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.
A precise answer to a variable question (situation)… thanks, as always, Ross!
As a motorsports writer and publisher I found that some information is easy to get from some manufacturers, but when it comes to tires, well…: “it’s a Black Art, we do not reveal that information, I’ll get back to you…” But sometimes I would find an engineer who understood that I was asking questions as a writer rather than a racer.
OH, yes, tire noise. From what I had gathered from one of the conversations I had with a Goodyear tire engineer at (then)Sears Point Raceway, now Sonoma Raceway, it’s all about the Cornering Force vs Slip Angle curve.
When a tire is at the peak of the curve it is happy, it is doing its job. It is generating some slip angle and grip. BTW, the Slip angle has nothing to do with the car being sideways. The noise the tire is making bears witness to how it feels. It’s like it is singing to you. Anywhere past the peak of the Cornering Force vs Slip Angle Curve the tire is no longer happy and its tune changes. At an extreme, street tires will growl when taken past their limit. This is typical with the front tires of a front-wheel-drive car.
I have suggested drivers use their Garmin Catalyst to recognize good and bad tire noise as compared to faster and slower times around a particular turn.
Jean Genibrel
AppliedSpeed.com
I appreciate your thoughtful and insightful response to one of the most pondered aspects of tires, and the art of racing. I have been attempting to define the sound a tire makes at its optimum performance. It has been elusive, at best.
As I try to better understand the topic I consider that moving tires are always making noise at some level and some frequency based upon speed, tread pattern, tire compound, temperature, and the endless variety of road makeup/conditions….plus the stress the tire is experiencing at any given moment. That stress changes as the carloads and unloads because of braking/accelerating or over rises and falls. All this while it could also be cornering to some degree. Once again, the tire design, rubber compound, pressure and temperature have some optimum conditions where it will generate the maximum force to react to those inputs and any one of those conditions can and will change second by second. What is the sound it makes at that ideal condition?
I do know that tire designs vary depending on intended purpose so that one tire, like a street tire, will likely have a more gradual rise to maximum traction so-as-to-be more forgiving and provide more feedback to the driver. Racing tires have very different and varied targets for their designs and engineers study those characteristics to best apply them to racing conditions. Holy smoke! What a complicated and interesting topic to try and get smarter about and hopefully, someday, get good at.
When I consider Sim racing some of these conditions are controlled to a degree. For instance, we do not need to worry about tire age, sizes, optional tread patterns or the myriad of competing tire companies/compounds etc. We get the limited compounds available for each car. Good! Sim track surfaces are more controlled than real life so many times we don’t have to worry about road patches, change in tarmac/concrete etc., we only have to deal with the engineer/designers’/programmers’ models. Granted we are seeing better modeling of track terrain, changing traction characteristics, temperature modeling etc. We need to keep studying and learning. Yikes!
So, I retreat from my exercise to understand what sound (screech, scrub, squeal, rumble, whatever) a tire makes at the peak of traction, and I really get why “IT DEPENDS.” Granted, tire sound is a significant vocabulary we need to try and interpret and understand, just like the thousands of other inputs we are attempting to process in pursuit of the fastest times. This is only one (truly important) element of the informed Art of Driving!