理论帮：前刹后刹？左手右手？

晟龙蓉

发现一个有趣的现象。前刹应该装在哪一边？我从小喜欢骑单车玩，大部分单车过去都是右手前刹，这几年接触锻炼或者说见到竞技目的单车，不论山地党公路帮很多人前刹改在左手。下文为翻译观点，另外附原文。（文章内容充实，我仅翻译讨论刹车部分的部分）。
1，正确的高效刹车为单独使用前刹车！除非湿滑弹跳等等情况，只要前刹车，急减速时候后轮承担导向左右，需要保持抓地力，不使用后刹车是保持抓地力的办法，独立前刹保证后轮仍然能够抓地。
2，前滚翻发生的概率极低，而且更多的是因为手臂支撑不足导致。
3，多数汽车靠左行驶的国家地区，前刹车在右手。反之亦然。
4，前刹如此的重要！不论我们是否能够认可和掌握单独前刹车技术。那么多数人又是右手习惯，是不是应该由更有力更灵活的右手来控制前刹车？原作者表示即使他自己在美国的时候仍然装配了右手前刹。
下为原文！
更加细致的解释了独立前刹车的意义。
Braking and Turning Your BicycleTranslations of this article:GermanRussianbySheldon "Front Brake" Brownrevisions bvJohn "One Good Turn..." AllenBike Culture LetterFront or Rear?Leaning in TurnsOver the Bars?Panic StopsUsing the Front BrakeUsing the Rear BrakeWhich Brake Which Side?Braking--Front, Rear or Both?Since your bike has two brakes, one for each hand, if you want to stop as safely as possible, you need to pay attention to how you use each of them.Conventional WisdomConventional wisdom says to use both brakes at the same time. Thisis probably good advice for beginners, who have not yet learned to use their brakes skillfully, but if you don't graduate past this stage, you will never be able to stop as short safely as a cyclist who has learned to use the front brake by itself.Maximum Deceleration--Emergency StopsThe fastest that you can stop any bike of normal wheelbase is to apply the front brake so hard that the rear wheel is just about to lift off the ground. In this situation, therear wheel cannot contribute to stopping power, since it has no traction.Won't I Go Over The Bars?The rear brake is O.K. for situations where traction is poor, orfor when your front tire blows, but for stopping on dry pavement, the front brake alone provides the maximum stopping power, both in theory and in practice.If you take the time to learn to use the front brake correctly, you will be a safer cyclist.Many cyclists shy away from usingthe front brake, due to fear of flying over the handlebars. This does happen, but mainly to people who have not learned to modulate the front brake.The cyclist who relies on the rear brake for general stopping can get by until an emergency arises, and, in a panic, he or she grabs the unfamiliar front brake as well as the rear, for extra stopping power. This can cause the classic "over the bars" crash.Jobst Brandt has a quite plausible theory that the typical "over-the-bars" crash is caused, not so much by braking too hard, but by braking hard without using the rider's arms to brace against the deceleration: The bike stops, the rider keeps going until the rider's thighs bump into the handlebars, and the bike, which is no longer supporting the weight of the rider, flips.This cannot happen when you are using only the rear brake, becauseas soon as the rear wheel starts tolift, the rear wheel skids, limiting itsbraking force. Unfortunately, though, it takes twice as long to stop with the rear brake alone as with the front brake alone, so reliance on the rear brake is unsafe for cyclists who ever go fast. It is important to use your arms to brace yourself securely during hard braking, to prevent this. Indeed, good technique involves moving back on your saddle as far as you can comfortably go, to keep the center of gravity as far back as possible. This applies whether you are usingthe front, rear or both brakes. Using both brakes together can cause "fishtailing." If the rear wheelskids while braking force is also being applied to the front, the rear of the bike will tend to swing past the front, since the front is applying a greater decelerating force than the rear. Once the rear tire starts to skid, it can move sideways as easily as forward.If you don't believe me, perhapsJohn Forestercan convince you...see hisEntry in the rec.bicycles FAQ on Front Brake Usage(Subject: 9.17). (Unfortunately, the maintainer of that site has a habit of breaking links, so you may need to go tothe rec.bicycles FAQ indexto find the article.) Or readJohn Allen's advice.Skidding the rear wheel also wearsthe rear tire very quickly. A single rear-brake-only stop from 50 km/h (30 mph) with a locked rear wheel can wear the tread of a road tire right down to the fabric!Learning to Use The Front BrakeMaximum braking occurs when thefront brake is applied so hard that the rear wheel is just about to lift off. At that point, the slightest amount of rear brake will cause the rear wheel to skid.If you ride a conventional bike, the best way to master the use of yourfront brake is to practice in a parking lot or other safe space, applying both brakes at once, but putting most of the effort into the front brake. Keep pedaling as you brake, so that your legs will tell youimmediately when the rear wheel starts to skid. Squeeze, don't grab,the brake levers, so you can sensewhen this happens. Practice harder and harder stops, so that you will learn the feel of stopping fast, on the edge of rear-wheel liftoff.Text the brakes in this way whenever you are about to ride an unfamiliar bike. Some brakes are more sensitive than others, and you need to know the "feel" of the brakes.Once you are comfortable with thefront brake, also practice releasingthe brakes to recover control, until this is an automatic, reflex action. At a very low speed, apply the brakes hard enough that the rear wheel skids, or just begins to lift. When it does, immediately release the brakes. Wear your helmet.Some cyclists like