Calculate Tire Combinations - (on 6140R and 6150R Tractors)

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:

Also see illustration in this section.

  1. The transmission ratio of the differential gear pair is “I3”. These values are displayed on the product information plate on the left side of the radiator. The following pairs are possible:

    Transmission ratio of differential ..............

    “I3”

     

    Gear pair

    		  

    PowrQuad™ transmission, 50 km/h

    AutoPowr™ transmission

    54/13

    4.154

    PowrQuad™ transmission, 40 km/h

    DirectDrive transmission

    49/10

    4.9

  2. The transmission ratio of the front axle is “I2”. This figure is displayed on the front axle serial number plate. The following ratios are possible:

    Transmission ratio of front axle ..............

    “I2”

    • 6140R ..............

    13.286

    • 6150R* ..............

    with TR up to 1.280 ..............

    13.846

    with TR over 1.281 ..............

    13.286

    IMPORTANT: *For 6150R tractors, the tire ratio (TR) between the front and rear wheels must be calculated; do this as follows:

    TR =

    A2

    		  

    A2 = Rolling circumference of rear tire

    A1

    A1 = Rolling circumference of front tire

  3. The transmission ratio of gear pair for front wheel drive axle output “I”. These values are displayed on the product information plate on the left side of the radiator. The following pairs are possible:

    Transmission ratio of front wheel drive axle output “I”

    PowrQuad™ transmission, 50 km/h

    AutoPowr™ transmission

    PowrQuad™ transmission, 40 km/h

    DirectDrive transmission

    • 1.455

    • 1.680

    • 1.708

    • 1.485

    • 1.720

    • 1.750

    • 1.515

    • 1.760

    • 1.792

    • 1.545

    • 1.800

    		  

Ascertain tire data:

  1. Select tires with suitable load capacity.

  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:

Calculate the overall transmission ratio using the following formula.

 

I =

A1 x I1 x I3 x 100

 

A2 x I2 x 102.75

A1 =

Rolling circumference of front tires

A2 =

Rolling circumference of rear tires

I1 =

Rear axle ratio is 6.40

I2 =

Transmission ratio of front axle

I3 =

Transmission ratio of the differential gear pair

102.75 =

A fixed value to determine the required front wheel lead

Ascertain the gear pair that is appropriate for the calculated overall transmission ratio.

Calculated
transmission ratio “I”

Transmission ratio of the required gear pair

(corresponds to a positive front wheel lead of 1.5 - 4.0%)

(corresponds to desired average value of positive front wheel lead)

PowrQuad™ transmission, 50 km/h

AutoPowr™ transmission

1.437 - 1.470

1.455

1.471 - 1.500

1.485

1.501 - 1.530

1.515

1.531 - 1.565

1.545

PowrQuad™ transmission, 40 km/h

1.659 - 1.700

1.680

1.701 - 1.740

1.720

1.741 - 1.779

1.760

1.780 - 1.822

1.800

DirectDrive transmission

1.687 - 1.729

1.708

1.730 - 1.772

1.750

1.773 - 1.820

1.792

Sample calculation

The intention is to fit a tractor with 710/70R38 and 600/65R28 tires, made by a certain manufacturer.

  1. The transmission ratio of differential gear pair “I3” is  4.9 .

  2. The transmission ratio of front axle “I2” is  13.286 .

  3. The transmission ratio of rear axle ”I1” is  6.40 .

  4. The transmission ratio of the currently installed gear pair “I” for front wheel drive axle output is 1.720.

  5. The rolling circumference of the tire “A2” on the rear wheel is  5780  mm (227.6 in.).

  6. The rolling circumference of tire “A1” on the front wheel is  4444  mm (175.0 in.).

  7. Calculate the overall transmission ratio.

 

4444 x 6.40 x 4.9 x 100

= 1.766

5780 x 13.286 x 102.75

The required gear pair must have the transmission ratio 1.760.

IMPORTANT: In this example, the gear pair that is currently installed for front-wheel drive axle output must be replaced with a different pair.

IMPORTANT: If the transmission ratio is changed, the following services must be performed by a John Deere™ dealer:

  • Change the gear pair for the front wheel drive axle output
  • Change tire size in the software of the control units
  • Calibrate the radar (tractors with radar only)

OULXA64,0002BF3-19-20130430