First of all how often is Mot required? By law in the UK the MOT is annually for cars older than 3 years. The test includes general roadworthiness, vehicle safety and exhaust emissions for petrol and diesel engines. Your tyre’s tread depth should not be below 1.6 mm legally. Anything below that would be an immediate fail. Tyre manufacturers recommend a tread depth of 3 mm, but anything between 1.6 mm and 3 mm is still legal.
External damage; bulges or deep cuts on the sidewall indicate a weak tyre. Cracked tyres are dangerous and deep cracks in the tread will fail MOT. When the outside edges are worn and showing ply or cords from within the tyre will cause a MOT fail.
Will a slow puncture fail my MOT? An obvious under inflated tyre could mean a slow puncture. If you have been driving like this for a while it could have damaged your tyre. Check your tyre’s sidewall for damage, an underinflated tyre puts a lot of stress on the tyre sidewall and there could be excessive tyre wear on outside edge. Also check the inside edge for tyre wear to make sure. it is possible you may fail MOT if there is obvious damage to the sidewall. It will raise a red flag if one tyre have visually less pressure than the rest. If your car has a tyre pressure monitoring system (TPMS), it will be checked. Any bad sensors could cause a MOT to fail.
Can you pass MOT with spare tyre on? If you had to replace your tyre with a space saver then the answer is no. Your tyres need to be the same size on one axle to be legal.
