Oscar Piastri said he never had any concerns about his McLaren’s legality after his dominant Miami Grand Prix victory prompted speculation over their car.
McLaren acknowledged the rumours around how they sustained good performance from their tyres during the weekend. Zak Brown, McLaren Racing’s CEO, was seen drinking from a bottle labelled “tyre water” on the pit wall.Piastri led a crushing one-two for the team in the race, finishing well over half a minute ahead of McLaren’s closest rival.
His car was selected for post-race checks by the FIA. These selections are made at random, according to the regulations, and Charles Leclerc’s Ferrari was also chosen.
“All inspected components were found to be in conformance with the 2025 Formula One Technical Regulations,” the FIA noted.
Piastri said he paid no attention to stories questioning the legality of McLaren’s MCL39.
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“I honestly haven’t read anything because I’ve not been concerned,” he said. “Maybe next time we’ll put some little figurines in a water slide as well, I don’t know, we’ll come up with something.
“But clearly it’s all been passed. I had no concerns, play on.”
The car belonging to his team mate Lando Norris was also selected following the Japanese Grand Prix last month. The FIA also passed his car after testing various parts of its electrical systems.
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2025 Miami Grand Prix
- Nothing for Ferrari to learn from Miami team orders episode – Vasseur
- Hamilton proud of Ferrari as ‘we’re taking a beating from media and people’s comments’
- McLaren legality never in doubt says Piastri as FIA’s post-race check clears car
- Albon did not disobey team orders in Miami says Vowles after Sainz’s complaint
- McLaren score their most emphatic win since Hamilton’s 2008 Silverstone triumph
pcxmac (@pcxmac)
15th May 2025, 18:27
I dunno about all the hoopla being talked about their braking system. Maybe if they were using the spindle as a compressor and they have a ‘fridge’ setup for rim, somehow… The phase change stuff ? maybe if it was being used as a way to switch the flows, from heat the tire, to cool the tire and vice versa. I can’t see that stuff cooling anything directly unless they are pulling electricity from the battery w/ Peltier devices (PCM). But that didn’t seem to be discussed in the theory. Just a lot of nothing burger.
Most likely Pirelli are handing McLaren tires with different chemical specifications / process-recipes. Tires that don’t break apart as easily because they are not say like contaminated, or manufactured in such a way the molecular bonds are less susceptible to thermal loading, where the point of equilibrium requires more heat.
Until F1 starts doing serious lot control, the customers get to keep the tires (IE, Pirelli does not keep any tires used on any F1 or Test Car) and doing a lottery for the tires, I suspect you will see a lot of people go from hero, to zero in the low speed turns (where the coefficient of friction for the surface of the tires is a more significant player in turning a car).
Pirelli should have a mule car, their own, whose suspension configuration, setup, weight distribution is standardized by the competitors in F1, and are open to the public. All testing that Pirelli does should only involve it’s mule car/factory test equipment.
Currently it is too easy for Pirelli to develop tires for one particular car’s setup/rear end, weight distribution, loading characteristics/profile. And if teams like Red Bull are serious about getting down to brass tax w/ respect to the tires, they need to seriously limit what Pirelli can see, and seriously increase the transparency of Pirelli’s production process.
Coventry Climax
15th May 2025, 18:39
Oh, come on!
Ever heard of centrifugal force? Happen to know the formula and how it’s related to (cornering) speed?
One more question, and then you can go look up the answers:
Which force is it, you think, keeps any car on track in any corner, any speed, anyway?
(Hint: scan what I quoted from you.)
Coventry Climax
15th May 2025, 18:43
Absolutely agree with the rest of it though.
Not that you said anything in that regard, but that is an aspect that the FiA should tackle and for once, exceptionally, can’t be blamed on Pirelli solely.
pcxmac (@pcxmac)
16th May 2025, 6:09
at lower and lower speeds, the tires and suspension (things like camber) play a much more important role in cornering. Sure there are different lines you can uses, different engine braking maps, differential setups, tricks and finesse moves you can use to oppose the ‘outward’ force you refer to. But to be honest, …
Max’s own testimony about the tires and low speed cornering, mirror what Lewis has been dealing with. And when teams go from god like pace to near midfield in one race, I don’t think that’s anything to do with the car myself. It’s just statistically impossible IMO. Especially when it’s timed exactly with their star engineer departing. It just reeks of narrative management by the big wigs, who are using simple ploys like tires to control the racing.
RBR are a great team, Merc had great pace, all went down the shooter at certain times where it was beneficial for the guys running the show. Also McLaren’s rise during it’s ascent in valuation during it’s trade to CYVN/Mum-something or other, it just smells really bad. The only thing I see acting in McLaren’s got better tire management theory is they seem to have far superior tire grip in colder/damp conditions, probably because they are better at turning the heat on to their carbon fiber drums and radiating it out to the wheel. But to be honest, in warm conditions I don’t think McLaren have anything better in terms of cooling, perhaps they are u sing PCM to switch venting profiles. But I honestly think McLaren’s success has more to do with Wolff giving them better power units and Pirelli giving them better tires.
pcxmac (@pcxmac)
16th May 2025, 6:17
more power/efficiency = more down force at same or better speeds, especially with flexi wings.
