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IRacing Tire Model History

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Overview[]

(Based on this update):

  • NTM v7 (from March 2019): new model for carcass motion (after V6), new tread rubber model (after V5) with better estimation of the shear relaxation modulus G(T, t);
  • NTM v6 (from June 2015): new carcass code, still using V5 tread rubber model
  • NTM v5 (from early 2013): V5 rubber model
  • NTM v1-4 (from June 2011): ?, debut dates?


Major changes:

  • April 2013 (NTMv5?): improved the modeling of tire carcass yaw motion relative to the rim. Increased tire slices for temperature computation from 3 (OTM) to 7-20 depending on tire width.
  • January 2013 (NTMv4?): improvements to the modeling of the tire carcass motion.
  • January 2012 (NTMv3?): improvements to tire damping forces, both vertical and lateral, and to the carcass torsional stiffnesses
  • October 2011 (NTMv2?): improvements to tire carcass stiffnesses and motion, modeling of tread compounds
  • July/August 2011 (NTMv1?): "tires are a bit more forgiving than in the preview release".

2020[]

2019[]

  • June 2019, Season 3 Build
    • V7 tire adjustments, including:
      • Tire compound and carcass curvature have been adjusted.
      • Oversteer/Understeer balance and over-the-limit behavior have been improved.
      • Minimum tire pressure has been set to 25 psi for all four tires.
      • All four tires now also have tire warmers to bring them up to 130F.
      • The primary change to the RT2000 is the improved aerodynamic forces, particularly side force and yaw moment. The rubber conditioning, which is the softening effect of simply working (stretching) the rubber repeatedly, is not quite correct yet, but the car is in a much better place than any previous build, so we wanted to share our current improvements. The tire pressure minimum is present because the handling is more predictable and better for new drivers with the higher pressures; without a minimum, nobody would run higher pressures. The tire warmers have been added to help offset some of the still unfinished conditioning effect.
    • New car (still on V6 tires): MENCS Ford Mustang.
  • March 2019, Season 2 Build
    • Tire Model V7 debut:
      • The new version 7 (V7) tire model has been introduced on the Skip Barber Formula 2000. This model has significant improvements to both rubber compound modeling and tire carcass dynamics modeling, and the feedback has been very positive for the few vehicles we have been testing it on. Only the RT2000 has undergone enough testing to release with this build, but we hope to put this tire model on every vehicle soon.
      • The allowable cold pressure range has been opened up to allow pressures that are, frankly, too low (14 psi) all the way up to too high (45 psi), but we feel it is important to allow you to push the boundaries so we can better find out if the tire is behaving reasonably. Running at too low a pressure can give you a very evil car. High speed corners and low tire pressures do not work well together. Which tire pressure is optimal will vary from track to track, and sometimes you may find compromising one part of a track is worth extra speed in other parts of that track. Also remember that average lap time is often more important than best lap time, so don’t forget to average in extra time caused by spins! In other words, if you’re having trouble racing on low pressures, try raising them.
    • New car (still on V6 tires): BMW M8 GTE.

2018[]

  • June 2018, Season 3: new cars Porsche 911 RSR and Subaru WRX STI.

2017[]

  • September 2017 (Season 4 Build), new cars: Dirt UMP Modified, Ferrari 488 GT3.
  • June 2017 (Season 3 build)
    • Tire updates: "Tires – The temperature effects from locking up a wheel have been improved. Now the temperature is kept separately for the contact patch and the entire tire surface, so lockup heats up the contact area much faster which reduces grip. Also, the temperature drops rapidly upon releasing the brake and allowing wheel rotation. This keeps the tire from becoming too “greasy” after a lockup. Both effects deal much more realistically with tire hot spots on the surface of the tire."
    • On Nascar cars: "Tuned tire compound for increased tire wear.", "Tire and wheel convection coefficients increased."
    • New cars: Ferrari 488 GTE, Ford GT – 2017.
  • January 26, 2017 (2017 Season 1 Patch 2): Porsche 911 GT3 Cup Car (991) released. iRacing staff said somewhere that they developed a new tyre model (V6.5?) out of things they learned about dirt and used it in the 991.

