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I'm playing with my fit a bit as I have gotten much more flexible since I had a bike fit 2 years ago (+1 to stretching and foam rolling.)

As I'm experimenting with drop I am wondering if it makes more sense to adjust my stem angle going from 0 degree shim to -2 degree or removing the last spacer (~5mm) I have below the stem to adjust the overall stem height(SLAMMED!) Is there traditionally an order of operations for these types of adjustments?

Should I consider going for a longer stem at a certain point?

Thanks for the help and I realize it might be time to get a new fit but figured I play around with it a bit first.

  • I would play with spacer stack first - fewer bolts and i'm lazy :) End result with bars at same height is largely cosmetic. – mattnz Apr 25 at 21:17
  • Spacers first, then maybe angle shims. The main issue with the shims is that they change the angle of the handle bars as well, going from -4 to +4 for example results in an 8 degree change in your handle bar (and hood angle). You will then need to reset your bars, which can be annoying if you don't have a tool like a digital level. – Rider_X Apr 28 at 6:04
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Assuming you've got a stem of about 100 mm, changing the angle by 2° will lower the handlebars by about 3.5 mm. If you want more drop, remove the spacer first. Obviously the difference between the two is tiny, and probably not perceptible.

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Should I consider going for a longer stem at a certain point?

For the changes you are looking at, probably not, however at some point you may need to change your stem, but surprisingly you typically need large changes in stack before you really need to worry about stem length. Note that as you drop the stem, your reach automatically gets a little bit longer due to the head tube angle. The question then becomes how much can you drop the stack before you need to change the stem length. The actual answer surprised me.

Over the years I took notes on what I found to be comfortable stack and reach dimensions under a variety of riding conditions (Figure 1a). Not surprisingly, under easier riding conditions I tended to prefer a higher stack and shorter reach dimension. When I compared this to the fit dimensions produced by various stem lengths if I only altered spacer stack height (Note, this is only a exercise, most bikes only allow 30 mm of adjustment in stack height), I found one stem length covered a wide range of stack heights (Figure 1b). Moving from the tallest position, I would need to switch to a slightly longer stem fairly soon, but after than the longer stem would adequately cover a wide range of stack heights. As I dropped the stack even further my preferred reach shortened a bit relative to how the fit dimensions changed by reducing the stack, requiring a switch back to the original stem.

This exercise assumed a head tube angle of 72 degrees, a very common angle for endurance road bikes. This makes me suspect this is why road bike geometry has centered around this head tube angle (it is possible to calm steering response down or speed it it with other geometry tweaks so you have a little freedom in your choice of head tube angles).

Finally, as an aside some may ask why my stack height preferences varied so much. I was wondering the same thing so I plotted it against average power readings and was quite surprised at strength of power as a predictor (Figure 2). In short, under higher efforts you support more of your upper body through core activation, and we often use our upper body weight as a counter balance to pedal forces.

Figure 1 Figure 1. Preferred stack to reach dimensions under a variety of riding conditions (A) and (B) fit dimensions of provided by two stem lengths when stack height is changed by spacers. Solid blue line indicates polynomial regression line, with shading indicating the 95% confidence region.

Figure 2

Figure 2. Preferred stack dimensions under a variety of riding conditions and associated average power. Solid blue line indicates polynomial regression line, with shading indicating the 95% confidence region.

  • Rider_X this is a great in-depth analysis and it's awesome to know there are people out there collecting data like this. One question I have is that in figure 2 where you plot preferred stack to average power based on what type of riding, when you took these readings did you normalize the perceived effort and measure the change in out put based on position? Or am I reading this wrong and you are saying at those outputs that was the preferred reach? – Matt Solomon Apr 29 at 17:28
  • @MattSolomon Figure 2 was derived retrospectively. I kept a fit log over the past few years, noting position, activity, and whether I found it comfortable. I then computed the average wattage typical for these positions (e.g., over the last 5-10 rides). Some positions, like the touring bike, had only a hand full of direct power measurements. When I plotted it out I was surprised by how well it fell out on a parabolic curve, but made sense when you consider the bio-mechanics of needing a counter-weight to pedal force (note you can pull on the bars, but this gets tiring over time). – Rider_X Apr 29 at 17:44
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First remove the spacers since that is a little easier and less drastic of a modification. If you find that more comfortable and do not have any lower back pain then try doing a neg rise stem.

A longer stem will modify your reach which could also solve some fit issues if you are feeling more flexible.

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