[fxie]

Hey guys, I'm currently running 34/40 psi on my winter square setup of Dunlop Winter Maxx tires. Since its a square setup, should the tire pressure be the same for both front and back? What would you guys suggest as the optimal tire pressure for winter driving?

[pikcachu]

Manual recommends 32/38.... square or not has nothing to do with it I think....
Also doesn't matter the season either... you should keep at the same pressure... although if you pump say 32 in summer and don't adjust that might drop to 27 in winter

[Wheelwright]

I asked my shop to use 40psi all around on my Dunlop Sport 4Ds. This way they are less squishy and don't harm handling too much. Also I don't have to check pressure often because the initial pressure was high.

[overcoil]

What's your tire size ?
Do they match a tire in the owner's manual
# your running now seem good, the higher rear numbers are probably due to the cars power,

[moltenfire]

Am I a geek, or does anyone else use the ideal gas law (PV=nRT) to calculate the correct tire pressure when measuring tire pressure in the winter?

[Killramos]

Originally Posted by moltenfire

Am I a geek, or does anyone else use the ideal gas law (PV=nRT) to calculate the correct tire pressure when measuring tire pressure in the winter?

I think its just you.

Unless you fill your own tires with 100% Nitrogen and have figured out a reliable way to factor in changes of stretch of the tires and rims as per temperature and pressure .

Its far from a constant volume system.

[caycep]

Dumb question - do you leave it lower in the winter with the assumption that when the tire gets hot, the hot pressures will be similar? Or fill it up to recommended spec cold?

[overcoil]

Originally Posted by caycep

Dumb question - do you leave it lower in the winter with the assumption that when the tire gets hot, the hot pressures will be similar? Or fill it up to recommended spec cold?

Fill up to door jamb/ owners manual specifications. If your atmosphere temp varies widely so will your tire temps. So in winter don't fill air during warmest part of day or on tire's up to temp through driving. It's cold tire's when you set pressure.

[AlpsRider]

I've settled on 35/36.5 with just me in the car or with 1 passenger, no luggage.
That is checking the pressure first thing in the morning in the unheated garage where the sun doesn't shine on the tires. At that pressure, the front tires feel more crisp and get less corner wear (which I think is a problem with the stock 235). The rears have less wheel hop. The tires heat up nicely and the front to back pressure ratio stays where I want it to be. At 32 in the front they get hot. I've read that having the front and back pressure more even decreases understeer. In Europe they apparently recommend the rears have lower pressure than in the US, I can see why. All bets are off when the outside temperature changes, they'll need to be checked again.

[neilr_]

I've got a similar/related question.

My wife's mechanic says the doorjamb labeled recommended pressures are for the OEM tires (the specific tires, not just the size) and that replacement tires should be cold inflated to the value on the tire. This is news to me - I've always gone by the doorjamb label.

Related to this, I'm running Continental WinterContact Si (225/45R17) tires. The value on the tire is 51psi; the doorjamb label says 32 front, 38 rear; the manual says 32/33 for 225/45R17 OEM tires.

Currently, my 228 says the tires are all at different levels between 32 and 34, so I think I need to do something. The question is what. Our temperatures are between ~30F overnight and ~40F mid-day.

Advice?

[overcoil]

^^^^
Pretty sure tire sidewall is maximum allowable/recommended PSI for the tire before any application by a car manufacturer to a vehicle - and the door jamb pressure is calculated for tire size and weight of the vehicle as determined by an individual car manufacturer.

The owners manual would be the source to find tire pressure of a different size for your model.

[pikcachu]

Originally Posted by neilr_

I've got a similar/related question.

My wife's mechanic says the doorjamb labeled recommended pressures are for the OEM tires (the specific tires, not just the size) and that replacement tires should be cold inflated to the value on the tire. This is news to me - I've always gone by the doorjamb label.

Related to this, I'm running Continental WinterContact Si (225/45R17) tires. The value on the tire is 51psi; the doorjamb label says 32 front, 38 rear; the manual says 32/33 for 225/45R17 OEM tires.

Currently, my 228 says the tires are all at different levels between 32 and 34, so I think I need to do something. The question is what. Our temperatures are between ~30F overnight and ~40F mid-day.

Advice?

The 51 on the tire is the max cold temp you should ever inflate it

You should NOT inflate your tires to 51

Your mechanic really has no idea
Use whatever the door jamb says

[AlpsRider]

Originally Posted by neilr_

I've got a similar/related question.

Currently, my 228 says the tires are all at different levels between 32 and 34, so I think I need to do something. The question is what. Our temperatures are between ~30F overnight and ~40F mid-day.

Advice?

I wouldn't trust the car's pressure readings. They are usefull as a rule of thumb but they are not accurate. You should check the tire pressure in the morning before driving the car and preferably away from direct sunlight. Sunshine on black tires heats them up more than you'd imagine resulting in increased pressure. Get a good tire guage, I bought a digital guage on amazon for around $20., then air up the tires at the gas station to about 40 psi, go home and check the pressure in the morning and let the air out to achieve your desired pressure. Tire pressure is one of the most important vehicle parameters that are within your control.