HPDE Tire Squeal
05-13-2014, 09:45 AM
#1
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HPDE Tire Squeal
I'm currently in the intermediate group (blue) with my 997.2 S using Michelin Pilot Sport tires. No other mods other than racing brake fluid. My track air pressures are 34 front and 38 rear hot. I'm to the point where my tires squeal coming out of most turns.
Does the squealing mean that I've approached the adhesion limit of the tires? Also, does it indicate that I'm wearing the tires more than I really need to? While I want to get around the track as quick as possible, this is my daily driver and I don't want to incur unnecessary wear.
Thanks for your help.
Does the squealing mean that I've approached the adhesion limit of the tires? Also, does it indicate that I'm wearing the tires more than I really need to? While I want to get around the track as quick as possible, this is my daily driver and I don't want to incur unnecessary wear.
Thanks for your help.
05-13-2014, 11:08 AM
#3
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Squealing tires can be caused by many things. The chemical composition of the asphalt binder, sealer or concrete mix; the particular mix of chemicals used in the tire rubber, etc.
The new track surface at VIR, for instance, has introduced squealing on tires where the more polished, lower grip surface did not exhibit that.
The standard Skippy mantra of "a squealing tire is a happy tire" reflects using the auditory faculty that most drivers have to determine and maintain the proper slip angle, or the difference between the the direction the car is going versus the direction of the tire, generally about 7-12 degrees is optimum. That doesn't necessarily mean that you are sliding 7-12 degrees from the car's vector, it means that the tire tread "squirm" is counted in that number.
For the most part, I encourage people to use tire squeal to help gauge the stress (good stress) placed on the tire. The goal being constant volume and pitch throughout the corner.
If you have a situation where the squeal gets louder BUT THE CAR ISN'T TURNING MORE, you have exceeded the capability of the tire to grip, and that can serve as a warning. The CHANGE of squeal volume and pitch is the indicator, not the squeal itself.
Some tires and compounds are more likely to squeal, but that is not an indicator of a less than optimum tire or use of that tire.
Paul Haney's bok gets into that pretty well! Enjoy making racket, secure that you are not generally tearing up anything more than normal wear and tear.
When I get worried is when the squealing turns into a squalling!
The new track surface at VIR, for instance, has introduced squealing on tires where the more polished, lower grip surface did not exhibit that.
The standard Skippy mantra of "a squealing tire is a happy tire" reflects using the auditory faculty that most drivers have to determine and maintain the proper slip angle, or the difference between the the direction the car is going versus the direction of the tire, generally about 7-12 degrees is optimum. That doesn't necessarily mean that you are sliding 7-12 degrees from the car's vector, it means that the tire tread "squirm" is counted in that number.
For the most part, I encourage people to use tire squeal to help gauge the stress (good stress) placed on the tire. The goal being constant volume and pitch throughout the corner.
If you have a situation where the squeal gets louder BUT THE CAR ISN'T TURNING MORE, you have exceeded the capability of the tire to grip, and that can serve as a warning. The CHANGE of squeal volume and pitch is the indicator, not the squeal itself.
Some tires and compounds are more likely to squeal, but that is not an indicator of a less than optimum tire or use of that tire.
Paul Haney's bok gets into that pretty well! Enjoy making racket, secure that you are not generally tearing up anything more than normal wear and tear.
When I get worried is when the squealing turns into a squalling!
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05-13-2014, 11:28 AM
#5
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Very welcome! Enjoy!
05-13-2014, 12:15 PM
#7
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I'd rather hear tire squeal on corner exit than corner entry... 
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maschinetheist (06-06-2023)
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05-13-2014, 01:45 PM
#8
In my experience, squeal is very dependent on the tire. If I were to rank tires I've used in the last 2 years:
1) Sumitomo HTRZIII squeal like crazy and will also chunk if driven hard in the dry. (These are my street/wet track tires)
2) Bridgestone RE-11A are "very chatty", but don't chunk.
3) Nitto NT-05s squeal just a bit, don't chunk. The original Dunlop Star Specs squeal about the same, but are more prone to chunking.
