Official 2016 Brazilian Grand Prix Thread ***SPOILERS***

You also have to remember that when you're hearing the likes of Verstappen saying "it's ready to go" that he has far more downforce than the cars lower in the pack. It's very different for some of the other drivers in worse cars. Hamilton was saying the same and he had more downforce and a clear track. It was only really Magnussen towards the rear who was being brave on the radio in terms of what was broadcast.

The Massa pit walk was tear-jerking. I know he's not the most loved driver among some fans, but it's hard to understand why when he's so loved among the paddock, and everyone who talks about him says the same. What a response.

The race itself obviously interesting. Verstappen was indeed very good, but I'm not about to say it was a great performance - he was on 20 lap fresher tyres than most others - he did destroy Ricciardo in the same conditions though. This wasn't his Barcelona 96 like some have claimed - it wasn't even in the same league. He was the only one really scouting lines behind the safety car, checking this and that.

I have to say I was more impressed with Nasr (he started last!), Ocon (3rd last!) and especially Sainz (15th!). What races! If it was still 2014 and it was Verstappen in P4 for much of the race we'd have been creaming ourselves, yet Sainz seemed to get sod all mention in the British commentary or online afterwards.

McLaren was extremely disappointing. These were the conditions you'd have expected them to make the most of and mix it up behind the podium finishers, yet they had no pace all race. I know Button said he couldn't switch either tyre on (and he is clearly counting down the days), but Alonso wasn't much better. I think most McLaren fans were consoling themselves that at least the aero is good, but yesterday showed they're still a long way behind in all regards. Williams once more spoiled the race for themselves, and while Red Bull made the same mistake they at least did something about it - Williams just kept Bottas out there and crossed their fingers.

Laton Wrote:
-------------------------------------------------------
> This is bollocks.
>
> When will people learn that heavy rain didn't kill
> Bianchi. An open cockpit didn't kill Bianchi.
>
> It was a tractor that killed Bianchi. We have
> sorted this out.
>
>
>
> Why can't we go racing?

A head-on crash could have done it though ...

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X (@ed24f1)

We also have to accept rightly or wrongly that in today's society it's less and less socially acceptable to put people at high risk especially for something which is a sporting activity.

Over the years F1's drive towards safety has been staggering.. it's risk management is effectively second to none.

Yes.. on occasion it saps much of the excitement out of it. But they can't exactly go back on things now because of the litigation involved in the event of when someone does get badly hurt or worse.

I don't see next year being massively different in wet conditions.... cars will still aquaplane in puddles.. race control will still be conservative. The only real difference will be the reduced visibility due to wider tyres displacing more water into the air. Possibly increasing the risk of cars accidentally tapping the white painted lines and hence spinning off.

We'll get more wet standing starts though.. as they've changed the rules. When the safety cars in the cars will do a standing start.

Alex Wurz made some comments on the heavy wets yesterday. Basically he said that the main disadvantage is a relatively hard rubber compound. The reason for this is not a lack of tyre testing or Pirelli being too conservative but the tyre allocation for the weekend. Apparantly teams have only four (iirc) sets of heavy wets for the whole weekend. If the tyres were less durable teams would run into problems in case of a completely wet weekend.
Concerning tyre pressures, he said pressures are quite high for the wets (almost balloon shaped tyres) as it is preferable to have a small area of contact.

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used to be GPGSL's Nick Heidfeld

Quote
n00binio
Concerning tyre pressures, he said pressures are quite high for the wets (almost balloon shaped tyres) as it is preferable to have a small area of contact.

I thought the main reason for high pressure in the wets was to open the tread block more.

Might also play a role, depends on the amount of water on the circuit i guess. If i remember correctly he stated that the tires could in principle displace a lot more water than what we had on sunday so the tread was probably not the decisive factor, at least this time.

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used to be GPGSL's Nick Heidfeld

I don't think the tyres are any worse than they used to be honestly.

Just look at races like Suzuka 1994, Australia 1989, Brazil 2004 and more recently the Nurburgring in 2007.

