#51
|
|||
|
|||
Braking Technique
In article , Mark McMaster
wrote: warren wrote: In article , Mark McMaster wrote: warren wrote: In article , Mark McMaster wrote: warren wrote: Sure Mark. Why aren't the pros following your advice? You'll have to ask them. I already know why. If you brake hard enough so that your front wheel has 90+% of your bodyweight on it (according to you and your sources) you will have a very difficult time trying to steeer/make subtle corrections. That is nearly always much worse than a slight skid of the rear tire and a good You seem to misunderstand the weight shift. Weight is shifted to the front wheel regardless of which brake you use. I know that, but I'm not interested in shifting as much weight to the front as you advise because it will have a worse affect on steering than the way I do it. But then I'm just doing what I see good pros doing all the time. However, in your case, your steering was greatly reduced by your insistence on over-braking the rear wheel and skidding. If you had slowed at the same deceleration rate but with more reliance on the front brake (and less on the rear), your rear tire would not have skidded, and your steering control would have been better. Given the situation I was in, and given that a very good pro descender like Beloki did the same thing, I'm fine with what I did. A skidding tire has less traction than a non-skidding (rolling) tire. At the very least, when you first sensed the rear wheel skidding, you should have let off a bit on the rear brake lever, See, you have a poor understanding of what goes on in that brief moment when I'm trying to avoid running in to the heads of two guys sliding in front of me who were the two riders right in front me (no time to prepare), while I slow down as quick as I possibly could under the circumstances. Neither of us even know exactly how much front brake I was using but I was still able to steer around something important. to stop the skidding and increase whatever tire traction was available - you would have stopped faster. If you are such a good bike handler, why did you allow the rear tire to keep skidding? Later you say it probably took me 40+ feet to slow down yet my rear rire lost only about 25% of its tread. I don't think I was skidding very long. So, if you choose to get half of your braking from the rear wheel, and I instead allow the front wheel to take 90% of my weight, I will stop in a distance at least 20% shorter than you will. But you will have much less reliable/nimble steering around whatever it is you're trying to avoid. What happens if I have 90% of my weight on my front wheel and I hit a slick spot on the pavement or a bump or a bike or body? I think it's usually better to have less than 90% if there's a chance of hitting something. If won't allow the front wheel to supply the majority of your braking, you simply can not maximize braking. Again, braking is not the only important concern. Although she has made her biggest mark in downhill racing, Marla Streb races in a very wide variety of events (road & off-road, bicycles & motorcycles). If you think she doesn't know how to handle a bike on pavement, you are very wrong. And again, you seem to be claiming that expert braking is only applicable to road racing. Nope, just that the braking on the road is often very different from braking off road and the opinion of a MTB racer is not particularly valuable when the obvious experience and technique of good road pros is contrary to her method (according to you). You seem to think that professional criterium racers know the best braking technique. I didn't say that. I think it can be critically important at times (contrary to what you said earlier) but I think maximum braking while trying to avoid something is common for a road racer too. "In steep straight descent on a mountain bike, put your weight far off the back of the saddle and clamp on the front brake. Your rear brake is used, but you will skid if you brake hard. The front brake is best for optimal control and stopping power on very steep descents like those found on the Slickrock Trail in Moab, Utah." The speed used there is a fraction of what happens in my case and the example provided by Beloki and the gradient is much different too. The skill should be performed differently. I use my front brake more when I'm on my MTB. Your use of MTB braking examples are another indication that you lack an understanding of the important factors for the road, and for his racing Phinney always had to use those mushy Dura-Ace brakes that had poor modulation. You said: and I'm truly convinced that I'm a good bike racer, so I must be an expert bike handler, too. I'm a better bike-handler than racer. Says who? No evidence of that has yet been presented. I know it. I was merely refuting your incorrect assumption about my opinion that one fact lead to the other. Therefore, despite my lack of understanding of the underlying physics, people should believe me when I explain how to brake, Yes. So now you are the self-declared expert. My, you truly are impressed with yourself. Not THE expert and lots of guys are better at it than me but the majority of them also use both brakes for road events for the reasons I've said, and the fact that I crash less often than the average of my fellow racers, and am able to pass alot of people who are demonstrating less accurate braking skills than me does indicate my skill level is good. And unlike you, I'm not advocating something contrary to the examples you can see every night on OLN. Next time I'll just jam on my front brake harder and I'll stop 20% sooner but I won't be able to avoid hitting the first guy's head because some dope on the internet told me to put 90% of my weight on my arms and I couldn't steer as well. "Sorry about the skull fracture but look, my rear tire is still good!" -WG |
