Bike Fitting is an Art, Not a Science

What counts in sizing and fitting a bike are the points where the bike intersects with the body. The relationships between the saddle contact point, pedals, and the handlebar grip area, determine the riding position. These relationships can be affected by a number of factors including frame size, saddle adjustment, crank length, stem size and adjustment, and handlebar design.

I’ve learned through many years of riding that, for me, the most important factor in bike fit is handlebar height in relation to saddle height (after setting saddle height, of course). I prefer the primary grip area of the handlebar to be 1cm-2cm above the top of the saddle, when the saddle is adjusted to the proper height (more on saddle adjustment here). Too low and there’s too much weight on my arms, too high and there’s too much weight on the saddle. This is a personal preference based upon how I ride, and others will certainly come to different conclusions based upon their physique and riding style.

What I find less important is the length of the cockpit, or in other words, the horizontal distance from the saddle to the handlebar. If the saddle to handlebar height relationship is correct, I feel equally comfortable on bikes of different lengths (within a reasonable range). Consider the photo above. The Surly LHT is a 56cm frame and the Rivendell Sam Hillborne is a 60cm frame. As you can see, the Rivendell is longer, but because the bars are at my favored 1cm-2cm above the saddle, I still find it comfortable. In fact, these two bikes both fit me quite well for how I use them. The Surly is a city bike for hauling weight in traffic, and its shorter front is good for that type of riding. The Rivendell, on the other hand, has a more open cockpit and the stretched out position is better for longer rides on open roads.

Where it gets tricky is when you start looking at different handlebars, stems, and top tube angles. When I purchased my Rivendell, I knew from the start that I wanted to spec the bike with Moustache handlebars. These bars have much less rise (they actually drop a bit) than the North Road bars on the Surly. To get the grip area at 1cm-2cm above the saddle, I knew I had to either use a stem with an extreme amount of rise or choose a larger frame to bring the front end of the bike higher. Since I didn’t want an exorbitant amount of stem showing above the headset, and I also wanted a more open cockpit than on the city bike, I went with the larger frame. On the other hand, if I had planned on speccing Albatross or North Road bars, I would have gone with a smaller frame size because of the handlebar’s greater rise.

Some modern sizing methods use upper body measurements and top tube length to determine frame size. While this may work for some people (but usually only if they’re speccing drop bars), it invariably places me on a bike that is too small. One of my bikes is a 54cm and it was sized using the top tube method. I’ve never been able to get the handlebars at my preferred height in relation to the saddle on that bike. The bars are too low and the cockpit is cramped, even though according to a popular “scientific” sizing method, this is the correct frame size.

All of this is a long-winded way of saying bike sizing is complex and I don’t believe it can be boiled down to a codified method. The photo above demonstrates that with careful component choices it’s possible to achieve similar riding positions on bikes of widely differing sizes. The number of variables in the process, including the intended use of the bike, frame geometry, saddle set-back, and handlebar/stem choice, make the process more an art than a science. Seeking out a knowledgeable salesperson or builder who has experience with transportation bikes, clearly understanding and stating your personal preferences, and remaining flexible in your assumptions, is much more likely to land you a properly sized bike than any mathematical formula.

30 Responses to “Bike Fitting is an Art, Not a Science”

  • Logan says:

    Great topic Alan!

    Bike sizing is indeed a difficult task. Tammy and I have come to a similar conclusion that regardless of the bike size as long as you feel comfortable on the bike that is what is important. Tammy’s LHT always looks too small for her but she assures me she is very comfortable. After reading your article I realized that I set up her bike with a slight rise in the handlebars over the saddle. That must be the key. :) Thanks for your insight!

    Jan Hiene in the new BQ has an article on how ride stability can be a factor of wheel size and tire width. I think alot of “comfort” on the bike has to do with how stable the ride feels as well. Very interesting stuff.

