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Would like advice on down hill speed and cornering fast.(26 posts)

Would like advice on down hill speed and cornering fast.gail
Sep 15, 2001 9:54 PM
re: Would like advice on down hill speed and cornering fast.harlett
Sep 15, 2001 10:04 PM
glad i stopped by. good to see you. thanks for the comments on that last thing. *S* give me a minute to write and I'll tell you what i know about speed..*G*
re: Would like advice on down hill speed and cornering fast.harlett
Sep 15, 2001 10:18 PM
your ultimate speed down a hill (assuming no pedaling) is determined by the balance between the component of your weight which is driving you down the slope, and the aerodynamic resistance which is holding you back. frictional forces are insignificant. therefore concentrate on reducing the aerodynamic drag. this means having the pedals fore and aft, feet pointing into the wind, knees in, hands on the drops to lower the upper body, elbows in. the head position is as low as possible.
taking corners fast is a skill requiring a great deal of practice. you need an exaggeratedly low center of gravity in the turn and your weight must tend towards the outside of the turn not the inside. your body has three points of contact with the bike: your backside, your hands and your feet. in the turn your feet are very important. for a lot of cornering force, lower the outside pedal fully, and shift some of your weight onto it. this will move your backside slightly to the outside of the turn, which is the correct direction. when necessary, use your legs as a suspension system. your bike will now ride out the bumps in the road, and your head will be steady, allowing you to maintain full control over the bike. the optimum position is to have the bike itself relatively over-banked into the turn, with your head turned so that you can see well ahead, right around the bend. if you've never done this before, it will be a bit of a revelation, perhaps for the first time you will begin to feel the push as your tires 'dig into' the road surface - analogous to the downhill skier's outside ski cutting into the snow and ice. you will not only be much faster, but you will also be safer too, as the bike will now take the precise line you demand of it. you must always leave a margin for error on the outside of the turn as you exit the bend, try to never use this last bit of roadway, except to recover from a serious misjudgement. another important advantage which comes from overbanking the bike, is that you can get into a turn much more quickly. the time when you will be pleased to have mastered this technique is when you round a mountain bend fast, and are suddenly and unexpectedly confronted with an opposite turn. you will rapidly be able to reverse the turn by rotating the bike under you. cutting off corners is another way to gain speed. it is all too easy to misjudge things and 'run out of road' though. the best advice I can suggest for starting to learn this is to not cut the corner until you can see the line out of it. so keep near to the outside until you can see the roadway out of the corner, then cut, that way you will avoid nasty surprises. there is one abiding principle which applies to every 'speed' sport, and this is that the faster you come out of a turn the faster you go down the next bit of straight. you will also need to learn the precise moment to begin pedaling out of a turn and be careful not to catch the inside pedal on the ground.
have FUN practicing this but remember think SAFE.oh and girls and speed are a natural combination!!!!!!*S*
re: Would like advice on down hill speed and cornering fast.gail
Sep 15, 2001 10:25 PM
Thanks. That's two things I owe you for now. Mind if I have your email addy?
re: Would like advice on down hill speed and cornering fast.harlett
Sep 15, 2001 10:32 PM
LOL after the other day i would have to be insane to give my email out on this site. *S* I'll get one at hotmail that we can use to exchange ours and then i can abandon it. next time i'll give that one to you. this girl needs some sleep for a ride tomorrow. nite!!!!
re: Would like advice on down hill speed and cornering fast.gail
Sep 15, 2001 10:35 PM
LAUGH. Thanks again. goodnight
duhduh
Sep 16, 2001 11:36 AM
like anyone here would want to email you your advise is bogus too isnt there a afgan bike discusion thing you could use not this one
Didn't Galileo solve this??jtolleson
Sep 16, 2001 2:31 PM
I buy into the discussion about technique, and especially the role of wind drag. I was surprised to see you describe downhill speed as a function of "weight" in your first sentence. Didn't Galileo disprove that (at least for free falling objects) several hundred years ago? What am I missing?
Didn't Galileo solve this??fuzzybunnies
Sep 16, 2001 2:39 PM
Galileo determined that two ojects in free fall will fall at the same rate. Going down a hill is different. Gravity works, and the heavier you are the better gravity works when other things come into play. TTFN
eat more donuts78velogirl
Sep 16, 2001 3:47 PM
I did this experiment once. I on my bike and Galileo in a 1956 buick. We each started coasting side by side down a long hill. He blew me a kiss just as he coasted out of my view.
The two riders of different weights are not free-fallingbill
Sep 16, 2001 6:39 PM
objects. Aerodynamic drag signifacantly impedes the movement of both. Even though the drag is about equal for the two riders, compared to the potential energy being expended as the riders go downhill (the potential energy being greater for the heavier rider), the drag is relatively greater for the lighter rider. I think. It's all high school physics; trouble is, high school was far too long ago.
Ahemgrzy
Sep 17, 2001 4:15 PM
Unless they're pedalling or braking then yes they are "free falling." That is their accelration is due to a component of gravity - it's just that it's not straight down. Without wind resistance (i.e. perfect vacuum) everything would fall at the same speed, and this is the rub. Problem is that the frontal/surface area of an object increases as a square functiopn while volume increase as a cube function. The bigger rider has *relatively* less drag for a given pound of mass. In reality the drag really isn't the same for the two riders - the smaller rider does have less drag, but it's still too much.

