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A short bike stem is common, and desirable, on MTBs (increased maneuverability) and a long bike stem is common on road bikes (lower body position), but is an ultra-short bike stem downright dangerous on a road bike? If not downright unsafe, is it safe with a small group riding in single file, but becomes unsafe for someone riding with a crowd?

Context of the question: A road bike of a given size will typically last a growing youth one season (up to 6 months) before it becomes necessary to replace it with a larger bike. One way to somewhat reduce the rhythm of replacement is to have a collection of stems (40mm, 60mm, 80mm, 100mm, 120mm), and to use one after the other. (This can be combined by buying the bike slightly ahead of time, and only allowing the child to ride when they clear the top tube.)

In case it matters, this would be the youth's only road bike. I appreciate that there are some motor skills that could get confused if one is switching between two bike frames. The magnitude of the "input" for a long stem, if done unconsciously (reflexively) could lead to excessive steering on a bike with a short stem.

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    Switching between 2 road frames with very different handling isn't a big deal anyway. You might not want to go straight into a bunch ride (though you're not normally manoeuvring much then anyway), but 5 minutes is enough to adapt for any riding conditions. I do this quite often, riding home on my tourer then swapping to my road bike. A different and sharper biting point on the brakes is more noticeable anyway. (Addressing the "not the question" bit)
    – Chris H
    Commented Apr 30 at 11:03
  • @ChrisH Yes indeed. One of the notable cursing scenarios on a bike is when I switch from hydraulic to rim brakes and find that I need a substantially longer braking distance. About the question: what is the shortest road bike stem you consider usable?
    – Sam7919
    Commented Apr 30 at 11:11
  • I'm too long to answer that question. I haven't swapped from the stock stems on any of my bikes, but wouldn't go very short even if I did
    – Chris H
    Commented Apr 30 at 12:43

2 Answers 2

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Your leverage on the steering is proportional to the distance from your hand to the stem quill. The reach of the stem will not affect that distance very much.

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    It really is that simple; isn't it? The hands-to-steerer connection is rigid, and so its shape is of no significance. The only factor is that the hand-to-steerer-to-hand angle becomes more obtuse when the stem is shorter. I'm not clear on how or why that would matter, but otherwise one shouldn't shy away from using whichever stem length leads to better ergonomics (/bike fit).
    – Sam7919
    Commented Apr 30 at 16:43
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I have never personally fitted a stem shorter than 60mm to a road bike BUT they are manufactured in this size, and ride fine. I don't see why you shouldn't test 50mm, given this is not an expensive part. Each person adapts to the handling of their own bike and gets used to it relatively quickly. Then the "danger" might be switching to another bike that does not handle as expected, after being used to so short a stem.

Answer is, it's not a problem going short, unless it's obviously a problem when riding. Each rider and type of bike (and the reach of the handlebar itself!) is different, so there is no universal answer.

I think you shouldn't ignore handlebar reach and width when you are considering this. Handlebars can vary in reach by cms in some cases!

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