Tyre help please

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531colin
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Re: Tyre help please

Post by 531colin »

Roadster wrote:Wider and hence heavier tyres will make the bike less wobbly because they add mass to the rotating rims of the wheels: this increases their gyroscopic effect which keeps the bike upright when moving forward.

However, the effect increases with speed and doesn't really help stability until bike and rider are reasonably underway. After that, even the narrowest and lightest tyres will have significant gyroscopic effect, so you might choose wider, heavier tyres for other reasons (like comfort) but not merely for the sake of improved stability.


Studies have shown that even in "bicycles" where the gyroscopic effect of the (front) wheel is cancelled out mechanically by a contra-rotating wheel (see http://science.sciencemag.org/content/332/6027/339?sid=c68a2457-3d07-4a97-9912-b8a73ab69376 amongst others) the bicycle is self-stable when pushed and released, so I wonder in what context the gyroscopic effect might be considered "significant"...?

I repeat, neither the gyroscopic effect of a wheel weighing a few pounds, or the self-stability of a bicycle weighing a few tens of pounds, will balance a rider weighing several stones.
Brucey
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Re: Tyre help please

Post by Brucey »

I think that all these things add up, and the human factor complicates matters.

For example adults who ride a Brompton (or similar) for the first time almost invariably wobble like fury. The trail usually isn't wildly different from larger wheeled bikes that don't cause such wobbling, so maybe the lack of gyro effect (or simply the mass in the steered part -which is BTW unavoidably doubled vs 'normal' in the counter-rotating flywheel experiment- ) is making the difference.

BTW I have found that simply increasing the width of the tyre (whilst keeping the tyre construction the same) greatly alters the steering feel. I think that the way the contact patch moves from side to side when the bike leans is exaggerated with the wider tyre and this alters the steering feel. This is to some extent ameliorated by lower tyre pressures but if you go too far the bike starts to feel horrible e.g. when you ride out of the saddle. For this reason I don't think I could never run a pressure like 35psi in a 37mm front for example, as others report they do.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Roadster
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Re: Tyre help please

Post by Roadster »

531colin wrote:I repeat, neither the gyroscopic effect of a wheel weighing a few pounds, or the self-stability of a bicycle weighing a few tens of pounds, will balance a rider weighing several stones.

You are stating the obvious and I in turn repeat, I didn't say that they would. I simply said that it would make the bike more stable, not totally stable, and only then when both it and its rider had achieved reasonable speed. I only mentioned the rider because a bike without one was in this case irrelevant. Nonetheless, I made no reference to the rider's wobbliness or lack thereof, but confined myself solely to the bike's.

I further repeat, at no time have I suggested that "the gyroscopic effect of a wheel weighing a few pounds, or the self-stability of a bicycle weighing a few tens of pounds, will balance a rider weighing several stones": those are your words, not mine, and you're just putting them into my mouth in order to create an opportunity to pour scorn on them. And what's that all about, then? Well, the usual patronizing crap, I suppose :roll: : it's all about trying to make yourself look big by making others look small, the main endeavour of egotists in all walks of life.
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531colin
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Location: North Yorkshire

Re: Tyre help please

Post by 531colin »

Roadster wrote:
531colin wrote:I repeat, neither the gyroscopic effect of a wheel weighing a few pounds, or the self-stability of a bicycle weighing a few tens of pounds, will balance a rider weighing several stones.

You are stating the obvious and I in turn repeat, I didn't say that they would. I simply said that it would make the bike more stable, not totally stable, and only then when both it and its rider had achieved reasonable speed. I only mentioned the rider because a bike without one was in this case irrelevant. Nonetheless, I made no reference to the rider's wobbliness or lack thereof, but confined myself solely to the bike's.

I further repeat, at no time have I suggested that "the gyroscopic effect of a wheel weighing a few pounds, or the self-stability of a bicycle weighing a few tens of pounds, will balance a rider weighing several stones": those are your words, not mine, and you're just putting them into my mouth in order to create an opportunity to pour scorn on them. And what's that all about, then? Well, the usual patronizing crap, I suppose :roll: : it's all about trying to make yourself look big by making others look small, the main endeavour of egotists in all walks of life.


That little outburst says much more about you than about me.
Roadster
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Joined: 26 Jul 2016, 2:12pm
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Re: Tyre help please

Post by Roadster »

Perhaps, but what it says is that I don't like being addressed as though I were a child or a simpleton by someone who evidently has no manners and no respect.
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531colin
Posts: 16083
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Tyre help please

Post by 531colin »

Brucey wrote:I think that all these things add up, and the human factor complicates matters.

For example adults who ride a Brompton (or similar) for the first time almost invariably wobble like fury. The trail usually isn't wildly different from larger wheeled bikes that don't cause such wobbling, so maybe the lack of gyro effect (or simply the mass in the steered part -which is BTW unavoidably doubled vs 'normal' in the counter-rotating flywheel experiment- ) is making the difference.

BTW I have found that simply increasing the width of the tyre (whilst keeping the tyre construction the same) greatly alters the steering feel. I think that the way the contact patch moves from side to side when the bike leans is exaggerated with the wider tyre and this alters the steering feel. This is to some extent ameliorated by lower tyre pressures but if you go too far the bike starts to feel horrible e.g. when you ride out of the saddle. For this reason I don't think I could never run a pressure like 35psi in a 37mm front for example, as others report they do.

cheers


Isn't it?
Dan Joyce's review of a couple of folders in Aug/Sept (current) CTC magazine has Brompton trail at 27mm.
I find Bromptons horribly wobbly. I'll try to get a go on a Birdy, Dan has their trail at 65mm
Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Tyre help please

Post by Brucey »

the trail is low, but not much lower than some large-wheeled bikes which (IME) do not make their riders wobble in quite the same way.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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