Tires Filled Tires

J_J · Jan 23, 2004

have you considered the fact that the rear tires, since they are filled, do not flex very much, where as the front tires that are not filled do flex and therefore the rolling radius of the tire changes. on a four wheel drive machine, the diameter of all four tires must be the same to function effectively. i would therefore jack up the rear tires and measure the center of the tire, and ensure that all the other tires are the same. you may have to run some tires at a different pressure to get equal diameter on all tires

same size tires from different manufactures may have a different rolling radius, and depending on air pressure may cause your back tires to working harder, and cause more stress.

j.j.

FOURTEEN · Jan 23, 2004

( The rolling radius of the tire changes. On a four wheel drive machine, the diameter of all four tires must be the same to function effectively.
j.j. )

The rolling radius of all tires changes as they move under various load and road conditions.

The horizontal diameter and circumference do not change. On geared 4WD vehicles the tires must be the same size (circumference). On a 4WD tractor with 2 size tires the internal gear ratios must be designed to allow all 4 tires to turn at the same speed.

The PT wheels are not geared together. Each is powered by a fully independent motor which is not influenced by the other motors on the PT. Each only "sees" more or less hydraulic pressure, and does it's work regardless of what may be happening to the other 3. (A 4WD SUV is like a boat with 4 oarsmen chained together - they must be the same size and work in unison. The PT is like a boat with 4 outboard motors - each one helps propel the boat, but is independent of the others.)

Charlie_Iliff · Jan 23, 2004

Filled tires are, by definition, mostly filled with incompressible liquid, so every shock is transmitted directly to the chassis. 

That's true, I suppose if you fill the tire completely. On ag tractors, we've always left a substantial air pocket, and some will claim that the best stability is to limit the fill to the axle line. For comfort and maximum traction on the turfs on my PT, I keep them very soft. 10-12 psi. I have considered going to 8 ply bar tires to avoid punctures, but the harshness and high spike loads are a bad side effect even without fluid.

J_J · Jan 23, 2004

it's ok to disagree, so here goes. yes, all the motors will try to run at the same rpm, given that all things are equal. now, let out half the air in one tire and notice the effect. for instance, i have a dixie chopper o turn lawn mower driven by hyd motors. if the tires are different diameters caused by leaking air, i have to compensate by adding more torque to the side with the low tire. i don't know if that explains my point. but i tried.

j.j.

FOURTEEN · Jan 23, 2004

Considering all these bad side effects, and already having full-time all-wheel drive, how much of an advantage are filled tires!??!

However, the judicious use of weigh can bring startling results. My 1976 14hp Power King 2WD tractor came from the factory weighing 850# with 8.00x16 AG rear tires. It often spun the tires when 48" mowing on lawn slopes or trying to push snow with the 48" dozer blade.

Completely filling the tires would have added 250#, but the tractor would ride like on concrete wheels. No thanks!

Instead I added: 2 steel wheel weighs of 135# each, a steel chassis weight below the frame of 130#, a steel 3 point hitch weigh of 70#, and a 50# steel scale weigh over the axle near the 1000AH car battery! The tractor now weighs 1400#, a 65% increase, with most of it centered (H&V) at the rear axle!!!

After studding the AGs with #6 hex head crown screws and dropping tire pressure to 7#, the Power King is **** near unstoppable for a 2WD! Wet grass, mud, ice, snow, slippery logs, and steep slopes (forward 25 degrees on dry loose clay)can be laughed at! Plowing into a snow bank at the end of our hard-packed snow covered parking lot in high gear, the Power King would actually slip it's clutch rather than spin a tire! Comfortable ride with a big footprint that is gentle on dry clay grass is another plus.

If my new PT-425 runs out of traction, or wants to lift it's tail, I will carefully consider all my other options before filling the tires.

PS: Based upon the new Power Trac Product Catalogue, "PT-425" and "Power Trac" are correct - not "PT425" and "Power-Trac". But then again, "catalogue" is used for the more common word "catalog"! Strange, but true!!

Charlie_Iliff · Jan 24, 2004

Considering all these bad side effects, and already having full-time all-wheel drive, how much of an advantage are filled tires!??! 

I don't think any of us can answer that question. Davesisk has fluid in the rears on his, but he's the only one I know who has it. I don't know that he's run without it to compare. Dave? I've had times with the 1845 where I needed more traction, but I'm on turfs with no added weight on the tractor. Most PT users have found pretty impressive traction without any modifications.

FOURTEEN · Jan 25, 2004

( Most PT users have found pretty impressive traction without any modifications.
)

My point exactly! It may be foolish to always wear suspenders just because someday your belt may break!

If someone often gets themself stuck, or lifts the rear wheels, if may be just "operator error"!
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