Mechanical Ratio

[Milo Holroyd]

Why is this info not available for Kubotas? I have asked two different dealers and both say Kubota does not supply that info. Am I missing something? Just trying to source different tires/rims for my L3130 HST. Has Industrial lugs on it now. Want to replace with Ag when the time comes. (soon). I have a pdf from firestone that describes the process of using three people and counting tire revolutions (engaged and disengaged) and the subsequent math to obtain the lead/lag. Is that the only / accurate method? Thanks for any help.

 

[skeets]

I think you mean the rolling ratio of the tires, there is a formula to figure it out, but I dont know it off the top pf my head. I bet the wolfman or one of the smart guys can fix you right up,, just hang loose it might take a day or so

 

[North Idaho Wolfman]

Fronts are 7.2-16 RC 89
Rears are 12.4-24 RC136

Your going to have an extremely difficult time varying from these sizes and still getting it to stay in ratio, as it is an odd tire size matchup.

 

[AllDodge]

I'm finding, a lot of gear ratios in the final out, but for tires sizes use this

Front old tires were 7.2-16 and new are 7-16
Rear 12.4-24

Front circumference = 87 inches
Rear circumference = 138.7 inches

Not the circumference of the tires. If you divide 138.7/87 = 1.59

So if you find other tires note the circumference and do the calculation. Keep it close if not exact this figure. This way there will be no undo stress on the drive line

 

[Milo Holroyd]

Thanks for the replies everyone. I'm still waiting for the ice to subside so I can run the rolling test to determine the lead / lag I have now with the R4 industrial lugs. I'm gonna attach the .pdf from firestone that I am using for this test.
(hopefully that's allowed)

 

[AllDodge]

Recommended tires

 

[georget]

Hi all..not trying to butt in on this thread.. I'm new to the forum..new to Kubotas.. So, what are you guys talking about..Mechanical ratio?..Lead/lag? And why does it make any difference? Seems to my dumb self that as long as the wheels go around and around and they fit in the wheel wells. you're good. Can one of you clue me in. I won't have to worry about it for awhile..new tires but eventually.

 

[D2Cat]

George, welcome to the forum. On two wheel drive tractors tire size doesn't make to much difference. However, on 4x4 tractors the circumference of the tires have to be within a range or mechanical binding occurs. That binding will eventually destroy drive parts.

 

[georget]

Thanks for that quick reply. Yeah, I'm trying to get my head around that. So, different drive ratios for the front and rear differentials..so in theory, I couldn't put the same size tire on the front and back..even if I could. So, is there only one ratio to meet regardless of tire size or will every manufacturer have there own requirements?
So I read that Firestone article..thanks Milo Holroyd.. interesting presentation so I guess no..what do you call it when you raise a jeep with huge tires? Oh well, thanks for the information and good night

 

[AllDodge]

Thanks for that quick reply. Yeah, I'm trying to get my head around that. So, different drive ratios for the front and rear differentials..so in theory, I couldn't put the same size tire on the front and back..even if I could. So, is there only one ratio to meet regardless of tire size or will every manufacturer have there own requirements?

It is calculated based on the gear ratio of front and rear. The front needs to have a faster ground speed the the rear. This is why the circumference of the tires play a large part in determining what tires can be used. Each manufacture can make the circumference different

 

[torch]

So, what are you guys talking about..Mechanical ratio?..Lead/lag? And why does it make any difference?

They are talking about the inter-axle ratio, or "Drive Train Ratio" as Kubota calls it. It is the ratio of the number of rotations of the front axle for each rotation of the rear axle. IE: a 1.475 ratio means the front axle rotates 1.475 times when the rear axle rotates once.

Unlike a 4wd car or truck, the front tires on most tractors are smaller diameter than the rears. The smaller circumference means that the front tires have to rotate more times to travel the same distance than the rear. So the manufacturer gears the front axle differently than the rear to compensate. "Lead" means that the front tires travel further than the rear, "Lag" means they travel less distance than the rear.

A bit of lead is good. Conventional wisdom says the fronts should about 2% lead, although apparently at least some Kubota models are designed to have between 3% and 7% lead. Lag is bad, putting additional strain on the system. At least when traveling forward.

To complicate matters further, you can't just measure the circumference of the tires. You have to do the calculations based on the "Rolling Circumference", which refers to the actual distance traveled per rotation by the tire when the tire is squished down by the weight of the loaded tractor. The rolling circumference can be estimated by the tire manufacturer, but varies by load, inflation pressure and tread wear.

As a new tractor owner with the OEM tires, the important thing for you to take away from this right now is to always use 2WD on hard surfaces. Otherwise the lead will be scuffing away your tread prematurely. 4WD is for loose or slippery surfaces only.

 

[GeoHorn]

They are talking about the inter-axle ratio, or "Drive Train Ratio" as Kubota calls it. It is the ratio of the number of rotations of the front axle for each rotation of the rear axle. IE: a 1.475 ratio means the front axle rotates 1.475 times when the rear axle rotates once.

Unlike a 4wd car or truck, the front tires on most tractors are smaller diameter than the rears. The smaller circumference means that the front tires have to rotate more times to travel the same distance than the rear. So the manufacturer gears the front axle differently than the rear to compensate. "Lead" means that the front tires travel further than the rear, "Lag" means they travel less distance than the rear.

