Some thoughts on motorcycle stability.

Stability in general and motorcycle stability in particular is one of those subjects that is so little understood that pretty well every misinterpretation of what's going on usually ends up as gospel. According to Roadcraft, “When you corner, your machine loses stability” which at first glance might appear to be a perfectly valid statement, but sadly it’s not entirely true and here’s why.

First of all, it might help to understand what stability or perhaps the lack of it, actually is. There are broadly two types of stability, static and dynamic and it’s quite important to understand the subtle difference between the two.

Simply put, if something has static stability and you disturb it, it will tend to try and return to its original state of equilibrium, but just because it is statically stable doesn't mean that it will ever get there. It may overshoot by further and further each time until catastrophic failure. For something to be dynamically stable it must actually be able to return to its state of equilibrium. It must therefore be statically stable in the first place otherwise it wouldn't even try to return at all. So while something that is dynamically stable may still overshoot, the overshoots will get smaller each time till there is nothing to correct. So you can end up with various combinations of the above

Statically unstable - gets disturbed and just disappears off somewhere. A good example of this is trying to balance a marble on a football. You can be certain that the marble will simply roll off the instant you let it go.

Statically stable + Dynamically unstable - gets disturbed, disappears off somewhere, but will keep coming back before disappearing again. A great example of this is a classic tankslapper when the front wheel shakes violently to left and right getting worse and worse with each movement.

Statically and Dynamically stable - gets disturbed but in time will return to its original position. A suitable example of this is putting the marble we used before into a fruit bowl. If you roll it up the side of the bowl and let it go, it will return to the centre, overshoot a bit and return to the centre and so on until it comes to a rest.

Now we know what stability is, let us see how it relates to our motorcycle. All bikes can exist in one of three states, moving, stationary and leaning against something (side stand, wall or the ground). As you might expect, the type of stability in each case is different. When the bike is stationary all we have to do to find out what sort of stability it has is to get off it and let it go. It then exhibits the classic properties of static instability in that it falls over with a mighty crash. Put it on its stand however and when we let it go it stays there, an example of static + dynamic stability.

It’s when the bike is moving that it starts to get interesting and this is where most of the confusion about stability arises.

The instant we drop the clutch and move away, we can happily put our feet on the footrests and enjoy the ride. Unless we are Dougie Lampkin however, we would find it next to impossible to keep our feet up whilst the bike was stationary. It is obvious then that the type of stability that our bike exhibits changes from being statically unstable to statically and dynamically stable as we open the throttle and move off.

This static plus dynamic stability is generated in a number of ways. Firstly our forward movement invokes Newton’s first law of motion in that something at rest wants to stay at rest and something moving wants to stay moving in the same direction, unless acted on by an outside force. Once we get the mass of the bike moving forward, it wants to stay moving forward and not to the side. Secondly, our wheels exhibit something called gyroscopic rigidity in that once they are spinning they resist being moved in any direction other than the one they are currently taking. Thirdly, the bikes steering geometry is set up so that if the bike leans to the left, it displaces the centre of gravity also to the left. This in turn sets up a steering action to the left which brings the centre of gravity back between the contact points of both wheels, thus restoring stability. The final piece of the jigsaw is how the rider subconsciously uses control inputs and body weight to keep the bike on its chosen path. For most of us, these control inputs were not learnt on a motorbike, but were probably discovered many years earlier, when we first wobbled off on our push bikes.

So if our bikes are stable when they are moving, is there any time when they are unstable? We touched on this a little earlier when we learnt how the steering geometry of the bike (rake, trail etc) acts to restore stability if the C of G becomes displaced from being between the tyre contact patches. At this crucial moment of instability, our bike is beginning to fall over, just like it would when it was stationary. Other words we can use to describe this falling motion are leaning and banking, the essential elements of cornering.

The crucial point here is that in order for us to steer our bikes, we must make the bike temporarily unstable, otherwise it would not lean and no lean means no turn.

We usually get our bikes into an unstable state by countersteering which displaces the C of G to one side of the bike. This unstable state persists until something acts to restore stability (if it didn’t our bikes would just crash to the ground every time we wanted to go round a corner). This restorative force comes from the steering geometry, the actions of the tyres on the road and the cone or camber steering force of the wheels all working together to make our bikes want to move in the direction of lean, cornering in other words.

These restorative forces continue to act until stability is regained when the C of G is once again immediately between the contact patches of the tyres. At this point, our bikes are banked over and cornering, but now they exhibit exactly the same amount of static plus dynamic stability as they did when they were travelling upright in a straight line. This is called the “steady state” lean angle and with an unlimited amount of petrol and with unlimited tyre life, our bikes could whizz round and round like this for ever.

