Whilst cleaning car this morning notice all 4 tyres have small cracks round the outside, car is coming up for 3 years old and has done just over 20k miles.

Tyres are Bridgestone Turanza and are original from when car was new.

Safe or replace?

Depends how big they are.

My car failed an MOT on Wednesday due to cracks in the wall. They were big though. (On two 8 months old tyres)

In terms of MOT requirements, and I guess therefore safety, if the crack is over something like 25mm, or they can see the thread, it's a fail.

How bad are your cracks?

Sorry forgot pic

Don't look too deep, would probably sand off

There looks to be cracks in the base of the tread as well - what's the depth of tread left?  If it's not much left it might be worth replacing of peace of mind.

 

I have to admit driving cars with tyres which probably had the same sort of cracks but I can say I'd advise it...  But then after cheaping out of tyres as I was replacing a car and then having an accident cause I couldn't stop in time (lorry hit a wall throwing large stone blocks into the road in front of me which took out my radiator) I'm now extremely wary of pushing my luck with tyres.

 

Seems like this has been discussed before, a number of people suggest contacting the manufacturer to see about getting a refund for the remaining tread,

http://www.briskoda.net/forums/topic/275103-tyres-loads-of-tread-left-but-cracking-all-over/