Right, just like the experts who have researched and concluded that CO2 is the cause of a global warming trend :rolleyes:
There's plenty of widely accepted BS in the world.
edit: Well said JTBo, your english is fine.
Until someone comes up with a reason why they think that the cliff-curves could ever be correct, it's common sense and reasoning to know that they're a myth. Todd has explained personally observed behaviour and physical reasons for his hypothesis; AND the working out of his theories have good results. I enjoy GTR2 from time to time still, but do you really think a car's behaviour is even remotely accurate around the limit? That just irritates me, anyone that thinks so has just plain never driven anything, probably not even a lawnmower.
Another reason that cars spin is because they run of out of lock, don't apply the lock fast enough, or don't reduce the lock quick enough once the car corrects itself.
Jtbo s explaind it very well for a english language noob like me but sorry Shotglass i can t understand the sense of your question even with translator
Could you maybe say it in german,would be a lot easier for me.
if you mean a moment who you could catch the slide with countersteering?
Yes,but it s a uncommon question since it s pretty logical just because of the weight transfer.Maybe it s no the explaination but it s only my feeling in this case.
But i m happy with Jtbo s post and most of all (you,BBT,jw..)others who posted here.It really brings me too change old certitudes i had bout this.
When sliding and pushing more accelerator, in rFactor with curves that have dropoff grip is completely lost in such situation, even pushing accelerator should just settle car a bit.
Of course if there is too much throttle applied sideways grip is sacrificed too much, but with those dropoff curves countersteering does not help at all as slip angles go to no grip area very easy.
Potentially, part of the problem is that seat of the pants "feel" from experience was used to create these graphs. As the tire breaks away and starts producing less grip because of a slide, it will feel like the the tire just broke loose in a very abrupt manner. The tire has not broken loose in an abrupt manner, but the g load in the car will change abruptly going from a constant 1g lateral (in a constant speed corner) to something much less than 1. This is going to feel like you went from tarmac to ice when you haven't.
I think it is very similar to the misconception that if you go from tarmac to wet grass, the car actually speeds up. Well it doesn't. Your rate of deceleration decreases giving you the feeling of acceleration. (I know, deceleration is just negative acceleration, but using the deceleration term is easier to understand)
I think a lot of those graphs in those books were derived from bias ply tires and with cars with much less advanced suspension systems than we currently use. It is possible that those cars with those tires behave very differently than what a more modern setup will behave.
Also, people may equate tires to something like a solid heavy object on a smooth surface (picture a square block of metal). You push and push on the object, and once you get it moving, it slides along pretty nicely. Try that with a rubber block. With enough force, you will get it moving, but it is not going to just start sliding along nicely once it is moving.
Anyway, sorry for the long post. That is just my way of thinking about this subject.
When the tires slide, it is because the force pushing the tire sideways is greater then the resistance. Unless you continue applying the sideways force, the tire will be slowed down. But all of this has little to do with the rolling friction of the tire. Your rear tires sliding is basically the same as a tire locking up.
Actually, there is no such thing as deceleration or negative acceleration. There is only acceleration.
I have driven alot of Road Cars and Formula cars on and over the limit and I do think the amount of Grip in LFS is quite good.
What has been mentioned before is quite true, that with the common field of view most are using, the sense of speed is not coming across. If you drive in your car and take both hands to cover what you see at the sides, and only look at a small portion of the view in front, like you do in LFS, you get the impression that your going much slower than you do.
That leads to corners beeing taken to fast and the impression that the car has to low Grip.
Choxaway, an included Replay in your opening Post would have been nice, you could take the car on a lap at the limit, then post the Replay and say at which corners you would expect the car to have more Grip. Because then, when reviewing and analysing the drive one can take a better look at the speeds and the amount of steering.
I have driven a Lotus Caterham the type of car you mentioned in your opening Post, I would consider the amount of Grip in the LX4 pretty accurate, not perfect by any means but not very far off.
the "break away" point at the top of these graphs is not a sudden loss of traction. The graphs I have seen are curves. Tires have an optimum slip angle (turning) and slip percentage (straightline). This angle or percentage is the top point on the graph. If you go beyond this point, it is not sudden death, it's just slower.
