Tire pressure

[MOFSTEEL]

So for stock tire size I know to follow the tire pressure listed on the inside of the drivers door.
...but what is proper for a 235/35/19 tire for everyday driving?

[VR2V8]

Your tires aren't marked with the proper pressure?

[MOFSTEEL]

Your tires aren't marked with the proper pressure?

I believe all tires are marked with a "Max" tire pressure.
This certainly isnt optimal for everyday driving.

[nimski62]

35-38

[Stevelev]

I'm running 40 lbs. Obviously track pressure would be lower (cold)

[DRYBONES]

I run 39psi. These cars are quite heavy and the higher tire pressure helps with fuel economy and as a plus the car feels more firm and planted...less sloppy on turns.

[WinterRunner]

i run 40 up front, 38 in the rear. MAkes the car feel less sloppy like ^^ he said.

[snowbird]

Your tires aren't marked with the proper pressure?

You should NOT be running maximum pressure, which is what is marked on the tires. That pressure is used to seat the tires when installing only. The tire actually says that right on the side wall as well. Furthermore, tire pressure depends on the vehicle, not the tire.

One downside of running a tire with too much pressure is premature wear down the centre of the tread patch. An over-inflated tire will balloon out slightly, putting more pressure down the centre of the tread.

I run my 235/35/19's on the high-side of the recommended inflation pressure stated on the door jamb label.

[Stevelev]

...I run my 235/35/19's on the high-side of the recommended inflation pressure stated on the door jamb label.

My door jamb states 44 lbs

[Audi Advocate]

38 gives great handling while saving the sidewall for track days.

http://i70.photobucket.com/albums/i9...cate/11719.jpg

[Mark@STaSIS]

Would somebody be so kind as to take a picture of their door jamb sticker of their B7 S4, preferably sedan and post it here?

Thanks in advance!

Mark at STaSIS

[gunxit]

[Louis J.]

Firstly, tire size has nothing to do with tire pressure. Tire pressure has to do with overall weight and weight distribution of your car.

Secondly, there is no right or wrong tire pressure. Tire pressure should be tailored to one's specific car and driving style. For example, if you want fuel economy, around 40psi cold all around is a good number (heat typically increase pressure by ~10% so you would net ~44psi hot, which is the recommended pressure). If you want handling, ~37psi cold provides a nice balance between increased grip within normal tire wear range. Tire pressure can also change handling characteristics and dial understeer or oversteer in or out. For our nose-heavy, understeer happy cars, higher tire pressure in the front can dial out understeer and make the car more neutral.

Personally, I run 41F/39R cold for street, 39F/37R cold for autox or track when wet/cold and 37F/35R cold for autox or track in warm weather. I say this because if one prefers performance over fuel economy for street driving, the lower tire pressures will work better. I have a 2.0T with a rear RS4 sway so I would increase the variance between front and rear on an S4 with stock sways as such car would probably understeer more than my car.

I think tire pressure is often neglected and its critically important both in terms of fuel efficiency and handling. Experimenting with tire pressures helps determine what works for one's particular needs and driving style.

[i_eat_staples]

Firstly, tire size has nothing to do with tire pressure. Tire pressure has to do with overall weight and weight distribution of your car.

Secondly, there is no right or wrong tire pressure. Tire pressure should be tailored to one's specific car and driving style. For example, if you want fuel economy, around 40psi cold all around is a good number (heat typically increase pressure by ~10% so you would net ~44psi hot, which is the recommended pressure). If you want handling, ~37psi cold provides a nice balance between increased grip within normal tire wear range. Tire pressure can also change handling characteristics and dial understeer or oversteer in or out. For our nose-heavy, understeer happy cars, higher tire pressure in the front can dial out understeer and make the car more neutral.

Personally, I run 41F/39R cold for street, 39F/37R cold for autox or track when wet/cold and 37F/R cold for autox or track in warm weather. I say this because if one prefers performance over fuel economy for street driving, the lower tire pressures will work better. I have a 2.0T with a rear RS4 sway so I would increase the variance between front and rear on an S4 with stock sways as such car would probably understeer more than my car.

I think tire pressure is often neglected and its critically important both in terms of fuel efficiency and handling. Experimenting with tire pressures helps determine what works for one's particular needs and driving style.

i do 41F/39R cold for the street as well, although I'm still playing around with settings for tracking

I did 47 hot for all 4 corners for my last event, but even that seems too high

[Louis J.]

i do 41F/39R cold for the street as well, although I'm still playing around with settings for tracking

I did 47 hot for all 4 corners for my last event, but even that seems too high

I hope you meant 37 and not 47 hot; that's just way too high. You want to go lower, not higher for track or spirited driving.

The type of tire makes a big difference in how much and how quickly the tire heats up. Generally speaking, the higher the performance tire, the softer the compound and the faster you can get heat into the tire whereas all-seasons for example will take longer and may not get quite as hot. Make sure you not only check and set tire pressure cold but that you also monitor tire pressure as you get heat into the tires.

[i_eat_staples]

I hope you meant 37 and not 47 hot; that's just way too high. You want to go lower, not higher for track or spirited driving.

The type of tire makes a big difference in how much and how quickly the tire heats up. Generally speaking, the higher the performance tire, the softer the compound and the faster you can get heat into the tire whereas all-seasons for example will take longer and may not get quite as hot. Make sure you not only check and set tire pressure cold but that you also monitor tire pressure as you get heat into the tires.

nope, 47 hot is what i ran on all 4 corners...i havent been able to get a good idea of what temp i should be running on the track (hot). I've heard most everyone is in the 40s. I have 18" kdw2's i use on the track.

You mentioned you run 37 F/R cold for the track in the dry? What hot temps do you try and run at?

[Louis J.]

nope, 47 hot is what i ran on all 4 corners...i havent been able to get a good idea of what temp i should be running on the track (hot). I've heard most everyone is in the 40s. I have 18" kdw2's i use on the track.

You mentioned you run 37 F/R cold for the track in the dry? What hot temps do you try and run at?

I think you're running a bit high. Lower tems, within a reasonable degree, provide more traction because you increase the load on the tires and by doing so, you make the rubber more malleable and sticky to dry roads. I have to emphasize WITHIN REASON again because if you go too low, say 30psi on our cars, the tire will simply slip too much and you'll loose traction. This also does not apply to wet surfaces, which is why higher pressures should be used for wet conditions. At 47 hot on dry climate, your tires are not optimizing traction.

I just corrected my post...I run 37F/35R cold which puts me at about 40/38 hot with my tires, though I'm still playing around with temps as I just bought new tires last month and have only done one solo1 and two autox on them. Also, the RS4 sway was installed two or three weeks ago so I'm still adjusting my pressures.