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   Home      iRacing-Help      Tyre-model
iRacing Tyre / Tire Model
Share an easy link:
Tyre or Tire, the rubber things connecting us with the road.... 
Also see NTM information at bottom of page
From 2016 s4 patch 2 release notes:
- Aston Martin DBR9 GT1, Chevrolet Corvette C6.R GT1, Ford GT
Tire warmers are now used for this car. Temperature is set to what we would see with blankets or an oven, as used on GT3 cars. 

- Dallara DW12
Road course tire wear has been significantly increased to ensure more realistic degradation. 

From 2016 s4 patch 1 release notes:
Dallara DW12
- Slightly tweaked the road course tires to give a bit more degradation.
Other car related changes - check the release notes.
From 2016 s4 release notes:
- Brake bias adjustment is now available for this vehicle in Official, Fixed Setup series.
Cadillac CTS-V Racecar, Dallara DW12, Kia Optima, NASCAR Camping World Chevrolet Silverado, NASCAR Camping World Toyota Tundra, NASCAR K&N Pro Chevrolet Impala, NASCAR Sprint Cup Chevrolet Impala COT circa 2013, NASCAR Sprint Cup Chevrolet SS, NASCAR Sprint Cup Ford Fusion, NASCAR Sprint Cup Toyota Camry, NASCAR Truck Series Chevrolet Silverado circa 2013, NASCAR XFINITY Chevrolet Camaro, NASCAR XFINITY Ford Mustang, NASCAR XFINITY Toyota Camry, Ruf RT 12R, Street Stock.

From 2016 s3 release notes:
We have performed an extensive update to all track surfaces to better model physics collisions, even with tiny particles like sparks, gravel, and marbles.
The dynamic track surface now includes dust and gravel, which is brought onto the racing surface from off-track excursions and affects tire grip.

- 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.

- The way the Dynamic Track is stored in a replay has been improved to allow sudden changes in the track surface state to be seen immediately.


- Improved the effective tire grip calculations related to marbles and dust on track.

Aston Martin DBR9 GT1
- The tire compound has been adjusted to better handle high operating temperatures; it now is matched to the Chevrolet Corvette C6.R GT1.

Cadillac CTS-V Racecar
- Tire construction has been changed to be more forgiving at and over the limit.

Chevrolet Corvette C6.R GT1
- A more temperature resistant tire compound has been added, so that the Chevrolet Corvette C6.R GT1 is more competitive with the Aston Martin DBR9 GT1, particularly in hot ambient conditions.

Ford Falcon FG V8
(see release notes for big changes)
- 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.

Holden Commodore VF V8
(see release notes for big changes)
- 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.

Global Mazda MX-5 Cup
- Fixed an issue with an incorrect normals texture reference with the vehicle tires.

Radical SR8
- Unfortunately, the developments for Season 2 did not have the desired effects on car performance, drive-ability, and real-world correlation. As a result, this vehicle has been restored to the 2016 Season 1 specifications.

V8 Supercar Ford Falcon circa 2012
- This vehicle now has V6 tires that match the 2014 V8 Supercars.

From 2016 s2 patch 2.1 release notes:
- Fixed a bug where performing a driver swap would not transfer how cured the tire's rubber was to the next driver, so the next driver would be able to continue on much faster rubber without having taken the time to swap a tire.
-- Please note that a separate existing bug, where the reported values in the Tire Info's Black Box may not show the correct values during a driver swap, has not been fixed at this time, but you may be assured that the physics and racing behavior are working correctly. 

From 2016 s2 patch 1 release notes:
- Setup changes that are applied during a pit stop (like tire pressures) are no longer kept when the Sim advances from one session to another. Immediate in-cockpit adjustments (like brake bias or traction control setting) are still kept across a session transition. 

From 2016s2 release notes:


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.

- Smoke and debris generated by opponent vehicles can now be seen.

- Opponent vehicles now show wheelspin and lockup, and skids and smoke from these actions are more realistic.

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!

see release notes for much more detail

BMW Z4 GT3, converted to Pirelli. Updated to match Mercedes AMG GT3.
Chevrolet Monte Carlo SS, reduced tire grip.
McLaren MP4-12c GT3, converted to Pirelli.
McLaren MP4-30, tire wear and degradation rate has been increased.
NASCAR - check the release-notes for various things.
Radical SR8, tire grip has been increased.
Star Mazda, tires now heat up faster; the goal is to have the tires come in more quickly from cold. Ideally, a fast lap is a timed 3rd or 4th lap.
Star Mazda, tire stiffness has been greatly reduced at both front and rear. Tires now seem better matched and have slightly more progressive breakaway characteristics.


