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When you read such post as this one https://bikeinsights.com/cyclopedia/trail you will learn how offset and head tube angle affects steering.

But I wonder about those parameters in "reverse" -- given trail (constant) when we change offset and angle what is the difference in steering?

For example: 760 mm wheels, one bike A with angle 78 degrees and offset 0 mm gives 80.8 trail, while another one B with angle 69 degrees and 61 offset gives 80.5 mm trail, so pretty close (let's call them even).

The difference of course is in the flop, for A it is 16.4mm, for B 26.9mm.

What would be the difference in actual steering? I am especially interested in such factor as self-correcting.

Equations: https://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry#Wheel_flop

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  • What’s the context here? Technical trails with a suspension rock? Road racing?
    – Paul H
    Jan 13, 2023 at 5:09
  • And what is the definition of flop?
    – ojs
    Jan 13, 2023 at 11:11
  • It's even more complex than that. Where the weight ends up can change a bike's self correction / flop / handling even more than a change in HTA, rake. (This is particularly noticeable in recumbent bikes, where moving a rider forward or backward an inch can change handling characteristics.) The good news is that riders can get used to just about anything in the realm of "normal" very quickly.
    – user36575
    Jan 13, 2023 at 13:05
  • @PaulH, Rigid fork, since suspension would add additional factor of sagging. Context is riding straight, I am not asking about particular race/event/trip but the nature of the bike. I selected those parameters to have constant trail so the variables would be only offset and angle (and as a derivative -- flop). Jan 13, 2023 at 14:36
  • I'll say this, as mountain bikes have gotten longer and slacker, they are increasingly spec'd with low offset forks. Those forks seems to provide a very acceptable balance of high-speed stability and low-speed maneuverability. IME, a modern bike with a 160 mm fork and a 64º HTA navigates tight switchbacks better than the 120 mm, 70º HTA bikes of ten years ago.
    – Paul H
    Jan 13, 2023 at 15:28

1 Answer 1

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As I always understood it, trail is the tendency of a bicycle to straighten itself out (to self-steer the front wheel to counteract a course deviation), and flop is a measurement of "turn-in," that is, the ease with which it can be steered off-course. But this article goes into a lot of detail explaining that A) flop is often defined incorrectly, and B) we don't have a good grasp of what (if anything) flop represents even when defined correctly.

I am reminded that bike stability has been studied in an academic setting for decades, and still isn't fully understood.

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