Monday, February 22, 2016

Size, It's Only Just a Number!

So I am working on a project for a bicycle manufacturer, where I'm suggesting geometry specs across 4 different sizes of the same model. It's a city bike. Or, more accurately, an upright town/country sort of bicycle. And it's got me thinking about how sizing has historically been treated by manufacturers of this type of machine. And how has it been treated, you ask? Badly!

You know how clothing sizing is not quite the same across brands? According to some American labels I am a size 2 and according to others a size 8. In the UK I might fit anything from an 8 to a 14. And in the EU, where I'll fall between 38 and 44 is anyone's guess. In my youth I thought this was an evil uniquely inflicted on women to drive them insane with body image issues. But subsequent shopping trips with men revealed it as a unisex problem.


When it comes to bicycles - and namely bikes of the utility, plainclothes, hop on and go, or whatever you want to call it variety, matters stand similarly. For while bicycle sizing makes it seem as if it's based on concrete numerical measurements (a bike can be described as a Size 54cm, or 57cm, for example), what those measurements refer to - and, perhaps more importantly, what they omit - can essentially render them useless.

Take, for instance, the lovely BSA above, of 1970s vintage. Never having had occasion to measure it before, I finally did so last night to get a sense of the proportions an "average sized" diamond frame might have around 26" wheels. But with the measurements I ended up with, I would not even know how to describe this bicycle's size! While the seat tube is 570mm (if measured center-to-center; or 582mm if measured center to top - but that distinction is another topic!), the top tube is a shockingly short 545mm across.

Now I suspect that BSA, back in the day, would have described this puppy as a "size 23" referring to the (c-t) seat tube figure in inches. And I also suspect that all of their sizes for this model would have shared the same identical top tube length, as would have often been the case with English 3-speeds - ensuring that most riders would feel either inordinately stretched out or uncomfortably cramped on their bikes.

Getting back to the BSA, its 570mm x 540mm dimensions explain why my husband - who is 5'11" with a long torso - finds this machine simultaneously too big and too small: He can hardly straddle the top tube, but once astride the bike the "cockpit" feels too small.

For this reason precisely, the French have traditionally described their bicycles by the top tube (or virtual top tube) length. And today, most roadbike manufacturers do the same, believing this figure to be more informative when it comes to fit. But describing a bike like the BSA as a Size 54cm would be problematic, as (1) most people short enough to be attracted to that size would likely not be able to stand over this bike, and (2) it would mean that all of BSA's sizes for that model could be described as 54s!

The existence of these different sizing methods can be confusing. Which of the bicycles above, for instance, both built around the same wheel size, would you say is "bigger"? Some would say the small-looking one of the right, as its top tube measures 56cm. Others would say the one on the left, with its 57cm seat tube. It is good to keep this in mind, whether buying 2nd hand, or ordering a new bicycle without test riding, and without the benefit of a complete geometry chart!

But the truth of the matter is, that in order for either the seat tube measurement or the top tube measurement to be informative as to a bicycle's true size, the frame as a whole has to use "proportional geometry" - meaning, that as the sizes go up, the seat and the top tube (or virtual top tube) expand in unison. And while this is not an especially radical notion, you would be surprised how few bicycles designed for an upright position even today take care for their geometry specs to be proportional across sizes. It is almost as if, on an upright bike, the rider is not meant to care about  positioning. The fact that most upright bicycle manufacturers do not release their geometry charts contributes to that impression.

While some in the bicycle industry insist a meticulous "dialing-in" is crucial even for casual upright cycling, others shrug and say that a bicycle "fits" if you can manage to hoist bum on saddle, or stand over the top tube without your privates catching. My own views, I guess, fall somewhere in the middle. Certainly, compared to a roadbike - where the difference between pleasure and pain can be measured in milimiters or halves of a degree - upright bikes are  more forgiving. But it does not follow that fit is altogether unimportant. One can be uncomfortable on a "comfortable" upright bike. You can spot the riders who are over-stretching awkwardly, reaching up as if their bars were ape-hangers,  or hunched over painfully. You can also spot the ones with the waaaay-too-tall stems (or seatposts) trying to compensate for inappropriate frame proportions.

An informative, cyclist-oriented model of upright bicycle sizing must consider overall fit and not seat tube length or standover height alone. Otherwise, what is size, but just a number?


