motorcycle aerodynamics?

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iwannadie · #1 Unread post by **iwannadie** » Mon Mar 21, 2005 1:57 pm

wasnt sure which board to put this so...

i was wondering every one says how bad bikes are for aerodynamics, i just dont see how this is, i mean you have such a small profile cutting through the wind compared to a car. do they mean bikes have no down force like a car does or bikes have more wind drag? im sure a big cruiser compared to a busa is a big difference, but i herd the busa is still 'very poor' when it comes to the aerodynamics. but to me the thing looks like it would have very little drag....

oldnslo · #2 Unread post by **oldnslo** » Mon Mar 21, 2005 2:16 pm

Bikes are notoriously poor in the aerodynamics department, but even worse, bikes with riders are far worse. Bikes like the Busa were wind-tunnel tested, I think with a tiny rider figure strapped on, in full racing tuck, to determine the least drag that could be had. I doubt there is a bike made whose coefficient of drag matches that of a Dodge Neon. The bigger you are, the worse it is.

Coach · #3 Unread post by **Coach** » Wed Mar 23, 2005 2:37 am

There isn't a bike made that's aerodynamic with me on it....

poppygene · #4 Unread post by **poppygene** » Wed Mar 23, 2005 3:13 am

Bikes are dirty, aerodynamically speaking, and there's really no way to improve it much - short of full, front-to-back bodywork. Who wants to ride in an egg? Not me.

An excerpt from Doug Meyer, of Sport Rider:

"The drag caused by the frontal area of the vehicle as it moves through the air is the major component of the drag equation. The rest is composed of a little number called the drag coefficient, or "Cd." The Cd is a computed value based on the measured drag of various shapes moving through the air. A flat disc presenting its face to the airflow has a Cd of about 1.0. A well-designed aircraft, like the Mooney, has a Cd of about 0.3. The average, late-model automobile has a Cd of 0.3 to 0.4, with a carefully designed Bonneville Salt Flats streamliner cutting in as low as 0.1. A modern sport bike, on the other hand, has a Cd between 0.5 and 0.6, which, interestingly enough, is about the same as a bus. The Cd is largely independent of size, but is determined mostly by shape. This is where the "conventional" motorcycle suffers.

While the front wheel, forks, brakes, handlebars and rider do not present a very unified front to the oncoming air, a motorcycle actually has such a poor Cd because of the untidy way in which the air rejoins after the bike passes through it. Low-drag shapes must be as streamlined at the trailing end as at the forward end. In fact, in any truly streamlined shape, it is the closure of the airstream that has the greatest effect on the total drag. Any really low-drag shape must address this, and conventional motorcycles don't.

There is a limit to what brute power can accomplish. Even Terry Kizer's 459- horsepower ZX-11 turbo has "only" gone 230 mph, greatly due to the horrific aerodynamic drag created by its slick-looking (as motorcycles go), but not aerodynamically slick, shape. If we could, we'd be better off trying to get our bikes more compact with less frontal area to impact the wind rather than more streamlined: It's the frontal area that plays the greatest role in the overall drag equation. But, we can get only so small."

vulcanman500 · Wed Mar 23, 2005 3:22 am

Coach wrote:There isn't a bike made that's aerodynamic with me on it....

iwannadie · #6 Unread post by **iwannadie** » Wed Mar 23, 2005 4:31 am

cool thanks for the info, sounds more like the air flow coming off the back is the problem and not so much the front end... be funny to see a clear plastic egg dome around a bike though to improve the aero ; p

oldnslo · #7 Unread post by **oldnslo** » Wed Mar 23, 2005 5:37 am

Maybe it would help to have your body perforated..which would help with weight, too.

Nibblet99 · #8 Unread post by **Nibblet99** » Wed Mar 23, 2005 5:39 am

oldnslo wrote:Maybe it would help to have your body perforated..which would help with weight, too.

only if you remove the rings / studs from the perforations, before hopping on the bike

iwannadie · #9 Unread post by **iwannadie** » Wed Mar 23, 2005 5:51 am

i have half inch holes in my ear lobes, i wonder how much drag that cuts down ; )

Nibblet99 wrote:
oldnslo wrote:Maybe it would help to have your body perforated..which would help with weight, too.
only if you remove the rings / studs from the perforations, before hopping on the bike

Wed Mar 23, 2005 5:57 am

While motorcycles have "not so great" aerodyamics, they do make up for it in horsepower to weight ratio and gas milage! I'd like to see a Neon do all that, even the Dodge SRT-4 can't compete.

Manufacturers do try to make good aerodyamic bikes, take the Kawasaki Ninja ZX-12R. Kawasaki gave the ZX-12R to it's airplane department to design for optimum aerodyamics. That's why it has "little wings" on the front fairing.

Mike.