Tire Pressure -- real world

[Wade]

Just got my new rig back from the tire shop. Not sure that it is fair to blame them as I made a special point of having them install steel stems for the load range D tires due to their higher than auto pressure. (I have since found out that they actually make rubber stems designed for higher pressures.)

One thing that no one ever talks about in regards to air pressure is how do you measure it?  I remember being at a Tire shop one day and asking if I could check my tires.  They gave me a hose with a really fancy Snap On digital gauge.  (I know it is fairly common for people to be concerned with older push rod gauges as they wear or get dirty causing the rod to slide with more difficulty and giving inaccurate readings.)  In any case, their gauge was 5 psi different than my digital gauge, one of my dial gauges and about the same as another one of my dial gauges.  (I only had one gauge with me at the time.) Later I came back as I wanted to test against my other gauge again. This time they gave me another high end analogue dial gauge and it agreed with the other one of my gauges.  I asked them how they could live with two different gauges giving readings that were 5psi off and that is where their goodwill to me ended;-)  Never did get an answer.

I would challenge anyone to demonstrate to me that there isn't at least 5psi variance in measurement across a wide variety of gauges. This is one of the many reasons I tend towards the higher end of the max sidewall PSI  (Usually about 5psi or a little more short of max.) rather than the vehicle ratings.  If the vehicle is rated at 34 psi and my gauge is off 5 high, then I actually have only 29 psi and then if it is loaded heavy on a hot day...

Got my RV back from the tire shop with new tires and brakes last night. This afternoon, about 80 degrees truck parked overnight, I tested the air pressure using my dial gauge. On the top pic below I measured 70 psi!  I would like to think that they set it at 65 on their gauge. The next picture, with the leaf in it, is the tire at 56 psi in my gauge. This is where I intend to start running it and adjust from there. I am new to this thing and I am not sure where I will end up. As I have repeatedly said I tend to run has high as i can, with a little breathing room at the top, for better mpg.  I will consider going lower and certainly will go lower if I don't like the way the truck preforms or if the tires are not wearing evenly.

On a perhaps related note, my truck is the 22RE with 4spd manual and MANUAL steering.  What a hoot!  I think I would have to go back to the '70s to remember the last time I owned a vehicle without power steering!  Frankly I really like it!  Perhaps if the fronts were down to factory PSI I might notice it?  From the little I have driven it so far I am very happy with the steering. I am also grateful that I won't have one more fluid to change or leak to fix!

The last time I mentioned this in another thread someone asked for people to share where they run their PSI. I would like to ask that again and perhaps pictures of where your tires ride.

Wade

 

Edited June 16, 2016 by Wade

[fred heath]

As I remember from years ago, tire pressure should be set when the tires are cool.

Obviously, as the tire heats up either from friction or ambient temperature, the air pressure will also rise.

[zero]

31 minutes ago, Wade said:

 

I would challenge anyone to demonstrate to me that there isn't at least 5psi variance in measurement across a wide variety of gauges.

Without power steering!  Frankly I really like it! 

Wade

 

I have a  high-end gauge calibration tool that I use to verify PSIG on my hydraulic gauges.   Works just as well on gauges used for air pressure.  Yes, pretty much all the ones I've checked vary, especially at lower pressures.  Once at 50 PSIG or over, not all that much.   I'm am sure that tire and vehicle manufacturers are well aware of the inaccuracy of pressure-gauges, as well as tire-temps or  changes in atmospheric pressure when readings are taken.  Thus there is a lot of lee-way.  I have an analog truck-gauge that goes to 120 PSIG and it is dead-on at 50 PSI.  Not that it is something I worry about too much. 

My Chinook with a 20R has manual steering.  It steers fine but it's light.  If there was a way to put power-steering in, I would. No such thing for a Toyota truck in 1978.  Besides the power-assist, I like the way power-steering stops feed-back from a front wheel to the steering-wheel when a pot-hole or rock is hit.

[Wade]

6 minutes ago, jdemaris said:

II have an analog truck-gauge that goes to 120 PSIG and it is dead-on at 50 PSI.  Not that it is something I worry about too much. 

My Chinook with a 20R has manual steering.  It steers fine but it's light.  If there was a way to put power-steering in, I would. No such thing for a Toyota truck in 1978.  Besides the power-assist, I like the way power-steering stops feed-back from a front wheel to the steering-wheel when a pot-hole or rock is hit.

I try to always measure tires cool. Says so right on the tire;-) Obviously you can't always do that on the road.

