Jump to content Jump to content

Tyre Wear & Physics Dscussion


Recommended Posts

How is it with the grip of rain tires on dry in reality?

I once heard that newcomers always get rain tyres at practice drives because they can't get the slicks up to temperature.
From this I conclude that the grip of rain tires is good even without water. Probably much better than their grip on wet?

Would that be the right ranking?

1. soft tyres on dry
2. hard tyres on dry
3. rain tyres on dry
4. rain tyres on wet
5. soft tyres on wet
6. hard tyres on wet

Or are rain tyres better than hard tyres on dry surfaces? (What effect does ambient temperature have on this?)

How much faster do rain tyres wear on dry surfaces compared to soft tyres?

Edited by PaulNbg
Link to post
Share on other sites

Yeah, I would like to know that, too.

My assumption is:

1. soft tyres on dry
2. medium tyres on dry
3. hard tyres on dry
4. rain tyres on dry
5. rain tyres on wet
6. soft tyres on wet
7. medium tyres on wet
8. hard tyres on wet

My logic says, if rain tyres have the best grip on wet of all tyres, they of course must be also pretty good on dry, because dry surface creates more grip naturally.
But I don't believe they are better than hard tyres, because these are made for dry surfaces.

In formula 1 the intermidiates and full wets wear out very quick if it gets dry, so I believe this happens in rally, too.


In the game, though, the tyres don't wear out extremely.
You can do a 12-long-stage event on wets without a single service area and the car is still drivable.
I believe the game just has 3 stages of tyre degredation: new, used and weared out.
And in the last stage, the tyres, any tyre, has just much less grip, but doesn't get more worse over time.

The difference between hards and wets on dry tarmac doesn't seem to be very big either.

  • Agree 1
Link to post
Share on other sites
Posted (edited)

Let's take the following example in reality

If you had to decide one day in advance/before, and for the next rally stage (8km) there was a 50% chance of rain (from the start of the race), which tyres would you rather choose?

Because I've claimed earlier loudmouthed that it should be the rain tires. But now I wonder if I have to revise that.
Dry tyres also have some profile, they are not slicks. With ordinary wetness, they are perhaps still reasonably clear? On the other hand, it is only a short stage and for rain tyres also on dry well doable?

And if the right choice is the rain tires, then the question: which choice would be the right one if the probability of rain is only 40%? Or only 30%?

Edited by PaulNbg
Link to post
Share on other sites

In principle, one could also formulate it differently: 5km of the track is dry, another 5km completely wet. But I think rain tyres are the better choice. I also forgot to take into account that soft tyres get too little temperature in the rain and are therefore not so good for wet conditions.
I guess that with 7 km of dry track and 3 km of wet track, the choice will be difficult in reality.

Link to post
Share on other sites

How slippery is the snow/ice in Monte Carlo?

LOEB onboard Rallye Monte-Carlo, minute 9:23

I ask myself, which tyres could these be?

Dirt Rally 2.0 seems to be very realistic in any case.

  • Like 1
Link to post
Share on other sites

minute 5:50 - rear soft tyres, front hard tyres
https://www.redbull.com/int-en/live/fia-world-rally-championship-2021-croatia-saturday-highlights


It is possible that a driver chooses different tires for the front and rear. But the reason was not revealed.
I always did that in Project Cars 2, soft in the rear and medium in the front, to get the sudden oversteer under control. Conversely, of course, understeer can also be quickly fixed with it. More games should therefore offer this in the setup menu.
 

Link to post
Share on other sites

TL:DR, 

anyway, from experience Rain Tyres are good on the Dry if the stage is small. The compound is even softer than softer tyres, so good grip from the get-go, however, due to the sides being too soft too, what usually happens is that you overheat the tyres very quickly especially in FWD cars. 

The medium, soft and hard compounds have more or less the same grip levels. Usually, it depends on the stage. If you do have big stages a hard tyre is required because they don't wear as much as a softer tyre. But when you have the tyres on the right temperature grip levels are the same for soft, medium and hard. The softer the compound the faster they get to temperature and the faster they wear.

 

Don't try to use the hard compound in the rain, even the soft tyre has to have crazy tyre pressures to work properly. With the hards you'll probably don't get them to temperature and you'll end up crashing due to aquaplaning.