A bit of lead is good. Conventional wisdom says the fronts should about 2% lead, although apparently at least some Kubota models are designed to have between 3% and 7% lead. Lag is bad, putting additional strain on the system. At least when traveling forward.

To complicate matters further, you can't just measure the circumference of the tires. You have to do the calculations based on the "Rolling Circumference", which refers to the actual distance traveled per rotation by the tire when the tire is squished down by the weight of the loaded tractor. The rolling circumference can be estimated by the tire manufacturer, but varies by load, inflation pressure and tread wear.

As a new tractor owner with the OEM tires, the important thing for you to take away from this right now is to always use 2WD on hard surfaces. Otherwise the lead will be scuffing away your tread prematurely. 4WD is for loose or slippery surfaces only.

AND.... don't forget that those specs are heavily dependent upon PROPER TIRE PRESSURES. Use the specified tire pressures or you defeat all that engineering you're paying for (OR you will pay for it later.)

 

[RCW]

They are talking about the inter-axle ratio, or "Drive Train Ratio" as Kubota calls it.

AND.... don't forget that those specs are heavily dependent upon PROPER TIRE PRESSURES. Use the specified tire pressures or you defeat all that engineering you're paying for (OR you will pay for it later.)

torch -

I want to thank you for that explanation! Greatly appreciated.

I'm no mathematical idiot, but this whole subject has baffled me. Your explanation makes more sense than any I've seen before.

GeoHorn -

Never thought of inflation being a factor, but that is logical, and apt to skew all the specs if not applied properly..

Thanks, guys.

 

[Milo Holroyd]

They are talking about the inter-axle ratio, or "Drive Train Ratio" as Kubota calls it. It is the ratio of the number of rotations of the front axle for each rotation of the rear axle. IE: a 1.475 ratio means the front axle rotates 1.475 times when the rear axle rotates once.

Unlike a 4wd car or truck, the front tires on most tractors are smaller diameter than the rears. The smaller circumference means that the front tires have to rotate more times to travel the same distance than the rear. So the manufacturer gears the front axle differently than the rear to compensate. "Lead" means that the front tires travel further than the rear, "Lag" means they travel less distance than the rear.

A bit of lead is good. Conventional wisdom says the fronts should about 2% lead, although apparently at least some Kubota models are designed to have between 3% and 7% lead. Lag is bad, putting additional strain on the system. At least when traveling forward.

To complicate matters further, you can't just measure the circumference of the tires. You have to do the calculations based on the "Rolling Circumference", which refers to the actual distance traveled per rotation by the tire when the tire is squished down by the weight of the loaded tractor. The rolling circumference can be estimated by the tire manufacturer, but varies by load, inflation pressure and tread wear.

As a new tractor owner with the OEM tires, the important thing for you to take away from this right now is to always use 2WD on hard surfaces. Otherwise the lead will be scuffing away your tread prematurely. 4WD is for loose or slippery surfaces only.

BINGO! and that is why I was asking for the mechanical ratio. There are several online calculators that allow for "plugging in" your ratio, and then front/ rear tire combos, with the result being your lead/lag. (but, you have to supply the loaded RC for any specific tire) I'm still waiting to run the test from the PDF I posted earlier. I will post the results here. Thanks for the help.

 

[North Idaho Wolfman]

BINGO! and that is why I was asking for the mechanical ratio. There are several online calculators that allow for "plugging in" your ratio, and then front/ rear tire combos, with the result being your lead/lag. (but, you have to supply the loaded RC for any specific tire) I'm still waiting to run the test from the PDF I posted earlier. I will post the results here. Thanks for the help.

I guess i'm not understanding why you don't get the right size tires and be done with it?

 

[torch]

BINGO! and that is why I was asking for the mechanical ratio. There are several online calculators that allow for "plugging in" your ratio, and then front/ rear tire combos, with the result being your lead/lag. (but, you have to supply the loaded RC for any specific tire) I'm still waiting to run the test from the PDF I posted earlier. I will post the results here. Thanks for the help.

Just to be clear: I am NOT saying your tractor's inter-axle ratio is 1.475. That number came to mind because it was just in another thread (referencing the B7300), but I don't know what it is for the L3130.

 

[Milo Holroyd]

I guess i'm not understanding why you don't get the right size tires and be done with it?

Because I'm not sure the tires on my tractor are correct. (420/70-24 rear and 10-16.5 front) Handles like a pig on ice in snow! So, I'm gonna run the test and establish my baseline.

 

[Milo Holroyd]

Just to be clear: I am NOT saying your tractor's inter-axle ratio is 1.475. That number came to mind because it was just in another thread (referencing the B7300), but I don't know what it is for the L3130.

Understood, and that is why I'm gonna do the test (weather permitting)

 

[North Idaho Wolfman]

Milo,
I can tell you those are the right size and ratio tires for the l3130.
The tire sizes are published for that model.

R4's do not handle snow worth a hoot, you would be much better off with chains or R3's.

 

[RCW]

R4's do not handle snow worth a hoot, you would be much better off with chains or R3's.

Milo - what Wolfman said....I'd never try a winter without chains, regardless what type of tire I have....