The locked tyre pushes the water. Just go with your hand over a wet ground you will push a lot water in front of your hand.
So there is more water in front. The profile of the tyre won't work to get rid of it, if the tyre stands still.

So this increases the water film and helps aqua planing to happen at a lower speed as with rotating tyres.

Just think about the reason for a good profile helping against the wet road. Aqua planing will happen somewhere, but it needs more speed. And then you can just hope to slow down in time before hitting something

@Nightshift:

You didn't understand me

Of course aqua planing can appear everytime. But a locked wheel does help it to appear, because it makes the water film in front of the locked tyres thicker ...

So you provoke aqua planing to happen at lower speeds with locking tyres and therefore increasing braking way.

And i won't disagree that you can do nothing if aqua planing happens. But if you create it artificially by braking without ABS and locking the wheels, ABS would help because it keeps the tyres rotating and therefore reducing the water film in front ...

@dark times:

I just think it would be a good time to implement these ones in order to make the simulation of traction control good ...

Quote from Shotglass :

which is a reduction in force of ~20% at worst not 100% like in that silly video

Yes, there comes the heat problem you said. In the video the tyre is overheating in addition to 20% reduction of force.
I think an addition for marketing ... just brutal locking brakes to show it exxagerated.

Quote from Shotglass :

neither because tyres dont work that way

Tyres are more complex than a block of wood or something. But they use friction too. Without static friction AND sliding friction a tyre wouldn't work. There is some factor of rubber "connecting" to ground but still there is a lot of friction.

Quote from Shotglass :

nope

So how do tyres work? And why then there is a reduced force when the tyre is spinning to much or locked?
I named a lot of sources and there are lots of physics books and other stuff.
You just made a statement of your own ... tyres have nothing to do with friction? Dream on
They are more complex as I said, but still there are some rules which count.

Quote from Shotglass :

and guess what there is in lfs

Show me a replay of you braking from 200 with locked wheels and then SIGNIFICANTLY shorter without locked wheels. Not just a few meters from 200 ...

Quote from Shotglass :

the one with 2 different surfaces
doesnt really matter which way the car faces with locked tyres so its a valid comparison

Its not comparable with a straight line braking test on even underground. ABS has to do a lot more and therefore won't result in a perfect braking distance. It has to adapt left braking force to right one on different grounds.

For real a lot of people will agree that locked wheels on the wet are really bad ... as you can read nearly everywhere.

Quote from Shotglass :

modern systems may be better thanks to the mechanics damping the higher frequency inputs from the system but the basics are still the same

Yes, on the dry they won't really lock the wheels permanently. Just trying to reduce braking force. Perhabs just at the first moment to recognize the locked wheels ...

Quote from Shotglass :

go ahead and believe the marketing but the whole point of a road abs is to keep the car steerable and as such it will never equal threshold braking
it might be true for a racing abs but thats a completely different system

It was developed to keep the car steerable. Right. But if you get a very good point between 20 and 40% wheel slip it will also decrease braking distances as stated on wikipedia in german and english most of the times.

But as I said it isn't about good driver vs. ABS ... just about locked wheels vs. ABS. So no reason to argue about that one ...

Last edited by RIP2004, Tue 13 Jan 2009, 23:49.

@s14

Nobody will disagree.

But for simulating traction control and ABS these issues get important somehow, to make these systems useful and demonstrate the increased safety ...

@Shotglass:

You can read at a lot of sources values for optimal grip of tyres. The values may not all be the same, but everywhere you can read : locked wheels don't have optimal grip, because they slide.

Simple Physics ...
sliding friction vs. static friction. Who wins?
Eventhough a tyre with rubber is much more complex, this simple rule still stays and affects it.

So even if we don't watch at temperatures and temperature would be equal, there should still be a difference. Perhabs then not as much and most likely this is a big part of the "braking problem" in LFS, if it doesn't heat up exactly. Overheated tyres will perform worse.

Just read at wikipedia:

http://de.wikipedia.org/wiki/Antiblockiersystem (german)

Optimal grip is at 20-40% wheelspin. Locked wheels DO have about 15-20% less "stopping power". So still significantly even without overheating.
So 200-0 about 140-150m in a normal car. => with locked wheels about 180m ...

