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Michelin’s technical manager Tony Charlton explains why tyres are so groovy
The reason you have grooves is to remove water from the contact patch, but also because the edges of the grooves produce very high-pressure areas that cut through any film of water or grime.
The high pressure is created when the tyre rotates and the edge following the groove hits the road surface fractionally before the rest of the tyre, with the weight of the bike pushing down through it.
That’s why some of our tyres have a lot of sipes – the very thin slits. These actually close up as the contact patch is formed, but when they first touch down they create that high pressure edge.
The beauty of a motorcycle contact patch is that it’s oval, with a point at the front. It acts like the bow of a boat, pushing water out of the way, and does the majority of the water clearance work. If a tyre was very thin and high pressure – like a bicycle tyre – it wouldn’t need grooves. In fact, the only reason we put grooves on narrow bicycle tyres is to make people more confident in the wet. They’re cosmetic.
But with a motorcycle tyre in the wet, grooves store water rather than channel it, as they do on car tyres. This is why motorcycle grooves don’t have to be continuous – they don’t have to push the water anywhere. Tread shapes are partly dictated by aesthetics, but the tread blocks in between need to be able to resist the forces of braking and acceleration. That’s why tread patterns on a front and rear tyre are the reverse of each other.
They have to cope with opposing forces – braking at the front, acceleration at the rear. If you ran the tyres the wrong way round they would feel pretty similar, but you’d notice less stability if you were pushing on, and they would wear faster. I don’t recommend it...