Why is MotoGP going carbon-fibre crazy?

So what’s so magical about carbon-fibre?

That ability to accurately create a chassis that’s light and stiff in some areas and light and flexible in others is what makes it so ideal for MotoGP.

“The fundamental of the material is that you can build something that’s light and strong or light and stiff — many people don’t realise there’s a difference — or light and flexible,” Barnard adds. “You can do whatever you want, depending on how you lay it up, which materials you use and so on.”

Barnard thinks KTM and Aprilia are probably using the M46J carbon-fibre-reinforced-polymer popular in F1.

“M46J pushes you well up the stiffness scale but maintains a very good strength and importantly you can lay it up over fairly complex shapes. If you go to something like M55J, which is super-stiff, you have to be very careful when you’re laying it up, because the fibres are so stiff you can break them.”

But why has KTM’s carbon-fibre frame made the RC16 so much faster out of corners?

Barnard believes the new frame must have more torsional stiffness than the steel unit, so the RC16 finds more drive grip on corner exits, when the bike is close to the vertical.

“They’ve most likely got it stiffer than the original frame, so the suspension can do its job, rather than the frame flexing,” he continues. “Whether you are using a steel or aluminium frame it’s basically a piece of elastic. It might be an extremely stiff piece of elastic but it’s still a piece of elastic and with elastic you have no control over it, no damping.

“So you build the chassis as stiff as you can make it in that area and then you work on the suspension to control the bike. If the frame isn’t totally stiff you’re confusing the suspension.”

And then there’s the weight-saving. The RC16’s frame is two kilos lighter than the steel frame, a useful gain.

“Light weight is everything. When I worked for Kenny I kept banging on about weight, but nobody seemed to worry about it. It was kind of, ‘We’ll worry about weight later, let’s get the thing going around the track first’. No! You have to build the bike from the beginning with weight in mind.”

Barnard is still fascinated by MotoGP, because of the challenges of making a chassis work at extreme lean angles.

“When you look at a bike leaning past 60 degrees you think, ‘how the hell do they get the load into the contact patch of the tyres?’ And when the rider goes over a bump the forces are going into the tyre vertically, so all the forces are trying to twist the swingarm and bend the forks.”

Like many car engineers who have worked on bikes, Barnard has a hatred of the telescopic fork.

“The worst thing you can do with a sliding member is put a side load into it, because then you’re binding it up, so you’ve made the made the reaction of going over bumps more difficult for the forks.”

This is another reason why a MotoGP chassis — the frame, swingarm, forks and triple clamps — needs to laterally flex at full lean, because the suspension is mostly useless at this point.

The big question is when did MotoGP engineers realise that chassis need to flex, because for the first three decades and more of MotoGP they simply built chassis as stiff as they could.

I recall Eddie Lawson scoffing at Honda engineers in 1989, when they told him the NSR500’s chassis “needs to bend like a tree”. Lawson wanted to go the other way, so Honda made a dozen or so new chassis, each stiffer than the last, and he won the title, so…

But there’s no doubt MotoGP engineers starting thinking about chassis flex in the 1980s.

Not in the early 1980s, when the first all-carbon-fibre GP bike — the Armstrong 250 designed by Mike Eatough and fabricated by car racing company Reynard – was raced by Niall Mackenzie.

“That was all about light weight — the bike weighed about ten kilos less than all the Yamaha TZ250s,” says Mackenzie. “The chassis was incredibly stiff, so we’d get chatter if the suspension wasn’t dead right.”

But definitely in the late 1980s, with Honda thinking about bending trees and Suzuki’s British-based 500 team thinking the same way.

In fact, factory Suzuki GP mechanic Paul Boulton remembers the exact moment he realised that mid-corner chassis flex was the way to go.

“We were watching at Clearways at Brands Hatch,” Boulton recalls. “There was a bump in the middle of the corner and every time our bike went over the bump it jumped across the track because the bike was so far over, the suspension basically wasn’t working. That’s when we said, ‘We need some flex’.

At that time Suzuki already used a carbon-fibre chassis of honeycomb design – basically a carbon-fibre sandwich with an aluminium honeycomb filling.

The chassis was created by Nigel Leaper, who built a similar unit, with inbuilt cornering flex, for Suzuki’s first RGV500 of 1987. Since then Leaper has created car composites for McLaren, Tyrrell, Lotus, Ferrari, Red Bull and Williams.

However, Suzuki wasn’t convinced by Leaper’s creation, so the factory remained on the conventional road, with an aluminium beam-frame chassis.

“The RG with the honeycomb was lovely to ride,” says Mackenzie, who raced the bike at the end of 1986, impressing the paddock so much that he got a factory Honda 500 GP deal for 1987. “We were using Dunlops, which I think were more forgiving, so maybe they helped with the chassis. Suzuki also gave a bike to Kevin Schwantz and I beat him at Misano, so I thought I was awesome, but he was running Michelins, which I think is what made the difference.”

What might’ve happened if Suzuki had gone down the carbon-fibre road with its RGV? Would Kevin Schwantz have crashed less and won more than one world title, because he would’ve had more feel and grip?

Over the next few weeks we will see whether the carbon-fibre RC16 works as well at Mandalika, Phillip Island, Buriram, Sepang, Losail and Valencia as it did at Misano and Motegi. If it does you can be sure that Ducati’s Gigi Dall’Igna will be considering a carbon-fibre frame for 2024. And probably Honda and Yamaha too.