Safe Speed Forums

Have you actually tried taking a porsche with only 2mm of tread left on the wet?

Try it, than tell me again that 2mm is fine.

You are fooled by the fact that top quality rubber will be better at evacuating water: that is compared to the same tyre when new. It does not say that at 2mm they are fine.

Most tyres' tread grooves tend to narrow as they get more consumed. Moreover, the smaller diameter will cause a 1 or 2% increase in rotational speed.

Add to that that most tread compounds have less silica the more they get consumed because of tyre tread deflection, and that some of the gooves actually disappear under 4mm.

On some trackdays, in the wet, they don't even allow you to access the track if you have less than 4mm of tread. And on a track day, you have much more room to play with if the back end decides to step out or the front end decides to straighten a corner.

I am bringing the example of sports cars because recently, most new cars are fitted with ultra high performance SUMMER ONLY tyres which people assume must be better in the wet in any condition.

As for aquaplaning, if you can't feel it, is mostly because many cars fail to provide feedback to the driver about it. I have driven in plenty of situations (even in this country) where I could tell if I had to brake it would take a long distance and a lot of skill. Just because you haven't, does not make it safer.

Incidentally, the more expensive a tyre (bigger, lower profile and wider), the more often it should be changed.

And when you have tyres that last 12k miles at most, and you drive 1000 miles a month, you can go from fairly acceptable to downright dangerous in a matter of days.

no, that's why I asked the question. Doesn't have to be a porsche. What's the difference in stopping distance between a car with good brakes and decent tyres with 2mm of tread and an average car with new but not so good tyres?

I have driven cars (as I'm sure most people have) with only 2mm of tread left and only had problems (if you want to call them that) in monsoon type conditions - in Oz when the heavens open they really open. The symptoms? Slight aquaplaning at 100km/h. Solution? Slow down. No further problems.

I've never owned such a car. They certainly exist, but I won't ever be found driving one with any regularity. I value my ability to deduce grip levels from steering feel far too highly.



So are you talking about aquaplane risk or something else entirely? And if it's something else, what is it exactly?

btw, here's a top anti-aquaplane tip for 'common conditions':

Where you encounter 'rivers' of surface water running across a road, or in any circumstance where you know you are entering an area of increased surface water, make sure the throttle is trailing when you hit it.

This is of several different benefits.

1) The forwards weight transfer assists the front tyres squeegee effect, while the backs run happily in the dryer tracks made by the fronts.

2) With FWD cars power tends to 'pull' you up onto the (aqua) plane negative power tends to help the front wheels to dig through the water.

3) If you are unlucky and an aquaplane starts you are in the best position to finish it. (i.e. slow down gently, make no control movements.)

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I agree that on cars that have little braking power, 2mm and 3mm won't make much difference.

But on any car where braking distances are measured in feet, not in miles, the difference is there, and should be noted.

We want legislations to keep up with reality. 1.6mm now that most new cars have strong disc brakes and UHP tyres, to me seems a recipe for disaster.

It is like saying that we should allow for cars to be built capable of 200mph with drum brakes. Heck, all you need to do is brake earlier isn't it?

Why do we need MOT anyway? If my left turn signal doesn't work, I simply won't turn left. If my headlights don't work, I will simply not drive at night. If my windscreen is cracked, I'll just open the sunroof and lift my head.

If we want to allow for motorists to travel faster (I certainly do), than we must insist on cars to be safer, not only when they come out of the factory, but by insisting regular maintenance is spot on.

1.6mm tread depth was fine when tyres were as wide as a pencil, and had very little water to disperse. Now we have tyres that have a footprint way too big to be safe at 1.6mm of tread depth in the wet. Of course you could buy all season tyres, but than why not have two different rules, one for summer only tyres (99% of the population), and one for winter or M+S tyres (the remaining 1% who already check their tyres more frequently).

Even off roaders are now fitted with summer only tyres, and rely on electronics to keep the passengers alive in wet weather.

Of course different cars have different braking abilities, and the driver should be aware of them. But when you rely on the car's braking performance, the last thing you want to think about is how much tread is left over.

You will be surprised at the delay in feedback most cars have.

You notice you are aquaplaning later than you think.

IMHO relying on skill alone on the public road is silly.

On the track I switch traction control and stability control off. On the public roads I don't. Call me chicken, but I care too much for my life.

Maybe I am just paranoid and check tyre pressure every week and tread depth every other week.
Maybe I know tyres are the only contact between the car and the road, and their importance is way underestimated.

Please do.



such as?



Aquaplane is all or nothing as definition. The effects of it are not. As the tyre tread is unevenly consumed, and the surface is uneven, and there are four tyres not just one involved, aquaplane for the vehicle as a whole may take place partially.



This is a ROSPA test.
http://www.rospa.com/roadsafety/advice/ ... _depth.htm

Taking the test at face value, and for example, deciding that if stopping (from an unknown speed) taking over 32.5m is dangerous, then you should be campaigning against smooth concrete, not tyre tread depth.

I also note that the tests were paid for by the British Rubber Manufacturer's Association. That's FAR from independent, because changing tyres earlier will massively increase their members' sales.

And RoSPA are too far gone to take seriously.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

yes, and they've said this:


but those percentages seem to relate to the difference between 3mm and 1 mm not 1.6mm

asphalt: 3mm = 27m (approx)
1.6mm = 33m (increase 25% not 36%)
1mm = 37m (increase 36.8%)

concreate 3mm = 36m
1.6mm = 42m ( 17%)
1mm = 48m (35%) no quite the 44.6 they're claiming here.