Why has Yamaha moved the M1 fuel tank?

Aside from MotoGP's switch to Michelin tyres, the biggest visual change on the 2016 Yamaha is a new fuel tank accessed from the rear of the bike.

So instead of having the fuel filler system located in front of the rider, it is now behind the seat.

We don't know the exact shape of the new Yamaha tank, but the majority of fuel is usually stored directly under the seat (see examples below). All other manufacturers still have the filler in front of the rider.

Katsuyuki Nakasuga gave the revised Yamaha tank its public debut as a wild-card in October's Japanese round (pictured), qualifying 15th and finishing the wet race in eighth place.

However eventual champion Jorge Lorenzo and Movistar Yamaha team-mate Valentino Rossi had already tested the bike in private at Aragon in September, then again at Valencia last month.

"The 2016 machine we tried in Aragon is the bike that's adapted to the Michelin tyres to get the best performance. The fuel tank is on the back, behind the seat, before it was in front of the rider," Lorenzo confirmed at Valencia.

While Bridgestone was renowned for the grip generated by its front tyre, it is the Michelin rear that dominates. Most believe weight distribution will be moved forward to compensate, so is that the reason for the new tank design?

"It is a different grip balance [with the Michelins], but we also have two litres more fuel for next year so we need to create volume. Find more room," Lorenzo's team manager Wilco Zeelenberg told Crash.net.

While the Yamaha and Honda factory entries have been restricted to 20 litres in recent seasons, this is increasing to 22 litres - for all competitors - due to the thirstier single ECU system.

"It's not completely [decided] if we will use this tank set-up yet. We know we have two litres more fuel to put somewhere so this idea was created and we are trying it," Zeelenberg continued.

"Basically we can go everywhere [with the two litres of extra fuel] but you cannot go a lot more forward because you have the airbox. And if you make the airbox smaller, that would be a problem!"

The Dutchman confirmed that the tank also allows the factory to try some new set-up options, as Yamaha seeks to perfect weight and geometry for the 2016 tyres.