Romancing
the Stones
I wrote this article back in 1997. In the
following year I fell off four times, three of them gravel related. I rediscovered the article when my home
computer was rendered unusable by virus and pop up infections and I set about
recovering old files before having it totally rebuilt. It is untouched, but has stood the test of
time. …Ed.
Gravel on corners is the bane of all motorcyclists, some more than others. There you are, flying along, no gravel for the last 200 corners, minding your own business, when, bang, there it is, gravel! You grab a big handful of brakes, your life flashes before your eyes, you crash, or you don’t. Familiar scenario?
Understanding Gravel
Gravel likes to congregate. Leading up to corners it is most often in strips. Car tyres throw gravel left and right. A “new” surface, which may consist of wet tar and gravel sprinkled over it (as distinct from “hot-mix”), is cheap and fast. Victorian councils specialise in this type of road making technique. The finished surface relies on cars to pound the stones into the tar and dispense the excess stones. (Who needs a roller when cars will do the work for you?) So the excess stones end up in strips up the middle of the road and at the side of the road. But cars take all sorts of lines through corners, so often you may find there is little or no gravel in a corner. It has all been thrown outwards and off the road. The gravel may not be as bad as you first thought!
Gravel is always on the move. Gravel associated with pot-hole repair tends to scatter. Rain washes it downhill, cars throw it here and there. Fresh gravel is the worst because it hasn’t had time to travel far, to congregate.
Why does a bike fall down?
Gravity. The earth sucks. But when we go round a corner we use gravity to “pull” us around the corner, so gravity is not all bad. The friction between the tyre and the road transmits this pulling force. Ride through gravel and the friction between the tyre and the road is reduced to almost nothing and the bike starts falling down with an acceleration of gravity which is 9.8 meters per second, per second. For example if you drop a stone, it will fall due to gravity 9.8 m in the first second, 18.6 m (9.8 + 9.8) in the second second, 28.4 m (9.8 + 9.8 + 9.8) in the 3rd second, etc. So it certainly doesn’t take long to fall from a seated position on a bike to the ground - much less than a second. Hence, “I was on the ground before I knew it”. Absolutely true.
But this is a worst case scenario - wall to wall gravel or sand or oil or water or ice. So lets assume the gravel has congregated which gives us a fighting chance, but not if the wheels lock! Spinning wheels have inertia.
Physics and Inertia
Inertia is a function of the mass of the wheel (disks, etc), the diameter of the wheel, and the speed at which it is spinning. The bigger the diameter for the same mass, the more inertia. The faster a wheel spins, the more inertia. We interpret this inertia as stability. We like stability because it offers security. We can trust the bike to behave in an expected and non-threatening way over bumps, and at speed. The downside of stability is that it makes a bike harder to steer. We like to be able to change directions quickly and without much physical effort. Hence there is always a compromise between the stability and ease of steering. Current thinking is that 17” front wheel is the best compromise. A 16” wheel is inherently less stable (ie has less inertia, is more prone to “bump” steer) than a 19” wheel, but steers quicker!
One of
Grabbing a big handful of brakes is about the worst thing you can do when trying to negotiate gravel. The wheel is much more likely to lock up and hence lose all gyroscopic (inertia) stability. Gravity runs amok. With the wheels spinning normal steering functions have a chance of working. You may have time to control the slide with “full opposite lock”. If you can brake hard in a straight line between gravel strips, then tip in, brakes completely released (to avoid usually front wheel lockup) your chances are optimised. The front (and rear) wheels will maintain gyroscopic stability and hopefully “step” and grip. The bike will feel like it moved about a metre (in reality a few cms) and you will live to abuse the local council.
The Fear
Adrenalin is a killer. It is triggered by the brain when we panic. It is one of those hormones that prepares the muscles for flight - the running away type flight. A nasty side effect is that it causes your hand to make a fist! Which is good if you want to brake, and terrible if you don’t. Meeting gravel mid-corner you don’t want to brake, but The Fear strikes and you automatically brake. Mongrel! It takes practice to control your hand, forcing it not to close. Buggered if I know how you practice it, other than scaring yourself silly, repeatedly! It worked for me.
Funnily enough, slow reactions will often get you out of trouble - the drama has passed before you have had time to react to it! There is hope for us old people yet!
The bottom line is: learn to control the adrenalin rush. Don’t panic. Physically fight your way through it.
Read the Road Surface Conditions -
Experience
Road signs are extremely important. The reason there is a bit of armco on one corner on the Reefton Spur is because 27,000 people have crashed there and the council finally got round to putting up a sign and a barrier! This sort of logic applies to any road sign. They cost money in installation and maintenance. They are there because something bad happened there.
There are a million tell-tale signs about road surface conditions which we absorb as we ride. Over the years this becomes our store of experience. Experience counts. In a way, experience is a form of cheating - it is an advantage. If you have been around a tricky corner 10 times before, you know what to expect. You know where it goes, whether it is off camber, tightens up, has bumps or a smooth surface. You can concentrate on the unexpected - the 4WD on the wrong side of the road or a freshly gravelled pot hole for instance.
Dirt riding teaches you to read road surfaces better and faster. On dirt, your whole being revolves around not hitting a rock and bending your rims, being speared by a tree, being thrown off by a hump or mud hole, or having the sump ripped out by a mallee root. But dirt riding is usually conducted at lesser speeds than road riding, allowing your viewing “horizon” to drop - that is, where you look is much closer - and necessarily so to avoid the above mentioned distractions. Returning to the road often takes a period of time to adjust - to re-focus your horizon. On the road we are instructed to look through a corner, to look as far ahead as possible, to lift our horizon. It works, particularly well on a race track. But it assumes a clean, safe surface. Usually a compromise solution is required - a scanning technique where you look near and far, regularly. Choosing the right technique for the surface conditions, on reflection, is done automatically and unconsciously I believe. How well we choose is a function of experience.
Know your Bike
You should be able to steer around most nasties on the road, placing the bike to within a few centimetres. Counter steering techniques allow you to pick the bike up mid corner to avoid a pot-hole, tank-slapper inducing hump, oncoming 4WD, or strategically placed gravel strip. This sort of control requires practice. And an understanding of your bike.
Modern sports bikes offer tremendous feedback and feel from the front end. You know what the front end (the tyre) is doing. This is a result of a combination of advanced suspension components, steering geometry, and tyre qualities. Such feedback allows the use of very powerful and sensitive brakes. You can brake surprisingly hard in gravel-in a straight line. But it must be controlled braking - a squeeze rather than a panic driven stab leading to instantaneous lock-up. (The same applies to any sort of braking really - just on bitumen you get away with a stab every now and again, on gravel you won’t.)
Go practice some figure eights and some stoppies! Get some skill. Practice braking in gravel around a corner too, on someone else’s bike!
Confidence
Riding a bike well is an incredibly rewarding and fun experience. But it is not fun if your confidence is down. Hopefully there are a few elements here worth pondering over Christmas which may make riding through unexpected gravel a touch less threatening, and hence riding more fun.
This is just a 2 hour effort off the top on my head, the idea being to impart some hard earned experience for the benefit of the members. It would be fantastic if other riders (experienced or otherwise) could contribute their thoughts and ideas about “Romancing the Stones”, or any other topic for that matter, to the Magazine.
Ben
Warden (ZXR750)