The potential energy to kinetic energy approach doesn't hold water b/c when you do the energy ballance the mass cancels out of both sides and you find that it doesn't matter. Take and object at rest and drop it and calculate the velocity (w/out drag) at the bottom. If you use an incline plane (i.e. hill) don't forget to multiplyby the sine of the angle. Zero slope and you're going nowhere.

Change in PE = Change in KE

mgh = 1/2mv^2

or cancel mass (m) from both sides and

gh =(v^2)/2

So, from an energy stand point all that matters is the height (and the slope). This is a little beyond high school physics and is really college level.
Trade Secretsgrzy
Sep 17, 2001 8:47 AM
You kinda went through the obvious from the physics stand point, which is good. However, there are additional techniques for setting up the attitude of the bike.

Probably some of the most important are to stay OFF the front brake once in the turn. It's OK to brake heavily with both brakes going into the turn and control the approach speed, but once in the turn the pressure on the front brake should be quite light while you can do some modulation on the rear. Front brake pressure increases the turning radius.

The other thing is to have the hands in the reach, not on the hoods. Your weight is higher and your reach is wrong.

Finally one of the more important aspects is to *straighten* the inside arm. This sounds totally counter intuitive, but it works. With both arms bent you really only have two solid contact points (saddle and pedals). Straightening the inside arm gives you the necessary solid third contact point and sets the bike on edge by allowing the rider weight to fall inside the truning radius of the bike and allowing the radius of the tire to initiate and maintain cornering in addition to turning the fork with respect to the frame. In motorcycles it's called counter steering and it's how you get a machine that weighs much more than the rider to corner quickly and hard. The other thing is to NOT have a death grip on the bars - you'll just induce a shimmy. Ultimately the design of the bike (frame geometry, wheels and tires), your weight distribution and fit determine the cornereing envelope of the bike.

Suffice to say most cornering limitations are due to the rider. There are many othere techniques such as squaring your shoulders, keeping you head level, but this should get you started and is very much overlooked when people are looking to be able to corner faster.
Trade Secretsharlett
Sep 17, 2001 11:53 AM
Good points!!! .like the instinctive feeling of wanting the center of gravity on the inside of the turn but the reality of it needing to be on the outside there are certain things about descending fast on a bike that are new learning experiences. I would advise the beginner to keep their arms slightly bent, hands forward in the drops with two fingers lightly on both brake levers until they came to a point of being relaxed doing progressively faster descents. much like finding the effectiveness of braking, when it helps-when it hinders, this is all about feeling in control and relaxed. knowing/learning what you and your bike can do is all part of retaining complete control
As to such things as squaring your shoulders, cutting corners off, using the banking of a hairpin to give you the maximum acceleration, shifting your weight fore and aft. these things and other points are details a person will acquire with thought and practice and listening to people like you talking about your experiences. ride fast...
huh??Bill in Palo Alto
Sep 17, 2001 12:37 PM
If your tires are at their limits in a corner, do not use any brakes. Your tires only have a given amount of grip, if your using 50% or your tires adhesion you can brake to use the other 50%. If your using 99% of your tires adhesion in a corner, well, you get the idea.

How does using the front brake decrease the turning radius??

Also, countersteering on a motorcycle is MUCH different than as you described.?
Well....grzy
Sep 17, 2001 1:07 PM
What you mention in the first paragraph is all well and good in theory. however, most people having trouble cornering faster aren't anywhere near the limits of tire adhesion - unless it's by accident. The pedal/seat/handle bar interconnect (i.e. rider) is the limiting factor. for enlightenment watch any crit race and see how hard the skilled racers corner their bikes using the exact same tires available to everyone.

Using the front brake *increases* the turning radius due to the weight transfer and added moment on the front of the bike. Many people go into corners riding both brakes and then go off to the outside. You can drag your rear brake a bit as you get more comfortable with higher cornering force (really "g"), but stay off the front brake - if you want a real world example in a safer environment try it on your MTB in the dirt. You'll soon see what I'm talking about. the front brake is super effective for slowing in a fairly straight line, and a bit can be used while cornering, but most people use way too much - especially when learning to corner faster.

