Why MotoGP records don’t get smashed any more

Such is life in the 21st century. In the good old days, motorcycle racing was a glorious free for all, when no one worried about riders or bikes going too fast because there was no such thing as too fast.

In the earliest days of the sport – 120 years ago – only one factor was considered in separating different racing classes: machine weight.

Engine capacity classes were the next phase in regulating racing. Then in the late 1960s things started to get out of hand – Honda built a five-cylinder 125cc four-stroke and Suzuki created a three-cylinder 50cc two-stroke – so each grand prix category was further regulated with limits on the numbers of cylinders and gears.

Now hundreds of limits apply to each class, both to the bikes and to the tyres. In the last two decades alone MotoGP’s rulebook has grown from 99 pages (in 1999) to 365 pages now.

The main reason to specifically limit tyre performance is to prevent corner speeds increasing because nowadays there is such a thing as too fast.

If MotoGP bikes keep going faster and faster around corners it won’t be long before the championship’s greatest tracks – Brno, Mugello, Phillip Island – will disappear, because they are already at the limit of run-off.

Such are the efforts to limit performance that today’s MotoGP riders go racing with narrower rear wheel rims than Wayne Rainey used to win the 1990 500 world championship. Back then Rainey mostly used a 6.25in or 6.5in rim on his Yamaha YZR500, which made around 160 horsepower.

Today’s MotoGP bikes – which are knocking on 300 horsepower – are limited to rear rims of no more than 6.25in at the rear and 4in at the front.

Each manufacturer is also limited to just two sizes of rim at each end – usually 6in and 6.25in rears and 3.5 and 4in fronts. A wider rim spreads the tyre which changes the profile, usually putting more rubber on the road but at the expense of slower handling. Most MotoGP riders currently use 6.25in rears.

This restriction to two sizes of rim is another result of things getting out of hand, as they do when some teams have lots of money to spend. Back in the final days of the 500s and the early days of MotoGP the richer teams had four or five different rim sizes for both front and rear wheels, which they could use as another tool for adjusting steering, handling and grip. And teams needed perhaps half a dozen rims in each size, which was good business for the wheel manufacturers but a disaster for the poorer teams.

Due to these restrictions and also the natural limits of a motorcycle – you probably don’t need me to tell you that an 8in or 9in rear rim wouldn’t be a good idea if you’re riding around a racetrack – the contact patch available to riders has hardly changed since Rainey ruled the world, despite horsepower nearly doubling.

Everything has got much better – engines, frames, suspension, brakes, and electronics – but the tyres are still just two hoops of rubber that must do their work by bonding with a few square inches of asphalt.

Teams can play around with tyre pressures – reducing pressure flattens the tyre and therefore expands the footprint – but even tyre pressures are now limited. This prevents teams from going too low in search of faster lap times and risking tyre failures.

Michelin’s current minimum limits are 1.9 bar (27.55psi) for front slicks and 1.7 bar (24.65psi) for rear slicks. Any rider found going lower – all tyres are monitored by mandatory pressure sensors that send info to Michelin – are supposed to get sanctioned.

In spec-tyre racing the aim of every team is the same: to generate the forces in the available tyres to get them to work, via engineers adjusting the motorcycle and via riders adapting their riding technique.

This year’s big challenge in MotoGP is the 2020 rear slick, which is causing issues for some bikes and riders but not for others. That’s always the way – every tyre will always suit some better than others. Whoever best solves the riddle of the 2020 rear will most likely win the 2020 world championship.