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  1. #1
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    high speed

    In another forum, Mark (Tandem Geek) wrote,

    "If terms like apex, countersteering, trail braking, off-camber, brake modulation, rim heating, and escape route planning aren't things you think about while descending then you may or may not be prudent to explore high speed descents."


    The topics of rim heating and escape route planning are probably common knowledge to people on this forum.
    I think when your refer to apex, you are talking about cornering properly.
    I assume that by brake modulation you mean that you brake gently at first and gradually increase pressure, not jamming the brakes on.
    When descending fast, what are you thinking about pertaining to countersteering, trail braking, and off-camber?
    Future speed mongers need to know . . .

  2. #2
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    Quote Originally Posted by cedo
    Future speed mongers need to know . . .
    Apex: Setting up for corners in such a way that you eliminate as much hard cornering as possible. What you are striving for is the ability to follow a continuous and smooth riding line that requires no braking once you enter the turn or any abrubt steering inputs. To do this requires either familiarity with the roads on which you ride or the ability to see past the apex, which is to say that you can see enough of the road ahead to know where the actual apex is. The execution is pretty straight forward: You set up for the start of your turn well to the outside of the visible corner as is safely possible, then move through the mid-point (apex) as close to the inside edge of the road as is safely possible, and exit as far to the outside of the corner as is safely possible. Essess on descents offer perhaps the most exhilarating test of your smoothness in setting up and executing a series of turns that require a complete shift of weight and balance from one side of the bike or tandem to another as you transition from the right to left hand turns in succession.

    Brake modulation: Brake modulation = the ability to exercise precise control over your brakes. Some bicycle brakes and in some cases frame characteristics allow you to do this better than others. Since bicycles allow you to independently control your front & rear brakes, this allows brake modulation to be far more dynamic than in your car in that, not only can you modulate your brakes as a system, you can bias your brake modulation from front to back to achieve different results or to handle different situations. In regard to rim heating -- something that tandem teams must respect if they are going to descend steep grades at any speed – on challenging descents, this independent brake bias allows for alternating the use of front & rear brakes. Rather than having both brakes applied continuously -- which will subject both rims to constant heating -- braking with the front only for a short period of time and then shifting to the rear for a short period of time will allow each rim to cool-off a little bit in the airflow which can reduce the maximum temperature that a rim would likely see if constant braking was used on the same descent. Also, as mentioned under the heading of apexing, smoothness is the key to controlled speed. Precise brake modulation allows a rider to "feather" their brakes to make minor speed adjustments or, as mentioned, to incrementally increase braking pressure without upsetting the balance or steering with abrupt inputs, either of which will reduce control and speed, sometimes in ways that are unpredictable. Therefore, as you begin to push your performance closer to critical speeds and in demanding conditions, the need to have highly predicable braking performance and knowing how to use it becomes increasingly important, i.e., braking before the start of your turns not after initiating (applying brakes tends to make bikes want to go in a straight line), understanding that brake energy is transmitted to the road by the same tire that is trying to hold your steering line (a tire can handle only so much friction before it gives), etc.

    Countersteering: This is how bicycles steer at high speeds (period). If you don’t have a full appreciation for what’s going on under you as you "lean into turns" and how "leaning" controls how your bike steers you could find yourself in a world of hurt if you enter a turn too fast or too low and need to tighten up your turning arc to avoid running into other riders, out of your lane, off the road, or worst of all into oncoming traffic. When you are traveling at a high rate of speed on a two-wheeled cycle you turn by countersteering, that is to say you turn the front wheel left to go right and right to go left. However, it’s done instinctively and most cyclists only recognize the act of countersteering as "leaning the bike into a turn". At high speeds, to tighten up the arc of your turn you MUST lean the bike deeper into the corner and to straighten the bike up or change its direction you must stand the bike up (by turning into the lean – yes, it’s true), and then "lean" the bike in the opposite direction. If done passively or by instinct, you can manage most fast descents with some semi-challenging turns. However, as you get into the very high speeds with high speed corners countersteering needs to be actively managed to maintain control of the bike. For example, if you find yourself in a blind corner that you assumed was a 90 degree turn that would end just out of view but, instead, found that it was a 180 degree with a decreasing radius, you would have to lean your bike far deeper into to the turn to stay within your lane or on the road. To do anything else, i.e., apply brakes or "steer" into the turn would either cause your bike to stand-up and go straight or perhaps slide out from under you. In either case, you would most likely leave the relatively safety of your traffic lane. It's also important to fully appreciate that countersteering and cornering at speed also demand some attention as to how you place your weight over the bike and consciously forcing yourself to "torque" the bike into the turn by putting pressure (shifting weight) onto your outside pedal, putting pressure against the outside of your saddle with your thigh, and also "torquing" the handlebars to press the bike into the turn. To be fair, shifting weight to the outside pedal is actually a misnomer in that what you really want to do is to keep your weight centered over the bike. There is a tendency for cyclists to move their body weight into the turn, ala a motorcyclist hanging off of his 300-600 lb motorcycle dragging a knee, which serves no purpose on a 18-40lb bicycle or tandem. By telling yourself to weight your outside pedal, etc.. all you are really doing is centering your weight.