57 comments:

  1. I always have a problem with fit. At 5' 6.5" tall and a short reach, city or urban hybrids fit me best. I can't ride most road bikes as the top tubes are too long and the steerer tubes too short. If I do get a reasonable fit with a WSB, I usually use a riser stem anyway. What I need is a quill stem I can raise or lower and a bike with a longer steerer tube, but not so much that it puts me into an extreme upright position. I prefer a more aggressive or relaxed geometry in an upright bike. Generally, a 50cm [20"] seat tube and 530-535mm [C-C] top tube works pretty well for me with flat or drop bars. I still usually have to have that riser stem. A good standover height for me is 29"-30". I go through stems and seat post changes more than I'd like. If I want city bars [North Rd. or similar] I need a longer top tube.

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    1. Funny, I am the same height as you exactly and also prefer 500x530 frames for road - but with a 100mm length stem and drop bars set very low!

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    2. Yes, we are all so different. I have a very short reach.

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  2. I thought generally a pair these days, namely "stack" and "reach". But yes, still only numbers.

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  3. In my book it's let the buyer beware, always. This is not a new thing and a constant reminder to try before one buys. I hate buying things…hate…and today found myself in need of new jeans because my two old pairs were completely worn out where the sit bones are located on the saddle. So I walked into my local used clothing shop and looked for the size Levi's that matched my other pairs and found one that matched. I was going to the counter to just pay for the thingt and leave but thought maybe I should try them on since it's been a half dozen years between purchases. Turns out styles change though numbers do not. They were oppressively tight and unusable to cycle with, let alone for a sixty year old man! Bikes have always been the same. Measuring one tube is only a starting point and has gotten more complicated over the years, just like jeans. Once one knows the brand one can make better initial choices but everything should be tested. Just b/c someone says it's good does not make it so.

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    1. Thanks to cycling I cannot wear trousers anymore, let alone jeans. My small waist/ big thigh muscles proportions are just not accommodated for, and trying stuff on that's like Size Gazillion but won't go on over my legs gets depressing. Thank god for skirts and stretchy tights.

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    2. Thank goodness for cycling or I'd have to wear a skirt around my frame instead of being able to fit into trousers!

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    3. Can't wear trousers? That is called hypertrophy. The bike didn't do that. Bikes are inanimate objects. It was how you chose to operate the bike that did that. Slam big gears all the time and look to get all your power on the downstroke you get big legs. Use the gear lever and start to learn how to pedal your legs will get slim. Every guy I've known who turned pro got a whole lot smaller while getting a whole lot faster. The only possible cycling that might maybe, just maybe, call for legs that don't fit in normal jeans would be kilometer time trial on the track or match sprinting. Some specialists in those disciplines are relatively small.

      Your body can be what you want it to be, all that's required is an adjustment in technique. If you ride like a weightlifter on wheels you will look like a weightlifter. If you think more like a marathoner you'll end by looking more like a marathoner.

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    4. Oh goodness. Thats what I get for hyperbole.

      For the record, I do own several pairs of trousers! Also my legs *look* skinnier than they did pre-cycling. But there must be more mass, distributed in a way that fools the eye.

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    5. I have seen photos of cyclists with very large legs (thighs) and have wondered about this - I've been cycling all my life and have quite thin legs - and mountain bike riding does require some power input - now I'm thinking that what the poster above suggests must be the reason - constant 'mashing' down on the pedals in a high gear.

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    6. This is actually worth a post in itself!

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    7. I have tried distance running, cycling, not cycling, not running, working where I lift heavy weights all day, work where I lift nothing heavier than a pencil, I have found that while there is a difference in fitness and some difference in strength, My body maintains a pretty similar overall muscle distribution - large thighs and shoulders - the genetic/epigenetic aspect to this seems pretty strong.

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    8. If you are talking about Levi's 501, yes, they had have had a more popular version that people can buy that is washed, or preshrunk. Much, much different than raw, shrink-to-fit. Giving way to our instant gratification mentality.

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  4. The proportional sizing of bicycle frames has varied historically, even though the proportions of the human frame have remained historically various -- until recently the two seldom have seemed to coalesce. There is an informative, if brief, history of how English and continental frames have changed in their proportions on Hilary Stone's website (in the frames section, obviously). Just google Hilary Stone. The Fossil

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    1. I heartily agree. HS's frame size discussion is very helpful - concise but historically sensitive. The piece certainly suggests a uniform language is unlikely any time soon given style shifts. I actually find measures fore and aft of top tube point over bb most helpful.