I think it's just modern drivers expect more from them.

gav Wrote:
-------------------------------------------------------
> > Concerning tyre pressures, he said pressures are
> quite high for the wets (almost balloon shaped
> tyres) as it is preferable to have a small area of
> contact.
>
>
> I thought the main reason for high pressure in the
> wets was to open the tread block more.


It is. Nobody in their right mind would ever want to reduce the size of the contact patch on a race car. When the water is displaced, the contact patch IS what you have to work with when it comes to acceleration, braking and cornering. It doesn't do you any good to reduced the contact patch to prevent aquaplaning, if you are dead slow on the rest of the tracks, where there are no puddles.

To explain it in an easy way, go get a hair brush, one of those that look like the back of a porcupine. When you push down on that with a flat hand, you will see the "tyre" construction bend down, and as a result, the pins (tread) in the brush move towards each other. That is what a wet tyre does, and that is why you want it slightly overinflated. When you release your hand, then the pins move away from each other again. That is when the tyre is throwing water up in the air, and making itself ready for another rotation.

If the tyre is overinflated to the point of being a ballon, it cannot deliver this flex, and you hinder it in working as designed.

The thing that cuts the surface tension of the water is not a small contact patch, but sharp edges in the tread itself. This is also why a worn wet tyre, that has enough tread to remove the amount of water it encounters can still aquaplane, because the edges have been worn.

Overinflating the wet tyre to reduce the contact patch, is a trick in karting. You also get the advantage of heating up the tread where the contact patch is a lot, because it is working overtime to handle your inputs. But karts are very different from F1 cars, especially considering downforce. You don't have downforce at F1 levels in karting to mash the tyre into the water, thus it is a trick that works. In F1, all you get is a wet tyre that overheats in the area of the contact patch, hence you risk blistering and wearing out the edges of the tread. You do not want that.

Go back to the discussions in 2014, in the Bianchi aftermath. You can find both Vettel and Hamilton pushing for better wet tyres from Pirelli, because part of the accident was that inters where just much better to use, because the wet window was too narrow, considering track wetness. What was the response from Pirelli? Additional treads and reworking the design, leading to an increase of 15 liters of displacement per second, to the current 65. They never mentioned making them any harder (or softer), nor regulating tyre pressure.

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It's only after we've lost everything, that we are free to do anything.



Edited 3 time(s). Last edit at 11/16/2016 03:01AM by Morbid.

Ok, I looked into the whole topic today. I am by no means a tyre expert but I guess I can sort of do an educated guess (not just quoting Wurz, lazy me).

First aquaplaning: as soon as the road is wet aquaplaning can happen. This is not just a question of whether there's a puddle or not, it also depends massivly on speed and the geometry of the tyre. If there is very little water the speed at which aquaplaning begins is obviously higher but it will start at some point. On the other hand a wider tyre will experience aquaplaning sooner than a thin tyre. E.g.: a typical bicycle will start aquaplaning in standing water somewhere around 70 kph whereas for a car in a similar situation half of the speed can be too much. By the way this similar the reason why rallye teams fit thinner tyres for races on snow.

What's the reasoning here? Aquaplaning happens when the tyre can not move the water out of the way fast enough and starts to run on a thin layer of water. Here two forces are at play. The water exerts a force on the tyre which is mainly caused by inertia of the water. The tyre exerts a force on the water which is given by the weight of the car divided by the area of contact (units don't add up but you get what is meant). If the car moves faster the force exerted by the water increases due to the fact that more water has to be displaced per time. If you make the car heavier or shrink the area of contact the force exerted by the tyre will increase. The tyre tread will influence the amount of water than can be displaced and decreases the force exerted by the water.

So if you want to fully avoid aquaplaning you would try to fabricate a tyre that exerts a higher force than the water in all sensible conditions and that shifts the minimum aquaplaning speed to a high value. As making the car heavier is not practical it's all about area of contact and tread. See the bicycle and rallye car example. And actually Morbid is spot on when mentioning the sharp edges of the tread. Edges are localized areas of high force exerted by the tyre and will thus help avoiding aquaplaning.

