Guest Blog: Mat Oxley - Why MotoGP has gone soft

MotoMatters.com is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.


Why MotoGP has gone soft

Frame flex is the black art of MotoGP chassis design. Here’s why chassis are getting softer, not stronger, despite ever-increasing speeds and horsepower

Study this photo of the front end of a Repsol Honda RC213V, particularly the upper triple clamp. Notice how the underside (between the two HRC logos on the left and right) has been scalloped out, so that much of the triple clamp can only be a few millimetres thick.

What does this tell us? That Honda, like everyone else, is making its MotoGP chassis softer and softer.

There are a few reasons for this, but most of all it’s because Michelin’s MotoGP tyres are of a softer construction than the Bridgestones, which the championship used from 2009 to 2015. If the tyres are softer, the chassis must be made softer to match, because both must work together in harmony.

“Historically speaking, the Bridgestone tyres had a much harder construction, so everything was much harder: the triple clamps, the chassis and many other parts,” says Takeo Yokoyama, HRC technical manager. “Since Michelin tyres were introduced we are going softer and softer, to get more feedback, to get more feeling and to make the bike turn better. We are still going in this direction.”

There have been other changes since the Michelins arrived. The stiffer Bridgestone slicks required a lot of load to make them work, so chassis became shorter to increase load transfer to the front tyre on the way into corners and to the rear tyre on the way out of corners. The Michelins need less load, so some factories have slightly increased wheelbase since 2015, while also raising the centre of gravity to ensure the bike still drops into corners nicely.

However, chassis stiffness is the most fascinating area of chassis design and it’s still as much a black art as a science. Engineers want the frame and ancillaries to offer excellent longitudinal stiffness, so the bike stays straight and stable while pulling 1.5g during braking, and they also want enough stiffness so the bike reacts to rider steering inputs.

But once the bike is on its side the chassis needs to flex laterally, because the front forks and rear shock don’t really work once they are past 45 degrees from the vertical. A few millimetres of lateral (sideways) flex provided by a softer frame, swingarm, triple clamps, forks and so on allows the bike to track bumps and ripples better, so the tyres grip the asphalt more effectively, which, of course, is what racing is all about.

More grip can deliver more corner speed, but it also delivers more turning. This is currently one of the engineer’s biggest jobs in MotoGP – helping Michelin’s front slick make the bike turn quicker.

Ducati still struggles in this area – remember Álex Rins riding around the outside of Andrea Dovizioso at Jerez and Valentino Rossi doing the same at Termas? – and Gigi Dall’Igna knows that too little flex in the right places is part of the problem.

Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.

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Comments

Talk about softness and flex, and not a word about frequency.  :(

Missing the forest for the trees.

Total votes: 8

Oxley has been around a while. We all know with age stiffness AND frequency come down a good bit. But we have appreciation for nuance and know what we are doing too, so...wait. What?
;)
Looks like he started with the Honda and carbon fiber sleeving, and talked with someone at HRC. Plus referred to "way back when" memories. Perhaps the reference to dampening the aluminum frame is also a sloppy way of referring to resonance? And Suzuki/Yamaha seem to be more the tuning fork corner, maybe they would articulate things differently. I guess the forest has several types of trees too eh? I liked the article, albeit wishing it was much more in depth as well.

The Honda may really be after both with this carbon fiber overlay. The combo is interesting. And very tuneable easily relative to a whole new frame (but good luck getting two of them to feel the same). If we are considering the softer carcass of the Michelin, and changes in chassis to compensate, this is a good start. The question indicating that Yamaha have not done so sufficiently and may be left w a ridgid stiffy sounds legitimate to my layperson's ears. If one consideration comes FIRST, it would seem to me to be flex characteristics matching tires.

And then ALSO frequency. Which Yamaha has had in sweet tune, and shall again before this 2019 concerto concludes. The Honda isn't as far off, nor has DNA as dependent on frequency (the rodeo bronco does fine w good old fashioned front porch music, while the carving knife preparation has a symphony of instrumentation).

Yet again, don't all current considerations leave one listening closely to the Suzuki? Music parallel geekout - Like finding yourself amazed that a small handful musicians are making ALL that amazing sound. That you have never heard before. Live. (Remember noticing Pink Floyd "live at Pompeii," Yes "close to the edge," Led Zeppelin et al?). Still gives me stiffness, and hearing a full symphony doing it detracts from the essence. For two years, call Yamaha Deacon Blue. Suzuki is the best Yamaha out there now. Yamaha has relied too much on proprietary electronics to sort their bikes, like over-production hinders live performance for Sgt Pepper's. But good morning, they are fixing their hole with a little help from friends at SIC and Euro testing, and getting better all the time.

Total votes: 12