What Tristan and rjm said.

It's funny, because I just noticed this recently. I've been away from LFS for about a year, and just started getting some seat time in again. Obviously, the stock setups that I had made me a moving chicane, so I procured some "better" setups from kindly fellow racers. Immediately, my lap times came down significantly.

I still wasn't keeping up with the faster folks, so I started twiddling copies of the setups I'd just received. The first thing I noticed was how extreme the camber settings were. The inconsistent heat across the tire after ten laps was pretty incredible. The outsides of the tires never got anywhere near optimal operating temperature, whereas the insides came up quickly and never really got so hot that they became greasy.

I spent a couple of hours making more reasonable setups, but as others have said, there is rarely a race over 5 laps, let alone ten. My inclination is to say that there's an error somewhere in the tire model, but I have no way to defend that position

It might simply be that LFS's tire model is more camber-dependent than you might expect. You get better results from simply keeping the tire level mid-corner than you do by keeping the tire temps relatively even.

Quote from Forbin :

It might simply be that LFS's tire model is more-camber dependent than you might expect. You get better results from simply keeping the tire level mid-corner than you do by keeping the tire temps relatively even.

I was under the possible misapprehension that the two went hand-in-hand. It seems like every setup guide begins with instructions to drive laps and adjust camber until the tire temps are even across each tire.

When I got to a point where this was the case, the dynamic camber numbers seemed appropriate. On the one I was working on last night, my lap times came down pretty consistently. At least until I started mucking with settings that are less measurable (at least at my experience level) -- like track bar settings.

So I started looking at the dynamic camber settings for a "reality check", instead of the static numbers on the left. What are the differences between these two values in the Garage?

The static camber numbers are just there as an adjustment. As far as I can tell, they're purely arbitrary. The live settings are all you should be looking at. Just make sure you drop the car before checking any changes. The tire will flex and resist the camber change (at least a little) until you do so.

What I mean by keeping the tire level is keeping the vertical load across the tire (inner, middle, outer) even. However, under this condition, the load on the outer part of the tire only meets or exceeds the load on the inner part under maximum cornering force. As a result, the outside doesn't heat up nearly as much as the inside. In order to get even temps (at least in LFS), you need to allow the outside to load up quite a bit (through the use of less camber), and doing so sacrifices grip.

I'm not too sure what to add to this thread. Much can be learned about how LFS's camber, tire temperature, pressure, and resulting grip work from running on the skidpad. I do quite a bit of this actually whenever running a car I've barely touched (that's my "new content," right there )

Camber adjustments for skidpad tests were done with the Shift-L suspension display on. This shows camber while actually cornering. What's noticeable is that the peak lateral grip comes in when camber is 0 on the Shift-L display. I.e., when camber is actually 0 at the moment relative to the road. This is what I call "dynamic camber" rather than the camber shown in the setup screens for "live camber," which to me is just "camber." In the setup screen this means adding in a lot of camber adjustment because the suspension geometry on all the cars I've tried lack enough camber gain to handle this (they all need shorter upper arms, pretty much).

Tire pressure has a noteable effect on dynamic camber (shift-L while cornering, although watching the 3 pressure bars on each outside tire in the F9 display as Forbin describes is the same thing) in LFS as the body roll angle changes. Lowering the tire pressure softens that corner of the car and increases body roll, so any time tire pressure is adjusted you ought to adjust camber too. This is something I didn't notice until playing with the LX4 in a frantic attempt to get within 4 seconds of Axus' lap times recently.

A reasonably safe conclusion is that in LFS these high cambers work in short races because the dynamic camber (shift-L while at max cornering) is close to 0, which gives the highest lateral acceleration and cornering speed. I'm not sure how the temperature distribution across the tire in LFS effects grip though, as you can't test that separately without throwing camber into the mix. My impression is that the average temperature across it is used, or something close to it, but I could easily be wrong there.

This works just fine on the skidpad, but on a track the tires heat up unevenly so much on the straights that you of course wind up with a really uneven distribution. What exactly the tradeoff is there in LFS I couldn't say. But I sure have fun trying to figure it out! This heating split on the straights seems overdone in LFS though.

In longer races, if you don't really notice much difference in grip when you have a really hot edge and really cool edge develop so long as the average temperature across the width stays about where the optimum temperature is, then you can probably be safe setting up the car to keep the average temperature at the optimum and not worry too much about the spread. I always until just recently assumed that having the temperature distribution equal and right on the optimum temperature was the way to go in LFS, but it seems that it's more important to have the pressure distribution even mid-corner. Ah, the joys of car setup

If this is the case, the pressure distribution then effects grip more than the temperature distribution, so it might be a good idea to set up the car to put the average temperature across the width right at optimum (just the middle temp is good enough, probably, unless tire pressures are exceedingly low or high). The end result is usually quite a lot of camber. Granted, this hurts your braking a bit, but the trade off is probably usually worth it.

Overall though, having -3 deg or more "live camber" isn't unusual at the racing track in reality, so I wouldn't let the number bother me. In reality, tires make peak lateral grip at some non 0 "dynamic camber" angle, often -3 deg or more. The front right tires in one racing class at a nearby (very) short oval track running street tires were running probably over -12 degrees. Road cars aren't set up this way because of tire wear and durability, primarily, where most driving is at 0.3g lateral or less. Most of the time you're going straight.