    Trail braking: Trail braking is an advanced braking technique that is more commonly heard discussed by folks who race sports cars or who are advanced motorcyclists; essentially braking all the way into the corner as a way of loading up the front wheel and helping to bring the rear wheel around faster to get around the corner a bit faster. However, cyclists and tandem teams can find themselves unintentionally trail-braking which can increase your turning radius and cause you to unintentionally head towards the outside edge of the road or lead to a rear tire wash-out: both are bad things.

    Off-camber: As in "off-camber turns" is something that can unnerve a rider who encounters one for the first time or unexpectedly at a high rate of speed. Quite simply, an off-camber turn is one with negative banking. Therefore, unless you adjust your lean angle to compensate for the steepened "virtual" angle of your bike vs. the road surface and recognize that traction is also reduced in an off-camber turn, things can get skittish.

    Taken in aggregate, these things all underscore the important of the aforementioned "escape route planning" that needs to go on in the back of your mind as you ride. Hopefully, your bike handling skills will allow you to "steer around" trouble and/or stop in time to avoid a crash. However, since that’s not always the case you’ll want to make a habit of looking ahead for hazards and escape routes by playing the "what if" game, e.g., what if that car doesn’t see me and pulls out into the road? Is he turning right (pass him on the left) or left (dive to the right)? Worst case, where do I go if I need to get off the road: in some cases, the right shoulder of the road may offer run-off space or a soft landing. However, that’s not always the case; so, do you have time to cross the on-coming lane of traffic to reach a safe landing zone on the opposite side of the road? Or, is this one of those situations where you just need to lay-it down and slide to a stop as the lesser of two evils is a monster case of road rash vs. something potentially far worse, e.g., a steep drop-off or guard rail. It’s sad but true, several square inches of your body will slow your speed down much faster than any kind of bicycle brake/tire combination and, the more of your body that’s in contact with the ground, the faster you’ll come to a stop (ouch).
    Last edited by TandemGeek; 05-09-09 at 02:04 PM.

  3. #3
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    Countersteering: This is how bicycles steer at high speeds (period). If you don’t have a full appreciation for what’s going on under you as you “lean into turns” and how “leaning” controls how your bike steers you could find yourself in a world of hurt if you enter a turn too fast or too low and need to tighten up your turning arc to avoid running into other riders, out of your lane, off the road, or worst of all into oncoming traffic. When you are traveling at a high rate of speed on a two-wheeled cycle you turn by countersteering, that is to say you turn the front wheel left to go right and right to go left. However, it’s done instinctively and most cyclists only recognize the act of countersteering as “leaning the bike into a turn”. At high speeds, to tighten up the arc of your turn you MUST lean the bike deeper into the corner and to straighten the bike up or change its direction you must stand the bike up (by turning into the lean – yes, it’s true), and then “lean” the bike in the opposite direction. If done passively or by instinct, you can manage most fast descents with some semi-challenging turns. However, as you get into the very high speeds with high speed corners countersteering needs to be actively managed to maintain control of the bike. For example, if you find yourself in a blind corner that you assumed was a 90 degree turn that would end just out of view but, instead, found that it was a 180 degree with a decreasing radius, you would have to lean your bike far deeper into to the turn to stay within your lane or on the road. To do anything else, i.e., apply brakes or “steer” into the turn would either cause your bike to stand-up and go straight or perhaps slide out from under you. In either case, you would most likely leave the relatively safety of your traffic lane.
    If you don't believe this (welcome to the crowd) you can prove it to yourself by putting your left hand on the right handlebar and letting go with your right hand. You'll crash or figure it out. (learned that trying to warm up my throttle hand behind the cylinder head of my motorcycle while cruising down the highway... figured it out).

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