Counter steering on a motorcycle is only really different by degrees. The machine/rider ratio is differernt, as is the ability to roll on power deep in the corner, you also have much higher adhesion with the bigger contact patch of the tires. However, the same principles and laws of physics apply. Chancers are if you can rail on a motorcycle you've got the bike thing under control. The key concept to counter steering is that you "push" the bars the opposite way to turn and allow the weight to "fall into" the turn. A stiff inner arm works towards this end.
uhhh... a few things.Bas Vanderwahl
Sep 17, 2001 2:38 PM
1. Application of the front brake could affect turning radius only if adhesion was lost. This is a higher level of skill than most riders have to be able to balance turning forces and brakes. LIke mentioned before if your tires are at cornering limits no brakes can be used unless slippage is desired. If not at cornering adhesion's limits, brakes, can be used, front or rear, doesnt matter which wheel. It is however, easier to recover from a loss of tract. on the rear than the front.

2. Of course your front wheel will slide out in dirt if you turn and also try to use the front brake. Same concept as on the road, just lower adhesion levels. In a straight line the tire is only handling braking. When turning, you have to split the adhesion between turning and braking.

3. Counter steering can ONLY be done if the rear wheel has a loss of traction. It is not possible otherwise. I dont think there are too many roadies that are getting rear wheel drift through corners.

4. In assessing the grip of a road bicycle, you also have to consider the substantial weight difference. I would bet that a road bicycle could corner right up there with a crotch rocket (with street legal tires) if not better. Now if you want to talk about 125 GP bikes with the sticky slicks thats another story.
uhhh... a few things.grzy
Sep 17, 2001 3:52 PM
Everyone is entitled to their opinions. You either missed my points completely or you haven't pushed the envolpe with respect to cornering. First one has to recognize that most riders aren't any where close to tire adhesion limits - it's more a question of ballance and dynamics. Why can a pack of riders go into a corner and all make it but one guy? It usually isn't the tires, but how they handle the bike.

1. Not true. You need to see it to believe it. Put the paper down go find a nice descending corner and make a few runs checking your speedo. Try using just the front brake, then just the back brake and then combos of the two. It should be pretty damn obvious that it does matter which wheel has the braking. A study of vehicle dynamics results in the same answer.

2. Master of the obvious. I used the dirt example to iluustrate the point. Again - go out and try it. You wanna rail single track on an MTB you minimize front brake application - that's not to say you don't use it. You start squeezing the front brake and you lose your line and speed - even if you don't go down.

3. You don't understand the definition of counter steering. Loss of traction is not required. If you want to turn left you steer to the right and begin to let your weight and the bike fall to the left, the arc of the wheel and the moving contact patch makes up for the slight steer to the right and the bike starts to turn left - quickly. It's a basic motorcycle skill and is usually taught on the first day of a 3 day course and then reinforced through quick manauvering drills.

4. Ain't no way a bike can pull as much "g" as a motorcycle b/c the contact patches and center of gravity are radically differen and the bike can power slide. A recumbent can out corner a "normal" road bike on a twisty descent all day. Again, you may need to see it to believe it.

I'm not trying to put you down, but I don't think you grasp what I'm saying. The original poster wanted to know how to corner better faster. All you did was say that it doesn't matter and offerred no tips or techniques that they could use. I don't think you'd be in the "fast cornering category" based on your responses.
uhhh... a few things.Bas Vanderwahl
Sep 17, 2001 4:13 PM
YOu suggested to the asker that he countersteer in the corner. I just wanted him/her to know that this isnt possible. Sure to initiate the lean, yes, but definitely not in the corner.

Your motorcycle stuff is blowing my mind. Vehicle dynamics?? Have a reference?

Your use of big words are slightly humorous.

I dont think you would like to mess with my skills. If you dont know me (I dont know you) you should keep those kind of comments to yourself. You could be talking to the reigning 500cc GP champ for all you know.
Slam Dunkgrzy
Sep 17, 2001 4:39 PM
Counter steering isn't just used to initiate a turn you also use it to maintain the corner since the bike is actualy leaned further into the corner than having the bike and rider all in a straight line at a given angle. I guess it comes down to the definition of counter steering - what's yours? You made several statements that certain things weren't possible based on what you think - I disagreed and tried to provide my basis. Here's a couple references for you since you asked.

Colin Chapman wrote several classic texts centered around suspension design and cornering - all very interesting reading. There is also a book called The Fundamentals Vehicle Dynamics which was our text many years ago. Amazon has it: (http://www.amazon.com/exec/obidos/search-handle-form/002-2585583-5318405)

Fundamentals of Vehicle Dynamics (R114)
by Thomas D. Gillespie (Hardcover - March 1992)
Average Customer Review:
Usually ships in 1-2 weeks

Our Price: $69.00

Which big words are you having trouble with - should I talk slower and use itty bitty words for you? I guarantee that the texts use larger words. There's this thing called a "dictionary" - you'd find it hillarious.

