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vegabass
12-15-2005, 12:57 AM
Whats going on,

I got myself some snow tires and i was wondering what PSI (air pressure) i should be at. Someone told me to be at a lower psi in the winter. The sticker on the door rating is at 32 psi front, 38 psi back. and then its like 39 front 46 back. I dont know what it should be at. PLEASE HELP. Car 330i

Jiver
12-15-2005, 01:25 PM
Vegabass,

The first two values are for normal loads and the second set of values is for maximum load. I suggest you go with the first set of values, 32 and 38. If you are constantly driving with four passengers and luggage go with the higher values.

Quack
12-15-2005, 01:47 PM
put 4psi higher than what normal rating is, in the winter tire pressures go down so you have to add more to componsate, if you put lower psi in your tire you will have a larger contact patch to the ground which you don't want in the winter

vegabass
12-15-2005, 02:29 PM
put 4psi higher than what normal rating is, in the winter tire pressures go down so you have to add more to componsate, if you put lower psi in your tire you will have a larger contact patch to the ground which you don't want in the winter

How come u dont want more contact patch. I thought that is what you are trying to achieve? Its me myself and i driving most of the time so i should do that 32 and 38 or do what quack said and go 36 and 42 psi then? How come they are different from front to back? All my family members cars have the same psi all around.

Axxe
12-15-2005, 04:09 PM
In the snow less is more. More weight per unit of area is a good thing (reduced contact pactch).

Quack
12-15-2005, 08:20 PM
How come u dont want more contact patch. I thought that is what you are trying to achieve? Its me myself and i driving most of the time so i should do that 32 and 38 or do what quack said and go 36 and 42 psi then? How come they are different from front to back? All my family members cars have the same psi all around.


you want the tire to be more narrow, so higher psi will make the center of the tire the contact patch, when it's narrow the tire will cut through the snow easier, here's a cheesy example, hockey skates are narrow, less contact but easy to control, hockey puck more contact patch, all it does is slide all over the place :D

vegabass
12-15-2005, 08:50 PM
you want the tire to be more narrow, so higher psi will make the center of the tire the contact patch, when it's narrow the tire will cut through the snow easier, here's a cheesy example, hockey skates are narrow, less contact but easy to control, hockey puck more contact patch, all it does is slide all over the place :D

ok, makes sense. But wont that wear out my snow tires from over inflation?

Quack
12-15-2005, 09:31 PM
not really, the cold reduces tire pressure, the colder it gets the lower the pressure in your tires, that's why you have to add more in the winter

King Luis
12-15-2005, 10:18 PM
look at rally cars when they race in the snow...the tires are probably as wide as your keyboard (short side).

Gamite
12-15-2005, 10:50 PM
not really, the cold reduces tire pressure, the colder it gets the lower the pressure in your tires, that's why you have to add more in the winter


but remember, if the tire is already very cold, it wont' go down in pressure, it will only go down with temperature changes. technically it should not go down that much since the air outside and the air within the tire will go down at similar rates.

vegabass
12-17-2005, 01:21 AM
but remember, if the tire is already very cold, it wont' go down in pressure, it will only go down with temperature changes. technically it should not go down that much since the air outside and the air within the tire will go down at similar rates.

alright, so can someone give me a PSI number to use _____ front and _____ back. That way i can set it, and maintain it at that level.

rico328i
12-20-2005, 07:22 PM
I personally run 32f 35r on my 328i w/winter tires. You may want to fool around with different psi's. It's a 'touch/personal' thing. Also depends on the particular tire you're using.

I have notice though in actual snow, 4cm + I definitely get better traction with a slightly lower psi. Again...I think it's a personal thing.

narrow tires in snow = more lbs/sq inch.

kidneykill
12-21-2005, 08:28 PM
I run 32 F and 38 r (Dunlop M3) on my 330ci, but my max load is 2 people.