I've got an air horn on my car because I'm not allowed to cut people up on the road, and when other people do it to me, I like to register my displeasure at something approaching 140db in two tones designed to instill fear into other road users.

On the track, you can cut people up all week, and people call it great racing... and they have a right to do the same to you if they're fast enough and have the control.

So why would you need a horn? I'd take mine out to save weight on the track!

I change pads and rotors over at the same time.

Ideally yes, that and a reventon. But LFS doesn't and won't have licensed cars. So I'd like them to come up with something comparable in driving physics! (and make it look effing great, in their own way.)

Better stop listening to Tristan then!

Seriously though, anyone fancy giving bridgestone a bell and seeing if they want send you a graph combining latitudinal and longitudinal multidimensional graphs?

I'm out of my depth here, I am a driver, but I am not a good mathmatician. I'm also exhausting from work today, aching like a corpse from being on the kart track for an hour an 15 minutes yesterday (the track has one straight, roughly 2 seconds long... and many, many corners).

I thought the traction circle simple pointed out how close to the maximum g-forces attainable by the car a drive is getting over the course of a turn or sequence of turns. Opporating at the cars lateral force limit would mean using the slip angles that generate the most grip, irrespective of where they fall on a graph, there could be a massive drop off after 11 degrees, right down to almost nothing, but if you are at the edge of the traction circle you'd be avoiding using those kinda slip angles?

Could anyone else clarify the correctness of what axus is trying to point out?

Last edited by z3r0c00l, Sat, 10 Nov 2007 20:58.

I've already explained this further up the thread -

they can't show original graphs and measurements because the tyres companies will never let them publish them, and the only people who can afford the blindingly expensive tyre testing equipment such as the Bridgestone MTS Flat-Trac LTR tire test system.

They closest they were allowed to come was best fit superimpositions.

The capabilities of the Flat-Trac allow plus or minus:

30 degree slip angle
10 degree inclination
road speeds of 200mph
lateral forces of plus or minus 6,744lbs
the same amount of vertical load
aligning torque for plus or minus 2,213lbs
longitudinal force of 4,496lbs
490hp net drive power


Second to that, what is wrong with taking information from racing drivers as to how a car feels when driving it? I personally would love to drive a racing sim that racing drivers say "feels right", irrespective of the means by which that happens.

Last edited by z3r0c00l, Sat, 10 Nov 2007 20:44.

Shotglass - check the first pic I've attatched, that's what I was trying to articulate from memory, but I've got a proper version to look at now. As for the nova video - examples are hard to find so I took the best one I could find, you try putting anything to do with tyre physics into youtube! :P

I found another graph - its pretty self explanatory.

I note a 7psi increase from 33psi having gone in on understeer and out on oversteer for about 8 minutes. Whatever that means.

I don't think anyone dare deny the fact that SUVs have a higher center of gravity.

Anything that has a higher center of gravity will be more prone to body roll(especially with soft, off-roadable suspension) and roll-over for a given speed and steering input and tyres with a given level of grip.

Of course it was a massive sweeping statement, they're called "the laws of physics". An ye canny change the laws of physics jim!

Tyres are so complicated in their behavior that there is no such thing as "off-topic".

Have you people ever heard of the term "it's so tight, it's loose" used before?

I don't think the fall off in traction with slip angle is pronounced enough for radial tyres because this behavior seems missing, kind of nulled out.

The effect I'm describing is when you understeer into a corner at the limit of effective slip angle, and then due to a surface change or steering input, going past the slip angle, when grip rapidly falls off, this brings the rear tyres up to optimum slip angle as they experience more lateral force as the fronts start letting go more.

the problem comes when you come back down the slip angles at the front assuming you made the corner, at which point you have to correct ultra fast as the front tyres snap back into their prime biting slip level...

I get the impression this is far less pronounced in LFS as it is in real life, although it could just be down to me having a naff wheel without 720 degrees of lock. Looks kinda like this:
http://www.youtube.com/watch?v=RuBlF6Aa8dc - I didn't think anyone in a nova could drive this well!



I had this happen in my car, and promptly tank slapped into what I've started calling "a minor off", because it sounds better than "parking off road" (my previous term) and much better than "I crashed into a ditch". (That'll teach me to think I'm the freakin' stig and turn off the DSC - http://www.youtube.com/watch?v=ncE-Vk7egRo)

Last edited by z3r0c00l, Fri, 9 Nov 2007 11:46.

you suck at graphics? blimey.

I'm not interesting in racing anything where the tires are designed grip badly. They make SUV tires knobbly even for road use, because they roll over too easy if you put sticky performance tires on.

I mixed up the camber sensitivities for cross-ply and radial tires. My bad.

I'm going to have a leaf through over dinner for any more useful and interesting information. I'm looking through at the moment a section on abrasion. (especially in the case where cold tires are pushed beyond the limits of grip. Interesting stuff.


There is a section on tire load sensitivities. This is important, because tires, in their massive complexity, don't produce grip linearly with load.

From personal experience, driving reasonable road tires at 235/40/18, 32psi, and dicking around, and well past the limits of traction, I'd say the tires snap back sooner. I'd say LFS's physics are spot on for wet roads, with the traction multiplied up a bit, if you get me. But I am by no means any authority.

Ok so this is the book:

http://insideracingtechnology.com/booktiredescrptn.htm

(didn't want to post the title here because google will index it and associate it with those images)

The tyre is inferred to be a modern Radial tyre, one of the more expensive street ones, it is "low profile", the tread pattern is street legal in america. That's about as much as they'll give away, apparently the tyre industries biggest product is secrecy!! Pressure at "recommended", so probably around 30 psi. Tyre width of around 235 going by other examples.

