Recent Chassis Developments In Moto2

Kalex rises to the top.

Chassis development moves forward in Moto2 and Kalex is proving to be most used on the grid.MotoGP.com

The 60-year history of the FIM’s 250 roadracing class was in 2010 replaced by both a new class and a new concept. The FIM’s previous classes, 125, 250, 350, and 500, had existed to present the range of motorcycles then being produced. In that era there were riders such as Ángel Nieto or Giacomo Agostini who spent their careers in one or two classes—the former in 125, the latter in 350 and 500. Each manufacturer in each class had developed its own racebikes, including their specialized engines.

For 2010, all this changed. Henceforth the racing classes would be rungs in a ladder leading to MotoGP. Promising new riders would begin in Moto3, limited to 250 four-stroke singles from a limited number of “regulated” designs. The successful would advance to Moto2, all of which machines would be powered by identical Honda CBR600RR inline-four engines, in an artisanal chassis of the team’s choice. Those advancing to MotoGP would ride true prototype motorcycles, each designed and built top to bottom by its manufacturer in the classic manner.

These changes eliminated the expensive engine development that had previously made the 125 and 250 classes so exclusive. It was hoped that Moto2 would “unleash a storm of chassis innovation.”

There has been Moto2 chassis innovation, but you have to look closely to see it. And it is highly significant, despite not being of the visually obvious sort based on forkless steering or aerospace hybrid carbon/Kevlar laminates.

Kalex’s Moto2 chassis won the first round of Moto2 in 2020 and also claimed the next four positions behind.Kalex Engineering

For 2019, Moto2 switched from Honda 600 power to Triumph’s 765cc Triple, requiring new chassis. The first (and so far, the only) Moto2 race this year—that at Losail Circuit, Qatar—was won by Tetsuta Nagashima on a Red Bull KTM Ajo team entry in KTM colors, on a Kalex Engineering twin-beam aluminum chassis (Kalex has had a long cooperative relationship with KTM). All of the top five rode Kalex, and of the 25 finishers, 17 (68 percent) rode Kalex chassis.

Kalex is the chassis to have in Moto2.

Riders on Speed Up chassis were sixth and eighth. KTM, true to the last with its welded steel-tube chassis, withdrew its own chassis entries from the class at the end of 2019.

Jorge Navarro was the top finishing rider on a Speed Up chassis at Qatar.MotoGP.com

All of the chassis in this class are beautifully made, displaying the highest class of machine work and welding while having the smoothly flowing shapes that best resist cracking in aluminum structures.

Kalex is the chassis to have in Moto2. Why? Rider Sam Lowes said, “If our setting was perfect, the Speed Up was as good as the Kalex. But 99.9 percent of the season it was no advantage to be on that bike, because our setup window was much narrower than that of Kalex. One weekend my bike was simply great and the next I had no chance at all.”

Lowes also noted that because so many riders are now on Kalex, that constructor’s information base is very large. It is also possible that Dunlop, who provides Moto2’s spec tires, are doing what comes naturally in racing—designing tires for the front row.

More than two-thirds of the Moto2 teams use Kalex frames, citing consistency and easier setup as the reasons.MotoGP.com

Swiss Moto2 rider Thomas Lüthi had ridden a Suter chassis in 2017, but that builder then left the class. Lüthi said, just before the 2018 season, “When I moved to the Kalex, if anything I think it might have been slightly worse but we found more consistency, and it was that consistency that I was looking for.

“If you find a perfect or near perfect setting on the Suter, then that bike is really great. If you have a bad day with settings on the Kalex, you can still make the podium, but if you have a bad setup day on the Suter, then you’d be fighting to be in the top 10.”

This has its parallel in the world of dirt-track cars. A car with a more flexible (“softer”) chassis is easier to set up, while a car built with greater chassis stiffness (influence coming from F1) requires much more from its suspension and so is harder to set up to go quickly.

Lüthi said the Suter chassis, when correctly set up, was more precise than the Kalex, more like a MotoGP bike.

Suter’s frame was more precise than the Kalex, but was more difficult to find a correct setup.Suter

“But just to find this setup is damn hard. The Kalex is not as precise and it moves more, but you can thus still be traveling very fast.”

Not as precise? Moves more? These are the criticisms Casey Stoner made of the quite flexible Ducati steel-tube “trellis” frame in 2008; “On that thing you can’t hit the same point two laps running.”

Much of this is surely the steer delay that a degree of lateral chassis flexibility imposes.

