Tire pressure - non runflats

[cowfish]

Hi, as you can tell by my posts I'm new (newly registered). Been reading these forums since December of last year. I appreciate all the great advice you guys take the time to put up so...thanks.

now, my question...

I just got rid of my RE050A II's and went with the non-runflat Continental extreme contact DWS. My car has the sport package with the staggered setup and I wanted to see what the dealership set my tire pressures at and to my surprise, it's set at 36 psi on all four tires. the label in the door as i'm sure you all know says 32 front/35 rear and that's where I kept the runflats at.

I was just looking for some input on this as maybe they know something I don't and set it up like that for a reason.I asked my SA and he wasn't too knowledgeable about tire pressures.


Thanks for any input and sorry for my spelling and punctuation. I'm in a hurry to get out the door.

[SilverBeam]

Go by what it says on the door.

[kornkid8600]

Door jamb

[Kevlar]

Start with what is says on the door and then adjust to your liking. I'm running 4psi over what it says on the door.

[robmpulse]

If the tires on the car are not the OEM tires, then the door is not accurate to what the tires should use. So if that is the case, DO NOT use what is listed on the plaque in the door jam. It may be accurate, but would only be that way out of coincidence. So it's best to just use what the tire says. You can also look up the air pressure specs online, too.

Start with the maximum listed on the sidewall of the tire. If that is too harsh, then let some out. 3 - 5 pounds less than maximum would be fine. Just adjust to your liking.

http://www.tirerack.com/tires/tires.jsp?tireMake=Continental&tireModel=ExtremeContact+DWS

The max inflation pressure for your new tires should be 55 pounds. Which I am assuming is MUCH higher than the stock tires. And running them in the mid 30's would cause them to be under inflated.....

[Kevlar]

Wouldn't the max inflation pressure be when the tires are hot?

[AshamedGorilla]

Wouldn't the max inflation pressure be when the tires are hot?
Maybe?


Either way, running at max is just that. MAX.
Most passenger tires (from my experience) say a max of 50-60psi. That's just a safety thing. It doesn't mean that's what you inflate it to.

I vote door jamb.

[TEPPSU]

Wouldn't the max inflation pressure be when the tires are hot?

Max tire pressure it the maximum amount you want to fill the tire at while the tires are cold. I would never set my tires at the max PSI.

I would go with what is on the door.

[bowmang]

just set it somewhere comfortable for you, within a good range... say 32psi-45psi. anything in there is safe, just make it comfortable.

like kevlar... i typically run 3-5psi over what the door jam says.

[samger2]

Yeah...I'm gonna re-iterate what was said...it's not recommended to run the tires at max pressure, doing that will insure that you have terrible ride quality and will cause the tires to wear unevenly. Again, max pressure is the maximum pressure the tire should have...not the suggested pressure.

In my 2010 tire guide it states that for a 2009 328i sport package you should have 32 up front and 34 in the rear...which is pretty darn close to what the door jamb will say.

[robmpulse]

After some online research, it turns out I was given wrong information a long time ago and I stand here corrected.

But this raises a hand full of questions. Depending on the make and model of the tire, the max tire pressure can differ drastically. Wouldn't 30 pounds pressure in a 55max tire be under inflated as opposed to 30 pounds in a 41pound max tire? At which point do you determine under inflation now? I was always under the impression that there was a 10 pound window starting at the max and going down. Which would mean using the vehicle's manufacture's recommended pressure of 32 in a max 51 would mean the tires are under inflated. ::shrugs::

Anyone have any input on this?

[kornkid8600]

Contact patch of the tire would tell you of you are over or under inflated.

Sent from my box of pancake mix.

[bowmang]

After some online research, it turns out I was given wrong information a long time ago and I stand here corrected.

But this raises a hand full of questions. Depending on the make and model of the tire, the max tire pressure can differ drastically. Wouldn't 30 pounds pressure in a 55max tire be under inflated as opposed to 30 pounds in a 41pound max tire? At which point do you determine under inflation now? I was always under the impression that there was a 10 pound window starting at the max and going down. Which would mean using the vehicle's manufacture's recommended pressure of 32 in a max 51 would mean the tires are under inflated. ::shrugs::

Anyone have any input on this?

the "max tire pressure" is simply an indication of how much pressure that tire can hold safely, and has nothing to do with how much SHOULD be in it.

when a manufacturer has a suggested tire pressure, it's because they tested the vehicle and suspension system and designed it to work with a certain tire and pressure. deviating from the stock tire can have an effect on this.. but it isn't enough to really worry about. when you have your tires filled to where they suggest, that will give you the best all around performance from the vehicle.. however, if you travel on the highway a lot, filling them a little more will offer slightly better fuel economy... where if you like to race around and have maximum grip, then a little less pressure is good for you.

normally, i will fill the tire to the suggested pressure, and then adjust up or down with a ~5psi range and set it right where i like it.... this certainly isn't going to damage anything.

so, basically, the "max tire pressure" has absolutely nothing to do with how much should be in the tire for driving, it is only the tire manufacturer saying "if you fill this tire more than XXpsi, it could be unsafe... therefore we're not liable".

hope that helps!

[SilverBeam]

There is definitely wiggle room on tire pressure. This fact is proven on the door, same tires, same tire size, different pressures from the rear. Less pressure makes the tire softer and makes for a smoother ride. Con: increased tire wear, increased chance of blow outs, reduced fuel economy. More pressure makes the car ride stiffer and sportier and increases fuel economy. Con: increased tire wear. You can do the old chalk trick to find out if your tires are inflated properly. Put a chalk line all the way across the tread of your tire and a little bit onto the side wall. Drive forward one rotation and check the chalk. If you have chalk left on the sides remove air. If there is chalk left in the center add more air.

http://www.tirerack.com/about/techcenter.jsp

Tire rack has 12 articles on tire pressure-- that is how important and complex it can be. I suggest you read into it in depth if you really want to know about it. If not, just set it to what it says on your doors and you'll be fine.