The Bum Steer

[Mikkel]

I am about to deal to another sacred cow.
I too believed that countersteering worked because of gyroscopic precession.
However, about 18 months ago there was a thread in here that argued this quite vehemently (can't find it at the moment). Anyway, the whole thing was settled when someone quoted an article concerning a guy in the states a couple of years back, who built a bike that had counter-rotating wheels within the normal ones. This, of course, had the effect of cancelling out any gyroscopic effects at all.
He found that the bike handled pretty much as any bike does, i.e. that counter steering still worked and so gyroscopic forces (which do explain the phenomenon) are not the major reason for it.
The conclusion reached was that if (for example) one wishes to turn left and so counter steers to the right. The tyre contact patch moves right and the bike rolls about its own centre of mass and so leans to the left.
Further, for reasons that I can't remember, precession does make some contribution to standing the bike up again when exiting the corner. I presume it has something to do with acceleration.
I shall continue hunting for the thread that I mentioned.

If he had done his job of countering the angular momentum of the wheels properly I'm sure he'd have gotten a rather different result.

If you construct a bike with rotating counterweights that exactly out-balances the angular momentum you will find that the bike - at ALL speeds - have exactly as much balance as it has when stationary. I.e. not a whole lot TBQFH!
So if he claims that he found the bike to be riding quite like a normal bike he hasn't managed to cancel out the gyroscopic forces at all - as such his conclusions are utterly inconsequential!

[skelstar]

Right on all counts.
Except in bold...a lot of thinking must go into riding a bike. Until your technique becomes automatic...

So why don't they teach this 'bumsteer'/countersteer blah blah theory at BHST unless it was already automatic. First time I'd heard the counter-steer thing was probably a month or two after I'd started riding. So maybe 5000kms into my riding 'career'.

Quite honestly I think its just an opportunity for people to post big words.

[Ocean1]

I've been watching and reading all the countersteering threads of late and someone's comment "... if you're getting around corners, then you must be coutersteering, can't be done otherwise ..." has prompted me to post a counter-view on counter-steering.

Taking my name in vain dude?

The comment remains valid, unless you’re talking about a slow sweeper any “normal” traverse of a corner on a bike requires countersteering. I didn’t say that was the only input required.

And you’re right, the no-lean quick flick technique is dirt related. As you say, it puts the bike down and not the rider, exactly correct for your typical dirt bike at any sort of speed. The only time I’d do that on the Buell would be if the other requirement for that technique could be met: break the back loose. So, on the dirt, or gravel.

My reactions are still dirty, a thing that may one day get me into trouble if I let my reactions over-ride my brain. I’m very aware of that, but there’s a hell of a lot of people who ride very different types of bike regularly and quite successfully modify their style to suit.

Think about the dynamics of this. The counter-steer is using gyroscopic precession to apply a directional force from the application of opposing forces. Doing so unsettles the bikle, you are applying a side-load to the front tyre that doesn't need to be there. The Bum Steer on the other hand is simply letting the bike fall into a position to cut the corner in a totally natural way. All the forces are acting in unision and towards the apex of the corner. If it didn't work, racers wouldn't be using it (watch the MotoGP slow motions to see it in action).

No it’s not. Sure, gyroscopic precession stabilises the bike’s attitude in direct proportion to speed, and any steering force applied to the bars has to overcome that. And yes, any steering input produces lateral force at the contact patch, but that force isn’t derived from or related to gyroscopic precession. What’s more that lateral force isn’t high, only on the slickest surfaces have I ever had initial steering inputs result in a wash-out, it’s a far smaller traction issue than that required to navigate the corner itself.

Like almost all of us you would have tried cornering with no steering input, it’s not that difficult, just sluggish. I’m willing to bet you failed the first time, grabbed for the bars half way through. You probably noticed that it takes longer to initiate the turn, and that it takes far more “counterlean” to stand the bike up again than it did to get it to fall in.

The fact is that all countersteering is doing is placing the bike outside your body mass, exactly the same thing you achieve by leaning your body in, but far faster, and with more control. The reason it’s faster is because any lateral movement of your body weight alone produces an initial equal and opposite reaction in the bike, cancelling much of the effect.

Fast dudes do pre-lean, but they also give the bars a savage tweak to initiate the turn itself. So much so that sometimes they bend the bloody bars. I’m not suggesting taking inputs to such an extreme on the road, but it’s a mistake to suggest that racers use predominantly body lean to navigate corners.

One thing we agree on, a good rider knows all of the available inputs possible to change the attitude of a bike, and uses them. Whether he knows exactly which input produces which effect depends on how much time he’s spent experimenting. The dirt’s a great place to do that. The road ain’t.

I am about to deal to another sacred cow.
I too believed that countersteering worked because of gyroscopic precession.
However, about 18 months ago there was a thread in here that argued this quite vehemently (can't find it at the moment). Anyway, the whole thing was settled when someone quoted an article concerning a guy in the states a couple of years back, who built a bike that had counter-rotating wheels within the normal ones. This, of course, had the effect of cancelling out any gyroscopic effects at all.
He found that the bike handled pretty much as any bike does, i.e. that counter steering still worked and so gyroscopic forces (which do explain the phenomenon) are not the major reason for it.
The conclusion reached was that if (for example) one wishes to turn left and so counter steers to the right. The tyre contact patch moves right and the bike rolls about its own centre of mass and so leans to the left.
Further, for reasons that I can't remember, precession does make some contribution to standing the bike up again when exiting the corner. I presume it has something to do with acceleration.
I shall continue hunting for the thread that I mentioned.

Interesting. And surprisingly it agrees with the above.

Not sure what this is going to achieve really. You guys won't come to a consensus (you rarely do), the bike/you arrangement is still going to behave the same, you're still going to ride just as well, and the usual culprits will litter the discussion with sexual innuendo.