to ride a fixed-gear bicycle, that is, a bicycle that does not permit coasting. When you brake hard with the front brakeon a fixed gear, the drivetrain gives you excellent feedback aboutthe traction at the rear wheel. (Thisis one of the reasons that fixed gears are favored for winter riding.)If you ride a fixed gear with only a front brake, your legs will tell you exactly when you are at the maximum brake capacity of the front brake. Once your fixed gear has taught you this, you will be able to stop any bicycle better, using the front brake alone.If you find the fixed-gear concept intriguing, I have a majorarticle on Fixed Gears for Road Useon this site, and also a page ofFixed-Gear Testimonialsfrom happy converts.When to Use The Rear BrakeSkilled cyclists use thefront brakealone probably 95% of the time, but there are instances when the rear brake is preferred: *.Slippery surfaces. On good, dry pavement, unless leaning in a turn,it is impossible to skid the front wheel by braking. On slippery surfaces, however, it is possible. Afront wheel skid almost always leads to a fall, so if there is a high risk of skidding, you're better off controlling your speed with the rearbrake. *.Bumpy surfaces. On rough surfaces, your wheels may actuallybounce up into the air. If there is a chance of this, don't use the front brake. If you ride into a bump whileapplying the front brake, the bicycle will have a harder time mounting the bump. If you apply the front brake while the wheel is airborne, it will stop, and coming down on a stopped front wheel is aVery Bad Thing. *.Front flat. If you have tire blowout or a sudden flat on the front wheel, you should use the rear brake alone to bring yourself to a safe stop. Braking a wheel that has a deflated tire can cause the tire to come off the rim, and is likely to cause a crash. *.Broken cable...or other failure ofthe front brake.When to Use Both Brakes TogetherGenerally I advise against using both brakes at the same time. There are exceptions, however: *.If the front brake is not sufficiently powerful to lift the rear wheel, the rear brake can help, butthe best thing to do is to repair the front brake.Typical rim brakes lose a great deal of their effectiveness when the rims are wet, so using them both together can reduce stopping distances. *.If the front brake grabs or chatters so you can not modulate it smoothly, you must only use it lightly. Again, repair is in order. *.On long, straight mountain descents, your front brake hand may get tired, or you may be at risk of overheating a tire and blowing it out, so it is best to spread the work between both brakes. Pumping the brakes, alternating between one and the other, will briefly heat the surface of each rim more and dissipate more heat before it spreads inwards to the tires. When sharp deceleration is needed, the front brake is more effective, as usual. *.When leaning in a turn, traction is shared between braking and turning. Using both brakes together reduces the likelihood thatone wheel or the other will skid anddump you. The steeper you lean, the less you can brake, so moderate your speedbeforea curve. When you are leaning deeply, you need to release the brakes entirely. *.Long or low bicycles, such as tandems and long-wheelbaserecumbents, have their front braking limited by the possibility of skidding the front wheel, since their geometry prevents lifting the rear wheel. Such bikes can stop shortest when both brakes are applied.Tandem caution:when riding a tandem solo (nostokeron board) the rear brake becomes virtually useless due to lack of traction. Therisk of fishtailing is particularly highif a solo tandem rider uses both brakes at once. This also applies to a lesser extent if the stoker is a small child.Which Brake Which Side?There is considerable disagreement as to which brake should be connected to which lever: *.Some cyclists say it is best to have the stronger right hand (presuming a right-handed cyclist) operate the rear brake. *.Motorcycles always have the right hand control the front brake, so cyclists who are also motorcyclists often prefer this setup. A moment of confusion in an emergency situation can be deadly. The left lever on a motorcycle operates the clutch, which will not stop you!There are also observable nationaltrends: *.In countries where vehicles driveon the right, it is common to set the brakes up so that the front brake is operated by the left lever. *.In countries where vehicles driveon the left, it is common to set the brakes up so that the front brake isoperated by the right lever. (The European Union has, however, adopted this as a standard, even though most European countires drive on the right.)The theory that seems most probable to me is that the national standards arose from a concern that the cyclist be able to make hand signals, and still be able to reach the primary brake. This logical idea is, unfortunately, accompanied by the incorrect premise that the rear brake is the primary brake.For this reason, I set my own bikesup so that the right hand controls the front brake, which is not the norm in the U.S.I also do this because I'm right-handed, and wish to have my more skillful hand operate the more critical brake.On the other hand, if you have already developed a preference, you usually do best to stick with it -- or at least, choose a few