BIKE FIT

Last Updated: 9/19/2010

UNDER CONSTRUCTION


OVERVIEW

Bike fitting is endlessly discussed among cyclists and for good reason. It can really make or break your cycling experience. I cannot add much of value to the volumes that have been written on the subject. Still, I can mention 4 points that have been helpful to me:
  1. Understand that there are very different styles of fit, each suited for different purposes and riding styles.
  2. Use a well tested formula-based system to determine your frame size according to a variety of measurements of your body.
  3. Customize your fit by swapping out components. This is a life long process.
  4. Seek expert fitting advice from a local bike shop, but take it with a grain of salt.

MENU


THE 3 STYLES OF BIKE FIT

Bike fit is all about putting the saddle and handlebars in a position that will best allow the rider to reach their goals. For the most part, saddle height is easy to get close as a function of leg length. The position of handlebars is more controversial.

Here's my bottom line... Most reasonably healthy people riding a performance bike but who are not racing competitvely will do well with bike that is sized so that their handlebars can be set between 0" and 1" below their saddle.

Obviously, that statement is a bit simplistic. It is more correct to say that different riding styles demand different kinds of fit. The best advice on this subject that I've seen is the essay "The Traditions of Road Riding and Our Three Styles of Fit" at the Competitive Cyclist website. They describe 3 fitting styles which can roughly be categorized by the height of the handlebars relative to saddle. The first is the Competitive Fit which puts the bars 3" or more below the saddle. This style should be reserved for professional racers or the most devoted of citizen racers who put the highest priority on aerodynamics. However, don't assume this is the best position for serious racers.

They call the second fit style the Merckx fit after the famous Belgian racer. This puts the bars 1" to 2" below the saddle. Before you dismiss this fit style as somehow less efficient than the Competitive Fit, you should know that some believe that this type of fit is ultimately more efficient since it puts the rider in a more comfortable position where he or she can breath better. These somebodies include Eddy Merckx and Lance Armstrong. According to one article, Lance arrived at this more moderate body position after extensive wind tunnel and power testing. The conclusion was that any aerodynamic benefits of the low bar style were undercut by decreases in the ability to breath, and with that, a decrease in power output.

The final fit style is called the French style in reference to the classic french style touring bikes. This style puts the bars at about saddle height and is generally associated with long distance riding. It is common for cyclists to migrate to this fitting style as they age. But, I would caution against dismissing this as the style for older riders only. If your goals are long distance cycling such as touring, brevets, centuries and other "event" rides, then this fit style should be considered closely.

My only strong opinion on these styles is that the low bar competitive fit should be avoided by pretty much everybody - or at least by anybody who will be reading this web page seeking fit advice (as opposed to a racing oriented site). Some young racers will always choose to punish themselves, but the rest of us mortals should probably have our bars 0" to 1" below the saddle. I flatly reject the argument that if the competitive fit works for pro cyclists on long road races, then it should work for us. Firstly, few recreational cyclists have the time to put in the amount of training needed to force your neck and shoulders to take that position and fewer still have the pain tolerance of pro racers. Secondly, there is good evidence to suggest that it's a misguided approach to gaining efficiency. My advice is to honestly assess your riding style and then choose between a Merckx or French style of fit.

Return to Top


FORMULA BASED FRAME PURCHASING

After you've decided on a fit style the next most important decision is to buy a frame that allows you to achieve that fit. Here's my suggested bottom line approach, assuming a goal of getting your bars 0" to 1" below saddle height:

Measure your inseam (a.k.a. pubic bone height) and then use the Peterson and LeMond formulas to calculate your frame size. Here's how to do it...

Stand in your bare feet with your back against a wall, feet comfortably apart. Place the spine of a large coffee table book against the wall between your legs and slide it up along the wall until it is firmly against bone. Have a friend run a tape measure from the floor to the top of the book. This is your inseam, or pubic bone height.

The LeMond formula for frame size is inseam x 0.67. The Peterson/Rivendell formula for frame size is inseam -15cm. In general, Peterson/Rivendell formula will give you a slightly larger frame size. Also note that the LeMond formula is typically adjusted upwards for riders above 6' tall. Here is a simple size chart in text format that gives both the LeMond and Peterson/Rivendell frame sizes, along with the recommended saddle heights.

For example, I'm pretty tall and have an inseam of 92cm. The LeMond size range for me is between 62cm and 65cm and the Peterson/Rivendell range is 63cm to 65cm. For the record, I started riding 64cm frames in 1977, rode a 62cm for about 10 years in the 90s and have been back on 64cm frames for the last 10 years. I could never really get comfortable on the smaller size and have come to trust these charts. For a normal, bars near saddle height fit, I suggest erring on the large size of the suggested ranges. If you find this overly simplistic, or if you want more detailed formula-driven guidance on other aspects of bike fit, I would suggest using the Fit Calculator at the Competitive Cyclist website.

Now that we've discussed how to find your bike size, we should talk a bit about what size actually means. Traditionally, the "size" of a bike has been the length of the seat tube, as measured from the center of the crank to the point where the seat post comes out of the frame. This is complicated a bit now that top tubes are no longer flat. So, for comparisons sake, many manufacturers will publish the "effective seat tube" or "size" based on the imaginary lines that would be formed if the top tube where level.

A word of warning... I think frame size discussions can get more complicated when dealing with some modern road racing bikes that are designed specifically for a low-bar type of fit. But this is of no matter, really, if you avoid such bikes. As a rule, I suggest that the bike should permit the bars to be set at a position that is level with the saddle. This is particularly true for modern bikes that use "threadless" headsets, as this style of headset dramatically limits the range of adjustability for handlebar height.

