When do tires lose their grip on the road?

Tire traction should be as follows 6/32 is ideal, 4/32 is average and fairly good, 2/32, you should probably think about replacing them. You can buy a tire gauge to measure the traction at any auto parts shop.

“Depending on the severity of the rain, a tyre will have to push away anything from 4 to 9 litres of water per second as you travel along a highway at 100km/h. If a tyre is worn out, the tread cannot adequately disperse the water at the contact patch and a film of water will be sandwiched between the tyre and the road surface. And once this happens, the grip totally disappears.”

When this starts happening?

Just after the screeching stops! ( the tyres not the passengers , they won’t stop).

When you go past Centrelink.

water on the road  is in fact a lubricant for rubber so that is when the tires  or tyers loose traction 

Grubbie lost his nerve years ago.

When you accelerate, brake or swerve suddenly...

When you apply too much power to the wheels to be able to grip the road quick enough to push the weight of the car, bald tyres still grip the road unless the road is wet.

This is Australia, it would be nice if we kept spelling like Australians and not Americans, the word is spelt "TYRE".

When centripetal force exceeds the amount of friction force created by the given tires and the given road.