I have a dream... Scawen mails me a development version of this sim and all the physics tools, for me to see how the tyres are modelled and to observe current data... Then being able to apply changes and test them out. Sadly I tend to wake up before I lock my brakes... illepall oooerrr..

I'd say LFS would benifit if a handfull of people get to tweak the physics parameters / curves. I doubt Scawen is handing out the 'stuff' though

That seems like a terrible idea to me

Yeah, other developers could get somewhat close if they would see Scawens code

One of the things that visiting professor Todd Wasson has often said, is that real tyres do not have much significant grip drop-off after the peak. Far less than people really expect. So this behaviour isnt really that suprising.

Also bear in mind the effect of brake balance. Lets say for the sake of argument that a locked tyre generates 95% of the force of a perfectly threshold braked tyre.

When you lock up all 4 wheels, they will each generate 95% grip and your overall braking force will be 95% of maximum.

Now lets say you try and threshold brake. If you are using a typical kind of setup, your brake balance will be a bit forward, and your fronts will be runnning at a higher slip ration to the rears.
So maybe you get 99% of theoretical maximum on the fronts, but the rears are probably only generating 70-80% of their theoretical maximum.

Now obviously the load on the fronts is probably double that of the rears, so the effect of this is not as dramatic is it sounds but it probably brings the average force back down to the same sort of range as the locked tyres.

Quote from colcob :

When you lock up all 4 wheels, they will each generate 95% grip and your overall braking force will be 95% of maximum.

As I recall, Todd said it was close to 80%.

Quote from Forbin :

Also known as high-siding, when the rear end steps out then suddenly grips.

http://www.youtube.com/watch?v=CCkhAq9rztQ

@fonny: im not a biker really but when you watch high-siding youll see that when rear slides the bike brakes(folds? bents? sry my english), the angle of the rear changes and so the contact patch resulting getting grip back (unluckily - lateral) - hey, youre into air!

@AndRand: I'm not so sure the contact patch changes at all. In the video I posted, you can see that in the initial slide, the bike's lean angle is constant. The bike just starts to yaw a bit, and when the slip angle reaches a critical point, the tire generates a massive lateral force.

This usually results in an imediate highside, but in this case, due to the skill of the rider involved (or just pure luck), the rear wheel is realigned to the direction of travel. However, as a result of inertia, the rear wheel overcorrects and generates a lateral force in the opposite direction. This results in the rear wheel getting launched into the air and the complete loss of any control that may have been present after the initial slide.

Quote from Forbin :

@AndRand: I'm not so sure the contact patch changes at all. In the video I posted, you can see that in the initial slide, the bike's lean angle is constant. The bike just starts to yaw a bit, and when the slip angle reaches a critical point, the tire generates a massive lateral force.

i predict change of contact patch with every change of wheel lean. rear one changes its lean during slide getting more grip to the critical point and then, agreed, happens the latter.
i see it like that but i can be wrong, as i said im not biker, though id like to experience everything just to the critical point

Quote from RIP2004 :

(can a mod change the title in the forum itself? Longitudinal instead of Lateral)
A car with locked wheels should use a significantly longer way to stop, than a car which brakes with spinning wheels. (at least on tarmac. In snow and in sand its a different matter ...)

Little off-topic:
Strange as it seems, but for example, on dry-tarmac car stops earlier when wheels are totaly locked compared to ABS braking...maybe due to unefficient ABS system...No-ABS situation: physics say spinning friction is higher than sliding friction, so braking with "spinning wheels" should be better (no shit )...

Not entirely sure but you might be able to draw a reasonable grip / slip curve if you start with high brake force in the car setup, perhaps with a 100% front bias, then brake 100% .. it will lock up.. then reduce brake strength until you start to not quite lock up.. With the telemetry program I think you can find the stop distance and wheelspin etc? Changing the available brake torque in small steps should be more accurate than trying to brake at the optimum 'manually'?

From what I've read in SAE literature and been told by Doug Milliken, with motorcycle tires the design goal is to produce lateral force with camber rather than slip angle. At a certain lean angle/camber angle on a given bike there is a certain amount of lateral force that will hold the bike nice and stable. One paper I read called it a "perfect turn" or something like that. I.e., if the bike is leaning at 45 degrees it will need to corner at 1g. 60 degrees is 1.73g, etc.. (It's just the tangent of the angle in trigonometry).

So what they try to do is design the tire so it will produce the amount of force to turn the bike at 1 or 1.73g or whatever purely by camber. If you do it with camber only then you don't require any slip angle at all. That's a good thing because any slip angle causes some drag which slows you down.

Granted, I doubt any tire does this perfectly at all cambers and so on. Plus, once you start using brakes/throttle things are bound to change so you'll end up with some slip angle anyway most likely.

Quote from Niels Heusinkveld :

Not entirely sure but you might be able to draw a reasonable grip / slip curve if you start with high brake force in the car setup, perhaps with a 100% front bias, then brake 100% .. it will lock up.. then reduce brake strength until you start to not quite lock up.. With the telemetry program I think you can find the stop distance and wheelspin etc? Changing the available brake torque in small steps should be more accurate than trying to brake at the optimum 'manually'?

Sorry for the late answer. Have been on holiday.

You're right. It's a better method to test it and there are differences. I think more interessting is the acceleration ( http://www.lfsforum.net/showthread.php?t=7840 )

There is a difference but it doesn't make the same difference as in RL racing.