|
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. These values are displayed on the product information plate on the l.h. side of the radiator. The following pairs are possible:
| |
Gear pair |
Transmission ratio |
| |
48/10 |
4,8 |
| |
52/10 |
5,2 |
2.
Transmission ratio of front axle. This figure is displayed on the front axle serial number plate. The following ratios are possible:
3.
Transmission ratio of gear pair for front-wheel drive axle output. These values are displayed on the product information plate on the l.h. side of the radiator. The following pairs are possible:
-
1,697
-
1,727
-
1,758
-
1,833
-
1,875
-
1,917
Ascertain tire data:
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:
IMPORTANT:
Tires used on the front wheels must have a Speed Radius Index (SRI) of 700 mm (27.6 in.).
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 (6.40) |
| |
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.
| 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) |
| 1,676 - 1,713 |
1,697 |
| 1,714 - 1,740 |
1,727 |
| 1,741 - 1,779 |
1,758 |
| 1,811 - 1,854 |
1,833 |
| 1,855 - 1,895 |
1,875 |
| 1,896 - 1,940 |
1,917 |
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 the differential gear pair is 5.2.
2.
The transmission ratio of the front axle is 13.160.
|