Quote from MadCat360 :

So you're comparing new tire model improvements between builds using an old tire model car? There's your problem.

I really like the improvements in this build.

i dont have any problems at all. I´m gonna quit iracing and start playing rfactor 2. yes itss the game thats cheaper and better then iracing

Quote from CodeLyoko1 :

i never drove start mazda, i only drove the skip barber, mazda mx5, dallara indycar and f1 before the update and dalara after

And which is the odd one out in those cars with respect to the NTM? :rolleyes:

Quote from boothy :

And which is the odd one out in those cars with respect to the NTM? :rolleyes:

i dont understand shit from wht you said

Star Mazda
Skip Barber
Mazda MX-5
Dallara Indycar
Williams FW31

Which one does not have the NTM? Which ones got the NTM for season 1?

The new Star Mazda drives like shit, you can't turn while accelerating.

Yea Star Mazda is borked now

Quote from CodeLyoko1 :

i dont understand shit from wht you said

He means the Dallara is still on the old tyre model this season.

Quote from DaveWS :

He means the Dallara is still on the old tyre model this season.

it is in the new one. the tricks i used to do on road america is now impossible to do. or they have changed the fixed sets.

Subsriced last Sunday and looks pretty nice and feels really good. And already got my first Rookie with Mazda MX-5 on Okayama Short.

Yep. A sim racer and a real life racer speaks here.


I love it how the fanboys just ignore the post.

http://members.iracing.com/jforum/posts/list/50/1843544.page

Anyone one watching: http://www.iracing.com/live/

DWC Oval round 1 - lap 47 of 100 as I type this.

Quote from Jshort :

Yep. A sim racer and a real life racer speaks here.


I love it how the fanboys just ignore the post.

http://members.iracing.com/jforum/posts/list/50/1843544.page

Yeah I've said that same thing for quite a while now. The cars just change direction so fast, and they use to change inertia values constantly in beta (still got some release notes from it).

Quote from jrd.racer :

Anyone one watching: http://www.iracing.com/live/

DWC Oval round 1 - lap 47 of 100 as I type this.

You mean watching a crashed stream?

Was in spectator slot and broadcasted some of it for people on TS.

LOL yeah 'crashed stream' - was getting boring anyways, silly longa$$ green flags on Daytona.

do you broadcast on twitchtv?

Nah, use Livestream. Allows the users to adjust what video quality they like (Mobile, low, medium, high, HD) and am able to push out 720p. I've done Twitch/own3d, and while I can push out the same quality, it has a lot less freedom as far as qualities, screen size, chat, etc.

So I can push out near the same quality of those other broadcasters, but the problem is that I do it on my own personal PC, so the broadcasting team would always be mainly me, and it is hard to dedicate that much time to it.

Speaking of broadcasts, anyone watch the V8SC series broadcasts? Here is a recorded version (less quality than live), pretty good racing.

Quote from Jshort :

Yep. A sim racer and a real life racer speaks here.


I love it how the fanboys just ignore the post.

http://members.iracing.com/jforum/posts/list/50/1843544.page

Could you quote that? I can't go there, because I haven't rented this iPay thing.

"It amazes me to think that people actually STILL believe throttle braking, and the way it works in iRacing is just "the way it is" lol. I have never had to do it in other sims (rFactor,LFS,NKP) in such a ridiculous way. When I get on the brakes in a real car I actually have time to react to the weight transfer and position the car accordingly, instead of having this weird instant change in direction that is unnatural and unpredictable. I don't like having to react to little twitches and changes in the cars direction, because no real car is like that at all. Driving a real car fast is fluid and smooth, not twitchy and unpredictable. I will say this again, and I'm sure people with no experience will tell me I'm wrong, but I don't feel like the cars have enough inertia..they just shouldn't move as quickly as they do.

I do not like throttle braking at all, but it's the only way i can get a somewhat natural feel for the car under braking to where I can confidently brake late and deep. Atleast in some of the lighter cars.


It has nothing to do with the diff or whatever, it's just the way the car reacts too quickly. Why is this???? I know other drivers who have raced in real life can relate, so why is this such a mystery? Why is it that whenever you are going into a spin you can just lock up the brakes and the car will instantly snap straight? Mass much?"



