What should not be mixed on the steering axle of a vehicle?

Mixing radial and bias tires on the steering axle of a vehicle is not advisable because these two types of tires have different construction designs and performance characteristics. Radial tires have layers of cord running at a 90-degree angle to the direction of travel, allowing for a flexible sidewall that provides better traction, improved fuel efficiency, and longer tread life. In contrast, bias tires have layers of cord crisscrossed over each other, which can lead to a stiffer and less stable ride.

When both types are used on the same axle, the handling of the vehicle can become unpredictable, especially during turns or when encountering uneven surfaces. This situation increases the risk of losing control, leading to potential accidents. Proper tire matching is essential for maintaining vehicle stability and ensuring safe operation.

While the other answer options highlight issues that can affect performance and safety, they do not cause the same significant control problems as mixing radial and bias tires on the steering axle. For instance, buses and trucks can have different tires suitable for their specific use cases, and mixing new and used tires on an axle could be managed carefully by monitoring tread depth. However, none of these combinations inherently disrupt the steering dynamics to the extent that mixing radial and bias tires does.