Tire size

Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
My l3001DT came with 12.4-26 tires on the rear and 8-16 on the front. I have swapped the rears to a 13.6-26. Is that a big enough change to hurt my 4x4 system?
 

Flintknapper

Well-known member

Equipment
L2350DT
May 3, 2022
1,050
1,290
113
Deep East Texas
My l3001DT came with 12.4-26 tires on the rear and 8-16 on the front. I have swapped the rears to a 13.6-26. Is that a big enough change to hurt my 4x4 system?
Depending on manufacturer.....you are probably looking at 1.5"-2.0" larger tire (diameter) over the stock tire.

So the tendency would be for the rear tires to push the fronts (when in 4wd). Whether or not that presents a problem steering or with binding of the gears....I can not say.
 

Mountainhill

Member

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l2501 (l3800 2013/22), Box Blade, post hole digger, Leon's rear blade
Apr 3, 2017
68
55
18
Nova Scotia, Canada
My l3001DT came with 12.4-26 tires on the rear and 8-16 on the front. I have swapped the rears to a 13.6-26. Is that a big enough change to hurt my 4x4 system?
Replacement tire is wider, not a smaller or larger dimension that would impact the ‘ratio’, so I’d say you have no issue.
 

Flintknapper

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L2350DT
May 3, 2022
1,050
1,290
113
Deep East Texas
Replacement tire is wider, not a smaller or larger dimension that would impact the ‘ratio’, so I’d say you have no issue.
13.6 tire is also taller (larger diameter by about 1.5"-2.0"), not just wider. That will change the ratio between the front and rear tires. Can't say if that will cause problems when in 4wd or not, but its a significant increase.
 

Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
13.6 tire is also taller (larger diameter by about 1.5"-2.0"), not just wider. That will change the ratio between the front and rear tires. Can't say if that will cause problems when in 4wd or not, but its a significant increase.
I do appreciate the feedback, I usually don’t use 4x4 much. But I won’t use it till I get new front tires for sure. I had chatted with another group member about it and he said to go to 9-16 I think.
 

woodman55

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L6060HSTC, RTV 1100
May 15, 2022
470
257
63
canada
I would try it on a firm dry surface and see how hard it is to get it into and out of 4x4. That will tell you how bad/good the tires match up. You can also lower the air pressure in your rear tires, this will help bring the ratio back to where it was with the smaller tires.

On a bit of a side note. My 6060 came with the rears inflated to 12psi, I lower them to 5 psi to get a better ride, and the 4x4 engages and disengages better now than it did with the rears at 12psi. Plus even with a load on the 3pt, the rears only have a very slight bulge.
 
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Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
I would try it on a firm dry surface and see how hard it is to get it into and out of 4x4. That will tell you how bad/good the tires match up. You can also lower the air pressure in your rear tires, this will help bring the ratio back to where it was with the smaller tires.

On a bit of a side note. My 6060 came with the rears inflated to 12psi, I lower them to 5 psi to get a better ride, and the 4x4 engages and disengages better now than it did with the rears at 12psi. Plus even with a load on the 3pt, the rears only have a very slight bulge.
Didn’t think about the air pressure, I’ll give that a try and when it dries up I’ll put it on the pavement to test it out. Thank you for the help
 
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The Evil Twin

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L2501, LA526, LP Box Blade, EA dual lid grapple
Jul 19, 2022
1,006
841
113
Virginia
Well I'll be darned. They are different. More interestingly is that some 28's aren't.
 

Flintknapper

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Equipment
L2350DT
May 3, 2022
1,050
1,290
113
Deep East Texas
Didn’t think about the air pressure, I’ll give that a try and when it dries up I’ll put it on the pavement to test it out. Thank you for the help
I don't think lowering the air pressure will relieve you of the ratio disparity. It would change the diameter of the tire (overall height) but the circumference of the tire remains the same. The distance traveled for one revolution of the axle should remain the same.....regardless the profile of the tire.

That is not to say that other dynamics (more or less resistance/torque realized at the axle) wouldn't affect the slippage on soft surfaces...but it won't have the effect of changing the final drive ratio. This will be most evident on hard surfaces where the gear binding will be felt.

