Butts Exposed,

[stay`tee]

there have been many photos of late showing naked bike riders standing on the footpegs with their butts up off the seat,, i have ridden this way and there is a definate improvement in speed which i am at a lost to explain why, is it that the riders back is more flatter, dose it let the air trapped in the riders head/chest area escape easier, ,, most folks say its how you close the door, but, with ya butt up there that door aint closed,,
I rode turbocharged dragbikes for many years and found that the stepped seats helped in improving speeds, i always put this down to more weight over the rear slick dimishing wheelslip somewhat, could this be whats happing on the salt, ,,

[kiwi belly tank]

Might be the added propulsion from a bean diet, butt that would put it in the blown class right! 
  Sid.

[Milwaukee Midget]

I'm glad to see this topic finally being aired out . . .

[USFRAMONTE]

Is this what one would refer to as "stand up" comedy?

[maguromic]

Is this what one would refer to as "stand up" comedy?

Only if you are the butt of the joke. Tony

[Bob Drury]

  youse guys really crack me up!

p.s. I would like to take a moment to join Stainless Steele whom I am sure will soon congratulate me on breaking the 2000 Barrier with my 2001st incitefull, knowledgeable, and perceptive post on this site........................... Ol' One Run, out...................

[Seldom Seen Slim]

I'm going out on a limb here, but maybe -- just maybe, mind you -- he asked a serious question.  I know, it's not like what lots of youse guys, yay-hoos that you are, are used to doing, but I'm gonna try to make a legitimate response.

Stay'tee, I'm often gone down the course with lots of my weight on my feet, usually standing on the ball of them.  I move my butt up and down and back and forth looking for more speed and traction.  Traction from weight-placement changes and speed from both traction and aero.  I've noticed that with my butt a bit off the seat - that I do usually get a touch more speed, and I've assumed that's because of the improvement.  I don't know the aero physics behind the straighter back/higher hiney -- but I do notice some benefits.  I keep most of my weight on the balls of my feet during a run whether I'm trying to move around or not, by the way.  I assume it moves y contribution to the weight of the loaded vehicle down a few inches to give a lower CG.

[kiwi belly tank]

The word "naked" in the first post gave me a mental picture I didn't like so I had to figure we were refering to girls on bikes Butt who the hell is doing speed runs naked & why?
  Sid.

[Stainless1]

Kiwi, you mean other than Freud...

One Run... get back to work, did you contact Coonrod yet?

I suspect tail shape has a lot to do with the effect and if it helps.  Didn't seem to help much on this one.  However smaller riders that rode the next year went faster... imagine that... and multiple riding techniques we employed to take advantage of the tail.

[RacerX9623]

From my limited experience racing the mile on a low power bike. I would guess raising your tail flattens your back and reduce the drag from turbulence.

[stay`tee]

it seems to affect all motorcycles, large and small, all with differing tail sections, the only constant of sorts is the riders position,
 i have tried it with fairings on and there is a slight increase in speed, however without fairings i can feel the bike uummm "loosen up", feels free'er cutting through the air and there is a definate increase in speed of approx 3-4 mph at 190+, this indicats that maybe its aerodynamics, "butt" , where do you think this improvement is comeing from, ,,

[maj]

My best guess would be the raised butt has less surface area or more accurately wetted area from the rear  for drag than a persons back at 45 deg or so  and disturbed air beyond that point has less to interact with

Ronnie if i bring a bucket to the lake we can test  

[stay`tee]

in my situation it changes the angle of my back (approx top of helmet to base of spine) from 35* down to high teens,, ,,

actually there are phots from the old days showing riders with cones strapped to their backsides, appears thay were onto it back then,  ,

[wobblywalrus]

The method has been used as long as I can remember to get a little extra speed on the straightaway during a road race.  Not many people do it.

[tauruck]

Bike aero must me the most difficult of all.

On a car the surfaces remain constant.

The wind tunnel must be the best option for finding solutions.

Check the lengths these guys go to.