Tire Selection, L2500DT

[pigdoc]

Looking for the wisdom of others who have encountered this dilemma.

This is the tractor that I recently bought and that I'm working to repair the front wheel drive on.
Front propeller shaft coupler was totally stripped out, and it tore up the front drive pinion splines pretty good.

I bought this tractor with a known non-functional front wheel drive, so I got it cheap.
It had tires on it that were not the stock sizes, including a pair of new lug tires on the front on Kubota rims (still with stickers!), much larger than the factory size.
Here's a pic:

I've spent some time surfing old posts here, to understand the issue of tire size and how it threatens the front drive mechanism if it's not 'correct'. I understand the "lead/lag" issue.

I looked up Rolling Circumference (RC) for the tires online and from those, calculated the front/rear ratios.

Factory tire sizes on the L2500 (from Specifications published by Kubota):
Rear: 9.5x24 RC 123 to RC 125 (depending on brand)
Front: 6.00x14 RC 77
Ratio: 0.621 to 0.626

Installed tire sizes:
Rear: 11.2x24 (Firestone Field & Road) RC 129 [they are a bit worn, with a diminished RC, which would increase the ratio.]
Front: 7.00x16 (Galaxy Agritrac II) RC 90.2
Ratio: 0.70

When I bought this tractor, it was surprising to me that it had virtually brand new Kubota wheels and tires on the front. Now, I'm thinking that the PO had put new tires/wheels on the front, and that is what wrecked the prop shaft coupler. The increase in tire size and consequent change in ratio would have greatly increased the "lead" on the front tires. Probably didn't take long for the coupler to give up.

So, my target is to get the Ratio as close as I can to 0.62 or 0.625, as I see it. BEFORE I throw a bunch of new (expensive) parts at the problem.

The rear tires still have about 1/2 of their tread left, but they are starting to dry rot. AND, I really do need fluid in them. So, I'm thinking that I might just upsize the rear tires rather than downsize the front tires. But, either or both are possible solutions.

I have done some online research on current R1 tire availability.
I have three several possibilities for a 13.6x24 rear tire:
- Firestone Super All-Traction II, RC 140 [Changes ratio to 0.644, using the 7.00x16 front tires.]
- Carlisle CSL24, RC 142 [Changes ratio to 0.635]
- Titan Hi-Traction, RC143 [Changes ratio to 0.631]
- Galaxy EarthPRO 45, RC143

If I add a tolerance of 2% to the factory ratio, I get 0.628 to 0.639.

Or, just should I replace all 4 tires, and put it back to factory?
I will probably never be driving this tractor on pavement.

I'm not averse to spending money on new rear tires, as I definitely need fluid in the rears anyway, and I AM averse to spending the money for fluid into old tires and innertubes, because of the increased stress on them that will be caused by the fluid.

I need to go back to MGD this week. On their junk tire pile, they had a couple of very good front lug tires on Kubota orange 6-lug rims, smaller than the ones on my tractor. Don't remember the size...I think I'll run over their today. If they'll sell me that set for a reasonable price, I'm coming home with them. Somebody will need them!

Looking forward to your feedback!
-Paul

 

[pigdoc]

<sigh>
Kubota published specs for front tires for this tractor in two places in the Operator's Manual.
In one place (page 10), it's "6.00-14" (for the DT), in the other (page 37), its "7.00-16".

Reading 'between the lines' the Manual seems to suggest that the 6.00-14 goes with the 9.5-24 rear tire.
And, they do provide recommended tire pressures and track adjustment diagrams in this Manual for 9.5, 11.2, and 13.6-24 rear tires (Operations section).

7.00-16s are currently on the front of my tractor.
So, maybe those are the front tires that are to go with 13.6 rears?
It's just not discussed in the Operator's Manual!
[I have a WSM on its way to me.]