It's clear that we can also decrease the are of contact by increasing the tyre pressure. The only data I found on this was that the speed of beginning aquaplaning increases with the square root of tyre pressure. So higher pressure = later aquaplaning.
If you go for maximum performance (F1) the truth will be somewhere in between, it's a compromise between avoiding aquaplaning and good grip on less wet parts of a track. The pressures I have seen so far suggest that the tyre pressures are higher than for dry conditions. Imo that's plausible.

What I don't get is your description of the tyre tread closing (?) and opening again while throwing out the water collected in the tread blocks. Maybe I'm misunderstanding what you were saying but this sounds odd to me. I didn't calculate it (too lazy, again) but I would guess that the movement/reshaping of the tread blocks is fairly small due to the low ratio of tread depth vs. wheel diameter. Imho what you want is displacing the water to the side of the the tyre at the area of contact as this costs next to no energy. Looking at the tread geometry this seems to be the intended effect. Spray seems to be just a suction effect, essentially glueing the car to the ground. Breaking this effect and throwing out the water is a massive waste of energy as the energy needed for this is taken out of the roation of the wheel. Same as a diffusor actually, I'm pretty sure that a diffusor (the whole undertray) performs worse in wet conditions.

tl,dr: you do want to increase tyre pressure in the wet, not to infinity but surely above dry level. And this doeas indeed wear out the tyres pretty fast if there's not enough water around but that's exactly what were observing.

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used to be GPGSL's Nick Heidfeld

n00binio Wrote:
-------------------------------------------------------
> What I don't get is your description of the tyre
> tread closing (?) and opening again while throwing
> out the water collected in the tread blocks. Maybe
> I'm misunderstanding what you were saying but this
> sounds odd to me. I didn't calculate it (too lazy,
> again) but I would guess that the
> movement/reshaping of the tread blocks is fairly
> small due to the low ratio of tread depth vs.
> wheel diameter. Imho what you want is displacing
> the water to the side of the the tyre at the area
> of contact as this costs next to no energy.
> Looking at the tread geometry this seems to be the
> intended effect. Spray seems to be just a suction
> effect, essentially glueing the car to the ground.
> Breaking this effect and throwing out the water is
> a massive waste of energy as the energy needed for
> this is taken out of the roation of the wheel.
> Same as a diffusor actually, I'm pretty sure that
> a diffusor (the whole undertray) performs worse in
> wet conditions.

The movement of the tread doesn't have to be big, it just has to be enough to cleverly both exploit surface tension and to break it. The problem with water is that it IS a liquid. This means it is constantly generating surface tension everywhere. So, if you slow things down enough, it acts like syrup.

A contact patch is just that, actual contact between tyre and tarmac. So there is no need to drain water away from the patch itself, as if there was water between the contact patch and the tarmac, you would already be riding on water, and be aquaplaning. This means, that due to contact between tyre and tarmac, water is constantly pushed away, and that is in FRONT of the tyre.

You can replicate this, with a bit of water on a table and your hand. If you move your finger towards the water, exposing the length of it, you will push it in front of your finger, even though there are wedges below your joints where it could escape between. Move that finger really fast, and you will fling the water in along in front of you. Even if your finger is not in full contact with the surface of the table, you will STILL be pushing water in front of your finger, even though some of it escapes between your finger and the surface.

Thus, the quicker the tyre is moving forwards, even IF you constantly break surface tension with the tread, the more water will be pushed in front of it and it will build up a larger and larger wave in front of it. This wave if allowed to grow too big, will induce aquaplaning, when the tyre lifts up over it. That is when you are literally "riding on water".

When the tread is "open" before contact, and cuts surface tension, some water will be forced into the tread from the wave. When the tyre hits the tarmac and comes under weight the treads come together, narrowing the groove. Since the water cannot go down, it can only go where there is room to do so. That is, following the tread pattern, or deeper into the grooves.

Example: if you have a straw and you dip it in water, and then place a finger on top, and lift it out, you have water trapped inside the straw. If the water was to drop out, it would make a low pressure area in the straw below your finger. Due to your finger, air cannot enter from the top. It is surface tension of the water, that prevents air from entering at bottom of the straw and equalizing that low pressure at the top, and hence the water dropping out. How can we manipulate this?

