# GTR2Optimal tyre pressure/temperatures?

#### JohannDaart

I drive Gillet on Monza.

I've installed XD hud for tyre and brake temps, and what I've noticed after 2-3 warm up laps:

1) Brakes cool down too fast on long straights, so I lowered down brake "ducts" setting from 5 to 2, and it helped. Now for the time of short 10 lap races they are longer in 300-600 temp range. Good. All ok. I know that for longer races, too little cooling might cause faster brake wear, but I'm only driving short races.

2) I've noticed that after warming up, left tyres are hotter than left ones, that causes slight pressure imbalance, so I wanted to correct that.
- But then I've red that optimal temperature of tyres should be around 90 degrees, no more than 100.
- Some guides say that for a given track, tyre pressure should be as low as possible without causing them to heat up above optimal 90 degrees.
- Other people say that in GTR2 you can forget about balancing left and right side, that the only thing that should be set for tyres in GTR2 is camber, so that temperature spread across a tire is between 5-10 degrees.
- Some other people say that optimal tyre pressure/temp can be checked out in tyre *.tyr files. For Gillet, it's "Dunlop_NGT.tyr", and it says:
Temperatures=(90.0,20.0) // Optimum operating temperature for peak forces, cold starting temp (Celsius)
OptimumPressureBase=90.0 // Base pressure to remain flat on ground at zero deflection

Well, 90 deg as optimal temp seems ok, but you can't even set 90 kPa for pressure in garage, and that's obviously not a number of optimal tyre pressure when they are warmed up, it's too low. I expected something like 180 or 200 kPa.

I've also noticed, that when I drive Gillet around Monza for 10 laps, they rarely go up to 90 degrees when they are around 180 kPa.
Even if I lower pressure down to 140 kPa (that feels wrong), tyre temps don't go up to 90 deg, while I thought that with the lowering of pressure they should...

Tyre temperatures in GTR2 seem to be a bit strange, but whatever, lets focus on their pressure - What tyre pressure should aim for when tyres are warmed up? Is it possible to check it in some files?

#### DucFreak

Tyre temperatures in GTR2 seem to be a bit strange, but whatever, lets focus on their pressure - What tyre pressure should aim for when tyres are warmed up? Is it possible to check it in some files?

Please take a look at the GTR Engineers Handbook, as you'll appreciate it.
For example, in regards to tyre temps, check page 18 and following ones.

In addition, also check the GTR2 Car-Owner's Manual, as it has really extensive data on car specs, including info on ideal tyre pressure and temps (on a per-car basis!).

Both are a must have!

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#### JohannDaart

Thank you Duc

Although... these books made clear how target values after warm up should look:
- 2-3 laps is enough for tyres to warm up to their working temperature.
- 80-90 degrees is optimal working temperature.
- 200kPa is optimal working pressure for Dunlops NGT.

It makes sense, because in novice mode, at the start of practice session tyres are warmed up to 90 deg and 200 kPa, no matter what set up is used, so probably 90deg@200kPa is what SimBin considers ideal.

But ingame I find that it's impossible to target temperatures.
- If I set up 180 kPa in garage, after 3 laps tyres get to around 200 kPa, but max tyre temp is 70 deg...
- If I set up 140 kPa in garage, after 3 laps tyres get to 160 kPa, but max tyre temp is 76 deg, other as low as 62 deg...

They are in 60-70 bracket, nowhere near 80-90 deg...

I wonder if it might be connected to fuel load, I run only 14 L for short stints? I will check it out.

Anyway, after lowering brake ducts, brakes work in proper temp, and now they are much stronger on initial input, so I need to lower brake pressure.
But I've realized that for the whole month since I've started playing GTR2, I was braking with cold brakes because of default duct set too high...

Default GTR2 setup is confusing if it causes player to unknowingly drive with cold brakes and cold tyres.

I will fiddle some more with this tyre pressure setup tomorrow, maybe I will get them up to proper temperature, but after couple test it looks like it's impossible in GTR2 to set up tyres so when they warm up they are at theoretical 85deg & 200 kPa.
I've seen on YouTube that in other sims like Assetto or Project Cars such values after warmup are common, maybe GTR tyre model is not so realistic in that regard.

Then maybe in GTR2 tyre temps are not that important and it's best to roll with default pressure and adjust camber for the even inner/center/outer temp spread for every wheel.

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#### VERT

- But then I've red that optimal temperature of tyres should be around 90 degrees, no more than 100.
Over 90 degrees (average of the entire tyre) you lose too much grip, so no more 90 deg. at the apex.

- Some guides say that for a given track, tyre pressure should be as low as possible without causing them to heat up above optimal 90 degrees.
"as low as possible" - up to a certain limit. You will get more tyrewear, less max speed, less grip.

- Other people say that in GTR2 you can forget about balancing left and right side, that the only thing that should be set for tyres in GTR2 is camber, so that temperature spread across a tire is between 5-10 degrees.
And caster, springs, ARB

Well, 90 deg as optimal temp seems ok, but you can't even set 90 kPa for pressure in garage, and that's obviously not a number of optimal tyre pressure when they are warmed up, it's too low. I expected something like 180 or 200 kPa.
It's optimal temp without a load. Under load (downforce and gforce) this value should be higher.

