It takes learning and practice.

Bike set up and bike fit are closely linked, and a thorough mountain bike fit will include attention to set up. Set up deals with the mechanical variables of suspension setting, tire selection and pressure. Bike fit deals with your direct contact points to the bike (feet to pedals; butt to saddle; hands to bars), and your body position on the bike. Being centered and balanced on the bike and able to easily move around over the bike is very important for maintaining control. If your center of mass is too far back, the front wheel will have a tendency to wander. Uphill this will make it harder to maintain a line; and in corners the front wants to slide out. If your center of mass is too far forward you can lose traction climbing, have trouble unweighting the front end to negotiate step-ups or washouts and be more prone to endo-ing on technical descents. Now a lot of this has to do with skill, but a better position makes the application of skill easier, and with less body input.

So would you benefit from a bike fit? Probably not, if it is your fitness or skills that are holding you back, or you ride easy trails at low intensity for shorter (under 2 hours) time periods. But if you have persistent aches or pains; you have bought a new bike and your bike control feels worse, not better; or you have competitive intentions and want to optimize your potential, then give it some consideration. By all means experiment with your own fit position. Mountain bikers are often self reliant do-it-yourself types. I’m one of them. I’d rather work on my own bike than take it to a shop, but when I can’t figure something out or fix it myself, I’ll take it to a shop. Next month – some “how to’s” on figuring it out for yourself.

Oh my aching butt…

This has been a common theme for people coming in for bike fits so far this year.  Well, maybe most years.  Humans weren’t designed to sit on bike saddles, so it’s no surprise this direct contact point with the bike can be problematic and difficult to solve.

There are a few causal categories:

Clothing: no chamois, wrong chamois shape or padding, not using chamois cream, wearing undies under bike shorts.

Activity Level: suddenly increasing ride duration or frequency.  If you are used to riding a a couple of days a week, and then bang out 2 or 3 days in a row, that can hurt, but it should be temporary.

Body Asymmetry: lateral pelvic tilt, pelvic rotation, leg length difference, riding posture, all affect weight distribution.

Saddle Type: and how well it supports your anatomy.  The two main variables are width and shape (or profile).  A saddle needs to be wide enough to support your sit bones, but the right width and wrong shape wont be comfortable.  I commonly see saddles that are too narrow to offer optimal pelvic support, but that is only part of the issue.  It’s not only the width at the rear, but the width of the nose that can be an issue. The profile from the back can be flat, semi-round or rounded.  The profile from the side can be flat, hammock, or curved.  Center cutout, or not. Then there is padding: none, a little or a lot.  More padding can mean more problems.
An old saddle may be broken down, or actually broken – which I saw a few weeks ago.

Saddle position: height, setback, tilt and rotation all affect your posture and comfort.

Identifying the culprit is key to coming up with a solution, and the solution usually involves some experimentation.  If you are still tender when trying out a different position or saddle, you are not going to know right away if that works for you or not. But it shouldn’t take months or years either.  Your body will let you know what’s good, usually through an absence of discomfort.  i.e the saddle should disappear from under you.

If this is a topic of interest there is a more indepth article here, which draws a lot on research done by Trek Bicycles. Thanks to a client for bringing this article to my attention.

For an even better article that focuses specifically on female anatomy and saddle contact discomfort for woman, and covers far more than my blog post, this is blog by Lovely Bike, and reader replies and comments is the most informative you will come across. Here. Thanks to Lovely Bicycle!

Don’t let a sore butt keep you off your bike.  If pain persists, see your bike fitter!

Size Matters

The following article was written for, and published in Cycling Utah and Cycling West in the March 2016 issue.

Spring is in the air, the sun is warming your back, and you’ve got the hots for a new bike. It won’t have the smell of a new car, but it will have the feel of speed, joy and freedom.  That’s assuming it is adjusted to fit you, and fitting starts with sizing.  Which is why size matters.

A bike of the correct size offers a “fit window” to allow for adjustments to the saddle and handlebar position to suit your body and riding needs.  If the bike is too big or too small for you, then it’s going to be a stretch (or a shrink) to get it close, and close will not be good enough for all day riding comfort.

Frame Size is a one dimensional measure of the height of the bike, as an actual or theoretical seat tube length.  It may be expressed in inches or centimeters, or as a small, medium, large, etc. There is not a consistent agreed way to express a bike size, and so the same frame label size between different brands can vary significantly.

While size matters, you should also know that Shape does too. Two bikes labelled with the same frame size may be a very different shape, and therefore feel quite different. Frame Size does not take into account the length of the bike or the height of the front end, both influencing where the handlebars can be. These are important because they affect your reach and drop from the seat to the handlebars which determines your upper body position, which influences your back, neck and hand comfort. Seat tube angle is also an aspect of shape that influences where your center of mass and balance can be located.

Shape is two dimensframe geometryional, and is defined in the frame geometry charts for each model, which show lengths and angles. Shape can be expressed descriptively.  For example as race, competition, sports, or endurance for road bikes and as XC race, trail, all mountain or freeride for mountain bikes.

Shape can also be described as frame “stack and reach” co-ordinates, which defines where the head tube is in relation to the bottom bracket. These are useful numbers for comparative purposes.

Shopping for Size

When going into a store to buy a bike, you now know it is important to get the right size and shape. How is this determined? You can measure the geometry of an existing bike you ride that feels good for you, and use those specs. But if you don’t have an existing bike, or if it is not a good template, then it’s in the interest of the bike shop to help you out. There are 4 main sizing methods:

The eyeball. This is when the sales person runs their eye up and down you, and pronounces a number with confidence. It’s good for their ego, but not necessarily a quantifiable, evidence based approach.  Move on….

Stand over clearance. This is useful, as no one wants to knack themselves straddling a bike, but it only takes into account one aspect of sizing, and ignores the rest. Move on….

Body measurements. Hard data like inseam length, height, torso length or sternal notch height, arm length. Now we are getting some evidence of skeletal proportions which are very useful for accurately recommending a bike size and shape, in conjunction with information about riding style and intentions, and physical factors like strength, flexibility and injury history. Be mindful that inseam length on its own is only a predictor of bike size and not bike shape. Two people with the same inseam length but different upper body portions may well be better off on different bikes. There are a number of body measurement systems available to bike stores, including the Fit Kit System which has been in use for over 30 years. This sizing is usually free if you are buying a bike at the store.

Pre purchase fitting. This top shelf option has you riding on a size cycle (bike simulator) to determine a final fit position, and from this a recommendation of suitable bikes and components can be determined. This will typically have a cost because of the time and technology involved. The Guru Fit System is one such option, with integrated frame finder software, but there are a range of low tech to high tech size cycles around.

Buying Online or Used

If you are buying online, some websites offer a sizing guideline. These vary widely from totally useless to quite thorough. You can also go into a local bike shop that uses a sizing system, but convey your honest intentions of shopping online, and expect to pay for the sizing service. This also applies if you are buying a used bicycle, which is by far the easiest way to get a bike that will not fit. A great deal off KSL doesn’t make for a great ride if the bike is the wrong size. Measure twice, buy once. Size matters. So does shape.