In last few days I've done a lot of testing about tyres. (I have one question/suggestion)

Does LFS tyre model calculate that tyre wear changes diameter of wheel? If you ask me answer is NO.
Well someone will probably say that this changes are negligible, but actually they are not so small.
Different tyre diameter is like different gear ratio. Also pressure in tyre should change diameter, as well as temperature but that two are negligible compared to wear.


EXAMPLE:
Car used: XFG
XFG have 15 inch rims and 185/50 tyres = 56,6 cm diameter (got this values from LFS Tweak)

Picture weared / non-weared tyre:



Tyre height in our case is 185*0,5 = 92,5mm = 9,25cm (non-weared).
When you compare weared vs. non-weared tyre you can see clearly that weared tyre is at least 1 cm thicker. (which in normal for everyday car after few months of usage)
Our new real diameter is 54,6 cm of even lower.

If we compare these two values in percentage:
54,6/56,6 = 96,47%

That means car with weared tyres will travel 3,5% less distance compared to car with non-weared tyres if their wheels have same rotational speed.
Percentage varies a lot by wheel height. (smaller wheel = bigger difference)


If you compare car speeds at same rpm :


In table there are shown values for XFG (default set - HARD TRACK) at rev limiter (8000 rpm).
Weared speed value is calculated if tyre wear was 1 cm.
Real speed is measured using Aonio.


2nd gear

4th gear



I would like to hear developers opinion about that.
We want LFS as realistic as possible, right? Then this is must do thing. I hope this will be introduced with new tyre physics.

respect for that!

implementation would be nice

Because thread thickness change is not there, the F9 view should be considered by no way as any to-scale representation of the tyre's geometry. You can't calculate the percentage using what you see on the screen.

I do agree with the rest of your post.

Quote from Keling :

Because thread thickness change is not there, the F9 view should be considered by no way as any to-scale representation of the tyre's geometry. You can't calculate the percentage using what you see on the screen.

I do agree with the rest of your post.

Not sure did I get it right.
In F9 screen there is shown thread thickness, weared tyre is noticeable thicker that the other.
By my assumptions every tyre should have at least 1 cm rubber (to wear), and my tyres were very close to blow up.
Problem is easly noticeable if you have flat tyre, you can still reach exact same speed as with nonflat tyre, but you need longer straight for that.

... Seems like it should be there though, wear does change diameter hence flat spots being present in the sim. Not sure why your results don't show that.

edit: physics wise it's there since it affects FFB, I guess maybe he overlooked it in the velocity math somewhere?

Even if the diameter is smaller, the tyres will have less surface touching the ground, thus having less resistance. So the tyres will cover a smaller distance if the tyres turn as fast as they did before they wore, but because it has less resistance they will turn faster and cover the same distance.

Just a theory, don't know anything about tyres or cars

IMO he was doing a test with full rpm at exact gears and it should show difference. If not it isnt implemented as many other things yet.

Quote from L@gger :

IMO he was doing a test with full rpm at exact gears and it should show difference. If not it isnt implemented as many other things yet.

Unless he measured that speed with cars speedometer, which would make all those figures useless.

Daniel, can you confirm that you used AONIO or any other coordinates based program to measure the speed?

Quote from Whiskey :

Unless he measured that speed with cars speedometer, which would make all those figures useless.

Daniel, can you confirm that you used AONIO or any other coordinates based program to measure the speed?

Read first post:

Quote from DANIEL-CRO :

...Real speed is measured using Aonio....

In tables:
real speed= AONIO
speedometer=car speedometer

oh, my bad, missed that line

when you measured unworn tires were they at optimum temperature?
Just to discard that the increased size in worn hot tires is equal to unworn cold tires.

Quote from Whiskey :

when you measured unworn tires were they at optimum temperature?
Just to discard that the increased size in worn hot tires is equal to unworn cold tires.

both tyres at 22-24 celsius, same speed


take a look at picture I've posted.
picture
how to explain that real speed is same with flat and non-flat tyre at 1st gear. There should be pretty much difference.

Re: #4

As you have pointed out, there's (very likely) no tyre tread thickness change (or diameter change caused by tread wear) in the physics system, which means there's no "hard-coded" value of tread thickness. The F9 view may give you a visual presentation of RELATIVE tyre wear, but you can not count the pixels and calculate the diameter difference using the pixel count. If we're correct on the "thickness change not taken into account" part, then the tread thickness you see on the screen doesn't mean anything in the tyre simulation algorithm. The only thing it does is visualizing the relative tyre wear variables.


Re: #11

Not 100% sure about my theory, but flat / non-flat sounds like another story to me.

