Saturday 24 March 2012
Photo Blog.
While the rest of the world is apparently readying themselves for the annual test of fitness and finesse (ha ha!) that is the Sherwood round of the NPS, Rachel and I are spending, for the first time in a long time, a relaxing weekend getting used to our bums being on our saddles for 4+hrs. So for all you XC losers at Sherwood, here's what today held...
Wednesday 21 March 2012
Size matters
So we have a new technological debate in the world of bike racing, this time sparked by a third wheel size being thrown into the ring after Nino Schurter's excellent win at the Pietermaritzburg World Cup race last weekend. There has been fierce debate on wheel sizes for racing and riding alike since Gary Fisher first started pioneering alternative sizes in the 2000s, and if anything the debate appears to be intensifying rather than settling down.
So let's be clear about a few things. Firstly, let's dispense with the impression that "big wheels" are new - they are not. The engineering argument behind the now franky ridiculous-looking "Ordinary" (what most of us think of when we hear the term "penny farthing") was that the larger wheel would provide a smoother ride for the user on the rough and cobbled roads. So big wheels have been used on rough surfaces since the 1860s.
The historical curiousity that resulted in so many modern-era bicycles having 559mm ISO wheels (what we think of as 26") was that the pioneering band who met on Marin Mountain in California in the late 1970s to ride bicycles down offroad dirt trails did so on old Schwinn clunker bikes from the 1930s. These had wide frame clearances to accommodate their larger "ballooner" tyres, and very laid-back frame angles that allowed extra stability when careening downhill on a foolishly unsuitable bike. The tracks that these guys rode down the mountain bore very little resemblance to what we would consider an mtb trail today - they are wide, open double-track with gentle turns and rough terrain. This is what we would consider perfect 29er territory today, where there is little need for acceleration and deceleration, and the larger wheels would smooth out the lumps and bumps a bit, but the opportunity to build a "better" bike was lost in simply having fun!
Cometh the hour, cometh the bike - as the sport became more and more technical, and moved away from the three hour epic hillclimbs and fast descents that were so common during the 90s (see for example http://www.youtube.com/watch?v=QTdMEZkZyTI ), and became more about a shorter 1h45m sprint over much harder, more technically demanding courses (i'm thinking more of this: http://www.youtube.com/watch?v=E1HteyJiOcs ) these 26" wheels suddenly came into their own; they are lighter and have a lower moment of inertia, and so require less force to accelerate compared to their larger-diameter cousins, perfect for twisty, tight fast-slow racing. But of course, no XC race can contain *just* technical features, and so of course there will always be fast sections where a larger wheel would win out.
The point I am trying (and possibly failing) to make, is that in terms of perceived benefits, changing wheel size is always going to be a compromise. If you can imagine the same rider is capable of winning a world cup race, where the differences are smallest between athletes, on any size of bike, it suggest the optimisation curve is very shallow indeed. As a former design engineer, i know what i would have been encouraged to do in this situation. I would have been encouraged to look for quick wins, but not waste time trying to infinitely refine because it makes little difference and costs a lot of time and money. So there are two explanations for the fact that the bike industry has pursued this apparent hiding to nowhere - either because they are led by their representative athletes (like Scott with their 650b prototype for Schurter), and are prepared to sink potentially millions of Euros to help them get the "marginal gains" to win. Or, the more cynical view would be that the industry has isolated a new way of encouraging us to buy a second bike, especially if we are easily-led racers, and with that realisation they are prepared to make an investment.
I am aware that i have been jaded by my experiences of working in industry to some degree, but it seems highly unlikely that manufacturers would expect to see a return of ~1M Euros from having their riders win world cups, it would perhaps improve their selling power a bit, but actually the top-end race models comprise a tiny component of overall sales. And most people don't buy new race bikes all the time. So it makes sense to believe that they think this is a great way to sell us a second race bike - if we all do it, and they're ahead of the curve, that's a lot of revenue!
I am prepared to believe that there are small gains to be made by particular bikes on particular courses, but i would imagine that they pale into insignificance ccompared to the effect of the riders themselves. I don't imagine that if Absalon had been on a 29er at the Dalby World Cup last year he'd have roasted Kulhavy, or even that he'd have finished in a different place in the final results. I can see the sense in bigger wheels for bigger people, but ultimately you should ride what you're comfortable with and what allows you to have a good position. For me, that's a 26er - i'm too short to get the position i like on a 29er, and the way i like to descend wouldn't suit a 9er anyway. The "its always faster" fanboys have missed a crucial point in their testing - the psychological placebo effect, that if you think something will be faster, you will sub-consciously ride to make it so. That doesn't work for me, as a physicist and engineer, i know it's not faster, it's just a compromise which puts a different emphasis on straight line and cornering speed, so i may as well stick with what i like!