Audi R8 LMS GT3, Formula Renault 2.0, Mercedes-AMG GT3, and Mazda MX-5 Cup
GARAGE From 2016s1 release notes:

Cars with tire warmers will now use the tire warmers while in the garage. The "Cold Pressure" setup item is now renamed "Starting Pressure" to reflect this change. iRacing setups have been adjusted for this change, but you will need to increase your tire pressure on any pre-existing setups to keep your hot tire pressures out on the track in the right place. You will need to raise your cold pressures for the various cars that have tire warmers by approximately the following amounts in order to convert them to a "Starting Pressure" value:
  • Aston Martin DBR9 GT1 = +3.0 psi
  • BMW Z4 GT3 = +6.5 psi
  • Chevrolet Corvette C6.R GT1 = +3.0 psi
  • Ford GT GT3 = +6.5 psi
  • HPD ARX-01c = +5.0 psi
  • McLaren MP4-12C GT3 = +6.5 psi
  • Ruf RT 12R Track = +6.5 psi
  • Williams-Toyota FW31 = + 5.0 psi.
- Cars without tire warmers will now enter the world with exactly the tire pressure specified in the garage, instead of always being a couple of psi higher than specified. iRacing setups have been adjusted for this change, but you will need to increase your tire pressure on any pre-existing setups to keep your hot tire pressures out on the track in the right place. The typical change for any car will be approximately +1.5 psi.

McLaren MP4-30
- New car added! The McLaren MP4-30 Formula 1 racecar features a few cutting edge systems that help set it apart from the pack, including the Drag Reduction System (DRS) to enable boosts of speed on straights, the Energy Recovery System (ERS) to re-charge the vehicle's batteries, and the Motor Generator Unit (MGU) to provide even more power for overtaking. Jump in the cockpit and get ready to experience a truly modern racing machine.
ED: Some useful links for the McLaren MP4-30
DRS & ERS explained by Team Redline youtube
MP4-30 Quick User Guide [ pdf attached to thread ]
For me: filed.
Wheel button mapping thread
Follow up posts - anyone willing to paraphrase this for me please?
• GARAGE TEMPS post by Eric H (16 Dec 2015):
Just for clarification our 'garage temperatures' are a combination of carcass and surface temps using conduction methods to calculate what is displayed.
They are not solely surface temps, which you can get from telemetry, nor are they carcass temps.
This method is how a probe would read; remember a tire probe pierces the surface and takes a reading within the tread.

In regard to flat spotting we don't have a model yet that localizes rapid heating that would have blocks of the tread that are hotter than others.
If you lock a wheel your entire tire surface 'gets hot'. This is partly why too much grip is lost in those types of events.

There is somewhat of a small bug in our implementation of tire warmers in that the blanket is essentially also heating up the wheels!
The carcass temps fall because wheels cool fairly quickly, which therefore bring down the tire pressures due to conduction through the rims.
If the wheels were kept at ambient instead there would definitely be less heat flow out while driving hard.
We're working on a fix. At this point it just means you may have to apply more 'starting pressure' to hit your on-track targets.

Post by Eric H (18 Dec 2015):
We could output temps in any form or fashion - and for dev purposes we do.
But what we are trying to do for members is output temperatures that are representative of how they would be measured on a real car at the race track.
Those being surface temps (akin to using IR mounted sensors), core temps (akin to using a pyrometer probe) and at least on one other car inner air temperature (akin to an internal air temp sensor).

BTW, there is no funny business going on trying to hide how the tire model works.
It's pretty organic and would be hard for us to do something like that anyway - every bit is linked to every other bit and hacks would break the thing!
The reason we don't output a lot more information isn't for any maniacal theory but because outputting things that aren't physically representative in the real world doesn't really make a lot of sense.
For instance, you can't measure carcass temps on a real car either on pit road or on the race track.  (See thread for more comments).

Post on the OVAL side by Eric H (18 Dec 2015):
1. Less tread changes the cornering stiffness of the tire.
This change doesn't have anything to do with the carcass and it's stiffness but really the amount of grip per unit of slip.
Increasing cornering stiffness of a tire, say by shaving it, can make it feel more edgy, have a higher grip peak but also a harder grip fall off beyond peak.
2. Optimum range is as cool as you can possibly keep them.
You'll notice your early laps are fastest and that's because they are coolest and therefore have the most grip.
3. I can't answer that because it'll depend on all sorts of things. Generally, though, you should target less spread than more spread.
4. I'm not clear on this question but I can say that the tires do deform in all directions - this includes the carcass sidewall, carcass belts and the tread.
5. It's not a percentage per se but a heat flow calculation based on how deep we are measuring. That'll depend on how much tread is remaining. Then once that's figured we'll calculate the heat flux. If the surface is really really hot and the carcass is cool more of the temp reading will come from the surface. Vice versa is true too.

