Wednesday, May 5, 2010

Name That Frame

It is no secret that I am obsessed with classic bicycle design and enjoy referring to different frame types by their names. Sometimes I get emails and comments asking to explain the difference between certain types of frames - for example "mixte" vs. "step-through". So I've put together a basic illustrated guide of sorts - describing some common design elements of diamond frames, step-throughs, and mixtes.

DIAMOND FRAMES
The Diamond Frame - or a "men's frame" - is readily recognisable by its horizontal top tube.

Classic Diamond Frame
Be it on a roadster or a roadbike, the classic diamond frame has a horizontal top tube - like the one shown on the vintage Raleigh DL-1 above and on this vintage Motobecane roadbike. For reasons I will not go into here, this is the most structurally sound way to build a frame. However, it is certainly not the most comfortable to mount: One must swing a leg over the back, or else lean the bike over quite a bit in order to step over a diamond frame bicycle.

STEP-THROUGH FRAMES
A "step-through" is a frame where one can readily step over the top tube without needing to lean the bike to the side or swing a leg over the back. This, of course, means that the top tube must be sloped so as to be positioned low to the ground. There are several popular subtypes of step-through frames:

Straight Step-Through
Usually when the term "step-through" is used, it refers to a straight step-through design, where the top tube and the downtube run parallel to one another. The Raleigh Lady's Sports above is a classic example of a straight step-through.

Loop Frame
A Loop Frame bicycle is a type of step-through, where the top tube is gracefully and symmetrically curved, rather than straight. The curve runs as closely as possible to the downtube, so as to maximise the easy step-over area. Dutch "Omas" and English "Lady Roadsters" (like the Pashley Princess above) are the most common examples of loop frames.

Swan Frame
A less common type of step-through design is the "Swan" frame. Notice that on the bicycle in the picture above (a vintage Steyr Waffenrad from Austria), both the toptube and the downtube are curved. The tubes curve around the front wheel, forming a shape resembling a swan's neck - and allowing for the same easy step-over as the straight step-through and the loop frame. Today we can see this design on the Azor Swan and the lady's Electra Amsterdam.

MIXTE FRAMES
Mixte means "mixed" or "unisex" in French. It differs from a step-through in two ways. First, it is not quite as easy to step-over, because the positioning of the sloping top tube(s) is higher. Typically, the rider will still need to lean a mixte to the side a bit in order to climb over it. Second, a mixte possesses a key structural component that a step-though does not. If you take a look at the three examples of step-through frames above, note that the top tubes extend from the head tube (where the handlebars are) to the seat tube (where the saddle is). A mixte frame has "stays" that extend past the seat tube, all the way to the rear dropouts (see pictures below). This design element was created to strengthen the frame for long, intense rides. There are two general subtypes of mixte frames:

Classic Mixte: Twin Lateral Stays
A mixte with "twin lateral stays" has two thin tubes running in parallel from the head tube past the seat tube, all the way to the rear dropouts. Note in the above picture of my Motobecane Mirage, that the tubes are separated the entire time. My custom Royal H. mixte frame and the new mixte frame from Velo Orange are examples of this design.

Alternative Mixte: Single Top Tube that Splits into Twin Stays
We do not own a bicycle in this category, so I borrowed a picture of a vintage Rene Herse from this earlier post. On this type of mixte, there is a single, sloped top tube that stops at the seat tube, then splits into narrower twin stays. The Rivendell Betty Foy is a popular example of this type of frame today.

So there you have it: some common frame designs in three categories. This post is not meant as a complete list of all the possible classic frame designs that have ever existed. There are countless hybrids of the frames I've described - such as mixte frames with curved stays, step-throughs that are mostly straight but curved just a bit at the ends, loop frames with different degrees of loopiness, and so on. There are also additional categories, such as priest frames, truss frames, classic cruiser frames... the list goes on. So many beautiful classic bicycles, so little time! Of course my personal favourites are the loop frame and the classic mixte.

28 comments:

  1. This post is awesome. I'm not too proud to admit that I got all confused in my head when it came to frame types. So thank you! You're a regular Encyclopedia Brown when it comes to bicycles!

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  2. Excellent essay! I'd never really straightened all these step through frames in an organized fashion before. I guess there are even variants on the classic mixte in the ways the top tubes interact with the seat tube and the rear brake.

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  3. thank you- very informative. The first time I was able to understand the true diff of a mixte and a straight step through and reminds me of the term Loop frame.

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  4. Thank you SO SO MUCH for this guide! So helpful! I'm sure they're a lot of work to put together, but I'd love to see more of this type :-)

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  5. You have a talent for making sense of things for newer riders. While the rest of us are blathering about what we have/want/like, you're making cycling more accessible!

    Always a fan,
    Michael

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  6. I love these informative posts...I have learned more about bicycles from your blog than anywhere else (yes, including forays into the library!). Thank you!
    Kat

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  7. Very nicely written.

    I always appreciate the clarity in your prose. It's clearly well thought out.

    -david

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  8. What a great post! Excellent photo examples too. (That swan frame is just dreamy...)

