Well the answer is 1.6 millimetres, so what was the question? A reader called up to ask what the official minimum tyre tread depth is. He had asked his mates and depending upon which “bar room lawyer” he spoke to, he got a different answer; well there’s a surprise, so I double checked with the ITV and got him the response


Regular readers will know that every now and then I get an “anorak moment”. You know how it is, you ask a fellow a simple question and you get a full blown answer regarding how many miles of rail track there are in the world, the amount of feathers on a particular bird and his opinion as to the quantity of objects in the sky. The stereotype is a solitary person totally engrossed in his subject and is found in isolated places following his passion. He always wears an anorak and there is no such thing as a simple answer from these people

Well I try to avoid these moments, but every now and then, the urge is overwhelming, so bear with me whilst I go into detail before the anorak gets put away again for a while

Not so obvious

As well as getting the above, answer only the week before, a customer’s car failed the ITV because there was a problem with his front tyres. They looked fine at a glance, but from the depths of the inspection pit, it was obvious that on the inside edge, they were as bald as the proverbial badger’s rear end. After consultation with the customer, I drove off to have them replaced; it had been raining heavily and I quickly realised that I had no grip on the tyres or road, but the steering wheel was being very firmly gripped! The effect of the baldness could not have been more apparent

Details for the inquisitive

So you look at your car tyres, which as the manufacturers tell you, are what hold you onto the road and you are confronted by a bunch of numbers and letters. So what do these mean? Here is an example 195/65 R15 91H.

Well 195 is the width in millimetres, now we can all understand that. 65 is the height of the tyre from wheel rim to the edge divided by the width. Yes really. Why the height isn’t just stated, I don’t know. I suppose it could be calculated, but by now I’m starting to suffer from information overload, but we’ll carry on a moment longer. “R” is radial. Many of us will remember cross ply tyres and when radials came along, even the bar room lawyers knew that they could not be mixed with cross ply on the same axle

15 is the inside diameter of the tyre, or if you like, the wheel size. Now this figure unlike all the others is given in inches (pulgadas to the Spanish) and proves that the wheel really was invented by the British! Makes you feel proud eh?

The letter “H” covers the subject that has made more tyres fail the ITV than for any other reason. This letter indicates the maximum speed that the tyres can be used at and is set at the time of manufacture of all cars and bikes. For reasons of safety, tyres with a lower rating are forbidden. Why should this concern us? Well for reasons I don’t even want to know about, the speed rating doesn’t seem to be a big deal in the UK, but here in Spain it is rigidly adhered to, so over the years a number of customers have had to change what were perfectly serviceable tyres because Slow-Fit or Herfords have fitted tyres that are acceptable in the UK, but not here. The speed ratings start with the letter “L” (120 KPH) up to “Y” (300 KPH). In our example, “H” means that the tyre is safe for speeds up to 210 KPH.

To find out what yours should be, look in the manual, or ask a reputable tyre fitting company; NOT down the local pub

Unless we have a tyre depth gauge in our back pocket, how do we know if our tyres are OK? Well some clever people have made that easy for us. At the bottom of the grooves in the tyre is a bar of rubber that does not quite go across the whole width of the groove. The height of this bar is, surprise, surprise, 1.6 mm. This is called a wear bar and when it is in line with the remainder of the tyre surface, you are overdue to replace the tyres

What does the 91 in our example mean? Well actually old chap as I was just saying it means that the tyre is safe to carry a load of 615 Kg, with 62 carrying 265 Kg and the maximum of 126 carrying 1700kg. Don’t worry about this one unless you are a detail freak in which case pop down to “Faster Fitters for Fun S.L”

Finally before I get tyred of this subject. In Spain the tyre tread pattern has to be identical on the same axle. So you can have matching pairs as all four do not have to be the same

Spare wheels

The spare wheel does not form part of the ITV inspection, so if you have an odd tyre on your car, take a look at the spare as you may be able to make up two pairs using this one. An explanation given to me as to why the spare is not examined is because of the modern proliferation of “space saver” wheels. Maybe this is so, but I’ll bet that if most of us looked at our spare, we would find it flat and worn around the edges; not a pretty sight when you are on a narrow hard shoulder, it’s raining and the kids are screaming

The first sight that I had of the spare on my Citroen (which I’ve just sold) was shortly after I bought the car a couple of years ago. I drove over a speed hump which was painted black just to make sure that I didn’t see it coming and was greeted by an almighty bang and the sound of tortured steel. The spare was slung underneath, but the bracket holding the carrying cage had not been tightened up, so the cage was dragging along the road and the spare wheel was forlornly awaiting retrieval from the

road. The following driver was laughing his head off; only later did I see the funny side

Glad you asked now?