HST or gear drive ?

[MChalkley]

Gordon - I think the modern-day farmers are finally coming around on this one but, historically, tire pressure has been the number one mistake they (and tire dealers, especially) have made. When I got my Michelins the tire dealer said I needed to run the rears at 35 psi. I mentioned to him that these things weren't on a 25,000 lb Cat TLB, but a 7,000 pound Kubota. (If I recall correctly, the tractor with 2,000 backhoe attached and as much as I can lift in the loader wouldn't overload one tire at 35 psi, much less spreading it over four tires.) He said it didn't matter, but agreed to lower them to 30. When I got home, I lowered them to 9 psi. The correct pressure for them would be 7-8, but Michelin won't let you run them that low...

MarkC

 

[Von]

Mark,
I'm running 8 psi in my rear loaded turf tires on my B2710, and they still have too much air in then. The tread is still not touching on the outsides. I run 22 psi in the fronts for the loader.

 

[radman]

DaveV,
To determine actual ground speed many large tractors use radar to determine true ground speed and not GPS. The radar in combination with what the transmission determines as its speed can determine the % wheel slippage.

 

[glennmac]

Mark, you have for some time advocated lower tire pressures than others might recommend. Could you share with us your authority for your views. I take it your views are not specific to radial tires, or are they.

 

[MChalkley]

Glenn - Well, what you say is true, but my opinions, in this case, are not my own. What I advocate is that you use the pressure recomended by the tire manufacturer for your weight. (Well, the tractor's weight, that is. But including your weight, of course. /w3tcompact/icons/laugh.gif) What you have to do, assuming you don't want to "air up" and "air down" depending on what you're doing and/or which implement you're using, is figure out what situation would create the maximum weight for that particular axle, divide by two, and inflate the tire to the pressure recommended for that particular load.

This gets a little tricky for the front tires because they are a lot smaller. Remember your physics? It's technically not the air pressure that supports the load, but the volume of the air. That's (the main reason) why a bigger tire will hold the same load with a lot lower pressure. Anyway, for front tires, imagine you have the maximum load you can lift in the bucket with no implement on the rear. (Don't do it, just imagine it. /w3tcompact/icons/smile.gif). Then imagine you stop too quickly. Hopefully, you remembered your safety rules about carrying the load low and wearing your seat belt (especially since you didn't remember the one about appropriate rear ballast). What happens? All of a sudden the front bucket is on the ground, the rear tires are off it, and you've come to a sudden stop. How much weight is on your front tires during the time between when the rear tires came off the ground and the bucket hit? You got it: the whole tractor, plus the whole load. Ouch!! So, it's best to run the fronts a little high, but you don't have this potential problem with the rear tires, so it's safe to lower them to the minimum. I use 2/3 of the weight of the tractor plus the weight of the heaviest implement, in my case, the 2,000 pound backhoe.

MarkC

 

[glennmac]

Mark, I'm sorry to hear that you have no opinions on this subject. /w3tcompact/icons/wink.gif In any event, I knew there was a basis for your statements, and what you say makes eminent good sense.

I guess what we--and apparently the farming community--do not know is what the tire manufacturers' recommendations are for given loads on the tires on our tractors. No information is disseminated on that issue other than what is in the owners' manuals. For example, my 2910 owners manual has a recommended pressure for fronts and rears, but it is not scaled for different weight loadings on the tractor. There is a boldface caution not to exceed these pressures. This causes me to wonder what load Kubota is assuming is on the back of the tractor--nothing, a backhoe, what. For that matter, we dont know what they assume is on the front of the tractor--for a loader would reduce the load on the rear tires. Indeed, we dont even know what tire brand the owner's manual assumes, since I have seen Firestones, Goodyears and Titans on 2910's. Finally, if the pressures in the owners manual assume a naked tractor, it would seem that, contrary to the boldface warning, tire pressures should be increased with a loader and hoe on the tractor.

I suppose the only way be sure is to get the tire manufacturer's load/pressure specs for the particular tires we have.

