Q: “I had a quick question with regards to tire squeal and using it as a gauge for performance driving. Recently, I took part in a driver training program and was reintroduced to the saying “a squealing tire is a happy tire.” My previous belief was that tire squeal occurred in the frictional region after the point where a tire has peaked in the force vs. slip angle curve, not approaching or at the peak. Obviously, every compound, construction, and even batch of tires act differently, however have you found a general trend in your experience? Also, does the same apply for racing slicks? In my limited experience with driving on slicks, I can’t say that I have ever gotten them to the onset of tire squeal before I’ve had to catch the slide.”
A: That’s such an interesting but difficult question to answer! And that’s partly because what you think of as “squeal” might be “tire howl” to me, “screech” to someone else, or….
We both know that a tire makes a certain, specific sound when it’s at the very peak of the traction/slip curve. It may be a squeal, a screech, a howl, a growl, or almost nothing. And you’re right that it’s different for every different tire. Oh, and track surface – it can sound different on concrete versus pavement, and if a sealer is on the surface, it’ll sound different again. But the bottom line is every tire makes some kind of noise when at the limit. It’s the minute gripping and letting go of the tread’s rubber from the track surface that results in the sound. A tire with large tread blocks makes more noise because those blocks kinda snap and then vibrate when they let go of gripping the track surface; a slick tire still does this but without the tread blocks, so the sound is not as noticeable.
As drivers, if we can identify the sound the tires make when they’re approaching the limit, at the limit, and then gone over the limit, we can use that info to home in on driving the limit. Of course, it gets even more complicated by having maybe one or two tires at the limit – making a certain sound – and one or two unloaded enough that they’re not at the limit – and making a different sound. Hey, this is not easy!
The “a squealing tire is a happy tire” is a good phrase to use to help some drivers learn that it’s okay for the tires to make noise. In fact, if the goal is to drive at the limit, they need to understand that that is part of the goal. If the tires are not making a sound, they’re probably not being driven close enough to the limit. Having said that, there are tires that make less sound than others, and if you’re trying to force a set of these “quiet” tires to make noise, you could over-drive them. Again, the goal is to learn what sound every tire makes.
Now, I’ve had many drivers tell me that they can’t hear the tires when driving – that the engine sound and wind noise drowns out the sound of the tires. And that’s accurate, sometimes. But I’ve watched in-car video from a GoPro in some of these drivers’ cars, and I could hear the tires on the video. Once that sound has been pointed out to the drivers, they then can zero in on the sound in the future, and become more consistent at driving at or near the limit.