Today I got new shoes for my Harley-Davidson Fat Boy. I’m told a pair of tyres on the Fat Boy can run for 15,000 to 18,000 kms. But I like to change tyres at intervals of 11,000 or so while there is still some life left in them.
The reason for doing that is traction. Imagine a brand new tooth brush and the resistance you feel when you scrub the bristles against your teeth. Say you take a scissors and cut the bristles almost completely, leaving just a stubble. Now imagine the resistance you will feel while brushing your teeth. Hardly any. The tooth brush will simply slide over your teeth.
The same thing happens with tyres. As the tyre tread wears out, the ability of the rubber to bend and offer tractive force significantly reduces. A good sign of this happening is the early kick-in of the ABS system when you brake hard. There isn’t enough rubber on the tyre to provide tractive force and the tyre beings to skid causing the ABS brakes to come the rescue. If your motorcycle doesn’t have ABS brakes then all the more reason to not burn your tyres till the nylon threads start to show.
Traction is also the reason why almost worn out tyres are chosen for doing burnouts. You actually want the rear tyre to slip while you keep the front brake locked down. Now imagine you are negotiating a corner with worn out tyres and you twist the throttle to accelerate. The rear tyre may not find the traction it needs and will slip which may end up with you losing the rear end and low siding out of the tarmac.
I see people riding their motorcycles armed to the teeth wearing full riding gear. Then I look at their tyres and often shake my head in dismay. I don’t know about you guys, but I consider tyres to be part of my safety gear. Because these are the two very important pieces of equipment that keep you from hitting the tarmac.