The reason these daigrams are all a "bit textbooky" is that they were not allowed to paste actual test results from the test facilities because that would give away a lot to the "enemy". So they've traced over them, and ditched the names, lol.

"Radial tyres are better because they have a stiffer, flatter contact patch, and there are higher restoring forces at lower values of lateral tread distortion, which translates to smaller slip angles for the same lateral force as bias ply tires. Smaller slip angles in turn mean less drag, and less heat."

We should chuck some bias ply's on the UF1 - not as sensitive to camber, and plenty of warning at break away so easy to drive at the limit - perfect for n00bz

Last edited by z3r0c00l, Thu, 8 Nov 2007 11:22.

I'll get it out tomorrow, and steal some more valuable information from it.

I'll get the brake design one out too. Check back later

A giant book on high performance tires I found in my university library. It's pretty mental some of the stuff that's down in there.

I found another one on turbochargers, but the maths was so horrendous I couldn't even work out which equations would be most helpful to post! i think the devs are just going to have to wing it on that front!

Quote from dougie-lampkin :

Why don't you guys have any problems with drifters? LFS is not a "drift simulator" either.

"We" do have problems with drifters, all the time. Most of them are over at www.lfs-torque.net now.

Just look at the number of locked threads where people got personal on their views about whats right.

Perhaps the cruise servers need their own space too.


LFS perfectly simulates the conflict between ricers/drifters/racers/street-racers/oval racers, that's for sure.

But this is coming from one of those annoying gits who thinks anything that isn't rear wheel drive is wrong wheel drive.

Last edited by z3r0c00l, Wed, 7 Nov 2007 21:42.

Ah right, thank you for that clarification

I've started buying pre-bedded pads, little bit more money, but it saves the guesswork trying to settle them in right, and it means you can get bedded pads for the rear, something you can't do without a brake bias adjustor valve in a "normal car".

I've been in the car with my cousin (he does the odd rally stage) coming down Box Hill, and he cooked his brakes, we slowed down off the 60 at the bottom to the rounderbout, and they promptly caught fire. That was a Mk2 Golf though... not even the GTI, think that counts as a road car!

I've been keeping up with your reynard site btw, looks to be the best fun I never had!

Last edited by z3r0c00l, Wed, 7 Nov 2007 15:43.

In cars with rear disc brakes, the handbrake is usually a set of drums inside the hats of the brake discs. Speaking from experience, if you cork about with it partly on, or, do a lot of yanking while its running,

The shoes just wear down to nothing, and dismount from their assemblies.

Then you buy new pads and discs at the rears, and a new rear brake innards kit (to replace the mangles assembly), and some new brake shoes.

Then you stop being a complete tonk, and realise, no, you are not the stig, and that yes, this car has to get you to unversity every day!

/offtopic

on topic : I can't find any figures for the thermodynamics of drum brakes, no any rates at which heat dissipates. Guess the UF1 and the XFG will have to go in the bin - nevermind, they're both wrong wheel drive.

Last edited by z3r0c00l, Wed, 7 Nov 2007 15:33.

It's probably just the car beeping to let you know the temp has dropped below 0 degrees c or 37 farenheight. It's an ice warning thing, lots of cars have it.

The Rotor may be an excellent conductor of heat, and have a roughly even temperature through out, but green fade (i think this is the right term, the one where little bits of pad get vapourised from the compound and make a gas which stops the pad contacting the rotor so much) would require modelling the pad surface, pad body, and rotor temps at the very least.

If the pad is too hot for too long that would impart heat to the caliper, and in turn boil the brake fluid, resulting in another kind of brake fade.


So you'd need atleast fluid, pad body, pad surface, rotor temp, and a cooling rate for each of those (dependant on the speed of the vehicle). You would also need pad wear, and disc wear.

The second section of the attatchment points out that if the pad experiences too much braking force on the disc without locking up, then it wears VERY rapidly. Concequently it should be possible to overheat the brakes making them very hot, but brake amazingly for a while, before the pad wears down super fast.

I can't remember the title exactly, I was digging around in the library for stuff on karts, and came accross it. It's for designing brakes. I'll have a look when i'm back there tomorrow.

I thought that was the simplified way of doing it, the complicated method in the book had sections for each strip of the brake disc in increasing radii, and the pad divided into 8 sections!

I'm guessing the constants you are referring to are disc mass etc, seeing as those don't change with every brake heat calculation?

The combined braking and cornering, and accelerating and cornering graphs should look like this apparently...

Last edited by z3r0c00l, Sat, 10 Nov 2007 19:31.

Everyone wants it, thought these might be of some small assistance, maybe.

Naturally some sort of "brake heat convective and radation" cooling model would also be needed. This should just be a fairly straight adaptation from the tyre model though.

There are two things the cooling model requires.

The rate at which the brakes cool down with various levels air speed (this varies depending on vented or solid discs, vented discs cool twice as fast(says this text book)). The second rate is the radiation of excessive heat from cooked rotors. (when they get massively hot they radiate heat at a rate that needs modeling).

Last edited by z3r0c00l, Sat, 10 Nov 2007 19:31.

as per thread title, see attached picture?

http://www.lfsforum.net/attach ... id=42200&d=1194376136

Last edited by z3r0c00l, Sat, 10 Nov 2007 19:31.

it means you are doing it wrong.