 

The rain tyres can be used in FWD in the rear axle, in small stages as they are up to temp faster than a soft tyre.

  • Thanks 1
Link to post
Share on other sites
Posted (edited)
On 4/25/2021 at 8:39 PM, UnderclassGDfan said:


In the game, though, the tyres don't wear out extremely.
You can do a 12-long-stage event on wets without a single service area and the car is still drivable.
I believe the game just has 3 stages of tyre degredation: new, used and weared out.
And in the last stage, the tyres, any tyre, has just much less grip, but doesn't get more worse over time.

The difference between hards and wets on dry tarmac doesn't seem to be very big either.

yes true ,i hope for dirt rally 3 the game have better strategy of tyre

Edited by gk9147
  • Agree 1
Link to post
Share on other sites

(I just realized you guys were talking only about real life tires, oops! In any case, I'm going to leave this up in case anyone interested in the game's simulation of tires. If anything, you can use it to compare real life applications if you want)

Ok! Finally got around to doing this post.

First thing is, I'll be using RDA and motec to help illustrate what the grip changes look like. I'll be using a G-G diagram, which simply plots long G and lat G on a graph. In other words, it is the friction circle if you are familiar with that concept. TL;DR, any time you try to get out of this circle, you start to lose grip, and you are pulled back 'in' to the circle because you are operating now in a zone with less grip. Imagine it like you are getting to the top of the mountain, but then start heading back down again. It is in this zone where the game's oversteer/understeer physics kick in, and you have to be ready for whatever comes your way. A great driver will always be at the very edge of this graph, or at the top of the mountain so to speak. The best drivers will actually be juuust a bit past the edge of grip, as typically grip loss happens progressively rather than instantly, so there's more time to be found in pushing the car just past its limits. The reason for using a G-G diagram is because in actuality, it is quite hard in real life to accurately measure grip at any one time as the mere concept is somewhat nebulous or can mean different things depending on how you look at it. Luckily, DR2.0 is just a simulation of reality, so things are much more predictable and consistent, so it's easier to derive conclusions from the data along with in-game driving experience. The other reason is this diagram is a better measure of tracking grip change as it takes driving skill (somewhat) out of the equation. Stage times can be too vague a measure even if you are using delta Ts, especially if we're trying to measure simply car performance. If you have any questions about all this, let me know and I'll try to answer them best I can. 

First off, let's look at Spain, wet tires degradation in the Ford Fiesta MK2. This is from the recent official club championship, at the beginning of the wet stages: https://i.imgur.com/K0neCEO.png

First thing I like to look at is standing start grip, which is where the highest positive long G values are populated. This is typically the only point in a race that you start from 0 mph, and it's a good place to check what grip is available at the wheels. With the wet tires, we are looking at somewhere between 1.2 and 1.3 g's in terms of grip. As a side note, I have no idea if that corresponds with real life. I read a manual put out by Michelin that says that the coefficient of friction (CoF) for any tarmac surface is anywhere between 1.0-1.3, but that friction values in rain vary wildly. Also, this applies to road cars and not to race cars that have special tires with special compounds and circuit tracks with special surfaces that will help increase the CoF by X amount. In any case, this is what the simulation is telling us how many g's we can pull at the start line with this car on these tires.

This is what the tires look like at the end of the wet stages, on the same stage: https://i.imgur.com/kUBY2P0.png

As you can see, these are two very different looking graphs, and they feel different while driving. At this point, the car has driven about 50km worth of stages. Again, looking at our standing start, our grip is diminished - down now between 1.1 and 1.2g's. So that's a net decrease of at least 0.1 long g's.  We can also look at the straight line braking zone, which seems to suggest about a 0.2g's loss in grip (in the negative g zone). This might not all seem that much, but given that G force is felt in terms of mass (1g is equivalent to earth's gravity, so 1g on acceleration means you "feel" your whole body weight as if it was lying on top of you), if we look at the minimum weight limit of R5 of 1230kg, 0.2g's is about 246N worth of force (1230kg * 0.2g), or the equivalent of putting a 25kg/55lb cement block on your front end while braking (I'm still a bit dodgy on the math here, so let me know if I have this wrong.). 