I also spent some more time with the Parts Diagrams at Messicks, and I discovered that, for the ring gear/drive pinion combos (for any tractor), in the Notes section, it gives the tooth counts for most gears. Rear diff is "8-39T" for a ratio of 4.875:1.

But, staring at the exploded Parts Diagrams to determine drive ratios is not very helpful for figuring out final drive ratios. Torque for the front axle comes from the countershaft and is transferred to the PTO shaft. There are at least 2 gear reductions and a step up in the transmission, and then three more reductions in the front axle (diff and two bevel gear sets in the axle drops).

I must do the Rolling Circumference test (with 4WD engaged) to be sure of the final front-rear drive ratio, rather than rely on book values for tire RCs in the Kubota-specified sizes. Then, I can accurately match tire RC specs to the tractor's gearing (plus ~2% lead for the front). The test will also give me a true reading on the (worn) rear tires' actual RC (by measuring how far the tractor moves for each rotation of the tire), rather than having to rely on book values for new tires.

I suppose that, if you had different tire wear (front vs rear), the deviation from your specified "lead/lag"
could change enough to stress the front drive components on hard surfaces...

It's probably a good recommendation to change all 4 tires when they get worn, rather than just the fronts or just the rears. Something my PO did not do.

Stay Tuned.
-Paul

 

[PoTreeBoy]

Looking for the wisdom of others who have encountered this dilemma.

This is the tractor that I recently bought and that I'm working to repair the front wheel drive on.
Front propeller shaft coupler was totally stripped out, and it tore up the front drive pinion splines pretty good.

I bought this tractor with a known non-functional front wheel drive, so I got it cheap.
It had tires on it that were not the stock sizes, including a pair of new lug tires on the front on Kubota rims (still with stickers!), much larger than the factory size.
Here's a pic:
View attachment 116569

I've spent some time surfing old posts here, to understand the issue of tire size and how it threatens the front drive mechanism if it's not 'correct'. I understand the "lead/lag" issue.

I looked up Rolling Circumference (RC) for the tires online and from those, calculated the front/rear ratios.

Factory tire sizes on the L2500 (from Specifications published by Kubota):
Rear: 9.5x24 RC 123 to RC 125 (depending on brand)
Front: 6.00x14 RC 77
Ratio: 0.621 to 0.626

Installed tire sizes:
Rear: 11.2x24 (Firestone Field & Road) RC 129 [they are a bit worn, with a diminished RC, which would increase the ratio.]
Front: 7.00x16 (Galaxy Agritrac II) RC 90.2
Ratio: 0.70

When I bought this tractor, it was surprising to me that it had virtually brand new Kubota wheels and tires on the front. Now, I'm thinking that the PO had put new tires/wheels on the front, and that is what wrecked the prop shaft coupler. The increase in tire size and consequent change in ratio would have greatly increased the "lead" on the front tires. Probably didn't take long for the coupler to give up.

So, my target is to get the Ratio as close as I can to 0.62 or 0.625, as I see it. BEFORE I throw a bunch of new (expensive) parts at the problem.

The rear tires still have about 1/2 of their tread left, but they are starting to dry rot. AND, I really do need fluid in them. So, I'm thinking that I might just upsize the rear tires rather than downsize the front tires. But, either or both are possible solutions.

I have done some online research on current R1 tire availability.
I have three several possibilities for a 13.6x24 rear tire:
- Firestone Super All-Traction II, RC 140 [Changes ratio to 0.644, using the 7.00x16 front tires.]
- Carlisle CSL24, RC 142 [Changes ratio to 0.635]
- Titan Hi-Traction, RC143 [Changes ratio to 0.631]
- Galaxy EarthPRO 45, RC143

If I add a tolerance of 2% to the factory ratio, I get 0.628 to 0.639.

Or, just should I replace all 4 tires, and put it back to factory?
I will probably never be driving this tractor on pavement.

I'm not averse to spending money on new rear tires, as I definitely need fluid in the rears anyway, and I AM averse to spending the money for fluid into old tires and innertubes, because of the increased stress on them that will be caused by the fluid.

