Is one tyre model enough?

Everyone in simracing these days, and every day for the last fifteen years, seem to be on about tyre models, a new one here, an old one there, another one that no one likes and several million opinions on all of them.  It seems in this day and age a sim is judged almost entirely on its tyre model.

Before we get too deep on this one, I would like to apologise to my American readers for spelling tyre with a Y. Over here in old blighty we spell it this way, and not with an I, as is popular in the United States.  It may seem an odd apology, I know, but some of my American friends (Bob) have had a real thing about it for a while, so I am sorry if you tire of me spelling it “tyre”.  Just remember I for fatigue, Y for round rubber thing.

In recent times there have been some reasonably notable advances in racing sims when it comes to tyre modelling, to the extent that our sims are becoming more and more realistic to drive with every major release.  Every new tyre model gets the Spanish inquisition on every forum from both the completely clueless and the vastly knowledgeable alike, everyone has something to add because if you’ve driven a car or kart or anything in real life it almost definitely had tyres (Caterpillar excavator and tank drivers excluded).  We all feel we know how a tyre feels and thus how it should feel in a sim.  If it doesn’t feel like what we know or what we have experience of, it is wrong. If it does, then it is spot on and a great sim.  But hang on, is this how it works?

With the right tyres I might have been on that white line!

In my experience, tyres can be very divergent beasts. A tyre from one manufacturer can feel very different to a tyre from another, and even two tyres that are the same make and model can be different, in subtle ways.  When out on track doing practice laps one can get very “Zen” about the tyres under your vehicle, and subtle changes in track temperature can merrily change the way they behave from one corner to the next.  It’s not unusual that, say, the front tyres behave with a wonderful turn in bite on a specific corner on one lap and it inspires a great confidence as you come around the next time, knowing the sidewalls will hold up, and that the grip is there, you push into the corner faster than before, and it holds on, it feels glorious as you exit at a speed higher than ever before.

The next lap you come around, and note the track is darker, a cloud has come over the circuit blocking the blazing sun from warming the tarmac, you twist the steering wheel with the same gusto, expecting that bite, and it doesn’t come, the fronts slip instantly, giving in to the demands of the driver and scrub speed away. You take remedial action and scrabble through the corner, wide of the apex, and note it in your mental rolodex for future laps.

This variance is implicit in nearly every circumstance. You can run the same car on the same tyres over two days with a slight variance in humidity, temperature and tyre wear, and they can feel very different to drive, you make minor adjustments to driving style and lap times can be similar. In real life, the interrelation between a driver and their current set of tyres is a symbiosis, both change constantly and adapt to one another’s input and response.

Then, if you switch to a different tyre manufacturer, the whole vehicle’s performance can change. This is hardly surprising, when variances in tyre pressures can change so much in a car’s feel.  When I switched my Lotus Exige from Yokohama to Toyo rubber there was a sea change in the way the car felt. The Toyo’s had notably less strength in their sidewall construction, this caused instability at the rear as the tyre jounced over bumps, the front end also failed to respond to entry inputs as cleanly as it had on the Yokohamas.

But, once this entry behaviour was over with, the Toyos delivered more mid-corner grip, and were able to maintain heavier lateral loading in faster turns.  The Yokohamas were considerably more tolerant of combined longitudinal and lateral loads, so you could carry the brakes deeper into the turn without overwhelming the front tyres and understeering, as well as being able to get back on the throttle earlier in the turn, but, on the Toyo’s, provided you braked in a straight-line, were smooth and turned in precisely, they were able to carry more speed through the corner.  One car, two different tyres, two very different styles and virtually the same lap times.

So, given that the driving experience was notably different on two different sets of tyres, how can I drive a simulated Lotus Exige and pass a judgement on what is “right” or not?  How can anyone be so clear and precise when they judge a racing sim and decry its tyre model to be “wrong”, when in real life one tyre can feel much more “right” than another?

Developers of racing sims are often party to direct data from tyre manufacturers, and this can help with granting a given car an accurate feel, often along with help from real world drivers. But what about sims that are open to mods? What about tyre manufacturers that might want to protect their products by keeping certain data close to their chests?  It’s a tough call, and it seems more and more the case that sim developers are creating their own “brand” of tyre, based on creating something that feels good to drive in most circumstances on the given car it is applied to.

Obviously, a tyre that runs on a NASCAR and one that runs on a Formula one car have to be markedly different, so it has long been not quite enough for a sim to have “a tyre model” when it is essentially modelling lots of different tyre types. But who is defining the character of a given tyre?  And is it always defined tightly by real world feedback, or is an element of test driver preference coming into it?  One tyre can behave in a certain way that notably benefits one style of driving, if you drive that way, you will like the tyres, if you drive in a different way, you won’t.

Could this explain why there has never been, and may never be a unanimous agreement in the simracing world as to which tyre model is best?  If one tyre that works best under high lateral loads, but is very sensitive to combined loads, is bolted onto a GT2 car, is it not quite feasible that one driver could find it perfectly to their taste and yet another find it nigh on undrivable?

As sims become closer and closer to reality it is a truism that they also get closer and closer to one another in feel; it is considerably easier to jump from one sim to another and maintain good pace now than it was five years ago.  The closer they grow in feel to real life also brings parity to the differences in driving style, and driver preference. So, with this being a competitive marketplace, how can developers keep everyone happy?

With more choice, simply.  If a driver, when taking out their virtual motor car, can choose between virtual Bridgestones, or virtual Pirelli’s (Or whatever they want to call them) then perhaps a balance can be found where two tyres can bring up similar lap times if driven the right way, and thus multiple driving styles can be covered.  Hey presto, everyone likes the sim and the level of forum tyre ranting reduces by 90%.


About shrapnel1977

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3 Responses to Is one tyre model enough?

  1. Aristotelis says:

    Pretty much agree with the whole post, and I’m mostly sure the gran majority of the simracing crowd will agree too, asking – or rather demanding – more choice on tires ecc.

    Unfortunately that’s only in theory. In reality, when we created tons of different tyre types for P&Gv2.1 (and even more for the upcoming v3) the majority of simracers never ever spent 5 minutes to read the manual and understand what were the characteristics of each one. And we’re talking for hardcore sim enthusiasts here.

    But yeah, fortunately they will always be sim junkies like us, that will keep doing things like that 🙂

    • shrapnel1977 says:

      I thought it was one of the best things about P&G tbh. There should be more of that sort of thing, more depth to the simulation can only be a good thing.

  2. Thanks for the nice article. I don’t think it’s intentional, but you seem to mix up tire model and tire implementation. As you describe it you would create one model for every tire you simulate, this may be true if you only look at sims that each feature only one series. However with racinsims like rFactor you have the tire model not as one specific implementation, but as an interface of settings you – as a modder – have to implement yourself. There is one tire model in the game that is configured – thereby implemented – and that does all the calculations that should work for any series. So in your article you compare tire model implementations, while the technical background of the tire model is not debatted.

    I hear this discussion often and especially with rf2 you are confronted with a tire model that is vastly extended with options compared to rf1. You need good sources and knowledge how to transform it into the implementation. With little affordable ways to get on the real data (buying is >6000€), this will surely become a larger topic.

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