Why do smaller wheels on a car ?

  • Thread starter midget200
  • Start date
  • Tags
    Car Wheels
In summary, the conversation discusses the effects of smaller wheels on a car's acceleration rate. Some believe that smaller wheels result in a higher acceleration rate due to a higher effective gear ratio, while others argue that the difference may be negligible. Factors such as weight, torque, and tire size are also taken into consideration. Ultimately, it is suggested that smaller wheels may improve acceleration but may also decrease top speed. The conversation also mentions the potential for systematic errors in the science lab results and the importance of considering other factors before drawing conclusions.
  • #1
midget200
1
0
why do smaller wheels on a car...?

I recently had to do a science lab for school, and my guiding question was 'Does the size of a car’s wheel affect the acceleration rate?'

when i completed this lab, my results were that a smaller wheel affects the acceleration rate more then a bigger wheel. can anyone tell me why?
 
Physics news on Phys.org
  • #2


Strangely I think that in reality the size of the wheels doesn't affect the acceleration rate of the car. I believe that for a given power of the motor, the car will make rotates the wheels according to the power of the motor and not the size of the wheels. In other words if you put smaller wheels they will rotates faster than big ones but the car will accelerate at the same rate as if you would have put big wheels. I might be wrong though.
So it remains to you to find out why did you get these results. Maybe systematic errors... you're the only one that know how you did the lab.
 
  • #3


Welcome to PF, Midget.
The main difference is that smaller wheels give a higher effective gear ratio for the power train. That improves acceleration, but decreases the top speed.
 
  • #4


Danger said:
Welcome to PF, Midget.
The main difference is that smaller wheels give a higher effective gear ratio for the power train. That improves acceleration, but decreases the top speed.

True, but you can also consider the greater moment of inertia that comes along with bigger wheels as well. If you consider turning as acceleration, which it technically is, the size of the wheels has a very significant affect on the performance of the vehicle. Thy dynamics of which I won't go into unless requested as it gets rather complicated.

In application, wheels are made as small and as light as possible for a given amount of required traction. That is unless looks are important (which they are from a business stand point) then its just what ever size looks cool.
 
  • #5


If the engine and drive system is capable of delivering the required torque, 18-inch wheels will give you better acceleration than 15-inch. But there is a big initial jolt to the drive system in turning those 18-inch wheels along with a greater tendency for the wheels to hop on the track. As I recall the real pros used smaller diameter wheels that were wider and a bit under inflated or racing slicks to get best grip and smoothest acceleration. However, they would use larger diameter front wheels (for rear-wheel drive) to shift more weight on to the rear drive wheels to keep them firmly on the track.
 
  • #6


The slicks used on diggers give the best compromise, although you can't use them off the track. They're short and fat to start with at low rpm's, then grow to be quite tall and narrow as speed increases. It's like having a constantly variable axle ratio.
 
  • #7


midget200 said:
I recently had to do a science lab for school, and my guiding question was 'Does the size of a car’s wheel affect the acceleration rate?'

when i completed this lab, my results were that a smaller wheel affects the acceleration rate more then a bigger wheel. can anyone tell me why?
WHAT affect did the smaller wheels have? Did they help or hurt acceleration rate?
 
  • #8


Danger got it absolutely right:

The main difference is that smaller wheels give a higher effective gear ratio for the power train. That improves acceleration, but decreases the top speed.

The basic reason is a typical gasoline engine needs to get revolutions up to mid range to begin to develop significant torque...a faster turning wheel (smaller circumference hence smaller diameter) allows that to happen fastest...
 
  • #9


Smaller wheels or smaller radius tires? Smaller wheels with the same diameter tires produces a minor effect assuming the larger wheel and tire combo weigh more than the smaller wheel and tire.

A smaller radius tire would increase the effective gear ratio as stated by Danger.

The force at the rear tire equals the rear wheel torque divided by the radius. With the same rear wheel torque, if the radius is smaller, the force is larger. However the engine speed versus car speed is higher with a smaller radius, so you reach red-line rpms in the engine at a lower speed in each gear with a smaller radius.
 

1. Why do smaller wheels on a car affect the ride?

Smaller wheels affect the ride of a car because they have less surface area to grip the road, resulting in less stability and control. This can lead to a bumpier and less comfortable ride.

2. How do smaller wheels affect the handling of a car?

Smaller wheels can negatively impact the handling of a car because they have a smaller circumference, which means they have to rotate more times to cover the same distance as larger wheels. This can result in less responsive steering and slower acceleration.

3. Do smaller wheels improve fuel efficiency?

Yes, smaller wheels can improve fuel efficiency because they require less energy to rotate compared to larger wheels. However, this improvement is typically minimal and can be offset by other factors such as increased rolling resistance and a decrease in speedometer accuracy.

4. Are smaller wheels cheaper than larger wheels?

Generally, smaller wheels are cheaper than larger wheels because they require less material to produce. However, the cost difference may not be significant and can vary depending on the brand and type of wheels.

5. Can smaller wheels affect the braking performance of a car?

Yes, smaller wheels can affect the braking performance of a car. Smaller wheels have smaller brake discs and calipers, which means they may not have the same stopping power as larger wheels. This can result in longer braking distances and decreased safety.

Similar threads

Replies
22
Views
1K
Replies
4
Views
1K
Replies
9
Views
2K
Replies
15
Views
2K
  • Mechanics
Replies
10
Views
1K
Replies
7
Views
1K
  • Engineering and Comp Sci Homework Help
3
Replies
102
Views
4K
Replies
10
Views
2K
  • Mechanics
Replies
17
Views
2K
Back
Top