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Some comparable bicycles have a crossbar (top tube) that's horizontal:

Windsor

Others have one that's sloped:

Trek Crossrip

What are the reasons for either frame design? Is it merely style preferences? Or is there more to it, like performance and comfort?

(Assume a mens frame.)

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The second bike is a trek crossrip which is a commuter cross bike (i.e. "cyclocross" for the road), so has a slightly different geometry (bb height, etc.), while the first one is a standard road bike (in fact, a woman's bike). –  Batman Apr 19 at 19:28
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I'm assuming the images were for illustration only. Two other examples are the Giant Propel Advanced (standard) and the Giant TCR Advanced (compact). Both of these are mens' road bikes and could quite conceivably run alongside each other on the same ride. Last year, Team Belkin's riders had the choice of either of these bikes in the Tour de France. (Not sure how this stands with Giant-Shimano this year.) –  PeteH Apr 19 at 20:09

2 Answers 2

up vote 5 down vote accepted

I thought this was an interesting question, so first of all, +1.

First off, the sloping tube (your second image) is known in cycling parlance as a compact frame. I found an article on the Giant web site about the advantages of a compact frame. When I say "advantages" - this is Giant's word not mine!

The full article is here, but to summarise it:

  • the compact frame is smaller than the corresponding standard frame. Therefore, less material is used in the manufacture. Therefore, it is lighter.
  • Again because it is smaller, it is stiffer
  • With traditional designs, to stiffen the bike designers use stiffer materials which unfortunately makes the ride rougher. By using the natural stiffness of the frame, materials don't need to be stiffened hence the ride is comparatively smoother
  • because the top tube is lower, it is easier for cyclists to get a good fit

Now I'll say straight away that you can attach your own weight to some of these features, this article has a whiff of marketing about it. But it certainly gives you some food for thought.

Interesting also to note that Giant's current top-of-the-range mens' road bike (the Propel) has a standard frame (i.e. horizontal top tube). Take from that what you will!

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I'm not sure how much of this is marketing, but I believe the main reason is comfort.

The longer seat post has more flex to absorb bumps and the seat stays being lower gives the rear triangle more flex too.

Another advantage is a lower stand-over height for bikes with high bottom brackets.

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