But the REAL interesting thing to notice here is the lateral G differences, or our cornering forces. The best drivers in the world have mastered the transitions between braking, cornering, and acceleration, so that's crucial to our understanding of how we see grip. For one thing, it's a lot harder to tell what's going on in the lateral directions. It was easy to tell where the grip is during straight line acceleration and braking, but cornering things are a lot fuzzier. It gets even fuzzier on dirt stages. But we can still derive some important info on this.

For one, notice how much more densely populated the graph is. This is natural considering that we are working with less grip, but it demonstrates how much even 0.2g's loss in grip affects your driving experience. If we look at the fresh tires, we are able to throw the car around a lot more. In fact, you can see how the shape of the graph bulges out like a rectangle a lot more than the worn tires, which suggests the ability to brake and corner at the same time without losing too much grip. There might be more grip to be found at the edges, we have more of a 'buffer' zone between grip/no grip, and so on. The car 'breathes' better on the road.

The worn tires, however, give us a different story. The transition between braking and cornering doesn't bulge as much, resembling more of a circle shape so we have to be more careful while trail braking. Our buffer zone is also reduced, so we are losing grip a lot faster (this is typically why players prefer driving cars with loose suspension - it helps increase this buffer zone and it eats your driving mistakes, so to speak). And as we already demonstrated, we've lost straight line acceleration and braking so we have to adjust our expectations of the car. 

Now let's look at soft tire degradation, during the same event: https://i.imgur.com/l7VBbxU.png

The orange dots are at the beginning of the event, while the white dots are after about 53km worth of stages. Important caveat: These are two different stages so the values will not be the same and we cannot derive as many conclusions from this. For one, hills and slopes change grip levels dramatically and we cannot assume loss of grip is simply caused by wear and tear. Still, this shouldn't change standing start grip unless the car starts on an incline. So here we can see again a loss of about 0.2 g's worth of grip. I should note too, that my setup used 0 degrees toe front and rear - in real life, toe creates drag on the tire and will wear it out faster, but I have not tested that in game yet. I did have camber on the tires, but it remained unchanged during the entire event. Looking back at the graph, we see the same effect as with the rain tires - a loss of about 0.2g's worth of grip over the course of 50km. So wet or dry, tire degen is just about the same. What's interesting to note here, is that soft tires on dry tarmac start with about 1.5g's, while wet tires on wet stages start with about 1.3 thereabouts. It doesn't look like much, but it's enough of a difference for players to complain profusely about the difficulty of wet stages.

There are several other implications here as well. For instance, there is nothing to suggest tire temperature is a thing. I looked at monte carlo tarmac and spain tarmac, used the same stock Monte Carlo setup on both (only difference was ride height, by a large amount actually), and couldn't find a difference between either, really. For the curious, this is a spain stage overlayed onto the monte carlo tarmac-only stage again in the ford fiesta mk2: https://i.imgur.com/eFiJ1oh.png

White dots are monte carlo, orange is Spain. Cornering grip looks different, and that is because the Monte Carlo stage I used goes uphill, so you lose grip going uphill. There's also lots more hairpins than Spain (spain only has one hairpin, compared to Monte). But again, if we look at the standing start grip, it's identical. Temperature/elevation does not seem to have any effect.

I think that's enough for now with this post. I could try and continue testing all this by testing soft tires on wet stages, measure hard tire grip and degradation, and so on, but I think this is enough of a jumping off point for you guys if you want to see see the effects for yourself. BUT, I'm willing to bet the results will be consistent with the game's descriptions. I would love to be proven wrong though!

Edited by ManicKodo
  • Like 7
Link to post
Share on other sites
52 minutes ago, Frankiestail said:

Would love to see what, if any, difference toe adjustment makes to wear.

It's a good question, though in my every day DR2.0 driving I always go with 0 front toe and in rare cares do I use any rear toe (damn you, Porsche). To me, I'd rather just change steering sensitivity if I'm being honest. I tell myself this is ok because I consider it like adjusting the steering rate on a rack and pinion steering column so just another way to tune. 

Link to post
Share on other sites

Great use case for RDA.  👍  I think this is a good scratch of the surface (with no offense intended); the real meat and what will get most people curious is going to be quantitative comparisons of compounds over several stages.  To help people make a choice on which compound to choose when.  (of course driving style may matter)

 

The other thing that would be interesting is whether making setup adjustments can compensate for worn rubber or harder compounds at all. 

