Pls explain reason for tyre pressure regulation

I'm obvioulsy a daft, old fart. Used to race several years back in the seventies. Still addicted, watching every race I can find on internet and TV. Quite a techie and as a web devloper, pretty OK with today's remote controlled digital settings.

But I simply can't wrap my head around this tyre pressure regulation. Ever since motorcycle racing started, it's been up to the rider/team himself/themselves to pump up tyres to their liking. Except from Barry Sheene's crash during Daytona practice 1975, I can't recall that any accidents ever happened due tyre pressure. (And Sheene's crash wasn't really due pressure as I recall, but to the centrifugal force in that high speed made the rear tyre expand).

Can someone enlighten me?

Cheers
Dani

It is because Michelin cannot design tyres for ..... Their last update was 2018 I think, and the aero loads have increased significantly to the point where the tyre wall is deforming to dangerous levels (i.e. causing a failure). Unfortunately, because they have to run a higher pressure now, this exacerbates climbing front tyre temp, which in turn increases pressure, which in turn increases tyre temp in a never engine cycle.

Michelin are supposedly developing a new tyre for 2025 or 2026, but in the mean time, they enforced a minimum pressure rule.

#22 said:

It is because Michelin cannot design tyres for ..... Their last update was 2018 I think, and the aero loads have increased significantly to the point where the tyre wall is deforming to dangerous levels (i.e. causing a failure). Unfortunately, because they have to run a higher pressure now, this exacerbates climbing front tyre temp, which in turn increases pressure, which in turn increases tyre temp in a never engine cycle.

Michelin are supposedly developing a new tyre for 2025 or 2026, but in the mean time, they enforced a minimum pressure rule.

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When I was racing (ancient times), Michelin was best.

Regardless:

Partially 1, and as I understand, Pirelli is the tyre sponsor 2024.
Partially 2: it's always (well, until Dorna/FIM decided to get one manufacturer per season) been up to riders/teams to pick whatever tyre and pressure they wanted.

It's part of the racing. During umpteen practices and whatnot, before and during season, the rider and the teams have gazillions of options to e.g. selct tyres and tyre pressure. What's the big deal? If Joe like 25psi and Buddy prefer 35, who cares?

Sorry, as I wrote above, I'm an old fart. Still not used to the fact that marketing people and other dimwits are doing their best to transform motorcycle racing into sheer entertaiment (money, money, money...)

Cheers
Dani

Danne said:

When I was racing (ancient times), Michelin was best.

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Michelin were mainly the best back in the day when they had pretty much a monopoly on MotoGP, and for European rounds could make tyres overnight on Saturday based on data gained during the weekend thus far, and ship them to the track for Sunday morning. They are known as 'Saturday night specials'

When Bridgestone came into the sport in 2005, they quickly overcame the Michelin dominance.

Danne said:

Regardless:

Partially 1, and as I understand, Pirelli is the tyre sponsor 2024.

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Incorrect, Dorna agreed an extension of the Michelin partnership in 2021 to extend to 2026

Danne said:

Partially 2: it's always (well, until Dorna/FIM decided to get one manufacturer per season) been up to riders/teams to pick whatever tyre and pressure they wanted.

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In the days before control tyre, you are correct. But there has been a control tyre in MotoGP since 2009. First, Bridgestone, followed by Michelin in 2016.

Danne said:

It's part of the racing. During umpteen practices and whatnot, before and during season, the rider and the teams have gazillions of options to e.g. selct tyres and tyre pressure. What's the big deal? If Joe like 25psi and Buddy prefer 35, who cares?

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As you noted above, control tyres have eliminated the options and variety teams and riders used to have.

Now any variation is cited as a 'safety issue'

Danne said:

Sorry, as I wrote above, I'm an old fart. Still not used to the fact that marketing people and other dimwits are doing their best to transform motorcycle racing into sheer entertaiment (money, money, money...)

Cheers
Dani

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Welcome to the forum!

Moto2 & 3 are Pirelli tires

It's an insurance policy for marketers and underwriters. Michelin doesn't want their tire delaminating during the races. They remember that bad old days with Vale slagging them for building tires that worked better for the Honda than the Yamaha. Rossi had issues with tire degradation during the 2006 and 2007 seasons.

The insurance underwriters also want the rule. They aren't paying claims for riders who get killed or injured when their tire explodes. Shinya Nakano tempted fate when his tire exploded on the front straight at Mugello. The current bikes put too much pressure on the front tire, and it was never designed to work with aero bikes, as it was supposedly designed before the pandemic. Michelin don't want to build a new tire, and with a new formula incoming for 2027, it might not be worth their while.

If a tire explodes, it could take out multiple riders, and the series as a whole would suffer, so I get the rule. Back when I worked in racing, we were constantly making tire pressure adjustments and taking tire temp readings, every track was a little different. We would always start with a baseline, usually the tire company would give you pressures for a specific tack and we would make our own pressure adjustments from there. We never really had to deviate to far from the recommended pressures. So my guess would be that one of these teams were pushing the limits of these tires during testing, trying to get the tire to perform in a way that it was not designed, and that is why it became an issue.