The tyre tread doesn't shrink its length very much when the air goes out. The tyre becomes flat because the tread (and the wall), which is no longer supported by inner air pressure, is forced to FOLD or TWIST. The tyre may look smaller, but the overall tread length shouldn't be greatly changed.

When your car accelerates up to a stable (top) speed, the tyre-tread and the ground shouldn't be sliding much against each other. This is true with the tyre being flat or not. Therefore, if the the tread doesn't become shorter and the wheel rpm doesn't change, the car should be going at the SAME speed.

(same times of tread length) * (same tread length) / (same time) = (same speed)

If you calculate the linear speed of the outer edge of the rim, it is going slower than the outside of a non-flat tyre. (at same wheel rpm) However, when the tyre is flat, the tread which touches the ground is actually going faster than the rim which touches it, and that's why they have the same average angular speed.

I don't think you'll get the same result in real life. When a tyre goes flat in real life, there is a lot of friction between the inner surface of the tyre and the outer edge of the rim, slowing down (twisting) the tyre tread somewhat. In the current version of LFS, there seems to be little (if any) friction between the two.

If my theory above makes sense, the test you did actually shows how wonderful the tyre simulation in LFS is. The system was made so many years ago, and it does have geometric modeling of the tyre rubber, which is independent of the solid rim model. Brilliant.

Just to be sure, tyre thread ("tread" by google) is (from wikipedia):
The tread of a tire or track refers to the rubber on its circumference that makes contact with the road. As tires are used, the tread is worn off, limiting its effectiveness in providing traction.

I belive that LFS uses tyre wear variale only to know when will tyre become flat.

About flat tyres - watched some videos about driving on flat tyre on youtube and to me it seems that this is identicaly to driving on rim. Probably there is no so much grip between rim and tyre, so tyre slips...


We need Scawen , I hope he finished his birthday party

AONIO uses OutGauge to get the car's speed, right? OutGauge provides the speedometer readout, not the real speed, you'd have to use OutSim for that.

Not truth, try brakeing with locked wheels. Speedomter goes to 0 (or close), but Aonio still shows speed (your real)

Daniel is right about the need to take into the account the tire-wear. But there are more factors:

1) A worn out tire due to its lessened radius, will have lesser mass and more importantly lesser moment of inertia. So it is easier to rotate that wheel with the same torque. This I am sure has implication on acceleration. Hence the reduction in linear velocity due to diameter decrease and increase in angular velocity(RPMs of the tire) due to lessened mass and lessened moment of inertia may try to cancel each other

2) Theoretically this lessened mass and lessened moment of inertia of the wheel should improve top speed too I believe, hence trying to cancel out the reduction in speed due to lessened diameter. But I am not sure about this second point.

But Daniels numbers may not be accurate because:
1) The F9 may be just an approximation, you should count pixels etc, as someone said above.
2) There may be other variables apart from the radius change alone, like the 2 I stated above (and many more that I/we don't know)

------

Quote from Ezpz :

Even if the diameter is smaller, the tyres will have less surface touching the ground,

Regarding this, due to tire-wear, and due to thinning of tire, I think there will be more deformation to compensate this, hence making the contact area constant, and hence rolling resistance may not change I feel.
------

Overall, I think there are many factors apart from tire radius. Also we need to think whether the typical tire-wear in a race decreased radius large enough to have significant changes. (I can't take that F9 data on face value)

It could also be possible that the net effect of all these was too little and they did not implement it hence.

But if it really decreases speed and if it is implemented then that is another reason for better tire maintenance during race

I don't know if a worn out tyre on LFS reduces the car top speed...
I'm almost certain that what happens is the exact opposite.

What I'm definitely certain of is that a worn out tyre has a lot more grip than a brand new one. Which is know and well discussed about there's some years now.

I'm just happy that you guys seem to be trying to understand why is that and how to solve it.

Because I've never seen an old racing tyre having more grip than a brand new one.
It's really weird and non intuitive.

I dont think that worn tyre have better grip, before in hotlaping drivers used to wear their tyre to heat them up to optimum temperature
If you take a look into some new WRs (with tyre heaters), youll see that no one wear out his tyres, because they are already at optimum temperature, best grip with unweared tyres not to talk that most WRs times are lowered by 0.2 s with new tyre heaters

Consider redlining the car.
with a smaller tyre, you would have a lower top speed.

Quote from DANIEL-CRO :

I dont think that worn tyre have better grip, before in hotlaping drivers used to wear their tyre to heat them up to optimum temperature
If you take a look into some new WRs (with tyre heaters), youll see that no one wear out his tyres, because they are already at optimum temperature, best grip with unweared tyres not to talk that most WRs times are lowered by 0.2 s with new tyre heaters

They don't for 2 reasons:

1) The replays have a limit now, which doesn't allow enough time for them to wear out the tyres as they used to do before.

