Numbers Don’t Always Tell the Story

This is me on my 60cm Rivendell Sam Hillborne. This is a comfortable fit. I think just about anyone, even those without a trained eye, can see that I’m in a relaxed, natural position. The position places just enough weight forward on the bars that I don’t feel planted on the saddle, but I can ride for hours with no wrist or neck pain.

The frame was sized using a “traditional” method. Essentially, it’s the largest frame I can ride in this model while still having just enough standover clearance. On paper, the 620mm effective top tube should be way too long for my build — I have long legs and a relatively short torso — but in practice it’s a good fit (compare this to my 56cm LHT’s 570mm top tube).

The $64 question is, “How is this possible?” I believe it’s a combination of this bike’s relatively shallow seat tube angle, upsloping top tube, and quill stem, as follows:

  • On bikes with steep seat tube angles, many people jam their saddles all the way back, or even go as far as purchasing seat posts with extra set-back to place the saddle further behind the bottom bracket. Doing this has the effect of lengthening the top tube and slackening the seat tube angle.
  • An upsloping top tube raises the front of the bike, making it easier to place the grip area of the handlebars at or above the height of the saddle.
  • The height of a quill stem is easily adjusted, again, making it easier to place the grip area of the handlebars at or above the height of the saddle. Higher bars essentially nullify the greater reach of a longer top tube on a larger frame.

A bike may have a longer effective top tube length on paper, but depending upon how it’s set-up, the physical reach to the bars may be the same (or even shorter) as on a bike with a shorter top tube that’s set-up differently. In the case of my bike shown above, the 71.5 degree seat tube angle, short reach quill stem, and Moustahce handlebars make for a fit that works well for me, even with what looks like a too-long top tube on paper. To get the same fit on a smaller frame would require a longer reach stem and more stem extension above the headset. The bike would be insignificantly lighter, the steering would be affected because more of the rider’s weight would be on the front wheel (whether this is better or worse is subjective), and in my opinion, the bike would be less aesthetically appealing because more seast post and stem would be showing.

Even though I happen to be a proponent of traditional sizing methods, none of the above is to promote any one particular approach to sizing and fit. The important thing is to remember that it’s a subtle combination of frame size, frame geometry, and component selection that results in a particular rider position, and that more often than not, the numbers on a geometry spreadsheet don’t tell the whole story.

21 Responses to “Numbers Don’t Always Tell the Story”

  • ghd says:

    I’ve been debating between the 56 and the 60 Hillborne, as I seem to be right in between the two. What is your PBH and how tall are you? The 60 I rode “felt” a little big, but it also had a stem with a bit of a long reach, and I wonder if a shorter-reach stem may just do the trick. It’s a great bike!

  • Jeff I says:

    Alan, great article. Seat tube angle is one of the most under-appreciated aspects of bike geometry/fit and you perfectly captured the nuance of it.

    I did have a question about your 1×9 conversion on your Surly LHT because I am thinking of doing the same for my Trek 520. What sized BB did you use for your Sugino crankset? I’m concerned that a 103mm spindle won’t be able to clear my chainstays. Your feedback would be greatly appreciated.

    Jeff

  • sophie says:

    I have been searching for the right bike for me for almost my whole adult life. When I was a kid, bikes I owned would fit me just fine. Then I grew older but stayed quite short (5’2″) and suddenly bikes would be a nightmare.
    I mean, basically all my bikes tore apart my upper back muscles and I would catch a headache in no time.

    I came to think of getting myself a custom bike (not a custom frame though, it will be my next project). The only two things I was concerned about were to reduce the top tube and seat tube length.
    And so I looked up the internet and ended up with a 46cm All City Big Block which I ride fixed.

    The handlebars are at 2 inches or so above the saddle level,the stem is 40mm in length, the seatpost has a set back and the saddle is a Brooks Flyer S.
    I never had a bike that sweet. It fits me so well that I feel in control, I feel happy, I feel safe.

    But then, reading your article, I came to think I’m extremely lucky that my bike is such a match for me…

  • Ryan says:

    Alan,

    First off thanks for this series of bike fit articles – good stuff. On either your site or one of the links you provided (maybe VO) the “your handle bar should block the view of your hub” method was discussed. In my case I have the following
    -55cm Handsome devil
    -80 cm stem even with saddle
    -VO grand cru seatpost (which has some natural setback by design)
    -45cm wide Nitto Randoneur handlebars
    -83cm PBH at 5’11″ – short legs long torso

    When I did the hub handlebar test I could see the hub slightly in front (closer to me) of the Handlebars with hands on top of the bar and the hub was just about hidden if I am in the drops. If I understand this method correctly, and here is my question, the fact that I see hub before the hars means my bike is too small correct? I already run a short stem and set back seatpost so it seems i should have gone up a size due to my freakishly (for my size) long torso….?
    Sorry for the long winded post you just got me thinking -Ryan

  • Alan says:

    @GHD

    “What is your PBH and how tall are you?”

    I’m 6’0″ with an 88.5cm PBH. If you otherwise fit the 60 (what’s your PBH?), you might see if you can get a test ride with a stem that has less forward reach.

    Alan

  • Alan says:

    “I did have a question about your 1×9 conversion on your Surly LHT because I am thinking of doing the same for my Trek 520. What sized BB did you use for your Sugino crankset? I’m concerned that a 103mm spindle won’t be able to clear my chainstays.”