So let's be clear about a few things. Firstly, let's dispense with the impression that "big wheels" are new - they are not. The engineering argument behind the now franky ridiculous-looking "Ordinary" (what most of us think of when we hear the term "penny farthing") was that the larger wheel would provide a smoother ride for the user on the rough and cobbled roads. So big wheels have been used on rough surfaces since the 1860s.
The historical curiousity that resulted in so many modern-era bicycles having 559mm ISO wheels (what we think of as 26") was that the pioneering band who met on Marin Mountain in California in the late 1970s to ride bicycles down offroad dirt trails did so on old Schwinn clunker bikes from the 1930s. These had wide frame clearances to accommodate their larger "ballooner" tyres, and very laid-back frame angles that allowed extra stability when careening downhill on a foolishly unsuitable bike. The tracks that these guys rode down the mountain bore very little resemblance to what we would consider an mtb trail today - they are wide, open double-track with gentle turns and rough terrain. This is what we would consider perfect 29er territory today, where there is little need for acceleration and deceleration, and the larger wheels would smooth out the lumps and bumps a bit, but the opportunity to build a "better" bike was lost in simply having fun!
Cometh the hour, cometh the bike - as the sport became more and more technical, and moved away from the three hour epic hillclimbs and fast descents that were so common during the 90s (see for example http://www.youtube.com/watch?v=QTdMEZkZyTI ), and became more about a shorter 1h45m sprint over much harder, more technically demanding courses (i'm thinking more of this: http://www.youtube.com/watch?v=E1HteyJiOcs ) these 26" wheels suddenly came into their own; they are lighter and have a lower moment of inertia, and so require less force to accelerate compared to their larger-diameter cousins, perfect for twisty, tight fast-slow racing. But of course, no XC race can contain *just* technical features, and so of course there will always be fast sections where a larger wheel would win out.
The point I am trying (and possibly failing) to make, is that in terms of perceived benefits, changing wheel size is always going to be a compromise. If you can imagine the same rider is capable of winning a world cup race, where the differences are smallest between athletes, on any size of bike, it suggest the optimisation curve is very shallow indeed. As a former design engineer, i know what i would have been encouraged to do in this situation. I would have been encouraged to look for quick wins, but not waste time trying to infinitely refine because it makes little difference and costs a lot of time and money. So there are two explanations for the fact that the bike industry has pursued this apparent hiding to nowhere - either because they are led by their representative athletes (like Scott with their 650b prototype for Schurter), and are prepared to sink potentially millions of Euros to help them get the "marginal gains" to win. Or, the more cynical view would be that the industry has isolated a new way of encouraging us to buy a second bike, especially if we are easily-led racers, and with that realisation they are prepared to make an investment.
I am aware that i have been jaded by my experiences of working in industry to some degree, but it seems highly unlikely that manufacturers would expect to see a return of ~1M Euros from having their riders win world cups, it would perhaps improve their selling power a bit, but actually the top-end race models comprise a tiny component of overall sales. And most people don't buy new race bikes all the time. So it makes sense to believe that they think this is a great way to sell us a second race bike - if we all do it, and they're ahead of the curve, that's a lot of revenue!
I am prepared to believe that there are small gains to be made by particular bikes on particular courses, but i would imagine that they pale into insignificance ccompared to the effect of the riders themselves. I don't imagine that if Absalon had been on a 29er at the Dalby World Cup last year he'd have roasted Kulhavy, or even that he'd have finished in a different place in the final results. I can see the sense in bigger wheels for bigger people, but ultimately you should ride what you're comfortable with and what allows you to have a good position. For me, that's a 26er - i'm too short to get the position i like on a 29er, and the way i like to descend wouldn't suit a 9er anyway. The "its always faster" fanboys have missed a crucial point in their testing - the psychological placebo effect, that if you think something will be faster, you will sub-consciously ride to make it so. That doesn't work for me, as a physicist and engineer, i know it's not faster, it's just a compromise which puts a different emphasis on straight line and cornering speed, so i may as well stick with what i like!
Southern XC Rd1
With the entire XC season packed into March-July, i have to admit that i'm sort of relieved to have made it to mid-March before hitting the trails in anger. When i first saw the racing calendar in December, i had apocalyptic visions of racing every weekend from the beginning of February through wind, hail and snow, only to see the best months of the year pass with barely a race to do! A slight shift of focus towards more marathon racing, and particularly some more European stuff involving proper mountains means that this isn't going to be the case, and i can look forward to the best (and worst) that July and August have to throw at me see through the tunnel of racing vision.