weeks of riding under undemanding conditions to retrain your reflexes. In an emergency, you must act faster than you can think.If you switch between a Mac and a Windows PC, where the same keys make different characters, or between a clarinet and a saxophone where they make different musical notes, you know how reflexes can trip you up.If youare used to skidding the rear wheelwith the rear brake, switching the brake cables can result a flight over the handlebars. If you mostly use the front brake, switching the cables can result in rear-wheel skidding and increased stopping distance.These problems are most likely when first riding an unfamiliar bike, so, again, always test the brakes with a light brake application when you first start out.See also myletter to Bike Culture magazine.Leaning in TurnsTo turn a bicycle, you must lean inward toward the direction of the turn. The faster you are going, andthe sharper the turn, the more youmust lean. You have no choice about this, for a given speed and turn radius, the center of gravity ofthe bike/ridermustbe moved sideways a particular amount or the bicycle will not balance.What you do have control over is whether you lean the bicycle more than, less than, or the same amount that you lean your body, toget the overall center of gravity to the place that it has to go. *.Leaning the bicycle sharply whilekeeping your upper body more uprightThis approach is popular with beginners who are scared to lean over sideways, and who feel less disoriented by keeping their bodiesmore upright. -- though actually, they don't. The cyclist is much heavier than the bicycle, which leans over farther, instead.Captaining a tandem with a stoker who doesn't know about leaning in turns can be a very unsettling experience, because you must lean farther to compensate.Keeping the upper body more upright is recommended by some racers and coaches as offering thepossibility of recovering from a skid, butI don't believe it.[I think there might be something to this. If you start to skid out, you might be able to yank the bicycle up and momentarily press the wheels harder into the road surface to gain more traction -- though the side force also might potato-chip a wheel, or roll atubularoff the rim.Racers also sometimes drop the knee that is to the inside of the turn. Yanking the knee inward mayalso help ro recover from a skid.Also see Jobst Brandt's comments, below -- John Allen.] *.Leaning the upper body sharply while keeping the bicycle more uprightThis approach is popular with riders who are afraid of striking a pedal on the road. This is a particular concern for riders offixed-gearbicycles, since they cannot coast through corners.This technique is also recommended by some racers andcoaches as offering the possibility of recovering from a skid, butI don't believe it.[Neither do I --but, as Sheldon says, this may benecessary to avoid a pedal strikewith a fixed-gear bicycle -- John Allen.] *.Leaning the upper body and the bicycle together, keeping them in line as when riding straight.This technique has the advantage of keeping the steering axis, tire contact patches and center of gravity all in the same plane. This preserves the proper handling characteristics of the bicycle, and makes a skid less likely. You can verify this yourself by performing an experiment suggested byJobst Brandt:"Some riders believe that sticking out their knee or leaning their bodyaway from the bike, improves cornering. Sticking out a knee is the same thing that riders without cleats do when they stick out a foot in dirt track motorcycle fashion. It is a useless but reassuring gesture that, on unevenroads, actually works against you. Any body weight that is not centered over the bicycle (leaning the bike or sticking out a knee) puts a side load on the bicycle, and side loads cause steering motions if the road is not smooth. Getting weight off the saddle is also made more difficult by such maneuvers."To verify this, ride down a straightbut rough road standing on one pedal with the bike slanted, and note how the bike follows an erratic line. In contrast, if you ride centered on the bike you can ride no-hands perfectly straight over rough road. When you lean off the bike you cannot ride a smooth line over road irregularities, especially in curves. For best control, stay centered over your bike."A letter to Bike Culture:The following is a letter I wrote to Bike Culture magazine in 1995, addressing some of the points covered above:In Bike Culture #6, Marek Utkin decries "Stupid Standards" in the bicycle industry. He begins with a wonderful exercise in guilt by association "Throughout history, despots have tried to regulate every aspect of their society..." He goes on to link Hitler to the D.I.N. and Stalin to G.O.S.T. standards. Unaccountably, he forgets to mention the strong linkage between Napoleon and the Metric system--perhaps he likes metrics, and doesn't want to bring up its despotic antecedents.He is specifically exercised by new E.U. regulations that specify that the front brake should be controlled by the right hand. "The trouble begins when a bike with right lever to front brake is ridden...in any country where traffic keeps to the right. The left hand signal, across traffic, is muchmore hazardous than the right hand signal. With the right hand...front brake the potential