Tyres and stopping distances

Your tyres, each with a contact patch on the road about the size of a large footprint, have to provide the entire grip for:


They also improve comfort whilst carrying the weight of the vehicle. If you look after them, they will work better and last longer.

Neglecting them will be expensive in the long run and could cause an accident and maybe get you or someone else killed.

The legal minimum tread depth for car and similar tyres in the United Kingdom and the European Community is 1.6mm across 3/4 of the width of the tyre  and round the entire other circumference.

When should they be replaced.

Most car tyres have tread wear indicators, usually six small ribs across the bottom of the main tread grooves, and when the tread surface becomes level with these ribs the tyre is at the legal limit and must be replaced.


I always replace mine at 3 mm. The extra few hundred miles is hardly worth the risk.

A depth gauge will let you know when it is time to replace the tyre.

The tyre tread pattern is designed is to give  grip in wet conditions.

The grooves  permit the water to be pushed to one side and allows the rubber to make contact with the road surface.

The  grip reduces as the tyre wears or as the road surface water depth increases and you do need to slow down in those conditions.

What pressure?

Correct tyre pressures are vital for balanced braking, maximum grip and maximum tyre life.

The recommended pressures  vary according to load or speed. Have a look in the vehicle handbook, or talk to  your garage or tyre dealer.

Wrong tyre pressures.

(high or low) will cause more rapid wear and shorter tyre life

Low tyre pressures

also cause increased fuel consumption and consequently increased air pollution.

High tyre pressures

High pressures may give an uncomfortable ride and reduce grip due to the smaller area in contact with the road.

Any incorrect tyre pressure is going to cause handling, braking and steering problems.

Pressures should be checked at least every two weeks and when the tyres are cold. Even a short trip to the local garage will warm up the tyre and raise the pressure. Accurate and reliable gauges are not expensive and will soon pay back their cost.

New car tyres have 8mm of tread.

Dry Road




To give you an idea of what the distances are on the ground the table below measures it truck lengths.

120 feet           37 m                2 ¼ times the length of one of Stobarts trailers.*                                           137 feet           42 m               2½                                                                                                                                   154 feet           47 m                 3                                                                                                                                 172 feet           52 m                 3¼                                                                                                                           188 feet            57.5 m            3½                                                                                                                           205 feet           62.5 m             3¾  **


• As tyre wear increases then stopping distances increase.

• With wet roads stopping distance increases

• With good new tyres you can stop in 120 feet (37m) at 40mph on a dry road;

• On a wet road that may increase by 30%

• Worn tyres (on the legal limit) may double the stopping distance.

Much better to stop behind it rather than halfway along under it.

*New tyres on a wet road at 40 mph

**Worn tyres on a wet road at 40 mph



Road and environmental issues will interfere with stopping distance.

  • Wet road surfaces
  • Loose surfaces
  • External air temperature

But now just to confuse you have a look at another page I have on the website.


It is the original 1947 highway Code.Have a look through this and you will see that stopping distances are the same now as in 1947.

We know that is rubbish.  It is from back in the days when tyres were made of real (rubbish) rubber. Brake drums were as good as baked bean tins and disc brakes were really rare.   http://en.wikipedia.org/wiki/Disc_brake and ABS was unheard of.

Today we have science and technology on our side. ABS, ESP, too many abbreviations to talk about.

Do we need cold weather tyres in Milton Keynes?

Now as well we have tyres designed to deal with cold weather.


The above is worth a read, it may help you to make a decision about whether you need winter tyres. I do not know any instructors in Milton Keynes who use winter tyres, and I personally have never experienced any problems when giving  driving lessons.

I give driving lessons in snow and icy conditions and will teach you how to deal with problems.


this is a work in progress.  More in the next day or two. 04.08.13