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The Assen TT circuit from a tyre point of view

The FIM Motul Superbike championship heads to a true temple of bike racing for the fourth round of the season 

The Assen TT circuit from a tyre point of view

Precision, technology and speed: three words that can accurately describe the Assen TT circuit; a Dutch track that ranks among the most famous in the world, where the fourth round of this year’s Superbike season will take place

Assen has hosted the world’s premier production-derived bike racing championship since 1992, on a circuit that was designed specifically for two wheels. It is recognised the world over as one of the most challenging circuits out there because of its high average speeds and rapid direction changes, which require massive concentration and precision.

The TT circuit at Assen also has a fascinating history. The whole story began on 11 January 1925 with the very first race that was held there, on a road circuit – unpaved in some places – between the villages of Rolde, Berger and Schoonloo. 

The first winner was Piet van Wijngaarden aboard a 500cc Norton CS1, ahead of the only three other drivers to have arrived heroically at the finish. Cheering them on were around 10,000 spectators by the side of the impromptu track.  That was around 28 kilometres long and featured some fast corners as well as flat-out straights. From start to finish, there was no shortage of hazards to catch unsuspecting riders out.

The heyday of Assen continued throughout the 1930s, when the track joined the international calendar and was called the Dutch TT in honour of the original Tourist Trophy. Even today it’s the only race on the calendar still to be called the TT, commemorating its roots as a road race.

In 1955 the current circuit was built in record time. Or at least part of the current circuit as we know it: the start-finish straight was also a public road open to everyday road traffic. Added to that was a closed loop infield, which made up the full circuit.

The first proper circuit race at Assen was held that very same year. And it led to a famous incident that is still called the ‘Assen miracle’ today. The riders, having seen the incredible number of spectators by the side of the circuit, started to demand a higher wage than had been originally agreed with the race organisers. After completing a very slow parade lap, they refused to take the start. Only a last-minute intervention from the organisers, who managed to finally hammer out a deal with the riders, avoided a complete fiasco.

In 1992, the local government decided to definitively close the start-finish straight to normal road traffic, and instead included it into the permanent circuit. This was mainly down to a number of serious accidents that took place during illegal street races held on the straight. 

Some extensive modernisation to the circuit and infrastructure took place between 2005 and 2006, when sweeping changes were implemented in the north part of the track. A new entertainment area was built and some sizeable grandstands were constructed on the section of track between Haarbocht and Veenslang. The capacity now is for 64,000 spectators. The current configuration, which includes the final modifications made at Ruskenhoek, reduced the overall length of the circuit by around 1500 m, to the current 4542 m.

Today the Assen TT circuit contains 17 corners: six left-handers and 11 right-handers. The tyres are not particularly stressed from a thermal degradation point of view: instead the key point is precision and strong directional stability in order to give the riders confidence throughout the many fast corners.

One of the decisive elements throughout the race weekend is the weather. The weather conditions in April can be variable and absolutely unpredictable, with highs and lows that have a big influence on tyre behaviour.  

The Dutch circuit’s asphalt has a high bitumen content, which means that the external temperature has a very big influence on track conditions: especially when using soft compounds on a ‘green’ track with little rubber laid on it. In particular, this phenomenon is mostly seen on Friday during the free practice sessions – at an early point during the race weekend.

During first part of the Assen TT Circuit, it’s important to find a good balance between the front and rear tyres, allowing riders to maintain the correct racing line even at very high average speeds of over 100kph.

The sudden variation between different types of corner is a particularly demanding characteristic of the track. So it’s very important to guarantee a high level of stability from the tyres: both front and rear, during the continual direction changes and acceleration. As a result, the teams tend to avoid the softest compounds and instead opt for harder compounds such as the SC1 or SC2. The specific characteristics of Assen can sometimes produce a phenomenon known as cold tearing, which leads to the tyres losing grip and not working correctly. 

Last year’s Assen TT round was once more heavily influenced by the weather, particular during race one, which was won by Jonathan Rea (Kawasaki Racing Team) by more than a second from Chaz Davies (Aruba.it Racing-Ducati SBK Team) and four seconds from local hero Michael Van Der Mark, riding a PATA Honda World Superbike Team CBR1000RR SP. For Rea it was a particularly good weekend as he also won race two, with the podium being a carbon copy of race one.

The Supersport race was won by Turkish rider Kenan Sofuoglu (Kawasaki Puccetti Racing), who would go on to be champion at the end of the season, followed by Jules Cluzel (MV Agusta Reparto Corse) and Britain’s Kyle Smith (PATA Honda World Supersport Team). 

In Superstock 1000, Lorenzo Savadori triumphed, riding a Nuova M2 Racing Aprilia RSV4 RF.

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