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  5. Fit is the most important thing when purchasing a bicycle. Calculating averages helps but is far from perfect and if you read this blog I suspect you understand that thought. If your bike is a recreational fashion, it's less important. If it's your mode of transportation and connection to reality, pay attention to what works for you and not the numbers.

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  6. Um, English bikes are almost always measured center to top and 582mm is within a hair of 23". The BSA is certainly a 23" frame.

    Over the years I believe my count of custom made bikes is six ordered, three actually delivered. Only one of them much fit me when I got it. Then there was my Cinelli. Andre Cinelli only knew me as a voice on the phone, a guy who worked at a bike shop in the States. He asked me what size I would ride, I said 58. He told me there would be two 58s in the shipment, the one with Super Corsa stickers was for inventory, the one with Speciale Corsa stickers would be mine. When the bikes arrived the Speciale Corsa was a knockout. Thirty beautiful Cinellis all in one place and mine was obvious. Then the shop guys started critiquing the geometry and wondering what the heck this bike was supposed to be good for. It was good for me. As long as I owned that bike hotshots in the know kept telling me it was downright strange. I loved it, rode it 100,000 miles, completely wore it out. No way will I ever know if Andre offloaded an oddball frame on me or if he knew something. I twice tried to order a straight copy of the geometry, no one would build it.

    Do not believe published geometry charts. There's many a slip betwixt cup and lip.

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    1. Right you are, it would have been described as a 23" (changed it).

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  7. Most bikes, these days, are very adaptable. Seat posts, stems, handlebars, are easily exchanged for a better fit and style of riding. Frame geometry is another issue and I suspect most buyers could care less.

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    1. It's a good sign when the buyer does not care IMO, as it means the bike is comfortable.

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  8. Back when all bikes were sized according to seat tube length, I usually ended up with a top tube that was too long for me, as I have a short torso. So, I raced on a bike with a stem that had only an 8cm extension. That dampened the steering responsiveness.

    Later, when I bought bikes according to their effective top tube size, I ended up with a shorter seat tube and had to ride with long seat posts, even on my road bike. That never felt quite right.

    Now my custom bikes have 55.5 cm seat tubes (center to center) and 53.5 top tubes. They feel so much better, and I can ride with a stem that doesn't blunt the bike's handling abilities.

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    1. Out of curiosity, what did not feel right about riding with a lot of seatpost showing? Was it an aesthetic dislike, or could you feel it flex?

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    2. I for one still believe it's immodest to show so much seatpost.

      When people actually CARED about these things, the rule of thumb was no more than 2 diameters of the post showing above the seatlug on anything but racers, and 4 diameters out of the frame was risque even for Trackirons. But in this day of "letting it all hang out" you'd think there was NO SUCH THING as a minimum insertion mark. Why there are riders whose surnames I don't know but who's naked seatpins I've been forced to spend entire afternoons staring at(not that I'm into that or anything). People will stop wrapping their bars next...

      It's shocking. Simply shocking.

      Dizpinny

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    3. It would be possible to draw/design frames with wildly differing dimensions that all gave the same seat/pedals/grips position as Justine's 55.5x53.5. They would not all feel the same. Myself I can ride from 57cm to 61cm, but I would never buy a 57 and I doubt I'd buy a 61. I know from hard experience that a compact, sloping top tube frame that is really honestly seriously just the very same thing as a 59 is not at all like a level top tube 59. Bought that one from two guys I've known for decades who are still the best in the business, are widely held to be the most scrupulously honest and honorable guys in the business. They've proved, to me and to anyone else, that they are brilliant designers. Feels different with lots of post out. There may be no explanation that a mechanical engineer could consider as real, not imaginary, it still feels different.

      As for getting the same position on different bikes, I don't even try any more. The bikes are different, let them be different. I have a new one (58 years old) that barely allows me to get 7cm of saddle setback. I would prefer 10-12cm. Now I do know how to play games and get the saddle way back regardless, but if I want to use period correct parts it would be hard. So instead I'm getting the experience of sitting closer to the bracket. The experience most people have on their bikes. And it's fine. It's different and it's fine. It's been different, it's been unproblematic. I'll never take that bike for a 12 hour ride and that's fine too.

