Guest Blog: Mat Oxley - Carbon-fibre MotoGP: it’s a long story

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.


Carbon-fibre MotoGP: it’s a long story

It’s almost 40 years since MotoGP’s first carbon-fibre chassis, so with Honda’s and Suzuki’s latest carbon-fibre frame coatings, how long before we see the next fully carbon MotoGP bike?

Back in the early 1990s when Kenny Roberts’ Marlboro-moneyed Yamaha 500cc and 250cc team bestrode motorcycle racing the ‘King’ walked into the paddock each morning carrying a shiny carbon-fibre briefcase.

The briefcase – paired with Ray-Ban Aviators and a big, fat Rolex – was the ultimate statement of racing intent: a man at the cutting edge of motorsport technology and with money to burn.

Carbon fibre became the standard chassis material in Formula 1 during the early 1980s, after McLaren engineer John Barnard designed F1’s first carbon chassis. But you can count on the fingers of your hands the number of motorcycle grands prix won by carbon-fibre chassis.

Carbon fibre arrived in bike racing grand prix paddocks in 1984, when Niall Mackenzie raced an Armstrong 250 with carbon-fibre chassis, fabricated by car constructor Reynard Motorsport.

The exotic aerospace material was first used in the premier class by Honda in the same year, when HRC equipped its first NSR500 with carbon-fibre wheels. Crucially these reduced unsprung mass to improve steering and handling.

Freddie Spencer and the carbon-wheeled NSR nearly won the 1984 Daytona 200 – a shakedown outing for the season-opening South African GP, where disaster struck. A rear wheel collapsed during practice, Spencer crashed and he was out of the race. What few knew at the time was that the American had noticed the NSR handling strangely as he flew around the Daytona banking at 180mph during the final laps of the 200. That’s when the wheel had started to fail.

Spencer’s accident taught HRC plenty and no doubt made bike people wary of carbon fibre. Indeed carbon-fibre wheels are now banned, but due to costs and concerns about rims getting damaged during frequent tyre changes.

The NSR’s carbon wheels came from Honda’s most exotic grand prix bike, the oval-piston, 32-valve, 21,000rpm NR500 four-stroke. The NR made its debut at the British Grand Prix in August 1979 (which made this year’s Silverstone event the 40th anniversary of Honda’s current participation in GP racing).

The NR never scored a world championship point against the all-conquering two-strokes, but it was a rolling laboratory for Honda engineers. In 1983, HRC built a futuristic NR500 with a full carbon-fibre chassis: carbon frame, carbon swingarm, carbon wheels, carbon brakes carbon fork sliders and a carbon silencer. The bike was never raced (by then HRC was winning with the NS500 two-stroke) but it pointed the way to the future.

Nowadays all MotoGP bikes have carbon brakes, most have carbon-fibre fork sliders and many have carbon-fibre swingarms.

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

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When Rossi was on the Ducati, and having nothing but problems, everyone was pointing to the CF frame and saying 'that's the issue....you need an aluminum frame'. A buddy of mine worked for Rockwell, had two Ph.D degrees, his work was classified 'Top Secret' (I never knew what he really 'did'), and he loved riding his motorcycle. When I told him about the CF frame issues/have to use aluminum, he laughed, saying CF was WAY easier to work with and you can design it with any stiffiness, varying stiffness, flexible in the middle/stiff at both ends/etc/etc/etc. Any/every variable of stiffiness, flexiblity, twist you could want/need could be designed into a CF frame. Hmmm.....

Total votes: 10

Don't forget it had the engine as a stressed mamber in the middle, having little more than a airbox and headstock to work with has to limit what flex characteristics can be made regardless of the material.

Total votes: 5

I have to confess I don’t really understand some of what’s being talked about in the great frame debate and would appreciate a ‘frames for dummies’ explanation! I get it that flex gives an extra element of suspension and therefore better grip on bumpy corners, allowing later braking, higher corner speed, faster exits etc. But I don’t understand why, for instance the headstock flexing thus putting the wheels out of line, of itself allows the bike to turn better. I’d have thought this keeps the rear every so slightly less leaned over than the front and while that allows you to get on the gas earlier, the lean angle on the front is still whatever is necessary to make the turn. Obviously I’m missing something about mechanical engineering here!

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G'Day Lilyvani I'm surprized nobody else was weighed in on this subject. So I will brake the ice. Most likely I will made a blunder or two & the smart people will eventually feel the need to correct my mistakes.

I'm talking about the entire enginebicycle here. Like all things motorcycle related it's a compromise.

Totally rigid doesn't work the best, totally flexible is no good either.

Tires are the key, different tires require different frames to get the maximum performance.

Mainly flex is important when leant over. as the suspension movement is in the wrong plane in this situation.

Torsional stiffness is very important, while lateral flex is considered good

Braking is mainly happening with the bike close to straight up and down. although releasing the brakes is an issue & that often doesn't happen until well deep into the corner at a big lean angle.

"higher corner speed, faster exits " yes if the flex is right it will help with these two very important aspects of a fast lap.

One thing I like to say regarding " putting the wheels out of line ". The rear tire is so wide these days compared to the front, that any time the bike leans the tires are out of line. That is (at full lean) the centre of the rear contact patch is roughly 90-100 millimetres out from the centreline of the bike, whereas at the front the contact patch is only 50 or 60 millimetres offset. So the wheels are out of line on the angle unless the tyres are both the same size and profile.

Feel is probably the most important characteristic when it comes to riding a motorcycle near to the maximum performance. If the rider cannot feel where the limit is, then it is difficult to push hard without going over the edge. If the chassis is too stiff it is harder to feel where the limit is.

Found a couple of articles for us to read. Mat Oxley again for a start

https://www.motorsportmagazine.com/opinion/motogp/why-motogp-has-gone-soft

Kevin Cameron is also awesome, in that article the Colin Edwards 2002 championship winning VTR1000 is mentioned. Apparently they removed one engine mounting bolt to give the Honda a bit more flex, & The Texas tornado went faster & won the chip.

https://www.cycleworld.com/2015/10/16/motogp-racing-chassis-flex-and-sta...

There was some dicsussion of this issue in the forum, I'm not sure where at the moment.

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I guess I’d probably need to do that mech eng course I always fancied in order to really understand the physics. Or settle for just being in awe of how far over these things can be leant, and the faith of those who do so.

Total votes: 1