TYRE PRESSURES

[jerrytr5]

I owe a lot to the advice and knowledge found on this forum and I am almost convinced by the arguments. But you are still excluding the requirement for braking from the equation.

I find it difficult to ignore a critical factor because it doesn't fit the longevity equation. I wonder what those two cars in the video would have shown with a brake test.

We know that the front brakes do more work than the rears (that's why we have discs front / drums rear).

A quote from kwikfit "At 30mph on a wet road, a car with brand new tyres with 8mm of tread will come to a stop in 25.9 metres. The same car travelling in the same conditions but fitted with tyres with just 3mm of tread remaining would come to a stop in 35 metres. That’s 35% further despite the tyres still being perfectly legal."

So when I'm cruising down the motorway in the wet and it all comes to a stop in front of me, I think I'd be glad I fitted the tyres with 7mm tread on the front, not the ones with 3. I'll take a chance that I have sufficient skill to prevent the car swapping ends which seems more survivable than disappearing 5 metres under a stationary HGV.

In a perfect world I'd have 7mm all round of course, but sometimes life just doesn't conform.

As dear Mr Pringle would have said 'end of'.

Jerry

 

 

[Motorsport Mickey]

Well it's a brave man that wants or thinks he can "buck the trend" of tyre manufactures and driving experts but picking a specific isolated instance of wearing your tyres down to 3 mm ignores exactly when you'd like to change your tyres ?

Will you "even" out the odds by just changing your front tyres for a new pair when you get down to 5mm  ? and then again the same thing when in 10,000 miles you have taken the surplus 2mm off from the 7mm new tyres then fitted to the front axle ? Of course you won't, the tyre manufacturers pick the comparison between 7mm new and 3mm part worn because they can justify there where the extra mm on tyres give you a benefit, and for impecunious owners the "buy now" mental signal for tyres. If you drive according to the conditions you will be a very unlucky driver not to be able to stop in even the extended distance a part worn tyre will give you. 

In contrast on an unfamiliar road in wet drenched conditions ( on 3 occasions during the last month I've been in this position) , once with a caravan in tow and on a downward gradient had to take a left hand bend at a road speed I considered was just underneath the maximum grip available (about 45mph) on a new set of tyres all round ( 4 months ago, so very near your perfect world ) and was very pleased my rear tyres had surplus grip in hand.

Why did they have surplus grip in hand ? because they were very near new and still with a soft compound (not hardened off with continual hot/cold cycles) and the tyres on the front although the same age (and at only 4 months old) had already had the edges taken off the thread blocks by the steering and front wheel drive and I was driving within the front axles now reduced grip available. That's the likely real world conditions we all experience a considerable number of times a year without being able to minimise it, other than by driving to the road conditions. Just as in your example about a sudden tail back and stop on the motorway, good driving skills gives you the extra braking space and will allow your car to stop in the distance between you and your HGV, no matter what your front tyre age or conditions...go slower.

For all tyre manufactures to cost themselves money (new tyres on the rear wear out slower) and the likelihood of litigation in the event their "fit new tyres to the rear of vehicles" advice is contributory to an accident,should convince you that they are sure their advice is correct and will withstand examination even in a court . However just to confirm, I knew Alec Pringle since the early 1970s ( I make that over 40 years) and over that time until recently he has been a good friend to the TR Register and their various car owners, Alec would always argue you drove your car according to the road conditions and would have no truck with a driver who wasn't far sighted enough to allow for those conditions...whatever tyre equipment was on the car.

Mick Richards

Edited October 22, 2019 by Motorsport Mickey