Ads |
#52
|
|||
|
|||
Braking Technique
warren wrote:
In article , Mark McMaster wrote: warren wrote: In article , Mark McMaster wrote: warren wrote: In article , Mark McMaster wrote: warren wrote: Sure Mark. Why aren't the pros following your advice? You'll have to ask them. I already know why. If you brake hard enough so that your front wheel has 90+% of your bodyweight on it (according to you and your sources) you will have a very difficult time trying to steeer/make subtle corrections. That is nearly always much worse than a slight skid of the rear tire and a good You seem to misunderstand the weight shift. Weight is shifted to the front wheel regardless of which brake you use. I know that, but I'm not interested in shifting as much weight to the front as you advise because it will have a worse affect on steering than the way I do it. But then I'm just doing what I see good pros doing all the time. However, in your case, your steering was greatly reduced by your insistence on over-braking the rear wheel and skidding. If you had slowed at the same deceleration rate but with more reliance on the front brake (and less on the rear), your rear tire would not have skidded, and your steering control would have been better. Given the situation I was in, and given that a very good pro descender like Beloki did the same thing, I'm fine with what I did. A skidding tire has less traction than a non-skidding (rolling) tire. At the very least, when you first sensed the rear wheel skidding, you should have let off a bit on the rear brake lever, See, you have a poor understanding of what goes on in that brief moment when I'm trying to avoid running in to the heads of two guys sliding in front of me who were the two riders right in front me (no time to prepare), while I slow down as quick as I possibly could under the circumstances. Neither of us even know exactly how much front brake I was using but I was still able to steer around something important. to stop the skidding and increase whatever tire traction was available - you would have stopped faster. If you are such a good bike handler, why did you allow the rear tire to keep skidding? Later you say it probably took me 40+ feet to slow down yet my rear rire lost only about 25% of its tread. I don't think I was skidding very long. So, if you choose to get half of your braking from the rear wheel, and I instead allow the front wheel to take 90% of my weight, I will stop in a distance at least 20% shorter than you will. But you will have much less reliable/nimble steering around whatever it is you're trying to avoid. What happens if I have 90% of my weight on my front wheel and I hit a slick spot on the pavement or a bump or a bike or body? I think it's usually better to have less than 90% if there's a chance of hitting something. If won't allow the front wheel to supply the majority of your braking, you simply can not maximize braking. Again, braking is not the only important concern. Although she has made her biggest mark in downhill racing, Marla Streb races in a very wide variety of events (road & off-road, bicycles & motorcycles). If you think she doesn't know how to handle a bike on pavement, you are very wrong. And again, you seem to be claiming that expert braking is only applicable to road racing. Nope, just that the braking on the road is often very different from braking off road and the opinion of a MTB racer is not particularly valuable when the obvious experience and technique of good road pros is contrary to her method (according to you). You seem to think that professional criterium racers know the best braking technique. I didn't say that. I think it can be critically important at times (contrary to what you said earlier) but I think maximum braking while trying to avoid something is common for a road racer too. "In steep straight descent on a mountain bike, put your weight far off the back of the saddle and clamp on the front brake. Your rear brake is used, but you will skid if you brake hard. The front brake is best for optimal control and stopping power on very steep descents like those found on the Slickrock Trail in Moab, Utah." The speed used there is a fraction of what happens in my case and the example provided by Beloki and the gradient is much different too. The skill should be performed differently. I use my front brake more when I'm on my MTB. Your use of MTB braking examples are another indication that you lack an understanding of the important factors for the road, and for his racing Phinney always had to use those mushy Dura-Ace brakes that had poor modulation. You said: and I'm truly convinced that I'm a good bike racer, so I must be an expert bike handler, too. I'm a better bike-handler than racer. Says who? No evidence of that has yet been presented. I