And I watched the video. The situations in the wet were about steering around an obstacle. As we know that isn't possible with locked wheels.

The other part is about braking on different surfaces. There is no real situation where one car brakes straight on the wet with ABS und one without.
They showed different aspects.

As you can read again on wikipedia and other sites : locked wheels push the water in front and the tyres begin to swim. Aqua planing. So locked wheels are very bad in the wet and the difference in braking way should be significant. You can see it a bit in the obstacle avoidance part of the video. The one with locked wheels seems to be much faster when arriving at obstacle than the one which avoids the obstacle by steering.

AND you don't really seem to read how ABS works. It doesn't try to lock the wheel often ... it tries to stay between 20-40% slip ... so it pumps against the braking but doesn't try to lock the wheel. Even not for short periods.

This is just the case with very modern ABS Systems. ABS Plus. They recognize surfaces like gravel and lock the wheels on purpose to use the better braking power of locked wheels in these special situations.

If overheating is a problem it should be fixed too of course

RIP

EDIT:

English wikipedia:http://en.wikipedia.org/wiki/Anti-lock_braking_system

"On high-traction surfaces such as bitumen, or concrete, many (though not all) ABS-equipped cars are able to attain braking distances better (i.e. shorter) than those that would be easily possible without the benefit of ABS. In real world conditions even an alert, skilled driver without ABS would find it difficult, even through the use of techniques like threshold braking, to match or improve on the performance of a typical driver with a modern ABS-equipped vehicle. "

Your opinion of threshold braking is old. It was correct with very old ABS Systems, which regulated very slowly. Modern ABS Systems are at least as good as a really good racing driver ...

But I didn't want to discuss sensible good braking without ABS on track vs. ABS braking. A skilled driver can get as close to those 20-40% slip as well, so he could match it.
Here it is about locked wheels vs. ABS braking. That is a whole diffent matter

Last edited by RIP2004, Tue 13 Jan 2009, 22:37.

Hi there.

I don't know if this already happens. It would be quite worth a lot of time to wait for the new patch. So sorry if this was supposed to be a surprise ...

but

Shouldn't tyre physics be improved in major points to simulate the new "electronic side"?

What is the point of a traction control system, which doesn't improve anything above stupid full throttle acceleration? As long as tyres produce almost the same amount of g acceleration with really bad (high) wheel slip as with good (20 to 40%?) wheel slip, traction control won't be able to show what it should do ...

Same point goes perhabs to braking, as it always seemed to me that fully locked wheels don't make the way to stop significantly longer. Perhabs a little bit, but not as massive as they should.

Out of my Spinoff ABS post:
Just watch here at about 2.20:

http://www.youtube.com/watch?v=ZSqGP...eature=related

This is how much ABS improves braking way on dry tarmac with new tyres if one just stupidly locks the wheels all the time. The small spin will perhabs exxagerate it a bit, but even from 100 km/h the difference should be quite visible.
A very good driver may brake as good as a modern ABS but noone who just locks the wheel unti the car stopped.
This would only result in shorter braking ways on snow or stuff that can be pushed in front of the locked wheel to help stopping, but not on usual dry road. (in the wet there is a even a much bigger difference because of aqua planing under the locked wheels)

In LFS if you brake at 200 km/h with very strong brake setup and just lock the wheels the braking way will be not bad. You won't beat that a lot with sensible, reasonable braking. There should be several car length in real life between a locked and a good braking ...

So next point is the new ABS. It can't show its effectivness. Ok, the main target was to preserve steering and it will preserve steering while braking, but braking won't be better in terms of the way. As said I don't talk about a good driver vs. ABS, which should be about equal with modern systems ... I am talking about full locked wheels versus ABS braking.

______________

To summarize it ... the longitudinal acceleration of tyres in LFS should be corrected to see, if the new systems really work as they should. Both, negativ and positive acceleration.

As Scawen said:
"This is on the mechanical side and the electronic side. We are trying to make a good simulation of the traction control systems and the stability control systems, well known to be a very good feature of VW cars."

So perhabs there will be a fix of tyre physics too. Otherwise traction control system will be quite poor at starts
It is finally time to kill those flaws. Even Need for Speed "simulates" to much wheelspin at drag races and punishes it. All ISI games and even Gran Turismo do this too ...