I ain't messing with your skills (I'm assuming you have some), but it's obvious you're no champion on wheels. Master of the obvious, sure. Do you even ride a motorcycle? If you did you wouldn't think that a bicycle could out corner any current crotch-rocket and none of this would blow your mind. Sure I'm amaking some assumptions, but the odds are I'm right on most of the uncertain stuff and dead right on the analytics.

And yeah, I'm being a little sarcastic and over bearing - your defensive ignorance requires it. Chock it up to the Mnky going ape.
Cat fight.NCP
Sep 17, 2001 8:34 PM
First off, nice thread.

I know this greasy character is a self proclaimed defender of truth.

Grzy, what is your definition of countersteer? You seem to be mixed up with the meaning.

Road bikes dont have suspension, I guess the front suspension compressing under front brake dive would affect steering, but only to quicken things up.

What does vehicle dynamics (assuming its talking about 4 wheeled vehicles) have to do with a bicycle?

Mister math, why dont you take the weight of a road bike and rider(200lbs), the weight of a motorcycle and rider (600lbs) and divide by the tire contact patches of both a road bike (roughly 1 inch) and a crotch rocket (roughly 3 inches)? Please give us the results.

Lastly its chalk, not chock.

Try to be mature in your replies.
Assumptionsgrzy
Sep 18, 2001 8:46 AM
Bikes are vehicles, therefore vehicle dynamics. There are significant difference between two, three and four wheeled vihicles, powered and unpowered, but the laws of physics still apply to all and the differences are accounted for. The Theory of Ground Vehicles is also a good reference. Had you looked at either one you wouldn't be asking that question.

Counter steering - when the front wheel alone is not turned enough to produce the resulting turning radius. This implies that the difference is made up by tilting the bike further into the turn and a shift of rider weight. By not turning the wheel enough in the direction of intended turn you have achieved counter steer. Now it's your turn.

Who said anything about front suspension? That said even a rigid fork bike has some suspension due to the compliance of the tire and the flex of the fork, but the travel is limited and has a higher spring constant.

First I'd counter that the contact patch of a crotch rocket is greater than three inches. Ultimately what matters is the ability to pull "g" and is usually tested on a skid pad. Contact patch alone doesn't determine cornering ability, it's but one factor.

I'm an engineer not a poet, please forgive me. It's kinda funny when people fall back on symantics and spelling to counter a technical discussion. Very telling.
re: adviceStarliner
Sep 16, 2001 8:23 PM
Before you start out, make sure your tires are inflated to the recommended pressure - don't want them to be underinflated or else your tail might wig-wag on a high speed turn.

Going downhill, keep your hands down in the drops, elbows and knees in, pedal cranks horizontal (one foot forward, the other rearward), butt slid back hanging over rear wheel, with the tip of your tongue able to taste your stem.
Goal is minimal drag without sacrificing stability/safety (no positioning hands together on stem away from your brake levers).

For fast turns, choose a line and stick with it through the turn. Try not to brake in the middle of the turn - do any necessary braking before you plunge into it. Try not to make steering corrections in the middle of the turn. Goals are to take it smoothly and as fast as possible avoiding the "try nots" previously mentioned. It will help if you learn to plan ahead of yourself rather than reacting to what is at hand.
re: adviceharlett
Sep 16, 2001 9:50 PM
your physical safety depends to a very large extent on your bike working correctly. the problem you would have on the flats that is an inconvenience can lead to serious injury on fast downhill descents. checking that both brakes are working well and are correctly aligned, brake pads in good shape, tires properly inflated and in good condition with no nicks are all things that need to be done. all of these things help you stay in control of your bike. one of the most important parts of fast descending is to be fully under control. one factor that also plays into safety and control is being free of any factors which may affect judgement: alcohol, prescription or even over the counter drugs and also your emotional state. ride smart and safe then ride fast
Dunno 'Bout Thatgrzy
Sep 17, 2001 1:26 PM
We sometimes hit a winery or two to do a little tasting before a screaming descent. It helps take the edge off and steady the nerves ;-)

Seriously - it's sound advice to be clean and sober. Probably belongs in the "do as say, not as I do " file.

Having the bike in proper working order and tuned up goes without saying. A set of beaten wheels makes it hard to corner fast, even if they're true and round, due to differences in spoke tension.

Three kinds of riders: those that have fallen; those that will fall; and those that will fall again. Think about it.
Thank yougail
Sep 17, 2001 4:38 PM
Thank you Harlett, grzy and Starliner for helping me begin understanding and doing this.. Good info from all of you. And "duh" your an idiot!!!!!