Tyre tread depth

[fly258]

What determines the original tread depth on new car tyres?
Obviously too little and they won't last long, but why don't they make them with say, 15mm of depth? Does it effect their performance? If so, how?

[Impret-Sir]

Two things occur to me, if the tread blocks were too long then they would not be stable, they would 'bend over' under cornering or breaking, and this would certainly effect handling, a bit like driving with an underinflated tyre. Secondly, if a tyre had a lot more tread when new it would last a lot longer and you would buy new ones less often, adversly effecting the tyre companies' profits.

[sddsddean]

Agree with I-S that the tread pattern could be a problem on a car tyre. On my truck tyres, which are around 300mm wide, you can get a lot 'chunkier' tread pattern and consequently original tread depth is 18 - 22mm depending on make.

[Jay70]

If you ever watch F1 racing ,you'll notice that if the cars are running on wet weather tyres with a tread pattern, as opposed to the dry weather groved tyres, that when the track starts to dry out they have to keep driving into the puddles to cool the tryes down. This is because the blocks in the tyres move about and warm up and without the water to keep the temperature down then the tyre will get excessivly hot and may delaminate. So from this I would deduce that there is a safe maximum tread depth for the tread on a standard all weather road tyre.