Think about accelerating from the starting line. You want some wheel spin, but not too much. If you try not to spin the tires at all (0% slip), you accelerate slowly. If you spin them too much, you go just as slow.(Same with braking - between lock-up and under-braking)
When turning in LFS, if you don't hear tire scrub, the tires are not at their optimum slip angle. If you are turning too hard or too fast, the tires will start screeching. They are not at their optimum slip angle and you will go slower.
Tires only have so much traction, and the when you exceed their maximum traction, they have less grip (not zero grip).
Wow, I wrote more than I wanted to. oh well. This is very complicated, especially when you factor in accelerating or braking while conering.
oh, one more thing, since we're talking about books, one book i recommend for everyone who likes driving and racing is "Going Faster! Mastering the Art of Race Driving". It's very informative and helpful. I've written too much already, so i'm not going to write a book review here, too. look it up on google. (This page lists all the chapters, etc.: http://www.themotorbookstore.com/gofamaartofr.html)
And at the highest slip angles it's 67%. I'd call that a cliff.
The only tire data I've seen that drops off significantly after the peak in slip angle on dry surfaces are big truck tires. They tend to have very large tread blocks that can do all sorts of nasty things at high slip angles which probably explains it to some extent, but in car tires this just isn't the case. Inadequate torsional stiffness in the belts might have something to do with it too, although that's pure speculation on my part and not based on any data.
In the wet there is usually quite a large drop off in both car and truck tires, but even a truck tire in the rain doesn't drop off as much as GTR/GTR2's racing slicks do in the dry. Longitudinal grip (acceleration/braking) usually does drop off at high slip ratios, but again, not generally clear down to 67% of the peak value.
Here's some data that is an exception to the rule, but again, these are giant bus tires (see page 24):
Even these big guys don't really show much of a drop off in lateral grip with slip angle (page 23). In some situations, even in the wet, the grip just keeps climbing slowly "after the peak" rather than falling off. Anyway, these are more along the lines of what you're driving in GTR/GTR2/rFactor, at least in terms of longitudinal slip. They're more like big bus tires in the rain with extra traction than any car tire I've ever heard of. This is precisely why when you countersteer just a little bit after hanging the back out a touch, the car, instead of straightening up or slowing down its rotation, just spins faster. Your real car would do that too if that's how the curves looked. It doesn't because the real curves don't look like that. That should be a dead giveaway but most developers miss it
A friend of mine and I did indeed encounter this in a light pickup truck in the rain once. We went a little too quick through a corner, the tail came out a little, he countersteered nice and smoothly, and the truck just accelerated around more quickly as he steered and wound up pointing backwards. Thankfully we slowed down quite a bit before hitting the little tree, sending the back of my head through the window behind us which exploded into a million pieces But anyway, that's a pickup truck tire in the rain, not a car tire or racing slick in the dry. Big difference!
Here's a paper written by a friend of mine (Milliken, author of "Race Car Vehicle Dynamics):
Dr. Kasprzak, Doug Milliken, and I attended an SAE conference together last October and had quite an interesting talk or two about tires. They are involved in a lot of tire testing (they have their own library of tire data that I'd kill to get my hands on) and definitely know their stuff. These are the guys that teach racing engineers in Nascar and so on what they didn't know they didn't know about vehicle dynamics and tires. Their paper there shows some real tire data that goes quite a bit past the peak force slip angle. See figures 6 and 8. Even the longitudinal curves didn't drop on these tires, at least out to whatever slip ratio the measurements were run to. This is somewhat uncommon from my understanding, but has been known to happen with some tires provided they aren't smoking hot from wheel spin/lock.
For those curious, figure 12 shows tire pressure effects :eclipseeh
Subjectively speaking about grip loss after the peak, I suspect we get as much or more of our feeling about what the car is doing from not just the acceleration, but also "jerk," the derivitive of acceleration. "Jerk" is to acceleration as acceleration is to velocity, or velocity is to position. It's how quickly acceleration is changing. E.g., at time 0 acceleration is 0g, at time 0.25 it's 0.5g, at time 0.5 it's 1g. The acceleration is changing 2g/second. That's jerk.
