(028) Coefficient of Friction

In this video I talk about understanding the coefficient of friction of a tire. But don’t panic! It’s not complicated, I promise. After this video you’ll have a much better understand of why traction is always in flux.

Coefficient of Friction – Video Transcript

Hey everybody Matt Covert here again from howtobecomearacecardriver.com and in this video we’re going to talk about coefficient of friction. Oh no, you might be saying, a math term. It’s going to be terrible. Well don’t panic, I promise it’s not that complicated. It’s just kind of a really cool thing that I think you should understand, OK? And we’re going to talk about how coefficient of friction relates to racing tires. So at least it’ll be interesting, alright? So let’s hop on into it.

Coefficient, let me just make this a little easier for you. Coefficient is just a fancy term for a relationship between two things. And in this we’re going to be talking about the relationship between potential force, potential cornering force, and we’re going to be talking about vertical load. We talked about vertical load in another video. So if you haven’t seen that, hop back through the link. I’ll put a link right there so you can go back and watch that one.

So let’s look at how these two terms relate to each other. I’m going to draw a quick little curve here. This thing is really tricky to write on sometimes. I get one more try. Last try. No I’m going to try one more time. Ready? Oh I think I nailed it that time. OK. So let’s talk about the relationship between potential force and vertical load. Alright?

A tire’s potential – let’s just say, this is a theoretical tire. Let’s say this tire is capable of producing eight hundred units of potential force when there are five hundred pounds loaded on that tire. Alright? And we just get – this is just a way to calculate the potential cornering force offa tire. And you can that if you do the math on this you’ll get one point six G forces. And that just means the tire is capable of cornering at one point six Gs, which is a lot.

And if you calculate out this number and you get a number like this you’re probably never going to see this on the track. You’re going to be limited by imperfections on the raceway and suspension limitations and all that kind of stuff. But it really helps to see in a graph type situation that when there’s less vertical load – say you’re cresting a hill and the vehicle suddenly becomes light as you’re cresting over the top of the hill. Your vertical load is going to be less because the vehicle essentially weighs less in that moment. So if you’re here, obviously, your tires have less traction because there is less weight on them. So under ideal situations, up to a point, the more weight you have on a vehicle under good cornering conditions then you’re going to have the most amount of force.

And eventually that force will drop off if you have tires that aren’t rated correctly and they have too much weight on them or your going down into a crazy dip and suddenly you have a little less grip because you’ve exceed the vertical load potential of that tire.

It’s really helpful to see it on a graph. This part is kind of a gee whiz thing. I don’t think this is really necessary to know but I do think, as long as – I do think this is a gee whiz thing if you understand that in the moment, every instant, the amount of grip that is available is always changing based on vertical load. And vertical load changes not only as a whole to the vehicle but in every corner of the vehicle. When you are decelerating the vertical load on the rear tires is much less. And the opposite is true. And when you’re cornering the inside tires have less vertical load. So this is a really complicated thing that gets a little crazy really fast. As long as you understand that this is always in flux and that your grip is always variable, that’s really all that you need to worry about. So I just really wanted to let you know about this coefficient of friction. Not crazy necessary. But you have to understand that everything is changing in every instant.

So I’m going to link to the YouTube subscription right there. And you can click through that and you’ll get notified every time we make another video like this and they’re always really fun. So go ahead and do that and I’ll be back soon with another video from howtobecomearacecardriver.com.

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