Based on the article I linked to, for cars which don't have pre-measured inertia values provided by the manufacturer they probably have a basic equation that uses all the known masses and weight distribution, and the resulting inertia value is refined by comparing it to the inertia and masses of those vehicles for which they have accurately measured data.

Quote from Liff :

Based on the article I linked to, for cars which don't have pre-measured inertia values provided by the manufacturer they probably have a basic equation that uses all the known masses and weight distribution, and the resulting inertia value is refined by comparing it to the inertia and masses of those vehicles for which they have accurately measured data.

Which might be how they've claimed to have done it, but they must've cocked up their calculations somewhere.. Just don't seem right at all to me. Thanks for pointing the article out though by the way.

Guess they just put out a fix containing a tire compound tweak for the Corvette, will be interesting to see what they changed.

Edit: Ian Berwick(from iRacing) says: "it's going to be a very minor adjustment to the tires. They should feel pretty much the same, but they should be SLIGHTLY more forgiving. Grant can feel the difference.... I'm not good enough to feel it, but slides are a bit more "catch-able" "

Quote from DaveWS :

If you want to test this for yourself I'll explain. Basically take any iRacing car, say the Mazda, to the skid pad as it loads quickly and is completely flat.
[...]
Now try in the Skippy. You should find that the natural side to side motion the car naturally falls in is much slower. Why is that? Does the Skippy have significantly higher rotational inertia IRL than the Mazda?

Moment of inertia is only one factor. The other is the torque, which in this case (polar rotation) is generated by the tyres. The car having much more grip (Mazda) may also more easily generate bigger difference in lateral forces of front and rear tires (assuming 50/50 weight static weight distribution for simplicity so that these forces have approximately the same arm relative to CoM of the car) and as a result bigger torque causing the rotation. With similar polar moment of inertia to Skippy, Mazda should be able to change its orientation much more quickly.

http://www.nessoft.com/ispeed/

very elegant solution for an external hud for iracing

I dig it

Quote from DaveWS :

Compare with other sims if you want.

I think this is the best way to do it! How does it compare to the C6.R in rFactor? What about the GTR class in LFS?

DaveWS - I'd have thought, if anything, most racing games/sims guess numbers that are too high for the moment of inertia tensor. LFS takes the generation approach, since such numbers are not easily measured, so they should be quite reasonable, and can dynamically change with passengers, fuel and mass handicap. Also, any sim only take 3 numbers it not fully modelling inertia, as simultaneous pitch and roll should be different to pitch followed by roll.

Quote from MKR :

Is your name Will Power?

How would you know what a real high downforce, open wheel, slick tyre race car feels like when pushed to the limit.

I do.

I don't play iRacing, as it didn't feel right to me either. I will admit (as I have done before, and will do again) that I haven't played it in a while though! Maybe the time has come to see if it's got any better.

Slightly pleased as well that they've acknowledged the graphics look silly. I've tried mentioning before how fake it looks, but apparently I've been wrong until now.

P.S. Since when was a Barber a high downforce car?

He's talking about the IndyCar at Barber Motorsports Park, Tristan, rather than the Skip Barber car.

Oh

Quote from Gnomie :

I think this is the best way to do it! How does it compare to the C6.R in rFactor? What about the GTR class in LFS?

Well both the GTR class in LFS and the C6R in rFactor feel more weighty and generally seem like there is more rotational inertia compared to iRacing, and you have more time to react to what the car / tyres are doing. Of course rFactor feels pretty numb and the tyres aren't great either, but as we know it hasn't got the best physics engine in the world nor the best modders bar some. In LFS the tyres allow for driving past the peak slip angles without losing out on laptime too much, and sometimes in fact gaining time. I'm pretty sure though that the new tyre model improvements on the horizon will feel much much better, and punish over aggressive driving more.

Quote from Bob Smith :

DaveWS - I'd have thought, if anything, most racing games/sims guess numbers that are too high for the moment of inertia tensor. LFS takes the generation approach, since such numbers are not easily measured, so they should be quite reasonable, and can dynamically change with passengers, fuel and mass handicap. Also, any sim only take 3 numbers it not fully modelling inertia, as simultaneous pitch and roll should be different to pitch followed by roll.

Presumably iRacing doesn't full into the category of too high. LFS feels just about right regarding the general weight and feel (bar how the tyres feel). Interesting how simultaneous pitch and roll might differ, my understanding of physics starts to be stretched here...

Quote from tristancliffe :

Maybe the time has come to see if it's got any better.

Do it! It's a little cheaper now, and I'm getting fed up with the fanboys over there who keep telling me I'm wrong and it's all perfect etc. Make sure you try the Formula Mazda out or the Dallara IndyCar cos those are the ones which feel too snappy to me (once you get rid of the understeer).

*hovers mouse pointer over buy button*

Quote from spanks :

http://www.nessoft.com/ispeed/

I dig it

I dig it too.
Might be tempted to find a cheapo monitor so i can finally use a HUD with split times. (the old thud never worked for me as i had softth)

Will Tristan be tempted over to the dark side? Find in tomorrows edition of 'LFS forum'.


edit: iR down for maintenance Grrr

Well, I've paid for it. And I've bought the Mazda single seater thingy, plus Silverstone.

I have a scary feeling that I might not be able to drive them yet though, until I've upped my unrealistic Safety Rating thingy. I do hope I'm wrong and I can play with what I've just bought. Edit: Not bought. Leased. My mistake.

you have to be D class 4.0 to race the mazda against other people unless its a hosted server, i think. but that wont take long.

