tyre temperature - the only thing that matters

[Racer_D]

IMO if you're only looking at pyrometer temperatures for setup, you're leaving a heap of performance on the table.

Some tires at some tracks may want a different temp spread than others. There's no one answer for what is best. That's another reason I say the concept of "optimum" in racing is BS.

Everyone has their own tricks of what to look at, when, and in what light.

Allright - from reading the other posts here (especially about even F1-teams not knowing their tires well enough), I can see this is a very difficult subject.

From what I know, a track is *always* different - the F3-races I went to had touring cars, FFords, etc. all putting down their own rubber, marbles, oil etc. on the track. So the aspect of other cars on track change it during the course of a weekend. At the same time, track temperature may vary a lot as a function of weather. So how on earth is it possible to predict the right tire settings etc.?

For instance, would tire engineers be able to advice: okay, track temperature is 35 degrees now, drop half a degree in camber if you want more 'stick'?

I am sure engineers take tire temperatures (from either DAQ or pyrometers) just to have the info, but I really wonder how they interpret it, what they do with it. If people have their own tricks to look at things, when to look at things, I wonder how 'exact' this tire science is right now.

[Jersey Tom]

I wonder how 'exact' this tire science is right now.

It varies substantially from tire manufacturer to manufacturer, and from series to series.

It's a lot better than it used to be, but it's impossible to control and account for everything. Impossible. I don't care if it's F1 or not. They don't know everything about the tires.

There is plenty that is open to subjective interpretation.

Some people lose sight of that when it comes to vehicle simulation, etc. Sim is only as good as the tire data (and everything else).

[Racer_D]

I wonder how 'exact' this tire science is right now.

It varies substantially from tire manufacturer to manufacturer, and from series to series.

It's a lot better than it used to be, but it's impossible to control and account for everything. Impossible. I don't care if it's F1 or not. They don't know everything about the tires.

There is plenty that is open to subjective interpretation.

Some people lose sight of that when it comes to vehicle simulation, etc. Sim is only as good as the tire data (and everything else).

Clear So basically, the most important part of the car to tune remains - as always - the nut holding the steering wheel...

[marcush.]

Coming back on JTs words ,more stick is not always the fastest...
To my knowledge it is not really the quickest way around the track looking to build up maximimum Gs ,in fact the side forces(Stick)do consume lots of power you beter used to accelerate the beast.So the longer the car is run flat(without sideforce)the more stick you got to move forward faster(same with braking).

As for the tyre ,you have to think of them as full buckets when mounting them on the car .If you try things with them too early ,you will waste the first 2 quarts just because of trying things which are yet impossible. the guy in search for the limit by overdriving not only does loose a lot of time thru mistakes he does also by throw away potntial of the tyre which is not recoverable.So in addition the tyre will not last as long.

I always preferred needle type pyrometer and did not really care about absolute temps,as long as I got the desired temp spread .But really you take each tyre after a Qualy run and long runs ,take the time to remove the pickup and take a really thorough look on how the tread/surface has developed.You build up experience what the tyre likes and what it doesn´t and of course you put that into context with what the stopwatch ,the datalog and the driver is telling you after the run(You have to ask ask ask ,don´t think for a second hes gonna tell you all he has experienced out htere before you have thumped him excessively....The temp spread is something you ask the manufacturer at the beginning of your using of this particular tyre on the car and you go on from there and build up your data base with good documentation and good equipment for measurement.

I remember a Pirelli guy in a Onemake Series who always, when asked gave completely useless guidelines about pressure and best proceedure of treating the tyre.
When trying to countercheck my Pressure gauge with them ,they had a 5€ thing to check pressures,so don´t assume you can rely on information given really...

[Shrek]

I was watching last years Turkey race and the commentators said that the hard tyres were faster in the heat, and i haven't seen anything about it anywhere, so the question is, is this true?

[mx_tifoso]

Shrek, I think that by reading this thread you will get the answer to your question.

[Shrek]

oh, thanks

[Belatti]

The next six months is likely to be interesting, both on & off track.

Any new info that you may have about the "magic ratio" from Bridgestones reduced width front tyres Dave?

