How can teams resolve tyre issues?

[Jersey Tom]

@ JT

Agree with your observations in general.

But is it fair to assume, that for a given tire (compound/construction etc.)it is
possible to say, if the lack of (momentary)grip is due to insufficient heat or due to too much heat,in a given situation.

Not necessarily. Everything affects everything, it's a question of level of significance.

Entirely possible that 0.5-1.0 deg change in camber or slip angle has a bigger effect on lateral force than a 10 degree change in tread temperature.

In any event, the common theme on this forum is rampant speculation with nothing to back it up. In reality with this tire stuff, you can be designing race tires for 30 years and it's still a crapshoot as to if it's going to do what you want. The more you try to figure it all out, the more --- you are.

[747heavy]

Thanks for your reply Tom.

I don`t want to pick bones with you - far from.
I can see where you are comming from, but would this 0.5-1° camber change
not also affect the temperature of the tire? Chicken and Egg again

As you say everything influences everything.
So where do you start, in a situation where track testing is limited/not possible.

[Jersey Tom]

Sure. Changing camber or slip angle will change instantaneous tire temp. No such thing as purely isolated or controlled lab tire testing. But after you collect enough data, you can start picking out what the tire is most sensitive to. Fact is, there are plenty of times when tread temp just isn't the end-all-be-all, or most important performance modifier.

As for where to go with limited or no track testing.. that IMO is precisely the problem most of these teams have. Really depends on the setup engineer, their philosophy, personal experience, even intuition. Sometimes you nail it. Sometimes you don't.

Ideally you collect as much lab data as possible.

[747heavy]

Thanks for you reply Tom

Is "graining" not a temperature related poblem?
I (think I)know that in a nutshell, it is exiding the shear stress of the compound in question, but was under the impression that this is related to temperature.

Either by the underconstruction of the tire beeing too cold (not enough intermolecular bonding) to hold the outer rubber particles in place (cold graining)or by the tire beeing to
hot (hot graining).

In either case I was under the assumptipon (maybe wrong) that it is related to temperature.
It could be compound related as well, but let´s say, that the compound is not totally wrong for the application in question.

[speedsense]

Thanks for you reply Tom

Is "graining" not a temperature related poblem?
I (think I)know that in a nutshell, it is exiding the shear stress of the compound in question, but was under the impression that this is related to temperature.

I have done some tire tests days for a few tire companies, a couple of times have run into tires with compounds that although the temps, internal pressure/air temp were dead on, the tire still grained. They were experimental compounds being tried for the first time, and the blame was on the compound. Interesting enough was one compound that grained after two "perfect" heat cycles then on the fourth cycle went back to normal with no graining. Wild...

[Jersey Tom]

One way or another, yea, when I think of what initiates graining or tearing.. you're exceeding the abuse & stress limit of the tread rubber. Can things like excessive heat cause that? Sure.

Crappy tire construction design can lead to graining as well.

Or, it can just be from overslipping the tires and steering them past their force peak. Can be from a car out of balance or an overly aggressive driver. Or again, if steering settings are really hosed.

Say for a given corner, your inside and outside tires both peak at about 5 degrees slip angle. If you're running some highly pro- or anti-Ackermann steering, or have a lot of toe one way or another.. you're going to be beating the hell out of one tire and barely working the other.

Bottom line, even if the tread is at a temperature where it has pretty decent strength and mechanical properties.. with enough load you can still shred it. There's an ultimate strength for any material.

[747heavy]

Thanks Tom

[DaveW]

Thanks, JT.... & 747. This has become a very interesting thread.

JT, I can understand everything you said, I think. As an end user, however, I expect a tyre manufacturer to produce a consistent product that is fit for purpose. Hence, I would expect wets to work best at (or around) ambient temperatures. I would not expect front wets to work at 100 degC & rear wets to work at 20 degC. Equally, I would not expect front slicks to work at 20 degC & rear slicks to work at 100 degC. Oh I know they could, but I would expect a designer to produce more or less "matched" sets of tyres, & I'm sure he would (at least try) if he wanted to keep his customers. This, together with a few other properties that are of interest to the designer, but not necessarily to the end user, will allow me to keep my stake in the ground, I think.

[Jersey Tom]

Oh for sure. It's just a very difficult moving target for the tire designer. The cars are always evolving to begin with, as are the setups as teams try more exotic setup options, things like inerters, etc.

Then, as you give them a new tire, they can completely change around their CG, wheelbase, load transfer characteristics, etc.