4) Nitto NT-01s don't squeal much at all. They "growl" on the edge of grip, but they will chirp at TWS T8.
After being on the NT-01s, I find the RE-11A squeal distracting as they squeal quite a bit before reaching their grip limit. IMO, the onset of squeal to the loss of grip is highly variable and feeling the grip is more valuable than hearing it.
It also depends on the track. TWS is relatively quiet, except for T8. Harris Hill Road and COTA are noisy on street tires. Going around COTA on RE-11As sounded like the Blues Brothers in my street car.
Then there is the old guideline, tires squealing is bad, whereas tires "singing" is good. I think this is what Peter is referring to with "The goal being constant volume and pitch throughout the corner."
-Mike
1) Sumitomo HTRZIII squeal like crazy and will also chunk if driven hard in the dry. (These are my street/wet track tires)
2) Bridgestone RE-11A are "very chatty", but don't chunk.
3) Nitto NT-05s squeal just a bit, don't chunk. The original Dunlop Star Specs squeal about the same, but are more prone to chunking.
4) Nitto NT-01s don't squeal much at all. They "growl" on the edge of grip, but they will chirp at TWS T8.
After being on the NT-01s, I find the RE-11A squeal distracting as they squeal quite a bit before reaching their grip limit. IMO, the onset of squeal to the loss of grip is highly variable and feeling the grip is more valuable than hearing it.
It also depends on the track. TWS is relatively quiet, except for T8. Harris Hill Road and COTA are noisy on street tires. Going around COTA on RE-11As sounded like the Blues Brothers in my street car.
Then there is the old guideline, tires squealing is bad, whereas tires "singing" is good. I think this is what Peter is referring to with "The goal being constant volume and pitch throughout the corner."
-Mike
05-13-2014, 04:43 PM
#9
2) Bridgestone RE-11A are "very chatty", but don't chunk.
It also depends on the track.
Then there is the old guideline, tires squealing is bad, whereas tires "singing" is good. I think this is what Peter is referring to with "The goal being constant volume and pitch throughout the corner."
-Mike
Tire singing is indeed good--when the pitch drops and is accompanied by rumble and vibration from the front end you know you've overdone it.
Gary
05-13-2014, 07:20 PM
#10
Grip is a function of friction. There is a period of of slipping and a period of sticking. Quickly repeating this constant cycle of slip-stick creates the noise you hear. The frequency of the cycle dictates the type of noise you hear (high pitched squeal, low pitched, squall, whatever). This audible feedback can inform you as to the amount of grip you have at the tire patch.
Most - if not all - tires let you know you are on slip by making noise. At the low end of the slip angle, you may not hear anything (say 1 degree of slip). As you get more slip, you will hear more noise because of the slip-stick effect. For a street tire, max loading may be between 5-12 degrees of slip angle. And there may be considerable noise in that entire range. But the noise at 5 degrees may be different than at 12 - and more importantly, the noise at 5 WILL be different from the noise at 15 degrees of slip angle. The "singing" tire at 5 degrees caused by slip-stick may have a higher frequency noise because there is more stick and less slip. As you get more slip and less stick, the frequency may be lower and kinda raspy. [I hope I got that in the right order, but whatever, you get the idea].
Like other forms of input while driving, you need to train yourself to understand what is normal and what is not. Tire squeal is proper in mid corner (from lateral load), braking on entry and acceleration on exit (longitudinal load). Keep in mind that your tires do have slip angle under longitudinal loading, so they may make noise there, too. [Think of peeling out, you make a slip-stick noise under longitudinal loading].
There may also be physical manifestations that correspond to the different pitched squeal. As you get more slip, the car may feel less stable, BUT - and it's a big but (VR, you like what I did there?) - you may be approaching the correct slip angle for maximum loading. That is, most people think they are at the maximum slip angle when the car starts to make a little noise and feel a little wobbly, but in reality, that is only the leading edge of the proper slip angle. You need to go a little faster yet to maximize the tires, which may result in more noise.
The critical slip angle for R-comps is narrower, and for slicks, narrower still. But even these tires will make noise. It's part of the physics of adhesion between rubber and pavement. Slip angle results in slip-stick, which will make noise.
