For some time Jerez has signified the beginning of the European leg of the MotoGP World Championship, but for 2005 it is the first leg of the 17 round season.

It's fitting then that Jerez is the circuit which traditionally pulls in the largest crowd, well over 200,000 last year during the three day event. It's due to the Spanish passion for motorcycle racing, but also the circuit's reputation for providing hard and close racing.

The closeness of the racing can be attributed to the undulating 4423m layout, numerous hard braking areas and countless camber changes; making a predictable chassis balance the primary concern - especially during heavy braking. For this reason it's necessary to maintain stability over the countless bumps that infest the entry into almost every turn, while also providing front-end feel which will inspire confidence.

The front forks will need to deal with the high braking loads yet they must also offer enough movement while almost fully compressed to ensure that it is the suspension absorbs these bumps rather than the front tyre.

Increasing the spring rate will prevent the front of the motorcycle from diving too quickly under heavy deceleration - a result of the weight transferring forward - while the fork compression damping will be set to allow enough high-speed movement to deal with the repetitive bumps.

Fork rebound on the other hand is dialed in to slow the return of the forks to their full length. This will prevent under-steer as the rider makes the transition from brakes to throttle and the weight transfers to the rear of the motorcycle. These steps, along with reducing the rear ride-height, will ensure the back wheel stays planted on the tarmac, in turn improving braking stability.

The virtually all-new 2005 YZR-M1 has experienced a few teething problems throughout the winter test schedule, but nothing that Yamaha feels will seriously hinder its chances at fighting for a victory at the first race of the year. The most visually obvious of these is with the main chassis - the upper engine mounts have been revised, as have the twin main spars.

These changes have been made in an effort to retain the same vertical and twist rigidity as in 2004 while reducing the lateral rigidity - effectively increasing front-end feel at high lean angles, when the effects of suspension travel is reduced. A crucial benefit on the bumpy high-speed turns featured at Jerez.

The overall dimensions of the YZR-M1 have also seen it stand slightly taller to help get the weight over the front of the bike during heavy braking. This effectively pushes the weight of the bike directly down the fork legs, pressing the front tyre harder into the track and increasing traction as a result. Again this is a significant advantage at such a hard braking circuit like Jerez.

The rear spring rate will be set slightly firmer to prevent the bike squatting under power through the long, sweeping, high-speed corners and the resulting cornering forces, while overall feel will be ensured with less compression damping - aimed at helping riders gain the best drive off the positive cambered turns. The M1's 2005 in-line four-cylinder engine will also help this cause thanks to the further evolution of its 2004 revised firing order design.

The revised firing interval of 2004 ensured the M1 retained the advantages of its compact in-line four-cylinder design with the added bonus of a power delivery resembling that of a V engine layout.

You only needed to hear the M1 to know there was something very different about the 2004 machine. So much so that many media nicknamed this latest incarnation as the 'Big-Bang' M1.

For 2005 Yamaha's engineers have delved further into identifying the ideal firing cycle in an effort to increase the peak power without sacrificing the 'sweetness' of the delivery.



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