What will happen if I put these tire sizes on my B8200?

MAArcher

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Kubota B8200
Oct 6, 2022
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I can get a deal on turf tires on rims. The sizes are:
Fronts 20.5x8-10
Rears 31x13.5-15
And they reportedly came of a B7200.

But tractor data says I need:
Lawn/turf front: 24x8.5-12
Lawn/turf rear: 13.6-16

Can I still use these tires?

Thanks!
 
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North Idaho Wolfman

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Is it a 4wd?
If it is you might run a very high risk of breaking parts.
You would have to get the "RC" ( rolling circumferences ) of each tire to compare.
 

MAArcher

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Is it a 4wd?
If it is you might run a very high risk of breaking parts.
You would have to get the "RC" ( rolling circumferences ) of each tire to compare.
It is 4wd. what do I do with the RC?

Can I figure it out with this info:
No code has to be inserted here.

Does it make a difference if I will mostly be using 2wd and driving on lawn, not pavement?
Thanks
 

Flintknapper

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You need to know the rolling circumference of both the front and rear tires because your tractor is 4wd.

The front tires obviously are smaller (in diameter) than the rears. So the gear set in the front diff must closely match the final drive 'ratio' of the rear (when in 4wd) or you will experience drive-line binding and possibly break/damage something.

Most tire manufacturers will list the inflated/mounted diameter of the tire (which can vary a bit one manufacturer to the next), but you can multiply the tire diameter by Pi (3.14) to get an approximate rolling circumference.

Then compare the ratio of the front and rear tires to see if the 'new' tires compare favorably.

You understand the tires you cited are MUCH shorter in diameter than the ones recommended?

No matter how good a 'deal' they might be....I can't imagine why you'd want to go that route?
 

MAArcher

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You understand the tires you cited are MUCH shorter in diameter than the ones recommended?

No matter how good a 'deal' they might be....I can't imagine why you'd want to go that route?
thank you for the info! I did t think an inch or two smaller would make much difference? All I’m doing with the tractor is mowing a couple acres. Money’s tight and the used tires and rims in good condition are $350 compared to new ones that would cost $3,000. I‘ve been looking for months and this is the first set of 6 lug wheels with turf tires that I’ve seen.
 

MAArcher

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I didn't catch that the tire specs compared to the ones I want to by didn't post. Here they are again:
Tractor data Spec Diameter
front 24X8.50-12 23.6
Rear 13.6-16 38.4

Used tires Diameter
20.5x8-10 20.5
31x13.5-15 31.5

How much of a ratio variance is acceptable? if I did it right the correct ratio is 1.6 while the used tires have a ratio of 1.5

Also, to be clear on what I'm trying to do, I have AG tires on there now, so if I have any projects that require traction I can swap and use those tires. But for routine weekly mowing I'd be using these turf tires so I don't tear the yard up.
 

Flintknapper

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thank you for the info! I did t think an inch or two smaller would make much difference?
It may not. The difference in diameter for the fronts is about 3" shorter and 7" shorter in the rear....which would lower the tractor about 1.5" in the front and 3.5" in the rear. If this would cause no issues for you then from that standpoint you'd be OK.

The ratio difference (front to rear) for both sets are roughly 1.63 for the spec tires and 1.54 for the used ones. In 4wd (on loose surfaces) I wouldn't think that would be troublesome. You might contact your dealership and ask their opinion.
 
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Henro

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It may not. The difference in diameter for the fronts is about 3" shorter and 7" shorter in the rear....which would lower the tractor about 1.5" in the front and 3.5" in the rear. If this would cause no issues for you then from that standpoint you'd be OK.

The ratio difference (front to rear) for both sets are roughly 1.63 for the spec tires and 1.54 for the used ones. In 4wd (on loose surfaces) I wouldn't think that would be troublesome. You might contact your dealership and ask their opinion.
Using Flintknapper’s numbers the the difference between the two ratios is around 5.5%.