Cu on track
RIP

Last edited by RIP2004, Tue 13 Jan 2009, 14:41.

Quote from RIP2004 :

A usual driver will always lock the wheels a bit if braking hard without ABS and therefore have a longer brakingway.
A very good driver can try to get the wheel as close to those 30% as possible. But I bet he won't beat a modern ABS System which interacts many times per second.

@bbman : What do you think I wanted to say with this?

Sure, a good driver won't lock the wheels completly for the whole braking distance like in the youtube clip. So the difference won't be as big or he is even as short as the ABS car.
But I would bet he can't beat a modern ABS, which regulates over 10 times a second and can release every single tire break.

Racing ABS Systems, if allowed, are even more efficient. I saw somewhere a clip where Sabine Schmitz (who won the 24h race at Nuerburgring in Germany and was third last year) was happy to have ABS in her racing car. And she IS a hell of a driver.

Take modern very fast cars ... like Porsche for example. ESP (called PSM at Porsche) can be switched off for very fast driving.
Can ABS be turned off in any modern car? Even for a racing track day?
No? Ask yourself why The very old Audi 100 of my grandpa had this feature

Modern ABS is better. It is even used in some races ... and always an advantage But it is often forbidden to show driving skills instead

Those opinions about ABS having longer brake distances is out of date.

This was the case with early ABS Systems, which didn't react quick enough.

Today ABS is very fast and will get the tires to about 20-40% slip. 30% would be for the perfect stopping power and a lot better than locked wheels. If it will even get faster, it will be even closer to 30%.

Just watch here at about 2.20:

http://www.youtube.com/watch?v ... Wroes&feature=related

This is a braking test with exactly the same kind of new car and the same new tires on perfectly easy and dry conditions.
In one car wheels are just locked and the other uses ABS.

In the wet the difference is even more significant.

The only situation where ABS is possibly braking less is on snow or a lot of dirt on the street. A locked wheel will then push it in front of the wheel and it helps stopping. So a locked wheels is better in those situation.

Today ABS Plus will be used in cars. This takes into account these situations and will lock the wheels a bit to use this also.

A usual driver will always lock the wheels a bit if braking hard without ABS and therefore have a longer brakingway.
A very good driver can try to get the wheel as close to those 30% as possible. But I bet he won't beat a modern ABS System which interacts many times per second.

So longer braking ways are of the old days where ABS was reacting slowly and only a few times per second. Today it will always be at least as good as a good driver, but most times even better. And nobody has to concentrate ... just hit the brakes hard and you can concentrate on steering and other stuff.

But one thing is right: ABS was developed mainly to preserve the possibility of steering around an obstacle while braking hard and not to have the shortest possible way, because that was at that time not the case. A good driver could do this too by just not locking the wheels ...

Last edited by RIP2004, Sun 4 Jan 2009, 23:17.

Cars do have ABS in reverse. At least my standard coupé does. I often drive reverse because I have to, to get to the street. And I had to break once, while i was very fast. And the brake pedal did move (pump), while ABS was working.

Last edited by RIP2004, Fri 19 Dec 2008, 03:11.

Quote from Scawen :

Well, no, about tyre physics, I haven't been thinking about tyres recently. On the physics side of things I'm more concerned about collisions and damage before another session on tyre physics. My brain is too small to think about TOO many things as once. So, no real reply, no plans on that at the moment.

Ok thx Then somewhere later. A good collision will be also great

Quote from RIP2004 :

Just one question: before LFS is out of Alpha state, will it have another tyre physics update?
The problem about longitudinal grip seems to be still present. It would solve problems about locked differentials and heavy wheel spinning being fast and perhabs other things.

Or would that be more a thing to correct in Beta Stage as tweaking?

@Scawen

I don't want to spam, but some other people were also curious about that question. Perhabs you didn't read it in all those posts
Can we get a comment on that, as it is on topic somehow?