Also, if the rear tires (now being taller) have changed the final drive ratio such that they overdrive the fronts (pushing them) you 'might' find it more difficult to steer the tractor in 4wd (it wants to keep going straight). But gear binding would be my greater concern. Using 4wd on soft surfaces will allow the tires on either axle/differential to slip....so no problem. Can't say the same for hard surfaces with good traction.

Changing the front tires to match (or nearly match) the final drive ratio of the rears would be the best solution.
 

GeoHorn

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May 18, 2018
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113
Texas
I would try it on a firm dry surface and see how hard it is to get it into and out of 4x4. That will tell you how bad/good the tires match up. You can also lower the air pressure in your rear tires, this will help bring the ratio back to where it was with the smaller tires.

On a bit of a side note. My 6060 came with the rears inflated to 12psi, I lower them to 5 psi to get a better ride, and the 4x4 engages and disengages better now than it did with the rears at 12psi. Plus even with a load on the 3pt, the rears only have a very slight bulge.
I think I’d FIRST try it on a dirt or loose surface to see if the tires are compatible….before stressing the gearboxes on a firm/dry surface. ;)
 
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Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
I don't think lowering the air pressure will relieve you of the ratio disparity. It would change the diameter of the tire (overall height) but the circumference of the tire remains the same. The distance traveled for one revolution of the axle should remain the same.....regardless the profile of the tire.

That is not to say that other dynamics (more or less resistance/torque realized at the axle) wouldn't affect the slippage on soft surfaces...but it won't have the effect of changing the final drive ratio. This will be most evident on hard surfaces where the gear binding will be felt.

Also, if the rear tires (now being taller) have changed the final drive ratio such that they overdrive the fronts (pushing them) you 'might' find it more difficult to steer the tractor in 4wd (it wants to keep going straight). But gear binding would be my greater concern. Using 4wd on soft surfaces will allow the tires on either axle/differential to slip....so no problem. Can't say the same for hard surfaces with good traction.

Changing the front tires to match (or nearly match) the final drive ratio of the rears would be the best solution.
I plan to change the front tires. My only deal is that I don’t break something. I know in 2wd I have no issues, I don’t use 4x4 very much even in my own trucks. Last time I ever used 4x4 was to rotate the diff a few times to slosh oil around after I rebuilt the portal/final drive up front. I’m going up to a 9-16 to make sure it’s perfect. I’m slowly rebuilding this tractor from the ground up.
 
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Mountainhill

Member

Equipment
l2501 (l3800 2013/22), Box Blade, post hole digger, Leon's rear blade
Apr 3, 2017
68
55
18
Nova Scotia, Canada
13.6 tire is also taller (larger diameter by about 1.5"-2.0"), not just wider. That will change the ratio between the front and rear tires. Can't say if that will cause problems when in 4wd or not, but its a significant increase.
My mistake, glad to be corrected 🤔
 

Flintknapper

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Equipment
L2350DT
May 3, 2022
1,050
1,290
113
Deep East Texas
I plan to change the front tires. My only deal is that I don’t break something. I know in 2wd I have no issues, I don’t use 4x4 very much even in my own trucks. Last time I ever used 4x4 was to rotate the diff a few times to slosh oil around after I rebuilt the portal/final drive up front. I’m going up to a 9-16 to make sure it’s perfect. I’m slowly rebuilding this tractor from the ground up.
Good plan and as long as you don't engage 4wd on a hard surface with good traction, you'd likely be OK until you can change out the fronts. As long as the fronts can slip.
 

Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
Good plan and as long as you don't engage 4wd on a hard surface with good traction, you'd likely be OK until you can change out the fronts. As long as the fronts can slip.
So I talked to my kubota dealer and he said the L345DT, which is the American version of my tractor to the T, came with 2 rear wheel options. 12.4-28 and 13.6-28. The front wheel was a 8-18. So I think I’ll be ok with what I have. I know the tire size pretty much stays the same even though I have 8-16 instead of 8-18 up front and a 26 inch rim in the rear instead of a 28, I believe but any advice I get I’ll be glad to take in the knowledge and use it.
 

