At the final Grand Prix event of the year, Yamaha traditionally holds a press briefing and discloses some information about that year’s YZR-M1 machine and its development. This year was no different, and at the recent Valencia round Kouichi Tsuji, MotoGP Group Leader and YZR-M1 Project Leader, gave this year’s presentation.
In every year’s briefing, it seems the development goals for the M1 are the same as years previously: The focus for the engine in 2012 was “balanced power and fuel;” for the chassis, “maximize corner speed and agility;” and for the EMS (Engine Management System), “direct and natural feeling.”
But this year marked a new era for MotoGP – or, perhaps, a return to a previous era – as capacity was increased to 1000cc. Maximum bore size is now limited to 81mm, and minimum weight was slightly increased. Additionally, Bridgestone made changes to the spec tires to cope with the increased power. According to Yamaha, the M1’s power increased from “over 200” to “over 240” horsepower, or an increase of approximately 20 percent, and the maximum speed reached at each track increased by an average of 11 km/h.
The presentation notes that faster lap times this year are largely due to the higher speeds, but the improvement in lap time was not as much as expected due to time lost from correspondingly more braking. In an example using data from 2011 and 2012 at the same track, a gain of .3 seconds was seen on one straight from the increased power, but at the end of another straight .2 seconds was lost under braking. In another example, the braking point at the end of the straight moved 17m earlier, a significant change.
To cope with the increased power and changed tire characteristics, the wheelbase was lengthened and the weight bias moved slightly forward. Increasing wheelbase reduces the tendency to wheelie both under acceleration and braking, while moving weight forward reduces wheelies under power but with an increased chance of the rear wheel coming off the ground under braking.
Designers in MotoGP have constantly been moving the centre of gravity around to take advantage of certain characteristics (or minimize difficulties associated with others), and the general trend since MotoGP’s inception has been longer, lower motorcycles. This layout helps keep both wheels on the ground under braking and acceleration, an increasing problem as power improves, brakes get stronger, and tires have more grip. The tradeoff with a longer, lower chassis is in cornering performance; the bike is more difficult to turn from side to side, and more lean angle must be used for a given corner radius and speed.
It’s interesting to note that rider input – how much of a sacrifice in one area is worth an advantage in another – has directed this trend to a certain extent. Small changes in weight distribution and centre of gravity height can be made with minor adjustments, such as moving the rider around, changing the position of the rear wheel in the swingarm, and so on. But at some point, large objects – such as the engine – must move and new parts must be made. Yamaha arguably made the best transition to 1000cc in 2012, with Jorge Lorenzo winning the championship, both Tech 3 satellite riders reaching the podium during the season and Andrea Dovizioso finishing fourth in the championship.