Keep it up.
RIP

Quote from Mattesa :

Would it be fair to say that it's hard to tell if iRacing has any similar physics holes because of their much more limited (...realistic) setup options? For example, you can't put a locked diff into the Solstice to see if it's faster. It's also been mentioned before that the fast setups in LFS make the comparison much harder. For example the XRG, it's ridiculous how that thing drives, completely not realistic how tail-happy it is, but that's the setup and not necessarily the underlying physics. But thanks for analysis, some really good feedback in this thread.

If there are physics holes, they will show up later with more cars I think I like the idea of limiting setups, because then its more the driver. On the other hand some experimental cars to learn about setups are great too.

You may however be able to test the accelerating thing, comparing plain full throttle starts with controlled throttle starts.

Yeah, I agree on the setups. They make a really huge difference and some much to tail happy RWD cars can be tweaked to a safer real world car setup and will then understeer quite a bit.
In my experience the differential does a LOT. An open differential is much easier to drive at the limit, but still not 100% realistic somehow, because it feels just like a traction control somehow Real RWD cars often are quite understeery without an real open diff.
The missing snappy thing isn't a setup thing I think though.

@Scawen : Great news. Thx for all of that and looking forward to it. Sounds promising.

Just one question: before LFS is out of Alpha state, will it have another tyre physics update?
The problem about longitudinal grip seems to be still present. It would solve problems about locked differentials and heavy wheel spinning being fast and perhabs other things.

Or would that be more a thing to correct in Beta Stage as tweaking?

Continue the good work

@technique : Damage sounds to me like LFS damage, but just stronger.

So there is no engine damage. People will continue driving after a high speed crash. Slow but they continue. I dislike that a bit. Ok, you have to steer full right to go straight, but still you will move with a car which should be out of race and perhabs, even if you don't want that, disturb someone else with no crash yet.
If you do a hard crash it should be over. Just like Hamilton at the exit of the box Wait till race is finished or do another.

@Michael Denham : Sounds good to me what I read about iRacing physics. Still I think its a bit expensive, because I race not always a lot. Sometimes I don't touch a wheel for a week or two ...

I also like the idea of punishing stupid behaviour, although it will be tough to identify it.

In LFS some things are still to linear. It seems to have one of the most complex physics modells calculated in real time. But still it feels more like a computer game to me than some of the cheated ISI physics sometimes, because you seem to hover above some road. Nearly no bumpy jumping and if the car begins to oversteer it does it slow. Instead of Grip, grip, grip and suddenly it begins, ... its just fading from grip to oversteer smoothly in LFS and smoothly back most of the time. In most situations the result counts and not the way, which may be better in LFS if expended further and further. But development gets slow at the moment. I have to say though, that Slick cars drive really well in LFS. Its more about the road going cars with street tyres.
And still as Scawen said in March 2007 there is something wrong with longitudinal grip, which leads to accelerating nearly perfect with heavy spinning wheels and also makes the differentials behave strange. Locked diffs are by far the fastest way, which isn't that realistic.
I am sure it has a lot more impact on other behaviour. If the wheels have to much grip with heavy spinning there is more movement in the driving direction when sliding, than there should be. So a correction will change all the physics behaviour a lot I think.

But to get back to topic somehow : what about iRacing? Is full throttle at start the best way or are you slower than others, who control there throttle a bit more if you react nearly equally to the signal?
And can the car be unusable if hitting a wall with high speed? This has a big effect on crash kiddies, as they can't continue to do anything. In GTR the race is over if you hit someone or something to hard. Engine off and stays off. So no movemement possible and also no reset possible, if server settings are good.
What about controlled long drifting all through the corner? Possible? (Something you can't do in GTR really but mostly because of the cars. See C6 by Niels ... it is possible with ISI to do a long drift, eventhough it is more difficult than in LFS. Not sure which one is more realistic, as drifting in real life should not be that easy and in a computer game with no feelings even more)

Last edited by RIP2004, Fri 27 Jun 2008, 14:02.

Is there a total destruction in iRacing? Usually a race car doesn't drive at all anymore if crashed with >100 into a wall or something.

Hi all.

