Bicycle Tire Question: Why Does Air Loss Affect Cycling Difficulty?

In summary, the conversation discusses the question of why a bicycle becomes heavier and harder to cycle when there is air loss in the tires. The main reason is the redistribution of the normal force, which creates a torque on the wheel and requires more effort to overcome. The conversation also touches on the effect of soft tires and the redistribution of the normal force on the wheel.
  • #1
fotonios
9
0
bicycle tires question...

ok...heres a question that was given in the interview to a student who wanted to study physics at cabridge university.

why when there is air loss in the tires of a bicycle(pressure decrease)...the bicycle becomes(heavier)?,meaning...harder to cycle.
 
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  • #2
There is a bunch of energy that goes into deforming the rubber of the tires and shifting the air around that doesn't get used if the tires are filled.
 
  • #3
Originally posted by NateTG
There is a bunch of energy that goes into deforming the rubber of the tires and shifting the air around that doesn't get used if the tires are filled.

thats true...but its not by far the main reason of the huge difference in the effort u have to put into continue cycling.

pls try again!
 
  • #4
I have always assumed that it was the greater area of contact between the the tire and the road which caused greater rolling resistance thus low pressure tires are MUCH harder to push down the road.

Is there more?
 
  • #5
Originally posted by Integral
I have always assumed that it was the greater area of contact between the the tire and the road which caused greater rolling resistance thus low pressure tires are MUCH harder to push down the road.

Is there more?

the (point),(area...) of contact of the tire with the road is stationary...the tyre at that point does't move with respect to the road...so there is no point of discusing resistance due to friction.(so the greater area of contact is irrelevant in that respect).

TRUE there is greater resistance in the rolling of the (wheel) tire...but what causes it?

i have given u a strong hint now.
 
  • #6
Originally posted by fotonios
TRUE there is greater resistance in the rolling of the (wheel) tire...but what causes it?
I would expect that the major effect of soft tires is this: the tire is squashed forward and bunched up---essentially pulled away from the rim. In turn, the rubber pulls against the rim, creating a torque on the wheel that must be overcome to keep riding.

Looked at in terms of external forces, the normal force (the ground pushing the tires up) has been redistributed. In a firm tire, the normal force is directly underneath the center of the wheel. In the soft tire case, the normal force is now squashing the rubber in front of center. Thus the normal force now exerts a torque on the wheel.
 
  • #7
Originally posted by Doc Al
I would expect that the major effect of soft tires is this: the tire is squashed forward and bunched up---essentially pulled away from the rim. In turn, the rubber pulls against the rim, creating a torque on the wheel that must be overcome to keep riding.

Looked at in terms of external forces, the normal force (the ground pushing the tires up) has been redistributed. In a firm tire, the normal force is directly underneath the center of the wheel. In the soft tire case, the normal force is now squashing the rubber in front of center. Thus the normal force now exerts a torque on the wheel.

you got it!
good thinking!
and good and complete explanation...not just a dry answer.
you should apply for cabridge...:)
 
Last edited:
  • #8
Ahhh! Beautiful! It makes very good sense now.

Thanks for completing a picture for me.
 
  • #9
I am not fully convinced. Wouldn't the normal force also act (equally) on the other side of the axis of rotation, that is, at the back end of the footprint?
 
  • #10
Originally posted by Moose352
Wouldn't the normal force also act (equally) on the other side of the axis of rotation, that is, at the back end of the footprint?
No, since the "footprint" is not symmetric. The footprint is distorted towards the front.
 

1. How do I know when it's time to replace my bicycle tires?

The general rule of thumb is to replace your bicycle tires every 2,000-3,000 miles. However, factors such as riding style, terrain, and tire quality can affect this timeframe. It's important to regularly check your tires for wear and tear, such as cracks, cuts, or bald spots, and replace them when necessary.

2. What is the difference between clincher and tubeless tires?

Clincher tires are the most common type of bicycle tires and are held in place by inner tubes. Tubeless tires, on the other hand, do not require inner tubes and are sealed directly onto the rim. Tubeless tires offer better puncture resistance and a smoother ride, but they can be more difficult to install and maintain.

3. How do I choose the right tire width for my bicycle?

The width of your tire will depend on your riding style and preferences. Wider tires (1.5-2 inches) provide more stability and traction, making them ideal for off-road or mountain biking. Thinner tires (under 1.5 inches) are better for speed and efficiency on smooth surfaces. Consider your typical riding conditions and choose a tire width that best suits your needs.

4. Do I need to replace both tires at the same time?

It is recommended to replace both tires at the same time for optimal performance and safety. If one tire is significantly more worn than the other, it can affect the handling and stability of your bike. However, if you are on a tight budget, you can replace one tire at a time, just make sure to choose a tire with similar characteristics to your existing one.

5. How do I properly maintain my bicycle tires?

Regular maintenance is key to extending the lifespan of your bicycle tires. Keep them properly inflated to the recommended pressure, which can usually be found on the sidewall of the tire. Check for any signs of wear and tear and replace tires when necessary. Also, make sure to clean your tires regularly and avoid riding on rough or sharp surfaces to prevent punctures.

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