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What goes up..........(37 posts)

What goes up..........John-d
Oct 31, 2001 7:08 AM

So, having got our bikes out from the garage, basement, attic, under the duvet.. we have now sat on our comfy saddles and spun our sub 12.00001 lb. bike to the top of the mountain, hill, hump back bridge, using our newly learnt perfect riding technique. What about the down side - eyeballs out or eyes wide shut?

There is a serious side to this as gains can turn to losses going down. What does the team think?
you don't get it backDog
Oct 31, 2001 7:38 AM
Going up, wind resistance is minimal.

Going down, wind resistance is extreme, and limiting. Plus, wind drag increases disproportionately with speed.

You never get it all back on the down hill. Even worse if you must brake for corners, something you don't do on the uphill.

Anyone thinks that heavier bikes are an advantage over all? Try riding a 50 pound bike up and down a hill, and then a 15 pound bike. Ought to be obvious which will be faster over all.

Light is better, assuming reliability and adequate stiffness is there.

If you don't believe me, run the numbers at

Yes you do. - I think!John-d
Oct 31, 2001 8:00 AM
That's an interesting site. I have just looked at the down hill sprint section. Heavier is faster.

My topic wasn't really to do with weight etc. I hade more in mind technique.

Fear factor

All that sort of thing.
Oct 31, 2001 8:14 AM
Yes, heavier is faster down a hill (or more correctly, higher mass to drag ratio); but it gets you more up the hill than you get back going down.

*Straights - tuck very low and narrow; stay in drops for handling, hands near center of top for aero

*Cornering - just like a race car, if you can - wide, hit apex, exit wide; brake before corner

*Line - see above

*Brakes - to descend fast, "don't brake lots"; brake only enough to stay on the road in the corners; never brake from mere fear (lots of people do); front brake does most of the slowing; watch lockup on rear

*Fear factor - what's that?

Great tips.Paula Pezzo
Oct 31, 2001 9:12 AM
What about countersteer?
Oct 31, 2001 9:16 AM
Too difficult a concept for most people. Let them discover it for themselves. :-)

Fear FactorTig
Oct 31, 2001 11:24 AM
Something that keeps you from being the best desender, but it also keeps you out of the ER and extends your visit on the planet a little! Too much Fear Factor can be worse than none at all. Driving behind a timid driver getting onto the freeway will remind us of that.

Funny how the Fear Factor grows with age and wisdom.
If you got it all backMel Erickson
Oct 31, 2001 9:05 AM
you'd have a perpetual motion machine. Compare it to a roller coaster. Eventually all good things must end.
No! No!Thinker
Oct 31, 2001 9:16 AM
Tell me there will always be beer...
There will always be beer, butMel Erickson
Oct 31, 2001 9:51 AM
there won't always be you!
Oct 31, 2001 10:00 AM
If I am 200 lbs, and drink about a quart of beer a day, then by the time I was 18 I was already mostly all beer, and since then, by your logic, I have been immortal:-) Result!
My god man...Mel Erickson
Oct 31, 2001 11:33 AM
You've discovered the fountain of youth!
Instructions I heard to build a good Perpeptual Motion Machine:Steeve
Nov 1, 2001 8:49 AM
I really heard this once at a dinner party!!!!

"First you start with a small battery...."

Unbelievable, but true!
The only perpetual motion machineDog
Nov 1, 2001 8:50 AM
the universe (as far as we know)
Even the universe will come to an end.Steeve
Nov 1, 2001 9:00 AM
In Thermodynamics 101 it's called "The heat death of the Universe" There is heat everywhere, but there are no areas hotter than anywhere else, eveything in the universe is at the same temperature, thus no work can be done.


What's the definition of "Absolute Zero"?

Answer: What most freshmen remember from Thermodynamics 101.
Stephen Hawking?Dog
Nov 1, 2001 9:12 AM
I thought I remembered something from Stephen Hawking about a cyclical universe. Seems plausible to me.

I want to read his book,Steeve
Nov 1, 2001 9:17 AM
I was just reading a commentary on his book this week (even though his book is probably about 10yrs old now). I really want to read it. Did you enjoy it? Was it any easy read?
Hawking is fascinatingDog
Nov 1, 2001 9:34 AM
I read the Brief History of Time and another book of his, but can't recall the title ; Hawking has a way of explaining extremely complex concepts in ways we amateur scientists can understand. Very fascinating stuff. Highly recommended

Only perpetual motion machine-a cat with jelly on its backvanzutas
Nov 1, 2001 12:12 PM
I have read that a Cat with a piece of bread with jelly on is back is a perpetual motion machine. Here is why.