Seems the net result would be a 5.5% change in speed of the front wheels VS the rears when the replacement tires were installed Relative to the original spec. This is change in the original FRONT WHEEL speed, NOT THE FRONT BACK SPEED DIFFERENCE.

Assuming the original spec for front wheel over speed is something like 2 to 3%, this overspeed would change by 5.5%, so 2% would become 2% +/- (2*.055) = 2% +/- .11%. So the net result wold be you would end up with 1.89% or 2.11%, depending if it ended up being a slow down or speed up. I would not expect this to be an issue. If the original ratio was speed increase of 3%, these numbers would change by a factor of 1.5.

Edit: I was trying to say while the percent would remain the same, when the difference goes up from 2% to 3%, the +/- amount of speed change also goes up by a factor of 1.5. The percentage remains the same.

This is my take on it anyway…
 
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MAArcher

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Is there anything I should look out for or monitor to make sure these tires aren't damaging anything? I'm assuming it might be a little like driving a 4WD truck on dry pavement, you'll feel binding when you turn or something like that?

Thanks for all the info!
 

North Idaho Wolfman

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Buy the tire and rims, install, place the tractor on a flat hard surface.
Engage the 4wd, put the tractor in neutral, push the tractor by hand.
If it will easily pushes for about 5 feet you should be fine, if it starts binding earlier then DO NOT use it in 4wd ever.
You could get smaller or larger front or rear tires later on to make it work properly .
 
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Dale Strobridge

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I have exactly that set of Bridgestone turf tires on mine, Front 20.5X8.00-10, Rear 31X13.5-15. The front tire size are extinct. All I can find now are 20X8.00-10 which are 1/2 inch shorter. Will this be a large enough difference to smoke my axle or 4WD transfer case ?
 

cthomas

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A quick google search a found this

I don't think .5 inches narrower will hurt anything, but compare RC.
 

torch

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But for routine weekly mowing I'd be using these turf tires so I don't tear the yard up.
Mowing with what? If you have a mid-mount mower, the reduced clearance underneath the tractor may be an issue.

As long as you leave it in 2wd, the ratio does not really matter. It's only when you try to engage both axles that the driveline tries to tear itself (and/or the lawn) apart.
 

N3BP

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We were just discussing this the other night on another thread, but Kenda makes a true turf tire in 20.5X8.00-10. It's the model K513. Everything else out that in this rare size is a trailer tire, and they are not the same. A true turf tire will have lugs designed to bite into grass, but not enough to damage it.

If you preform the test Wolfman talks about in post# 10 with 20X8.00-10 tires on the front, you will feel it drag. I doubt it would damage the driveline, but you're defiantly going to wear the front tires down quicker. 20.5's make the driveline smooth as butter.

 

GreensvilleJay

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Kinda curious about needing 4WD for mowing a lawn. If you really require 4WD, I'm beting 'turf' tires aren't the proper type of tire ??
 

N3BP

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Kinda curious about needing 4WD for mowing a lawn. If you really require 4WD, I'm beting 'turf' tires aren't the proper type of tire ??
I have a sand mound in the rear of my property and it cannot be mowed in 2wd, even when it's dry out. At the same time, I don't want R1's ripping the yard apart. So turf's in 4wd is the ticket.
 

lubbadubb

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I can get a deal on turf tires on rims. The sizes are:
Fronts 20.5x8-10
Rears 31x13.5-15
And they reportedly came of a B7200.

But tractor data says I need:
Lawn/turf front: 24x8.5-12
Lawn/turf rear: 13.6-16

Can I still use these tires?

Thanks!
wondering if you ended up getting these tires? if not can you send me the info? i need this exact size. if you did get them and arent using them, would you sell them to me? had to ask...
 

MAArcher

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Kubota B8200
Oct 6, 2022
100
42
28
New England
wondering if you ended up getting these tires? if not can you send me the info? i need this exact size. if you did get them and arent using them, would you sell them to me? had to ask...
Hello, they are currently on my machine. If you find the correct set of turf or industrials for an 8200, let me know and maybe we can swap. Otherwise I have to hold on to them, they are working good for not tearing up my lawn when I mow. Thanks