danger increases. Stopping the front wheel only, with one hand on the handlebars, can cause front-wheel instability. Also the upper part of the cyclist's body moves forward as the bicycle abruptly decelerates, causing further pressure on the right side of the handlebars."I have to attribute his attitude to a common misunderstanding about brakes. With bicycles, as with virtually all wheeled vehicles, the front brake is the more important and effective brake. The front brake by itself will stop a standard bicycle twice as fast as a rear brake by itself. The front brake by itself will stop a standard bicycle asfast as both brakes used together, except on very slippery surfaces.Unfortunately, many casual cyclists and non-cyclists have the mistaken idea that using the front brake is dangerous, and that you are likely to lock up the front wheel, pitch over the handlebars and crack you skull. This type of accident is extremely rare, and unlikely on a bicycle that is in goodrepair, ridden by a cyclist who has learned to use the front brake sensitively.The danger is more real for bicycles with damaged rims, or mis-adjusted brakes. The danger is even greater for the cyclist who habitually relies on the rear brake alone when suddenly faced with the need for a panic stop. A panicky rider who is unused to the front brake may indeed grab it full-force as a last resort, and may take a header.If you will forgive an automotive analogy in these green pages, a driver who has never driven a car with power brakes is likely to skid afew times the first time he or she tries driving a car that has them. This does not mean that there is something wrong with power brakes, however, it means that thedriver needs to learn how to use them.I frequently ride a fixed-gear bike with a front brake only. This is an excellent way to learn subtle control of the front brake, as the fixed gear gives very good feedback of the traction available at the rear wheel.In the early '80s, I became infatuated with mountain bike riding in the woods, and completelyre-adapted my braking style to cope with the loose surfaces common on woods trails.In 1988, I moved to France for a year, and got back into road riding.Near my house was a wonderful bit of road down the side of a valley, called La Route des Sept Tournants. It is a series of sweeping switch backs, beautifully paved, very well engineered. I used to descend it regularly on oneof my favorite loops. The problem was, I could never really go fast down it, I always felt that I was on the verge of losing traction with myrear wheel and spinning out. After a few months of this, I was beginning to conclude that I had just become a coward as I reachedmiddle age. I remembered I used to go faster around similar bends on my old fixed gear with no rear brake----wait a minute, maybe that's it! The next time I went that way, I decided not to use my rear brake unless I felt I really needed it--I would just go slowly at first, only as fast as I felt comfortable with using the front brake alone.Mirable dictu, I found that I was my old self again! It had indeed been the rear wheel that was on the verge of slipping, and only because I was using its brake. Without the drag of the rear brake,the rear wheel was in no danger ofslipping. The front wheel, thanks tothe weight shift caused by the braking I still had to use, had plenty of traction as well.Many people will tell you that it is dangerous to use your front brake in a turn; I would respond that this is so if your turning/banking technique is incorrect. The center of gravity of a bicycle/rider must lean into a turn; this is required by the laws of physics. There are three ways you can do this. One way is to keep the bike more-or-less upright, but to lean your upperbody into the turn. Another is to keep your body more-or-less upright, and lean the bicycle under you. The third, and usually correct technique is to keep your body in line with the bicycle frame, lean thebicycle and rider together as a unit.Leaning the bicycle and rider differently messes up the handling of the bike, by moving the center of gravity sideways from the plane of the wheels. If you apply the front brake while doing this, the braking force exerts a steering force through the now off-center headset. Jobst Brandt has an excellent way of proving this to yourself: try riding down a straight,but bumpy stretch of road while leaning the bike to one side and your body to the other. If you are brave, try applying the front brake very gently.I must admit to a bit of ambivalence as to whether a government body should tell people how to set up their bicycles.In the U.S.A., de-facto governmentregulation has made left-front all but compulsory for new bikes to besold. I strongly object to this. I once had a near-accident as a result: I was riding an unfamiliar bike that was set up left-front, even though I am used to right-front. I came to an intersection, a car cut me off, I instinctively grabbed with my right hand. Since this was the rear brake, I was only barely able to stop in time!I will add one further reason for preferring the right-front setup: Most people are right handed. I think we can all agree that the front brake requires more skill thanthe rear; therefore, it should be assigned to the more skillful hand.
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