2016[]

  • December 2016 (2017 Season 1 Build):
    • "Telemetry – New telemetry variables, “TireLF_RumblePitch”, “TireLR_RumblePitch”, “TireRF_RumblePitch”, and “TireRR_RumblePitch” are now available. These represent the pitch in Hz produced by the tire going over a rumble strip, or 0 if the tire is currently not on a rumble strip."
  • September 2016 (2016 Season 4 Build), from the release notes: "Dynamic Track:
    • – Increased the effective starting usage level, which controls the amount of rubber on the track, for sessions that have a short Practice and an attached Qualifying prior to a Race.
    • – Improved the calculations used to conduct heat from the tire into the track, and updated the conduction and convection model for the track surface. This results in lower starting track temperatures, but a significantly more dynamic range when cars interact with the track.
    • – The tearing of rubber from the tires versus from the track has been adjusted so that when a tire is not sliding, it is more inclined to pick up track rubber. Also, the calculations for determining the thickness of the track rubber under the contact patch and the rate at which the track will accept rubber have each been improved. The combination of these changes will make the track rubber build up about three times as fast, and in general be more dynamic.
    • – The Dynamic Track system now assumes there is some residual starting dust on the track even before any simulated running of cars or cleaning for a session is performed. The amount of starting dust is related to how must dirt and gravel is around that track, such that a track like Mazda Raceway Laguna Seca is more prone to being dusty than a track like Talladega Superspeedway.
    • – Dust will now be picked up and thrown due to air displacement near moving vehicles."
    • "Dallara DW12: "– Tire wear for the road course tires has been increased to bring the total wear over the course of a stint closer to real-life values."
  • June 2016 (2016 Season 3 Build)
    • From the release notes: "Tires – Improved the effective tire grip calculations related to marbles and dust on track."
    • "Dynamic Track – Dust and gravel can now be dragged and thrown onto the track by wayward cars, which then interacts with the tires to affect grip and accumulation of debris on the tires."
    • V8 Supercar Ford Falcon circa 2012 (which it seems already had V6 tires), now has V6 tires that match the 2014 V8 Supercars.
    • V6 tires added to Ford Falcon FG V8 and Holden Commodore VF V8. "This vehicle now uses V6 tires. These tires are capable of maintaining grip at higher operating temperatures, so they should feel less greasy in hot ambient conditions and more catchable in big slides. However, be aware that grip will be slower to build when the tires are cold, so it will feel icy for the first few laps when ambient temperatures are cold. Also, you will nominally find peak grip at around the 3rd to 5th timed lap on a qualifying run. We understand this is not ideal for 2-lap qualifying runs, but felt that better grip at high operating temperatures (where the tires run most of the time) would be a worthwhile tradeoff against a relatively slow build of grip when cold."
  • March 2016 (2016 Season 2 Build)
    • Tire related updates:
      • "Garage – Initial temperatures of wheels and tires have been improved, especially for cars with tire warmers. Previously, the entire wheel and tire was heated to the tire warmer temperature; now only the tire surface is heated to the specified temperature, while the wheel is more appropriately closer to the ambient temperature. This may produce a subtle change in ride height in the garage, so cars with tire warmers may need an adjustment to pass Tech if they were close to the limit on ride height."
      • "Dynamic Tire Debris Accumulation – Tires on all vehicles now visually show the accumulation and dispersal of debris. This includes materials such as grass, gravel, rubber marbles, dust, and sand. These materials are picked up when driven over based on the surface type, grip, and speed of the vehicle, and then they are removed over time by the same factors. The physics model for this activity has already been running since last season’s update, so there is no change to driving characteristics, but now you can see the effects!"
    • New cars: Audi R8 LMS GT3, Mercedes-Benz AMG GT3, Formula Renault 2.0, Mazda MX5.