Also, if I were McLaren I would have a trick compressor coming off the spindle feeding in to a vortex tube, w/ PCM flow switching. Not sure if that would add much to rolling resistance. But as far as cooling and heating solutions it might be a lot better, and it might be what RBR are seeing with the super cool air.
you would get very hot air (for heatup, or dump-at-temp), cold air (cool down, dump-on-too-cool), and air in (from a compressor, probably geared to achieve significant RPM. Im not sure what kind of thermal loading requirements need to be met, so it might actually be pretty unfeasible.
McLaren still have trouble following other cars, which means they are still pretty limited on their cooling though. I would think.
Alesici
16th May 2025, 9:17
I don’t know what Coventry Climax is on about. Centrifugal force doesn’t exist. The tyres’ friction creates centripetal force, accelerating the car towards the inside of the corner. Pcmax’s point that tyres are more important than other things (e.g. downforce) at low speeds than at high speeds is valid. (Though I’m convinced about his theory of collusion with Pirelli.)
It’s worth understanding that there is no fixed coefficient of friction. For example, it reduces with increasing download. That’s why it’s important to have a light car and also one with a low centre of gravity, so that no individual tyre is relatively overloaded.
Pcmax may be misunderstanding the aspect of phase change materials (PCM) that is beneficial. It’s not for redirecting the flow to control the direction of heat transfer – that’s probably done with something like a bimetallic strip (which works on the basis of relative thermal expansion). The benefit of PCM is that it retains a constant temperature during the phase change, limiting extremes of heat transfer from the brake drum to the tyres and back again. It might be a solid-gas phase change to get around the ‘no liquid cooling’ rule, but is much more likely to be solid-solid (involving a change in crystalline structure) whose weight is retained throughout that race.
Tony Mansell (@tonymansell)
16th May 2025, 12:14
Ive accidentally clicked on racecar engineering !!! Interesting stuff but feels a bit word salady bearing in mind no one on here has talked about ‘phase change’ till this week and suddenly we’re being told why it wont work/works differently
Alesici
16th May 2025, 13:47
Note I meant to say I’m NOT convinced by Pcxmax’s Pirelli collusion idea.
anon
16th May 2025, 16:07
@tonymansell it’s come about because a particular Youtuber, who happens to work in motorsport and produces videos about Formula 1, started pushing the theory that McLaren were using phase change materials, or PCMs, to control the rate at which heat was radiated from the rear brake disks to the wheel hub.
That video led to some rather fevered speculation in some quarters that McLaren had found some sort of special silver bullet – some of it coming from people wanting to make it sound like some sort of ultra-exotic solution, whilst others might have had an axe to grind and wanted to claim McLaren were cheating by using that sort of solution.
The reality, as some of the more sober outlets have pointed out, is that it’s not a case of McLaren employing the sort of exotic solution that makes for a dramatic headline. Instead, it seems to simply be that McLaren chose to commit more of their time into modelling the airflow through the rear brakes and coming up with a more sophisticated way of managing the airflow than anybody else has.
As you can see from the way that several other posters are reacting, given it’s also a rather prosaic and unexciting answer, they’d rather speculate about an answer that is wrong, but more dramatic sounding, than one that is much more likely to be true, but also not particularly exciting.
Coventry Climax
17th May 2025, 1:05
That’s a lot of words and they completely miss the point.
If it weren’t for friction, you wouldn’t be able to keep a car on the road – any road – and you wouldn’t even be able to accelerate or brake either. Try slicks on ice and you know what I’m talking about.
In order to stay on the road, and neither slide outwards or inwards, the force that drives you inwards, (centripetal) needs to equal the force that drives you outwards (cerntrifugal). (Just like lift needs to equal gravity in order for a plane to stay up.)
The outwards driving force depends on the square of the speed, the radius of the corner and the ca’s weight, but it’s obviously quite safe to assume that the weight stays the same.
So the amount of friction needed to go through corners at higher speeds, is much higher than what’s needed to go through corners at low speeds.
In a corner, weight shifts to the outsuide of the car, due to the fact that the CoG is above ground level. That puts extra weight on the outside tyres, generating extra friction. Inside though reduces, for the exact same reasons.
The extra friction needed for highspeed cornering is created by increased downforce only, generated by aero configuration and exactly that: higher speeds.
But regardless: All of that friction still comes from the contact patches of the rubber on the tarmac and it’s only that which keeps the car on track.
So ‘Oh come on’ means to say there’s no such thing as a coefficient of friction and it being bigger at low speed corners.
What is true, is that in low speed corners, the friction is determined by the weight of the car, the rubber compound, the tyre pressure (size of the contact patch), ‘roughness’ of the tarmac, radius of the corner and the (low, but still squared) speed only, as there’s no downforce to help create any extra.
Coventry Climax
17th May 2025, 1:09
@pcxmac
@tonymansell
anon
and
alesici,
obviously
Coventry Climax
15th May 2025, 18:31
Top notch modern F1 scrutineer on the job:
Weight – Check Wait, was that scale calibrated? Pounds or kg? Oh well.
Floor – Check Can’t really reach all the way down there, but I think it’s OK.
Rearwing – Check No, I’m not gonna lift 20 kg just to check that. Can’t get my finger in there now, so should be OK. Besides, MBS said it was supposed to be OK, so all fine.
OK, great passed. In just 4 days, must be a new record.
Hey Oscar! Family OK? No, no issues here.
Fuel sensors, darn, darn, darn, forgot the fuel sensors. Oh well. Don’t really understand those anyway.
Ferdi
17th May 2025, 6:43
Ofcourse, just look at the number of stakeholders in all of this that are invested in McLaren succeeding. I would not have expected any other outcome of these tests.