Safe Speed Forums

As alluded to previously, but I am not sure anyone has articulated yet, and given that the purpose of tyre tread is to dissipate standing water, were the limits of braking at which traction was lost, in these tests, reached due to aquaplaning or lack of friction. Only the former could be improved by more tread, the latter would actually be solved through a compromise of less tread, whilst leaving enough to prevent aquaplaning!

I'm sure this was somethig AutoExpress tried a year or so ago. We'd need to look at the methodology of the tests very carefully to see whether the results were valid. Someone has already suggested that the different vehicels were on different tyre makes. Also, these reults, are they for the MPV, the sports car, the saloon...? (or, possibly, the "whatever vehicle was likely to suit their purposes best in each test"?

That kind of results scatter is less than I'd expect from a test amongst all the brands of tyre currently available to buy legally in the UK these days anyway. They ought to ban crappy no-name tyres before they start on tread depth! It really says something for the intellects involved that there is currently no legal requirement for the amount of grip a tyre has and as a result, they vary wildly. Still, if everyone has to change their tyres more often, I expect they'll buy cheaper tyres, so as long as the tread depth is OK, let's not trouble ourselves with tedious details like whether or not they work!

I don't know why they're stopping at 3mm anyway - clearly 8mm is better still and as organisations like this have the "what price a human life?" as their stock phrase, surely no price is too high? We should obviously change our tyres before every trip!

Maybe the the MOT could include a test of tyre grippieness under dry and wet conditions? Per vehicle that could mean something...?

_________________
Andrew.

As part of their type approval, tyres need to meed load carrying and speed capabilities appropriate to the claims on the sidewall. These are tested for compliance. There is a proposal currently out to make grip (longitudinal AND lateral, I think) part of this testing regime. I think that will probably cure it! Measuring it at MOT would be difficult because it varies so much with things like temperature and the weight of the car on the tyre.

When I used to race in the Super Road Saloon championship we had to run road legal tyres. In order to get best performance in the dry we used to get new tyres and GRIND THE TREAD OFF to the legal minimum. This significantly improved performance. If you did not do this you were simply not competative.

So its swings and round abouts more tread means better in the wet worse in the dry and visa versa.

_________________
Speed camera policy Kills

It was the same when I used to race Prodsports... For dry races the tyre manufacturer to whom I was contracted used to supply brand new tyres with only 3mm of tread (because the regs stated that we had to finish races with no less than 2mm, to stop people using "instant slicks"). If it was going to be a wet race, we used tyres with about 6 - 7mm - they cleared the water as well as new 8mm treads but were rather more stable under load.

_________________
"Politicians are the same the world over... We build bridges where there aren't any rivers." - Nikita Kruschev

I see the 'Tyre Industry Council' are listed as an associate organisation.
As the famous comedian Max Miller might have said, "Now, there's a funny thing".

The other thing to consider is that because of the now complex tread patterns modern tyres have tread wear indicators. Thes show when the minimum operational depth has been reached and is very easy for anyone to visualy check. It would require tyre manufacturers to re-tool tyres for the UK market....meaning more expensive tyres.





Yes indeed. Don't expect balanced research there. All of their profit comes from aftermarket sales.

_________________
Speed camera policy Kills

I thought that the tread wear indicators were set at 2mm for an international market.

Can anyone confirm, one way or the other?

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

http://www.tyresave.co.uk/tyreinfo.html



I believe that 1.6 is the international standard.

http://intune.stamfordtyres.com/index.php?option=com_content&task=blogcategory&id=6&Itemid=26

_________________
Speed camera policy Kills

Super, thanks.

I wonder if it used to be 2mm?

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

Regarding tread wear indicators; IIRC all motorcycle carry them as standard too. Certainly the makes that I have used do.

_________________
Prepare to be Judged

My wife does so few miles that her tyres would age and perish before they get down to 1.6mm. I change them when the rubber goes hard and starts to lose grip but they usually still have nearly 4mm of tread and so are perfectly safe (according to Brake).

Most tyres have about 8mm when new. I'd estimate avg life to 1.6mm is around 25k avg so something like 360BNvm isn't that something like 10M extra tyres needed and disposed of per year

Hardly good for the planet.

Add to the fact that most change their tyres at 2mm you'd be seeing people discarding tyres at 4mm. That's 30% ish of the tyre going in the bin.

Given that only 1% (defective tyres) of accidents were caused by illegal tread depth and poor inflation. I wonder how many of the 23 total lives could be saved by going for 3mm? I'd estimate no more than 3 or 4 at the most.

Interestingly that is the same number caused by traffic calming but we don't here brake getting upset by that

source:
http://www.dft.gov.uk/172974/173025/221412/221549/227755/285672/Article4ContributoryFa1.xls

Likewise -last car I got was about four year old when I got it - about a year later with about 38k on clock noticed that the tyres were cracking between the treads although still with more than 4 mm. All four had to go ,not because of low tread but due to old age.

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on