Personally, that cracking would not stop me driving the car at all, but I would certainly check the tyre pressures before going anywhere and would not drive it either fast or like I stole it....
You certainly need to budget for replacement tyres in the immediate future - there doesn't look to be a huge amount of tread depth, so new tyres wouldn't be a bad idea for grip in the wet, never mind those cracks.
You can tell how old a tyre is by reading the info on the side of the tyre - you are looking for a string of 15 letters and numbers starting with 'DOT'. Here is the one from one of my tyres:
It's the last group that give the manufacturing week - so my tyres was made in the 24th week of 2012. If yours are very old, it's possible that the code is only three numbers long - two numbers for the week and one for the year, so 011 would be the first week of 2001.
There are no hard and fast rules about how long tyres are safe to use, as most tyres wear out before they 'age out'. But at 6 years old, they are getting old and 10 years is probably a sensible maximum. It's ultraviolet that kills tyres so if they have stood outside all their life, that ages them faster than in a garage.
Looking again at your photo, you have cleverly included one of the tread depth markers built into the tyre - a bump in the main drainage channels:
So that tyre is still legal on tread depth, but only just. My experience (which may be just psychological) is that tyres seem to wear faster the nearer the minimum tread depth they get, so replacing them at 3mm instead of the legal minimum of 1.6mm isn't costing me much - and there is a big, big difference between the wet grip at 3mm and 1.6mm.
They say tyres last around 5 years after which they start to decompose whatever.
Many cars such a classics that may only do a couple of hundred miles a year and still have tyres on well over 10 years old that still havent worn at all and look fine, but take them on the motorway at high speed and they can blow as quite a few have in the past with disastrous results.
If you want a definitive answer just pop into a garage that does MOTs and ask if they will just look and tell you theres no problem, if they say its ok you can then blast off down the motorway without a care in the world?
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