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  9. Thanks for the feedback; I am glad people are finding this post useful. There are quite a few things I've left out, so as not to overload with too much information at once. But perhaps I will flesh this out later into some sort of encyclopedia-type entry with drawings and additional details.

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  10. Great overview!
    One of my favourite designs is the “alternative mixte” (with or without the additional stays).

    Nico

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  11. @ Velouria - it's difficult to do frame-design justice in one post, but you've done a very good overview here. There are of course areas selectively you left out, but I feel that well-edited posts such as this give a good overview of the basics of vintage European-inspired frame design. Since your blog concentrates on that era and attracts readers interested in such an era, the focus and editing help a great deal.

    Thanks for sharing your writing, and for doing it well. As someone who appreciates good writing, I always enjoy reading your posts.

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  12. The color of that Herse mixte is kill-ing me.

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  13. Thank you for pointing out that a sloped top tube is a departure from the standard level top tube of the diamond frame. Personally, I want my top tube nice and level, just like in my Motobecane. :)

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  14. David - Thanks so much for the kind words : )

    neighbourtease - Yeah. A vintage bike shop in Philadelphia is selling an original Herse mixte in phenomenal condition if you are interested...

    MDI - I am actually not sure when the sloped top tubes began to come into use; would love to find out.

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  15. Great post! Interestingly Kona chose a swan design for their Africabike. Click on my name to see an example in Mozambique.

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  16. wow, this is truly very informative! tks for the effort. would you care to comment on the pros and cons of cantilever frames? or are there no benefits to be had except perhaps an exercise in styling?
    TIA

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  17. Congratulations for this interesting post.
    I'd like to add that classic mixte design is also known as Albert Six in memory of the builder who was the first to use it in the 30's for his tandems.
    More details for those interested and reading french on the site Tandem Noir http://pagesperso-orange.fr/tandem.noir/pages/tandem-t2.htm

    Denis

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  18. ohchusan - Do you mean frames with cantilever brakes, or something different?.. I think the benefit is braking power, which is why you often see them on off-road bikes. But I doubt that you will see many classic bikes with these, Rivendell being the exception.

    Denis... Wow, thank you for that information. I have been trying to research the history of the mixte for the past year, but have not gotten very far; there is not much available!

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  19. Nice post, I agree. The Sam Hillborne geometry is completely different from a mountain bike or "compact" road bike however. Mountain bikes have sloping top tubes in order to increase standover and road bikes do it partly to make the frame ostensibly lighter and stiffer. The Hillborne is an "expanded" frame design, to allow for a more comfortable fit.
    http://www.rivbike.com/products/show/sam-hillborne-framebike/50-700

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  20. Thanks Jim. I do know that the Hillborne frame is an expanded design, whereas most sloping MB and road frames are compact - but I figured this point was beyond the scope of this post, just like differences in angles and wheelbase and all that. One thing I've been curious about, is whether any vintage bikes were designed with sloping top tubes, or whether this is a fairly recent invention.

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  21. "I am actually not sure when the sloped top tubes began to come into use"

    When it comes to bicycles everything old is new again. Although the sloping top tube is thought of as modern it was actually one the most popular frame styles from the 1890s up to about WW1.

    As in this portrait of Henri Desgrange astride his bike at Wikipedia: http://tinyurl.com/27gqyeq

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  22. Re sloped top tubes - apologies to those part of the discussion, but I have now removed that from the "diamond frame" section, because I think the distinction was too confusing. This was supposed to be a very basic categorisation system : )

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  23. This is so useful - thank you!

    Could somebody please describe how to pronounce "mixte"? I asked one bike shop if they had any of this type of frame that I could try out and just got a strange look, so perhaps I have been mispronouncing it.

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  24. I'd like to read your impression of the "Public" bicycle, available in diamond, mixte, or loop frames, with internal gears up to 8 speeds on some models, and derailleurs on others. They appear to be intended as a practical, daily use bicycle.
    I'm not an owner, but am interested in them.

    http://publicbikes.com/BIKES

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  25. I've always pronounced it something like "meekst." Assuming it's a French word, it shouldn't be far wrong. As for types of frame, the Dutch still make a cross-frame bicycle (kruisframe or pastoorsfiets). Apart from priests being able to ride these wearing a soutane, I gather they smooth out shocks from rough roads. This type, made by Raleigh, was used extensively by An Garda Síochána, the Irish police force, before they all got cars.

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  26. Regarding the sloping top tube, I fear it's a ploy by the bicycle industry to get away with producing a much smaller range of frame sizes. Think about it. With a regular diamond frame, with a horizontal top tube, they used to have to make a range of sizes with all the main tubes in proportion. Now, with a top tube which slopes down towards the seat cluster, all the adjustment is in the seat pillar, and you get maybe three sizes, max. Aesthetically, it doesn't look too great either. Yet you see a great many of these bikes which people pay big bucks for.

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  27. I just got a Specialized Expedition which has a "U" frame. Apparently it is a wider bore tube with 2 tracts inside. The shift and brake cables are actually inside the tube, protecting them from the elements.

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