Improving Aerodynamics

[donpearsall]

I have read in various bike mags that the Hayabusa is already very efficient in its aerodynamics. The fairings, etc are about as good as you can get them.

1. For speed runs over 200mph, is there anything that can be improved in the fairings? I mean short of making it into a streamliner?

2. Considering that the frontal area is pretty wide already because of the radiator and oil cooler, does it make sense to lower the frontal area more by putting on a narrower tire/brake/fender? Would there be any gains from this?

3. On high speed runs, I have seen riders with their helmets above the windscreen. Does that cause more drag, or are the helmets actually in the wind shadow area because the windscreen deflects the air up and over?

Thanks

Don Pearsall

 

[Pop]

Get a midget to do the run for you!

 

[AZIROC]

where *if even possible* could u get the fairings like on the ELF racing busa?

 

[DAB]

Jump off when you reach 200...

 

[RandomNickname]

The aerodynamics on the bike are the lowest on any stock bike.

However once you throw on a rider, some of that goes away, and no matter how low of a tuck you go into, your arms and legs (which do cause a great deal of turbulence) are still going to cause some interruption of the aerodynamic goodness. Of course the same is true for any other bike you get on, so it's feasible to argue the slipstreaming qualities of the Busa are still second to none.

As far as narrowing the tire helping, in a word, no. Basically your nose fairing and tire are punching the initial hole for the bike to come through. If anything narrowing the most forward bits of the bike would cause it to punch a smaller hole, which in turn would cause more turbulence once the air hit the main body/radiator/rider.

As far as helmets being over the screen, how high over the screen are we talking? a couple of inches? the entire helmet? That would make a huge difference.

 

[NearDeath]

1. You can go with racing plastics, this will help...
2. mirrors don't cause much drag, but every little bit helps...
3. Check out "Project260's" bike in the top speed section under the 300MPH post... That should give you some ideas...

 

[him]

where *if even possible* could u get the fairings like on the ELF racing busa?

talked to the dealer 8k for carbon fiber and 5k for regular plastic

 

[NearDeath]

where *if even possible* could u get the fairings like on the ELF racing busa?

talked to the dealer 8k for carbon fiber and 5k for regular plastic

Yea, plastics are worth 8k...

I don't care if they gave another point on your aeros, I could add a lot more HP for 8K

 

[frisbee]

So many variables , Even waxing can help reduce windage . you have to think about every screw that sticks out , your outfit , your tuck , it all adds up . I plan on joining the 200mph club at salt lake soon.

 

[Phantom12]

1. Get rid of your mirrors

2. Slam the bike down

3. Remove reflectors

4. Double bubble windscreen

5. WAX



Other things that are non aerodynamic but show improvement...

Smaller tires (180 rear)

Supersoft rear to reduce tire slippage at high speed

Hard street tire up front to reduce rolling resistance.

Inflate the front tire heavily (42-43psi) and keep your rear at 38-39psi, less rolling resistance

Lightweight oil helps the clutch spin faster

Stiff rear compression to prevent the tail from sagging and lifting the front at high speed.

 

[ROBOPTI]

DEAD WRONG ON FEW FACTS Phantom

On all my 230+ runs I have run 8-10 OVER max tire pressure in both tires .. You will loose pressure as the run progresses

I would HIGHLY recommend you not run supersoft in the rear .... medium is fine ... but you will generate enough heat to get even a hard to temp ... the front - i run medium .... a softer tire will tend to delaminate at a high enough speed if they generate to much heat

You WANT the rear to sag/squat as you need weight on the rear wheel to keep positive traction .... the front wheel lifting is NOT that big an issue at all
... A stiff rear will cause excessive wheel spin .... You DO NOT want the bike to "plane out" ... you want your weight as you are accelerating to be direct above that rear contact patch .. .not a wheelie ... but ass end heavy

Another lil fyi .... If you intend to run super high speeds ... 220+ ... 90degree valve stems are a must or somehow seal the stem ... you're valvestems will suck thru and de-pressurize you're tire instantly .... not good

oil etc ... not that big an issue

totally agree on body setup / mirros etc however

 

[theemrrdkill]

Quote:
1. Get rid of your mirrors

2. Slam the bike down

3. Remove reflectors

4. Double bubble windscreen

5. WAX



Other things that are non aerodynamic but show improvement...

Smaller tires (180 rear)

stick with a med compound.

Hard street tire up front to reduce rolling resistance.

Inflate the front tire heavily (42-43psi) and keep your rear at 38-39psi, less rolling resistance

Lightweight oil helps the clutch spin faster

Stiff rear compression to prevent the tail from sagging and lifting the front at high speed.

fyi ..what " POP" said ( Quote#2 ) ..get a midget

 

[Phantom12]

Robopti- 8-10psi over max pressure? I was under the impression that the air in the tires EXPAND as the tires heat up... hence using such high PSI is a dangerous thing. On super high speed runs, you'd think there would be a LOT of heat and therefore a lot of tire expansion. No?

As for the supersoft rear... You want traction in the begining of the run and sufficient traction at high speeds. No? Maybe at 230mph speeds a medium tire is sufficiently heated up... and if at Bonneville... getting a quick start isn't really as important. But on pavement in a limited distance like..let's say Maxton.... Isn't a supersoft tire optimum? I know there are different set-ups for different surfaces... so maybe it's not that neither of us are wrong... just stating different optimum set-ups for different venues?

As for the rear sag...too much of it and you're wheeling the first couple gears... not to mention raising the nose up at high speed which increases frontal area and catches excessive wind under the nose. No?

I understand you need weight on the rear to hold traction... but that's what the supersoft is for... besides, I'm not saying go full hard on the rear compression, just stiff.

Again, if I'm wrong... please explain it to me, further. I'm always willing to learn.

Nice tip on the valvestems... I had no idea. But then again, I've never been 220mph. 203mph on GPS when I hit the revlimiter in 6th... haven't done a top speed test since.

a genuine 200+mph has a way of humbling a man.