Yamaha YZR-M1 MORELONGITUDINALSTIFFNESS

º Engine: 989cc inline-four four-stroke º Power: 225bhp (2004) º Weight: 148kg º Number of wins: 46 Note long and super-slim engine hanger – Yamaha were also seeking more longitudinal stiffness and less torsional stiffness.

When Rossi joined Yamaha the factory’s race department was in crisis. The M1 hadn’t scored a single victory during 2003, while the RC211V took 15 wins and 39 podiums. This was the scale of the challenge facing Rossi, crew chief Jeremy Burgess and Yamaha’s racing chief Masao Furusawa.

In fact they fixed most of the bike’s problems during Rossi’s first test in January 2004. The M1’s biggest problem had been locking the front tyre into corners. No one had been able to solve this problem, but Rossi beat it on day one! His feedback, crosschecked with data, revealed that the engine-braking software was all wrong – it was accelerating the bike into corners!

The 2004 M1 wasn’t as good as the RC211V but the 2005 M1 was. A more compact engine helped Yamaha concentrate mass, which made the bike the most agile on the grid, with superb corner-entry performance. The 2005 M1 also made more peak power, thanks to an extra 1500rpm. ‘But we still need to improve engine character in acceleration because the Honda is more elastic, more sweet,’ said Rossi. The big regulations change for 2005 was a reduction in fuel capacity, from 24 litres to 22. Every drop of fuel wasted became wasted horsepower, so electronics engineers had to minimise wheelspin, because spinning the tyre wastes fuel.

The all-new 2006 chassis gave good results at the factory but chattered like crazy with Michelin’s grippier 2006 rear slick. Rossi’s crew tried many cures but the best fix was reverting to the 2005 chassis. An improved version of the 2005 unit arrived mid-season, plus a stiffercarcass rear slick for more stability.

Yamaha’s last 990cc engine had a shorter stroke, for an extra 800rpm and five more horsepower – around 250 in total. Fuel consumption was improved via better combustion. Yamaha were still learning – in hot weather the fuel cavitated in the fuel pump, so for 2007 the pump was put inside the fuel tank.

Rossi lost the 2006 title largely down to bad luck, but in the first year of the 800s he was out-gunned by Ducati. The 190cc reduction in engine capacity and a further one-litre reduction in fuel capacity, to 21, caused Yamaha’s engine designers big problems. Yamaha struggled to create enough power with less fuel and when they did find more power they had overheating problems. Then they introduced a pneumaticvalve engine (which increased revs from 17,500rpm to 19,000) and they had even bigger reliability problems. On the plus side the bike was still user-friendly and strong in the corners.

In 2008 Valentino went so far as to threaten walking away from Yamaha if they didn’t manage to turn things around after the defeats

of 2006 and 2007. The threat worked because the 2008 M1 was the best bike on the grid, a superbly rider-friendly package that defeated the fast but fiery Ducati.

Yamaha increased power by 12 percent. The giant leap was the electronics, with cutting-edge vehicle dynamics software that calculated lean angle, tyre contact patch, centrifugal force and delivered exactly the right amount of torque at any lean angle, regardless of how much throttle the rider used. The system was also predictive, like Ducati’s, so it was always one step ahead of the rider, making tiny adjustments as and when necessary.

2009’s move to stiff-carcass Bridgestone spec tyres required a rethink on chassis specification. The 2008 M1 had a shorter wheelbase to get more load into the tyres to generate more heat and grip. In conjunction the M1’s anti-wheelie software was developed to improve acceleration from slower corners, always a Yamaha weak point. The old system gauged wheelies via front-wheel speed and fork-extension sensors. The 2009 system measured machine pitch rate to predict wheelie level, a more accurate method.

The following year Yamaha remained the best bike in Motogp for the third season in a row and for the first time someone else rode it faster than Rossi. Jorge Lorenzo’s glass-smooth riding style suited the M1 perfectly and allowed him to run settings that were more friendly to the tyres. Also the Spaniard didn’t move around on the bike so much, which allowed him to use huge corner speed, so he didn’t have to use so much throttle to get out of corners. Meanwhile Rossi over stressed the rear tyre.

In Motogp’s new specification tyre era chassis set-up became trickier. ‘You need to get your wheelbase, centre of mass and rotation [of load] correct, so you are putting weight on the front during deceleration and onto the rear when you are accelerating,’ explained Burgess. ‘If you don’t have enough weight on the rear, you will lose grip on the exits and you’ll also lose the assistance from the rear of the bike when you are braking. But if you put too much weight on the rear, the bike won’t turn or brake well.’

‘The M1’s big problem had been locking the front tyre. Rossi beat it on day one’