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    4. Velouria--I actually could feel flex from the post. And that was when I was skinny! And, truth be told, I didn't like the aesthetic, either!

      Dizpinny--I love your response.

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  9. And then there is men's and women's proportions...

    My wife and I are the same height, but her legs go all the way up to here while my torso goes all the way down to there. There's no way the same frame is going to properly accommodate both of us without compromise—sometimes problematically. It's my sense that bicycles have traditionally been proportioned to fit the longer torso and arms of a man unless specifically designed to work with female proportions of longer legs and shorter torso.

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    1. I am 4" shorter than my husband but my legs are nearly the same length. Not all women's vs men's bodies express the same differences though. Personally I do not like "women-specific" geometry on bikes, as I think it often creates more problems than it solves. Regardless of gender, individual differences in proportions is why persons of the same height might require completely different bike sizes.

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  10. Enough space behind the rider for a childrens seat and somwhere to put your groceries. To manage the bike with those two things in place gives a step-through frame.

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    1. I do not actually understand how some people can ride diamond frames with a crate piled high full of stuff (or a kid) on the back. I've watched them swing a leg over, but the mystery of it still evades me!

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    2. Well I do that and sometime the mystery evades me too. Usually if the load in back is tall I swing my leg over the front. That can be complicated by wide bars. More than a few times I've snagged cables attempting this. The worst is when you got on the bike without problem and then can't get off. The ultimate solution is to drop the bike to the ground and then "dismount". That one always works but can be embarrassing. How all this is done while balancing a child on the back completely escapes me. I've witnessed it many times and remain baffled.

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  11. Frame sizing!? I am sure we could all write a book on that! For many years, riding cruisers or Mountain bikes I knew my size was either a Medium or an 18" frame, there was a discrepancy here and there, mostly I was riding bikes with 26" wheels so overall it worked/no issues. Then I started riding frames with "road sizing" 48, 52, 55, Etc. and bikes with different wheel sizes, even Mountain bikes were getting out of the Small, medium, large into 5 or 6 sizes, this confused things quite a bit! The problem with sizing things from the center of the bottom bracket to the top of the top tube or the length of the seat tube is that dimension will change quite a bit depending on wheel size and bike type. A touring bike with 700C wheels will have more Bottom bracket drop then a Cycle cross bike with the same wheel size or a bike with 650B or 26" wheels. This will of course effect the "frame Size"!! Anywayz, now I look at two numbers when buying a bike (OK more than that, but the two main ones are) Standover height and top tube length. 77CM is just about ideal for me (although Grant says I could go more) and because I have a long torso (like your Beau) I go for the longest top tube I can find especially If I am running swept back bars as opposed to drops.
    Just my opinion, but I would think that sizing the bike by the effective standover although not perfect is preferable to the way they do it now. Sizing a bike that way yields a number that anyone would immediately know they could fit regardless of use, wheel size, etc. which could be invaluable in this, the Internet age where people buy things sight unseen.
    - masmojo

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  12. I am fascinated that my workcycles fr8 is comfortable for me to ride and I'm 5'5" with short legs/short arms/long torso yet the same size bike can be ridden by a much larger person comfortably I'm told.

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  13. I never gave much thought to fit when I was younger, being one of the "if you can hoist your bum" crowd. A youthful body will flex enough to handle a variety of ill-fitting bikes. However, at the ripe old age of 66, I just had my first bike fitting session. While the flexibility is still there (somewhat) the recovery time from the various "new" aches and pains is longer. And there are more. I ride with my adult son (28 yrs old) and all he needs is sufficient stand over height so as to not crush his private parts. I'm curious whether a proper fit from an early age makes a difference in when those aging pains make their presence known.

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  14. I own 2 bikes, a size 53.5 Velo Orange mixte 700C and a 49.5 Soma Grand Randonneur 650 B. The mixte has a 53.5 seat tube and 575 effective top tube. I run Nitto albatross bars and a 8cm stem. It's comfortable. The Soma has 49.5 seat tube and 530 effective top tube. There's lots of seat post exposed and I run a 5cm Nitto tallux stem all the way up with an inch of spacers as well and a short reach, shallow drop handlebar. It's comfortable. I'm 5'6" with 80 cm pubic bone height which I think is pretty normal. My probably over-generalization from this limited experience is that "road" bikes are not designed to fit women and mixtes are.

