Usage:
All Backhoe Loaders Equipped With Four Wheel Drive (4-WD)
Caterpillar has received numerous questions and/or complaints concerning front tire wear and noise that may occur when 4-WD is disengaged when the machine is moving. This article provides some answers to those concerns.
In general, the front tires on a 4-WD Drive Backhoe Loader will wear more rapidly than the front tires used on a 2-WD Backhoe Loaders.
-
- A. Unloaded Condition
By design, 4-WD backhoe loaders have the smaller front wheels traveling from 2% to 5% faster than the rear wheels. This difference provides a positive tractive effort from the front wheels. Since the front wheels travel faster and with 70% to 75% of the tractor's weight on the rear wheels, almost all this slippage will occur at the front wheels. On soft and/or slippery surfaces, this slippage can occur with little tire wear. The opposite is true on hard surfaces. This slippage still has to occur and front tire wear will be accelerated. Customers should be encouraged to shift out of 4-WD when it is not required.
- B. Loaded Condition
As load is applied to the loader bucket, the rolling radius of the front tire will be reduced. This smaller radius reduces the difference in travel speed between the front and rear wheels. With a fully loaded bucket, the difference in travel speed may approach zero (in some materials, the ratio may even go to a negative value). In summary, as load is applied, the amount of slippage that must occur is reduced.
- C. Tire Size
Caterpillar has selected a specific tire brand and size to assure the optimum ratio between the front and rear wheels. These tires have known values for load carrying capacity, loaded and unloaded rolling radius which are critical for maintaining the correct ratios.
Other tire brands labeled for the same size may vary in circumference, rolling radius, etc. by as much as 3%. This difference could cause tire wear to accelerate even more.
- D. To Maximize Tire Life
1. Use correct tire inflation.
2. Use correctly sized tires.
3. Disengage 4-WD when additional traction is not required. Also disengage 4-WD when "roading" the machine on paved surfaces.
4. Limit or restrict the use of brakes to slide the front wheels around sharp turns.
- A. Unloaded Condition
Engagement and Disengagement Noise
Caterpillar Backhoe Loaders have the capability to engage or disengage the 4-WD while moving. Some noise (a "clunking" sound) may be generated when the 4-WD is disengaged on the run. This noise is caused by normal gear backlash and the release of energy (torque) in the front drive line (tires, shafts, etc.). The level of noise will vary, depending on load, speed, and/or sharpness of turn being made. This noise ("clunk") is normal and is not detrimental to the 4-WD.