In this video I introduce a topic that is widely ignored: tread squirm. But that’s OK. I tell you all about it, why it should be avoided, and how we can negate it’s occurrence to maximize our tire’s potential.
Tread Squirm – Video Transcript
Hey everybody Matt Covert here again from howtobecomearacecardriver.com and I’m back here with another video. Another free video. And OK, we just need to take a second to talk about something that is vastly, vastly ignored in the tire management portion of racecar driving. And that is the topic of tread squirm. I like saying that – tread squirm. Let’s hop right on in. I’m going to explain exactly what this is and what we can do about it. Alright?
So I’m just going to draw the bottom of a tire. We’ll just say that’s like the – looking at it from the side. So this is where is connect the ground, across. Alright? Now I’m going to make a crude drawing – let me start – let me change that, there we go. Alright. So I’m going to draw some theoretical tread blocks. Let’s say that these are the sections of raised rubber on the tread section of a tire. Alright. That looks more like buck teeth than it does actual tire treads. But that’s OK you’ll get the idea, alright?
So tread squirm is when we load a vertical force onto a tire, alright? And this is what tread blocks look like when they’re either going in a straight line or when they’re static. Alright? Let me just do this, OK. So let’s add a force this way, OK? Tread squirm is under a lateral force and it causes tread blocks to kind of bend over like this. OK? If that makes any sense at all. Yeah those ones look a little better. Yeah, there we go.
So you get the general idea, OK? Your tread blocks have kind of bent over to the side because of a force that is acting on them. And this is no good and there are a couple reasons why, OK? Number one is effects the contact patch. Whoops. And I know we’ve talked several times about contact patch. And that’s really the goal of racecar suspension and tire choice, is maximizing this contact patch. You want the bottom of your tire to be completely touching the ground all the time. Alright?
And when you get this kind of – this is very exaggerated and of course this is just an example – but when you get into a situation like this the contact patch gets messed up. It kind of lifts up one side. You can kind of see the angle there. The side of the tread and you’re kind of using this section of it and it’s just not optimal, alright?
And let me just move on to the next one real quick. This is kind of a stability issue. Alright? And I think as a general rule I’m going to go ahead and say if anything is just kind of flopping around in your racecar it needs to be fixed. And this is definitely not a good situation to be in, like we said earlier.
Here’s the big one. OK? A heat factor. We’ve talked a lot about keeping tires within their optimal temperature ranges, OK? All of this bending rubber – you know what happens when you bend something a ton of times OK? It creates heat because all the molecules inside are rubbing against each other and that’s a problem when you’re trying to keep your tires inside an optimal temperature range. Excessive tread squirm is going to overheat your tires. OK? And this is no good because this will cause your – not only – this will cause your tires not only to be outside of their temperature range but it will also heat cycle your tires out.
OK? So you’re going to wear out your tires. The hotter your tires are the easier they deteriorate and the more useless they become. Every time you put a heat cycle through a tire it becomes a little less effective. It effectively starts hardening up the tire. Alright? And that’s no good.
So let’s talk about what we can do about this. I know a lot of autocross tires – we’ll make another example. Let me back up a sentence I’m going to change that, OK? The easiest way to change tread block squirm – OK so like I said you have a block that is bent over like that – the easiest way to fix this is to have shorter tread blocks. OK? When your tread blocks are shorter or shallower there’s just less mechanical advantage for them to bend over under a lateral force.
OK so a shorter block is going to alleviate a lot of the heat problems that you have. It’ll be more stable, your contact patch will be more normal and this is the best way to fix it. OK? A lot of autocross tires are manufactured with short tread blocks. Some of them – I know the Direzzas are nine thirty seconds tread, most of them. And some of seven thirty seconds. They’re already pretty short, OK? But there is a lost art that can make this even better. And a lot of autocross guys don’t even do it. And it’s called tread shaving.
So what you’re doing is – if you have a set of tires that comes out of the factory with tall tread blocks, OK? You’re actually shaving them down so they come out like this, OK? And I know it’s counter intuitive but if you shave a tire’s treads you’re actually extending it’s life. Even though you’re taking off a lot of rubber off the tires you can actually extend that tire’s life because it will heat up less, deteriorate less, and the cooler you keep a tire the less intense the heat cycles are and that’s definitely a good thing, OK?
And especially in autocross when you’re using – and this applies mostly to like the Street categories or whatever – you can’t go anything softer than a two hundred UTQC tread rating. Which is just a rating of how soft a tire is. OK? So when you’re using a tire compound of this nature your tires are probably going to heat cycle out before they wear out. So even though you’re taking all this extra rubber off it’s not going to wear out your tires prematurely. It will actually help extend their life through the season, which is great.
And the other thing that people don’t think about, about shaving tires is you’re saving a ton of weight. Let’s say you take almost a quarter inch of off your tread blocks all the way around the tire and then you do it four times. One for each tire. You’re going to save several pounds of weight. And that is all kinds of rotating mass and inertia and outboard weight and polar moment and all that weird stuff OK?
So I think that pretty much wraps up tread block squirm. It can be fixed through shaving like I said. And something that most people are not aware of and they should be and that’s all there is to it, alright?
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