 

[MChalkley]

Glenn - I guess it was a tad insincere of me to claim I have no opinion - what I should've said was that my opinion is that I should agree with the tire manufacturers... /w3tcompact/icons/smile.gif

You're exactly right - the only way to correctly inflate the tires is to figure it out using the manufacturer's data sheet for the tire - and you're not provided with that or even told it exists. I guess the CT and SCT manufacturers consider this to be a "tempest in a teapot" issue. Their view is obviously that you should "pump 'em up tight and go". (I know the rules of punctuation say the period should go inside the quotes, but I think it's stupid, and I refuse to do it. See, I do have an opinion on some things... /w3tcompact/icons/laugh.gif)

For those of us who want maximum performance, though, it's not a trivial issue (tire pressure, that is, not punctuation...). You get way less traction with an over-inflated tire, it's much harder on your back (and backside), etc.

For farmers, obviously, improper inflation steals bread from their table. Now that I'm doing more and more commercial work with my equipment in addition to the charity work I've been doing for the past 5 years or so, I'm firmly in the "stealing bread from my table" camp.

Still, tire loading can be a complicated issue, and it should be addressed more thoroughly by the tractor manufacturers. At the very least, they should provide the data sheets for the tires they sell you with the tractor. I admit that my tires are an extreme case (most everything is, with me), but a guy I know who has a huge Cat TLB, 4-wheel steering, extend-a-hoe, 4-in-1 bucket, you name it. We were working on the same job not long after I got the Michelins and he was laughing at the size of the tires (making comments like "What are you trying to do, make sure it'll still get traction if you roll it over?") One of the things, he said was "Next thing I know you'll have tires the same size as mine on that thing." I looked over at the lettering on his and said "They already are, next time they'll be bigger." As you might expect, he jumps down, saying "No way!", but it was true. Not only that, but mine were radials, whereas his were bias ply and mine have heavier duty ratings. So I got the data sheet for his Firestones and the next day we figured that he needs to have his inflated almost to the maximum allowed pressure. Mine, of course, need to be at the minimum. (Now the front tires are a totally different story - his are much heavier duty than mine.) The point is, it needs to be adjusted, at the very least, for the equipment it's installed on, if not also the circumstances it's being used under.

MarkC

 

[gordon]

Yes tire pressure is the key to alot of traction problems that are blamed to the tire itself. If the tire can't work properly then your losing traction and when you loose traction you loose production. Loose production and your losing money---cha-ching cha-ching. I often wonder why that subject hasn't come up more here. It is the least expensive way to gain preformance. Makes ya think no doubt.

All of the major players in the tire game have the sheets on pressure versus weight. Alot of the information is on the web. The Goodyear ag book is downloadable in pdf form lots of great information on tires for tractors. http://www.goodyear.com/us/tires/farm/handbook.html

Oops this is a thread on trans choices, glad I never go off topic. Ok back on track. At work we have a large John Deere and a large New Holland. The New Holland has all the bells. Four wheel drive or power assist-it kicks in with 15-20 percent wheel slippage. Diff locks on both front and back axles. Auto shift trans within the range-three ranges six gears in each range. They get used for cutting grass and pushing snow in the winter. That New Holland will push some snow, has a dregleman blade on the front and a rear blade as well. Offset the rearblade and you can cut a real wide pass.

Now to my question, how does the tractor know to kick in the power assist when the proper amount of wheel slippage is reached? Has to have some sort of wheel sensors, right? But like Bird said earlier the more stuff on the tractor the more possibilities of a breakdown.

Gordon

 

[Rowski]

I'll try a stab at it.

Viscous (sp?) clutch, clutch packs (like limited slip differential), or senors and computers.

Nice link. I'll have to look up my Firestones. Does air pressure play more of a role in radial or bais. I know it makes a difference in both. Radials give better traction, but... Just wondering. Like you said it the most cheapest/easiest thing to do to gain traction.

Derek

 

[TWINKLE_TOES]

MarkC,

Good post Mark, deserves a thread all it's own. If you watch the deformation of the rear tires on the tractors in the tractor pulls you figure out real quick they don't have those suckers at manufactuers max pressure. A big ole roll will form in front of the tire when they are working real hard.

Al