# Does Temperature affect the coeffecient of friction?

1. Aug 21, 2004

### JBeans

I have a Question, and I'd appreciate it if someone could give me a definite answer:
Does The temperature of the road surface affect the friction between the tire and road surface?

2. Aug 21, 2004

### Integral

Staff Emeritus
Sure, Is not this why the dragsters spin their tires before a race?

3. Aug 21, 2004

### JBeans

Yes, but that makes the rubber softer, doesn't it. See i'm trying to figure out if the road surface's temperature has anything to do with the friction between it and the tires. So are you saying that anything when is heated, the coeffecient of friction increases?

4. Aug 21, 2004

### Integral

Staff Emeritus
hotter road surface will mean hotter therefore softer tires. Friction requires 2 materials, how do you separate the effects?

5. Aug 21, 2004

### JBeans

Suppose the tires hadnt been on the road as yet, and The temperature of the road gets to 130 degrees (F). Now if the tires were to come into contact now with the road, would the coeffecient of friction be different than that if the road was 50 degrees? I'm just saying before the tires had time to soften.

6. Aug 21, 2004

the teason temp affects friction is a 'microscopic' one. When you increase the temperature of most common solids (ie. rubber, pavement) The solids expand, creationg greater 'gorges' or bough bumps on the surface, causing more friction. If it is cold outside, there microscopic 'gorges' attract, and the surface begins to lose friction.

7. Aug 21, 2004

### JBeans

Thanks that helps.. so one more question, would there be any difference in friction in a temperature change, say from 40 degrees fahrenheit to 140?

8. Aug 22, 2004

### ArmoSkater87

That makes sense, but I thought that hot brake pads have less friction because they are expanded from normal.

9. Aug 22, 2004

### ArmoSkater87

There are a lot of factors involved. For example, at 40 degrees the water vapor in the atmosphere would condense slightly on the pavement, making the road much more slippery and low in friction. Depending on the day, the water might mix with settled dust on the road, making a small layer of "mud" (I dont think you would see it very well), and in this case you would have "hydroplaining" going on, which is very bad because it causes there to be very little friction. When it gets hot to 140, then the pavement would expand and I guess increase in friction, at least thats what would make sense.

10. Aug 22, 2004

### kawikdx225

Hot brake pads have less friction mostly due to a layer of gas that is created when the pads vaporize. This thin layer of gas acts as a lubricator. Most performance disc's have holes or slots cut through them to release the gas and help cool the disk.

11. Aug 22, 2004

### Staff: Mentor

Asphalt also softens with temperature... Though, cement does not.

So, the answer to your initial question is: depends on the material.

And then there's viscous friction...