When cornering you feel the 0.5g or 1g, but you also feel how quickly the acceleration is rising. In the case of a set of car tires that peak at 1g, you have positive "jerk" as you're on your way up to that 1g, but before you hit it and the curve starts rolling off into the peak, the "jerk" changes and eventually becomes 0 as you finally hit that 1g. To our rear ends this feels very much like there's been a sudden loss in traction, but there doesn't need to be any loss at all in order to get this impression. It's a bit like sliding sideways into the grass. The acceleration drops considerably extremely quicly (very high negative jerk). Many people swear their cars actually speed up when they hit the grass, which of course is not the case, but our "jerk meter" seems wired into all of this and produces that sensation. That's my theory anyway
A jerk curve would essentially be the slope of the lateral force vs. slip angle curve. Drivers' descriptions of how one tire feels very forgiving while another one feels like it loses grip abruptly seem to match this concept. If the force curves rise and then very gingerly roll off into the peak at 12-15 degrees slip angle, the jerk curve is low and the driver feels that the tire is very forgiving and easy to drive. Switch to an F1 tire that peaks at 4 degrees slip, where the force rises very rapidly and then very quickly rolls off into the peak, and the driver will say that the tire is very snappy, tricky to drive, and more importantly, he might say that the tires lose grip very quickly, even if the force is actually totally flat after the peak. The jerk is considerably larger (not the jerk driver, the jerk = derivitive of acceleration ).
To be fair though Todd, the GTR2 tyre file slip angle vs lateral force curves go out to 120° or so. At a more reasonable high slip angle, say 45°, the lateral force is still around 93% of peak.
Also, I don't think it's clear how the curves in the tyre files are actually used by the ISI physics engine(s). There are a handful of modifiers that are used to scale, shift and transform the curves as a function of load, pressure, temperature, etc. At the end of the day, the initial curves might not be particularly meaningful. For example, as a test, I tried setting one of the slip angle vs lateral force curves to a flat line at 1.00, leaving the other tyre parameters the same; the in-game results were not significantly different than using the original unmodified tyre file. I think parameters like LatPeak, LoadSens, DryLatLong and DropoffFunction are much more important in determining the actual values used by the game than the raw data in the curve table itself.
Then again, what do I know? The ISI tyre files are a mystery.
Hi George,
I agree with your point concerning restricted views - it's also a bit like looking forward through a zoom lens on a camera whereby the foreshortened image totally eliminates a true sense of speed, whereas the same camera at its wide angle setting will dramatically increase that feeling of speed - something I notice a lot when viewing TV footage of a race from the camera mounted on the driver's helmet. In order to take in a wider FOV, the tiny camera's set at quite a wide angle and the car appears to travel much faster as a result.
I found that altering my FOV to about 60 gave me a more natural - or should I say equivalent to a real - driving view forward and sense of speed but as you say, it's like wearing blinkers and the speed sensation is thus reduced. It's only since setting up my TIRPro enabling me to look about me as I would in reality, thus removing the blinkers but still in the correct driving position in the car, that I found a much happier state of affairs where I can judge my speeds and anticipate corners in a more realistic manner. With a virtual driver in place, when I look around I can see 'my' shoulders where they should be and I'm not located too far forward or back in the virtual seat. The huge advantage of TIR3 is that I can quickly glance round, sit higher or crouch down a bit, lean left or right slightly as though anticipating centrifugal force, albeit not actually there, in much the same way as if driving a real car.
I wish I had one of those rumble seats (someone raving about these in the flight sim forums) whereby the force feedback that I enjoy with my M/Soft FFB2 wheel and pedals is similarly transmitted to the seat and gives the flyer (or in this case driver) feedback from the virtual wheels. Maybe the vibration coming back from the road surface might impart some sense of weight to the cars and sideways momentum when turning hence the old 'flying by the seat of your pants' expression.
One problem when approaching corners is that when braking there's no feeling of weight beneath your body or being forced sideways by gravity etc, which may well be why I initially had so much difficulty feeling my way around the track. I still think the Caterham-types appear underweight and skittish, when I would have thought their body weight or mass would, in conjunction with their low height, wide tracking and fat wheels, give them more grip on the bends - particularly being dry weather.