Either way, keep up the analysis. 🙂

PrxyCwZ.png

Edited by bn880
  • Thanks 1
Link to post
Share on other sites
14 hours ago, bn880 said:

Great use case for RDA.  👍  I think this is a good scratch of the surface (with no offense intended); the real meat and what will get most people curious is going to be quantitative comparisons of compounds over several stages.  To help people make a choice on which compound to choose when.  (of course driving style may matter)

 

The other thing that would be interesting is whether making setup adjustments can compensate for worn rubber or harder compounds at all. 

Either way, keep up the analysis. 🙂

 

Thank you! Indeed, I'm trying to think of other ways to do it (within the time constraints I have) but I'll just show this graph, which plots soft, medium, and hard tires on the fiesta mk2 on Spain tarmac: https://i.imgur.com/i1woGoI.png

So judging off my other graph that looks at soft tire degradation after 50km, driving on softs after that distance is about the equivalent of driving on hard tires. Performance is very noticeably bad in-game. While I have not tested the degen of medium tires, even if degradation was half of soft tires, you would be operating in about the same grip level. Now, obviously, I would have to test this - if medium tires degrade much slower than softs, anything beyond 50%, then maybe there's a case to use mediums. I believe using softs for anything up to 50km looks to be the best choice, and I'm willing to bet that is the case for any surface (so many assumptions! I'm a terrible researcher).

I'm not too interested in testing beyond this distance, as I don't really have the time to do that and it seems more relevant to custom hardcore no-service-area club events  :P. However, I am interested in testing toe angle and if that has any effect on wear as it does in real life. That could greatly influence what tires to pick if indeed toe increases wear.

In regards to setup changes, I'm still trying to figure that one out. I find the data traces for oversteer, steering angle, gps direction and heading, etc., to be quite noisy and I can't seem to judge any conclusions, other than as front direction and gps heading move away from each other, the driver needs to compensate for this with the wheel to get the car stable again. But I don't think that's really much of a revelation. I would love to figure out a way to measure how setup changes affect the speed at which the car arrives at its grip limits, but I'm not entirely certain I can with the data, or if it's really all that practical. 

Edited by ManicKodo
  • Like 1
Link to post
Share on other sites

Yeah, obviously no one is paying you to do the research 🙂  Anything more will be welcome and toe/setup wear is another interesting topic.

Experience suggests your views of compound wear are correct, but as mentioned, full data would provide new insights into WHEN it even makes sense to use mediums or hards.

Link to post
Share on other sites

it comes down to what the masses play and time. generally just soft is perfect for 90 percent of dirt rally . going deep into tyre differences is a murky thing. pcars for eg was amazing in early testing on tarmac then they tried to go full stephen hawkin on tyre simulation and literally ruined what was a great game.

data will show you data but doesnt mean when you try and apply that data it will feel right. the feel right is what really matters.

 

Link to post
Share on other sites
5 hours ago, dgeesi0 said:

data will show you data but doesnt mean when you try and apply that data it will feel right. the feel right is what really matters.

 

I believe this as well, it's my opinion that data needs to support what is happening in-game, not just relying on data points for everything. That said, I will say that my in-game experience, before I even decided to test this, coincides with what I see in the data - tire degradation has a significant impact on the car's abilities and the driver has to compensate for it. I could also go into the delta Ts and speed traces to demonstrate this point as well, but the important thing is writing down impressions of your driving experience FIRST, and then see if the data can clue you in to what is happening.

Link to post
Share on other sites
  • Social Media & Community Team
9 hours ago, dgeesi0 said:

it comes down to what the masses play and time. generally just soft is perfect for 90 percent of dirt rally .

I think the main reason for that are the stint lengths between Service areas and the general durability of the tyres in this game.

  • From anecdotal evidence Softs are good for around 30km before they drop off, Mediums 50 and Hards... who knows.
  • Most events in the game (Career, Weeklies, Monthlies etc.) are rarely more than 25-30km in terms of stint lengths, therefore Softs are typically the best choice.

This is why I set up the official Club to have 50-60km stint lengths this year.