    On a side note I think you would be happy to hear that nearly all the bikes displayed at the pedal nation event here in Portland had a similar setups to what you described above. The majority of vendors and builders were promoting comfort, utility/cargo applications and family focused cycling. :)

    Cheers,

  • Doug R. says:

    Alan, great piece. I have (as you know )many life long injuries which make me setup a bike with great care so I can operate it with comfort and avoid pain and numbness. I always go for the adjustable stems. I know many people don’t prefer them because they can come loose or “Rattle”, however, I have found a good brand which works very well for me, Kalloy a maker of both 1 1/8 mtb and old school 1″ etc. quills. I like the build quality and clean design. Dougman

  • Joe says:

    Great write up alan!! As always, great info and easy to understand terms. Bravo

  • Eric Owsley says:

    There’s probably a post answering this already on the blog, but Alan’s comment about cockpit length not being much of a factor got me thinking about the effect of stem length on steering feel. My old Raleigh has virtually no forward travel on the stem, and I love the way it tracks and settles into corners. My other bike has a similar set up — North Road bar, same saddle height, but shorter top tube and longer reach stem — and the steering feels much quicker, even twitchier. Can anyone offer my an explanation of these differing feels?

  • Alan says:

    @Logan

    “Jan Hiene in the new BQ has an article on how ride stability can be a factor of wheel size and tire width. I think alot of “comfort” on the bike has to do with how stable the ride feels as well. Very interesting stuff.”

    Definitely. And tire diameter and flotation can significantly contribute to shock absorption, another important aspect of ride “comfort”.

    “On a side note I think you would be happy to hear that nearly all the bikes displayed at the pedal nation event here in Portland had a similar setups to what you described above. The majority of vendors and builders were promoting comfort, utility/cargo applications and family focused cycling. :)”

    That’s great to hear, Logan!

    As an aside…

    I know this is a topic you’re interested in… Did you notice the headtube angles and fork offsets in the above photo montage? It clearly shows the LHT’s higher trail front end in comparison to the Hillborne’s more moderate trail. I thought it was cool to see the two in direct contrast like that and thought you’d find it interesting.

    Alan

  • Alan says:

    Hey Eric,

    In comparing the difference in handling between your two bikes, there’s very likely more at play than just the stem length. Head angle, trail, weight bias, wheel diameter, and even tire diameter and wheel weight have an affect on how a bike steers. While stem length certainly plays a role, you’d have to look at all the factors together to get an idea about what’s happening. My guess is that the head angle on your old Raleigh is more relaxed, it probably has a much further rearward weight bias, the front end probably has higher trail, and I’m guessing the wheels are heavier.

    Here’s a pretty good introductory article on bicycle geometry at Wikipedia:

    http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry

    Alan

  • keith says:

    Another great post Alan. I sent a comment a few weeks ago asking you about these very bikes and the different sizes, so thanks for revisiting the topic once again. Now if you ever want to write about trail, I’d love to read it.
    Keith

  • Joe says:

    I second Keiths request

  • AndyN says:

    The photo above, with the longer Riv superimposed over the shorter LHT reminds me of an experience we had. My wife is 5’2″ (158cm) and we had a devil of a time finding her a bike that fit properly. As an adult returning to cycling for the first time since childhood, she hadn’t grown accustomed to the ill-fitting “small” frame sizes that I see many other shorter riders struggling with. Eventually, we found a perfect solution in a Novara “children’s” road bike. The interesting thing was comparing the so-called kids bike to the smallest adult commuter bike on the floor at REI. They both had 26″ wheels, and the saddles and bars were in roughly the same places. The difference was the 2″ shorter wheelbase on the kids bike. The shorter wheelbase made all the difference in terms of bike feel, and in bike fun. Her prior bike, a Craigslist Special, was an X-small frame size, but rode like a oil-tanker because it was too long. She never enjoyed riding it, and frankly didn’t see the economic rationale for buying a a different bike. I think she mostly was humoring me, her bike-nut husband. Finding the bike that actually fit was a revelation – we had been doing short Sunday rides in the park; now she’s become a full-time bike commuter. The experience really opened my eyes to how poorly the bike industry serves the customers who fall outside the 5″9″ to 6′ 2″ male demographic. I imagine that to her, *every* bike felt like I feel on my ’41 Schwinn cruiser – big and slow. Imagine a Schwinn cruiser with drop bars … no wonder she wasn’t having fun.