Yesterday I had a great race with 8 people. Mostly from Canada or USA (it was late). Very close racing, a few small contacts. The start was great. In Qualy I just got the 4th, but I could pass Nr 3 and 2 and get to second until someone pushed my back in T1 and I spun out. I was lucky ... no big damage and I could go for it from the last pos. If it was hard enough I could also well be finished for that race but luckily no big damage. (unlike LFS, where you're nearly always fine to continue to the box)
Very exciting but fair racing. I got the first people really fast but then it got harder. After killing 8 seconds I finally was close enough to get in Pos 4. And this dude was really fair. He said I could pass on the right on the straight and so I did. But the grip in the right wasn't as good as on the racing line and so I skidded a bit and began to spin. He braked hard and still let me in front of him.
Rest of the race I just had to fight against my tires, which were nearly destroyed But I could stay in front and be still a little faster than that fair guy behind me.

I enjoyed this great sound. Sounds like on TV. The racetrack ... very very nice. Racetracks you know and see in the real world. Very precise and lots of bumps. Its really great to break on a bumpy straight. You can acutally feel (hear) when the tires lock up or not and the car is bouncing a little, which makes it more risky and leads to skidding a bit.
Great real cockpits which do a lot to immersion.

The start is also nice. Not everyone gets away nearly equally like most times in LFS by just full throtteling, because of still wrong longitudinal grip. You have to get the right RPM not to stall, but spin a little, but also not to much.
The braking is also more exciting just because of those bumps. Its not easy to get the right amount towards the end and enter a corner clean.

You can push those cars hard without always counter steering. If you drive slow, everyone can go around the corners. If you push them you have to work a bit harder A lot snappier and grippier than LFS, where e.g. road cars feel still a bit like driving in the wet.



Then I thought, that I love the big V8 sound of my Saleen and the surrounding Ferrari, Lamborghini, BMW and Porsche and all those interessting well known real cars. Even this old 911 GT2, that was easy to get. I respect drivers who choose those cars and push them hard. They often don't finish last.

I love those great known precise tracks with all their bumps like Imola, Spa, Monza, Barcelona, Hockenheim and soon Nürburgring Nordschleife.

Get the right time and place and people will drive fair and mature, because a contact may finish the race ultimately with engine off and isn't starting. They will indicate where to pass and let you pass if you are really faster.
And it can suddenly rain and get wet ...

No costs for great races. Statistics can be done community driven, if you like it by just driving organized races. I payed only once for GTR2 and it should be cheaper than 1 month iRacing by now with IMHO much more interesting tracks and cars. It may be ISI physics, but very very well adapted so all those little details in racing are great with those cars.

*running away*

Last edited by RIP2004, Fri 27 Jun 2008, 11:49.

Hi.

One more physics thing: longitudinal acceleration and grip of tyres is wrong.

Scawen said it himself in one Post:

Quote from Scawen :

But we know the longitudinal tyre forces need some improvements, for example the well known thing that in many cars the acceleration seems too good if you just wheelspin.

It shows he is aware of it. This post was in March 2007 ... so I hope something will be done soon :-)

As I said it differs a lot with the car.

I think it isn't really bad with the FWD cars. They feel pretty well. But cars like the FZ50 feel quite wrong ... don't you think?

Well it differs a lot between different cars.

I drove a usual Opel Vectra A (Vauxhall) with about 90 HP before. And it was a bit less grippier, but I still had the impression of a bit better grip than in LFS.

Now I drive a Opel Astra Coupé with about 150 hp. It has a sports suspension and is a bit more towards sports. Its still no real sports car, but there is a lot of difference in corners. I tested it often in corners I know blind, where there is a lot space and no other people, that can get in danger and I still was afraid to push it harder. It grips so well. So it took a bit of time, until I got it to the limit.
A real sports car has even a higher limit I am not really sure how much I would dare to get it to
But even my "slowish" car is very hard to get to this very last limit, which occurs in lfs quite often. The cars in LFS are mostly a bit more sports cars

It is not really comparable to a simulation at the PC, but it is much harder to get out of control in a real car in dry condition. You have to really steer brutally fast ... and even than my car is really really stable.

Just let someone drive a slow round in LFS, who drives for real ... he certainly will have an accident or at least spin in a RWD, even if he/she isn't pushing really, but just driving slow.
RWD cars aren't that bad by far in reality. I also drive a 180 hp RWD Omega from time to time. And it will understeer at the limit, wobbling around with the soft suspension But still grips better and won't by far spin as fast as in LFS, which is for sure also a lot because of different setups and ESP Systems.