Well if you grasp the straw at a part below your finger and mash it where there is still air, you use the air pressure to break the water tension and push water out. If you put a finger at the bottom of the straw, remove the one on top, and then mash the lower part of the straw, you are pushing water UP the straw. With enough of the straw collapsing, water will eventually escape at the top. If the straw had a trumpet shape in the bottom, the effect would be much more pronounced. That is what the action of the expanding/contracting tread is doing.

So, to explain, there are basically two types of treads on a wet tyre (oversimplification). You have treads that run around the circumference of the tyre, and you have treads the run lateral to the tyre. The treads that run the circumference of the tyre drain the wave made in front of it, and also acts as storage and transportation system. When that tread narrows the groove on contact with the tarmac (due to load weight+downforce), it pushes water DEEPER into the groove, and along the route of the groove. This brings us to the lateral treads, where the water is displaced too. When the tyre rotates enough that a certain section does not act as a contact patch any more, it is not under load. Then the groove opens up again - THAT PULL along the surface of the water in the groove helps break the tension, letting centrifugal force sling it away from the tyre, and thus not only is spray created, the tyre is drained and ready for another cycle.

You can see this in action on the pictures below.






Notice the fact, that these are cars that both use downforce and do not use downforce. Both are making spray, and you can clearly see the action of the tyres flinging the water into the air. You can even see the flinging action from the FRONT tyre of the non downforce car. And you have to agree, that these wet tyres are probably a lot worse than what F1 cars have today.

While it is true, that undercar downforce of any kind, and especially the diffuser, and even just the low pressure area behind a car that creates drag will create spray, they are NOT alone in doing this. In the wet though, this massive vacuuming action will help a lot to dry a track for each lap run.

> tl,dr: you do want to increase tyre pressure in
> the wet, not to infinity but surely above dry
> level.

That's it. Shot from the hip, I would say maybe 20% from dry conditions (I know some semi-amateur racers use this range, although it might NOT translate to F1). This is not only because of how the wet tyre interacts with water, but also due to lower stress on the tyre not heating it as much, and water constantly cooling it. Using the tyre raises temps, and hot air expands, so dry tyres would see a larger pressure increase than wets.

What we have to remember, is that Pirelli has already mandated a large increase in tyre pressure on dry tyres to combat the torque of the electric engines ripping them apart. That increase has been described at numerous races as overinflation. So I reckon, they have already tapped out that 20% increase. I doubt the construction of the wet tyre is any better at dealing with the torque problem. So, I THINK (as in do not have solid evidence) that the wet tyres are already inflated beyond the optimal point, just to help keep them together (rendering Wurz statement factually correct, but the reasoning wrong). And to return to the original point of debate, wider tyres will be a lot better at handling this torque. Thus pressures can be reduced. Which would put the wet tyre back into it's operational window.

That is my take on WHY the wider wet tyres will be better, even though they theoretically should be worse. Added to that, you will probably see the intermediate tyre being used more in drying conditions, because the wider dry tyre will be worse in those conditions.

---

It's only after we've lost everything, that we are free to do anything.



Edited 8 time(s). Last edit at 11/17/2016 01:58AM by Morbid.