So Roadcraft is sort of half right when it says “When you corner, your machine loses stability” but what it should say is “In order to go round a corner, your bike must first become temporarily unstable so that it starts to fall (lean) in the direction of the turn. Stability is regained once the steady state bank angle has been achieved and the cornering forces have restored the centre of gravity directly between the tyre contact patches.”

Stability is a mightily complex subject and I can hardly do it justice in this little Blog entry, but if you do want to know more about stability then I must recommend the book by Tony Foale called Motorcycle Handling and Chassis design. You can buy it online at http://www.tonyfoale.com/ and although it is quite expensive, you will find a wealth of information within its pages about how your bike works.

A Total Control Riding Clinic will show you how to manage the moment of instability to make it work for you so that you can corner better and safer than you might at the moment. We still have some places left on the upcoming courses, so why not do yourself a favour and get yourself booked in?

The Laws of Physics

"You cannae change the laws of physics Cap'n" as Engineer Scott famously said in Star Trek and although it was a science fiction programme, the statement is most certainly fact and these same laws play a massive role in keeping us safe on our bikes.

In conversation with a retired motorcycle Policeman the other day, I enquired as to why all bike cops rode around bolt upright in the saddle and astonishingly the answer is that it "looks professional". I would have expected him to have told me that the upright style brings many benefits, but no, it is the look that is important. I suppose the thinking goes that the Police are considered to be good riders and can hustle along well enough sitting bolt upright, therefore riders that hang off like their favourite racers, will try and ride like their favourite racers (fast) and that of course must be discouraged.

Although it may look professional, to certain eyes, the bolt upright riding style has a particular and deadly disadvantage that outweighs any of its advantages.

The picture with this blog is of a chimney in mid collapse. Notice that the top of the chimney has broken away from the main body and has adopted a much steeper angle than the rest of it. This is a wonderful illustration of Newton's First Law also known as the Law of Inertia, which states that an object at rest tends to stay at rest and that an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. The chimney in the picture has started to fall because the demolition contractor has knocked its feet out from under it, thus rendering it unstable. As it falls it tries to accelerate the entire mass of the chimney, but there is a bit of a problem in that the top of the chimney has to accelerate much, much faster than the bottom of it. The first bit of Newtons law states that stuff wants to stay at rest, so the brick built chimney snaps in the middle as the inertia of the top resists the acceleration forces coming up from the base. The only way to stop the chimney from snapping is to lower it at a rate that allowed all the components to accelerate together. This rate would be much slower than that due to gravity alone and would require some sort of external counter force to be applied. Watching videos of concrete, rather than brick chimneys being demolished shows that because they cannot snap due to their massive strength they fall very, very slowly once their foundations have been blasted away.

This leads us straight to the problem with the bolt upright riding style in that a bike is like the falling chimney. When we lean the bike over to negotiate a corner, the faster we lean it, the quicker it will turn and the slower we lean it, the slower it will turn. If we try to lean it quickly, then Newtons law of inertia means that our very heavy head wants to stay where it is and like the top of the brick chimney in the picture, it tends to get left behind. If we lean it at a rate that allows us to keep our head in line with the rest of the bike, then like the concrete chimney, it has to lean very slowly indeed.

This wouldn't matter so much but for the fact that leaning a bike slowly takes up a fair amount of road in going from upright to leaned over. To counter this problem, we have to start the leaning process early and the earlier we start leaning the bike the wider we will run at the exit of the corner. To counter running wide at the exit, we have to lean the bike over more and run the risk of dragging hard parts or running out of tyre which usually means we run wide.

Running wide on rural bends is the biggest killer of riders in this country, yet the Police use and encourage a riding style that practically guarantees that riders will run wide and kill themselves. It hardly makes any sense.

As it is impossible to change the laws of physics as Scotty once told us, we will have to change something else to make them work in our favour rather than working against us.

Luckily there is a solution to the problem and it's called the Total Control riding style which we are hoping will eventually become the default professional style for riders of all types. After all, you cannae change the laws of physics!

Get yourself booked onto a course today and learn the secrets of the Total Control riding style, you never know, it might well save your life.

The "killer" question?

So who, or what is the biggest killer of motorcycle riders? Let's take a look at the usual suspects to see if we can find the truth.

Surely the biggest killer must be the idiots in cars, not looking properly and wiping us out at junctions? No, although they do have an impressive kill rate, they are not the biggest killer.

What about potholes then? There is a lot in the news about these horrid things, they must be at number 1? No, in fact the victim count from potholes is remarkably small considering how many of them are out there.