I need to go back to MGD this week. On their junk tire pile, they had a couple of very good front lug tires on Kubota orange 6-lug rims, smaller than the ones on my tractor. Don't remember the size...I think I'll run over their today. If they'll sell me that set for a reasonable price, I'm coming home with them. Somebody will need them!

Looking forward to your feedback!
-Paul

@eserv published tables some time ago. According to the L table, the L2500DT gear ratio is 1.6363, or 0.611 inverted.

 

[pigdoc]

@eserv published tables some time ago. According to the L table, the L2500DT gear ratio is 1.6363, or 0.611 inverted.

Ohhh, THANKS for that hot tip!
Here it is:
Tractor Wheel Database Somewhere? | OrangeTractorTalks - Everything Kubota

GOLD!
Deserves a re-up!

I will be carrying this list when I'm at sales, simply to judge used tractors on how well the tire ratios (Rolling Circumference or Diameter) match up with the tractor gearing.

-Paul

 

[pigdoc]

@eserv published tables some time ago. According to the L table, the L2500DT gear ratio is 1.6363, or 0.611 inverted.

Got out and did the Rolling Circumference test today.

First, I marked a rear tire and a front tire at the same place (top lug, so I could lean over a fender and see the mark from the driver's seat).
Then, I drove a marker stake directly below the rear axle CL.
With the 4WD off, I drove forward 10 rear tire revolutions, while counting the front tire revolutions.
For this test, the tractor rolled forward 106 feet, 4 inches. And, the front tire went around exactly 15 revolutions.

That established the rolling circumference of the two tires:
Rear: 127.6 inches (measured, versus the book value for new tires of the same brand, 129 inches)
Front: 85.1 inches (calculated, from the 1.5 ratio observed).
Ratio: 1.5

To measure the gearing of the tractor, I put the tractor in 4WD and repeated the test.
This time, the front tires went around 16.25 revolutions for 10 revolutions of the rear tires.
From that, the gear ratio is estimated to be 1.625 (Front vs Rear), very close to the 'book' value of 1.6363.

Note, I did these tests on loose gravel, so there is a bit of error in measuring rear tire RC, due to slippage.
I took a look at that, too.

I simply backed up to the starting point, and noted that I went one foot farther for the same number of rear tire revolutions when I backed up. So, a bit less than 1% error in my measurements, due to tire slippage.

Now, I have everything I need to confidently order new rear tires that will be the correct circumference to match the front tires and for the gearing of the tractor!

See my other thread for an update on the front wheel drive repair...

-Paul

 

[fried1765]

Got out and did the Rolling Circumference test today.

First, I marked a rear tire and a front tire at the same place (top lug, so I could lean over a fender and see the mark from the driver's seat).
Then, I drove a marker stake directly below the rear axle CL.
With the 4WD off, I drove forward 10 rear tire revolutions, while counting the front tire revolutions.
For this test, the tractor rolled forward 106 feet, 4 inches. And, the front tire went around exactly 15 revolutions.

That established the rolling circumference of the two tires:
Rear: 127.6 inches (measured, versus the book value for new tires of the same brand, 129 inches)
Front: 85.1 inches (calculated, from the 1.5 ratio observed).
Ratio: 1.5

To measure the gearing of the tractor, I put the tractor in 4WD and repeated the test.
This time, the front tires went around 16.25 revolutions for 10 revolutions of the rear tires.
From that, the gear ratio is estimated to be 1.625 (Front vs Rear), very close to the 'book' value of 1.6363.

Note, I did these tests on loose gravel, so there is a bit of error in measuring rear tire RC, due to slippage.
I took a look at that, too.

I simply backed up to the starting point, and noted that I went one foot farther for the same number of rear tire revolutions when I backed up. So, a bit less than 1% error in my measurements, due to tire slippage.

