Topic: Proper Tire Pressures

[Carbon Sky]

From a bunch of trial and error, I tend to like my stock 245/45/18 Goodyear F1 GS-3 front tires around 28-29psi, and the rears about 1 psi higher.  I find it has the best balance of grip in the most conditions.  I run my winter 225/65/16 Nokian Hakkapellita RSi at 32psi and 33psi front and rear respectively.  And even then, it rides LOADS better.  But there's also loads more tire wall squirm.  But, it's also amazing in bad conditions.

[Carbon Sky]

I run 6psi in my 37" tires on my jeep.
The traction is amazing and I can literally crawl up rocks


I normally run 29-32 on the sky depending on the situation

Makes me think of mountain biking.  I run knobby, beadless (kevlar beaded so the tire can fold up), 2.5" tires on my hardtail with a big front fork at about 25psi on the trail.  Any lower and my nearly 200 pounds will bottom out the tire.  But I also run Micky Thompson 1.1" slick tires at 65psi.  It's a totally different bike just swapping the tires.  It suddenly becomes an amazingly fast/efficient urban assault bike.  You can jump down up to about 5 steps without issue.  I ride with cleats and clipped in to my pedals, so I can side bunny hop up a curb and get around vehicles when they don't leave enough space between them and the curb.  Yet it's super efficient, low rolling resistance, etc.  You just have to be more careful about things like drainage grates, and light rail transport tracks in the road.  But again, I just bunny hop as I'm rolling over them. 

[Sly Bob]

Tire manufactures don't recommend tire pressures generally.  They do tell you the max PSI that a particular tire is rated for, but that isn't a reccomendation.

I've been scared to find some people in the past that actually though that it was though.   

[Critterman]

Most people including the einstiens that work in service think that that is the pressure to run your tires at.  Very few look at the vehicles recommended pressure.  My truck runs 26 lbs on all four corners, If I take it in for any service I always check the tires.  35 lbs is what it is at 90% of the time.  It's like driving on ice.

[timlange3]

Normal air is 78.9% Nitrogen by volume so I'm surprised a 100% Nitrogen would make any difference.  Maybe it is more the lack of water vapor.

Did the base 2.4L cars come with different tires than the turbo cars, I thought they did, so would they have different recommended pressures?  I see more difference to handling due to outside temperature than to minor (couple pounds) pressure differences.

[DaveOC]

Normal air is 78.9% Nitrogen by volume so I'm surprised a 100% Nitrogen would make any difference.  Maybe it is more the lack of water vapor.

Did the base 2.4L cars come with different tires than the turbo cars, I thought they did, so would they have different recommended pressures?  I see more difference to handling due to outside temperature than to minor (couple pounds) pressure differences.

Yes, the NAs had Goodyear RSA tires while the turbo cars had Goodyear GS-2s.  Both used the same recommended pressure, 29 lbs.

[Sol Asylum]

Normal air is 78.9% Nitrogen by volume so I'm surprised a 100% Nitrogen would make any difference.  Maybe it is more the lack of water vapor.

Did the base 2.4L cars come with different tires than the turbo cars, I thought they did, so would they have different recommended pressures?  I see more difference to handling due to outside temperature than to minor (couple pounds) pressure differences.

From talking with the tire change guys at my dealership nitrogen doesn't make that much difference.  They were telling me that when the temps drop they will have a line of customers saying the TPMS is telling them they need to check their tires and add air.

When I used to work with the airlines one of the inspection items we had was to check the tire pressures each night on the aircraft and they were serviced with nothing but nitrogen.  Normal pressures were to be 125psi, if we checked the tires right after the plane landed they would be about 150 and if we did not service them but checked them later after they had cooled down 115-120 were normal readings.  Nitrogen is used in aircraft because it's dry and it has a safety benefit of not making fires bigger like compressed oxygen would.

The idea that nitrogen doesn't have a pressure change with changes in temps doesn't seem to go along with what I remember from chemistry class either.  I have had the ability to put nitrogen in my car tires for well over 15 years now and if I thought it would make a difference I would have but since I already have an air compressor in my garage it's just easier to use that.

[cdflint]

Would the same 29 psi be used on bigger wheel/tire set up? I have 275 35 19's on the rear and 245 45 19 on the fronts Conti DWS's. When they installed them they had at 32 psi. Watching on the guage it can go up to 35-36 but go back down.  I have not played with the tire pressure, just looking for a comfort ride on the street mostly.

[elff]

On the drive home from having new tires installed the Nitrogen gained 2 psi as the tires warmed up.
Which was pretty much what I see without nitrogen.
They also over inflated them and mounted the sensors out of order so I had to go through the relearn process.  No biggy, it's easy and detailed in the owners manual.

I didn't pay for it so I just humored them and let them inflate them

CDflint, I have mine set to 30 for my 275s and that hooked up real well and has a nice ride.
Fronts are 29.

[cdflint]

Cool thanks elff, I'll give it a go.

[Treeman]

Racers run nitrogen and it is to.get rid of the water vapor. We are talking about folks worried about half psi. Air is just fine for the rest of us slobs. I do have a water trap on my air compresser.

[JimmyBaja]

I have winter air in my tires right now @29 psi but since it's been so warm lately I'm thinking of switching to summer air@29 psi.

[elff]

You skipped fall air?????
Are you insane?
For the love of marshmallow fluff, do not
I repeat
Do not skip
Sping air

[JimmyBaja]

Why not¿ it's been spring pretty much all winter here.

[Critterman]

There is a formula on this site that I found on line for proper pressures when you change your tires.  I will see if I can find it.

[Critterman]

Okay found it

http://www.kappaperformance.com/forum/index.php/topic,4068.0.html

[ChopTop]

One thing I read years ago (and never knew), OEM engineers factor in original tire sizes/pressure when tuning the suspension.  Hence the reason that when some folks buy 20, 22, etc., rims, they discover they lose ride quality. 

Another way of saying it is a tires aspect ratio directly affects ride quality because a sidewall aspect ration is in a symbiotic relationship with the hardware suspension because metal rims don’t absorb/transmit energy like rubber.

Unless you consider bent rims as part of the process

[elff]

aren't rubbers supposed to prevent transfers??
 

[Critterman]

aren't rubbers supposed to prevent transfers??
 

Of fluids, not energy