I've always felt iracings weight transfer was exaggerated but I'm no expert. More wrong over there than just the tire model in my opinion. I'm just happy that I'm not the only one who feels this way.

Alot of the iRacing forum regulars are asslickers fo' sho'. Makes me laugh that alot of people think the tyre on grass physics are realistic. Not to mention throttled braking etc.

Quote from Jshort :

Yep. A sim racer and a real life racer speaks here.


I love it how the fanboys just ignore the post.

http://members.iracing.com/jforum/posts/list/50/1843544.page

I have never read those threads before, it seems that is true what you guys say about the fanboys, makes me want to cut them with a machete

I use both at the same time in real life, but not like some guys do in iRacing. Not during full threshold braking. Though I could see where that technique could be useful.

Ultimately a driver's opinion doesn't hold much more weight than any old sim racer - both are witness statements. What actually demonstrates what is right and what is wrong is data. Evidence. It's so freely available in iRacing that it simply staggers me these days that people who are serious about their assertions don't prove them with the mountains of data that is being generated for them. Or, at least, go into the data, find something odd, and then ask more questions about it.

Turns out not that many people care that much, and so only a few people actually go far enough to find out more about the model they are analyzing.

By the way, I have been very fascinated by Scott Liang's postings. He seems to be one of those people that formulates an idea having only done no or very minimal investigation and then runs with it, formulating more ideas on top of his already assumption-ridden ones. In the thread Jshort posted he actually claims throttle while braking makes "ground effects."

Quote from MadCat360 :

In the thread Jshort posted he actually claims throttle while braking makes "ground effects."

Well duh, it creates the effects of braking and throttle at the same time!

That can't be true.

Hi, guys. I just wrote up some functions to get the vehicle and tire slip angles out of the iRacing telemetry. Check forum here if this sounds like your cup of tea:

http://members.iracing.com/jfo ... list/1477369.page#4240355

Cut paste someone please; not a current iR subscriber!

Quote :

EDIT: The current file that you should have should be Slip_Angles_Fix_3.zip.

I've just written up some functions to get the slip angles at each individual tire along with the slip angle of the vehicle. Thank you, iRacing, for adding the x/y/z velocities to the telemetry output which is what made this possible.

Attached are five files. Four of these are preconfigured with the Radical specs as best as I could come up with them. The fifth function, Slip_Angle_Vehicle, does not require any customization and should always work with any car. So if you want some immediate results, hop in the Radical, then go to the garage and set the front and rear toe angles to 0. Record a run and off you go.

Unzip the file attached here and plop the five functions here:

Documents\McLaren Electronic Systems\ATLAS 9\Funclib

Warning: The front slip angles will not be correct as I have them set here. I assumed the steering ratio was 14:1 on the Radical, but I have no idea what it really is.

Go have some fun now and come back to read the rest of this when you want to try a different car. I'll wait here

Ok, you're back? Great!

When you want to change cars or use toe angles that are not set to 0, or you change the steering ratio, you need to adjust values in the individual slip angle functions. There are four functions for getting tire slip angles (one for each tire):

Slip_Angle_LF (Left Front)
Slip_Angle_LR (Left Rear)
Slip_Angle_RF (Right Front)
Slip_Angle_RR (Right Rear)

This follows the same format as all of the other iRacing functions so should look familiar.

There are two cases when you need to manually edit two or more of the functions:

1) If you use any toe angle this needs to be typed manually into the function definitions. When you change the front toe angle you need to change the ToeInSetting in BOTH of the front tire Slip_Angle functions. Likewise, if you change the rear toe setting you need to change the value in both of the rear tire Slip_Angle functions. Easy enough? Good!

2) If you change cars you need to update values in all four of the Slip_Angle functions individually. Do not simply copy and paste one function definition to another one. They all look the same but they aren't really. There are little negative signs and things that vary between them, so do it the hard way: Load each function one by one and type things in manually so you don't end up with garbage data showing up in the telemetry. If there's a mistake made, the error will only show up as a degree or so in many cases, so it won't be immediately obvious when something's wrong. Be very careful...

