Assen is unique in a number of ways; the Dutch TT originally began life as 28km street circuit before being shortened - once in 1955 and again in 1984 - to comply with the ever-changing demands of modern motorcycle racing.

The most recent of these took place this year with the modification to the snaking back straight leading up to the Stekkenwal right hander. With speeds increasing safety became an issue with the current layout and as a result the former back straight has now been fitted with a second gear right hander at the midpoint followed by a sweeping left into Stekkenwal.

In addition the De Bult turn has been become more of a 90-degree turn and has lost its positive camber. Despite these changes the Assen layout is still the longest on the MotoGP calendar, now measuring just less than six kilometers in length, and continues to maintain its street pedigree - although this is changing with every modification. The length has been shortened by a total of 30m - from 6027 to 5997 - and is due for an additional modification in 2006.

With barely a straight piece of tarmac in sight there is no rest for the MotoGP field, making Assen more of a rider's circuit than any other ever visited this season. Handling will therefore be a major focal point, due to high-speed chicanes and dramatic camber changes - the latter, in some places, resembling the profile of a public road more than that of a motorcycle racetrack.

This single feature in itself makes Assen a challenging circuit to master. Hold the inside line and the rider will benefit from the extra drive available off the steeper section of the camber, but the suspension will need to compensate for these much higher G-force loads that will be experienced.

A good result at Assen relies heavily on a chassis that offers both agility and stability. It is quite a difficult balance to find at the best of times, but with the white line to white line racing line it is a must find. This is why Yamaha will continue with the base geometry it has used over the past few rounds, relying on the finer adjustments of the suspension package and the correct tyre profiles to get the best out of the Deltabox chassis.

The combination of such fast cornering, good grip levels and extreme camber angles produce the high cornering G-forces, a load which the suspension package will need to deal with. For this reason a heavier rear spring rate will be chosen, in comparison to the front set-up, to prevent the back of the bike squatting under power, yet it will still need to offer a compliant ride to ensure feel isn't compromised.

This won't be an issue if the compression damping character is dialled in to compensate. Therefore it will be wound back, from what was used in Barcelona two-weeks earlier, increasing the predictability of a slide as well as tyre life.

Although the rear spring rate is firmer than what Yamaha used at a circuit like Mugello, the front will be somewhat softer in feel. The latter is possible because of the lack of seriously hard braking that will be done on the flowing layout. Tailing the brakes into the turn is more common at this circuit.

With an outright top speed of around 310kmh Assen isn't the fastest circuit, especially when you compare it to the 340kmh plus of Mugello, but that doesn't matter as the Dutch TT isn't about outright top speeds - it's the top speed average that counts.

In this regard Assen is one of the fastest tracks of the year. Because of this it's an extreme and hard working circuit, not only for the riders and the chassis, but the tyres too. Fortunately grip levels are high yet the track surface isn't too abrasive, even though almost all the driving will be done off the side of the tyres.



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