There are frequent complaints about dangerous drivers on the servers. I am curious to know what other people define as "safe racing". For instance, in a one hour race with 20 drivers what would you consider an acceptable number of loss-of-control incidents (spins or all 4 wheels off the track)? A total of 20, an average of one for each driver? How about contact with other cars which causes that car damage, or loss of control? Would more than a total of 5 such collisions be classified as a crash-fest? What are your opinions?

I see three problems with the RAC design:
1) It appears that the tires are the same size on the front and rear. But there is 50% more weight on the back and the rear tires have to handle all that power. Using different air pressures can help but it would be better if the tire size fit the amount of work that the tire had to do.

2) As mentioned in a previous post, no rear ant-roll bar. This limits the ability to independently adjust the vehicles vertical spring rate, roll spring rate, and fore and aft distribution of roll stiffness.

3) The rear suspension design. If you compare the rear upright of the RAC to the other cars in LFS, it is the only one with the upper attach point so far outboard of the lower one. This is probably done to raise the rear roll center. Maybe an effort to increase the rear roll stiffness without increasing the rear spring rates. As a result, the rear wheel cambers change a lot more than they do for the front wheels. Plus, it tends to have the "jacking" effect of a car with swing axles.

Based on these three factors I think the front of the car is much more efficient than the rear. Usually increasing the front roll stiffness will ease the load on the rear tires at the expense of over working the outside front tire. Therefore making the feel more balanced. I haven't been able to do this with the RAC. Either the frame is too flexible to transfer the roll moment to the front, or there just isn't that much weight that can be transferred at the front, or I am doing it all wrong. So I have tried something that they did on the Auto Union GP cars back in the 1930's when they had lots of power and narrow tires. They would put positive camber on the front wheels to make the car lose grip at the front more easily. Thus, when the driver lost the back end of the car it was easier to catch because the front tires were already closer to their limits. What seems best to me is (a) setting the live camber settings at the front to between 0 and -1. (b) Setting the live rear cambers to between -3 and -4. And (c) raising the ride height of the front of the car to make the initial roll centers more equal for the front and rear. The tire temperature profile for the front tires looks terrible with these settings (outside edge about 5C hotter than inside edge) but I find the car to be much more controllable and easier to save when the back end breaks loose. In fact, I am now trying to dial out some of the understeer in slow corners without losing the stability it has. Lap times ( at least for a slow driver like me) don't seem to be that far off what I can do in the LX6. After all, if you can't use all the extra grip at the front, it really isn't going to be of much help.

But everyone has different abilities and preferences on how they want a car to feel. Just something that works for me and might or might not be of help to someone else. By the way, I really like the car.

Quote from hp999 :

And I love how someone with 18 posts moans about RAC.

Well, I am glad I made you happy but I don't think I said whether I like the car or not. I just asked what other people thought. Besides, my number of posts has nothing to do with my number of years spent sim racing and modding the physics in GPL cars.

I would like to try some of those "decent" and "proper" setups. The ones I have tried so far either have uncontrollable oversteer from the start or have understeer right up the the point the back end slides away never to be recovered.

Are there any fans of this car? Detractors?

Quote from AeoIus :

I agree with everything said here, but for me personally I find the RWD cars in LFS too difficult to control.

In LFS I'm well able to race in all FWD and 4WD cars, but seem unable to race correctly in the RWD cars. They seem too slippery to me and I cannot consequently race them without losing them at some corner, even the low powered cars or maybe especially even the low powered cars.

The XRG is probably one of the harder cars to drive because of the low amount of stiffness in the tires. But if you keep increasing the air pressure in the tires then the handling becomes more stable but with less grip and slower lap times. And when choosing between speed or stability most people choose speed so stable setups are hard to find. If you try the XRT with normal tires and use restrictor settings to get the same power to weight ratio as the XRG, then you will find the cars handle much better even though the coefficient of friction is about the same.

Try starting with lots of understeer and low power and work your way towards faster setups.

