What determines optimal wheel size?

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In summary, the conversation discusses the reasons for different wheel sizes in heavy machinery, trains, bicycles, and their impact on factors such as weight distribution, speed, and rolling resistance. The use of larger wheels in trains is primarily due to lower rolling resistance and ease of bearing selection, while in bicycles, wheel size greatly affects torque and RPM. In addition, the design of steel on steel rolling is more similar to that of roller bearings and requires careful consideration of contact stresses.
  • #1
SkepticJ
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As a lay person I've wondered this for a while.

Obviously heavy machinery that rolls on dirt and mud needs large tire/wheel diameters and widths to spread their weight out to an acceptable ground pressure, eventually having to switch over to cat tracks when larger wheels start to give negative returns.

But what about trains? They roll across the hardest, smoothest surfaces that anyone could reasonably wish for, but their wheels are still proportionally quite large. Why? Why are bicycle wheels so huge? At least for road bikes; for mountain bikes it makes more sense.
 
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  • #2
Smaller wheels need higher RPMs to travel the same distance. Bigger wheels more easily travel at high speeds but at the sacrifice of torque.

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  • #3
Rolling resistance is proportional to 1/r of the wheel, so a large wheel has lower overall rolling resistance. Larger wheels also have lower angular velocity (RPM) at speed, making bearing selection easier. Still, I think rolling resistance is the biggest factor.

See here: http://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html
 
  • #4
Steel on steel rolling design is much different from pneumatic tires. It is more like roller bearing design. Care must be taken to make sure contact stresses are acceptable. Wheel diameter figures significantly in that set of tradeoffs.
 

1. What factors should be considered when determining optimal wheel size?

There are several factors that should be taken into account when determining optimal wheel size. These include the weight of the vehicle, the intended use of the vehicle, the terrain it will be driven on, and the desired level of performance.

2. How does wheel size affect vehicle performance?

The size of the wheels can greatly impact the performance of a vehicle. Larger wheels typically provide better traction and stability, while smaller wheels can improve acceleration and maneuverability. However, larger wheels also tend to be heavier and can negatively affect fuel efficiency.

3. Is there a standard optimal wheel size for all vehicles?

No, there is no one standard optimal wheel size for all vehicles. The optimal wheel size will vary depending on the specific vehicle and its intended use. For example, a sports car may have larger wheels for better handling, while a truck may have larger wheels for off-roading purposes.

4. How can I determine the optimal wheel size for my vehicle?

The best way to determine the optimal wheel size for your vehicle is to consult with a professional mechanic or use online calculators that take into account factors such as tire size, vehicle weight, and suspension characteristics. It is important to also consider your personal preferences and driving style.

5. Can changing the wheel size on my vehicle have any negative effects?

Yes, changing the wheel size on your vehicle can have potential negative effects. It can affect the accuracy of the speedometer and odometer, put extra strain on the suspension and brakes, and potentially void the vehicle's warranty. It is important to carefully consider and research before making any changes to the wheel size of your vehicle.

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