CHAPTER 19 ■ WHEELSSolid tires wear well but don’t grip as well, nor do they absorb bumps as well as pneumatic tires.
However, because they don’t squish, they add fewer errors to precision movements.
Tire Shapes
Tire shape makes a significant difference in traction and resistance. Look at the shape of the curve of the top
of the tires in Figure 19-3. Some have broad, sloping shoulders; others have brief, square shoulders.
A rounded cross section tire, similar to a bicycle tire, only has a tiny portion touching the ground at
any point. Because there is less contact with the surface, these tires are easy to turn and have a low-rolling
resistance. Rolling resistance is the amount of friction generated against the road, which determines how
easily the tire rolls forward and backward. Because of the limited road contact, rounded tires are more
energy efficient, and thus a good choice for long-endurance runs.
Balloon tires protrude a bit over the sides of the rims. Balloon tires absorb shock well and can handle
uneven surfaces. They’re preferred for off-road and rough surfaces.
There are some in-between tire shapes on which the center portion is slightly flattened, but drops off at
the shoulders. This offers a balance of characteristics, not being the best or worst performer in any category.
Flat tires provide the greatest traction on flat surfaces. This makes them great for delivering motor
power to the road, although with the expense of having the highest-rolling resistance. Choose a flat tire
shape for maximum pushing, pulling, and acceleration on smooth surfaces.
Tire Width
Greater width usually provides greater stability and traction to a tire, no matter what its shape (see Figure 19-4).
Wide tires are also less likely to become stuck in parallel-aligned surface grooves.
Figure 19-3. Left to right: Rounded, balloon, hybrid, and flat