Return to Top


ADJUSTING FIT WITH COMPONENTS

Even assuming that your frame is a reasonably good fit for your body and riding style, you should be prepared to adjust and fine tune that fit by adjusting or replacing components on the bike. My intention here is only to identify those components you may need to adjust or replace. It is not to describe how to make those adjustments. I will leave that job to others.

There are countless articles on how adjust and fine tune your fit available on the internet. By far, one of the best articles I've read on adjusting your fit is by Peter White at his website. The thing I appreciate most about Peter White's approach is he recognizes how fit is affected by things such as the rider's style, preference and age.

The components that have an affect on fit include the seat post, the handlebar stem, the handlebars and the crankset. The most first and most obvious adjustment to be made is the height of the saddle, which is adjusted by the seat post. However, just as important is the fore/aft position of the saddle on the seat post. The position of your hips relative to the center of your cranks forms the foundation of your bike fit, so together, these 2 adjustment are absolutely critical. In nearly all cases, the seat post that comes with your bike will provide you with the range you need to get a proper fit. Typically the only reason people replace their seat posts is to achieve some fashion oriented goal such as weight reduction or looks. However, occasionally a person needs to move their saddle more foreword or, more typically, more rearward than their stock seat post will allow. To achieve this, you can use special "set-back" seat posts.

Not long after the saddle height has been set with the seat post, many cyclists conclude that the stock saddle that came with the bike needs to be replaced. For most long distance cyclists, this is a correct conclusion. Most modern saddles consist of plastic shells that are covered with some sort of foam material and then wrapped in leather or some synthetic material. Another style that has re-emerged is the unpadded shell. I first saw (and used) unpadded plastic shell saddles in the 1970s and today they've reappeared made from super light carbon fiber. Lastly, and in my opinion most importantly, there is the leather saddle; namely the Brooks line of saddles. While I'm generally trying to steer clear of offering specific fit and comfort advice on this page, I will say that the Brooks B-17 has been, far and away, the most comfortable saddle I've ever used. But saddles, like ski boots, are a very personal issue. Different back sides demand different saddles. As a rule, the wider your sit bones are from each other, the wider saddle you'll need. Related, the higher your cadence is (the rate at which you spin the pedals), the narrower saddle you'll prefer.

Another of the most frequently changed piece is, or should be, the handlebar stem, which adjusts both your reach to the bars and the height of your bars. The height of the bars relative to your saddle height should be determined by your riding style (not by the well meaning suggestions of racer wanna-bes). The standard rule of thumb for determining the reach from your saddle to the bars is is that this distance should equal the distance from your elbow to the tip of your middle finger, which is a very easy test to perform. That said, finding the best reach and handlebar height can be a life-long quest. For this reason, it is not uncommon for experienced cyclists to end up with a small collection of stems in their parts bin. Worse, this can change over time. The more you ride, the more your neck and shoulder can accommodate lower bars but the more you age, the more you will like your bars up higher. Some better bike shops even have adjustable stems that they can loan to customers so they can try various combinations before buying. If your shop offers this service, take advantage of it.

The handlebar is another commonly replaced part. Bars can vary in terms of their width and in the distance from the top of the bars to the bottom of the drops. And, there is a nearly infinite number of variations in the different curves and shapes that are available. Each bar style has its devoted fans and its not uncommon for cyclists to try many different styles before finding comfort. Generally speaking, bar width is related to the rider's shoulder width, but there is plenty of room for variations here.

The last component that can be adjusted to affect fit is the crank set. The length of the crank is the most commonly discussed variation. One school of thought says that crank length should vary based on femur length and concludes that tall riders should be on very long cranks and short riders on short cranks. Another school of thought is that crank length should be adjusted according to riding style. According to this line of thinking, low cadence power riders should use longer cranks and high cadence spinners should use shorter cranks. And yet another school of though says that for many decades everybody rode on 170mm cranks and got along OK. Each of these perspectives has a kernel of truth in them.

The other aspect in which cranks can vary is called the tread, which is the width of the cranks measured from the outside face to outside face at the pedal threads. In some circles, this is called the Q-factor, or quack-factor, as in how much the crank makes you ride like a duck. Some folks argue that narrower is better. Others suggest that the tread should match your hip width. And others suggest that the angle created by your knees should dictate the ideal tread for the rider. Most agree that tread can have an affect on knee pain. Whether you're concerned about crank length or the tread, I think the reality is that most folks just ride with the stock crank that came on their bike. Quality cranks are expensive items to replace.

Return to Top


SEEK LOCAL EXPERT ADVICE

Whitehead once advised, "Seek simplicity, but fear it." This leads me to my final piece of advice on bike fit. Seek expert fit advice, but be suspicious of it. Most bikes ship with parts on them that will fit most people and a good number of bike shops are happy to sell you a bike and send you on the way with no fitting help beyond raising or lowering the saddle. And since most fit problems take many miles to make themselves known, this approach often works, at least for the shop.

So, if you are having fit problems, seek out a local bike shop that offers a fitting service and that has a good reputation in this regard. If the shop has dedicated valuable floor space to create a fitting area, this is a positive sign that they at least want to appear to take fit seriously.

But be aware. Many so-called fit experts either are or were racers and the siren song of a low-bar "competitive fit" may still have a strong influence on them. Worse, you could end up with somebody with little fitting experience beyond running numbers through a formula based system and reading too many racing magazines.

You should expect to pay 1-3 hour's labor rate for a good fitting service. In return, you should demand the fitter help you achieve your fitting goals. Don't hesitate to print off and bring in the Competitive Cyclist essay on fitting styles and be sure to work out a common understanding of your goals. If the fitter puts your bars 2" below the saddle and suggests that you'll get used to it, ask for your money back and seek advice elsewhere.

Return to Top


Dave's Backcountry Skiing Page
Dave's Cycling Page

Copyright 2006 by David Mann