Formula 1 2026, Sepang: Why You Should Have Been Watching Super GT

A softer tyre degrading less than a harder one on Sepang’s ageing asphalt. Surprised? You probably shouldn’t be. 

After Friday practice, Pirelli engineer Simone Berra revealed that in some direct comparisons the soft compound degraded at roughly the same rate as the medium - and sometimes even less. The reason is simple enough: the harder tyre is struggling for grip, sliding more, overheating the tread surface and destroying the very advantage its more durable compound is supposed to provide. 

Friday degradation ran at around 0.2–0.3 seconds per lap. Two stops are considered the baseline, three are possible, yet nobody used the hard tyre at all on Friday. Every team saved two fresh sets for Sunday. 

There is now a very real possibility that the tyres everybody so carefully saved will turn out to be the wrong ones. 

Unless it rains, naturally. 

For us, however, the more interesting question is why this “anomaly” exists at all. 

Sepang’s asphalt is breaking up. Cars are pulling loose particles onto the racing line, and the FIA has arranged for the circuit to be swept after every session. Pirelli says real lap times are around 4.5 seconds slower than simulation predicted, largely because of the surface condition. 

The Formula 1 teams that clearly have not been paying much attention to Super GT spent all of Friday protecting their toughest tyres for the race. 

The logic looked impeccable. High degradation? Save the hard tyre. Unfortunately, the tyre has its own ideas. 

After FP2, Berra described a rather revealing result from both modelling and direct comparison. In some cases the soft did not degrade more than the medium. Sometimes it degraded less! 

For Formula 1 fans who watch nothing except Formula 1, this may look peculiar. 

For the rest of us, not so much. 

Super GT has been teaching the same lesson for years: calling a tyre “soft”, “medium” or “hard” tells you far less than people imagine. Three nominal tyre types may hide numerous combinations of tread, belt and carcass stiffness. 

And the first thing to remember is this: A harder compound is not necessarily a colder tyre. 

A hard compound may resist certain forms of thermal degradation and wear better. But first you have to make it work.If the tyre does not generate enough grip, it slides more against the asphalt. 

Yes, some slip is essential to generate lateral force. That is how tyres work, sorry. But once you pass the useful slip range, additional sliding no longer creates more cornering force. 

It destroys it. 

And sliding means heat. Worse still, that heat appears exactly where you do not want it: close to the tread surface. The deeper layers may still be relatively cool because the structure is stiffer and takes longer to warm. 

Now you have a hot surface over a cooler internal structure. And that is one route towards tearing, separation and those familiar rubber “worms” we call graining. 

The softer compound can do the opposite. It conforms to the asphalt more effectively. It generates more grip. The car slides less. The driver makes fewer corrections, the rear tyres spin less on corner exit, and the front tyres scrub less when the car pushes into understeer. 

So although the rubber itself is less durable, less energy is being wasted through parasitic sliding. 

And because “soft” only describes part of the tyre - especially if you remember the Japanese approach, where tread, belt and carcass stiffness may be combined in very different ways - a soft tread does not automatically mean a thermally soft internal structure. 

Under the right conditions, the two effects cross over. 

And then tyre heresy occurs: the softer tyre lasts longer than the harder one. That appears to be exactly where Sepang has ended up. 

But so far we have only heard the tyre’s side of the story. 

The asphalt has a statement to make too. 

Why it pays to watch more than Formula 1 

If Sepang’s behaviour has surprised you, you probably have not been following the rest of motorsport very closely. The circuit did not suddenly collapse because Formula 1 arrived. Its deterioration was already visible at least as far back as the 2025 Super GT season. 

At the January winter test everything still looked normal. Team Kunimitsu Honda ran a 1:48.996. When Super GT returned in June, the same car was already more than two seconds slower in first practice. 

The Japanese drivers said openly that the surface felt completely different and grip was much lower. Tadasuke Makino estimated the loss against the winter test at roughly three seconds. TOM’S Toyota made the same observation: the circuit had deteriorated noticeably since January. 

So what changed? 

Most of Sepang’s asphalt is old. The circuit was last fully resurfaced in 2016. Parts of the lap were renewed in 2023, including roughly the T6–T12 area and the region around T9, but a large proportion of the circuit still uses the older surface. 

Before the Grand Prix, Pirelli measured very high roughness - comparable with Bahrain. But asphalt does not age like a concrete slab that simply gets smoother. 

Very crudely, it is a structure made from: aggregate + mineral filler + bituminous binder. 

The aggregate gives you the texture. The bitumen holds the stone skeleton together. 

And ten years in Malaysia is not a pleasant life for bitumen: heat, high ultraviolet radiation, rains, repeated extreme heating and cooling. Oxidation gradually removes lighter components and makes the binder harder and less ductile. 

The result can sound contradictory: a surface that is extremely rough for the tyre - and at the same time - too weak to hold its own aggregate together. 

The tyre can grip the exposed stone perfectly well. The problem is that the stone itself is no longer held as securely inside the asphalt matrix. Super GT had already started noticing the effect. GT500 cars are heavier than Formula 1 cars but generate less downforce, so the total cornering loads are still lower. 

Then Formula 1 arrives. And Sepang begins to eat itself. 

Not simply because “F1 has more downforce”. What matters is the combination of large normal loads and enormous tangential forces in the contact patch. 

