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I'm comparing the following endurance road bikes, all in 58cm or L:

  • BMC Roadmachine
  • Cannondale Synapse
  • Trek Domane
  • Look 765 Optimum
  • Specialized Roubaix

I'm 6'2" and recently recovered from a herniated disk and hip arthroscopy. Given that, I'm looking for a geometry that is "upright" in riding position.

How can I best compare or measure 'upright-ness' between these bikes?

I know the basics: shorter reach + longer stack == more upright. But those measurements actually seem to conflict here, and I'm not sure the degree to which other measurements may counteract them. For instance, the Roubaix has the longest stack, but also a relatively high reach and the shortest head tube length. The 'best match' seems to very widely by different categories/measurements.

Is there a slightly more nuanced way to compare this measure between the bikes shown here?

enter image description here

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Bike Insights has used stack to reach ratio to compare a number of brands of bikes. One limitation is that they may not have every model and every year of bike entered on their site, but their data appear reasonably complete for major brands. The link I inserted may take you to a comparison of the 2020 Roubaix Comp and the 2020 Trek Domane aluminum (but the carbon Domane has the same geometry). It should show a picture of two overlaid simplified geometry diagrams.

They rate the Specialized in your size as being about average in terms of stack to reach compared to other endurance road bikes, and the Domane as being relatively upright. They discuss their rationale and some limitations of stack to reach here. They do let you visualize how the frame geometry affects the relative riding position between two bikes, although they do not include the effect of the stem and handlebars.

It is important to remember that frame stack is measured to a point just above the head tube (except for the Roubaix, see comments on Adam's answer), and that we further modify fit by spacers under the stem, the stem length and angle, and the handlebar reach. Riser handlebars are rare on road bikes, but a number of Roubaix models are equipped with such bars. Riser bars add further stack to your final position. You may be able to achieve your preferred riding position on any of the models you listed.

You asked about head tube length. To a great extent, the effect of head tube length is already captured in the frame stack measurement. You mostly don't need to worry about the head tube length per se. In the case of the Roubaix, as we discussed, the stated head tube length is deceptively short because it doesn't account for the suspension system (which is mounted in the head tube). The Roubaix's stack measure appears to be taken to a virtual point above the head tube, because the suspension needs some clear space above the head tube itself.

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You're almost there. You can quantify "uprightness" as the stack/reach ratio. Just add another row to your spreadsheet and insert that formula.

I'd say anything over 1.5 is pretty upright; down around 1.4 is pretty racy. You can compensate to some extent with spacers and stem length.

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  • Would you say that head tube length is not as relevant because it is already somewhat captured by the stack? – Brad Solomon Feb 4 at 16:00
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    I'm not sure how head-tube length is relevant here. There may be some way it is, but for your purposes, it is indirect at most. You may want to consider seat-tube length, because the amount of exposed seatpost will affect ride quality a bit (more exposed = more compliance), but that's a separate issue, and you're looking at a couple of bikes with suspension anyhow. – Adam Rice Feb 4 at 16:19
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    @BradSolomon I think the Roubaix's stack is measured to a point above where the head tube meets the steerer. This is to account for the Future Shock suspension. If correct, then the Roubaix's head tube length may be misleading. bikeradar.com/reviews/bikes/road-bikes/… – Weiwen Ng Feb 4 at 16:53
  • @WeiwenNg Ah, good find. I see on specialized.com it's implied to be an extra 20 mm – Brad Solomon Feb 4 at 17:37
  • I think the effective top tube length is more important than the reach here. At least in the MTB world, there's such a range of seat tube angles floating around, reach only provides insight on how the bike will feel out of the saddle, but not how it'll fit. – Paul H Feb 5 at 19:17

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