Link to post
Share on other sites
5 hours ago, PJTierney said:

This is why I set up the official Club to have 50-60km stint lengths this year.

And I love that you did this. But sadly I don't think even with your masochistic levels of championships that we have found a use for Hards yet - or even anything but Softs outside of extreme cases. JRC Endurance I think people run Mediums on, but that is also 12x Long in a row without service stops.

Without 12x Longs, I think Soft tires are still always better than Mediums or Hards. You just lose too much time early by going with M/H types to justify their gains later in the rally. The harder compounds are still going to feel slippery too later on, just a bit less slippery at the same distance. Soft tires early can put you -10 seconds ahead of Mediums for the first few stages; the middle few stages you can see gaps of 0 to -5 seconds or so; then on the late stages you only see 0 to +5. Essentially your early stage performance on Softs is worth almost twice as much as your late stage performance on anything. The splits are just bigger on fresh Soft vs fresh Medium because once they are both worn down a bit, the Mediums can't run away significantly faster. 

This is all anecdotal evidence just from my playtime, but it has held pretty true for me. The DeltaΔ for fresh tires is larger than the DeltaΔ for worn, and by a significant enough amount that it starts to negate the latter entirely.

  • Like 1
Link to post
Share on other sites
  • Social Media & Community Team
36 minutes ago, StockTunesOnly said:

Without 12x Longs, I think Soft tires are still always better than Mediums or Hards. You just lose too much time early by going with M/H types to justify their gains later in the rally.

I think it depends on the driver.

At Greece even on the Mediums my car was just "dead" at the end of a stint as the fronts had no more grip left. I'd swing a car in for a hairpin and when I attempt to pull the Scandinavian Flick it just doesn't whip around. I'm probably harder on my front tyres than average as I use a low rotation setting, as I like the front of my car to be "pointy".

Link to post
Share on other sites
  • CMPJTierney changed the title to Tyre Wear & Physics Dscussion
2 minutes ago, PJTierney said:

At Greece even on the Mediums my car was just "dead" at the end of a stint as the fronts had no more grip left.

Oh absolutely, my Softs were completely gone by the end of the event too. But, to me at least, I highly doubt the Mediums would have felt any less "dead" by that same point - we still had to run 5x Long and any tire choice would feel slick. I was still scared to turn in sharp on super fast & narrow 5s or 6s. Mediums might have helped give you a bit more comfort and breathing room while pushing the full width of the road, but I still feel like I'd be tip-toeing around and being hesitant in spots.

I hope some people can prove me wrong in the clubs though, I would really love to see more compounds being used. Would really love to see limited tire supply in future titles too, cuz a 4 service stop rally with only 2 sets of tires is a VERY different event than a 4 stop, 4 tire set rally.

  • Agree 1
Link to post
Share on other sites

Yeah, I like the idea of a limited set of fresh tires.

I also think it would be interesting if the developers played around with the degradation curves, so that they aren't just linear. Softs would have the sharpest curves, while medium and hard would respectively have shallower curves. You could even tie wear to degrees of slip (not exactly sure how that is calculated in the physics engine), but I don't think it needs to be too complicated to introduce enough variation to start being an important part of tire selection. You don't even have to calculate it in real time necessarily. That way, the heavy drifters will burn through tires a lot quicker than those who are more careful with their driving inputs. Have some kind of fun feature in-between stages like Phil commenting "the tires took a beating that run" or something like that. Keep it vague enough that the player at least knows their tires are going.

It just needs to be such that the tire strategy is tied to something else, not just stage distance. Watching the Croatia rally, Neuville and Hyundai team really screwed their chance at an event win due to tire choice and you don't need much to mimic that kind of situation. Except play testing time 😬

Link to post
Share on other sites
  • Social Media & Community Team

I'm sure I read somewhere that how you drive the car does have a minor effect on the tyre wear. For example, if you light up the rears through every turn they'd be shot earlier than a normal drive.

Link to post
Share on other sites
3 hours ago, PJTierney said:

I'm sure I read somewhere that how you drive the car does have a minor effect on the tyre wear. For example, if you light up the rears through every turn they'd be shot earlier than a normal drive.

Can confirm this, but don't have the quote ready. I remember specifically asking a dev about this after launch and being told how you drive definitely impacts the wear.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...