North Idaho Wolfman

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L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
24,805
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113
Sandpoint, ID
I'll bet your front tires are pretty worn down, which drops the ratio even more.
You would be safer to run a 9-16 with that new rear tire.
A lot of people have never seen the inside of the front gear case, well lets just say very small is a good description of the gears in there, and takes little force to snap them.
Also not OLD (original) 13.6 -28 were smaller diameter than the new 13.6 -28's
 

Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
I'll bet your front tires are pretty worn down, which drops the ratio even more.
You would be safer to run a 9-16 with that new rear tire.
A lot of people have never seen the inside of the front gear case, well lets just say very small is a good description of the gears in there, and takes little force to snap them.
Also not OLD (original) 13.6 -28 were smaller diameter than the new 13.6 -28's
I don’t know why I said new lol, these tires are new for the tractor. There off of a 80’s model yanmar. Sorry I didn’t say something earlier, I’m with you on the new front tires for sure. The ones on it have 90% tread left cause the tractor only has a little over 800 hours. She’s still not broke in yet. I been looking for some 9-16 but they don’t really make that tire anymore from what I can see. All I’ve found is 9-16.5, I can get the 9-16’s no problem from bkt but they want 400$ a piece for them.
 

North Idaho Wolfman

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Jun 9, 2013
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Sandpoint, ID
There off of a 80’s model yanmar.
Now that changes this a bit.
Might be old profile tires so, Flat hard surface, put the tractor in neutral, 4wd engaged, manually push the tractor, if it rolls several feet before binding, then your good to go.
P.S. Take it back out of 4wd after the test, and don't run it in 4wd on hard surfaces! ;)
 
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Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
I'll bet your front tires are pretty worn down, which drops the ratio even more.
You would be safer to run a 9-16 with that new rear tire.
A lot of people have never seen the inside of the front gear case, well lets just say very small is a good description of the gears in there, and takes little force to snap them.
Also not OLD (original) 13.6 -28 were smaller diameter than the new 13.6 -28's
Now that changes this a bit.
Might be old profile tires so, Flat hard surface, put the tractor in neutral, 4wd engaged, manually push the tractor, if it rolls several feet before binding, then your good to go.
P.S. Take it back out of 4wd after the test, and don't run it in 4wd on hard surfaces! ;)
I took it for a test run when I got home and when I put it on the pavement I killed the engine while it was in a bind and I could engage and disengage 4x4 with no problem and as far as I could tell there was no scuffing unless I turned really hard, which I know is normal for any 4x4 vehicle. I didn’t try what you said but I’ll try that when I get home tomorrow. All of this was done on pavement. Again I’m sorry for not mentioning the tires were used lol.
 
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GeoHorn

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May 18, 2018
4,463
2,084
113
Texas
Now that changes this a bit.
Might be old profile tires so, Flat hard surface, put the tractor in neutral, 4wd engaged, manually push the tractor, if it rolls several feet before binding, then your good to go.
P.S. Take it back out of 4wd after the test, and don't run it in 4wd on hard surfaces! ;)
THAT is an EXCELLENT test for sure!

I once had a Jeep Cherokee that I discovered by accident would not “coast” in 4WD. By that, I mean that while in neutral the car would not roll smoothly….but acted as if the emerg. brake was applied.

I took it in to the tire store that had just sold me new tires and they were as shocked as I to discover the exact SAME size/brand of tire on all four wheels….. the rear tires had over one-inch greater circumference than the fronts. (Their mfr’r dates were also about 6-months apart.)
Changing all 4 tires again to the same mfr’g date resolved the problem. (Cooper tires)

Anyway… a good tire-match should roll very easily in 4WD with the tranny in nuetral. Thanks Wolfman for the reminder.
 

Dynexmidnight

New member

Equipment
L345DT
Aug 17, 2022
23
4
3
Mississippi
Now that changes this a bit.
Might be old profile tires so, Flat hard surface, put the tractor in neutral, 4wd engaged, manually push the tractor, if it rolls several feet before binding, then your good to go.
P.S. Take it back out of 4wd after the test, and don't run it in 4wd on hard surfaces! ;)
Alright I tested it the way you said to and it passed. I also tried putting it in and out of 4x4 on the pavement again and it worked perfect.
 
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