2015[]

2014[]

  • September 2014 (2014 Season 4 Build):
    • from the release notes: "Tire Model – The tire tread band yaw response has been improved, and is much better at low speeds, and when stopped. Now while at very low speeds the steering will feel heavy because you are trying to turn the tread but it is not able to roll enough to relax that motion. You should be able to feel the difference in higher and lower pressures much more at low speeds now. The tire will feel different even up to 80 mph, where the new low speed code approaches the old model."
    • Last tire model version (5) added to the two cars that were still on the "old tire model" (pre NTMv1): Silver Crown, Sprint Car.
    • New car: Holden Commodore VF V8.
  • July 2014 (2014 Season 3 Build): all remaining cars (except Silver Crown, Sprint Car, which are still on the "old" pre NTMv1 version) have been migrated from NTMv4 to NTMv5.
  • January 2014 (2014 Season 1 Build)
    • from the realese notes:
      • "For cars with v4 and v5 tires:
        • – The tire probe temperature measurements that are reported in the garage and black box now compute more reasonable equilibrium values to better represent what temperature is actually measured in a pit stop.
        • – Better carcass yaw stiffness and carcass yaw motion. We think this feels better and there is less force feedback chatter as a result too."
      • "For cars with v5 tires:
        • – There have been further improvements to tire heating energy transfer calculations.
        • – The tires now smoke more realistically (and interestingly, that improves the feel over the limit by limiting surface temperature build-up).
        • – Applied a fix to all v5 cars that we had made to the Ruf when it was released in December, which stops certain sidewall loads when a tire is rolled onto the sidewall (heavily loaded, or low pressure) from adding extra grip."
    • New cars with NTM v5: RUF RT 12R AWD, Super Late Model
    • Cars in this build that have updated from NTM v4 to v5: Cadillac CTS-V Racecar, Chevrolet Corvette C6R, Chevrolet Monte Carlo SS, Ford GT, Ford Mustang FR500S, Kia Optima, McLaren MP4-12C GT3, Radical SR8.
    • Cars already on NTM v5 from previous builds (check when they were updated): RUF RT 12R C-Spec, RUF RT 12R RWD, RUFRT 12R Track.

2013[]

  • October 2013 (2013 Season 4 Build)
    • from the realese notes: "New Tire Model – v5 Updates
      • – There is now much better rolling drag computation, which gives more rolling drag and more tire heat.
      • – Improved the low speed vs high speed grip levels. Now there is a little less low speed grip, and a little more high speed grip.
      • – Improved/increased the loss of grip that occurs the thinner the tire tread rubber gets. "
    • Cars that have been updated to the v5 model this season are: Legends Ford ’34 Coupe, Mazda MX-5 Cup, Mazda MX-5 Roadster, Pontiac Solstice, SCCA Spec Racer Ford, VW Jetta TDI Cup
    • New car: Ford Mustang Class B.
  • July 2013 (2013 Season 3 Build):
    • from the release notes: "Tire Model
      • – Fixed a bug that would allow the tire carcass to move too rapidly as it passes through zero deflection. This helps the tires to feel less twitchy.
      • – Fixed a bug in the temperature calculation that helps the over-the-limit feel."
    • Cars added to Version 5 Tire Model (NTMv5 debut?): Lotus 49 (newly released car), Skip Barber Formula 2000, Street Stock.
  • April 2013 (Season 2 Build):
    • from the release notes: "New Tire Model
      • – The way we model tire carcass yaw motion relative to the rim has been improved. This has helped responsiveness.
      • – The NTM tires (and real world tires) are very dependent on temperature which greatly affects the properties of rubber. We’ve always just used 3 slices of tire (inside, middle, outside) to track temperature since way back in the day, but this is not really sufficient for the NTM, since it is so much more critical to get correct temperature than in the OTM or Papyrus tire models. The tire code now computes temperatures for many elements across the surface. Now tires in the sim compute anywhere from 7-9 slices for our narrower tires, to up to 20 slices for the wide tires some of the cars have. The result is that as the tire contact patch is moving left and right across the tire surface the temperatures used by the grip code are more correct and produce a better, more progressive tire temperature effect. Also, the 3 temperatures we record for visual display are now more accurate too (although there is still work to be done there). This change applies to all NTM tires."
    • New car: Kia Optima.
  • January 2013 (Season 1 Build):
    • from the release notes: "New Tire Model
      • – There have been improvements to the modeling of the tire carcass motion, which improves the handling on all the cars. All our NTM cars feel much better with this tire model update, and have had some amount (anywhere from a little to a lot) of re-tuning, so even if a car doesn’t have its own release note does not mean that you shouldn’t try it out to find out how it drives now!
      • – Tweak skid widths, smoke and skid amounts.
      • New Steering Model: – All the cars have better constrained steering systems to go with the tire carcass improvements, giving more precise feel."