know it. I was merely refuting your incorrect assumption about my opinion that one fact lead to the other. Therefore, despite my lack of understanding of the underlying physics, people should believe me when I explain how to brake, Yes. So now you are the self-declared expert. My, you truly are impressed with yourself. Not THE expert and lots of guys are better at it than me but the majority of them also use both brakes for road events for the reasons I've said, and the fact that I crash less often than the average of my fellow racers, and am able to pass alot of people who are demonstrating less accurate braking skills than me does indicate my skill level is good. And unlike you, I'm not advocating something contrary to the examples you can see every night on OLN. Next time I'll just jam on my front brake harder and I'll stop 20% sooner but I won't be able to avoid hitting the first guy's head because some dope on the internet told me to put 90% of my weight on my arms and I couldn't steer as well. "Sorry about the skull fracture but look, my rear tire is still good!" -WG The theoretical computations are accurate. But I have to wonder if there isn't a lack of reliable scientific data on its practical application. I think we know you can't go 100% front. But feelings won't quantify 50%, 75% or 90% to the extent that anyone can reach a practical analysis where the rubber meets the road. |
#53
|
|||
|
|||
Braking Technique
warren wrote:
In article , Mark McMaster wrote: warren wrote: In article , Mark McMaster wrote: You seem to misunderstand the weight shift. Weight is shifted to the front wheel regardless of which brake you use. I know that, but I'm not interested in shifting as much weight to the front as you advise because it will have a worse affect on steering than the way I do it. What affect on steering do you expect from the weight shift? I think you'll find that weight distribution has less effect on the ability to steer than you imagine. For example, the old high wheeler bicycles steered just find with most of their weight on the front wheel. Watch a BMX freestyle rider stand on the front axle pegs - they still steer just fine, too. (Here's an extreme example of steering with a fully loaded front wheel: http://www.craigjones.com/record-stoppie.html) So, if you choose to get half of your braking from the rear wheel, and I instead allow the front wheel to take 90% of my weight, I will stop in a distance at least 20% shorter than you will. But you will have much less reliable/nimble steering around whatever it is you're trying to avoid. Again, I suggest you actually try steering with the majority of weight on the front wheel before you leap to such conclusions. You'll find it is more nimble than you imagine. For example, if you've ever sprinted out of the saddle, standing directly over the pedals with your chest over the handlebars, you've probably put about 75% of your weight on the front wheel. And yet racers do this all the time in tight pack sprints, which also require nimble steering. In the more stable position of being on the saddle (or at least with your legs clamping it) and your arms in a more braced position, you can easily remain nimble with 80 or 90% of your weight on the front wheel. What happens if I have 90% of my weight on my front wheel and I hit a slick spot on the pavement or a bump or a bike or body? I think it's usually better to have less than 90% if there's a chance of hitting something. That's odd that you worry about such things, when you race a lot of criteriums. What if you leaned way over in hard corner and you bump into someone or hit a slick patch? A rider with experience and good technique will know how far they can push their traction, and how to react to the unexpected. If you so timid about slick pavement or hitting someone, why do you race criteriums? Although she has made her biggest mark in downhill racing, Marla Streb races in a very wide variety of events (road & off-road, bicycles & motorcycles). If you think she doesn't know how to handle a bike on pavement, you are very wrong. And again, you seem to be claiming that expert braking is only applicable to road racing. Nope, just that the braking on the road is often very different from braking off road and the opinion of a MTB racer is not particularly valuable when the obvious experience and technique of good road pros is contrary to her method (according to you). You seem to boo-hoo a lot of good advice from many sources. Perhaps you open your eyes a little more, you might actually learn something. And yes, offroad braking does have pertinence to road braking - especially in light of the possibility of "slick spots" you seem to be so worried about. There may be variations in technique, but the same basic principles apply - the laws of physics don't suddenly change when you move from one surface to another. I'm a better bike-handler than racer. Says who? No evidence of that has yet been presented. I know it. Well, that certainly proves it - not. Your willful ignorance of several bike handling related subjects seems to belie that. So now you are the self-declared expert. My, you truly are impressed with yourself. Not THE expert and lots of guys are better at it than me but the majority of them also use both brakes for road events for the reasons I've