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    1. By roadbikes do you mean bikes with drop bars, or bikes with diamond frames? Either can fit a woman nicely, but the proportions of a bike you intend to set up with drop bars would have to be very different to one you would sent up with swept back bars.

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  15. Ohdon'tgetmestarted. I'm a titch, 5'3" with short torso but long legs (30" inside leg). I have a Brommie which I found overlong in the reach until I tilted the handlebars back an inch. Moving the saddle forward didn't work as it meant raising the saddle to an alarming height. I was lucky to find that the handlebars could be tilted back a little - from the side, the handlebars follow the curve of the front head tube, quite elegant really. All is harmonious now and it feels perfectly comfortable, but it was a near squeak. I cannot find another bike in any bike shop which fits me so well. I remember your blog on an older Brommie which shows it used to be a shorter bike. Why, oh why don't bike manufacturers cater for those of us who don't want to ride stretched out so it pulls painfully at your back muscles ...

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    1. I suspect the reason Brompton lengthened their virtual top tube at some point, was because their customers (at the time) were predominantly male. Would be nice if they offered a shorter TT version again; even for me the reach is longer than I prefer and I am 5'6.5"!

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    2. Agreed. Please have a word with the amiable Mr. Will B-A. I'm guessing he'd listen to you :)

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  16. I am 5'6" with long legs and arms - I have the seat post raised and saddle set back as necessary, then I am right to go - this is with bikes sized as 'medium' - I would never ride a bike with a small frame. I'm thinking this measurement issue would only be a real problem for those ordering bikes on-line - I have always bought my bikes from my local bike shop and have had no issues.

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  17. I once bought a bike frame on ebay, a Bridgestone MB3, that I thought was my size, and was ticked off when it proved to be two sizes smaller than advertised. I shared my frustration with the seller, but then realized that the measurement he had provided was the top tube length, not the seat tube. It wasn't a lot of money, and the bike built up into a nice commuter for a friend. 1of course measuring frames can be tricky. But as soon as I saw that photo, I knew the tape measure belongs to a knitter.

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  18. My cousin and I were mountainbiking a couple of weeks ago; him on his Cannondale and I on my GT. Both frames are size large, and we're both very happy with our respective bikes. Nonetheless we decided to swap bikes during the ride and he described my bike as being more compact and definetely shorter and I had the exact same feeling about his bike. Upon measuring the bikes we learned that my bike had was longer overall and had longer reach. Go figure.

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    1. seat position and/or angle maybe?

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    2. It's very exciting that your getting involved in bike design. I am working on a accountancy course and have learnt how companies can benfit from collaboration with super bloggers like yourself!

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    3. Do you mean the companies benefit from the blogger's popularity? I am not sure the niche bike industry and myself are at a scale where that sort of effect would kick in! And besides that works only if the affiliation is promoted.

      I have been involved in bike design for a few years now and most of these projects have not been publicised. Typically I am asked for my opinion on some aspect of geometry, or, less commonly, to spec out a bike from scratch. In the end, the manufacturer may or may not use my contributions in the finished product (I imagine I am not the only one being asked), and sometimes I do not even know whether they do end up incorporating my input or not. In any case, this kind of work is somewhat different from a collaboration where my involvement in a product warrants putting my name to it and also gives the manufacturer the (questionable!) benefit of such an affiliation. Between the two, honestly I prefer to be involved in the role of anonymous designer rather than "blogger collaborator," although at times it can feel frustrating to not have control over where the finished product goes.

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    4. I would imagine the manufacturers you work with are aiming to benefit from the modern business approach of being customer led. In a way you represent their 'best salesperson' and advocate of their products. For example, in the fast fashion business I understand bloggers like http://www.theblondesalad.com/ have worked with companies to highlight their products to consumers. You seem to be getting involved at the design and also promotional stages of the company. More to come?..

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    5. Also, I have learnt that social media is increasingly important to companies marketing departments. As a separate issue that gaining feedback on product design from people such as yourself increases their 'market led approach' to understanding and meeting customer needs to ensure consistency in improving performance.

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    6. I understand what you are saying and there are certainly companies, and bloggers, who follow that model.