Now, I have everything I need to confidently order new rear tires that will be the correct circumference to match the front tires and for the gearing of the tractor!

See my other thread for an update on the front wheel drive repair...

-Paul

Thank you for sharing this information!

 

[pigdoc]

The saga continues...

I had two choices to make Rolling Circumference correct for the tractor:
- replace front wheels/tires with smaller ones
- replace rear wheels/tires with larger ones

The fronts had recently been replaced, and the rears are half-worn and badly weather-checked.
So, setting aside the relative costs of my two choices, it makes more sense to replace the rears.
[I only want to do this ONCE.] Original rear rims are 10-24s.

I started by taking my MEASURED RC of the front tires and multiplying that by 1.02X the gear ratio of the tractor to put 2% lead into the fronts. Thus, for the L2500, I need the tire ratio to be 1.67 (1.6363*1.02), Based on the MEASURED RC of the front tires, the RC of the rear tires needs to be 142 inches.

Of course, I won't have the opportunity to actually measure the rear RC until the wheels and tires are installed on the tractor. I have discovered that tire manufacturers not always precise about what the actual Rolling Circumference of their tires is, as installed. The book value on the 7.00-16 front tires (Galaxy Agri-Trac II) is published at 90.2 inches. The actual measurement I got was 85.1 inches. That's a huge difference. So, I'm hedging that the actual RC of the Galaxy rear tires will be a bit less than the book value. So, in general, do NOT rely heavily on published RC values.

I had several rear tire brand choices, with book-value RCs (for 13.6-24) of around 142 to 143 inches.
Carlisle CSL24 - 142 inches
Titan Hi-Traction - 143 inches
Galaxy EarthPRO 45 - 142.9 inches
BKT TR-135 - 140 inches

Galaxy tires are manufactured by Yokohama. I like the idea of Japanese tires on a Japanese tractor. The BKTs are about $50 less. After carefully measuring the diameter of a brand-new unmounted BKT 13.6-24, I think their book-value RC is a bit low. If I was putting tires on a grey market tractor, I'd probably lean towards the BKTs (manufactured in India). So, I'm going with Galaxy rear tires.

Next, rims. For the L2500 I need 24-inch "4-loop" rims to work with the wheel centers. Books say they need to be 12 inches wide for 13.6-24 tires.

I live only about 30 miles from one of the biggest used tractor tire/rim yards in the region - Wenger Systems, in New Holland, PA. I spent a few hours wandering around that yard on Tuesday. LOTS of 6-loop wheels, zero 4-loop 12-24s. "We'll have to make those for you, $200 each." And "Oh, we can't get those Kubota brackets to weld onto the rims anymore, so you're getting the generic loop." Cuts your rear track options down from 8 to 4, but I'm setting my rear track as wide as I can get it, so that doesn't really matter to me. This ain't gonna be a row-crop tractor!

I sez, "OK, do it."

When my rims are welded up, I'll pick them up, and take them to the powder-coating place. I think, for a bit of bling, I'm going to have them powder-coated in that off-white (cream) color that Kubota used in the late 1980s. Black tire, cream rim, orange center. She'll be sharp-dressed, for sure!

A note on fender clearance. With the old rear tires (127.5 RC), I had about 3.5 inches of fender clearance. I think the new tires will clear the fenders with an inch to spare, but that's NOT enough room to run tire chains. I have hundreds of hours of seat-time on an International 460 Utility with FEL, and we ALWAYS ran rear tire chains on that tractor in the winter (in Iowa).

I took a look at the fender mounts on the L2500, and it's a simple matter to make spacers out of strap iron to raise them. We'll see...

If I had unlimited access to Kubota rear wheel centers, I'd try to get hold of a set of 24-inch for 6-loop wheels, because 6-loop wheels are much easier to find. Kubota put these 24-inch, 6-loop centers on the L3450, for one. But, many (most?) Kubota 6-loop centers are for 26-inch (and up) wheels. And then, for bigger tractors yet, the 6-loop centers mount with 8-lugs.