Quote from tristancliffe :

Well, I've paid for it. And I've bought the Mazda single seater thingy, plus Silverstone.

I have a scary feeling that I might not be able to drive them yet though, until I've upped my unrealistic Safety Rating thingy. I do hope I'm wrong and I can play with what I've just bought. Edit: Not bought. Leased. My mistake.

Looking forward to hearing what you think. You can test any car and track in "test" mode offline. To race them online like Gabkicks says you need a certain safety rating. As much as I despise the safety rating system myself you can get up to the rating you need to race the Mazda with others online quite quickly since you now get promoted to the next license instantly when you meet the requirements. You'll need to fulfill the MPR requirements (4 races I think in a rookie car) as well as driving without picking up incidents.

The "FastTrack" promotion system is temporarily disabled due to some database issue they were having. They said they're working on a fix for it.

Dave I'm not sure if I can really agree with you. I've been silently reading and contemplating what you've been saying, but I'm just not seeing it.

The Dallara doesn't really display any of the handling characteristics that the old mazda did. I don't think I have snap spun once. The slides are also pretty savable. I don't even find it twitchy

I'm using volker's set and have gotten down to a low 12 at Barber so I am driving it plenty hard to know what it actually handles like.

Also...brace yourself for this one guys...Richard Towler actually likes the Dallara. I think hell has frozen over.

UncleBenny did you ever post your thoughts on the corvette?

Recorded a 1:12.6 lap around Barber with Dallara Indycar.
Not very clean one, but the clock likes it
http://www.youtube.com/watch?v=G0ae33msMw8

As for handling, it can be snappy if you provoke it with fresh tires but once you're past the sweetspot, it gets much more tame as the tires start to wear out.

Quote from spanks :

The Dallara doesn't really display any of the handling characteristics that the old mazda did. I don't think I have snap spun once. The slides are also pretty savable. I don't even find it twitchy

Do you think you could post (zip I guess) a replay of you driving the Dallara with a particularly loose setup to demonstrate? I have had many "correct once = snap the other way at 1000 mph into a barrier" moments like in the Mazda. I'll post a quick replay of a particularly bad one at mosport when I get home (30 mins or so). No doubt I'll get told I'm overcorrecting etc.

Very nice lap Crommi, are you using Volkers setup? It's always front grip limited as can be seen in your lap, you never once have to correct for oversteer, it's on rails. GP4 anyone? /me runs

Quote from DaveWS :

Very nice lap Crommi, are you using Volkers setup? It's always front grip limited as can be seen in your lap, you never once have to correct for oversteer, it's on rails. GP4 anyone? /me runs

I used Volker's set as a base to get idea on how to make the car fast. Made some changes to it, especially increased bump gap which made the car feel bit more agile and added front wing for fast corners. But overall it feels pretty good for my driving style as I don't like oversteery cars in general. There's really not much sliding, usually getting bit of a 4wd drift into T1 and little bit of wheelspin on the inside tire coming out of last corner, but letting the car hit rev limiter kills it quickly.

I don't really like the idea of running negative bump stop gap, makes the front feel really weird through fast corners and it's not really realistic to have suspension compressed that way on a standstill.

Quote from DaveWS :

Very nice lap Crommi, are you using Volkers setup? It's always front grip limited as can be seen in your lap, you never once have to correct for oversteer, it's on rails. GP4 anyone? /me runs

Sounds like you should try a front grip limited setup

Joking aside, I honestly don't feel the same about the Dallara... and boy I was one of the biggest Mazda haters out there; I tried to get into that car time after time after time, but it never felt right.

It's quite different in the Dallara! The limit can be felt much better than in the old Mazda (haven't spent more than a lap in the newly updated Mazda, so I can't judge the updated tyre model) but it's just a b*tch once you try to step over the limit. For me, it drives the way I expect a top level openwheeler to drive. You never really see slides (even little ones!) during real Indycar races either, but you see plenty of spins - I think there's quite a big truth to the way in which the car reacts to being overdriven in iRacing, however I'm not claiming it's perfect.

Crommi there was an excellent discussion about bumpstop gap and what a negative number really means on the forums.

There was the guy who made the indy car participating in the discussion.

He was saying that their bumpstop material is actually quite a soft material and a negative number should not be seen as a solid suspension. The bump stop is acting like another spring when it starts to get compressed ramping up the spring rate as it goes further into the negative. Having a negative bumpstop or zero bumpstop gap on this car just means that it is touching or slightly compressed and will get stiffer as it is compressed harder.

In the future he said that we'd have the option to choose the durometer of the bump stops lol...more setup options

Dave I'll throw some laps together tonight if I have time. I'm off to campus at the moment and have a substantial amount of solid works to get done before tomorrow. I should have saved some replays from last night...

Don't get me wrong, I do crash kind of frequently. It is kind of how I learn a track...110% and eventually I string a lap together. It is frustrating and sometimes boring but I actually crash more trying to go slowly lol. I just can't really recall any times that I actually had to countersteer and it shot off in the other direction.

At least the Dallara isn't as bad as the Mazda I guess. Here is a particularly violent snap I had in the Mazda at Mosport, during my first few laps around there. (It's just a 10 second cut)

I might give the Dallara another go sometime tonight, maybe some more setup work (increasing the bump stop gaps perhaps at the front to get rid of the understeer) and it'll start to work for me, despite *cough* the inertia issues I still believe the car has.

Download everything. Install everything. Update everything. And then the "Member Site" is down or something. Meh