When a cat falls it will always land on its feet.

When a piece of bread with jelly on it falls onto a white carpet it will always land jelly side down.

therfore by putting the two together the unit will continually hover above the carpet rotating.

Efficiency will be improved by haveing a more expensive carpet and or more jelly on the bread.
i won't remember this 'til 6 hours into my next long ride. nmJs Haiku Shop
Nov 1, 2001 1:18 PM
Space-Time Continuumbreck
Nov 1, 2001 11:00 AM
In Modern Physics space and time are linked; matter and energy are transmutable one to the other. Only math can describe these functions and layman's models have to suffice for the "best guess" as what this all means such as Einstein's famous falling elevator example as to how gravity may be perceived. Einstein never bought into Newton's relative mass; inverse-distance model of gravity and has proven to be correct. However for earth bound physics Newton got it right to so many decimal places it makes no fiff. Einstein's space-warp theory is so bogged down in high order math that it serves no useful to solve everday problems.

Back in 1963 Arlington State College, Texas, was taking my first Modern Physics course (Relativistic Physics and Quantum Mechanics intro) given by an old prof. from Bonn, Germany who spoke broken English. He stated, with a twinkle in his aged eye, that the problem understanding the diff between Newtonian Physics and Modern Physics was your mothers fault. That one early day when you were a toddler and driving away from the house, you said to your mom "Look, mommy, the house is moving away from us!" "No, no, no Johnny", she replied, "The house is stationary and we are moving away from it!"

Einstein in his General Theory of Relativity 1905, postulated that since there is no absolute "point of rest" in the universe, any physical object, hence the car, can be taken at a state of rest and all laws of the Universe still apply. So Johnny was right but needing to live on the fixed platform planet as opposed to the open sea with no reference points, it is much easier to survive if you take mom's viewpoint.

The most amazing thing may be that solid matter of any sort, as we know it, consists of only a hundred or so elements called atoms with close to 99.999...n% empty space contained with in them. The solar system model of the atom being most easily visualized has the nucleus consisting of postive charged Protons and neutral charged Neutrons bound closely together by the Nuclear Force, and the negatively charged Electrons in defined orbits revolving around much as the planets around our Sun and kept in check by the Electrical Force. In Earth geometry terms if the nucleus were the size of a pea, the nearest electron would be thirty five miles away. These atoms link together to form molecules such as water with the central oxygen atom and two attached di-polar hydrogen atoms 105 degrees apart.

The edge of space, who knows?
"Those who know are not learned"
"The learned do not know"
- from the Tao Te Ching of Lao Tsu
~6th century B.C.

Our wise men, be it Newton, Einstein, or Hawking ( a simple net search will reveal some of his "ramblings" :) give it their best shot. Time may or may not tell if they were right, as we (people) will need to be around to find out. Our nearset star, the Sun is scheduled to grow hotter as it ages and cook us all some day. Doubt if "we" make it that far though, at least in the form that we are in.

And "we are all in great form, heh!", to return to bicycling. And imagine we are never taking the "straight line" to get to our destination as we are taking the great arc to get 'round the planet :)

BTW, am a lightweight at this subject and will not be able to answer any questions. Perhaps on the board there are those thta could though, and especially if the enlightenment may apply to the bike :)

keep talkin', breck, i'm listening. you've said some of this...Js Haiku Shop
Nov 1, 2001 1:23 PM
in a way i hadn't considered before. and i read. alot.

Wow, all this from one comment about perpetual motion.Mel Erickson
Nov 1, 2001 2:52 PM
You never know what the baby will spit up.
speaking of babies spitting up... :-) nmDog
Nov 1, 2001 7:58 PM
Lost me with this one? nmMel Erickson
Nov 2, 2001 6:43 AM
The Knack and how to get it ... :)..breck
Oct 31, 2001 9:52 AM
Sum planetary laws are just like ol' Al's Special Theory of relativity back in ought 15 ; that is, the pathway down is much akin to his warped space theory of gravity as opposed to ol' Isaac's relative mass "theory" which we were taught in high school physics simply because we could not (as yet) work out tenth order differential equations. Some still don't get it :) Happily for us there is some low order physics technique to be learned down-the-hill warp speed mountain planetary pathway as opposed to the ho-hum get your asse kikk'd over the hill-and-dale by the stronger riders.