Looking down on the Kalex chassis, one is struck by how much the lateral thickness of its side beams tapers from front to back. If there is to be flex, this taper places most of it at the rear of the beams. Looking likewise at the forward engine attachment points, they become quite thin at their extremities. It is as though the forward chassis were a quite rigid four-legged “spider” surrounding the engine and holding the steering head at its front. At its extremities it has zones of flexibility that provide the lateral “give” that can keep the front tire in contact with the pavement.

Changes visible in recent Moto2 chassis include opening up the steering-head area to provide extra intake airbox volume. The steering head itself is made narrow so that carbon ducts fitted closely on either side can send air from a central nose intake to the airbox, with minimum energy loss. From at least as long ago as 2014 Moto2 makers began to sheathe the inner or outer vertical faces of their side beams with carbon fiber as a means of increasing resistance to steering-head tuck from braking loads. Everyone is using elaborately machined parts which allow accurate local control of wall thickness—no more slapping frames together from a machined steering head plus two uprights and lengths of constant-section extruded side beam. Where should flex occur, how should it be distributed, and how much is too much? As they say in F1, “To design next year’s winner you have to have designed last year’s.”

In 2010, the first year of Moto2, the Moriwaki chassis closely resembled the chassis of the production CBR600RR and Honda’s 2009 RC212V MotoGP bike. All of these designs shared the longer front engine mount spars that are one element in allowing the steering head to flex laterally by a few millimeters—an innovation from 2002. In 2010, the Gresini team and Toni Elias won the first Moto2 championship on the Moriwaki chassis while Kalex failed to score a single point. By 2012, competition from other chassis makers caused Gresini to switch from Moriwaki to Suter.

How can a designer know the side effects of building in a given degree of lateral flexibility? Will the resulting flex introduce undesired flex-steer? Will riders be spooked by “movement”? Will stress introduce upsetting gyro loads if the front wheel twists out of plane with the rear?

The old way was to build a series of chassis, build up testbikes, order in a stack of tires, and set highly paid test riders to doing fast laps. Another way—taken by former 250 GP rider Martin Wimmer in developing the MZ tubular Moto2 chassis—is to apply stress to your chassis with a long steel bar and see where the deflections appear by having a small forest of dial gauges bearing against various parts.

The digital equivalent is to model the chassis as finite elements and then to apply the various expected stresses in the process called “dynamic FEA.” It is possible to write software that will change design dimensions by small increments and repeat the testing, over and over through vast numbers of iterations, such that desired values are approached by successive approximations. This sounds otherworldly but it is just less familiar to us than brute trial-and-error or steel bars and dial gages. Aviation has used these techniques for decades and now the low cost of computing brings them to a greater number of users.

Dynamic FEA allows engineers to make changes and test more iterations of a chassis than would be possible through prototyping frames and applying physical stresses.Kalex Engineering

Kalex now has more than 10 years of this design experience, such that when it applied what it knew to the unknown case of a chassis for the Triumph Triple introduced to Moto2 in 2019, at the first Jerez rollout of that chassis, rider Jesko Raffin said after five laps, “It feels like a Kalex.”

Thanks to the great numbers of chassis hardware photos available on the internet, we can look at earlier chassis in a new light. The Honda RC30 Superbike beloved of collectors has a massively braced steering head from which emerge hefty side beams of constant section—all of it clearly intended to be rigid in all directions. At the time, this was thought to be the key to best lap times in 500 GP. Those gains were finished by 1993, replaced by the “chatter, hop, and skating” experienced by Wayne Rainey at the Australian Grand Prix that year.

This stiffness is now known to cause vague front-end feel and sudden loss of front grip—as Ducati discovered with its super-stiff carbon MotoGP chassis of 2009. Honda’s RC30 chassis is beautiful—its machining and welding are of the highest order. It is a jewel of chassis artistry, but it just happens not to have worked very well on other than quite smooth pavement. That bike did win the first two World Superbike championships—to a large extent because its acceleration was superior to that of its Ducati competition.

As they say in F1, “To design next year’s winner you have to have designed last year’s.”

Kalex principal Alex Baumgärtel says philosophically, “Most riders say that our chassis is softer than the Suter, while others say the exact opposite. We have never tested the Suter for stiffness or geometry because you just have to go your own way.”

Alex Márquez, brother of current MotoGP champion Marc Márquez, was 2019 Moto2 champion on a Kalex. Right now, Kalex’s understanding of what a chassis must do to win championships comes closest to the ideal. What next?

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