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Ascertain tire data:
This information must be ascertained from the tire manufacturer's manual.
1.
Select tires with suitable load-bearing capability.
2.
Select tires appropriate to the tractor's top speed.
3.
From the manual, ascertain the rolling circumference of the tire desired for the rear wheel.
4.
From the manual, ascertain the rolling circumference of the tire desired for the front wheel.
Ascertain the following data:
1.
The difference in rolling circumferences between the front and rear tires must be between 945 mm (37.2 in.) and 1618 mm (63.7 in.).
2.
Calculate the rolling circumference ratio of the rear tire to the front tire.
Go to line (F -K) in the table below that applies to the gear pair on your tractor and find the value that corresponds to the calculated rolling circumference ratio. The column gives the front wheel lead that may be achieved with the tire combination. If the calculated ratio does not lie within the range of values stated, either select a different tire combination or change the gear pair for the front wheel drive axle.
IMPORTANT:
The largest front tires on 6010, 6110 and 6210 tractors must not exceed an index radius of 610 mm (24.0 in.). The largest front tires on 6310 and 6410 tractors must not exceed an index radius of 620 mm (24.4 in.).
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If a new pair of tires is selected for a tractor with cab, the basic informator (BIF), the Basic Control Unit (BCU) and ground speed sensor (radar) must be recalibrated. See your John Deere dealer.
Example
The intention is to fit a tractor with 18.4-38 / 14.9-24 tires, made by a certain manufacturer.
The differential gear pair is 47/10.
The transmission ratio of the front axle is 15,89.
The transmission ratio of the gear pair at the front wheel drive axle is 1,497 (= gear pair H).
According to the tire manufacturer's manual, the desired tires have the following rolling circumferences:
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18.4-38 = 5203 mm (205 in.)
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14.9-24 = 3795 mm (149.4 in.).
The difference between the rolling circumferences is 1408 mm (55.4 in.), i.e. within the acceptable range.
The ratio of rolling circumferences is:
| 5203 mm (205 in.) |
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= 1,371 |
| 3795 mm (149.4 in.) |
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In the table below, the line with gear pair H includes the figure 1,369, which is sufficiently close to the calculated value of 1,371. The front wheel lead of the desired tire combination is therefore 2%.
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