said, and the fact that I crash less often than the average of my fellow racers, and am able to pass alot of people who are demonstrating less accurate braking skills than me does indicate my skill level is good. And unlike you, I'm not advocating something contrary to the examples you can see every night on OLN. Next time I'll just jam on my front brake harder and I'll stop 20% sooner but I won't be able to avoid hitting the first guy's head because some dope on the internet told me to put 90% of my weight on my arms and I couldn't steer as well. "Sorry about the skull fracture but look, my rear tire is still good!" So, if I understand correctly, what the issue boils down to in your mind is not wanting to shift too much weight onto the front wheel because it makes steering difficult. I don't know why you believe that. A bicycle turns by counter steering and leaning, and front/rear weight distribution does little to change that. Road bikes have no suspension, so their steering geometry does not change with weight shift. It takes little torque to turn the front wheel (even at speed), and any additional weight shifted onto the front wheel has no significant affect on that. After all, a unicycle is highly nimble, even though it puts 100% of its weight on its front wheel. Racing motorcycles don't seem to have any problem steering, even when they are braking so hard they are practically doing a nose-wheelie. I think you also overestimate the traction demands of braking. If you were to apply both brakes equally until the rear tire skidded, you'd be at decelerating at a rate of about 0.3g - i.e. your tires would have a traction force of about 30% of the rider/bicycle weight. If you cornered and leaned over enough to hit a pedal on the ground (about a 35 deg. Lean angle), you'd have a lateral force of about 0.6g, which requires about twice as much traction force as you could need with equal front and rear braking. And yet racers seem to have no problem cornering at the angles and lateral forces where they can't pedal for fear of hitting a pedal on the ground. On good pavement, a bike can be cornered at up to about 1 g (45 degree lean angle). Even when you consider that the tires are nearly equally weighted when cornering, that means each tire in a corner can support a traction force equal to half the weight of the rider/bicycle. Braking, on the other hand, is limited by the pitch over point, and the pitch over point is at about 0.5g, which is within the traction that is demanded for cornering. But there is a key difference, and that is that under hard braking, the forward weight shift increases the traction of the front tire, making it even less likely to skid than in hard cornering. Since we have to brake at less than the pitch over point, hard braking with primarily the front brake puts less traction demands on the tires than hard cornering. And since you are such a good bike handler, I'm sure you have no problem with cornering traction, so you shouldn't have problems with braking traction. Since we're on the issue of traction and skidding: These are always an issue during all types of riding over any surface. Surface conditions, speed and terrain contours all affect traction available for cornering or braking, and a cyclists must be aware of these at all times, and adjust their actions accordingly. However, it seems that your solution to these problems is to simply avoid hard braking (and its reliance on the front brake) at all times, even when it is warranted. It seems your fear of the front brake is preventing you from using it to its full effectiveness when conditions allow. A better approach would be to learn appropriate technique for hard braking situations, and therefore the proper use of the front brake, and practice it, so that you would have those tools at your disposal when those situation when it is advantageous. Sure, excessive front braking may cause problems in some situations; but there are many, if not more, situations where problems can be avoided with judicious use of hard front braking. When that car pulls suddenly pulls out in front of you, pulling hard on the front brake and loading up the front wheel may be preferable to the alternative. On a weekly ride I do, there is a steep (about 10% grade), somewhat curvy, half mile descent, which ends at an intersection with a busy road (Waltham St., intersecting with Lexington St., in Woburn, MA). Just coasting, it is easy to exceed 40 mph on this hill. I regularly let it fly to about 40-42 mph, and then brake hard in the last 150 feet around the last curve before the intersection. Trying to use equal front and rear braking would result in rear wheel skidding (and loss of direction control), so I use mostly front wheel braking. I have yet to skid the front wheel or go over the handlebars. By the way, while there are few bicycle riding instruction courses, there are many motorcycle riding courses. I think you will agree there are similar concerns for motorcycle braking (skidding, pitch over). None the less, Most of these course attempt to teach riders to let go of their fear of the front brake. See: http://www.motorcycle.com/mo/mcnews/safe3.html http://www.geocities.com/armingk/drivingskills_1_1.htm http://homepage.ntlworld.com/ian.max...Advanced_ridin g/Braking/braking.html http://www.nhtsa.dot.gov/people/inju.../00-NHT-212-mo torcycle/motorcycle45-46.html http://www.webbikeworld.com/Motorcyc...aking-tips.htm http://www.motorcyclesafety.org/page...s_braking.html Mark McMaster |