Morbid schrieb:
-------------------------------------------------------
> The movement of the tread doesn't have to be big,
> it just has to be enough to cleverly both exploit
> surface tension and to break it. The problem with
> water is that it IS a liquid. This means it is
> constantly generating surface tension everywhere.
> So, if you slow things down enough, it acts like
> syrup.
>
> A contact patch is just that, actual contact
> between tyre and tarmac. So there is no need to
> drain water away from the patch itself, as if
> there was water between the contact patch and the
> tarmac, you would already be riding on water, and
> be aquaplaning. This means, that due to contact
> between tyre and tarmac, water is constantly
> pushed away, and that is in FRONT of the tyre.
>
> You can replicate this, with a bit of water on a
> table and your hand. If you move your finger
> towards the water, exposing the length of it, you
> will push it in front of your finger, even though
> there are wedges below your joints where it could
> escape between. Move that finger really fast, and
> you will fling the water in along in front of you.
> Even if your finger is not in full contact with
> the surface of the table, you will STILL be
> pushing water in front of your finger, even though
> some of it escapes between your finger and the
> surface.
>
> Thus, the quicker the tyre is moving forwards,
> even IF you constantly break surface tension with
> the tread, the more water will be pushed in front
> of it and it will build up a larger and larger
> wave in front of it. This wave if allowed to grow
> too big, will induce aquaplaning, when the tyre
> lifts up over it. That is when you are literally
> "riding on water".
>
> When the tread is "open" before contact, and cuts
> surface tension, some water will be forced into
> the tread from the wave. When the tyre hits the
> tarmac and comes under weight the treads come
> together, narrowing the groove. Since the water
> cannot go down, it can only go where there is room
> to do so. That is, following the tread pattern, or
> deeper into the grooves.
>
> Example: if you have a straw and you dip it in
> water, and then place a finger on top, and lift it
> out, you have water trapped inside the straw. If
> the water was to drop out, it would make a low
> pressure area in the straw below your finger. Due
> to your finger, air cannot enter from the top. It
> is surface tension of the water, that prevents air
> from entering at bottom of the straw and
> equalizing that low pressure at the top, and hence
> the water dropping out. How can we manipulate
> this?
>
> Well if you grasp the straw at a part below your
> finger and mash it where there is still air, you
> use the air pressure to break the water tension
> and push water out. If you put a finger at the
> bottom of the straw, remove the one on top, and
> then mash the lower part of the straw, you are
> pushing water UP the straw. With enough of the
> straw collapsing, water will eventually escape at
> the top. If the straw had a trumpet shape in the
> bottom, the effect would be much more pronounced.
> That is what the action of the
> expanding/contracting tread is doing.
>
> So, to explain, there are basically two types of
> treads on a wet tyre (oversimplification). You
> have treads that run around the circumference of
> the tyre, and you have treads the run lateral to
> the tyre. The treads that run the circumference of
> the tyre drain the wave made in front of it, and
> also acts as storage and transportation system.
> When that tread narrows the groove on contact with
> the tarmac (due to load weight+downforce), it
> pushes water DEEPER into the groove, and along the
> route of the groove. This brings us to the lateral
> treads, where the water is displaced too.

Yeah, that's what I had in mind as well, maybe my wording was a bit too sloppy. But yes, agreed. (except for the water / syrup comparison: this property is called viscosity and not really related to surface tension, but not important here, I get your point)

> When the
> tyre rotates enough that a certain section does
> not act as a contact patch any more, it is not
> under load. Then the groove opens up again - THAT
> PULL along the surface of the water in the groove
> helps break the tension, letting centrifugal force
> sling it away from the tyre, and thus not only is
> spray created, the tyre is drained and ready for
> another cycle.

This is the only thing that I do not see. Imo the draining of the tread is purely centrifugal force. Surface tension is not broken here, it just dictates the shape of a water droplet. The area of the water/air interface is minimized due to surface tension. If I understand correctly what you're saying the tread would have to pull the water surface in such a way that it would shrink the water/air interface if the water transforms into a drop. I can't see this happening but I haven't found any numbers on that so who knows. Imo it's just centrifugal force, nothing more. But it's a minor point really.

>
> You can see this in action on the pictures below.
>
>
> [i68.tinypic.com]
>
> [i68.tinypic.com]
>
> Notice the fact, that these are cars that both use
> downforce and do not use downforce. Both are
> making spray, and you can clearly see the action
> of the tyres flinging the water into the air. You
> can even see the flinging action from the FRONT
> tyre of the non downforce car. And you have to
> agree, that these wet tyres are probably a lot
> worse than what F1 cars have today.
>
> While it is true, that undercar downforce of any
> kind, and especially the diffuser, and even just
> the low pressure area behind a car that creates
> drag will create spray, they are NOT alone in
> doing this. In the wet though, this massive
> vacuuming action will help a lot to dry a track
> for each lap run.

Maybe again my wording is at fault here but I did not try to convey that only the undercar is creating spray, I'm aware that most of it is caused by the tyres. My point was that the spray caused by the wheels will acutally slow the car down and that a wet track will decrese the efficiency of the diffusor.

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used to be GPGSL's Nick Heidfeld