For fast down hill mountain tek-knee-Q, listen up and take notes; class is about to begin. Down Hill 101 today's subjects: 1)Aero position 2) cornering 3) counter-steering 4) braking 5) missile-lane-e-us & drafting :)

1)Aero position for the twisty-turny down-hill:
Pedals flat; knees hugging the top tube; elbows in to the sides; both hands against the stem; unload-the saddle and put your weight onto the pedals, hence loading up the bottom bracket, so as to lower your center of gravity and steady up the bike. Keep the back flat and low; chin up; Eyeballs as far out over the bar as you dare. Relax and do not look down nor think about front wheel flats if you are a pure roady; mtb'rs ignore this "possibility" :)

2) down-hill cornering:
Put the hands back onto the brakes, straighten the torso up a bit. One needs really good front brakes for slowing you at the last possible moment into the turn; rear brakes are moderators and don't lock these up(!). If you continue to lock up the rear, unscrew the caliper nutt a tad. Un-squeeze the brakes going into the turn; relax into the "U" section with outside-of-the-turn pedal straight down and fully loaded up with your weight; lean as much into the hill as you are comfortable with but keep the body in the same plane as the bike. Do not attempt to pedal in hard cornered high-crowned turns as the inside pedal may touch the pave and pogo the bike. To slow down not using-the-brakes simply hang the knee out on the inside of the turn and this excess drag will slow you. Pedal out of the turn in your "best" gear.

3) counter-steering:
Always counter steer the bike. Do not drive it like an ol' VDub bus, I.E. turn the "wheel" into and out of turns. Simply put some straight arm pressure on the bar in the direction in which you intend to steer the bike. The bike will follow. This is especially helpful when riding narrow shoulder margin back country roads with the dirt just inches away as the Bimmer Crowd's you and you are "threading the needle" between pave and dirt. Practice counter-steering if it is not in your bag-of-tricks or "possibles" as the old mountain men such as Jim Bridger would say.

4) braking:
Brake as little as possible, it only slows you down :) However if you must, front braking rules. Practice the art of front braking on more moderate down hill. Loosen up the rear brake one full turn in the steep mountains.

5) missile-lane-e-us & drafting:
Practice the missile-positions on moderate down hill and straight down hill first. Do not draft behind Dino if he has been draughting at the Cop Bar previous to the ride :) Anywho, be careful behind your buds on the down hill if they are the nervous type.

Pleese add to, correct, or detract from :) After i post i always see dumb errors :)
BTW, posted this sim-to thread as Wade Kelly or Big Ring an boards gone bye and got only the one response from Do(u)g as to fine-tuning, etc.

Shooting Star Ranch
San Diego Mountains ...yes, we do have sum :)
nice. thorough. thanks! nmJs Haiku Shop
Oct 31, 2001 11:50 AM
The Line to take into the turn ...addendum ..breck
Oct 31, 2001 12:59 PM
Dog covered this butt me should have commento on "theory and practice". It may be obvious from a pure geometry view point that the widest smoothest arc maintained thru the curve will obtain the max speed. However there are sum rulze may need to be broken in very tight blind curves as experienced on the mountain back country roads here and there.

Typically the steeper the road and the tighter the turn the more blind-spot-around-the-corner you will encounter so be very very careful here. Make it a habit to be "looking 'round" the fast up-coming corner for any hint of traffic that may overshoot the center line as you may also be tempted to do [and we all are]. On really blind curves for complete safety one may not want or prefer to take the "best" arc but one that will give you some safety margin to the right of the center line just in case you encounter some motor-head over the line at the last sec.

In general, start the up-coming turn against the right shoulder and shoot for a smooth arc to the center divide line of the center-of-the-curve apex and ending up on the right shoulder. Again, be forewarned that auto traffic coming up the hill will also be doing same and may (will) wander over the center-line, especially if the other car/truck/moto-cycle is a "local" and has the typical attitude that this is "their road" and they own it, as all we "locals" do. Motor tourist may be the worst though as they do not "know" the curves and driving them too fast for their/your safety and commonly overshoot the center divide.

Also check behind you when fast down hill cornering so no surprises will hamper your safety. Esp current moto-cycles which are extremely fast and can be on you in a sec as i have experienced more than a few times.