#54
|
|||
|
|||
Braking Technique
warren wrote:
Tonight during my warmup I did some testing. While going down a 4-6% grade at about 12mph I applied about 50% (of what I could have applied with full squeezing force) to the front brake only and I slowed down rapidly but my rear wheel came off the ground about 1-2 inches. And then you pitched over and broke your spine and now you are posting from hospital using a straw in your mouth? No? What a miracle! Every expert knows that as soon as the rear wheel leaves the ground the rider will spontaneously combust, unless of course the rear brake is on full. For the next 3 attempts I applied about 50-60% force front brake only on a flat section starting at about 21mph and I slowed down rapidly but I had to exert ALOT of pressure on the bars to keep from getting pitched forward. It felt like something close to doing a push-up. It's okay. Having raced 700+ criteriums at cat 3 and better you have a strong upper body. During the second two of these tests I tried to steer or move the bars a bit but it was almost impossible to do anything useful with that much pressure on the bars. Do some more pushups. Then I tried 2 tests with rear brake only at about 60-70% and it took longer to slow down but it was pretty easy to continue steering. So basically you just conceded that the original argument, which you opposed, is correct. Q.E.D. Good game and thanks for playing. See you next Christmas. Then I tried two tests on the flat and a very slight down grade with front and rear brakes, each at about 50%. I slowed down pretty fast, was able to steer a little, and in one test my rear wheel did some very brief (a few inches maybe), intermittent skids. You were able to steer "a little"? Surely that level of control is not nearly nimble enough to avoid the cyclist lying in the road ahead, on fire (because while he was crashing he used the front brake only which made him combust spontaneously)? I tried two tests on a slight upgrade of about 2-5% with a bit more braking about 60% pressure on each brake and I slowed down quickly but there was more pressure on my arms/bars and steering was a little less possible. You might need to replace your headset if it makes it impossible to steer while you are braking. Now, more than before I'm convinced not to apply more than about 50% pressure to my front brake and use 50-60% pressure on the rear brake if I may need to steer around something while braking hard. If I'm not worried about steering I think that something around 60% on the front and up to a light/brief skid on the rear is optimal. The likely cost of too much front brake is far worse than the likely cost of too much rear braking. Except on 70 degree off-road descents on loose gravel, where traction is sufficient for braking by sticking a branch in between the spokes of your front wheel. An 8 year old kid knows how to control a rear wheel skid as long as they're still able to steer with their front wheel They haven't raced in any criteriums so they are irrelevant. (I will now proceed to unceremoniously delete the rest of your paragraph without reading any useful information it may contain. (Though I'm tempted to point out that a controlled crash isn't really a relevant form of safe braking.)) As for your comment about sprinting out of the saddle with 75% weight on arms/front wheel... As you may know I do ALOT of sprint training. Of course! Any professional criterium racer worth his weight in gold does. That movement/body position (with slightly bent elbows and arms about 80 degrees to the top tube) is not trying to resist being pitched forward (you'd better have your arms almost straight for that and at a shallower angle than 80 degrees) and it's much easier (compared to hard front braking) to keep your arms relatively relaxed during sprints. So your headset is fine but your motor skills are suffering. .... |
#55
|
|||
|
|||
Braking Technique
warren wrote:
Tonight during my warmup I did some testing. While going down a 4-6% grade at about 12mph I applied about 50% (of what I could have applied with full squeezing force) to the front brake only and I slowed down rapidly but my rear wheel came off the ground about 1-2 inches. For the next 3 attempts I applied about 50-60% force front brake only on a flat section starting at about 21mph and I slowed down rapidly but I had to exert ALOT of pressure on the bars to keep from getting pitched forward. It felt like something close to doing a push-up. During the second two of these tests I tried to steer or move the bars a bit but it was almost impossible to do anything useful with that much pressure on the bars. Then I tried 2 tests with rear brake only at about 60-70% and it took longer to slow down but it was pretty easy to continue steering. Then I tried two tests on the flat and a very slight down grade with front and rear brakes, each at about 50%. I slowed down pretty fast, was able to steer a little, and in one test my rear wheel did some very brief (a few inches maybe), intermittent skids. I tried two tests on a slight upgrade of about 2-5% with a bit more braking about 60% pressure on each brake and I