      Personally I see design and promotion as two separate categories and try to make this clear to companies who express interest in hiring me. These days if a manufacturer (or individual builder) asks me to help with design, it is usually because they've heard from others in the industry that I know bike geometry, am familiar firsthand with a wide range of bikes within specific genres, am proficient in bikeCAD (frame building software), and understand the nuances of framebuilding from having done a course with a master builder in 2012. Very seldom do the companies who ask me to help in this context also see me as a promotional vehicle. But of course some do. Which is why I always try to clarify whether "design" also involves promotional involvement, then make my decision.

      This question of skill vs promotional value is not unique to the design field. When I am hired as a photographer, or a writer, it can be by someone who doesn't even know, or care, about Lovely Bicycle, or it can be by someone who explicitly hopes to benefit from affiliation with the blog. And, as with design, best I can do is clarify my role in advance so that our expectations match.

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  19. One bemoans the lack of standardisation in everything, particularly annoying with bikes I agree, but a standardised society would be worse.

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    1. No to a standardised society!
      Yes to reasonable bicycle sizing!

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    2. Trying the bike is always to be recommended although I've bought many a machine untried via the Web and never had a problem.

      Mischievous thought, many of your male readers will be deeply relieved by the article headline.

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  20. the geo on my 28" gazelle basic step through is perfect

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  21. "Certainly, compared to a roadbike - where the difference between pleasure and pain can be measured in milimiters or halves of a degree - upright bikes are more forgiving."

    Why?

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    1. The leaned-over roadbike position tilts the body in a way that puts pressure on the hands and on the most sensitive parts of the genitals, as well as potentially strains the back and shoulders - which can result in pain, numbness and even nerve damage, unless an optimal balance between pressure points is achieved. This is especially true for riders whose core and upper body muscle tone is not sufficiently developed to hold up their torso whilst leaning forward aggressively.

      On a bicycle with swept back handlebars, the upright position is more similar to the natural sitting position we are all accustomed to. With the body tilted back at the pelvis, the sensitive bits of the undercarriage don't press into the saddle; the hands are resting on the grips; the back is much straighter and the shoulders more relaxed. In this general position, because there is less potential for strain and pressure, fit is more forgiving.

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    2. Simplest way to relieve pressure on the hands is to pull on the bars. We are descended from four-footed creatures who used all limbs for propulsion. Use your arms. A pure static load is going to hurt.

      Simplest way to relieve pressure on the saddle is to put weight on the pedals. Even intermittent effort relieves the butt from compression. With really good pedal style (not simple) there really isn't much weight on the saddle.

      Unfortunately cycling is unavoidably hard on the back. Nothing for that one but strengthening exercises

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  22. Excellent blog post here, and best of luck with the project you're doing for the manufacturer. I have struggled with frame size since determining a couple of years ago that my Trek flat-handlebar road bike frame is too small. At age 52 now, I'm looking to be a bit more upright while keeping the bike lightweight. You make excellent points about the variety of factors that determine a bike's real "size." It's certainly more than the length of the seat tube. The bottom line for me is that I need to ride more bikes to learn what works best for my requirements. It seems the cheap Schwinn hybrid I road prior to the Trek fit me better than anything. It's just that the thing weighed a ton. I love your blog and photography!

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  23. Neither of these bikes look comfortable or enjoyable as is but like all bikes there's potential for making something work.

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  24. This may still be overly simplistic, but why not report frame sizes with two numbers (forgive my terminology if there are generally accepted ones already in use)?

    1. Center of crank (call this Point C) to top of seat tube (call this Point T, defined by height where top tube meets head tube; I'll call the center of the head tube at this height Point H)

    2. Point T to Point H

    In other words, what I typically think of as frame size (seat tube length) is C-T. What I typically think of as "reach" is T-H. These define two sides of the triangle C-T-H-C, where the length H-C depends on the angles.

    Given variations in available seat posts, saddles, and stems, I would think that at least most riders would be able to know in advance that a 58/53 would fit them (cm in both cases).

    My current road bike, a Specialized Roubaix, is labeled a 54cm. When I measure from the center of the crank, I get:
    a. 45.7cm to where the top tube intersects
    b. 50.8cm to the top of the seat tube
    c. 58.4cm to point T
    d. 53.3cm from point T to point H

    Oddly, the distance that comes closest to the labeled 54cm is the one distance I least associate with that measurement.

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