Comparing setup from iRacing for same car in AC when the tire pressures values differ

[Davy Jones]

I've been watching Niki Thiim's video on the Porsche 911 GT3 Cup car in iRacing and trying to follow his setup changes for the Nordschleife.

I know that the physics and tyre models etc in AC and iRacing differ and have their own features and quirks. So trying to transfer a setup from one to the other should not I guess be possible nor even correct. I still wanted to take Niki's setup as a reference points since the Porsche 911 GT3 Cup car in both should in a way be the same.

I noticed though in AC that the tyre pressures are presented in psi where as in iRacing its kPa. I don't know of an option in AC to switch the value types at least metric to imperial option support it.

I can always convert online e.g. 165 kPA = 24 psi but is there an easier way and if possible within AC itself?

 

[mclarenf1papa]

No way to convert units within AC....also the AC tire pressures are wrong.

 

[Cote Dazur]

No way to convert units within AC....also the AC tire pressures are wrong.

In which way are they wrong?

 

[Michael Hornbuckle]

No way to convert units within AC....also the AC tire pressures are wrong.

In which way are they wrong?

 

[natedogg1867]

In which way are they wrong?

The Porsche Cup Car in AC uses the same optimal pressures that the GT3 cars use in AC. So, 26 psi is optimal (hot pressure), and any deviation from that is going to see you lose grip, etc.

However, that isnt exactly correct.

The PCC uses the Michelin Porsche Cup N2 tire for Carrera Cup Deutschland this year, and you can see some specs here - click. Front tires are the 27/65-18 and the rear tires are the 31/71-18.

From that link, you can view the technical recommendations pdf file, which lists the recommended minimum hot pressures.

The front tire does seem to have a minimum hot pressure of ~26 psi from what I can gather, however the rear has a minimum hot pressure of ~31-2 psi. So, quite a bit higher than what AC uses as optimal.

This is also just the minimum hot pressure, which can be higher depending on the camber you use. Front seems to have a range of ~26-30 psi, and rears ~31-33 based on the default camber values of -4.5° front and -4.0° rear.

You can see all this in the pdf file in the link though.

I reckon this also isnt the only car in AC with this discrepancy. In the end though, if the car behaves the same as the real car at the optimal pressures AC uses, Im not sure how big of a deal that really is. Someone far more knowledgeable than me could answer that, as I have no idea.

Edit: According to that screenshot in the OP, iRacing also uses the wrong pressures for both the front and rear if those are considered optimal in iR (171 kpa front hot and 176 kpa rear hot)

 

[mclarenf1papa]

The Porsche Cup Car in AC uses the same optimal pressures that the GT3 cars use in AC. So, 26 psi is optimal (hot pressure), and any deviation from that is going to see you lose grip, etc.

However, that isnt exactly correct.

The PCC uses the Michelin Porsche Cup N2 tire for Carrera Cup Deutschland this year, and you can see some specs here - click. Front tires are the 27/65-18 and the rear tires are the 31/71-18.

From that link, you can view the technical recommendations pdf file, which lists the recommended minimum hot pressures.

The front tire does seem to have a minimum hot pressure of ~26 psi from what I can gather, however the rear has a minimum hot pressure of ~31-2 psi. So, quite a bit higher than what AC uses as optimal.

This is also just the minimum hot pressure, which can be higher depending on the camber you use. Front seems to have a range of ~26-30 psi, and rears ~31-33 based on the default camber values of -4.5° front and -4.0° rear.

You can see all this in the pdf file in the link though.

I reckon this also isnt the only car in AC with this discrepancy. In the end though, if the car behaves the same as the real car at the optimal pressures AC uses, Im not sure how big of a deal that really is. Someone far more knowledgeable than me could answer that, as I have no idea.

Edit: According to that screenshot in the OP, iRacing also uses the wrong pressures for both the front and rear if those are considered optimal in iR (171 kpa front hot and 176 kpa rear hot)

This (and thank you for making this post).

Also, in AC, tire pressures don't behave correctly (there's an issue with the temp : pressure formula that's too extensive of a fix at this point in AC's life), so the discrepancy between real and sim optimal pressures doesn't mean much, if anything at all, besides the numbers being different. And yes, quite a few cars in AC share this issue (including all of the GT3s). It's not game-breaking by any means but just something to keep in mind when comparing to other sims and real life.

Aside from that, pressure does quite a lot of complex things to a tire that I can only envision RF2 coming close to modeling correctly (but don't even get me started on the practicality of its tire model), so it's worth just going with what makes sense for a given sim, as each has its own nuances (e.g. in AC, aim for the optimum pressure number and you should be fine).