As an example, here's what the Slip_Angle_LF function definition looks like:

ToeInSetting = 0/16
SteeringRatio = 14

FrontWeightPercentage = 38
TireDiameter = 16
TrackWidthMillimeters = 1800
WheelBaseMillimeters = 2370

RadiansToDegrees = 180 / 3.141593
DistCGY = -TrackWidthMillimeters * 0.5 * 0.001
DistCGX = WheelBaseMillimeters * 0.001 * FrontWeightPercentage * 0.01
ToeInDegrees = asin(ToeInSetting / TireDiameter) * RadiansToDegrees
TireSteerAngleDegrees = ($SteeringWheelAngle / SteeringRatio) * RadiansToDegrees
VelocityTireXFromYaw = $YawRate * DistCGY
VelocityTireYFromYaw = $YawRate * DistCGX
VelocityTireTotalX = $VelocityX + VelocityTireXFromYaw
VelocityTireTotalY = $VelocityY + VelocityTireYFromYaw
return (atan(-VelocityTireTotalY/VelocityTireTotalX) * RadiansToDegrees - ToeInDegrees + TireSteerAngleDegrees)


All four functions look almost exactly like this. The ToeInSetting is at the top in all of them so it's easy to find and change. This is the only garage/setup parameter that needs to be updated when you're playing with a given car, with the exception of SteeringRatio on some of the cars. If you don't get the correct values here, the slip angles will all be off by the amount of the toe angle. Be very careful because it's easy to forget or put the wrong toe angle in the wrong function (putting the front toe in a rear slip angle function, for example, or the rear track width or rear tire diameter in the front slip angle functions).

The next block of numbers are specific to each car and should be self explanatory. What you have to be careful about here is that when you are in the front slip angle functions, you are setting the front track, the front diameter, and the front toe setting. This better be the same in both front slip angle functions if the car is symmetrical at the front end.

The same goes for the rear slip angle functions. When you set "TrackWidthMillimeters" in a rear slip angle function, you are setting the rear track width. When you set TireDiameter you are setting the rear tire diameter. And again, this needs to be updated in both of the rear slip angle functions.

EDIT: Michael Watson asked if asymmetrical toe is supported. Yes, it is. Perhaps a better way to think of the toe angle setting in each function is that you're setting the toe for that individual tire. So on a road car if you have -2/16 toe-in at the front (negative toe-in is the same as toe out), the toe needs to be set to -2/16 in both of the front tire functions.

TIP: Unless you're playing with asymmetrical toe as Michael suggested, you will always change either two files or all four, never just one file. It might help to try to remember to think in pairs.

You only need to pay attention to the first six lines. The top one or two are adjustments in the garage. The next few are specific to each car and don't need to be changed unless you change cars.

One other detail: Tire diameter and toe need to be set to whatever you see in your garage. It shouldn't matter if you're using inches or mm or whatever, so long as both the ToeInSetting and the TireDiameter are using the same units.

However, TrackWidthMillimeters and WheelBaseMillimeters must be specified in millimeters. No other unit will work correctly.

Inaccuracies: Bump steer is not included in these functions. The slip angle error at any give tire will be equal to the amount of bump steer the car has at that corner's suspension deflection at the moment the slip angle is calculated. I imagine iRacing probably models bump steer, but I think this is usually some small fraction of one degree, so it shouldn't throw in too much error. It might be safe to assume you're probably going to be within 0.5 degree accuracy here or better on the tire slip angles, but I'm not really sure.

Steering geometry effects (Ackerman) are also not included. These functions assume the front tires are simply steered by the steering wheel angle divided by the steering ratio.

That's it for the inaccuracies. On to the fifth function: Slip_Angle_Vehicle. This is the slip angle of the entire vehicle which is a little different from what it is at the tires. If you were drifting this would be "drift angle." Those of you who have been curious how rear tire slip angles and vehicle slip angle are related can now see for yourselves.

One more thing. In iRacing the lateral velocity (VelocityY) is negative in a left hand turn. I've flipped a sign where needed in order for the slip angles to come out positive in left turns and negative in right turns in accordance with SAE J670 slip angle sign convention. This is nice for oval racers because the slip angles will always be positive in the turns. For road racers I suppose it doesn't matter which way is which.

Ok, I think that about does it. Have fun.

Todd I actually started testing that as soon as you posted. I took some telemetry from mine and a couple DWC people for the F1 car on the NTM. Would it be accurate to have 10deg slip on the front tires nearly every corner, while having up to 11deg on the rears in some corners? Personally I think it's a bit high but I don't know F1 tires at all.