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Discussion Starter #1
I am curious if others crouch down over the tank when travelling at speed?

Here is my discovery ...

The boundary layer of the wind coming off the windscreen comes right to my neck. I suppose this is an ideal placement, cuz my helmet is in the quieter laminar air stream. If I bend down just abit, with my helmet in the turbulent zone, the buffet noise is deafening. But, what is it like below the boundary layer?

I started riding on the highways with my head below the turbulent layer. I lay my chest on the tank, my knees are braced against the tank, and my feet (balls of feet) are higher on the pegs. Here are my discoveries:

- Boy! is it ever quiet laying behind and under the windscreen.
- My regular mirrors are out of allignment for seeing rearward.
- The tank is slippery to grip with the knees.
- Steering is very responsive but graceful, cuz I now have no body weight
on the grips, and to steer I can end up pushing horizontally (better) with no ineffective downward force (useless).
- This alternate position helps ward off any body fatigue (but only if I alternate between laid down and upright positions, say each 15 minutes).

To improve the experience, I have added:

1) Secondary mirrors, permanently set for allignment for when I am laid over the tank. This gives me continuous view of any potential tailgaters. (I would never ride when I can't see behind me.) The mirrors were bought at a bicycle store.

2) Adding rubbery side kneed pads to the tank greatly increases the grip and comfort for my knees (just like horseback riding). The side pads are "BMW" product sold at the local motorcycle store.
 

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Laying on the tank is definitely comfortable for a while, but my neck tends to get sore/tired after a little bit. I have noticed though, that it really cleans up the air and makes the ride rather enjoyable.

I've also noticed a change in airflow (though not a major difference) since I added my tank bag.
 

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Can you post a little more info on the BMW tank pads? They look pretty good.
 

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I don't, never seen much reason to, a few times I've tried it and didn't like the position at all and felt like I wouldn't be able to react properly if anything were to happen.
 

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Discussion Starter #5
Binary Jay said:
I don't, never seen much reason to, a few times I've tried it and didn't like the position at all and felt like I wouldn't be able to react properly if anything were to happen.
J,

I do sense a diminished ability for "reactivity". The downside being that once laid down, my body becomes committed to that posture. When upright, I can spontaneously shift my body rapidly in reaction to a surprise.

I use the laid-position primarily for highway straight-aways, and absent of significant traffic.
 

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Is the traffic in Vancouver any worse than Toronto's? :)
 

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Discussion Starter #7
J,

I moved from Toronto to Vancouver in 1990. Loved Toronto, as Vancouver.

Yup! Traffic is just as bad out here. I remember taking up to 2 hours to get out of the city on Friday afternoons (Vancouver is about 1 hour, cuz we aren't as big).
 

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Discussion Starter #8
Devious said:
Can you post a little more info on the BMW tank pads? They look pretty good.
The BMW pads is a package of two side knee pads and one center buckle pad. Unlike conventional tanks protectors which are thin plastic, the BMW product is made from very thick rubber, about 3 mm thick. The back side has self-adhesive.

When riding through the cold winter months, my knees no longer freeze while gripping the tank. The thick pads act as insulators. Yeah!

When shopping, I tried countless motorcycle dealers, and most had only the thin plastic center pads. You'll need to call around to find the BMW product. Good luck.
 

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Livin' on the Edge!
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It's hard to lay on the tank comfortably with the stock bars. With my lower and more forward bars, it is very comfortable. The answer for me is heck yeah, I do. Helps keep the front end down.
 

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If I want to crouch on the tank, I put my feet up on the back pegs. Its more comfortable on the legs. If you need to turn, I just shift body weight, I don't my knees into the turn.
I only use this if I gonna go real fast in a straightaway. On the fazer, if you don't tuck at high speeds, the wind becomes unbearable much above 120. But I've only done that a couple times.
 

