Winter Tyre Pressure

[woodshaper]

What Tyre pressures are people using in their Winter tyres?

The Garage inflated mine to 30 PSI (205x55X16 H)

woodshaper

[3rensho]

I keep mine at 35-36 psig as recommended on my door panel sticker. 205x65 R15

[woodshaper]

Just had a word with a Local Tyre Dealer, they advised using the manufacturers standard pressures but to lower the pressure depending on depth of snow.

woodshaper

[corkgsxr]

For a car 33 untill the proper ice hits then 29 to 30.

Same with van just drop 3 or 4 psi when the ice hits.

Any more and you lose grip

[woodshaper]

Thanks for the info.

Went out am and drove up two long steep hills with a covering of about 3 inches of snow which had started to freeze, got wheel spin. (at 30 psi)

Increased PSI to 34 front 32 rear and drove up a freezing slush covered long steep hill this afternoon at a steady 20-25 MPH, no problems!

Can't say that about the twit who followed me up at the same speed, he WAS following me UNTIL HE GOT TO THE SHARP BEND AT THE TOP!

Happy to have the ability to brake/stop safely in these wintery road conditions we now have here, I need it to be able to avoid the other DIP STICKS out there!

woodshaper

[philip]

Out of experience i never trust garages and tyre places putting the correct pressure in. I got 4 new winter tyres and not 1 of the 4 had the correct pressure i knew when i drove out and the car handled strange, then drove to pressure pump i always use.

[Northman]

Just had a word with a Local Tyre Dealer, they advised using the manufacturers standard pressures but to lower the pressure depending on depth of snow.

woodshaper

For a car 33 untill the proper ice hits then 29 to 30.
Same with van just drop 3 or 4 psi when the ice hits. 
Any more and you lose grip

Not according to the AA, who say on their Winter Tyres page "Check tyre pressures too but don't be tempted to try reducing pressure when there's snow and ice about – it doesn't help with grip and can affect handling."

The Institute of Advanced Motorists says the same thing: "Do not be tempted to reduce pressure to increase grip. Tyres with low pressure do not have any more grip and are prone to overheating and blowouts."

[corkgsxr]

Reason they say that is most people will wait until there stuck before they drop dropping pressures and will take a guess at it. 95% will go way to low and instead of a enlarged contact patch they end up with a W effect where the centre raises off the road reducing grip and highly increasing rolling resistance.

To further the problem most bad ice is only short sections so when they pass to normal roads the go up to 60/70 mph on quite underinflated tires.

3 psi will enlarge the contact patch, tires will warm up faster but its not near enough to Overheat. Might cause a marginal lowering of mpg.

This is why they advise not to. Average person will do it in a panic and do it wrong

[Northman]

Reason they say that is most people will wait until there stuck before they drop dropping pressures and will take a guess at it. 95% will go way to low and instead of a enlarged contact patch they end up with a W effect where the centre raises off the road reducing grip and highly increasing rolling resistance.
. . .
This is why they advise not to. Average person will do it in a panic and do it wrong

I would be interested in knowing how you know that this is their reason for telling us that reducing pressure does not improve grip.

[corkgsxr]

The aa spokes man is regularly on today fm. He sed so.

Iv a great understanding of the affect of pressure differences on tires.