2012[]

  • October 2012 (Season 4 Build), cars moved from OTM to NTM (one car, total is 26 cars on NTM): Lotus 79.
  • May 7, 2012 update:
    • "New Tire Model – Prevent the surface temperature from exceeding the burn temperature of rubber. Will help keep the tire from getting too greasy when too hot."
    • NTM improvements and tweaks to Street Stock and Williams FW31.
  • April 2012 (Season 2 Build):
    • from the release notes: " New Tire Model – Fixed an issue where a very lightly loaded tire would lose stiffness, resulting in a "floaty" feeling in the lightly loaded tire. "
    • Cars updated to the NTM (two cars): Chevrolet Impala SS 2009, Dallara Indycar - 2011.
    • New car: Cadillac CTS-VR.
  • January 2012 (Season 1 Build):
    • from the release notes: "New Tire Model
      • – There are improvements to the tire damping forces, both vertical and lateral. There are improvements to the carcass torsional stiffnesses, which affect the load sensitivity. Fixed a significant bug with lateral/vertical force coordinate transformation. These changes have made all the cars more predictable and have improved the tire feel."
      • – "The local driver’s (your) car now produces tire smoke for cars with the NTM.
      • – For all the cars that now have the NTM, existing setups may need some work. There are good baseline setups for all the cars; you may want to start by loading those. Typically, the NTM cars require more front brake bias to avoid spinning under braking. They also often require pressure and camber adjustments from the old tire model setups, as well as ride height adjustment."
      • "Brake Modeling
        • – Almost all our cars now feature a model of brake temperature. When your brakes get hot enough you will see them begin to glow. At a daytime track you can start to see glow if the brake rotor surface is getting hotter than about 1380 degrees F (750 degrees C), but at night you can see glow as the surface exceeds 1200 degrees F (650 degrees C).
        • – The only physical effect, currently, is that the brake rotor can radiate heat into the wheel rim of any car that has the new tire model. The old tire model does not model wheel rim temperature, so this effect does not apply. Hot brakes can really heat up a wheel rim, which will bring up the hot air pressure of a tire by several more psi over the course of a stint than without the brake heat being modelled."
    • Cars added to the NTM (four cars, confirmed 18 cars in total with NTM): Star Mazda, Radical SR8, Riley Daytona Prototype, Williams-Toyota FW31.

2011[]

