Help with tires please!

[406nick]

So I need a new front tire on my gray market b6000 but I really don't want to have to buy a whole new set if possible. The owner before me let the tractor sit with a flat for far too long which rotted the bead. Tread and everything is still good (as is the other tire) but I don't see any way to salvage this tire.
As much as I use it I can't justify spending 150 bucks for new tires so I am looking for used ones. I have found a place that sells used tires but the ones I saw on their website are 5.00x12 instead of 5-12 which is what my tire reads. Why is it so critical to keep the same size tire? And if just the diameter is critical could a person go to a 4.00x12?? I don't know much about the tractor but if you were to replace them as a set would the different size be a big deal?
Again I am pretty clueless when it comes to tires so hopefully someone can help me understand what I need to look for or give me some options.

 

[hodge]

So I need a new front tire on my gray market b6000 but I really don't want to have to buy a whole new set if possible. The owner before me let the tractor sit with a flat for far too long which rotted the bead. Tread and everything is still good (as is the other tire) but I don't see any way to salvage this tire.
As much as I use it I can't justify spending 150 bucks for new tires so I am looking for used ones. I have found a place that sells used tires but the ones I saw on their website are 5.00x12 instead of 5-12 which is what my tire reads. Why is it so critical to keep the same size tire? And if just the diameter is critical could a person go to a 4.00x12?? I don't know much about the tractor but if you were to replace them as a set would the different size be a big deal?
Again I am pretty clueless when it comes to tires so hopefully someone can help me understand what I need to look for or give me some options.

Is your tractor 2WD or 4WD? If 2WD, it is no issue- you can change the size of the front tires. If you have a 4WD, the tires need to be the same diameter, or the ratio between front and back will be off. Then, it will bind up in 4WD, because the front tires are traveling a different distance in ratio to the rear, and the more you roll, the more it tightens up.

 

[406nick]

It is a 4wd. So if I measure the diameter of the tire and the new ones are close to the old ones I should be fine shouldn't I? I found some used tires that are 4.00x12 that I believe are 20.3" in diameter and I think the 5-12 tires are 20.8" in diameter. A little narrower but heck for the cost seems like they should work. I can't imagine be a half inch smaller would be a big deal since I'm sure tires can wear that much.

 

[lsmurphy]

1/2" taller is a big deal........changes the rolling circumference.

But in your case I don't think it matters much.

 

[olthumpa]

It is a 4wd. So if I measure the diameter of the tire and the new ones are close to the old ones I should be fine shouldn't I? I found some used tires that are 4.00x12 that I believe are 20.3" in diameter and I think the 5-12 tires are 20.8" in diameter. A little narrower but heck for the cost seems like they should work. I can't imagine be a half inch smaller would be a big deal since I'm sure tires can wear that much.

[FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif]Circumference = Pi (3.14) times Diameter (C=p[FONT=Verdana, Arial, Helvetica, sans-serif]D)[/FONT][/FONT][/FONT]
[FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Verdana, Arial, Helvetica, sans-serif]so: 3.14 X 20.3 = 63.742[/FONT][/FONT][/FONT]
[FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Verdana, Arial, Helvetica, sans-serif] 3.14 X 20.8 = 65.312
[/FONT][/FONT][/FONT]
= 1.57 inches difference in circumference
Now take the diameter of your rear tires multiply it by 3.14, call this number Y
divide Y by [FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Verdana, Arial, Helvetica, sans-serif]63.742 = A
[/FONT][/FONT][/FONT]divide Y by [FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=verdana, geneva, helvetica][FONT=Verdana, Arial, Helvetica, sans-serif][FONT=Verdana, Arial, Helvetica, sans-serif]65.312[/FONT][/FONT] = B[/FONT][/FONT][/FONT][/FONT]

Now subtract A from B this is the difference in inches that the narrower tires will fall short, ( have to slip), to cover the same distance as one revolution of the back tire. You will find that this adds up quickly. You now have stress between the right front tire and left front tire and stress between the front axle and the rear axle.

If you brake an axle , gear, bearings etc, you will find the price of a set of matching tires to be CHEEP and then you will have to still buy a set of matching tires or risk doing it again..

 

[406nick]

Ok that makes a lot more sense now that you explained it like that. So the rolling circumference should be close between the front and rear. So I could measure my rear and might actually find that one of those tires could be better than whats on there just by matching the size.
Is there a rule of thumb on how much difference there can be? Obviously no difference would be the way to be but I can't help but think there will be some.
Anybody know where a person can get a set of used 5-12 tires?
And thanks everyone for the help! Again I have no clue what I am doing with tires but I don't want to mess anything up!