Tires Loaded Tires & PSI

[snmhanson]

Probably a dumb question but I'll ask it anyway. Do loaded tires have the same PSI reading as unloaded tires? In other words, say I have tires speced for 20 psi. If the tires are loaded should they still be inflated to 20 psi or does the material inside them effect the pressure? It seems to me that the PSI would be the same regardless but it never hurts to ask.

Matt

 

[KiotiJohn]

You still put in the same PSI. John

 

[timb]

I think there have been some discussions here where there might be a point to running a little different pressure than an unloaded tire - but most folks I've talked to say they've always kept them the same.

Just make sure you're checking the PSI with the valve stem at 12 o'clock!.

 

[KiotiJohn]

I should have gone into more detail with my answer. The long and short of it is that it matters whether you have radials or bias ply tires. In general, it's recommended that you not use liquid ballast in radial tires as it tends to make them stiffer.
For bias ply tires, some recommend 1-2 PSI higher than the stated maximum. Here's a link to a Firestone article on the procedure that should answer most of your questions. John
filling tires

 

[Henro]

I run my loader rear tires at about 12 PSI. I had not checked them for a while and a month ago they seemed kind of soft...and I think they were at something like 6 PSI...

One thing to keep in mind is that with fill in the tire the air bubble is smaller, and when the tire deforms pressure increases faster inside than it would if the tire only had air in it. So it may make sense to carry a little less pressure in the tire than you would if you only had air in it, if the tire is loaded with liquid.

Now my front tires are foam filled...wonder what pressure that equates too... /forums/images/graemlins/confused.gif

Lower pressure in my mind equates to better traction to some degree, since the tire contact patch would be greater if the tire flattens a bit on the bottom. I think the reason I started running lower pressure was because I got the impression from other posters here that lower pressure and tire deformation was gentler on the grass. But since then I have stopped using the tractor for mowing...but then again, I still have to get on the better part of the yard now and then, so I have not changed my practice any with respect to tire pressure...

 

[KiotiJohn]

A couple of the tire articles I read in the last few stated that running RADIAL tires at correct/low pressures is a good thing. All of the articles stated that running bias ply tires low is bad for the tire. Radials will have that cheeky look when at the correct/low pressure and will increase the footprint on the ground. John