From the same thread...

Q: Ok, how does the cornering stiffness go UP with LESS material on the surface?
A: Less tread will shear proportionally less.

Reference to shear explained by Eric H, post:
You're using shear as a verb and I'm referring to it as a noun. I could have used the term deflection. A tire with half the tread, notwithstanding the improved thermal control, will see half the deflection for a given load. To reach equilibrium and generate the same force more tread depth will require more deflection, or slip.

Another analogy for car guys out there. Cut a spring in half and it's stiffness will double. The material properties haven't changed but the resultant rate of deflection has. A tire tread 'spring' in shear, bending, compression, or whatever works the same way.

But, a big but, as tread wears down it can effectively get harder as the tread depth approaches zero. The reason for this is the really stiff carcass can now impart some of it's stiffness into the rubber. Think of a huge soft block of rubber sitting on your desk in front of you, like 5 inches thick or something. If you press your fingers into it perhaps it will deflect a bunch. Now shave a very thin layer off of it and try to deflect that very thin layer. It won't deflect nearly as much because of the solid surface underneath, being your desk, is limiting it. Same thing can happen on a tire. But we're talking at less than probably one to half a millimeter, or something, of tread remaining.

Noted: Don't get confused with a stiffer construction and a stiffer grip response. Interlinked they are but they are also two different things. Tire heating affects performance from a cycling standpoint too. Tires get harder as they heat up. RS tires will heat more than LS tires on an oval car and harden faster.

Ed: For the OVAL side, I suggest reading thread  Ride Height Sensor Location (12/2015).
iRacing v6 Tyre Model  (New Tyre Model 6 / NTM6).
2016s3: Falcon & Holden V8SC added NTM6
2016s1 release notes:
"Physics. Zero pressure stiffness calculations have been updated for better realism."

Related post by Eric H: "Really tires have some amount of stiffness even when air pressure is zero.
Although our model hasn't been going to zero stiffness when a tire contains no air DK has come up with a better method to calculate how stiff the carcass behaves when it this condition."

Another related post by Eric H: "It does matter now as this change impacts the stiffness slope with change in air pressure. Off of some reference inflation pressure less air pressure will retain more stiffness and more air pressure will gain less than before."

2015s4 release notes:
V6 tires now include a term in the lateral stiffness calculations that was missing in the NTM previously (including the v1-5 tires).
All prior cars with v6 tires from last season have been revised to suit, and many more cars have been upgrade to v6 tires.

Aston Martin DBR9 GT1. BMW Z4 GT3. Cadillac CTS-V Racecar. Chevrolet Corvette C6.R GT1. Chevrolet Corvette C7 Daytona Prototype.
Chevrolet Impala Old Class B. Chevrolet Impala-COT. Chevrolet Monte Carlo SS. Chevrolet Silverado - circa 2013. Ford GT. Ford GT GT3.
Ford Mustang FR500S. HPD ARX-01c. Kia Optima. Legends Ford '34 Coupe. Lotus 49. Lotus 79. Mazda MX-5 Cup. Mazda MX-5 Roadster.
McLaren MP4-12C GT3. Modified - SK. NASCAR Camping World Chevrolet Silverado. NASCAR Camping World Toyota Tundra.
NASCAR K&N Pro Chevrolet Impala. NASCAR Sprint Cup Chevrolet SS. NASCAR Sprint Cup Ford Fusion. NASCAR Sprint Cup Toyota Camry.
NASCAR Whelen Tour Modified.  NASCAR XFINITY Chevrolet Camaro. NASCAR XFINITY Ford Mustang. Pontiac Solstice. Radical SR8.
Riley MkXX Daytona Prototype. Ruf RT 12R AWD. Ruf RT 12R C-Spec. Ruf RT 12R RWD. Ruf RT 12R Track. SCCA Spec Racer Ford. Silver Crown.
Skip Barber Formula 2000. Sprint Car. Star Mazda. Street Stock. Super Late Model. VW Jetta TDI Cup. Williams-Toyota FW31.

V6 tyre changes: driveability, tyre degradation, and vehicle response.
2015s3 release notes:
Dave K has a new model of the tire carcass that does a much more accurate computation of the tire's stiffness.
Amongst other things tires now respond much more correctly to tire pressure changes.
This is what is called a "Version 6" tire. Most of our road course cars have been updated with this.

* David K's 2011 NTM & temps post.

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