Final answer:
The part of an under-inflated tire that still grips the road well is the tread. A wheel rim by itself is not very useful for driving as it needs a proper tire for safety and comfort. An under-inflated tire compromises the efficiency of the tire-rim combination and can lead to uneven tire wear and handling issues.
Step-by-step explanation:
If a tire is under-inflated, the only part that grips the road well is the tread. The side of a tire known as the sidewall is not designed to have contact with the road surface. Likewise, the bead is the part of the tire that ensures a snug fit onto the wheel rim, and the rim itself is the foundation to which the tire is fitted. An under-inflated tire causes most of the car's weight to be carried by the tread that sits at the edges of the tire, rather than being evenly distributed across the full tread surface. This can lead to uneven tire wear and potential handling problems.
How useful is a wheel rim? A wheel rim by itself is not very useful for driving. The rim is an essential component as it provides a base for the tire, but without a properly inflated tire, the combination of tire and rim cannot function effectively. Driving on just the rim without a tire will likely cause damage to the rim and result in an unsafe and uncomfortable ride. Therefore, it is important that a tire is properly inflated to ensure a safe and comfortable car ride, utilizing the design of both the tire and the rim to improve vehicle performance and safety.