On top of that, curve balls come your way which just totally --- you. Good example would be NASCAR at Indy in 2008. For a few years.. bring same tire to the race because it works great. Then out of nowhere, on same tire, they don't last more than 10 laps. Likewise Michelin got caught out there in F1, despite being the self-proclaimed technology and development wizards.

Plus compounding for a certain temperature range even, is not necessarily straightward. Like I'm fond of saying, there's no "optimum" temperature for a compound. What makes for the best grip does not necessarily make for the best lap time.

[marcush.]

One way or another, yea, when I think of what initiates graining or tearing.. you're exceeding the abuse & stress limit of the tread rubber. Can things like excessive heat cause that? Sure.

Crappy tire construction design can lead to graining as well.

Or, it can just be from overslipping the tires and steering them past their force peak. Can be from a car out of balance or an overly aggressive driver. Or again, if steering settings are really hosed.

Say for a given corner, your inside and outside tires both peak at about 5 degrees slip angle. If you're running some highly pro- or anti-Ackermann steering, or have a lot of toe one way or another.. you're going to be beating the hell out of one tire and barely working the other.

Bottom line, even if the tread is at a temperature where it has pretty decent strength and mechanical properties.. with enough load you can still shred it. There's an ultimate strength for any material.

exactly my experience.I made this experience with the Lotus Elise and dare I admit :Kumho track day tires.for a sensitive driver the ultra soft compound was the way to go .. but those who were overly aggressive with turnin and did resort to too much steering lock ate up and grained them in no time at all .
but the real funny thing was on some sort of coarse surface at high ambient temps the tyres simply gave no grip ,do what you want it was terminal understeer ,no grip and no temp!, just shedding rubber and deep routing on the tread in no time at all so the tyre was f...d before developing any temperature.put on a different ,harder compound and the grip was a lot better and no signs of graining...

[DaveW]

On to some more interesting things, perhaps, taken one at a time, if I may.

I estimate tyre damping coefficients (as well as stiffness) as a matter of course during a rig test. Tyre damping coefficients are a by-product of stiffness estimation, & are relatively small. There is a measurement issue that I will gloss over for now, but the estimates tend to be consistent & have given rise to some interesting (to me, anyway) observations.

Tyre damping coefficients tend to respond to set-up changes in quite a logical way, & "hot" tyres always seem to have lower damping coefficients than cold tyres.

When I rig test a vehicle fitted with new tyres, tyre damping coefficients usually (on average) decrease slowly during the course of the day. In contrast, the damping coefficients of "scrubbed" tyres tend to remain relatively consistent over time (for similar set-ups, anyway). I have concluded that new tyres are "run in" slowly during the course of a rig test.

For mid-engined, rear drive open wheelers front tyres almost always have higher damping coefficients than rear tyres. This would appear to make some logical sense, because the rear tyres transmit power, whilst the fronts do not. The vehicles usually carry more camber at the front, of course, and increasing camber normally increases tyre damping coefficients. My (perhaps rhetorical) questions are: is this property accidental, or is it a deliberate design feature? If not, & if the increased front damping coefficients are entirely due to camber, is front camber a device that is (consciously or otherwise) used to make the front & rear temperatures more consistent?

[DaveW]

On top of that, curve balls come your way which just totally --- you. Good example would be NASCAR at Indy in 2008. For a few years.. bring same tire to the race because it works great. Then out of nowhere, on same tire, they don't last more than 10 laps. Likewise Michelin got caught out there in F1, despite being the self-proclaimed technology and development wizards.

Firestone had similar problems early in 2005.... The surface had been grooved (diamond cut) after being resurfaced. I believe the surface is easier on tyres now....

[Jersey Tom]

Can't speak for what various tire manufacturers do in their design process, and what they do and don't tune for.

All tires do have a break-in time though (passenger and race), so it doesn't surprise me that the tire properties would change over the course of a test.

With regard to camber, I'd say front camber isn't a heat thing. Just purely bumps up peak lateral grip, independent of temperature. Not going to explain how or why And of course, there are reasons why you can generally get away with more front camber than rear.

[747heavy]

interesting observation DaveW.

Unfortunately, I can´t add anything to answer that question.

I can see the higher damping relates to more heat, for a given frequency/amplitude input
connection.

But, why would more camber lead to a higher CoD in the tire?
Does (in your observations) the vertical stiffness of the tire increase or reduce with
more camber?

[DaveW]

But, why would more camber lead to a higher CoD in the tire?
Does (in your observations) the vertical stiffness of the tire increase or reduce with
more camber?

I guess because the carcass is worked differently... Stiffness reduces with camber, but max stiffness is not usually at zero camber, or what is referred to as zero camber (wheel rims deflect).