Tyre models - versions and what they mean

Discussion in 'Car Information and physics updates' started by Alex Hodgkinson, Dec 16, 2020.

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  1. Alex Hodgkinson

    Alex Hodgkinson Sector3 Developer

    Jun 5, 2017
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    This thread refers to the the tyre versions displayed here in column G.

    No version/empty cell

    Pre-2017 development. Not really sure about the method here and didn't really dig too deeply in to it, so there's not much to say.

    V1 (2017)

    This was my first attempt at making a tyre generator tool for RaceRoom in excel. It's actually built on something I started for rFactor in around 2009, adapted to suit RaceRoom. It's quite basic truth be told as all tyres use the same core characteristics. Slip angles, slip reaction and grip curves are all exactly the same across the different tyre sizes. Different tyre weights are accounted for, and affect unsprung weight as well as the spinning inertia of each corner.

    V2 (2018)

    Built on the work above, this version takes into account a few more criteria in order to generate each tyre's character. The slip curves are updated to match some findings, which actually give a narrower operating window than previously. Cars are more responsive, but grip drops off more quickly.


    With this update tyre construction becomes more of a factor. How much the optimum slip angle changes as the tyre loads up is now calculated per tyre size and according to tyre construction. In addition, each tyre's vertical stiffness (how much it compresses as downforce builds, for example) is particular to each individual tyre width, sidewall height, construction and weight.
    We added flat spots at this point. Each tyre is divided into radial segments which can wear down at different rates depending on how they're treated during the tyre's life.
    Also started to implement different compounds with differing characteristics other than the obvious grip and wear rates. Harder tread compounds tend to have softer construction as they operate under less load. If soft compounds had the same construction as hard compounds, they would feel mushy as they're under more load.
    Different compounds also have differing grip drop off at different wear levels, an example of which is below:

    Screenshot 2020-12-16 192429.jpg


    Moving from V3 to V4 was the biggest step of all. Until now, optimum camber was a set value - tyre grip peaked at whatever that value was set at and dropped of either side. With V4.0, that code was re-written. Now the optimum camber changes according to how much load is on the tyre. The greater the load, the higher the optimal camber. So we can now take two different cars, one heavy and one light, fit the same sized tyres to them and simply due to the different loadings the camber requirements will be different. Nice stuff!
    Slip angles are calculated per tyre, and are related to tread width, aspect ratio, sidewall height and construction. Now if we change tyre sizes on a car, the characterises change slightly.
    The final big thing was a creation of a new slip curve generator. This now adjusts slip/grip curves slightly per tyre to account for different characteristics. As an example, for the same construction, a taller sidewall will tend to flex a bit more initially but then be more progressive as load increases. Lower profile tyres will flex less initially, so slip angles are lower, but then drop off is a bit steeper afterwards.


    In other words, now we're getting really close to just punching in a tyre size to our calculator and getting something completely bespoke out.


    This is really just a small tweak on the V4.0, as the .1 suggests. I had a re-think on how to calculate slip ratios and applied it. Gives the calculator tool a wider operating range which will allow a larger range of tyres to be generated without having to 'fudge' at any point.
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    Last edited: Dec 16, 2020
  2. Alex Hodgkinson

    Alex Hodgkinson Sector3 Developer

    Jun 5, 2017
    +1,829 / 0 / -0
    You can expect the following car classes to be updated with v4.1 tyres with the incoming patch;

    GT2 (new)
    Audi TT Cup
    Audi TT VLN
    Touring Classics
    DTM 1992
    Group 2
    Group 4
    Group 5
    2003 DTM Mercedes
    2005 DTM Mercedes
    Formula RaceRoom 1990
    Formula RaceRoom Junior
    Hillclimb Icons
    Volkswagen ID.R
    NSU TT
    Porsche GT3 Cup Sprint
    Porsche GT3 Cup Endurance
    Porsche 964 Cup
    WTCC 2014/15/16/17
    Cupra E-Racer
    DTM 2020
    Porsche Cayman Cup
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    Last edited: Dec 17, 2020
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