# How Much Friction is Desirable

1. Mar 25, 2012

### Sidelines

Given a set of wheels connected with a frame and chassis (a typical car), on a surface, how much friction is desirable? Too much friction would slow the car down, where as too little would cause slipping.
A specific example would be four equal wheels with a frame and body, around 1 kg on a wooden surface.

2. Mar 26, 2012

### rcgldr

Rolling resistance slows a car. Friction should not be much of a factor (unless tire surfaces start to act as adhesives). Wiki article:

http://en.wikipedia.org/wiki/Rolling_resistance

3. Mar 26, 2012

### sophiecentaur

With rubber tyres, there is a significant loss due to friction with the road because the tyre is constantly distorting as it comes in contact with the ground and the tread pattern 'scuffs'.
Steel wheels on steel rails are a lot more efficient as the contact area and the distortion are reduced but the low (static) friction limits acceleration (+ and -).

4. Mar 26, 2012

### Khashishi

You are probably overthinking it. Rubber tires should do fine for a 1kg toy car. If it is important to optimize it, you need specific information about the acceleration and top speed of the car.

5. Mar 26, 2012

### sophiecentaur

What, on PF? This is angels on a pinhead land.

6. Mar 26, 2012

### rcgldr

Relatively stiff rubber tires, either very high perssure, or solid rubber tires, reduce rolling resistance, but generally have less grip.

7. Mar 26, 2012

### mender

Actually most of the resistance is internal due to hysteresis of the rubber; not much scuffing going on.

8. Mar 27, 2012

### sophiecentaur

I was thinking in terms of wear as being evidence of scuffing but I guess that is only a small fraction of the contribution to the heating up of the tyres due to internal losses when travelling (a good indicator of energy loss).

9. Mar 27, 2012

### A.T.

sliding friction / aerodynamic friction / tire deformation : BAD (creates resistance)
static friction : GOOD (provides traction)

10. Mar 27, 2012

### Sidelines

How could I optimize static friction in tires and downscale the bad friction forces?
This is more for thought than actual results if the whole 1 kg car seemed pointless.