Must be diesel spills, due to the carelessness of many truck drivers? Once again a resounding no, although there are a lot of unplanned dismounts due to diesel and other surface contaminants, the morgues are not bursting at the seams because of it.

Ahh, speeding, that must be it. The Government tells us that speed kills, so that must be the answer? It's certainly the easy answer, but it is not the right answer. Breaking the speed limit might kill a few of us, but again, it is not the biggest killer.

To find the correct answer, we must first find the killing ground where most of us end up dying and work out the solution from there. According to all the information gathered from many fatal accidents over the years, it is the rural left hand bend where most of the carnage takes place, not one particular bend you understand, but any and all of them. To add to the horror, in most of the fatal accidents on this type of bend, there was nobody else involved at the beginning of the accident, but there usually is some kind of third party involvement at the end of it.

Averaging out all these accidents, they all seem to follow a sickeningly inevitable course. Our victim is happily bowling along the road, enjoying all the sensations that riding a motorcycle brings when a corner hoves into view. There is nothing unusual in this, as our victim has already negotiated dozens of corners just like this one on the ride so far, so why should this one need special consideration? Trouble is, our rider has made a serious mistake on the approach to the corner because it is most definitely NOT like all the corners that have gone before. Maybe it tightens, or perhaps there is a huge patch of gravel on the surface, or even a tractor parked up just out of sight round the corner. Whatever it is that makes this corner different to all the rest, it is going to have a profound effect on our rider when they suddenly realise it IS different.

What happens immediately after this moment of realisation, will seal our rider's fate and it is THIS moment that is the answer to the "killer question".

The action a rider takes at the moment of realisation of his mistake is by far and away the biggest killer.

Although many riders might make similar mistakes, the mistake does not seal the rider's fate. Fixing mistakes that riders make will certainly help to reduce the carnage, but there are so many mistakes to be made that you could not possibly fix them all.

Much better to concentrate on the moment of realisation, because you will get one of those, irrespective of the mistake you may have made.

That's the big difference between Total Control and other advanced riding courses. Other courses will try and show you how to avoid making mistakes, whilst Total Control will show you what happens at the moment of realisation and what you should do about it.

We call this Superadvanced riding, you should try it, it might well save your life.

Heart of England Bike Show

This litle show organised by Warwickshire Council, will be at the Heritage Motor Centre near Gaydon in Warwickshire this Sunday and we will be there to promote Total Control.

Am just about to go and set up the stand, and even though the weather is a bit murky today, all being well it will be much better tomorrow.

There will be lots of training organisations attending such as IAM and Bikesafe, so it will be a good opportunity to introduce Total Control to them as well as all the visitors. If you fancy a nice ride out into the country, why not come along to Gaydon and say hello.

MotoGP from Quatar

Just finished a televisual feast of motorcycling. Superbikes from Valencia and MotoGP from Quatar, fantastic, I’m in seventh heaven. Can’t help but wonder what would happen if you put Valentino on the worst bike in a Club race, would he be up the front, or would he trail along at the back making up the numbers? I somehow think that he would be somewhere near the front leaving everybody to marvel at his riding ability. Just goes to show, I suppose, that it’s not the bike, but the rider that makes the biggest difference.

MotoGP Season

Sunday 11^thof April, it’s the start of the MotoGP season, the sun is shining, it’s nice and warm and I’m out on my bike enjoying a nice long ride in the country. Whizz, whizz, a couple of sports bikes blast past me on the straight. Knee out, bum out as they peel into the corner, no doubt thinking that they really showed the bloke on the GS how to ride fast. Halfway through the corner and I’m wondering why these speed merchants are going so slowly. Never mind, I’m happy enough just sitting there as the corner unfolds to reveal a nice long straight. The bloke at the back can’t resist a quick peek into his mirrors to see how much distance they have put between themselves and the lumbering GS and rather than seeing a rapidly receding dot, he gets the full blast of my gimlet eye staring right back at him. This is his cue to twist the throttle some more and he and his mate accelerate away.

On for a few miles and follow a Harley through a very pretty village. Nasty sharp corner right in the middle, but easy enough to negotiate when you know what you’re doing. This rider obviously doesn’t as he wobbles round the corner demonstrating a perfect example of a thruppeny bit line. At one point I thought he was going to come to a complete halt, but he managed to find some reserves of skill somewhere and eventually proceeded on his way.

Corners are like that and as these riders clearly demonstrated, they can be either too fast or too slow for the skills they have to hand. Thinking about it, the Harley probably represented an investment of about twelve grand and the R1’s not much less than that. I can’t for the life of me understand why someone would spend that much on a bike and not be bothered to learn how to ride it properly.