I got rid of the spare and the support brackets on my real Caterham SV (1300lb car, 250hp 4 cylinder 2.3 liter Ford Duratec engine):

caterham pics

I have a new web host now, but the link remains the same (see below). There are racing game videos, racing game mods (mostly getting rid of icons on replays, savegames, and some radio control related videos and links, such a rc glider dynamic soaring at 301mph.

http://jeffareid.net

How do we know that any actual tire data was used for the tire physics as implemented in LFS? I know this is hard to find, but Avon does provide such information, and there are also some good sources concerning tire physics and simulating it on the web.

I thought they put ice on the rear tires of the LX6...

Quote from Woz :

Yep, tire scrub sounds earlier would help a bucket load as you would get that early warning but not sure how simple that would be as it depends on the tire model and how it is coded.

Base the sounds on slip angle, and for throttle / brake usage, base it on slip ratio. The slip ratio sound may be a bit unrealistic if it kicks in well below the limits, but there isn't any other reasonable means of feedback.

Both.

I own a Caterham SV with a 2.3 liter Ford Duratech with about 250hp. This is the first car I've ever experienced lift throttle oversteer with (however the car recovered very quickly, much quicker than my heartrate did). Recovery seems much easier than it does in LFS, but as posted, it's because you can feel the rear end getting loose much sooner than you can with LFS. One thing that would help would be for tire scrub sounds to occur further below the limits than they do now with LFS. In a real car, you can hear scrub sounds well below the limits of traction (at slower speeds where wind noise doesn't block out the sounds).

Quote from Bob Smith :

Well, I tried your set, and I wouldn't really call it easy to drive, it's just pig understeer at every corner. OK so it doesn't spin so easily, but you couldn't actually use a set like that for anything other than "this set doesn't spin much".

As someone else posted, reducing front camber (which I did) seems to help. Regarding my understeery setup, on the skid pad the sustained g-forces while cornering remain about the same.

Did you see more than a 1 second per lap difference between the two setups? My issue is I'm just not that fast with LFS, my Blackwood times are barely under 1:25. You're probably a lot faster.

Regarding setups, you can try edgars wr setup.

LX6_bl1_Edgar748.set

How about Nordschleife and Isle of Mann?

Anyway, all of this is getting a bit off topic. I'm trying to understand why some LFS cars like the LX6 reacts so severely when the rear end gets a bit loose. I tried using the setup parameters so if the LX6 is sliding sideways, the front end has less grip than the rear. In addition to sway bars maxed at front and zero at rear, I had to also mess with the camber settings to get the result I wanted. The net result is a LX6 that is a lot easier to drive, but I don't understand why it takes such an extreme setup to get it to behave itself.

If you want to try it out, here's the test setup I created for Blackwood:

http://jeffareid.net/lfss2/LX6_bl1_jeffr.set

Quote from sinbad :

Even the new lap-record holding Radical SR8 was using road-tyres, they claimed they could have taken 30 seconds off their 6:55 laptime if they had used slicks).

True, but Dunlop Direnzas are a lot stickier than "road supers". Apparently this run was done on a Radical with the SVA option. Note that the only tires specified for Radicals are slicks. For street tires, you're on your own.

http://www.cgimotorsports.com/radical_info.html

Note that Dunlop Direnza are probably the softest "street legal" compound tire you can get, from this link in reference to Berkins, another Lotus 7 replica maker. I don't know if the Direnza 02G is what the Radicals use, since the downforce puts more of a load on the tire than a 1200 lb Lotus 7 replica does.

http://www.prbaustralia.com.au/Newsletter%20APRMAY05.PDF

Yokohama A032—good all-rounder, good road mileage and competent track tyre

Toyo R888—as for Yoko A032, but better value for money, but squarer profile may touch front guards

Avon CR500—premium soft road tyre, rain pattern, expensive

Dunlop Direnza 02G—excellent soft road tyre, excellent for supersprints but get too hot after continuous laps

Avon ACB10—probably the fastest road-legal tyre, crossply, very soft, expensive

Regarding the SR8 record run, if that car could really run 30 seconds faster with slicks, then why not an attempt with an all race SR8 to break the all time record of 6:11 set by Stefan Bellof back in 1983 with his Group C Porsche 956 during practice?

Last edited by JeffR, Mon 31 Oct 2005, 04:16.

Although the Avon CR500 is specified for most of the "Caterham" classes run by Catrerham themselves, most club racing classes with tire restrictions use the Avon ACB10, a racing compound tire, or they use slicks if there aren't any tire restrictions. As previously posted, most USA SCCA racing classes, that have tire restrictions, just require a DOT approved tire, which translates into a racing compound tire with treads, like the Avon ACB10. Many classes in the SCCA have no tire restrictions other than the tire must have a proper speed rating, so slicks are used in these classes. Note that the ACB10 is the "Roadsport A control tire".

Regarding the Caterham runs at Nordschleife, I wasn't referring to the offical production car class runs, just the lap record runs made by some club racers. I don't know what official orginization defines what a production class car is, or what such a car can run with on the Nordschleife. My guess is a racing compound tire with treads if there are tire restirctions.

