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After using some online fit calculators, I was looking around at some bikes and frames. Surly says to pick one based on the effective top tube, for which a recommended length for me is 53.5 cm. Some shops have told me to ride a 54 cm frame, others 52 cm, mostly just based on standover height. I have been sampling some bike geometry and noticed that CX/touring bikes sometimes tend to be very long for their height:

| Bike | Purp | Size | Eff. TT | |-----------------|------|-------|---------| | Surly Straggler | CX | 52 cm | 54.6 cm | | Jamis Quest | Road | 51 cm | 53.0 cm | | Giant Defy | Road | Small | 53.0 cm | | Jamis Aurora | Tour | 53 cm | 55.2 cm | | Jamis Renegade | Adv. | 51 cm | 53.2 cm | | Jamis Renegade | Adv. | 54 cm | 55.1 cm | | Jamis Bosanova | Tour | 51 cm | 54.0 cm | | Jamis Bosanova | Tour | 54 cm | 55.5 cm | | Soma Smoothie | Road | 52 cm | 53.0 cm | | Soma Double-Cr. | CX | 52 cm | 55.6 cm | | Soma Double-Cr. | CX | 46 cm | 53.1 cm | | Trek Domane | Road | 52 cm | 53.0 cm | | Trek 720 | Adv. | 52 cm | 53.8 cm |

So, for example, if I wanted to get a Soma Double Cross, by the effective top tube recommendation, I should go for the 46 cm frame? That seems tiny. By the top tube recommendation, Surly doesn't even make a Straggler small enough, but the extra 1 cm could be handled with a smaller stem? Is there a reason the CX/touring bikes are relatively longer? Wouldn't that result in a less upright, and therefore less comfortable position for long rides?

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    IMHO,effective top tube is the way to go. OTH, fitting calculator rarely applicable to touring bikes due to different geometry than typical road bikes(e.g. longer chainstay, diamond shape to fit more water bottles) – mootmoot Jul 4 '16 at 16:05
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    Dunno about cross bikes, but touring bikes are typically designed to have a longer wheelbase, trading off nimbleness for a smoother ride, more heel clearance to panniers, more toe clearance to the front fender, and more rear fender clearance. Most of the difference is in the chain stays, some is in the top bar. – Daniel R Hicks Jul 4 '16 at 18:20
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On touring and Cyclocross bikes usually the handlebar is higher than a road bike. When the handlebar is higher the reach will be longer (like when you lift your hands they are getting further away from you body). In order to compensate on that longer distance, you can either have a longer stem or, in that case, a longer top tube.

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  • I would add your reach is the longest when your bars and saddle are at the same height. This is the usual setup (or around there) for touring for most people. As you move away (extremely high or low bars) your reach will shorten. People who tour and want extremely high handlebar positions will need a shorter reach (similar to a performance fit), but a much higher frame stack. – Rider_X Dec 14 '16 at 21:26
  • Welcome to Bicycles @Gaia. Thanks for answering one of our questions. Rather than compensate I'd suggest you say accommodate; on first reading it seemed you were saying opposite things in the same sentence. BTW, we recommend that new members take the tour to make best of the site. Good to see you here – andy256 Dec 14 '16 at 23:41
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Modern road bikes have moved to compact frames, which was pioneered by Giant. This was do to several reasons. They are stiffer, when all things are equal. They are also a bit cheaper to produce. They are also easier to fit a larger number of people to fewer frames.

Cyclocross bikes do come in compact and more traditional forms. Surly is about as traditional they come. Touring and Cyclocross bikes share the need for stability during dynamic weight transfer. That's why they are longer, as a rule. A longer wheelbase is more stable/less twitchy.

When it comes to you finding your dream bike, I have some simple advice from the dawn of bike fitting. Stand over the bike, and make sure your um...unmentionables have about an inch (for a touring bike and 2 or so on a Cross) before they make contact with that top tube. You can't change top tube height. Stems, seats, handlebars can be swapped out at will. I would also consider the length from the center of the BB to the top of the seat on your favorite bike. Make sure you can replicate that as well.

I hope that helps, and good luck!

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I would have to disagree that long top tubes are more "traditional". Most of my steel bikes, ranging from 1954 to 1986 or so have square dimensions, 57 top + 57 seat. The only one that doesn't is a comparatively new soma doublecross from around 2004 or so, it has a very long top tube. I also find it uncomfortable on long trips due to being too far forward. I have found the same thing with newer steel/touring bikes. I can't explain it except that I think a lot of frame makers for the past 20 years have sort of worshipped rivendell/grant pedersen which started this long top tube fad. I think it's because they evolved from the 90's mountain biking world which used long top tubes. I think it's a bit ridiculous and would prefer a shorter top tube and longer stem. All that said, once sizes get very small, like below 52, there simply isn't enough room for 700c wheels anymore and compromises must be made, one of those is to keep the top tube long. At this point people should really be using 650b wheels instead. Good like finding what you need, and don't compromise on fit!

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  • The front wheel needs to be at a certain distance from the bottom bracket to avoid toe strike. As such, a shorter top tube forces a stronger angle on the steering tube. And a strong steering tube angle increases problems with sharp cornering. Finally, the further to the front the front wheel is, the harder you can brake the bike. So, from a mechanical standpoint, there are quite a few arguments for not making the top tube too short. – cmaster - reinstate monica Sep 8 '20 at 20:49

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