[speedsense]

IMO if you're only looking at pyrometer temperatures for setup, you're leaving a heap of performance on the table.

Some tires at some tracks may want a different temp spread than others. There's no one answer for what is best. That's another reason I say the concept of "optimum" in racing is BS.

Everyone has their own tricks of what to look at, when, and in what light.

Allright - from reading the other posts here (especially about even F1-teams not knowing their tires well enough), I can see this is a very difficult subject.

From what I know, a track is *always* different - the F3-races I went to had touring cars, FFords, etc. all putting down their own rubber, marbles, oil etc. on the track. So the aspect of other cars on track change it during the course of a weekend. At the same time, track temperature may vary a lot as a function of weather. So how on earth is it possible to predict the right tire settings etc.?

For instance, would tire engineers be able to advice: okay, track temperature is 35 degrees now, drop half a degree in camber if you want more 'stick'?

I am sure engineers take tire temperatures (from either DAQ or pyrometers) just to have the info, but I really wonder how they interpret it, what they do with it. If people have their own tricks to look at things, when to look at things, I wonder how 'exact' this tire science is right now.

The "problem" with tire engineers hired by tire companies is whether they tow the company policy or not. A tire engineer has to adhere to company policies in the information they share, mostly due to legal aspects and protecting company knowledge. They know far more than they are willing to share. Especially when involved with a spec tire.
Personally I have found out more about a tire type,temp range effects (over and under, as well as target) by having conversations with the tire compound engineer. (Most of them are happy to talk, as nobody ever seeks them out) They seem more willing to share information, at least on the chemical side and at times will share the construction end. For instance whether it is better to scrub or run from new or what the "real" top pressure level is before explosion (was way beyond what the tire engineer said)

The constant change in the chemical properties throughout the tires life and use, have a direct effect on temp ranges and of course the grip level. Temp distribution, levels and cycling are the dominant factors in this chemical change.

One of the most important aspect of tire temp, is the core heat and the retention of it. Without ample (under worked) or too extreme core heat (overworked tire), the outside, surface temp may "appear" on an IR logging graph or a pyro reading as being normal on a short run, yet the core is far off. Internally measuring the air temp through a doubled air pressure/air temp sensor reading can help keep the ranges "in check" and lead to a better understanding of optimum levels of grip.
The variables of making tires, is very similar to making cake. A couple degrees of room temperature or humidity can change the exact same tire procedure and create a tire that is different from the rest. Shipping a tire on a hot truck or train, can change it further (more curing). Leaving your tires out in the sun and the UV light will change it further.
To make this conversation,even less controllable, a bias ply vs a radial has properties in vertical and lateral weight loadings and grip levels that almost opposite of each other. One type of tire can absorb a quick vertical weight transfer (bias), the other will lose grip (momentarily) with the quickness of the accelerations (radial).
From an engineering stand point, one would approach the setup, say... with spring rates for example, that would differ according to the tire type.

The science of tires, is a less exact in measurement and in maximizing grip, than we would like it to be. Especially coming up with an exact measurement of the optimum contact patch and the exact path it follows. Kinda like trying to measure a rubber band that can bend, flex, contort, twist, expand, compress and warp in one small spot.
The person that can invent a selection of sensors that could measure this to an exact science, will become very rich indeed. IMHO

[Jersey Tom]

The "problem" with tire engineers hired by tire companies is whether they tow the company policy or not. A tire engineer has to adhere to company policies in the information they share, mostly due to legal aspects and protecting company knowledge. They know far more than they are willing to share. Especially when involved with a spec tire.

Do you mean engineers.. or technicians?

[speedsense]

The "problem" with tire engineers hired by tire companies is whether they tow the company policy or not. A tire engineer has to adhere to company policies in the information they share, mostly due to legal aspects and protecting company knowledge. They know far more than they are willing to share. Especially when involved with a spec tire.

Do you mean engineers.. or technicians?

The "customer service" engineers or I guess in some cases they are technicians as well...depends on the company, at least most of the companies I've dealt with.

[speedsense]

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[speedsense]

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[speedsense]

I estimate tyre stiffness as a matter of course when rig testing a vehicle. Many caveats - wheels are not rotating, tyres are usually (but not always) cold, they are loaded vertically but not laterally, etc. Customers choose baseline pressures.