A Caterham "production car" is a tough call, since you can order one with "Avon Caterham Slicks". Edit: sine production class is supposed to be street legal, then the Avon ACB10 was probably used. These are stickier tires than the CR500's or LFS's road supers.

LFS doesn't have the equivalent of a racing compound DOT (street legal) tire.

Last edited by JeffR, Mon 31 Oct 2005, 04:08.

Quote from Bob Smith :

OK, so take this example:
Your rear brakes loose in the GTT for example, and you have to pile on loads of opposite lock to stop the car from spinning. You put on just enough lock to stop the car from spinning, but not enough to reel the rear back in. So you're now pulling a huge powerslide (some call it drifting, I'm sure there's some subtle difference in definition, but anyway). But you're not going to spin. And the rear isn't coming back into line. So slip angles must be equal and you've still got lots of lock on.

In this case, the rear slip angles are much higher than front slip angles. You see this all the time at drift events, rally events, and dirt track events. There's no rule that states slip angles have to be the same to prevent a car from rotating (yaw rate) faster or slower than it needs to in order to take a turn.

In the case of donuts, you can have the inside front barely moving at all, virtually no slip angle, while the rear tires have a huge slip angle, as in the second half of this video:

http://home.att.net/~b.a.porter/burnout.wmv

Last edited by JeffR, Mon 31 Oct 2005, 01:54.

I thought of a good example regarding slip angles.

Take the case of a car moving forwards on a steeply banked straight. The actual path direction vectors for both the front and rear of a car are parallel: their directions are identical front and rear. Yet the car will have an overall yaw angle, pointed slightly up slope on the banked section of track.

In order for slip angles to be the same front and rear, the steering has to be centered.

I prefer a steering input based definition for understeer versus oversteer. Maybe new terms are needed.

Steering understeer - as the amount of bank of the straight is increased, it takes more steering input to keep the car going straight.

Neutral steering - as the amount of bank of the straight is increased, it takes the same steering input to keep the car going straight.

Steering oversteer - as the amount of bank of the straight is increased, it takes less steering input to keep the car going straight.

Steering critical oversteer - as the amount of bank of the straight is increased, the steering wheel approaches being centered.

Quote from Bob Smith :

If the car begins to oversteer, slip angles must be larger at the rear.

I'm talking about what happens after a car stabilizes into a fixed yaw angle while turning. Think of this as the slip angle for the entire car. The car is pointed inwards relative to the direction it's actually traveling while turning.

My impression was that the only way for all 4 tires to have the same slip angle while turning is for the steering wheel to be centered when turning (and no ackerman effects at the front). In LFS, this can be setup with the LX6 with slicks, via the slick mod, with near equal front and rear sway bar settings (I couldn't get this to work with the road supers as they are too unstable).

However what I left out is the rate or rotation of the car as it turns. The car is yawing in the direction of the turn while it is turning. This means the front end is moving inwards, and the rear end is moving outwards relative to the center of rotation of a car in a turn. However, relative to the path of the car, both the front and rear end of a car are moving inwards.

I've found some web sites with questionable diagrams of slip angles when explaining understeer / oversteer, such at this one:

http://www.autozine.org/techni ... dling/tech_handling_4.htm

The issue is that the diagram shows the front slip angle as inwards versus straight ahead, and rear slip angle as straight ahead versus outwards, for the neutral and oversteer cases. Based on these diagrams, the implied path of the front end of the car is the same as the direction that the car is pointed in, for both the neutral and the oversteer case, while at the same time, the implied path at the rear end of the car is outwards.

Obviously, there is no slip angle at the rear end of a car unless the rear end of a car is yawed inwards relative to it's path. Assuming the car isn't hinged in the middle the entire car is yawed inwards at the same angle. This is pretty obvious in the case of tires with large slip angles, similated in games like GPL or GTL.

Last edited by JeffR, Sun 30 Oct 2005, 13:10.

Regarding the slip angle versus lateral force (grip), here's a link that describes the differences between radials and bias ply racing tires, along with a graph. I think the radial curve dropts off steeper than it does in real life for racinc radials.

tire_info.htm

If LFS doesn't allow slicks for all cars, then it should at least allow DOT racing tires, which are typically bias ply, and provide grip aroung 1.2 to 1.3g's, right between the road supers and slicks of LFS, but with the stability of the slicks, because they are usually bias bly. In real life, most racing classes permit the use of the equivalent of a DOT racing tire. (In the USA, DOT just means that the tire is street legal).

Another link including a graph comparing slip angle versus lateral force versus normal force. Note that at low normal force, the curves lost almost no grip when beyond optimal slip angle. These curves are for racing radials. Bias ply slicks have much less or no loss in grip at fairly high slip angles.

http://www.smithees-racetech.com.au/ackerman.html

Last edited by JeffR, Sun 30 Oct 2005, 12:23.

Quote from Breizh :

Those slicks you tested on the LX6 were R2s or R1s?

I've tried both.

Quote from Tweaker :

Errrm how do we know what kind of tires are modelled in LFS?