Guess I am making a somewhat bigger deal out of it here than in the real world. I am mostly concerned with wear and consistency between tires.  I don't worry about the precision either and I would guess that while you don't worry about it, you do likely check for consistency?

IIRC, you said you run your rears at 45. Where do you run your front and do they lie much flatter than my pics above? Does the lower pic look "crazy" over-inflated to you? (Front wheel FWIW.)

Interesting note about steering feedback. I'll put up with that for system simplicity at this point. Am a bit overwhelmed at everything I need to do to get my Toy the way I want it.

[zero]

1 minute ago, Wade said:

I don't worry about the precision either and I would guess that while you don't worry about it, you do likely check for consistency?

IIRC, you said you run your rears at 45. Where do you run your front and do they lie much flatter than my pics above? Does the lower pic look "crazy" over-inflated to you? (Front wheel FWIW.)

Interesting note about steering feedback. I'll put up with that for system simplicity at this point. Am a bit overwhelmed at everything I need to do to get my Toy the way I want it.

I calibrate my gauges mainly because I have a lot of heavy equipment that runs at 8-10 PSI.  Little room for error, especially with tires that are often 40 years old.  People have been killed by putting 50-60 PSI in a farm-tractor tire rated for 8-15 PSI.   My pickup truck runs 80 PSI in back and at that sort of high pressure - I also like to know I'm pretty close.  As far as how my tires sit? I'll take some photos later but I think mine squat more then your's. They are supposed to.  Called the "loaded radius."

Power-steering became pretty much standard equipment years ago in full-size 4WD trucks mainly because of the feed-back issue. If you have ever been in the woods, hit a tree stump, and near broke your hand with manual steering - you'd be eager to have power.  Not so common an issue on a paved highway.

I think one of the last full-size trucks sold in the USA with 4WD and manual steering were the Dodge Power Wagons made up to around 1971.  No power steering option available and they were horrible.
No power steering option on 70s Toyota pickup trucks either but none of them had 4WD.  I tried to engineer some power-steering into my 1978 Chinook and gave up.   It is fine and easy to steer most times.  Once in awhile when stopped the "arm-strong" steering system gets to me.  But both my shoulders are completely worn out, so that's a personal issue. I recently gave my son my diesel Dodge pickup because I could no longer shift it, due to my right shoulder.   I can drive the stick-shift fine with my Toyota Chinook.  But that Dodge with the German 5 speed trans is murder and I had days I had to reach over and shift with my left arm.  I was scheduled to go in the hospital two years ago for new shoulder joints - but I keep chickening out.

[Wade]

LOL! one of the vehicles I was thinking of was a 72 Dodge power wagon.  Forgot about what it was like hitting something off road till you mentioned it. At least that thing had a giant steering wheel to help you manage it!  It was only a 2WD but the base model. Sure they probably sold it with power steering by then. Sorry to hear about your shoulder.  Look forward to seeing your pics and hopefully the actual PSI.

Wade

[zero]

1972 was the first year of the "new generation" Dodge truck.  Very different from the 1971.  1972 had a major change in the steering geometry that allowed power steering in the 4WD just like Chevy had at the time.
I think that "new" 1972 design stayed near the same all the way to 1993 when Dodge finally did a big revamp again.

[Wade]

Ours had the rather bullet proof 225 slant six. I remember putting a long block in 79.  Don't remember why;-) 

Perhaps it was the really long gearing of the 3 on the tree?

Interesting that motor put out something less than 20hp compared to the 22re.  The 22re really is a great piece of engineering.

Thought you might get a kick out of this:

http://www.performancesimulations.com/wp/fact-or-fiction-tire-contact-patch-size-is-determined-mostly-by-weight-and-tire-pressure/

 

Wade

[DanAatTheCape]

I run my rears at 65 (max for class D)   I use a tire gauge like this  http://www.autozone.com/tire-repair-and-tire-wheel/tire-gauge/slime-10-120-psi-dual-head-pencil-gauge/513701_0_0/?checkfit=true

 

I can check my front tires with this.       As for calibration, I compare my tire gauge whenever I can.   A lot of inflator heads have a built in gauge. 

I also keep one of these http://www.autozone.com/air-tools-and-accessories/air-chuck/vaper-dual-tire-chuck/125074_0_0/?checkfit=true

with me -  I have put it on many times at inflator stations as they often do not have a head that works on my vehicle.  Before I carried an extension hose but that was a hassle.