Friction and Motion: Exploring the Impact of Tire Inflation on Resistance

In summary, the conversation discusses the concept of rolling resistance and how it is different from traditional friction. It explains that rolling resistance is affected by the deformation of the tire and surface, rather than just the contact area. This leads to the understanding that underinflated tires have more rolling resistance due to increased deformation, which can be beneficial in certain situations such as climbing over rocks or driving through sand.
  • #1
A Physics Enthusiast
If friction is independent of area of contact, how do less inflated tires of a bicycle experience more resistance towards motion than the well inflated tires?
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
  • Like
Likes sophiecentaur
  • #3
T13091999 said:
If friction is independent of area of contact, how do less inflated tires of a bicycle experience more resistance towards motion than the well inflated tires?
Take an uninflated tyre and 'knead' it with your hands. When you cycle on a soft tyre, you are actually doing this to every bit of the tyre as it comes into contact with the ground. A hard tyre may rattle your teeth but it takes much less energy.
P.S. Steel wheels on steel rails are highly efficient.
 
  • #4
sophiecentaur said:
Take an uninflated tyre and 'knead' it with your hands. When you cycle on a soft tyre, you are actually doing this to every bit of the tyre as it comes into contact with the ground. A hard tyre may rattle your teeth but it takes much less energy.
P.S. Steel wheels on steel rails are highly efficient.
I have failed to understand this. Do you mean that the deformation of the tyre takes away the "effort" ? (Sorry for the not-so-proper terminology)
 
  • #5
A Physics Enthusiast said:
I have failed to understand this. Do you mean that the deformation of the tyre takes away the "effort" ? (Sorry for the not-so-proper terminology)
The forward motion of the bicycle requires continual deformation of the tires as they roll. This deformation consumes energy beyond what is required to overcome friction.
 
  • #6
A Physics Enthusiast said:
I have failed to understand this. Do you mean that the deformation of the tyre takes away the "effort" ? (Sorry for the not-so-proper terminology)
The hysteresis in the deformation involves a loss of energy. So the deformation takes away Energy. The word "effort" is used to describe a Force so it is not appropriate to apply it here, I think. Best to talk in terms of Work Done and work returned to the system.
 
  • Like
Likes jbriggs444
  • #7
A Physics Enthusiast said:
Do you mean that the deformation of the tyre takes away the "effort"?
Did you read the link in post #2?
 
  • #8
Friction is generally not independent of area of contact. That's an oversimplification used in introductory physics, and it's generally fairly accurate for hard objects sliding against each other, but when you get into complex situations like modern tires, both the contact area and the shape of the contact patch matter.

In addition, rolling resistance is yet another phenomenon that is independent of ordinary sliding friction. A wheel which is rolling is not sliding, so the sliding friction formula does not apply. Instead, rolling resistance has more to do with the deformation of the wheel and surface, and the energy needed to cause that deformation. As a result, a wheel which deforms less will have less rolling resistance, leading to the tire pressure dependence you talked about.
 
  • #9
A.T. said:
Did you read the link in post #2?
Yes. Wikipedia says that deformation of the tyres contributes to rolling friction. I got confused as I wasn't able to link that concept with the concept of friction being independent of area.
 
  • #10
A Physics Enthusiast said:
Yes. Wikipedia says that deformation of the tyres contributes to rolling friction. I got confused as I wasn't able to link that concept with the concept of friction being independent of area.
Some wikipedia articles are quite good, some not so much, and some are generally OK but carelessly written so can be confusing. You've been victimized by one of that last kind.

(Stuff like this is the reason why wikipedia is not a generally accepted reference under the PF rules, although we will routinely refer people to particular entries that do fall in the "quite good" category.)
 
  • Like
Likes A Physics Enthusiast
  • #11
A Physics Enthusiast said:
I have failed to understand this. Do you mean that the deformation of the tyre takes away the "effort" ?
Yes, energy is lost in the continuous deformation of the underinflated tire as it rotates. It has nothing to do with the friction between the tire and the road. Have you been able to start understanding this effect now because of the responses in the thread? :smile:

https://www.physicsforums.com/threads/awesome-motorbike-skills.937405/#post-5928180

tirepressurestory_04-jpg.jpg


EDIT/ADD -- Bonus Quiz Question related to the question in your first post -- Why is underinflating tires good for climbing over rocks or riding/driving through sand? :smile:
 

Attachments

  • tirepressurestory_04-jpg.jpg
    tirepressurestory_04-jpg.jpg
    46.7 KB · Views: 346
  • Like
Likes sophiecentaur
  • #12
berkeman said:
Have you been able to start understanding this effect now because of the responses in the thread? :smile:
Yes. I need some time (exams are going on).
:blushing:
 
  • Like
Likes berkeman
  • #13
A Physics Enthusiast said:
Yes. Wikipedia says that deformation of the tyres contributes to rolling friction. I got confused as I wasn't able to link that concept with the concept of friction being independent of area.
Why are you trying to link it to something you learned about "friction"? The wiki article explains right at the start why "rolling friction" is a misnomer.
 

1. What is friction and why is it important in motion?

Friction is the force that resists the relative motion between two surfaces that are in contact with each other. It is important in motion because it can either hinder or aid the movement of objects and is a key factor in determining the amount of energy needed for an object to overcome resistance and move.

2. How does tire inflation affect friction and resistance?

Tire inflation affects friction and resistance by altering the contact between the tire and the road surface. When tires are properly inflated, they have a larger contact area with the road, resulting in more friction and better traction. This can reduce resistance and improve the overall efficiency of motion.

3. What is the relationship between tire pressure and friction?

The relationship between tire pressure and friction is inverse - as tire pressure increases, the contact area between the tire and road decreases, resulting in less friction. This can lead to reduced traction and increased resistance, making it harder for the vehicle to move.

4. How does tire inflation impact fuel efficiency?

Proper tire inflation can significantly impact fuel efficiency. Under-inflated tires can cause increased resistance and drag, leading to a decrease in fuel efficiency. On the other hand, over-inflated tires can also result in reduced fuel efficiency due to the decreased contact area and increased wear and tear on the tires.

5. How can we measure the impact of tire inflation on resistance?

The impact of tire inflation on resistance can be measured through experiments or simulations that compare the performance of tires at different inflation levels. This can include measuring the distance a vehicle can travel with different tire pressures, as well as the amount of energy needed to overcome resistance and maintain a constant speed. Additionally, specialized tools such as dynamometers can be used to measure the force and resistance experienced by tires at different inflation levels.

Similar threads

Replies
6
Views
827
Replies
22
Views
1K
Replies
5
Views
1K
Replies
8
Views
3K
  • Mechanics
Replies
31
Views
637
Replies
18
Views
2K
Replies
24
Views
3K
  • Mechanics
Replies
10
Views
4K
Back
Top