Road Supers on the LX6 produce a sustained (versus temporary peak) max cornering force of about 1.15g's. In LFS, the road supers are more unstable than the slicks, I assume that this is LFS's idea of how a radial based street tire behaves.

Slicks on the LX6 (via slick mod) prodcuce about 1.4g's of cornering force, a tad less than real racing slicks, but close enough. They are more stable than the road supers, and my assumption is this is LFS's ides of how bias ply racing slicks react.

Quote from sinbad :

Caterham classes - only the top cars with 260 bhp run slick/cut-slick tyres. The others all use road-tyres, from 100bhp beginner classes in which the tyres are intended to last all season, through to 200bhp

This is ignoring the fact that a significant portion of Caterham racing is in 2 liter class, not Caterham specific, and most of these are done with slicks.

Caterham specific classe were changed in 2005 (no superlight R500 classes). I don't see a class for their R500 superlight anymore. As posted most of these classes are oriented towards the lower powered cars, and generally allow the CR500 tires. Note that Caterham describes this tire as an all weather racing tire, not as a road tire.

I suspect that most European club racing by Caterham owners doesn't involve the Catheham UK sponsored racing, more more of the equivalent of the SCCA in the USA.

I can guarantee that all the lap record runs by Caterhams at Nordschleife were done using slicks.

In SCCA racing. almost all classes allow DOT racing tires, or slicks. You can scan this document to see what is allowed:


2005GeneralCompetitionRules.pdf

Even though most racing classes for modified road cars (and even stock road cars) allow at least DOT racing tires, if not slicks, LFS doesn't include either.

Last edited by JeffR, Sun 30 Oct 2005, 11:18.

Quote from thisnameistaken :

I still think that if you made it a server option most people would want the slicks (the "easy" tyres), so server admins would enable the slicks, and you'd never see the road tyres again.

If this is what the buyers of LFS S2 want, then why not give it to them? I don't think slicks are "easy" tires, unless the road supers are improperly implemented, or they are deliberatly implemented to be less stable. With slicks, braking distances are shorter, requiring more driver accuracy for braking points.

With a few exceptions, almost every racing class allows DOT tires to be used. For lighter cars, this translates into about 1.2 to 1.3g's of cornering force, and the tires handle more like slicks than road supers. LFS doesn't have such a tire model, but this would be a nice addition.

Line: 10 - No matter where my car is, it's always on some line.

Consitency: 10 - every lap time is different, now that's consistent.

Racecraft: 10 - I've mangaged to turn every opponent car into a braking or cornering assist.

Quote from sinbad :

As long as there's a real-world reason for something being as it is, I don't mind, hence why I don't mind the current LX cars having high-performance road-tyres.

But in the real world, LX owners have the option of running with slicks, and many do.

It's not a biggy for me, with all the games out just now, I don't play any of them online much, and there's already a slick mode for LFS S2. However other players here are wanting to race the LX6 online with slicks, and I agree with them and offer supporting reaons for doing so, so far to no avail.

Maybe I'm a bit touchy on this one, becaue of a similar problem with Need For Speed Porsche Unleashed. In the car file, NFS5.CAR, one of the race cars, the 550, didn't have any tires at all in its list of available parts, an obvious bug and the only car with this bug. The parts file, NFS5.PRT had 3 types of tires specifically for the 550, normal, rain, slicks. With a missing key part, the game defaulted to a standard tire. The fix was simple, and could be done via a savegame without changing any acutal game files, but some vocal opponents claimed they didnt' want any non EA changes even though the game was abandonware by then. So this meant the entire online community was stuck with a race car that didn't have slicks, because of opposition from a small, but vocal group. (Note that all other cars in NFS Porsche Unleashed have slicks as a tire option, from the 1950 356 to the 2000 turbo, only the obvious bug in the NFS5.CAR file prevented the 550 from having any tires at all).

Quote from tristancliffe :

Also, I don't think saying the LX6 should be like the brand new CSR, especially as it's only just been released, but the LX6 has been in LFS for two years...

and so has the superlight 500, a 4 cylinder with 230hp.

Quote :

Please don't turn this into another my names JeffR...

Please note that I didn't start this thread. Several players would like slicks for all cars, a few more would like slicks on the LX6. None of this has anything to do with actually owning a seven replica, just the fact that seven replicas are supposed to be track cars, and unlike street cars, they are designed to run with slicks.

Quote :

Road cars, like LX's should have road tyres.

Most people don't consider LX's to be road cars, most consider them to be track cars that are street legal. This is also the way the cars are marketed. How many road cars weigh less than 1200 lbs, consider a heater and windshield (instead of windscreen) as options, and don't offer air conditioning, a radio, cruise control, abs, or a lot of other things you find as an option on most road cars.

If there ever was an LX8, it should get the same engine as the Radical SR8, which is composed of two Hayabusa 1.3 liter motorcycle heads paired up to a common crankcase to create a V8. 350hp.

A Radical SR8 just recently ran a 6:55 lap at Nordschleife.

Then again, a Radical SR8 would be a cool car for LFS.