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Gyroscopic effect of deeper front wheels?

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Gyroscopic effect of deeper front wheels?

Old 07-16-22, 12:22 AM
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tFUnK
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Gyroscopic effect of deeper front wheels?

When I first went from a 38mm to a 60mm front wheel a few years ago, I recall feeling that the steering became heavy. At the time I attributed it to the aerodynamics (catching more wind). I switched back to the 38mm and that was that.

Today on a different bike I switched out my 32mm front to a 50mm front and felt the steering become noticeably heavier. But this was just a driveway spin at slow speeds, so I'm now thinking it's the added mass concentrated at the rim is introducing a gyroscopic effect. Does my physics check out? Anyone else notice this when going to a deeper front wheel?
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Old 07-16-22, 03:40 AM
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Polaris OBark
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I've never tried a deep rim, but yes, your physics checks out. If you want to further test your hypothesis, fill your tube (or tire) with water. The result should be dramatic.
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Old 07-16-22, 12:26 PM
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Originally Posted by tFUnK View Post
Today on a different bike I switched out my 32mm front to a 50mm front and felt the steering become noticeably heavier. But this was just a driveway spin at slow speeds, so I'm now thinking it's the added mass concentrated at the rim is introducing a gyroscopic effect. Does my physics check out? Anyone else notice this when going to a deeper front wheel?
How fast was your driveway spin?

You can check this by holding your front wheel in the air and turning the bars left and right, then spinning it as fast as you can and turning the bars left and right. I can spin my front wheel with my finger up to 3 or 4 revolutions per second. If the wheel has a circumference of 2m, that's something like 6 to 8 m/s, or maybe in the 15mph range, give or take. While it's spinning, is turning the bars easier, harder, or about the same as the wheel wasn't spinning? Is it easier, harder, or about the same as when you were in your driveway "at slow speed"?
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Old 07-16-22, 08:32 PM
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I understand stand the principle of a gyroscope. Keep in mind a smaller tire will spin faster then a large one at the same speed thereby increasing the gryo effect. Which is one reason I believe it has much less effect on a bikes steering then the bikes geometry, like head tube angle, fork rake and trail. My comfort bike has twitchy steering and it doesen't get better with speed even with heavy 2" wide tires. I swapped bikes with a friend's cruiser bike that was much more stable thanks to a more relaxed geometry.

It should be noted that a taller tire will change the geometry slightly, and that might have an effect on steering when combined with more rubber on the road with a wider tire.

Last edited by xroadcharlie; 07-16-22 at 08:49 PM.
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Old 07-16-22, 10:48 PM
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Good discussion here. I'm glad my physics checks out. Just surprised at how noticeable the effect was going from a 32mm or 38 mm front wheel to a 50mm or 60mm front wheel. When I say the steering felt heavy, I mean I actually felt what I can only describe as resistance, not that the steering was too slow. I am curious if anyone riding 50mm+ front wheels experienced anything similar? I imagine the pro peloton routinely ride 40-60mm fronts, and it's obviously no issue for them. And yes, I am conflating wheel depth with mass here, but I think we can accept that the two are correlated.
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Old 07-16-22, 11:41 PM
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The two are definitely related. The force input to a gyroscope exits the gyroscope 90degrees away. Thats why when you turn your bars at approxamately horizontal, the bike leans one way or the other (perpendicular to the direction of rotation.) The more mass/higher the rotation, the more pronounced the effect, the heavier the resistance to input.

"Counter steering" is the conventional term for utilizing this emergent property.

Last edited by base2; 07-16-22 at 11:53 PM.
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Old 07-17-22, 06:34 PM
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Not so fast. If your deep section rims are heavier than the ones you replaced, then you'll probably get more of a gyroscopic effect. But as some of that mass is at a smaller radial distance from the hub, it's gyroscopic effect is not as pronounced than would be the case if they weight were at the circumference. If you were to replace those original rims with rims with the same weight as your deep sectin set, but which had the same profile as the original (i.e., a cheaper set of wheels), the gyroscopic effect would be greater than the deep section wheels.

In fewer words, the deep section wheels only add a gyroscopic effect insofar as they might be heavier than the shallow section wheels. Further, heavy shallow section wheels have the greatest gyroscopic effect because of their mass distribution.

I think the "heavy" steering of deep section wheels is more likely owing to the aerodynamic effects of moving more air around as the wheels rotate to the side, rather than owing to a gyroscopic effect.
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