    Hey Bike Industry! There’s nothing particularly unusual about a 5′ 2″ adult. Why aren’t you making bikes that truly fit those customers? I’m not talking mere standover clearance, I’m talking about that ineffable joy of a machine that whispers to you as you ride.. “Go Faster… Go Farther…. Go… Go! Go!”

  • Jim says:

    Bike fit starts with your butt in relationship to the bb. Where you like to put your hands follows. All kinds of geo’s can work for a rider of a given morphology. BTW the superimposed picture would be more correct if the bb were lined up, given this starting point. Getting bogged down in individual metrics obscures how a bike rides. All the numbers together go to the ride.

  • Logan says:

    @Alan,

    Thanks for pointing that out. This Venn diagram approach is a great way to see differences in bike frames! Fantastic idea! :)

  • Steve C says:

    the “whole package” fit approach, rather than just the frame size is definitely the way to go, I’m very comfortable on my Diamondback based home built hybrid.

    I tried some Origin 8 spacebars to get a more favourable angle for the poor old wrists, but they put my hands too close to my knees for comfort and I was already using a 120mm stem, so it’s probably best to start with the seat, feet and hands and work back from there through some preferred component options and them to the frame dimensions and angles

  • Saddle Up says:

    For someone as experienced as you Alan bike fit may indeed be more art than science. For someone relatively new to cycling and without a vast cycling history I believe that they in fact will benefit more from the science of bike fit. Bikes like the Rivendell have their own unique fit methology, as do bikes equipped with handlebars that position the rider in a more upright position

    The relationship between your backside, your knees and your feet is where science comes into play. The art of bike fit is in the relationship between the saddle and the handlebar positions. This is where science and art of bike fit truly interesect. Having a fitter with experience and skill is what brings the science and the art of bike fit together.

    My contribution to aid riders in getting the most from their bicycle through proper fitting.
    http://saddleupbike.blogspot.com/2010/04/mobile-bike-fit-studio-and-labratory.html

  • Alan says:

    @Saddle Up

    Very interesting! Thanks for the link.

    Regards,
    Alan

  • Rick says:

    @SaddleUp:

    “Having a fitter with experience and skill is what brings the science and the art of bike fit together.” Bulls-eye!

    That’s exactly my problem with both bike shop salesmen and restaurant servers: too little training to help the customer properly, and too much, “hey, just sell what we got”, regardless if it’s not what customers want or need.

    A case it point: last Friday, as I was riding to our local train station to meet my wife, I passed both a bike shop (not local, but a chain from the Bay Area) and, outside, a young woman struggling to ride a bike. “Too big!” I said as I passed by; as I was about to go on my way, she said, “Really? Why?” Obviously, having opened my big mouth, I needed to finish what I started, and was happy that I left a few minutes early for the train. I went inside with her.

    I looked the bike more closely: a Specialized Globe Caramel 700, size small, and had been adjusted for her by someone by bringing the seat post down as far as it would go. I asked how tall she was, and she replied, “5-1″ “Ah, I see”, I said. We went inside and found the young man who had helped her. He possessed the enthusiasm and helpful earnestness that you find in abundance these days with youthful service types (I’m sure most of them state, “I’m a people person!” on their resumes.) The problem, of course, is they don’t actually know anything about the product they’re selling.

    “Can I help you, sir?” he asked, all cheekbones and teeth. I replied that I was just passing by, and had noticed that the bike might be a touch too small for the lady. He looked at me once again with all the earnestness he could muster, and relied: “But that’s what we have in a small size!” Ah, I see: small person=small bike. I asked if they had the regular Caramel bike–the one with 26″ wheels–and was told no. I asked if they had any bikes in an XS size, and was told no. I asked if he understood how the small size was probably for someone three inches taller, and was told no. I asked if he understood (out of earshot of the young woman-I had no interest in embarrassing him), that sending a person out of his shop in an ill-fitting bike would probably ruin the experience of ownership for the rider, and especially so for a first-time one? His reply was perfect: “But I thought it fit her”. Yep, well, ok, thanks, and you have a nice day, too, my young friend.