By the way, the center hub and bolt pattern seem to be the same for all 6-lug rear wheel centers: Hub hole diameter is 135mm, lug bolt diameter is 170mm.

Stay tuned!
-Paul

 

[PoTreeBoy]

The saga continues...

I had two choices to make Rolling Circumference correct for the tractor:
- replace front wheels/tires with smaller ones
- replace rear wheels/tires with larger ones

The fronts had recently been replaced, and the rears are half-worn and badly weather-checked.
So, setting aside the relative costs of my two choices, it makes more sense to replace the rears.
[I only want to do this ONCE.] Original rear rims are 10-24s.

I started by taking my MEASURED RC of the front tires and multiplying that by 1.02X the gear ratio of the tractor to put 2% lead into the fronts. Thus, for the L2500, I need the tire ratio to be 1.67 (1.6363*1.02), Based on the MEASURED RC of the front tires, the RC of the rear tires needs to be 142 inches.

Of course, I won't have the opportunity to actually measure the rear RC until the wheels and tires are installed on the tractor. I have discovered that tire manufacturers not always precise about what the actual Rolling Circumference of their tires is, as installed. The book value on the 7.00-16 front tires (Galaxy Agri-Trac II) is published at 90.2 inches. The actual measurement I got was 85.1 inches. That's a huge difference. So, I'm hedging that the actual RC of the Galaxy rear tires will be a bit less than the book value. So, in general, do NOT rely heavily on published RC values.

I had several rear tire brand choices, with book-value RCs (for 13.6-24) of around 142 to 143 inches.
Carlisle CSL24 - 142 inches
Titan Hi-Traction - 143 inches
Galaxy EarthPRO 45 - 142.9 inches
BKT TR-135 - 140 inches

Galaxy tires are manufactured by Yokohama. I like the idea of Japanese tires on a Japanese tractor. The BKTs are about $50 less. After carefully measuring the diameter of a brand-new unmounted BKT 13.6-24, I think their book-value RC is a bit low. If I was putting tires on a grey market tractor, I'd probably lean towards the BKTs (manufactured in India). So, I'm going with Galaxy rear tires.

Next, rims. For the L2500 I need 24-inch "4-loop" rims to work with the wheel centers. Books say they need to be 12 inches wide for 13.6-24 tires.

I live only about 30 miles from one of the biggest used tractor tire/rim yards in the region - Wenger Systems, in New Holland, PA. I spent a few hours wandering around that yard on Tuesday. LOTS of 6-loop wheels, zero 4-loop 12-24s. "We'll have to make those for you, $200 each." And "Oh, we can't get those Kubota brackets to weld onto the rims anymore, so you're getting the generic loop." Cuts your rear track options down from 8 to 4, but I'm setting my rear track as wide as I can get it, so that doesn't really matter to me. This ain't gonna be a row-crop tractor!

I sez, "OK, do it."

When my rims are welded up, I'll pick them up, and take them to the powder-coating place. I think, for a bit of bling, I'm going to have them powder-coated in that off-white (cream) color that Kubota used in the late 1980s. Black tire, cream rim, orange center. She'll be sharp-dressed, for sure!

A note on fender clearance. With the old rear tires (127.5 RC), I had about 3.5 inches of fender clearance. I think the new tires will clear the fenders with an inch to spare, but that's NOT enough room to run tire chains. I have hundreds of hours of seat-time on an International 460 Utility with FEL, and we ALWAYS ran rear tire chains on that tractor in the winter (in Iowa).

I took a look at the fender mounts on the L2500, and it's a simple matter to make spacers out of strap iron to raise them. We'll see...

If I had unlimited access to Kubota rear wheel centers, I'd try to get hold of a set of 24-inch for 6-loop wheels, because 6-loop wheels are much easier to find. Kubota put these 24-inch, 6-loop centers on the L3450, for one. But, many (most?) Kubota 6-loop centers are for 26-inch (and up) wheels. And then, for bigger tractors yet, the 6-loop centers mount with 8-lugs.

