Tire Combination Guidelines, Up To 40 km/h (25 mph)

The size ratio of front wheels to rear wheels must produce a 1 % to 6 % on tractors with PowrQuad and PowrQuad PLUS transmissions.

NOTE: In order to choose proper tire combination, MFWD clutch ratio for your tractor needs to be identified.

IMPORTANT: Any time a new brand or tire size is selected, see your John Deere dealer for recalibrating tractor controllers and radar.

Available tires are grouped by rolling circumference (RC).

Rear tire groups 44, 45, and 46 are available for 7330 tractors. The target rolling circumference for each group is shown below.

NOTE: Table shows target rolling circumference and should NOT be used to calculate front wheel lead. Exact rolling circumference values vary for each tire size. Use rolling circumference information from your tire dealer to calculate front wheel lead.

Tire Groups and Target RC

Group 39 - Front

3850 mm (151.6 in.)

Group 40 - Front

4055 mm (159.6 in.)

Group 41 - Front

4275 mm (168.3 in.)

Group 44 - Rear

5000 mm (196.9 in.)

Group 45 - Rear

5270 mm (207.5 in.)

Group 46 - Rear

5550 mm (218.5 in.)

Tires of the same size but different brand name, as well as different size tires within the same RC group, may have slightly different rolling circumferences than their target values. Therefore, it is necessary to verify front wheel lead using procedure below.

Front tire group must be five groups lower than rear tire. This results in front/rear tire group combinations of 39/44, 40/45 and 41/46.

Front Wheel Lead Verification Procedure

  1. Select tires with suitable load-bearing capabilities.

  2. Select tires appropriate for tractor's top speed.

  3. NOTE: DO NOT use estimated rolling circumference values in previous table to calculate front wheel lead. Exact rolling circumference values vary for each tire size. Use rolling circumference information from your tire dealer.

    Obtain rolling circumference for replacement front and rear tires from your tire dealer.

  4. Use tractor's model, transmission and MFWD clutch ratio in following chart to find front axle-to-rear axle speed ratio needed to calculate front wheel lead.

    Model/Transmission

    MFWD Clutch Ratio

    Front Axle-to-Rear Axle Speed Ratio (AR)

    7330, PowrQuad and PowrQuad PLUS

    1.760

    1.800

    1.341

    1.311

  5. Calculate front wheel lead (overspeed), using following formula:

    FL = RCF x AR ÷ RCR, where:

    FL = Front Wheel Lead

    RCF = Rolling Circumference — Front Tire

    RCR = Rolling Circumference — Rear Tire

    AR = Front Axle-to-Rear Axle Speed Ratio

    Resulting front wheel lead should be between 1.01 (1%) and 1.06 (6 %) for PowrQuad or PowrQuad PLUS transmission.

    SAMPLE CALCULATION:

    • Tractor Model: 7330 with PowrQuad Plus transmission, MFWD clutch ratio of 1.760

    • Group 41 front tire, 16.9R28, with RCF = 4242 mm

    • Group 46 rear tire, 20.8R38, with RCR = 5436 mm

    • From the chart, front axle-to-rear axle ratio (AR) for this tractor = 1.341

    • Applying formula: 4242 x 1.341 ÷ 5436 = 1.0464 (4.64 %)

    • Front wheel lead (FL) is between 1.01 (1%) and 1.06 (6%). Tire combination is acceptable.

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