I left iRacing before the hosted races started. How has that worked out? Did it reduce the number of people doing the public races as some people said it would? Was there an obvious increase in membership that could be attributed to the availability of hosted races/leagues?

I think legoflamb is on the right track when he suggests something like iRacing's Safety Rating. People aren't much different than dogs when it comes to doing things for which they are rewarded and not doing things for which they get punished. Most LFS servers reward risky driving. Going as fast as you can and trying to make the spectacular pass is rewarded with excitement and once in awhile it even works. When it doesn't a driver can just vote for a restart, wait for the next quick race, or go to another server. There is no long term down side.

But I know people who quit iRacing because they didn't like having to drive in a more restrained style. It just wasn't fun for them. Learning to do something that requires good judgment, discipline, as well as good reflexes is something that is more of a long term satisfaction, not the instant fun that some people want in a game.

I definitely would like to see some type of safety rating in which a driver is punished by having to use a restrictor plate if he had a bad rating or having servers be able to limit access only to drivers who have a good rating.

I wonder if the importance of the sidewalls of the tire are given enough study. All the loads on the wheel rim come from the tension and shear loads in the sidewalls. The sidewalls pull up on the contact patch and, therefore, have a lot to do with the pressure distribution across the contact patch, the shape of the contact patch, and which parts are sliding and which aren't. Under lateral load the leaning of the sidewalls steer the tread/belt of the tire and determine the slip angle. With the empirical approach all this is hidden in the curves but, with a physical approach, I would think that this is as important as the lateral bending of the tread belt.

I received an email from iRacing inviting me to renew my subscription. Have they added any new tracks to the basic content in the last 6 months? Is the basic road course package still:

LRP
Summit
Lowes
Laguna Seca

I bought the Skippy but that is all the content I had on my first try. Just based on what I already have is there any reason to give it another try? Any updates or physics changes to the above content that might change my mind about the value of the game? (Not interested in hosted races or special painting options, by the way.)

Currently I have to replay a practice session in fast forward and write down the times if I want to get my lap times for all the laps in the session. Is there a program that will generate a file from the replay with this information?

I looked at the LFS Stats thread and evidently it does not work with the newer versions of LFS.

What kind of team are you looking for? Gentleman's racing club
Age: 65
Country: USA
Preferred Car/Track: Anything but FO8, F1 and ovals
Average Laptime on Your Preferred Car/Track: Best lap times are between AI Quick and Pro times using same setups, depending are car and circuit.
How Active Are You?: About 10 hours a week.
What Kind of Control do you use?: G25 wheel
Time Zone: CST (GMT -6); Available between UTC 1400 to UTC 0300

Drove GPL for the last 11 years. My philosophy is to stay on the track and see how fast I can go, rather than go as fast as I can and see how long I can stay on the track. Looking for other drivers who take realistic racing serious but don't take winning serious.

This is not meant to start a LFS vs. iRacing argument, I would just like a comparison of the two in regards to aero downforce. When I was subscribing to iRacing I didn't buy any of the downforce cars because I didn't think I would enjoy them. The management of the weight transfer of a car under dynamic loads is one of the things that I like best about driving. For example, there are a couple of turns at Aston Club at which the track has a little hill in the middle of them so that one has to make adjustments as the car first presses down on the track and then gets light after the hump. This a bit of the a challenge in cars like the LX6 whereas, in the FO8, the changes in elevation are hardly noticeable because of the aero downforce. In the winged cars, because of the downforce and stiff springs, I don't experience as much the weight transfer under braking, acceleration and cornering loads. My question to those who have tried the winged cars in iRacing (I don't count the Skip Barber 2000 in this group because there doesn't seem to have much downforce), do you consider the formula cars in LFS to be a good representation of what downforce feels like or do you think I would have come to a different conclusion if I had tried the aero cars in iRacing?

Quote from Wm. Peddle :

What in hell is the problem with some drivers?
Do they not realize that the driver ahead of them may have to break early, because the driver ahead of them has to break early when ever the corners get bunched?

