Tire inflation question

[Soundguy]

I air my lawn tractors up till they feel hard with my thumb pushed down on the tread / and / or when thy no longer squat down with me setting in the seat.

that's the end of that 'science' for me anyway... for my tractor tires.. i just look at profile with them on the ground / tire patch and air til they look right..


soundguy

 

[rabidracin]

I am going to assume the new tires have a higher max pressure because they are a higher ply tire. I personally would go with a little less air than recommended if that is the case.

Remember with no suspension, like on a tractor, your tire is your spring and only suspension, more air = higher spring rate, less air = less spring rate. Which would mean a stiffer ride with more bounce and is something i personally wouldn't want. Just my.02.

 

[Soundguy]

I'd kinda hope there is some sort of spring built into the seat too.. a fixed / solid seat would beat the heck out of ya. Not sure I've seen many that way that don't have air or springs in them.

soundguy

 

[zing]

No, that is NOT why it is there.
THAT is the pressure for the maximum rated load when cold.
If you are running at the maximum rated load your application is probably marginal.
If you are running at max pressure while not at maximum load you are almost certainly getting more tire slip than optimal, perhaps even tire hop when under load, & BTW wearing out the center strip more than you need to.

What you NEED is a set of load/pressure tables and a good understanding of what the loads actually ARE on your tires.

My tractor manual says:
- 18 pounds for muddy field work
- 24 pounds average use
- 40 pounds loader work
The side of the tires say "Max load 50 psi, do not exceed"

Personally, I prefer to just leave them alone because they are loaded, but I noticed the fronts were getting pretty low the last time I had something heavy in the loader, so I think they are going to need to be topped up. I definitely won't be filling them to 50 psi though.

 

[ModMech]

I'm going to get arguements on this but.....

I run the (turf) tires on our B2410 at ~ 8 psi for the Fronts and ~5psi for the Rears. I got that by understanding that there is a tire-load inflation chart, which I don't have, but generally you drop PSI relatively quickly but do not impact load capacity more than about 15% even with a 50% decrease in pressure.

Then I got the tractor (no loader ) all ready to mow and drove it over a patch of wet pavement and looked at the tread witness marks on the dry pavement. The tires were all 15 psi - 20 psi when I started and I just kept dropping the pressure until the transverse tread pattern was even. We have a "lawn" so soil compaction and tread marks are a big deal to us, lower tire pressure = lower ground pressure for a nicer lawn. Lower pressures are also easier on the sprinkler heads when you run them over

With the R1s on the rear, it is different because those are for TRACTON and the pressures are higher at about 15-18 psi. If I have the sickle on, the RR goes up to 20-22 psi or I can't get the bar off the ground

 

[krumph]

I have Massey 1260 on the front they are Bridgestone 4ply 212/80D15 pillow diamond that says max of 22 psi and the rears are Bridgestone 4ply 355-80D20 with a max of 14 and max of (50 psi for beadsetting) ? the thing that i have trouble with is since i got the tractor second hand i think they were always over inflated. after reading this post i put both sets at the max psi and they seem really under inflated now and drive really spongy. i even had a flat repaired at a garage last year and they over inflated the front to 29 psi also. is it normal to only have 14 psi in a rear tire of that model? the rear tires are loading by the way. if i inflate the rear to where the full thread is touching evenly on the ground i have to get the rear to about 19 psi instead of 14.

 

[Heavyduty]

I was wondering if you run your tires at 12 psi, would the actual weight from the tractor have a ground pressure of 12 psi? :confused2:

I've always been told that, by farmers when talking about soil compaction.

 

[paul314159]

I don't think it works that way. Ground pressure would be a combination of the weight distribution front to rear (I'm ignoring any side to side difference) along with the contact area of each tire. The contact area of the tire is dependent on the inflation pressure, but I don't think the contact area varies all that much unless you are way under inflated.

Paul

 

[RoyJackson]

I was wondering if you run your tires at 12 psi, would the actual weight from the tractor have a ground pressure of 12 psi? :confused2:

I've always been told that, by farmers when talking about soil compaction.

I don't think that's correct. The weight, per square inch, would be the tractor's weight divided by the total area of the tires' contact patches. That's really simplifying things though since the weight on the front tires and rear tires differ, as do the contact patches (due to the difference in the tires's sizes and weight distribution of the tractor).

I think what the farmers' meant was, by lowering the tires' pressures, the contact patches are larger hence less weight per square inch of patch hence less soil compaction.

Make sense?

The contact area of the tire is dependent on the inflation pressure, but I don't think the contact area varies all that much unless you are way under inflated.

Paul

Depends on how stiff the tires' sidewalls are...

 

[Reg]

I don't think it works that way. Ground pressure would be a combination of the weight distribution front to rear (I'm ignoring any side to side difference) along with the contact area of each tire. The contact area of the tire is dependent on the inflation pressure, but I don't think the contact area varies all that much unless you are way under inflated.

Paul

There are limits at each end, i.e. once it is "rock hard" another few psi won't change the contact area significantly, unless it blows it off.
Similarly, if it is so low that the rim is pinching the sidewall to the ground a couple of psi won't reduce the contact area by much.

Within the useful range pressure is close to weight/area.

Anyway, second guessing that we all are MASTERS at,,,; it still makes more sense to get the load/inflation tables, weigh each axle, do the table look up, adjust for special factors, then you KNOW you've done it RIGHT.