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There's definitely a benefit to not weighting the bars. You can get that benefit while sitting upright, too. Use your knees to grip the tank, and support your upper body with your torso muscles. Those swanky tank pads should help with that, too. If you can accelerate and brake without adding much force to the handlebars, you'll end up riding much smoother.

Your engineering side might get a kick out of this... While riding along a boring stretch of flat freeway with my throttle lock on, I played around with body position to find out what the fastest position was. It wasn't actually tucked all the way down onto the tank. I tucked down just till I could feel the laminar part of the airflow heading over my helmet and down my back. Any further down, and the turbulence coming off the top of the screen and over my back must have added a bunch of drag.
 

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Discussion Starter #13
fraggle1 said:
There's definitely a benefit to not weighting the bars. You can get that benefit while sitting upright, too. Use your knees to grip the tank, and support your upper body with your torso muscles. Those swanky tank pads should help with that, too. If you can accelerate and brake without adding much force to the handlebars, you'll end up riding much smoother.

Your engineering side might get a kick out of this... While riding along a boring stretch of flat freeway with my throttle lock on, I played around with body position to find out what the fastest position was. It wasn't actually tucked all the way down onto the tank. I tucked down just till I could feel the laminar part of the airflow heading over my helmet and down my back. Any further down, and the turbulence coming off the top of the screen and over my back must have added a bunch of drag.
Yup! I got your kick.

I didn't consider gas mileage but I can image that it may be significant (guessing 10% at highway speeds). In the past I have done numerical modelling of aerodynamic drag on racing bicycles (I have a bicycle background - but new to motorcycles) and at speed for them, drag is everything!

Last week I stuck some telltales (ribbons) to the top edge of the windscreen. The obvious was found - the boundary layer is straight horizontal off the top lip (no up curl occurs). So your recommended body position for least drag matches my silly little experience.

:beer
 

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Discussion Starter #15
Mark_FZ6,

That is a hugh improvement. Good to hear.
 

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I like those mirrors a lot! I do crouch when there is a lot of high speed wind gusts in different directions. I find that by keeping my weight close to the tank, I have more control and can feel the direction of the gusts faster.
 

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skeleton said:
1) Secondary mirrors, permanently set for allignment for when I am laid over the tank. This gives me continuous view of any potential tailgaters. (I would never ride when I can't see behind me.)
Good idea, but believe me when I say that the few times that I get down on the tank, I KNOW there is NO possibility that I'm being tailgated! If they can hang back there, they deserve to be there. :lol
 

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Livin' on the Edge!
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Mark_FZ6 said:
I just figured less drag equal increased gas mileage so I tried it and I got 30 miles or so more out of a tank so I was impressed. Hey Fazr6 Which lsl handel bars do you have.
My first pair of LSL's were the street bar. Not the high street bar. They work well and just barely give full clearance when adjusted properly. I did have to cut about 1 1/2" or so off of each end...maybe more like two. I'm now trying the drag bar cut real short but had to make adjustable steering stops to keep them from hitting the fairing and tank. The reason I changed again was because I could go even shorter and I'm now about 1 1/2" lower than with the street bar.
 

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I always lay on the tank tucked as low as I can get when I know there isn't much traffic behind me. On straights and on the Interstate, of course. My mirrors are adjusted where I only have to raise my head slightly to check behind me. I actually found the best position for my mirrors while trying to adjust them for the tucked position. Good call on the bicycle handlebar mirrors, though. I might try to find one or 2 of those to add some rearward visibility. I usually vary from tucked to upright every few minutes as well, but I hate the windblast at 75-80+ when sitting upright.
 

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I also like laying on my tank bag. I didn't get to do that today though, because the bag was full of chocolate truffles. I found I was much more tired, and my back aches after this ride. Interesting to hear about the turbulence issue. I'm going to play with that. There's definitely a point at which the wind holds me up a bit without so much buffeting (even at 100mph, which I tried today for the first time).

I am concerned that my new GIVI will cause all sorts of problems with air flow.
 
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