    I informed her that if the shop didn’t have a bike that fit her properly, then in was best that she kept looking. She left without the bike, and went to another one that I knew would fit her correctly. Happy ending, right? I hope so, but you get my drift: what if I hadn’t passed by?

    So if there is any bike shop owners that read this, please train your people correctly–your employees have so much more power than they realize. Restauranteurs? I’ll get to you later! :-)

  • Don says:

    Bike fit is as important to the casual rider as it is to the commutor or the competitor. It is probably the primary predictor of whether someone will stay with it or not.

    I am continually amazed by how the tiniest changes can make a world of difference, and by the uniqueness of each person’s body. A lot is said about proportions and relative lengths of different parts of the body in relation to riding, but just as important is weight distribution and weight density. People often choose bikes based on aesthetics or perceived lifestyle, which can be like choosing an outfit or haircut without regard for one’s physique. I love that a bicycle can be an indirect portrait of a person’s body.

    Getting that balance point right is like feeling a golf or tennis swing when it’s right: it can be a challenge to get to that point, but once experienced, there’s no turning back.

  • David says:

    @Steve C
    I’m riding an old DB Overdrive Comp, it makes a great commuter. What’s you’re project?

  • Tim D. says:

    Handlebars and their position can definitely make a big difference. I recently put moustache bars on my commuter/camping bike, and just did a 70 mile camping trip this weekend. This particular bike is a bit bigger than my other bikes, but not out of my size range, and the moustache bars instead of drops made it feel like a whole different bike.

  • Eric says:

    Nice comparison Alan, thanks. I’d love to see the same photo comparison done with a rider on the bikes….

  • Steve C says:

    Dave,

    it’s a Zetec comp frame with Kona project 2 rigid disc brake forks, Hope mini disc brakes and self made 700c wheels

    the bike was assembled from parts obtained from trade-me, the local online auction site, the next upgrade is road triple chainrings because the MTB gearing tends to max out on the road!

  • Charlie says:

    Alan, Nice post– you nailed all the key issues. Except one: recommending relying on bike-shop advice too much. Rick’s story (which happens thousands of times a day) shows why.

    My recommendation: Get any old bike set up with an adjustable quill stem–adjustable in height and reach. Play with the positions of the seat (vertical and horizontal) and the bars (again, vertical and horizontal) until you like the result. *Then* when you shop for a bike, make sure it can be adjusted to match that setup.

  • David says:

    @Steve C,

    Nice setup. Mine’s not too different from where you’re headed, though in steel rather than aluminum, and your brakes are a big upgrade from my Dia Comp calipers. I’m running 700C x 32 wheels with the original Suntour XC Pro microdrive triple cranks and 11/24 rear cassette. I find that I keep it almost exclusively on the 42 front chainring but I have a very consistent commute and the 9 speeds in the rear cover my necessary range almost perfectly (though with a few wide jumps in the middle.) That said, it’s nice to be able to drop down to the two smaller front rings when I want to go exploring in hilly Seattle and don’t know what I might run into.

    @Alan
    Sorry for the your/you’re transposition above. As an amateur text editor, I was horrified to see that after I hit “submit”. You really need an “edit” function. Barring that, in the future during moderation, feel free to clean up any headslappers I may make!

  • AndyN says:

    @Rick –

    Good on ya for offering unbiased assistance! IMO, the Novara Pulse is a must-try for the shorter adult women, even if it’s displayed with the kids’ bikes. Or, as when my wife found hers, when mounted on top of the car roof-rack display, requiring two REI employees to fetch down for a test ride.

  • Peter Stewart says:

    The setup is more like art, but art is always preceded by years of dedication and learning, which boils down to the “science” part.