By the way, the center hub and bolt pattern seem to be the same for all 6-lug rear wheel centers: Hub hole diameter is 135mm, lug bolt diameter is 170mm.

Stay tuned!
-Paul

I may have slipped a digit, but if your front rolling circumference is 80.5", wouldn't your perfect rear be 80.5*1.636=139.2", and if you want front lead, rear would be 139.2/1.02=136.5"?

 

[pigdoc]

I may have slipped a digit, but if your front rolling circumference is 80.5", wouldn't your perfect rear be 80.5*1.636=139.2", and if you want front lead, rear would be 139.2/1.02=136.5"?

THANKS for your reply, PoTreeBoy!

Front RC is 85.1 inches, not 80.5 inches.
But, your calculation is right on.

85.1 * 1.6363 = 139.25" - rear tire RC that 'matches' front tire "measured RC".
139.25"/1.02 = 136.5" - my tractor's ideal "measured RC" for the rear tires, providing 2% front tire "lead".

In my search for the optimal rear tire, I've taken to measuring diameter across the plane of the tread, at its apex, just to check the RC book values against reality.

For my front tires (Galaxy Agri-Trac II), the book value RC is 90.2", but the actual measurement of the tire itself was 86.3 inches (from diameter, converted to circumference). And, the "measured RC" is 85.1". ["Measured RC" is the rolling test, described above.] Couple of important points in there:
- book value RC seems uh, 'inflated' (no pun intended)
- measured RC is about 1.4% smaller than the diameter measurement. I attribute the difference to the tread sinking into the ground surface. [So, "measured RC" is dependent upon tread depth and ground conditions, e.g., pavement vs mud, to pick a couple of extremes.] I measured the RC of the fronts on a relatively soft surface - loose gravel, with 4WD disengaged. That's going to be representative of the surface this tractor will be most used on. I don't ever expect to drive the tractor on pavement (in 4WD).

Anyway, back to the rear tires. Based on the limited dataset I have (so far), I'm working on a presumption that the measured RCs of Galaxy tires are going to be 'somewhat less' than the book values...and, what the measured diameter would indicate. And, 'somewhat greater' than the "measured RC", due to 'tread penetration' of the surface. I won't know for sure until I repeat the "measured RC" test with the new tires.

For the dimensions of the Galaxy EarthPRO 45, here's what I have:

Of course, a big unknown is how much the tire diameter is going to 'grow' when it is inflated. My projection: not much.

I had the opportunity to measure that Galaxy EarthPRO 45 12.4-24 tire but neglected to do so last week. I'll measure it tomorrow. I just think it's bound to be too small. But, we'll see!

I realize that, for the sake of front tire "lead", it's better to err on the side of rear tire being a bit smaller than the tractor's gear ratio calls for. [A too-big rear tire is going to result in front tire "lag".]

Bottom line is that, 'on-paper', the process of picking a rear tire size should be simple and straightforward. But, in practice, you've got all sorts of considerations:
- accuracy of book values
- inflation pressure (affects circumference? By how much?)
- ground conditions/tread depth (softer ground will yield smaller measured RCs)
- relative weighting, front to rear (more weight on rears relative to fronts, smaller rear measured RCs)
- wear (over time, rears will likely wear faster than fronts, if 4WD use is judicious)

Another unknown is how much 'hydroinflation' and/or rear wheel weights are going to change "measured RC" - ground penetration of the tread will increase as a result. And, I will do one (if not both) of those things.

All this creates anxiety over writing that big check.
And, I'm overthinking the choice. That's just me.

In the back of my mind is the realization that the repair I did on the front drive pinion is not as strong as original. The more front "lead" (or "lag") I have, the more stress on that repair. I think the 13.6-24s are going to put me pretty close to zero front lead.

-Paul