Tire Pressure

[KTD]

This may be a stupid questions, but here goes . . .

My JD425 Garden Tractor has loaded tires. Is there any need to check tire pressure? If so, how do you do it?

 

[Bird]

What are those tires loaded with? If foam filled, no checking necessary. If liquid, then yes, sometimes the pressure may need to be adjusted. There are air/liquid tire gauges available at most auto parts and/or tractor supply houses. My preferred method is to start with the valve stem at the top (12 o'clock position), preferably, but not absolutely necessary, put a jack under the tractor and raise it enough to take the weight off the tire. And then I give mine a short burst of air from the air hose first to clear the valve stem of most of the liquid, then check the pressure and adjust as necessary.

 

[Gary_in_Indiana]

I'm confused. Wouldn't the tire pressure you gauge with a jack under the machine taking the weight off be notably less than the pressure with the tire bearing it's normal load?

 

[KTD]

Thanks for the reply Bird. The tires are loaded with a liquid. I didn't know that there were tires gauges that would measure the liquid filled tires.

 

[Freds]

What does clearing the valve stem with air before checking do? Isn't that why you use the air/liquid tire guage? I have to ask because my new tractor has loaded tires, but I don't have a compressor yet. /forums/images/graemlins/frown.gif
My tires were loaded with calcium chloride (and water I presume) and tubes were put in... does this have a bearing on your method Bird?

Thanks

 

[PineRidge]

Freds the initial burst of air clears the valve stem of any calcium chloride, this prevents damage to your pressure guage.

 

[JeffRey30747]

Pressure in a confined space stays constant as long as the volume of the space and the temperature stay constant and no more material is introduced into the space. True, deformation of the tire under load may change the volume of the space (inside of tire) enough to impact pressure, but I wouldn't think it would be enough to be significant. My opinion is that the volume would be fairly constant but removing the load just shifts more of that volume below the level of the valve stem, making for a less messy scenario overall.

Jeff

 

[Freds]

Thanks Mike. Looks like I'll have to get an air compressor. One would come in handy anyways.

 

[DiskDoctr]

Freds,

For around $20 or less, you can buy a portable air tank that you can fill at the local gas station (or friend's house) and carry to your place to fill up your tires. Can usually handle around 115psi.

Volume of air is limited, best for topping off tires, not so good for filling from flat (too many trips needed).

A quick, cheap interim solution until you get your compressor.

-JC

 

[Bird]

Gary, I won't try to get into the technical aspects of why the air pressure in the tire stays the same whether the tire is on the ground or jacked up, but it does; at least so close you won't know the difference. Did you ever notice when you have a new tire mounted, or a flat fixed, that they air it up to its required pressure before putting it on the car? And the main reason I prefer jacking it up is just so it doesn't try to push any liquid out. Probably not necessary; just my own preferred method.

Freds, I don't even know exactly what's different about the air/liquid gauges from the air gauges (stainless steel maybe?). They look the same and not much difference in price, but the ones made for liquid don't corrode like the one made just for air will. And it may not be "necessary" to give it a short burst of air first, but I just like to clear the valve stem and get as little liquid in the gauge as possible. I know if the liquid is nothing but water, it won't hurt the gauge, but I'm not so sure about calcium.