C-Series Backhoe Loader Ride Troubleshooting Guide Caterpillar

Problem:

Some ride related complaints concerning loping, also called "porpoising", have been received. The ride dynamics of the backhoe loader are very complex. There is no solution that will improve the ride for all machine configurations driving on all types of ground surfaces without making drastic changes to the machine or without adding a suspension system to the machine.

Therefore, this is a list of suggestions or methods that have been known to make some improvement in the ride of the backhoe loader. They are listed in the order in which they should be tried.

Solution:

1. Insure that the seat is properly adjusted for the operator. When possible, position the seat in the middle or upper height adjustments. These positions allow more seat travel than the lower positions. The larger seat travel distances reduce the likelihood that the seat will hit the bottom stop in its suspension system while roading.

When properly adjusted, the seat should not contact excessively on the top or bottom stop. Set the adjustment dial to the weight of the operator to get an approximate setting. Use trial and error to fine tune the seat. If the seat seems to contact excessively at the bottom of the seat travel, increase the adjustment. If the seat contacts excessively on the top of the seat travel, decrease the adjustment.

2. Early in the C-Series production, the seat damper was changed to a stiffer unit. This change increased the effectiveness of the seat suspension. Check the serial number on the sticker affixed to the back side of the seat back.

If the serial number is less than 101,784 for machines manufactured in the United States, or 6,247 for machines manufactured in the United Kingdom, replace the former arm assembly and shock absorber. Replace the 132-9231 Suspension Arm Assembly with the 150-1549 Suspension Arm Assembly and the 8Y-5965 Shock Absorber with the 150-1550 Shock Absorber.

3. Check to insure that the tires are at their recommended pressure. The recommended pressures for backhoe loader tires are listed above.

4. If the machine in question has radial tires, consider replacing the rear tires with bias ply tires. If the ride is still not acceptable, replace the front radial tires with bias ply tires. At their recommended pressure levels, bias ply tires have about 40% more damping ability than radial tires.

The damping force of bias ply tires is still minimal, but the change from radial tires to bias ply tires can yield a marked improvement in ride quality. This phenomena is particularly noticeable in heavy machine configurations (AWD, IT, Estick) and less noticeable for the light machines configurations.

The customer should be made aware that there are still advantages to radial tires over bias ply tires. Radial tires have better puncture resistance, longer life, and better traction than bias ply tires, but the ride quality will be compromised.

5. Check to insure that the machine has the proper counterweighting for the machine configuration. Proper counterweighting should yield a minimum of 25% of the total machine weight on the front axle. In general, changing from the bumper to the first counterweight increases the percentage by 1.7%. Each additional counterweight increases the percentage by 1.2%.

It is a common misconception that the more weight placed on the front axle produces a better ride. While this may be true for operations such as truck loading where the machine is accelerated forwards and backwards repeatedly and it is necessary to keep the front wheels weighted and on the ground, it does not necessarily mean the machine will lope less while roading.

In fact, it has been observed that too much weight on the front end can actually make the machine prone to loping. The benefit of more counterweighting is too dependent on the machine configuration and the ground profile to recommend an "optimum" counterweight configuration.

However, ride quality is a customer perception. Some customers feel that a more heavily weighted machine rides better. Try to increase the counterweighting to see if the customer likes the change in the ride.

6. If the above ride improvement methods fail to give a machine a satisfactory ride, tire air pressure adjustments may be used as a last resort.

Try reducing tire pressure in the rear tires. Do not reduce the tire pressure by more than 5 psi below the recommended pressure. Road test the machine to determine the effect on the ride.

Next, try increasing the pressure in the front tires. Do not increase the tire pressure by more than 5 psi above the recommended pressure. Road test the machine to determine the effect on the ride.

Lastly, try reducing the front tire pressure. Do not reduce the tire pressure by more than 5 psi below the recommended pressure. Road test the machine to determine the effect on the ride.

Make the customer aware that the tire pressure adjustments have their disadvantages. Tire life, fuel economy, and side slope stability may be compromised.

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