In short, hearing tire noise is an indication that you driving on slip (vs grip only). That doesn't necessarily mean you are at the limit, or even close to it. It just means you have reached a point where the tires are slipping.
sidenote: because grip levels generally result in a bell shaped curve, there will be noise on both sides of maximum grip. IMO, the closer you stay to the leading edge of the grip, the easier you are on the tires and the longer they will last. The saying "overdriving the car" sometimes means you are on the back side of the grip curve. It may not be any slower (because you are simply at the complementary slip angle), but it will be harder on the tire. An example may be helpful here. Say max grip is at 10 degrees of slip (nice round number). If you are at 8 degrees of slip (2 below max), let's say you have 80% max grip (on the way up the grip chart) and you are under using the tire. Going faster may actually improve lap times. At 12 degrees of slip (2 over max), you may still be at 80% max grip - but you have exceeded maximum slip angle and are on the way DOWN the grip chart. You are chewing your tires up, and going any faster will reduce lap times. Another interesting side note - tires don't just give up. The whole "the tires just lost grip" is a fallacy. There is a slope for grip on the trailing edge of the graph. It never just goes away. Usually, it's a function of the second error... And all of that will make noise as well.
-td
Most - if not all - tires let you know you are on slip by making noise. At the low end of the slip angle, you may not hear anything (say 1 degree of slip). As you get more slip, you will hear more noise because of the slip-stick effect. For a street tire, max loading may be between 5-12 degrees of slip angle. And there may be considerable noise in that entire range. But the noise at 5 degrees may be different than at 12 - and more importantly, the noise at 5 WILL be different from the noise at 15 degrees of slip angle. The "singing" tire at 5 degrees caused by slip-stick may have a higher frequency noise because there is more stick and less slip. As you get more slip and less stick, the frequency may be lower and kinda raspy. [I hope I got that in the right order, but whatever, you get the idea].
Like other forms of input while driving, you need to train yourself to understand what is normal and what is not. Tire squeal is proper in mid corner (from lateral load), braking on entry and acceleration on exit (longitudinal load). Keep in mind that your tires do have slip angle under longitudinal loading, so they may make noise there, too. [Think of peeling out, you make a slip-stick noise under longitudinal loading].
There may also be physical manifestations that correspond to the different pitched squeal. As you get more slip, the car may feel less stable, BUT - and it's a big but (VR, you like what I did there?) - you may be approaching the correct slip angle for maximum loading. That is, most people think they are at the maximum slip angle when the car starts to make a little noise and feel a little wobbly, but in reality, that is only the leading edge of the proper slip angle. You need to go a little faster yet to maximize the tires, which may result in more noise.
The critical slip angle for R-comps is narrower, and for slicks, narrower still. But even these tires will make noise. It's part of the physics of adhesion between rubber and pavement. Slip angle results in slip-stick, which will make noise.
In short, hearing tire noise is an indication that you driving on slip (vs grip only). That doesn't necessarily mean you are at the limit, or even close to it. It just means you have reached a point where the tires are slipping.
sidenote: because grip levels generally result in a bell shaped curve, there will be noise on both sides of maximum grip. IMO, the closer you stay to the leading edge of the grip, the easier you are on the tires and the longer they will last. The saying "overdriving the car" sometimes means you are on the back side of the grip curve. It may not be any slower (because you are simply at the complementary slip angle), but it will be harder on the tire. An example may be helpful here. Say max grip is at 10 degrees of slip (nice round number). If you are at 8 degrees of slip (2 below max), let's say you have 80% max grip (on the way up the grip chart) and you are under using the tire. Going faster may actually improve lap times. At 12 degrees of slip (2 over max), you may still be at 80% max grip - but you have exceeded maximum slip angle and are on the way DOWN the grip chart. You are chewing your tires up, and going any faster will reduce lap times. Another interesting side note - tires don't just give up. The whole "the tires just lost grip" is a fallacy. There is a slope for grip on the trailing edge of the graph. It never just goes away. Usually, it's a function of the second error... And all of that will make noise as well.
-td