  • October 2011 (Season 4 Build), from the release notes: "Simulation: New Tire Model
    • – The new tire model is now available on many new cars including most of the Rookie cars (..). There are several improvements that apply to all the cars with new tires, including those you are familiar with already.
    • – You will probably want to start with the baseline iRacing setups provided with these cars – any old setups are likely to need some work at the very least, and they may not work well at all. The new tire model generally requires more forward brake bias than the old tire model, so if you are spinning under the brakes on turn entry, adjust the brake bias forward. The Legends car also has a road setup (road.sto), which is worth trying to get a handle on at Oulton Park – it will really teach you how to drive this car! Hint-mostly with your right foot…
    • – The modeling of tread compounds is improved, with road compounds that are softer and have a better feel. Work continues with the compound modeling, and the tread/surface interaction-tires are still a bit too grippy when cold, but that will continue to improve.
    • – The tire carcass stiffnesses and motion are more realistic, giving a better feel.
    • Known issues: – The carcass lateral stiffness is a bit low at typical real world pressures – you will need to run 5-10 psi higher pressures than you might expect to get the tires to feel predictable.
    • – The tires are overly sensitive to rolling onto an edge, so you will want to run cambers that may be a bit closer to zero than you might otherwise for now. This is also helped by higher pressures.
    • – Very slow speed (< 12 mph or so) behavior is still not 100% – you may notice some cars wobble while stationary, or make tire skidding noises at very low speeds. Best fix is to not drive at very low speeds!
    • - The slow speed issue also arises in the garage for some cars, causing the readings to bounce around a bit. This is usually not a big issue – it is exacerbated by low pressures and large cambers."
    • Added to the NTM (8 cars): Legends Ford ’34 Coupe (advanced) and Legends Ford ’34 Coupe Rookie, Mazda MX-5 Cup, Mazda MX-5 Roadster, SCCA Spec Racer Ford, Street Stock, Chevrolet Monte Carlo SS, Chevrolet Corvette C6R.
  • July/August 2011 (Season 3 Build)
    • from the release notes: "Simulation: New Tire Model (..) The new tires continue to be developed, and we will be rolling out more cars with the new tires as we are able. Setups for cars other than the Skip Barber car will need to be adjusted—we have included some new baseline setups with the affected cars. The tires are a bit more forgiving than in the preview release of the Nationwide car. Low pressures are no longer necessarily the way to go for the fastest laps. If your car feels unstable under braking, try moving the brake bias more forward (higher front bias percentage), since we’ve found that many of the road cars seem to have too rearward of a brake bias on the new tires if using the old setting.
    • Added to the NTM (five cars): Chevrolet Impala (Cup car, Nascar A series), Chevrolet Silverado (truck, Nascar C series), Formula Skip Barber 2000, Ford GT (new car), HPD ARX-01c (also known as Acura LMP) (new car).
    • Car already on NTM from previous release: 2011 Chevrolet Impala Class B
  • June 21st, 2011 update, the New Tire Model debuts with a preview on the new 2011 Chevrolet Impala Class B (COT) car.
    • From the official announcement: "The wait is over. After 18 months of crunching numbers (..)" (so work on NTM started in December 2009/January 2010)
    • From the release notes: "This is a preview version of the iRacing 2.0 tire model; there are a few known issues (lack of tire smoke being the most visible), but the tires’ response is very close to what you will experience when the model is complete. The heavy, high-speed Nascar oval cars work the tires very hard, so be aware that overdriving the car, or pushing too hard, will be costly in terms of laptime and tire life. That said, we think you will enjoy them! "
    • "The new tire model is very susceptible to sustaining mysterious unexpected amounts of damage from wall corners and seams. We have made some improvements to many tracks to reduce the chance of having these weird invisible collisions against certain spots in the walls at many tracks, but there may still be spots against walls where you may find the 2011 Impala B blowing a wheel out unexpectedly. We’ll be working on improving this by the time we do a full release of the new tire model."
  • April 2011 (Season 2 Build), announcement on upcoming NTM preview: "We have an updated version of the Chevrolet Impala Class B for 2011 that is very nearly ready for release, featuring a “preview” version of Dave Kaemmer’s long awaited new tire physics model. If you own the existing Nationwide car you will get it free as the new car is a part of the same car package you already own. It will be made available at some point within the next week or three, once all the details are finalized for public consumption."

2010[]

Reference marks relative to overall iRacing history[]

  • August 26, 2008: iRacing initial release
  • September 2004: Dave Kaemmer co-founds iRacing.com

References and links for further info[]

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