What tire pressure to run?

Status
Not open for further replies.
Joined
Nov 23, 2016
Messages
1,732
Location
WI
Feels like I've been posting a lot in this section lately... oh well, I'll try to stop eventually.
smile.gif


Walmart put 35PSI in my new tires (245/75/16 Hankook Dynapro ATMs, P rated). Does that sound about right for my Liberty? Weight wise I'm guessing it's probably around 4600-4800 lbs once you add in the winch, skid plates and rock rails. Door sticker is irrelevant at this point, I think, not a factory size. I'd do the chalk test but I'd have better luck playing pickup sticks with my butt cheeks than finding a dry section of pavement here for awhile.
smile.gif
 
My G.C. recommends 33/36 psi front/rear in 265/50R20's. Never heard of such a thing! What is the point of a 3 psi difference between front & rear?
 
What is sidewall max PSI?

I'd probably run the fronts 4-6 PSI higher than the rears. The rears, primarily transmitting power to the ground, will have a tendency to wear in the center, where the fronts will tend to wear on the sides from doing the steering. The fronts also carry a bit more weight.
 
The door sticker isn’t for the dry stock weight of the vehicle, it’s for the max loaded point of the vehicle too.

But I usually add a couple PSI. 36 psi in the Jeep and Sonata.
 
Originally Posted By: das_peikko
35PSI is the standard that most tire shops go by.


Interesting. I worked at a tire shop for a little bit and we went by the door sticker as it varied by type of vehicle. As a general rule at least
 
I wish a published list were available of tire psi BY POUNDS OF LOAD each tire carries!

My F150 is very front heavy, so gets more PSI in front tires, than in back.
 
Originally Posted By: Aero540T
I worked at a tire shop for a little bit and we went by the door sticker


I have never ever seen a tire shop guy look at the door sticker.

35 psi is VERY common
 
I want to say max is 44. It's 0 degrees out so that's my best guess.

I would run different pressures front/rear but the tcase would pitch a fit, they have to be within a pound or two of each other for it to shift in/out of 4WD smoothly.
 
Originally Posted By: Linctex
Originally Posted By: Aero540T
I worked at a tire shop for a little bit and we went by the door sticker


I have never ever seen a tire shop guy look at the door sticker.

35 psi is VERY common


I don’t disagree. And it wasn’t every vehicle as you start to figure it out. Most passenger cars were 32 if I remember correctly.
 
My Hankook tires are rated at 51 PSI my car calls for 34 PSI. I run them at 40 PSI. Better MPG more than 0W-20 ever gave me. About a mile per gallon in town and a 2+ MPG increase on the open road.
 
Originally Posted By: das_peikko
35PSI is the standard that most tire shops go by.


This.

When I first started airing up tires, I went by the door sticker. In a busy shop environment, you'd be surprised at how time consuming that can be. Some cars don't even have the sticker, or the numbers are illegible. For a myriad of nuance reasons, 35 PSI is a standard.

Now, some cars, like Corolla's, I can remember being around 32/33 PSI front and rear. If I notice I'm working on one of those, I'll put in 33 PSI. But I also realize that so many tires I work with, are being driven by a person who doesn't make it a habit of checking the air. So I end up putting 35 PSI in anyway, knowing it's better for the vehicle to be a tad over recommended PSI than being under; especially when MPG's are more important than handling, for most.
 
Last edited:
Originally Posted By: JohnnyJohnson
My Hankook tires are rated at 51 PSI my car calls for 34 PSI. I run them at 40 PSI. Better MPG more than 0W-20 ever gave me. About a mile per gallon in town and a 2+ MPG increase on the open road.


When I do tire pressure checks, I sometimes ask what a person wants to run in their tires for this very reason. 40 PSI is pretty high for a Corolla, but if that's your preference and you've seen a good reason to do so, then 40 PSI it is.
 
I generally fill all tires to 38-40 psi due to the fact that most people never check their tire pressure unless a light comes on, and the fact that tires constantly lose a small amount of air at all times. I put 4 new tires on an older Civic for a friend that was on hard times a couple of years ago and just saw her car again after all this time. I knew I had put in 38-40 psi as usual when the tires were new. The car was back this time for worn-out front brake calipers (252,000 miles on originals. Now she has a job and has money to pay for the work.) Anyway, all of the tires had 18-19 psi in them. Surprisingly, they were not worn badly on the edges. I told her she needs to check her tire pressure and keep filled for the obvious reasons.

If you put in what the door sticker says, you are already low on air pressure, IMO.
 
Originally Posted By: bmwtechguy
I generally fill all tires to 38-40 psi due to the fact that most people never check their tire pressure unless a light comes on, and the fact that tires constantly lose a small amount of air at all times. I put 4 new tires on an older Civic for a friend that was on hard times a couple of years ago and just saw her car again after all this time. I knew I had put in 38-40 psi as usual when the tires were new. The car was back this time for worn-out front brake calipers (252,000 miles on originals. Now she has a job and has money to pay for the work.) Anyway, all of the tires had 18-19 psi in them. Surprisingly, they were not worn badly on the edges. I told her she needs to check her tire pressure and keep filled for the obvious reasons.

If you put in what the door sticker says, you are already low on air pressure, IMO
.


I would have disagreed 4 months ago. Now, having been a tire guy for a few months, I 100% agree.
 
Originally Posted By: HoosierJeeper
Feels like I've been posting a lot in this section lately... oh well, I'll try to stop eventually.
smile.gif


Walmart put 35PSI in my new tires (245/75/16 Hankook Dynapro ATMs, P rated). Does that sound about right for my Liberty? Weight wise I'm guessing it's probably around 4600-4800 lbs once you add in the winch, skid plates and rock rails. Door sticker is irrelevant at this point, I think, not a factory size. I'd do the chalk test but I'd have better luck playing pickup sticks with my butt cheeks than finding a dry section of pavement here for awhile.
smile.gif


Walmart did right with 35 psi. No worry.
 
This is a 4 wheel drive, so conditions indicate what the pressure should be ... Sand, maybe 15 psi. Rocky trail, maybe 36 PSI. Desert trials, maybe 28 PSI. Highway, whatever gives you even tire wear across the tread area.

BUT, 4x4's are different from FWD or RWD in that they bind if the rolling diameter is off. So you not only carry a tire pressure gauge, but you carry a tape measure. You air up the fronts to whatever the driving conditions are - let's say highway at 36 PSI.

On a clean dry level surface like a parking lot, you measure from the ground to the upper lip on the front wheel rim. Say it's 20". Now you inflate the rears so you get the same 20". Pressure makes no mind. You must be at rolling the same dia ...

With nothing in the back - it could be 26 PSI. Or with the back full of camping gear, it could be 34 PSI. As long as it's the same rolling dia, it'll shift into and out of 4x4 on the fly with minimal bind. Get them off and you'll have to stop and back up to get it to unlock ...

On 4x4's you must learn to manage the pressures for the conditions at hand, and there will be a difference between front and rear because of vehicle loading, engine weight, etc.
smile.gif
 
Last edited:
Broc, I disagree...the tiniest difference will lead to wind-up, as does the Ackerman effect on the steering, which means that all the tyres run a different number of miles in any single trip.

Only technique that I've found for all the variables is to take an engineer's 6" rule, and slip it in between the tread and the concrete as you pump the tyres.

about a half inch of peneetration seems to give fairly even wear...too much penetration, and there's too much pressure. Too little, and there's not enough. As you drop the pressure, you can see how hard the edge is to lift, as the centre of the tread "pops" upward with no contact pressure really at all.
 
Status
Not open for further replies.
Back
Top