slowed down quickly but there was more pressure on my arms/bars and steering was a little less possible. Now, more than before I'm convinced not to apply more than about 50% pressure to my front brake and use 50-60% pressure on the rear brake if I may need to steer around something while braking hard. If I'm not worried about steering I think that something around 60% on the front and up to a light/brief skid on the rear is optimal. The likely cost of too much front brake is far worse than the likely cost of too much rear braking. First a few of comments: As you saw, the front brake is capable of higher braking rates than the rear. I'm sure you also recognize that the weight shift (requiring more arm force to oppose) was due to the deceleration rate, and not to which brake was actually doing the braking. Although the rear wheel skidded momentarily a few times using the rear brakes, even at the much higher deceleration rates with the front brake, the front wheel didn't skid. When braking hard and loading up the front wheel, it didn't actually take more steering torque to turn the front wheel to steer. Instead it is a matter of muscle control, to coordinate the small steering forces with the larger forces needed to oppose the forward shift. Just like a lot of other riding skills, this is a skill that can be mastered with practice, and steering will become more nimble and fluid. Just as a quick illustration, imagine that you had foot pegs mounted to the rear dropouts (like on a BMX freestyle bike), and that you stood on these wheel holding onto your handlebar drops. In this position, it would be very literally like doing pushups on the handlebar. The overall front/rear wheel weight distribution would be about the same as when riding normally, but you'd have far more of your weight on your arms. As you can imagine, with that much weight on you arms, it would initially be a bit more difficult to coordinate your steering motions (even when not braking). However, with practice, you could learn to be quite nimble and maneuverable. Still and all, it is good to develop the reflexes to be able to maneuver while applying hard braking. It will add an additional tool that can be utilized when the conditions require it. Of course, I'm not recommending that you slam on the brakes and load up the front wheel every time you brake. Obviously it would not be recommend when riding in deep sand, or over washboard ruts. But in those situations where it can be done and you really need it, it's nice to be able to pull hard braking techniques out of your bag of bike handling tools. Mark McMaster |
#56
|
|||
|
|||
Braking Technique
In article , Mark McMaster
wrote: First a few of comments: As you saw, the front brake is capable of higher braking rates than the rear. I'm sure you also recognize that the weight shift (requiring more arm force to oppose) was due to the deceleration rate, and not to which brake was actually doing the braking. Although the rear wheel skidded momentarily a few times using the rear brakes, even at the much higher deceleration rates with the front brake, the front wheel didn't skid. I think part of Beloki's problem may be that his front wheel hit that loose or slick patch of pavement or granular stuff on top of the pavement with a "highly-loaded" front wheel, and the front wheel slipped a little. He had alot of braking on both wheels but I think his steering problems are what kept him from being able to skid his rear wheel to a controlled stop. When braking hard and loading up the front wheel, it didn't actually take more steering torque to turn the front wheel to steer. Instead it is a matter of muscle control, to coordinate the small steering forces with the larger forces needed to oppose the forward shift. Just like a lot of other riding skills, this is a skill that can be mastered with practice, and steering will become more nimble and fluid. I sincerely doubt that. When your arms are trying to oppose the weight shift the (arm) tension has to be very high to do that. Steering (with arms. wrist, hands, hips) takes muscles that are as relaxed as possible and that's along way from the situation where your arms have to provide resistance to say, 70-90% of your bodyweight, especially if those correction have to happen very fast and accurately. Remember, in my case the two guys directly in front of me created an obstacle and that is not very much time or distance to make a correction. I don't think the freestyle bike analogy works because the speeds (its influence on steering corrections) and the dynamics of the weight shift are so different. I also don't think the analogy of normal road turns and stopping down a steep hill are quite the same because not only do you have alot longer to decide what you want to do, you have alot longer to initiate the turn, and supple hands and arms are not as important for that type of turning while braking hard. -WG |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
"Actually you are the first person to bring up this issue" | James Annan | Mountain Biking | 428 | April 4th 04 08:59 PM |
Training Technique? | Roy Zipris | General | 4 | February 3rd 04 01:49 PM |
First road bike: braking? | Alan Hoyle | General | 47 | September 28th 03 11:40 PM |
Thoughts on braking | John Appleby | General | 76 | August 11th 03 10:30 AM |