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I've been reading a lot about road bikes and looking at the differences between bikes called "compacts" but I don't see much consistency.

I've read that compact road bikes have different gearing and also a sloping top tube but not necessarily both. I've also seen some bikes with "Compact" in the title but don't appear to have either of those features! Am I missing something?

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The word "compact" can be used in two contexts, both separate from each other.

The first is to do with the geometry of the frame. This is basically where the top tube is sloped rather than level. As is often the case, Sheldon has a good description including the whys and wherefores.

The second is to do with the gearing, in particular the number of teeth on the front rings. This is covered in a previous question: Number of gears for a racer. (Its covered on Sheldon too, close to the previous link.)

If you weren't already aware, Sheldon's site is a superb reference for all things bicycle.

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  • @Bendihossan gold dust – PeteH Jul 14 '13 at 13:11
  • Note that many "compact" frame designs come dangerously close to the old "mixte" style. Not really a new concept, just warmed over. – Daniel R Hicks Jul 14 '13 at 13:47
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    Having assembled a classic (non-slope) frame of a larger-than-recommended size for me, I'd say a sloped top tube has AT LEAST the (rather understated) benefit of MORE SEATPOST FLEX, thus softening road harshness a lot (I didn't realized I would miss this so much). So, a compact frame might be a good choice not only for racing-performance reasons, but also for long-distance riding at a slower pace... – heltonbiker Jul 14 '13 at 15:24
  • @heltonbiker - Yet at least the old mixte frames had a reputation for being much stiffer than a standard diamond frame. – Daniel R Hicks Jul 14 '13 at 18:44
  • @DanielRHicks The mixte frame is an interesting case, since it has the sloped top tube that gives more clearance, while having its seatstays relatively high at the seatclamp, thus not having as much influence on exposed seatpost length and flex. Some say those parallel tubes running from headtube to rear axle are extra weight without that much extra structural strength, but the resulting DESIGN is surely remarkable no matter what! – heltonbiker Jul 14 '13 at 20:30
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The last post is correct about two meanings for compact: sloping top tube as one meaning and a compact crank (smaller chainrings) as a second meaning. A third meaning also exists - or used to exist: a bike built around smaller 650C wheels. Cannondale used to market their 650C-wheeled road bikes as compact frames.

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