Typically, tyre stiffness varies by around 8 N/mm/psi &, perhaps, 10 N/mm/degree of camber (apologies for the mixed units).

Across a range of open wheeled, mid engined aero vehicles (IRL through to F3) the ratio of rear/front tyre stiffness is usually between 1.1 and 1.3. The ratio for F1 tyres between 1994 & 2004 averaged 1.17. None prior to 2005 was less then unity.

F1 grooved tyres during 2007/2008 averaged 0.92, & the 2009 slicks appear to be (one sample only) slightly worse at 0.91.

Aero centre of pressure should be close to the centre of gravity for consistent balance, & both should be at around 47.6 % wheelbase behind the front wheels for zero sideslip/ny with the 2009 F1 slicks. That would have an unacceptable impact on traction for a rear drive vehicle, so the (not very comfortable) compromise is, perhaps, a centre of gravity close to the geometric centre. Not easy to achieve with a mid-engined layout (hence heavy front wing assemblies & no KERS), & the result must still be an evil drive (sideslip AND probably a lateral balance shift with airspeed). A possible explanation, perhaps, for some of the inconsistencies & tribulations observed over the last three years.

Would you relate the findings (bolded) as an association to a tire "spring" frequency balance (front to rear), as we would relate the spring frequency balance of the front and rear springs in a car?
As the tire is essentially an uncontrolled spring and your ratio findings seem to point to such an area of interest....IMHO

[DaveW]

Would you relate the findings (bolded) as an association to a tire "spring" frequency balance (front to rear), as we would relate the spring frequency balance of the front and rear springs in a car?
As the tire is essentially an uncontrolled spring and your ratio findings seem to point to such an area of interest....IMHO

Good question, & one I can't answer simply. However, it is worth noting that a spring doesn't have a "frequency", as I'm sure you know. The comment is worth making, however, because your statement implies, perhaps, that a quarter car model can be used to set springs & dampers. The technique certainly is used in the road vehicle world to decide on spring selections (spring_stiffness / corner_spring_mass). The concept is flawed, however, because tyres do affect vehicle natural frequencies & the two axles of a vehicle are not isolated from one another, but are connected by the sprung mass.

In other words, the mechanical suspension set-up problem is not one of optimizing two second order systems (or even two fourth order systems if tyres are included), it is one of optimizing a single eighth order system, with (actually) many non-linear parameters. An asymmetrical vehicle (e.g. NASCAR) raises the complexity yet again. A satisfactory solution to the problem (in general) can only be obtained using a full vehicle model or a hardware-in-the-loop test using multi-post rig.

To illustrate, start with a completely symmetrical vehicle (c.g. at 50%, same springs, dampers & tyres at each axle). If the front springs are required to be increased, then a quarter car model would suggest that the front dampers should also be increased. Usually, however, increasing the front springs will imply that the rear axle will dissipate more of any disturbance energy, so the correct change would be to increase the rear dampers. When the ratio of tyre/spring stiffness is small, the spring change would probably require some combination of increased rear damper settings, reduced front damper settings, reduced rear springs, & increased rear tyre stiffness. Parameters very definitely become highly "coupled".

Why is tyre stiffness important? Because they have to support the suspension & transmit suspension loads to the road surface. It follows that tyres (or, more accurately, their vertical stiffnesses) are an integral part of the suspension of a vehicle. It turns out that having a stiffness split that corresponds with the sprung mass c.g. position is a good starting point. Tyres that don't have the "correct" stiffness split can be accommodated by making suspension adjustments; if other (usually driver or aero) requirements mean that this in impractical, then the alternative is to move the sprung mass c.g. position, which is what F1 teams have been doing for the last few years. There is a compromise to be made in that case, however. Moving the c.g. (& centre of pressure) forward improves vehicle "mechanical" control & tends to increase front tyre temperatures, but it will reduce traction...

Tyre lateral stiffness split is also important, principally for the driver. A vehicle that sideslips under lateral loads affects a driver's ability to operate close to the "lateral limit" of the vehicle (& its tyres).

As I said at the start, your question is difficult to answer. I hope the above will help a little.