I find it pays not to think too hard about this kind of thing. I like to know when my tyres are up to temp, where my head is pointing and if the rubber is good. End of story.

If you asked a real natural racer exactly what forces apply to which control inputs he uses he probably couldn’t tell you. Some of us are not naturally that talented dude, we like to pick a process to pieces so we can understand it better. That, and we just like to argue.

[MSTRS:Me]

So why don't they teach this 'bumsteer'/countersteer blah blah theory at BHST unless it was already automatic. First time I'd heard the counter-steer thing was probably a month or two after I'd started riding. So maybe 5000kms into my riding 'career'.

Quite honestly I think its just an opportunity for people to post big words.

BHS is just that...Basic Handling. The push (or pull) method of steering is the most basic and effective way of changing a bike's direction of travel. Undeniable.
The other techniques can be learned with experience, experimenting or at an Advanced course.

[Ocean1]

Right on all counts.
Except in bold...a lot of thinking must go into riding a bike. Until your technique becomes automatic, that is. Then your brain is freed-up to consider stuff that hasn't reached you yet. This is why people who have ridden for years seldom bin.

Think it's usually the other way around. Most people don't think much about how they manage a pushbike when they first learn, it's only when it becomes automatic that they start to think "why".

[Badjelly]

I believe the countersteer that initiates the turn is a bad substitute for poor body position and technique. Hence "The Bum Steer". A turn that is initiated by loading up the "inside bum cheek" does not need counter steering input. Before the howls of Indignation and Outrage gather volume, I do agree that you can use small countersteering adjustments. I just don't agree that it is the only way to initiatre a turn ... back to The Bum Steer.

Interesting stuff, Grub. You talk about Casey Stoner, but Casey and his MotoGP pals go through corners hanging off the inside of the bike. I don't see people do that on the road, certainly not so much. I (think) I go through corners with my torso pretty much on the axis of the bike, and my head tilted outwards to keep it roughly horizontal. Are you suggesting I should move my body to the inside?

I agree that riders can and should change their weight distribution on the bike as they enter corners, but I suspect that it's the handlebar inputs that actually initiate the turn.

Like I said, interesting stuff...

[Badjelly]

Most people don't think much about how they manage a pushbike when they first learn, it's only when it becomes automatic that they start to think "why".

And some never think why, in fact they actively resist it. Which is fair enough, but some people (I'm one) like to analyse what they do.

[MSTRS:Me]

Think it's usually the other way around. Most people don't think much about how they manage a pushbike when they first learn, it's only when it becomes automatic that they start to think "why".

Knowing 'why' may require thinking, but in all likelihood only as much thinking as is needed to track down someone who can tell you why. A lot of us have no real interest in the why, just to know it works is enough. And I stand by what I said...the less 'thinking' one has to do about the mechanics of guiding one's machine, the better able one is to plan ahead. Therefore avoiding hazards more easily.

[Ocean1]

If he had done his job of countering the angular momentum of the wheels properly I'm sure he'd have gotten a rather different result.

If you construct a bike with rotating counterweights that exactly out-balances the angular momentum you will find that the bike - at ALL speeds - have exactly as much balance as it has when stationary. I.e. not a whole lot TBQFH!
So if he claims that he found the bike to be riding quite like a normal bike he hasn't managed to cancel out the gyroscopic forces at all - as such his conclusions are utterly inconsequential!

Not true, there's another huge difference between a stationary and moving bike when it come to possible control inputs. YOU"RE MOVING, any change in steering input is effective because it's possible to change the contact patch.

[Ocean1]

Knowing 'why' may require thinking, but in all likelihood only as much thinking as is needed to track down someone you can tell you why. A lot of us have no real interest in the why, just to know it works is enough. And I stand by what I said...the less 'thinking' one has to do about the mechanics of guiding one's machine, the better able one is to plan ahead. Therefore avoiding hazards more easily.

For me, when riding, (rather than "experimenting") it's two completely different exercises. So yeah, the execution does not require knowledge, we're saying the same thing.

[Badjelly]

Quite honestly I think its just an opportunity for people to post big words.

I disagree, though I can see why you would think that. It's a bit like wine criticism: all that "hint of lychees" and "soft tannins with a lingering finish" stuff sounds like waffle, and to some extent it is, but bugger me, some wines really do taste like that!

Ocean1's post a few messages back has clarified several things for me and is, in my opinion, a clear demonstration that it's not just big words.

[Mikkel]

Not true, there's another huge difference between a stationary and moving bike when it come to possible control inputs. YOU"RE MOVING, any change in steering input is effective because it's possible to change the contact patch.

Either you didn't read or you didn't understand my post. If it's the latter case I could suggest starting out here: Classical Mechanics.

[MSTRS:Me]

... So yeah, the execution does not require knowledge, we're saying the same thing.

Hope so...coming from the angle of a relative newby, they are constantly and consciously brain-guiding their machine. How and why it works is not an issue for them at that point, just the fact that it does work. However, it doesn't happen 'automatically' until a sufficient amount of practice has occurred, hence my take on the 'thinking' bit. Once the inputs are happening more-or-less without conscious thought, then the rider may start to think 'why does it work?'. Doing this at this point is a good thing, because the rider is then in a position to make a quantum leap in their abilities to react to various situations that present. Experienced riders are not necessarily 'fast' but will be better equipped on the roads to survive. And in all likelihood be faster on average through being consistent.

[Ocean1]

Either you didn't read or you didn't understand my post. If it's the latter case I could suggest starting out here: Classical Mechanics.

Oh I'm sure you can think of a third alternative dude.

[Mikkel]

Oh I'm sure you can think of a third alternative dude.

You're pulling my leg. I see