    I went with the 103mm Sugino BB-103 which gave me plenty of clearance on the LHT. I don’t know for sure if they’ll clear on your 520, but my guess is that they will.

    Alan

  • Alan says:

    @Sophie

    “I never had a bike that sweet. It fits me so well that I feel in control, I feel happy, I feel safe.”

    That’s super! Congrats… :-)

  • Fergie348 says:

    Thanks for the picture with this one, Alan. It really does say a thousand words. I agree completely with your assertion that frame size, geometry, components and rider preference have a huge impact on what constitutes proper bike fit. No better argument for going to your LBS if you’re not sure what you want/need to be comfortable on a bike.

    Just looking at your picture (thanks for putting your feet in the 3 o’clock/9 o’clock position on your SH), I notice that your knee is further behind the ball of the foot than I have ever been comfortable with. Do you ride this bike primarily or exclusively with flat pedals? I always ride clipped in, and a decent amount of my power comes from pulling back on the pedal when it’s at the bottom of the stroke. I’d get tired quick if my feet were that far in front of my leg! It would be a different issue if I were riding flat and just using my quads to push forward and down..

    Also, your handlebar position relative to the saddle is about exactly where I ride on the tops of my drop bars on my daily commuter. I’m probably on the tops about 30%, on the hoods 50% and in the drops 20% of the time. It feels good to move around on the bike, especially on rides longer than about 10 miles.

  • Alan says:

    @Ryan

    ” If I understand this method correctly, and here is my question, the fact that I see hub before the bars means my bike is too small correct?”

    You have the right idea, but you also have to consider standover height. The next size up from your 55cm is a 58cm. On the Handsome website, they list the standover height for a 58cm as 83.4cm, which is too large for your PBH of 83cm. The bad news (it’s not that bad… :-)) is that you could stand to have a bike that’s perhaps a little longer, but the good news is that you actually have what appears to be the correct frame size for your physique. We have the opposite fit challenges; you with a long torso, and me with long legs.

    All that said, as long as you feel comfortable with your bike set-up as it is, I wouldn’t sweat the bar position – it sounds like you’re in the ballpark, and for those of us who are not averagely proportioned, that may be the best we can do short of a custom frame.

    Alan

  • Alan says:

    @Fergie348

    “Just looking at your picture (thanks for putting your feet in the 3 o’clock/9 o’clock position on your SH), I notice that your knee is further behind the ball of the foot than I have ever been comfortable with. Do you ride this bike primarily or exclusively with flat pedals?”

    I’ve been riding platforms exclusively for about the past 4 years. Also, I’ve spent a lot of time on recumbents and old school mountain and touring bikes, so a position that’s just a little further back than what you find on most bikes in your LBS feels right to me. This equates to something around a 71-72 degree seat tube angle.
    Alan

  • ghd says:

    Thanks, Alan. My PBH is 89, and I’m 5’11″. I think the dirt-drop stem (or similar) may be a better bet than the stem I test-rode with. Will have to see if I can find a 60 to ride with the shorter-reach stem. I like the idea of the bigger frame, at least in principle.

  • Alan says:

    @ghd

    So you’re like me: long legs, short-ish torso. I hope you have an opportunity to test ride the 60 with the Dirt Drop/Moustache combo.

    Regards,
    Alan

  • eddie f says:

    Hello Alan, I know you know your own comfort, but in that photo it looks like your elbows are nearly locked and that makes my arms hurt! None of my 3 road bikes has comfort handlebars and if that was my Sam it would have drops, higher stem, and more extension. That would make it so my elbows were bent and I was able to use them as springs rather than props. Food for thoughts.

  • Alan says:

    @eddie f

    Hi Eddie,

    Don’t worry, I don’t lean on my locked elbows… :-)

    For a relaxed set-up like this, with my back at 60-65 degrees, there’s not enough weight on the bars to require the deep bend at the elbows typical of a racing fit.

    Alan

  • CedarWood says:

    Good information for those of us with short torsos and legs too long for their own good. I’ve been considering the Dirt Drop/Moustache combo for a vintage mixte rebuild, and this post has pushed me a little closer to a decision. Thanks for the info.

  • Ride Report: 09.21.10 | Pedalling Along says:

    [...] to Alan at Ecovelo, a good rule of thumb for stem/top tube/seat position sizing is that there should be a straight [...]

  • Mark says:

    Hi Alan,

    Thanks for addressing a topic that in the current era (i.e., many compact road bike frames) is poorly understood even by builders like Surly, with the result that too many people are fitted to frames that are too small for their body dimensions because top tube length only was considered in determing the fit.

    You mention handlebars, but I would guess that the most material reason that such a long top tube fits you is because you’re using upright handlebars. With drop bars and the same stem length, the top tube would probably feel too long.

  • Mike Bowers says:

    Have you done a piece about fore-aft adjustment of the saddle? How are the guidelines different for a more upright seating position? Is it still knee over pedal axle?

  • EcoVelo » Blog Archive » Proper Frame Fit says:

    [...] Numbers Don’t Always Tell the Story [...]

  • Mel Hughes says:

    Sorry to get in on this one so late. But I am 5′ 10.5″ with a PBH of 83! From what I gather, I could ride a 56cm Hillborne, as long as I don’t put tires any fatter than35mm on it. (Or a 57cm Hilsen. Hmmm…)

  • Alan says:

    @Mel

    Yup, sounds right. 56 Hillborne or a 57-58 Hilsen/Atlantis/Hunqa, etc.

    Alan

 
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