    To quote a movie (don’t know which one): “You need to learn it all, and then forget it all”.

    I cannot tell you how frustrating it was looking for some solid answers to setting up my bike correctly from information on the Internet. Just too many claims of “it needs to feel right”, which is really stating the obvious.

    We take for granted how much knowledge actually goes into the decisions we make on bike setup. Those unconscious decisions are a result of all the knowledge we’ve built up over the years.

    So, for me the following helped me to get the best out of my current ride without investing in any new hardware:

    1. Saddle height
    2. Saddle fore/aft
    3. Handlebar height
    4. Distance from seat to handlebar (requires hardware change, not changed yet)

    I have yet to get my head around all the other measurements like wheelbase and all that jazz. I’m sure frame builders and bike builders know these measurements and their effects on the overall riding. I’d love to find an article that summarizes all that into a nice clear package like…

    Longer wheelbase makes the bike feel more…
    Shorter chainstays make the ride more…
    etc, etc

    Until such a time, just keep being creative.

  • edde says:

    So you guys never fitted a recumbent or crank forward? (I know Alan has.) Pretty much tosses the “science & art” of bike fit on its head, except seat height/x-seam length.

    I ride, among other bikes, a locally crafted cromo crank forward with standard bike saddle which defies “plumb line from knee to crank end” rule with no apparent ill effect. The bike is more comfy than typical uprights, easy to get a foot down without getting out of saddle while retaining proper leg length, puts less stress on neck, hands, wrists & arms, has long enough wheel base to ease bumps, is near impossible to do a header and is still sufficiently agile handler to off road occasionally. To be sure, I fiddle with stem & handlebars and found set-ups that work great for me and other CF riders.

    Whatever, yall have FUN, Ride your bike;-)

    edde

  • Alan says:

    @edde

    Yeah, I fit a few recumbents… :-)

    In general, I found fitting recumbents much easier than fitting diamond frames. The fact that most come equipped with widely adjustable seats (not saddles) and adjustable stems makes the process relatively simple. Also, recumbent designs aren’t typically fettered with the limitations of standover height and limited stem rise that are inherent in most uprights (other than step-throughs and mixtes).

    Regarding the plumb-line from knee to crank fitting technique, I think that’s pretty well been de-bunked as a legitimate part of the bike fitting process (bracing for the incoming on that comment… LOL).

    http://www.sheldonbrown.com/kops.html

    Alan

  • rod says:

    Hi Alan,

    Thank you as always for these thoughtful and interesting posts. This one in particular seems quite timely. I’m 6’2″ with a PBH of 90cm and am riding a 56cm LHT. While I feel the TT length is close enough for rock n’roll I know that the vertical height or amount of seatpost showing is pretty dramatic. I would prefer to have more of the Rivendell style fitting with handlebars above saddle but there is no way I will ever accomplish that on this 56cm frame.

    I have a question about the Sam Hillborne and the Handsome Devil as potential spirited road riding bikes for longer rides. With the intent of getting a bike for club rides/centuries and just good old long rides for the fun of it. Since you have had access to all these bikes I thought I’d tap on your experience to get your take on the ride characteristics, weight of the bikes and general impressions.

    Thanks.

  • Alan says:

    Hi Rod,

    Sorry to hear you ended up with a too small bike. At your PBH you could easily be on a 58 or 60.

    It would take a full article to really get into comparing these three bikes in detail, but here are a few quick thoughts.

    The Rivendell is the most refined of the three. It’s lighter, livelier, and prettier than the others, but at its higher price point that’s expected.

    The LHT and Devil are priced about the same. You’re familiar with the LHT, so I’d suggest taking a look at my review of the Devil and comparing notes with the ride quality of your bike:

    http://www.ecovelo.info/2010/02/16/handsome-cycle-co-devil-2/

    The most striking difference between these two bikes is that the LHT handles best when rear-loaded, while the Devil handles reasonably well with some weight over the front wheel. The geometry chart in the review might provide a little insight.

    Alan

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