Imagine one piece of aggregate protruding from the surface. The tyre pushes down on it vertically while simultaneously trying to move it sideways or longitudinally. Under braking, the contact tries to drag it one way. Under traction, the other. In a corner, lateral force tries to pull it sideways. 

If the bituminous binder is still sufficiently tough and viscoelastic, the stone stays where it belongs. If the binder has aged and weakened, ravelling begins. The aggregate is pulled out of the surface. 

That is very close to what Pirelli is now describing. Berra says the asphalt is physically breaking up during the sessions and loose stones are appearing on the track. 

Between sessions, the FIA can send out sweepers. 

During the race, with twenty cars, high temperatures and repeated loading, things become more difficult. Again: unless the rain decides to solve the problem in its own way. 

Between tyre and road 

Sepang is currently sitting in a particularly nasty middle ground. There is an abrasive asphalt, where the road wears the tyre. And there is a disintegrating asphalt, where the tyre starts wearing the road in return. 

Temperature probably explains a good part of the difference between the trouble-free winter Super GT test and what Formula 1 is seeing now. 

During Friday running, the track surface stayed above 50°C. When Super GT raced here in June 2025, the asphalt was generally around 36–46°C. It was about 42°C at the start and fell towards 35°C during the race. The January test was probably kinder still. 

For bitumen, another 10–15°C matters enormously. Its mechanical properties are highly temperature-dependent. Heat softens the binder. Its modulus falls. And its ability to hold aggregate under repeated tangential loading becomes worse. 

Once stones and rubber debris appear on the racing line, the effective friction coefficient falls. The tyres slide more. That creates more heat and more tangential work. Which creates more damage. A wonderfully self-sustaining mess. 

Pirelli apparently does not watch Super GT either. A few weeks before the Grand Prix, the Italians did not expect anything this dramatic. Their measurements suggested that the broad characteristics of the surface remained reasonably similar to 2017. 

And that tells us something useful. 

Static roughness measurements did not reveal the parameter that really mattered: the strength of the aggregate-binder bond under dynamic loading. They measured roughness. They measured the friction-related characteristics. 

But apparently not the surface’s willingness to fall apart when a modern Formula 1 tyre starts pulling at it. 

The soft tyre takes revenge 

Now back to the tyres. Softer rubber has a lower dynamic modulus, so under the same load it conforms more closely to the road microtexture. 

This is entirely consistent with Persson-type contact theory: road asperities repeatedly deform viscoelastic rubber, and the easier the rubber deforms at the relevant excitation frequency, the greater the real contact area becomes. 

Experiments show the same basic trend. Increase elastomer stiffness and the real contact area falls. In deliberately crude terms: the soft rubber wraps around the peaks. 

The hard rubber rests on fewer of the highest ones. 

And that gives us another interesting possibility. 

If the same normal load is carried by a smaller real contact area, the local pressure on individual asperities rises. Experimental work on elastomers has shown exactly this: harder materials can create higher local contact pressures and increase the abrasive action of hard particles against the opposing surface. 

So, crudely again, the hard tyre does not deform around the microtexture. It simply hammers harder on the highest points. And that may make them easier to fracture. 

Problem solved? 

Not quite. 

Because the soft tyre has another weapon. If it wraps further around a protruding stone, it does not merely press down on it. 

It can grip it. 

And that allows the tyre to transmit a larger tangential force into the aggregate. Recent experimental work has shown that softer elastomers can entrain particles more strongly in the contact, increase friction and, in some regimes, produce more wear of the opposing surface, not less. More grip produced more grooves and more damage. 

So an old asphalt surface may face two different failure modes. 

The first is the hammer: a hard tyre concentrates load onto fewer asperities and fractures the surface through high local pressure. 

The second is the pliers: a soft tyre wraps around the aggregate, develops a large tangential force and pulls the stone sideways until the weakened bituminous binder lets go. 

Why can the soft last longer? 

The soft tyre conforms to the microtexture better. It generates more grip - the car slides less. 

If the medium compound is too stiff for the current surface, it may spend every lap undergoing small amounts of unnecessary slip. And over an entire lap, it can therefore dissipate more frictional work despite being made from harder rubber. 

That energy has to go somewhere. Into tyre temperature. Into tyre wear. And potentially into further destruction of the already weakened road surface. 

Real tyre-road contact research shows just how sensitive this can be: local roughness can alter friction by more than 50%, while the so-called flash temperature generated inside microscopic contacts has a strong influence on the friction coefficient. 

As for the road itself, there is even modelling work showing that local stress concentrations in tyre-road contact contribute to wear both of the tyre tread and of road asperities. 

So asking “Which tyre destroys the road microtexture more?” is not some pub argument. 

It is a perfectly legitimate tribology question. 

And suddenly school physics is no longer enough. 

The softer rubber creates more real contact area and may transmit a greater tangential force. The harder rubber has less real contact area and therefore higher local pressures. 

So there is no universal answer of “soft” or “hard”. 

You need one more piece of information: How is the surface failing? 

If failure is controlled mainly by local compression or fracture of aggregate, the harder tyre is the more likely aggressor. 

If failure is controlled by aggregate being pulled out of weakened bitumen by tangential loading, the softer tyre may - surprisingly - be the more destructive one. 

So no, for those of us who watch Super GT, Sepang’s tyre behaviour is not particularly shocking. 

For everyone else? 

Well. 

Maybe it is time to broaden the viewing schedule.

• Вперёд >