For the purposes of accelerating and braking in a straight line it is important to have the tyres in contact with the road. Aerobatics, whilst exciting and dramatic are not really appropriate for the highway. Similarly, for the stability of the machine when cornering, contact with the road is essential.
Now, on a board-flat, dry racetrack we can fit a tyre with no tread. What is important to traction during accelerating and braking is the size of the tyre’s contact patch and the friction between the rubber compound and the road; clearly a tyre with no tread has more rubber in contact with the tarmac. Your tyre pressure is important here:
You can see that the correct inflation pressure (and this is related to the combined weight of the rider and the machine) results in the maximum contact area. But of course, we don’t ride around all day on dry, flat race tracks or even dry, flat roads – we have water to contend with.
Aquaplaning occurs when a combination of speed, tyre wear, tyre inflation or the depth of water on the road causes a loss of traction. Basically, a layer of water creates a cushion between the road and your tyres, drastically reducing the friction between the compound and the road surface.
Tyres are designed with grooves and ‘sipes’ to allow water to disperse away from the contact patch and to allow the rubber compound to maintain contact with the road. At higher speeds, the wedge of water in front of the tyres may pass right under the tyres with the result that the tyres will ride on a cushion of water. This is obviously not desirable since it results in a complete loss of friction between the tyre and the road…
But of course our wet roads are also not flat – we also have bumps to contend with. Newton’s Second Law of Motion tells us that “the acceleration of a body is directly proportional to, and in the same direction as, the net force acting on the body, and inversely proportional to its mass” which means in this context that if you exert a force on your motorcycles front wheel, via a bump in the road, it is going to accelerate in the same direction as the force was applied; and if it is a lightweight motorcycle it will accelerate more for the same bump. Now, having bounced your front wheel clear of the ground, your ability to maintain your tyre’s contact patch and your braking ability is going to be compromised, isn’t it!
What we need then is some form of spring suspension arrangement. Some of this comes in the form of tyres, and some in the front & rear springs.
As you will see from the foregoing, it is most important to keep the front wheel in contact with the road if we want to steer and to avoid falling off. Springs at the rear end are mostly concerned with your comfort and you will see many pictures in this book showing Bantams with no rear suspension. Whilst there are many incarnations of front suspension, the one we see today and on our Bantams is the telescopic fork – essentially a pair of tubes, arranged to slide inside one another and provided with a spring to absorb the energy from the bump which is all you need – except when we realise that the energy stored in the spring by the compression from the bump will be released again as soon as the bump is gone, and if it is of sufficient magnitude will result in the wheel bouncing off the road again. Thus we need a method of releasing that energy slowly, or damping it. In early Bantams this is not really addressed, except perhaps by excessive friction; later machines have hydraulic damping within the fork leg.
Now, on a board-flat, dry racetrack we can fit a tyre with no tread. What is important to traction during accelerating and braking is the size of the tyre’s contact patch and the friction between the rubber compound and the road; clearly a tyre with no tread has more rubber in contact with the tarmac. Your tyre pressure is important here:
You can see that the correct inflation pressure (and this is related to the combined weight of the rider and the machine) results in the maximum contact area. But of course, we don’t ride around all day on dry, flat race tracks or even dry, flat roads – we have water to contend with.
Aquaplaning occurs when a combination of speed, tyre wear, tyre inflation or the depth of water on the road causes a loss of traction. Basically, a layer of water creates a cushion between the road and your tyres, drastically reducing the friction between the compound and the road surface.
Tyres are designed with grooves and ‘sipes’ to allow water to disperse away from the contact patch and to allow the rubber compound to maintain contact with the road. At higher speeds, the wedge of water in front of the tyres may pass right under the tyres with the result that the tyres will ride on a cushion of water. This is obviously not desirable since it results in a complete loss of friction between the tyre and the road…
But of course our wet roads are also not flat – we also have bumps to contend with. Newton’s Second Law of Motion tells us that “the acceleration of a body is directly proportional to, and in the same direction as, the net force acting on the body, and inversely proportional to its mass” which means in this context that if you exert a force on your motorcycles front wheel, via a bump in the road, it is going to accelerate in the same direction as the force was applied; and if it is a lightweight motorcycle it will accelerate more for the same bump. Now, having bounced your front wheel clear of the ground, your ability to maintain your tyre’s contact patch and your braking ability is going to be compromised, isn’t it!
What we need then is some form of spring suspension arrangement. Some of this comes in the form of tyres, and some in the front & rear springs.
As you will see from the foregoing, it is most important to keep the front wheel in contact with the road if we want to steer and to avoid falling off. Springs at the rear end are mostly concerned with your comfort and you will see many pictures in this book showing Bantams with no rear suspension. Whilst there are many incarnations of front suspension, the one we see today and on our Bantams is the telescopic fork – essentially a pair of tubes, arranged to slide inside one another and provided with a spring to absorb the energy from the bump which is all you need – except when we realise that the energy stored in the spring by the compression from the bump will be released again as soon as the bump is gone, and if it is of sufficient magnitude will result in the wheel bouncing off the road again. Thus we need a method of releasing that energy slowly, or damping it. In early Bantams this is not really addressed, except perhaps by excessive friction; later machines have hydraulic damping within the fork leg.