Sounds like excellent adviceDutchy
Oct 31, 2001 4:22 PM
I will try putting theory into practice on the weekend, I have some great 5km/3mile descents in my area,
that I know well, It just seems that downhill cornering is my weakness. I can turn left very good but am LOWSY
turning right, I can't figure out why.

My brother reckons I am at least 10kph/6mph slower in the corners than I should be.
Although as someone has
already said safety becomes more of an issue as you get older/wiser. He's younger and has no fear.

Thanks for the advice.

Excellent, just what I was looking for - thanks. One....John-d
Nov 1, 2001 1:08 AM
last question, The beer, to get the maximum benefit do you keep it on the bike until the bottom or drink it at the top before you decend?
Hate to mention this but...muncher
Nov 1, 2001 1:30 AM
Unless the maj or your weight is in your legs (which would make you odd, by general physiological standards) below the level of the saddle, then by standing slightly on the pedals (to weight them), you are actually raising your c of g, are you not?

I agree with your tip on this, but is the reason not just that you achieve a more stable platform controll wise because the bike can more easily sift around under you, under control?
Nov 1, 2001 4:00 AM
If you assume that the centre of gravity (CoG) of the bike is say somewhere in the middle of the diamond (e.g.) and you then place your weight fully supported on the saddle that could put the overall CoG at say belly button height. I know this is an over simplification but bear with me.

If you change this by applying your weight through your legs at the pedals or crank height that surely would have the effect of lowering the overall CoG.

Or to put it another way what about the 'track stand', they don't do it sitting down. They want their CoG as low as possible to stay upright easier.

How about a new slogan for the rear screen of the car - Track riders do it standing up?
Can't see it...muncher
Nov 1, 2001 4:40 AM
cos if your c of g is above your waist (as most folks is), then by standing you are raising it. Is your vew not confusing weight distribution on the frame with gravitational centre? Think about cornering. Your weight is pushing out from your c of g. The fact that you are standing on the pedals doesn't move YOUR c of G to the bb, it just bears the weight - the pendulm effect still eminated from the c of g of the whole bike and you mass - which will be higher if you raise yourself on the pedals?
Yes, your rightJohn-d
Nov 1, 2001 5:52 AM
you don't actually move the CoG but the standing action allows an offset force to the centre line, to be applied when viewed from the front. So as you said in the beginning one has a more stable platform.

Well I found it a useful exercise anyway thanks, sorry to be obtuse.
Welcome - found a solution anyway...muncher
Nov 1, 2001 6:01 AM
Have just lowered by c of g by consuming a large round of samdwiches while thinking that over. Best bit is that they will continue to lower my c of g untill some time tomorrow when..(enough - Ed).

:-) M.
CG visualization ...breck
Nov 1, 2001 7:11 AM
Hard to visualize i know. It may be simpler to say "load up the bottom bracket" for a more stable platform. Mountain Bikers use this method on rough fast down hill trails not only to reduce the butt pounding but to have more control of the bike. It does work.

One simply needs to try the methods to see if it works for them.

May as well insert the "wisdom and old age" conundrum here, as am getting the feeling of posting too much. Posting may well be like putting in the fence. That is the more posts one installs in a linear fashion to support the wire or mesh, the stronger we may believe our arguments to be and so hold back the madding crowd after our butt.

As we get older we may merely trade off perceived safety for less performance. We have a wife, kids, house, and a good job. Why lose it over sum stupid antic on the bike means nothing at the end of the day except you smoked old Bob whom typically gets the best of you. So us old guys typically get more crafty and sneaky to off set our ability to perform against the younger crowd. We even insist on age-group awards in the races, though i insist on weight-groups but nobody listens.

Nobody listens to us and that's why we are here espousing all this nonsense when we should be out riding or throwing the ball for the dogs to fetch. If she's a good mutt and strong we throw it out farther. Heck, we are not going after it. That is the crux of the problem. As we age we don't go after it as much anymore. We sit and type instead :)

cheers guyz and galz,
Sprung vs. unsprung weightStarliner
Nov 1, 2001 1:06 PM
I think what this is all about is not a matter of the center of gravity of two combined masses (the bike and the rider), but where the two masses interface with each other.

That interface point is lowered from seat level to BB level when lifting out of the saddle.

Whether or not it is an illusion or if science can explain it (I'm an artist, not a scientist), shifting the interface point down to the BB does make me feel more sure and stable on a screaming, twisty descent.

I suppose anybody would feel more stable and balanced with their body weight supported by their feet rather than by their butt.