Valencia Test Deep Dive, Part 2: Ground Effect - KTM And Ducati Follow Aprilia's Lead

Maverick Viñales at Valencia aboard the Aprilia RS-GP. Photo: Cormac Ryan Meenan

For the past few years, Ducati have been the manufacturer pioneering the direction of development in MotoGP. Ducati will come up with a new idea, which the other manufacturers will hastily copy, with a greater or lesser degree of success. Holeshot devices, ride-height devices, winglets. The latest example of this are the tail fins, the four winglets sticking up from the tail of the Desmosedici, which have suddenly also sprouted from the tail of the Honda RC213V and the Yamaha M1.

(As an aside, what do these tail winglets do? Riders report they give better stability, especially under braking. They are too tall to be purely vortex generators – which would reduce drag by smoothing the boundary layer of air on the tail. A possible explanation is that they are directing the airflow coming off the rider, the least aerodynamic part of the motorcycle. But they could also be helping to keep the tail of the bike straight under braking once the load disappears from the rear wheel and shifts to the front. But I digress.)

At Valencia, we saw something new. Instead of everyone copying Ducati, Ducati and KTM were suddenly copying Aprilia. The fairing lowers of the Ducati and KTM were suddenly sporting the wide, flaring bulge which the bikes of Aleix Espargaro and Maverick Viñales have had since the Barcelona test. Ducati and KTM were merely following the example of Honda, who tried such a fairing at the Misano test in September.

The Honda RC213V of Marc Marquez at the Misano test, complete with bulbous lower fairing. Photo: Niki Kovács
The Honda RC213V of Marc Marquez at the Misano test, complete with bulbous lower fairing. Photo: Niki Kovács

What is the purpose of these lowers? And how do the versions used by Ducati and KTM compare? Here's a deeper dive into what we saw at Valencia, based on photos taken by Niki Kovács and Cormac Ryan Meenan.

To start off with, a comparison between a standard Ducati – in this case, the GP21 of Marco Bezzecchi during FP3 before the Valencia race – and the version of the fairing tested by Enea Bastianini at the test on Tuesday.

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Source: 
year: 
2023

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Comments

In aviation, ground effect is higher pressure underneath a wing when its close to the ground, creating more lift with less drag.  I haven't quite figured out how ground effect is supposed to be low pressure and suction when applied to a motorcycle fairing.

It's just something that works better when in close proximity to the ground. Same same but different. The flow speeds up, so the pressure drops. A lot can be happening as the fairing shape moves away from the ground again moving towards the rear wheel. This will also depend on everything else that's going on such as the slipstream and the turbulence created by the wheels. One key to making it work very well would be to stop the flow slowing down as it moves rearwards. Hugely open and leaky I don't think it will be producing much downforce but crucially the side of the fairing away from the ground will be producing next to nothing in comparison and the vector of whatever force it does produce is somewhere not too far from perpendicular with the track. Real downforce in the lean instead of some halfway house component of force inline with the chassis.

Just a random rambling thought from someone with absolutely zero understanding of aerodynamics: could the difference be that in an airplane the airflow and ground effect principles are based on the wings generating lift, whereas on the bikes the fairings are not designed to generate lift? I'm probably wrong, but it's not like it's the first time.

Actually that’s the best explanation. Aircraft wings are intended to provide lift, vehicle wings or other shapes are essentially upside down wings and are intended to provide downforce.  The ground effect amplifies the wing effectiveness; more lift for a plane, more downforce for a vehicle. One of the reasons is that the airflow near the stationary ground is slower so the velocity difference between the “top” and “bottom of the wing is greater than if it’s moving through air further from the ground. But the benefits come at the cost of more drag. 

the stegasaurus wings on the back imho also acts as spoilers when leaned over in corners, pushung the rear down creating more traction on corner exit

The lower you can run the car the more down force. Lowers the air pressure under the vehicle as the air speeds up

"Motorbikes are more like airplanes than cars" - someone in MotoGP engineering that is technically smart (I forget who, I want to say Furusawa)

David, one would assume with the new fairing lowers increasing grip that the mid corner speed would have gone up from two years ago. Would this be true? (is it possible to even find these figures out?) . . cheers