MotoGP Chassis Wars

Yamaha's YZF-M1 MotoGP bike, on which Jorge Lorenzo gets such fabulous starts and is now leading the Championship, has come far from the original design of 2001.

Yamaha engineers began the new four-stroke MotoGP era by adapting the chassis of its 500cc two-stroke YZR500. It was a loveless marriage. At Motegi in 2003 the engineers were puzzled. An M1 would lap consistently for a time, but then the rider might lose the front end and crash. Sound familiar? Casey Stoner, riding the super-rigid carbon-chassis Ducati had the same experience in 2009–'10: loss of front grip without warning. "Feel" is the warning signals a bike gives you as you near the limit. Ducati had it with the steel-trellis used by Stoner in 2007, and it appears they didn't know what they were giving up with the frame-design switch in '09.

I met a Yamaha chassis engineer at the Yamaha "Media Center" (museum) in Hamamatsu just before Motegi. He pointed to the two long front engine hangers on Honda's dominant RC211V V5 bike. They could, he said almost wistfully, allow the whole steering head to flex slightly from side to side, acting as a "suspension" at high angles of lean, to keep the front tire gripping on unsmooth pavement.

At the track, I encountered Honda’s RC211V project leader, Shogo Kanaumi. He said his company had made many tests to determine how much stiffness is necessary in various directions. He noted that great torsional stiffness is necessary for good handling, but laterally there is benefit in increased flexibility.

Honda had used this in a 2002 crash program to make Colin Edward's RC-51 Superbike match the corner grip of Troy Bayliss' wallowing trellis-framed Ducati. Edwards had said of the very flexible, visibly weaving Ducatis, "Yeah, they wallow. But they dig in and go around the corner."

This program, applied in steps, eventually gave Edwards the corner grip he needed to win the 2002 title after an epic finale at Imola, Italy.

In May of 2003, Yamaha’s engineering “fixer,” Masao Furusawa, was put in charge of the M1 program. The prototype he gave Carlos Checa for the post-Valencia test at season’s end had the new, long front engine hangers—and he immediately went faster on it. Of this prototype (the first of four initial test chassis), Furusawa said, “We decreased the lateral stiffness quite considerably while increasing torsional and vertical stiffness just a little. This concept turned out to be a big improvement.”

Motorcycles have very limited tire footprint, so their turning ability is limited. There are two basic approaches to how best to use this ability. One is to minimize what the motorcycle does poorly—turning—and maximize what it does well—accelerate. This is the kernel of what Kenny Roberts took to Europe in 1978, to brake late and hard, get the motorcycle turned early and quickly, and then use the remaining part of the corner as a dragstrip on which to achieve a high exit speed. Roberts’ rivals were faster at the apex, but he was faster where it counted—on corner exit. He was 500cc GP champion 1978–’80.

Today’s version of Roberts’ dirt-track-derived style looks a lot like corner speed, but Ducati’s MotoGP engineer Filippo Preziosi in 2008 cautioned that, “something else is going on.” That something was Casey Stoner’s style of tightening the turning process by dropping down on the tire edges for a limited time to steer with throttle, defining the “point” of what Cal Crutchlow later called “Honda’s V-shaped line.” Honda’s Marc Marquez rides in similar style.

Yamaha, in its M1, instead chose to maximize tire grip to enable riders to carry maximum speed through corners. With speed higher in-corner, less braking and acceleration were necessary. To maximize grip, suspension spring and damping rates had to be softer to enable tires to track over roughness.

Chassis length was extended to increase stability.

Transitions from braking to turning and from turning to acceleration had to be made with great smoothness—no sudden moves or “yankin’ ’er around.”

When Crutchlow rode the Yamaha in 2011 he tried to ride it in Superbike brake/get turned/go style but he said, “It wouldn’t do it. I had to learn to ride it as it was.” Hard braking on the soft-sprung Yamaha could bottom the fork, and trying to get it turned quickly was delayed by its longer wheelbase and softer suspension.

MotoGP has become a straight contest between these two contrasting styles. As you’d expect, the “Honda way” works best on stop-and-go tracks, and “Yamaha’s way” can excel on flowing tracks and longer corners.

As tires evolve, chassis must evolve. When Michelin brought a big new rear tire in 2006, it set every chassis to chattering. The usual emergency fixes (like lead-filled axles to tune out certain flex frequencies) worked for Honda but not for Yamaha. Valentino Rossi was stopped by chatter for four races, and only reverting to the 2005 chassis enabled recovery. Chatter, stability, chassis flex, and engine characteristics are mysteriously entangled. There is no textbook. The ’06 championship was lost.

In 2007, the problem was Casey Stoner on the 800cc Ducati with revolutionary Bridgestone tires. When Rossi switched to Bridgestones, weight had to be shifted rearward on the Yamaha and its center of mass raised to transfer weight forward quickly on braking. Yamaha’s 2008 chassis’ lateral stiffness cut another 10 percent (making it now just two-thirds as stiff as the 2004 baseline), and with refined electronics and Bridgestone tires Yamaha riders dominated 2008–2010.

In 2012, engine size jumped from 800cc to 1,000cc. M1s were now run with their rear axles at their long limit to minimize wheelies and exploit the bigger engine’s greater torque. A longer swingarm arrived. Chassis beams were reduced in cross-section, especially just above the swingarm pivot.

Photos of the most recent M1 chassis show that the former “Deltabox” structure of separate side beams, engine hangers, and hanger struts has blended into a triangular “big web” on each side, billowing out like Batman’s cape to clear the engine’s cylinder head, with an apex attaching low on the front of the engine as before. Some have speculated that the “Batman cape” is machined from solid to precisely control its dimensions. This chassis seeks to better combine the necessary lateral flexibility with the bending and torsional stiffness required to resist braking force without upsetting steer effects.

In 2013 began the reign of Marc Marquez on Honda, the duration of which is unknown to us. Riders asked for increased braking stability (a particular Honda strength) and more in-corner grip.

Tires changed again. Yamaha lost ground when Bridgestone in 2014 brought faster-warming tires that also had slightly reduced edge grip. Edge grip is basic to the modified corner-speed riding styles being evolved by both Lorenzo and Rossi and built into the long-and-low Yamahas. But both riders are having to reduce their time on the tire edges because the Honda, plus Marquez’s mastery of tire management, often add up to Marquez having more tire left at the end—as he clearly did at Indianapolis. Lorenzo has a substantial championship lead as the second half of the season moves to tracks that notionally favor the Yamahas.

No chassis can be perfect—just better or worse. Motorcycle roadracing might have once been a noble contest of engine power and durability, but with engine development now frozen in-season it has become a struggle to produce chassis properties that riders can use to race hard all the way to the last lap. Chassis and suspension function as a filter system, softening or stopping inputs that fatigue the tires, letting through inputs that riders need to know where the edge is. Understanding is taking time but will one day benefit all motorcycles.