Another good thread! I autox my car, and I have spent some time talking to Frank Secondary, the guy who designed the Kumho V710s we run. We've chatted about tire temps and camber quite a bit and the conclusion we've usually come to is that it's far from an exact science, he knows the theory, but he doesn't have the answers, and that you just have to test and do what works. This pretty much fits in with what you've mentioned you've tried on the skidpad, Todd. For autox, Frank suggested that for the road cars most of us are running, more camber is almost always a good thing. Most of us run 2-3 degrees and he said we could go more than that (assuming our cars are not camber limited...with stock ride height I can't get more than 1 at the front and 2 at the back on my car!). There is little concern with losing braking performance because so much of it is cornering and transitions in autox of course. The main thing I got from chatting with him is that you just need to test things and do what works.

Quote from jtw62074 :

In reality, tires make peak lateral grip at some non 0 "dynamic camber" angle, often -3 deg or more.

Do you know why this would be? That's unintuitive. (but then what part of tire physics IS intuitive! :razz

So really then; LFS's crazy camber's arent even as crazy as they could be IRL then, based on this statement... Also based on what you said, I presume that the uneven heating in LFS isn't due to camber values that are too high, but rather possibly inaccurate heating on the straights - which makes it seem like the camber is to blame when in fact the tires have lateral grip peaks at dynamic values that are too high as it is...

Interesting.

Quote from Ball Bearing Turbo :

Do you know why this would be? That's unintuitive. (but then what part of tire physics IS intuitive! :razz

It is intuitive BTW. Whilst the outside tire is cornering, it is subjected to both severe vertical and lateral loads. Since tires aren't exactly stiff wooden blocks, the tread block(s) (depending on whether tit's a slick or treaded tire) are deflected to the inside of the corner. The final result is that the pressure distribution over the contact patch becomes uneven when cornering at the limit with 0 relative camber to the road because the tread blocks actually deflect, causing uneven pressure over. The extra negative camber compensates for this tread block deflection, allowing more even pressure loading across the contact patch.

Just read my explanation and with a bit of imagination one can easily figure this out.

I'm not positive but I think with the current tire flex model, LFS already simulates that.

EDIT: No, I take that back. The load bars in the F9 view correlate pretty much exactly with camber. That is to say, when camber is 0 (as seen in the Ctrl-L view), the load bars are even.

EDIT2: Actually, if you look at the Shift-L view, you will notice that the wheel itself is still cambered negatively quite a bit relative to the bar that represents the track, even when the camber of the outside tire reads +1. I would have to assume then that LFS is telling you the camber of the tire patch, not the wheel.

No, it's not intuitive that less surface area in contact with the road could make more grip. Due to load sensitivity, putting even more load on the side of the tire where it's slightly deflected to shouldn't help. It would not allow "more even pressure loading", it should be the opposite as far as I can tell... Perhaps your explanation is poor, or just to condescending to convey your idea?

I think Todd is talking about the wheel's camber. In order to get equal load across the tire, the wheel's camber has to stay negative as explained by post above with LFS used as an example. If the wheel is flat (0 camber) under high cornering stress, the contact patch flexes inward. This effectively puts more load on the outside of the tire. To counteract that, you need more camber, which effectively makes the contact patch's camber more even (closer to 0 instead of highly positive)

Quote from Forbin :

I think Todd is talking about the wheel's camber. In order to get equal load across the tire, the wheel's camber has to stay negative as explained by post above with LFS used as an example. If the wheel is flat (0 camber) under high cornering stress, the contact patch flexes inward. This effectively puts more load on the outside of the tire. To counteract that, you need more camber, which effectively makes the contact patch's camber more even (closer to 0 instead of highly positive)

By having your wheel camber more negative then the road, this compensates for tread deflection, so the actual thread contact area is greater and the vertical and lateral loads more evenly spread. Thus, more even pressure distribution.

It is not just area that affects load sensitivity. Pressure distribution is the real factor here, though it is related to area on the ground too. and no I have no intention of being condescending. People seem to be misunderstanding me a lot these days. I am just helping you to visualize tire behavior better by encouraging the use of imagination.

Remember, we are trying to get the tread to 0 degree camber relative to the road, not the wheel. To understand this better, just play around with a wide racing style, low profile, soft and hollow (non-pressurized air filled) remote control car tire tire that you can easily load with your hand. As you vertically and laterally load the tire simultaneously, note that zero wheel camber actually forces the inside edges of the tread block(s) to lift off the ground as they flex under the lateral load. In real cars, this easily shows up as more temperature on the outside tread block(s) then the inside since the inside is actually experiencing less pressure. This condition is easily remedied by adding just a few extra degrees of negative camber relative to the ground, so we end up with the individual tread blocks square to the road for ultimate pressure distribution.

And yes, Forbin's explanation is actually quite good and straightforward, though it misses out a bit on the subtleties of what really happens. Just try my suggested experiment and you can easily see that Forbin and I are absolutely right on this.

Hope this helps. If not just say so politely and I am OK with trying to explain this better.

Quote from Forbin :

Actually, if you look at the Shift-L view, you will notice that the wheel itself is still cambered negatively quite a bit relative to the bar that represents the track, even when the camber of the outside tire reads +1. I would have to assume then that LFS is telling you the camber of the tire patch, not the wheel.

interesting ... i wasnt aware of that but it seems like its in fact true (while being incorrect)
either that or the wheels camber drawn in shift-l is very exaggerated

Or the diagram rotates with road camber, yet ignores it for wheel camber (i.e. zero camber at wheel might be drawn at 5° if there is 5° road camber).

nope the road camber seems to be drawn into the diag via the inclination of the grey line
the green one appears to be up in car coordinates

Great post, Todd (post #30). I was using "dynamic camber" because I couldn't remember what it was called on the setup screen. The term "live camber" is what I meant. I also just learned you can watch the dynamic camber through the Shift-L or F9(?) layovers during a replay. I was watching the tire temps and trying to watch dynamic camber in the F9 screen the old fashioned way -- while driving