Tassie Riding in Summer

[Batfink]

hey baz.. now I am at work I got time to research

found this

Hi, I'm from Dunlop motorcycle tyres and I hope what follows explains why front and rear tread patterns are in opposite directions to each other. Brummmie and mojitomax have got the right idea but this is the full expanation.

Tread patterns have several other duties other than evacuating water. One of which is to contribute to even-tread-wear characteristics, i.e. not wear out in a stepped manner that can affect a bike's handling towards the end of the tyre's life.

In order to give smooth, even wear the tread grooves need to be aligned with the forces acting upon the tyre. With the rear tyre the forces are accelerative (from the engine) and cornering. The further the bike is leaned over the less effect the accelerative forces have because the amount you're on the gas reduces as lean angles increase. But as the bike is leaned further over the more the cornering forces come into effect.

So in the centre of the tyre the grooves tend to be more circumferential in order to align them with the accelerative forces pushing the bike forwards at more upright angles. But the grooves gradually arc outwards towards the tyre's shoulders as the cornering forces come increasingly into play. Hence, even though most tyre tread designs differ from each other you will usually find large elements of arcing tread design. And those tyres that don't follow this principle tend to have poorer wear characteristics.

Because bikes are not 2-wheel-drive vehicles, the forces acting upon a front tyre are not accelerative and cornering but braking and cornering. Braking forces affect a rear tyre a little but they are overwhelmed by the accelerative forces. The vast majority of the bike's braking is done by the front tyre and braking forces are in the opposite direction to accelerative forces so in order the align the tread grooves with these forces from upright to leaned over they need to be in the opposite direction to rear tyre tread grooves.

This principle holds true for all of our road and race radial tyres: Roadsmart, Qualifier, Qualifier II, Qualifier RR, GPR Alpha-10, GP Racer D209 and D211GP.

If it's the thought of poor water evacuation that's concerning you, don't worry. When it's raining, research with our development riders has found that on the road, riders rarely lean beyond 28 degrees. 25 to 30 degrees being the usual range, depending on the rider's experience and riding style. So the grooves that clear the majority of the water are concentrated in this zone of the tyre and you'll notice that the grooves in this area of your tyres are largely circumferential on both front and rear, so no problems with water evacuation straight out from the rear of the tyre's contact patch.

New developments in compounding are also having a greater effect on a tyre's wet road grip. The Qualifier RR has as much wet road grip as all-round sports-touring tyres of just a few years ago, despite having far less tread grooves.

When the road dries out you use bigger lean angles so we reduce the amount of grooves further out towards the shoulders, where there is reduced need for water clearance. By having less grooves on the tyre's shoulders, and hence more rubber in contact with the road, dry road grip is increased.

I hope that helps.

the clarity has gone from mud to very silty/brown water.... LOL

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oooh and the directional arrows re also there due to tread splicing as well.. so don;t try to turn around even a slick tyre otherwise you can cause a catastrophic failure of tread peeling off carcase..

the things u learn ;)