In LFS even at low speed a rwd oversteers sometimes. Its hard to reproduce, but just try the FZ50 with very soft accelerations and careful steering.
I tweaked everything in setup. Open differential, traction control on and very high, even different tyres in front and back. And still it is a dangerous car, whereas a porsche 911 happens to be driven by old people, unexperienced women etc. and won't crash, until really pushed hard.

EDIT: btw. I think that the cars with slicks grip quite realistic, eventhough I really can't compare that to RL experience. But it just feels right. But some people who have real slick experience still describe rl slick grip higher ...

Last edited by RIP2004, Sun 24 Jun 2007, 21:31.

Hi there.

Most of the usual points have been mentioned. It is right, that you don't have the correct impression of speed because of the lack of perfect graphics and forces on your body.
And setups do a lot too.

BUT it is still interesting, that a lot of people, who have RL experience mention this "ice" feeling of road cars. Its still the impression I get too. I move a road car sometimes at the limit and over the limit till ESP catches it again
And you have a lot of grip on street tyres with a usual car.

A part of it will be because of the factors mentioned above. But I am absolutley sure, that there are still some main things wrong with tyre physics.
In other games, which grip more but don't simulate as much things as LFS does, the grip sometimes feel alright (rFactor, GTR2) and people don't complain about icy/wet feeling, eventhough the g forces there are also as correct as in LFS.

I am really looking forward to the next update. Scawen mentioned, that he is aware of the longitudinal bug.
Cars accelerate way to good with heavy spinning wheels. This has a huge impact on tyre physics in my oppinion.

It will not only affect starts in the way, that full throttle starters get away pretty good in comparison to real life, where bad wheel spin results in a bad slow start.

It also affects the grip in corners a lot. Locked differentials with bad spinning wheels are very fast in LFS. In real life its not always the best way to have fully locked differentials.

If a FWD car is in a hard corner and accelerates hard, the spinning wheel will still have a bit more traction than in reality and therefore it understeers less.
The other way around a RWD car with hard spinning wheels will spin faster, because the rear tires grip a lot more while spinning and therefore are pushing against the instable back of the car. => spin.
In real life the spinning wheels would lose a lot of longitudinal force and therefore wouldn't push as hard at the back. It would get into sliding and oversteering a bit slower.

Just a few examples of what I could think of. There are several other situations which are affected as well. So balancing tyre physics a bit more and removing this bug with high longitudinal grip will affect driving in LFS a lot. We'll see if scawen fixes it and what problems remain after that.

Greetings
RIP

Quote from Scawen :

But we know the longitudinal tyre forces need some improvements, for example the well known thing that in many cars the acceleration seems too good if you just wheelspin.

I think I will have to plug in my wheel soon again

I think a change of longitudinal forces with spinning wheels would have a huge impact on the physics, not only when accelerating at the start.

I would love to see that corrected in Patch Y, as it is the last bigger flaw I could discover in the great tyre physics of LFS.

This will be less noticable now with next patch because of the false starts and reaction times, so it is good to know, that you are working on it.

Keep up the good work

Quote from DaveWS :

When you say not so good in other ways, do you mean what I mean?

- The way a full-throttle wheelspin start gives as good a start as a controlled start
- The way the car slides around quite easily, and does so almost very gently, with no real "snappiness" between sliding and gripping

Are we all on similar lines here??

Exactly my thoughts. Sometimes it doesn't seem to regain grip as fast as a real car would.

There is still a lot of oversteer even with a open differential (which helps a lot )

I really also would love to see some kind of ESP like the TC which helps against oversteer for beginners, but makes you slower like in real life by taking away throttle and braking single wheels.

Interessting discussion again about that topic

I really hope that this longitudinal grip is fixed. It would make starts even with the current signal system a lot more enjoyable, as everyone would try to give a good amount of throttle.
If you do it right, you should be quick. If you just do a full throttle start, like most people now, you are a bit slower and some starter behind you will overtake you.

And if you try the right amount and fail, by giving not enough throttle, you should be very slow at start.

Much more fun at starts.

I really hope that this is fixed before the free start system is implemented. This would hide this last problem of LFS tire physics because of different reaction times to the signal.