Likewise, come out of a bend too fast and when the back starts to go, I would normally counter this with a touch of opposite steer but do that in these cars and they take on a life of their own swinging back and forth until a total spin results. I seriously believe decent tyres on such fat wheels wouldn't react so violently but it's only my impression, never having raced the real thing.
As to your first point, having only just bought the game, I had no idea I could keep the playbacks and access them other than immediately after a race, how long they remain recorded and stored - and where to gain access to them again another day.
How replays are saved depends a bit on how you set up LFS, but this section of the LFS Manual explains it quite nicely.
Once the setup is saved ingame, you can go to "<LFS install dir>/data/spr" for single player replays (respectively to "<LFS install dir>/data/mpr" for multiplayer ones), find the replay in question and attach it to a post here in the forum. To do that, first click on "new reply" like you normally do, scroll down a bit to the "Additional Options" and there you find a button named "Manage Attachments". That opens a popup window in which you can browse to the replay you located earlier and upload it to the forums by pressing the "upload" button. Once this is done, you can close the popup and continue writing your post as normal.
Doug wrote back and said the tire type and data on pressures must have been proprietary since they weren't included in the paper, so that can't be made public. Sorry!
I don't have the files handy at the moment so can't double check, but it seemed to me they dropped very much more rapidly than this. I could be mistaken though.
Most likely, LatPeak shifts the curve to the right as load is increased. However, at any given load there is a peak and some point after that where the force drops to 67% of that peak. LoadSens is load sensitivity, another modifier that varies friction coefficient with load. With this too, however, you have a peak and some point after that where the force drops to 67% of the value. DryLatLong is another multiplier. Same thing there though. There's 100% at one point and 67% at another. I'm not sure what DropoffFunction does, but I very much doubt it fixes anything up.
I don't think there's any magic stuff going on there. When driving it I can immediately tell that the force curves drop off quite a lot after the peak in all of ISI's sims that I've tried, with the exception of the Mustang and perhaps a couple of other cars in GTL. It's easy to tell. Kick the car a bit sideways going into a corner and you'll slide right off the outside of the curve where if you were running at the peaks you would have rather easily made it. Try countersteering a little bit (not tons of lock) and you'll see the cars spin faster than if you left the steering alone or steered into the spin instead. If steering into the spin = easy spin correction then the curves definitely are dropping quite a bit.
Take a look at this replay of hannu's world record hotlap at Blackwood. Save it into lfs directory/data/spr, then load up LFS, load the replay and watch it from the in car camera.
Notice the cornering speeds which can be achieved with good balancing of the car with countersteering and smooth throttle usage. Now replicate it yourself.
Seriously though, it takes A LOT OF PRACTICE to be that fast, but it is doable, just keep at it.
Here's a screengrab of the GTR2 Michelin M3 GTR tyre file in Dave Purdy's Physics Editor. http://i17.tinypic.com/5ybsgh3.jpg The y-axis is lateral force (normalized to a peak value of 1.0), the x-axis is slip angle (measured in steps where each step is 0.009 radians). The max value along the x-axis is 236 steps which corresponds to 2.124 radians or 121.7°. The peak normalized lateral force occurs at step 11 which corresponds to a slip angle of 0.099 radians or 5.7°. At a slip angle of 45° (0.785 radians, step 87) the normalized lateral force is 92.8% of the peak.
So, while the curves do drop off to 60-70% of peak this only happens at extremely high slip angles that likely will not occur in-game. For the range of slip angles that are likely to occur, the curves remain in the 90+% range throughout.
I'm not arguing for the accuracy of the tyres in ISI-based sims, by the way. They largely feel strange to me too.
Incidentally, for a bit of fun I tried using Niels' C6 Corvette tyre files with the M3 GTR in GTR2. It was sliding all over the track - lots of fun!
but sorry Shotglass i can t understand the sense of your question even with translator 
This is precisely why when you countersteer just a little bit after hanging the back out a touch, the car, instead of straightening up or slowing down its rotation, just spins faster. Your real car would do that too if that's how the curves looked. It doesn't because the real curves don't look like that. That should be a dead giveaway but most developers miss it 