I've also noticed, that when I drive Gillet around Monza for 10 laps, they rarely go up to 90 degrees when they are around 180 kPa.
Even if I lower pressure down to 140 kPa (that feels wrong), tyre temps don't go up to 90 deg, while I thought that with the lowering of pressure they should...
Lower pressure is more temp, but more important that 180 front / 140 rear changed car balance to understeer. Also it adds a little longitudinal grip for rear tyres

Tyre temperatures in GTR2 seem to be a bit strange, but whatever, lets focus on their pressure - What tyre pressure should aim for when tyres are warmed up? Is it possible to check it in some files?
For tyre temperature it needs to set springs, then camber/caster, and only then pressure

i hope this text is understandable. English is not my strong point

#### DucFreak

Default GTR2 setup is confusing if it causes player to unknowingly drive with cold brakes and cold tyres.

I will fiddle some more with this tyre pressure setup tomorrow, maybe I will get them up to proper temperature, but after couple test it looks like it's impossible in GTR2 to set up tyres so when they warm up they are at theoretical 85deg & 200 kPa.
I've seen on YouTube that in other sims like Assetto or Project Cars such values after warmup are common, maybe GTR tyre model is not so realistic in that regard.

Then maybe in GTR2 tyre temps are not that important and it's best to roll with default pressure and adjust camber for the even inner/center/outer temp spread for every wheel.

It's been many years since I've looked at GTR2 default cars in such detail (or competitively) but, from memory, while the ideal temp is ~80ºC, maintaining them between 65ºC~95ºC (and ~10ºC difference from inside to outside of tyre) was more than OK for me (to keep best grip and wear).

If so curious, maybe try a softer compound (if possible) and see if same exact thing happens(?).
Notice that when a driver struggles to get higher temperatures on tyres, it could also be down to other simpler variables (unrelated with car setup) such as low temperatures on track, or too conservative driving.

I agree that the default GTR2 setups can be confusing, and definitely improvable.
Something that is usually not mentioned is that, at release, GTR2 was somewhat divise in the userbase migrating from GTR1. One of the things that caused commotion was that the original GTR1 came with more documentation, with custom qualify and race setups (provided by the developer) for each and every default car and track, and more difficult physics.
GTR2 did not have the same ammount of documentation, nor the custom qualify and race setups, and the physics were a bit more forgiving (actually better, IMO). And that, along with the absence of Starforce DRM (content became fully visible and unlocked), was one of the reasons why the community saw so many modders embrace it (the default content), with documents, setups, and even different physics (at some point, NAP mod was really popular).

EDIT: good reply above by VERT.

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#### Shovas

Please take a look at the GTR Engineers Handbook, as you'll appreciate it.
For example, in regards to tyre temps, check page 18 and following ones.

Been reading through this and I'm finding this to be one of the best guides I've ever come across for learning car setup terminology and what each components impact is in actual scenarios. It's much better than the somewhat vague iRacing tooltips.

The Experts Q&A starting on page 16 is also great to expand on the technical points described before it and get down into brass tasks "here's how it feels on track, how should I adjust it?"

I'm definitely going to re-host this on my blog and convert it to web friendly html.

In addition, also check the GTR2 Car-Owner's Manual, as it has really extensive data on car specs, including info on ideal tyre pressure and temps (on a per-car basis!).

Also a great doc for those wanting the specific technical details of their GTR2 cars.

#### Shovas

I was watching my tire pressures and temps in my last GTR2 session and I found they were increasing as expected through 3-5 laps. If had to hazard, they were about 80% at 3 laps and reach about 100% of their ranges in 5 laps. I was driving the HQ F575 GTC on HQ Magny-Cours.

Also, I'm using the HQ Cars (from the HQ Mods Collection) and I would recommend those over the original cars. I spent a lot of time *trying* to dial in ffb on the original cars in dry and wet conditions and I never was able to get satisfactory rain driving on the original cars. It was doable but very, very horrible driving and I suspect not quite realistic. This tells me something's not quite right with their setups. On the other hand, with the HQ cars I was able to dial in FFB in dry and wet conditions with much better results. Driving in the rain wasn't so insane, it was noticeable but not driveable without worrying about crashing every lap.

#### Shovas

By the way, any stability issue installing the XD mod? I'm always wary about those DLL mods.

#### Jempy

I've been using XD in GTR2 and Race07 for years without any problem ...

Just pay attention to other "mods" using the same d3d9.dll and applying the recommended actions you always find in the readme.

#### JohannDaart

After more tests I figured out why default tyre pressure in garrage is set by SimBin on 160 kPa.
I've set camber on all wheels to zero out of curiosity, and I found out that even at 150 kPa, center tyre temp is lower than inside and outside temp, that means that the tyre is underinflated in that track conditions (middle "low pressure" pic):

So when the track weather is at 20 degrees, 160 kPa is the lowest tyre pressure that gives correct pressure after warmup (left "correct" pic).

Even at this lowest correct pressure, tyre temps don't go up to 90 degrees after warmup laps in Gillet. So I guess there's no point chasing some "optimal working temperature".
Gillet GT3 is not that fast compared to GT cars, so maybe temperatures go higher in cars like Lambos or Maseratis.

Second thing I realized, that by default, camber is set in a way that spreads outside and inside temps by 5 degrees.
Monza is a track with long straights, so the camber should be set in a way that gives best grip on the straights, not on the corners.
In the Engineers Handbook linked by Duc (thank you a lot! ), it is said that inside-outside tyre temp spread should be no more than 10 degrees.

So I guess best way to set tyres in GTR2 is to forget about targeting certain temperature/pressure values, just focus on camber considering track type:
- Tracks with long straights - low negative camber so temp spread is below 5 degrees
- Tracks with many corners - higher negative camber so temp spread is below 10 degrees
In both cases making sure pressure is set so center temp is between outside and inside temp.
That will result in best possible grip.

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