How the new CBR600RRs aerodynamics compare to a MotoGP bike

Dailies -

By

12Nov_CBR600RR-Aerodynamics_02_gallery_large

This is how the 2013 Honda CBR600RR‘s aerodynamics stack up to the company’s RC212V MotoGP racer. Using Computational Fluid Dynamics analysis to illustrate how the bikes interact with the air, high pressure areas are colored red, while lower pressure fades through yellow, green and then blue. As you can see, the road bike is impressively close to the race bike.

The new CBR’s been fitted with a redesigned front fairing that drops drag by 6.5 percent. The new “line beam” headlights slope inwards towards the central air intake, directing high pressure air where it’s most beneficial.

Looking at the two bikes side by side, we can see that the largest high pressure area on both is concentrated around that air intake. Other hot spots include the leading edge of the tire, lower forks, and the rider’s helmet.

MotoGP regulations are famously restrictive on aerodynamics:

2.7.7.1 The windscreen edge and the edges of all other exposed parts of the streamlining must be rounded.
2.7.7.2 The maximum width of bodywork must not exceed 600mm. The width of the seat or anything to its rear shall not be more than 450mm (exhaust pipes excepted).
2.7.7.3 Bodywork must not extend beyond a line drawn vertically at the leading edge of the front tyre and a line drawn vertically at the rearward edge of the rear tyre. The suspension should be fully extended when the measurement is taken.
2.7.7.4 When viewed from the side, it must be possible to see:
a. At least 180 degrees of the rear wheel rim.
b. The whole of the front rim, other than the part obscured by the mudguard, forks, brake parts or removable air-intake.
c. The rider, seated in a normal position with the exception of the forearms.
Notes: No transparent material may be used to circumvent the above rules. Covers for brake parts or wheels are not considered to be bodywork obstructing the view of wheel rims in regard to the above rules.
2.7.7.5 No part of the motorcycle may be behind a line drawn vertically at the edge of the rear tyre.
2.7.7.6 The seat unit shall have a maximum height of the (approximately) vertical section behind the rider’s seating position of 150mm. The measurement will be taken at a 90° angle to the upper surface of the flat base at the rider’s seating position, excluding any seat pad or covering. Any on-board camera/antenna mounted on the seat unit is not included in this measurement.
2.7.7.7 Mudguards are not compulsory. When fitted, front mudguards must not extend:
a. In front of a line drawn upwards and forwards at 45 degrees from a horizontal line through the front wheel spindle.
b. Below a line drawn horizontally and to the rear of the front wheel spindle.
The mudguard mounts/brackets and fork-leg covers, close to the suspension leg and wheel spindle, and brake disc covers are not considered part of the mudguard.
2.7.7.8. Wings may be fitted provided they are an integral part of the fairing or seat and do not exceed the width of the fairing or seat or the height of the handlebars. Any sharp edges must be rounded. Moving aerodynamic devices are prohibited.

All that effectively creates the archetypal shape you see on every GP bike. Aerodynamics would benefit drastically from taller screens, larger fairings and longer tails. Fairings on street bikes like the CBR are largely styling exercises, again failing to truly push aerodynamic efficiency in the name of GP-like styling.

Having said that, it’s notable how much greater the GP bike’s screen is at protecting the rider from the wind. The hotspot there is considerably smaller than that on the CBR’s helmet, illustrating the benefit tall or “double bubble” screen bring and why you see virtually all production-based race bikes fitted with them.

via Honda

  • http://www.facebook.com/andreas.alm.315 Andreas Alm

    What about the rear? As far as I know this is more important in the quest for lower drag; space under seat behind frame, tail shape, hugger.

    • http://RideApart.com/ Wes Siler

      It’s hugely important, but is largely unaddressed on GP bikes due to the regs and, as a result, most street bikes don’t bother either. One big exception is the Hayabusa. Its tail is large, tall, long and bulbous, specifically to try and close the airflow behind the rider with minimal drag.

      • http://www.facebook.com/yannis.tsiapas Yannis Tsiapas

        Correct, the ideal shape, is that of a raindrop

        • MonkeyPaintR

          Except the shape of a raindrop isn’t the ideal shape.

        • nightscout13

          Correction, a tapered front, tapered rear. A raindrop would have one side that’s too bulky.

  • R_Melaun

    Most of the drag comes from the rear of the bike as the airflow there is almost entirely turbulent. If it could be controlled, its pressure could be raised as it slows while leaving the bike and rider. The Czysz attempts to do this with its various aero devices at the rear. In reality, bikes are way too short for optimal airflow (as defined as least drag).

    If my memory is correct – which is doubtful – a slenderness ratio of around 6:1 or 7:1 would be necessary. That ratio would make for a rather lengthy bike.

    • Adrian MacGeraghty

      Yep. The ‘blue’ is just as bad as ‘red’. I wanna see the back ends, too.

  • http://twitter.com/GeneCash Gene Cash

    And in other news, similarly shaped objects have similar aerodynamics!

    I remember when Al Bowers put the Ninja 900 in a NASA wind tunnel in ’84, and found the slightly-sunk headlight negated the benefits of the entire rest of the fairing.

    Speaking of production vs MotoGP… at Jerez, the top 1000cc WSBK bike was 7/10ths faster than the top 1000cc MotoGP bike. http://superbikeplanet.com/2012/Nov/121129az.htm Suck it, Carmelo Ezpeleta.

    • TP

      To be fair, Laverty’s lap would have put him third on the grid for the GP race at Jerez this year. Which was where Nick qualified

  • http://twitter.com/bloodfalcons motoguru.

    That’s pretty wild.

  • http://www.facebook.com/corey.cook.549221 Corey Cook

    I like that the computer modeled rider on GP bike is clearly wearing a racing suit while the rider on CBR is clearly wearing a T-shirt. Hey at least Honda know’s who their demographic is…

    • rohorn

      Does this mean that T-shirts with speed humps are next from (fill in the blank moto gear company)? In Spectra/Dyneema, of course.

  • http://twitter.com/MotoCzysz MotoCzysz

    Font view is typical, the 3/4 views look inconclusive, maybe a study of cross winds?(where did this model come from?) The front is easy, the real magic occurs behind the rider.

  • mintpaul

    Just proves how uncomfortable modern sports bikes are for real world riding…

  • AM3RIG

    interesting…