2) The tyre blankets allow a pretty optimal temperature spread (as in, the optimum temp. on the whole surface of the tyre), so it has a lot more grip than a "regular" tyre (with cambers not allowing for such a spread and some good difference between the inside and surface temperature of the tyre) at optimal temperature for the compound in regular/realistic conditions.

In short, the tyre blankets are quite artificial/unrealistic.
It's not the case that new tyres suddenly have better grip than old tyres.

I'm still pretty sure that worn out tyres have a lot more grip than brand new tyres, comparing them with the same temperature and spread across the tyre surface and it's inner temperature.

Ask any endurance team driver.

I am pretty sure that worn tires from my best experience in FBM gives you better traction properties. I saw many guys running their pbs and overall much more better lap times at these conditions...

I dont think so that small changes in grip affects top speed of a car. There is still nearly 0 slip in wide range of tire traction in straight line driving...

In real life I always set my best lap after a few laps on a set of tyres.

Quote from Meanie :

1) The replays have a limit now, which doesn't allow enough time for them to wear out the tyres as they used to do before.

replay length is like 10 minutes, take for example WR XFG@BL1 (most driven combo, probably finest WR )... jinja jorj have like full 8 minutes to wear out his tyres, why he didnt if this is faster?
In older WRs there is like 1 minute of heating up (wearing) tyres than hotlap (which is slower...)
also compare old vs new (with tyre heaters) WRs on oval, every WR is beaten by 0.1 s or more... even if in old replays tyres were heated up to optimum temperature... in new oval WRs there is just pure hotlap, no wearing tyres

In real life tyres have best grip after few sliding spins, to remove dirt... from surface, and little heated them.

Quote from L@gger :

I am pretty sure that worn tires from my best experience in FBM gives you better traction properties. I saw many guys running their pbs and overall much more better lap times at these conditions...

That proves nothing, people heat up their tyres, and online you cant heat them up without wearing.
From my experience online, my best first split at BL1@XFG is 29.79 (heated, and worn)
And in hotlap, my best first split is 29.76 (heated) after like 10 attemps and also in hotlap I cant use racing line which helps me a lot online, online I have far more laps done. How to explain this?

Quote from L@gger :

I dont think so that small changes in grip affects top speed of a car. There is still nearly 0 slip in wide range of tire traction in straight line driving...

Agree, especially for speed like I used.

Quote from tristancliffe :

In real life I always set my best lap after a few laps on a set of tyres.

Yeah, I always make best lap (online :P) in about 3rd or 4th lap. (when my tyres are heated up)



From some guys I heard that weared tyre used to be faster in patch Y, but now this is questionable.

Scawen is only person who can answer this questions, we just assume

They don't "wear out" the tyres on the new hotlaps because by doing so, you would lose the perfect SPREAD of optimum temperature (as in, the inner, middle and outer edge and the inside of the tyre too! all in perfect optimum temperature at the same time), which plainly just do not happen ever on a realistic/regular/normal racing situation. Ever.

So yeah, having this unrealistic (I'm not moaning against it at all, even Scawen admitted that this - temperature wise - is a somewhat half cooked solution for the time being) excellent spread of emperature on the tyres is worth a LOT more than a few minutes of the tyres worn out.

You can even notice that the faster you start the lap, the better (and lots of people - using the new starting point option - do just that). Why? Again, because you don't want to lose the perfect temperature spread.

So I don't think it's really comparable.

As I said, ask any endurance team driver about this.
For some reason, older tyres on LFS, are a lot grippier (and therefore, faster) than brand new tyres.

And when I say older tyres, I mean tyres at least after their "half point" lifetime-wise, so to speak. The tyres on LFS are on their best and grippiest behavior just before the tyres go.

Say 10min before they go flat because of lack of rubber on them.
Before they start to "freeze" and whatnot.

With a heavier car (say 30% fuel on a FO8) you will run a lot faster on old tyres but around optimum temperature than a light car with brand new tyres (say, 10% fuel - same car), those last also on optimum temperature.

It's really obvious the difference.
I suggest you to run some long stints and see this for yourself.
I don't think anyone can miss it.

Again, considering the SAME temperature on the tyres:
To have a very old tyre (near it's death point) perform closely to a brand new tyre would be very weird. But even weirder is what we have now, with the older tyre outperforming the brand new tyre!

Any endurance (or anyone really that uses his tyres near the point of plain running out of rubber on them) driver to comment on this?

Old (thin) tires in LFS are faster than brand new tires, yes.