I think the problem is that a lot of people don't understand the "field compression" effect that occurs at turn one. If the whole field takes off at the same time, and accelerates at the same rate, then the field arrives at turn one with the same spacing as it was on the grid. The problem is that the lead car gets to his braking point first. If you have 20 cars, and the grid spacing is 10 meters, then the 20th car is still 190 meters from his braking point when the leading car hits his brakes. It will be another 4 or 5 seconds before the last guy gets to his braking point while everyone in front of him is slowing down. Plus the first lap braking point will be earlier because the tires are cold and the cars have to go through turn one slower because they are usually side-be-side with other cars. The drivers at the back of the grid are less likely to be aware of this. If everyone applied the brakes at the same time as the lead car, and then continued to brake until they reached their cornering speed, then the compression would not occur. But the the cars behind the lead cars would reach their cornering speed before they reached the corner and would have to continue at part throttle until they reached the turn. And that is the problem. Anyone braking early and staying behind the driver in front of them becomes a sitting duck for the drivers that qualified behind him. All those drivers who were slow in qualifying take advantage of the situation to do what they couldn't do based on talent by taking advantage of the safe driving of those ahead of them. This results, at best, in cars being three or four wide going into turn one or the back markers running into the back of the cars ahead because openings closed up before they could get to the openings.

Some leagues I have been in have tried to make rules such as no overtaking before the apex of the first turn but people still seemed to get carried away with their enthusiasm. HS (Human Stupidity) makes AI, flawed as it may be, a better option for me.

Quote from Falcon77 :

As somebody already explained before, all other things being equal, overall grip determines body roll and not the other way around
With the same ride height you cannot have more grip with "less roll", or more precisely: less weight transfer. If you lower the ride height though, you *might* end up very near the current lap times..

I agree with your statement. Scawen's post was a little too general to permit one to come to a conclusion about what he meant(comments in brackets are mine):

"...we found that we could not make the LFS model handle as well as the real car[too slow?, too unstable?]. One of the reasons for this was that the LFS tyres had too much grip [generated too much lateral load for a given vertical load?, to high a coefficient of friction?, individually or all together?] and this was causing the inside wheels to lose too much load [again, vertical or lateral?] while cornering. But simply reducing the grip would not have been a good approach... the result would have been just the same old LFS but at lower speeds [but if you had too much lateral load being created, the speeds would be too high to begin with]."

But I am happy with the present model so any improvement will be a bonus.

Quote from Turbo Dad :

Makes a huge difference

It certainly does! Now instead hearing the skid and thinking, "Darn, I've flat spotted my tires!", I can hear them getting ready to lock and ease up. It is brilliant the way they have implemented the sounds except it defeats the purpose when they are so quiet they can't be heard. A bit like painting a masterpiece and then hanging it with the picture facing the wall. I wonder how many people have tried the demo and have given up because of this?

Thanks for the download. On further investigation it appears that what I was looking for is there ... but it isn't loud enough to be heard. I tried replacing the road noise files with the horn sound. The road noise starts at 20 km/hr. The second sound at 0.60 G (for the LX4). The third at 0.85 G. The fourth at 1.03 G and the last at 1.10 G. The problem is that I can't hear the first three at all even with the skid sounds at max. I wish the tire noise on my road car was that quiet! I have to turn the radio up when I get to 100 km/hr. (Of course, it is a Chevrolet. ) Maybe I'll just tape a recorder to my fender well and go do some parking lot driving to get those rubber grinding on pavement sounds I want.

First of all, I am very impressed with LFS and the quality and number of features that it has. The engine sounds are great and the first time I heard the echos coming off the buildings I was stunned. Dirt on the tires, localized heating are all great. However, it seems to me they are missing a bit on the tire sounds. They seem very simplistic and don't convey as much information as they could. It appears you get tire squeal when the tires start to slide that increases in volume the more you slide. But this all occurs after the slide begins. Tires make all kinds of sounds before they even reach the limit. They make a scrubbing sound that gradually gets louder as they are put under more stress. Then they start to squal which gets louder as they approach the limit and then transition into a screech as they go past their limit.

