Tire Combinations (up to 50 km/h; 31 mph)
IMPORTANT:
Stay with tire dimensions as identified in Group A OR Group B. Tractor approval/ homologation

rules do not permit switching between groups.

Group A 





520/70R38 
Continental 
AC70T 
420/70R24 
Continental 
AC70T 



420/70R28 
Continental 
AC70T 
520/70R38 
Pirelli 
TM700 
420/70R24 
Pirelli 
TM700 



480/70R24 
Pirelli 
TM700 



380/70R28 
Pirelli 
TM700 



420/70R28 
Pirelli 
TM700 
600/65R38 
Continental 
AC65 
540/65R24 
Continental 
AC65 



480/65R28 
Continental 
AC65 
600/65R38 
Pirelli 
TM800 
540/65R24 
Pirelli 
TM800 



480/65R28 
Pirelli 
TM800 
Group B 





18.4R38 
Michelin 
XM25P 
14.9R24 
Michelin 
XM25P 



16.9R24 
Michelin 
XM25P 



13.6R28 
Michelin 
XM25P 



14.9R28 
Michelin 
XM25P 
18.4R38 
Michelin 
XM27 
14.9R24 
Michelin 
XM27 



16.9R24 
Michelin 
XM27 
460/85R38 
Kleber 
Traker 
380/85R24 
Kleber 
Traker 



420/85R24 
Kleber 
Traker 



340/85R28 
Kleber 
Traker 



380/85R28 
Kleber 
Traker 
520/70R38 
Continental 
AC70G 
420/70R24 
Continental 
AC70G 
520/70R38 
Kleber 
Fitger 
420/70R24 
Kleber 
Super 8L 



480/70R24 
Kleber 
Super 8L 



380/70R28 
Kleber 
Super 8L 



420/70R28 
Kleber 
Fitger 
600/65R38 
Kleber 
Super 11L 
540/65R24 
Kleber 
Super 11L 



480/65R28 
Kleber 
Super 11L 
600/65R38 
Michelin 
XM108 
540/65R24 
Michelin 
XM108 



480/65R28 
Michelin 
XM108 
The size ratio of the front wheels to the rear ones is precisely determined in order to produce a positive front wheel lead of between 1.5 and 4%, otherwise the tires will become deformed or suffer undue wear. To ascertain the correct ratio when changing tires, proceed as follows:
Ascertain tractor data:
1.
Transmission ratio of the differential gear pair. This information is displayed on the transmission type plate. The following pairs are possible:


Gear pair 
Transmission ratio 

47/10 
4,700 
2.
Transmission ratio of front axle. This figure is displayed on the front axle type plate. The following ratios are possible:


OU12401,0000E5C 1901JUL031/3

3.
Transmission ratio of gear pair for frontwheel drive axle (output). This figure can be found on the transmission serial number plate. The following ratios are possible:

1,446

1,465

1,497

1,532

1,564

1,597

1,625

1,658

1,692

1,725

1,760

1,795

1,833

1,870

1,907

1,943

1,990

2,028
Ascertain tire data:
This information must be ascertained from the tire manufacturer's manual.
1.
Select tires with suitable loadbearing 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.
Calculate the difference between the rolling circumferences of the tires on the front and rear wheels.
IMPORTANT:
The largest front tires on 6020, 6120 and 6220 tractors must not exceed an index radius of 610 mm (24.0 in.). The largest front tires on 6320, 6420 and 6420S tractors must not exceed an index radius of 620 mm (24.4 in.).
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.
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 overall transmission ratio using the following formula:


A1 * I1 * I3 * 100 


I = 




A2 * I2 * 102,75 






A1 = 
Rolling circumference of front tires 

A2 = 
Rolling circumference of rear tires 

I1 = 
Rear axle ratio (7,0714) 

I2 = 
Transmission ratio of front axle 

I3 = 
Transmission ratio of the differential gear pair 
Ascertain the gear pair that is appropriate for the overall transmission ratio.


OU12401,0000E5C 1901JUL032/3

Calculated transmission ratio 
Transmission ratio of the required gear pair 
(corresponds to a pos. front wheel lead of 1.5  4.0%) 
(corresponds to desired average value of pos. front wheel lead) 
1,428  1,446 
1,446 
1,447  1,478 
1,465 
1,479  1,512 
1,497 
1,513  1,544 
1,532 
1,545  1,576 
1,564 
1,577  1,604 
1,597 
1,605  1,637 
1,625 
1,638  1,670 
1,658 
1,671  1,703 
1,692 
1,704  1,737 
1,725 
1,738  1,772 
1,760 
1,773  1,810 
1,795 
1,811  1,846 
1,833 
1,847  1,882 
1,870 
1,883  1,918 
1,907 
1,919  1,964 
1,943 
1,965  2,002 
1,990 
2,003  2,062 
2,028 
Sample calculation
The intention is to fit a 6420 tractor with 600/65R38 and 540/65R24 tires, made by a certain manufacturer.
1.
The transmission ratio of the differential gear pair is 4,700.

2.
The transmission ratio of the front axle is 15,692.
3.
The transmission ratio of the gear pair for the frontwheel drive axle is 1,532.
4.
The rolling circumference of the tire on the rear wheel is 5263 mm (207.2 in.).
5.
The rolling circumference of the tire on the front wheel is 3923 mm (154.4 in.).
6.
The difference between the rolling circumferences of the tires on the rear/front wheels is 1340 mm (52.8 in.), i.e. within the acceptable range.
7.
Calculate the overall transmission ratio.
3923 * 7,0714 * 4,700 * 100 


= 1,536 
5263 * 15,692 * 102,75 



The gear pair that is required must have a ratio of 1,532.


OU12401,0000E5C 1901JUL033/3