LFS appears to have primarily one frequency that only changes volume. (If there are other sounds I can't hear them and I have the car sounds down and the tire noise at max.) Coming over from iRacing this is one thing that is a big difference in the two sims. iRacing gives a much better indication of where the tire is on the slip angle curve using audio information. They use a variation of sound type, frequency, and volume to give the information that you would get physically if you could feel the inertial forces. And I think that LFS already has the code for doing this. The force view with its different colored vectors with varying lengths could be adapted for audio. Substitute sound/frequency for color and volume for vector length and you have a good start on a superb audio feedback system for the tires/inertia. And I don't think it would hurt to cheat on the level of sound because, after all, we don't have the realism of feeling the inertia forces.

Quote from Bob Smith :

Is the drop really from the tyre losing vertical spring rate though, as I would expect the side deflection to be similar to turning a square into a parallelogram (for a very crude analogy), which would automatically create some reduction in sidewall height (if not length).

I think you are correct that if the tread moves to the side then the sidewall has to extend (less bulge) or the bead will have to move down to keep the same distance to the tread. But if you define spring rate as the load divided by the distance that it deflects then wouldn't it work out to be the same thing as a reduction in vertical spring rate? If not technically then at least in practice? Also, think of standing a broom straight up and pushing down as compared to leaning the broom over at an angle and pushing down vertically (not along the broom handle).

If anybody has any wisdom to offer on tire theory please jump in because I need all the help I can get. Of course, if people are interested it might need to be a separate thread.

I drove GPL for the past eleven years but made the mistake of trying iRacing. The iRacing tire model has that little something that lets you know how hard the car is working to hang on to the track. At some point you can sense that the tires are really being given all they can take and you had better be careful. Whether you are at 50%, 100%, or over the limit at 110% iRacing has a different feel for each case rather than just gliding over the track surface at different rates of speed with the same feel. The latter is the way GPL now feels to me. I would put the present LFS tire model about half way between the two. I really hope that LFS has tried iRacing and notice what I am referring to.

I am not sure what causes this. I have written a tire analysis program that attempts to calculate the loads and the shape of the tire sidewalls in order to get a better feel for what happens to a tire under stress. The program seems to give reasonable results for vertical load as far as spring rate and contact patch size but the lateral load case is flexing too much. Even so, there seems to be a cross coupling effect between vertical load and side load. A side load reduces the vertical spring rate of the tires and increased vertical load increases the side deflection. So if you apply a side load to a tire the wheel will tend to settle closer to the track surface. If the tire loses side grip then the side deformation will decrease and the tire will try to push the wheel up causing a sudden increase in vertical load as the tire tries to jack the car back up where it would normally be for less side load. With added vertical force it would seem that the tire would momentarily regain grip and the process would then repeat itself. This may be the source of that little chirp-chirp sound you get as you reach the limit as apposed to the constant squeal sound that occurs below the limit.

If anyone (Bob Smith ?) knows of a good source of information for sidewall behavior would you please post it. I can find loads of stuff on contact patch stuff but that is mainly about grip. The sidewalls are what really count for spring rate and feel. At least that is my opinion.

I have read the Manual and Bob Smith's setup guide but couldn't find an explanation for the teal green vertical lines in the suspension diagram that go with the setup page. My guess is that it is the direction the contact patch will move as it deflects up (that is, the perpendicular to the roll center).

As an engineer I enjoy all the data that LFS displays both in the setups and in the Force view. However, would it be possible to add the vertical spring rate of the tires to the information shown? The tire spring rate becomes quite significant with modern race cars and their super stiff suspension systems.

I've had eleven years with GPL and the last three months in iRacing. I have had more fun with LFS in the last four days than I did in the whole time at iRacing. I tried LFS about 4 years ago and was not impressed with the demo, but I am having a blast with it now. I can't believe it is being programmed by just one man. Very well done, in my opinion. If the tire model update makes it even better than it is now I don't think LFS needs to worry about iRacing.