For now, I seem to have done my usual trick of tuning up the "diesel" side to my racing engine, whilst having done nothing to improve on anything beyond my TT threshold. I have only myself to blame, my weekday base training has been sitting on the turbo trainer mashing out 20m threshold pieces, whilst weekends have been spent exploring the Kent hills on-road, and the North Downs off-road. It's not a bad way to do thing, but i always find myself caught like a rabbit in the headlights come mid-February, not wanting to make the switch to shorter, harder intervals-based sessions because i'm happy in my little twenty-minute bubble. It generally takes the first XC race of the year, usual the NPS at Sherwood to make me realise that i must try harder, and that XC racing is about going over and under your threshold, and not just sitting steadily at it!
This time, i had a busy weekend of seeing friends, collecting a bike, and racing at the fantastic old-school venue of Checkendon to break me out of my early-season funk. It was great to see Sarah and Trev, and stay in their new little house, and fantastic to pick up my new Trek 9.9ssl (a hardtail and a 26er - what a luddite i am!) from AWCycles, who have once again excelled themselves in their support of me. Armed with some measurements taken off my poor, cracked Kinesis, setting the Trek up was pretty easy, and to my surprise, i found myself really rather liking the riser bars that came as stock on it. Maybe i'm starting to get this new-school XC malarkey!
Poor kinesis frame - cracked along the top of the chainstay. Here's my original blog about receiving it almost 3 years before it broke... http://overthehillracing.blogspot.co.uk/2009/03/good-things-come-in-boxes.html
Rachel and Sarah got to the venue earlier than us, a necessary evil given that Rachel's race started at 10am, by the time me, Trev and Nick arrived, she was already finished, and had come away with 2nd place behind Mel Alexander (Cardiff Jif/JRA) in the elite race. I went for a pedal around the course with team mate Simon Ernest (you can read his excellent article here: http://simonernest.blogspot.co.uk/2012/03/its-not-about-bike.html), it was good to catch up with him and see what was in store for us during the race. Steve James' description of "like riding through nutella" is pretty apt, slippery, muddy, rooty, fun, a bit scottish was what i thought. I had no idea how my race would go, but i knew whatever, i'd leave smiling.
We were gridded up pretty quickly, a good thing given the chilly wind that was nipping at all of us as we stood waiting for the start, and off with a minute's gap to the elite riders. For the first time since i started racing expert, i managed to stay somewhere in the pack at the start, and even found myself moving forwards a couple of places once we got through the first few turns - perhaps all those competitive commuters at the traffic lights in London have done me some good after all! It was not to be however, and after some short battler with Tom Ward (Giant Radlett) , Ed Rose (Progression Fitness) and Richard Lewis (CC Basingstoke) i started to feel the lactate building up, and slipped backwards. With this inexorable slide came a shift of focus from riding for places to trying to ride smoothly and treating the experience as a valuable training ride, that was until i saw Richard suffering up ahead (sorry!).
I dragged my tired body across the line 16th, nearly 12m down on Jason Bouttell who tore the legs off the Sport category last year, and is showing no intention of slowing down this year either. Not a great result, but a few national ranking points and a good 1.5hrs of hard riding on my new bike to get me used to it, and most importantly i set the bar low; i can move forward from here!!
It was great to return to a course that was the scene of my first outing in sport way back in the heady days of 2006, and where i first got the bug for racing rather than riding. I wonder how i would compare to myself six years ago as a racer...
For now, I seem to have done my usual trick of tuning up the "diesel" side to my racing engine, whilst having done nothing to improve on anything beyond my TT threshold. I have only myself to blame, my weekday base training has been sitting on the turbo trainer mashing out 20m threshold pieces, whilst weekends have been spent exploring the Kent hills on-road, and the North Downs off-road. It's not a bad way to do thing, but i always find myself caught like a rabbit in the headlights come mid-February, not wanting to make the switch to shorter, harder intervals-based sessions because i'm happy in my little twenty-minute bubble. It generally takes the first XC race of the year, usual the NPS at Sherwood to make me realise that i must try harder, and that XC racing is about going over and under your threshold, and not just sitting steadily at it!
This time, i had a busy weekend of seeing friends, collecting a bike, and racing at the fantastic old-school venue of Checkendon to break me out of my early-season funk. It was great to see Sarah and Trev, and stay in their new little house, and fantastic to pick up my new Trek 9.9ssl (a hardtail and a 26er - what a luddite i am!) from AWCycles, who have once again excelled themselves in their support of me. Armed with some measurements taken off my poor, cracked Kinesis, setting the Trek up was pretty easy, and to my surprise, i found myself really rather liking the riser bars that came as stock on it. Maybe i'm starting to get this new-school XC malarkey!
Poor kinesis frame - cracked along the top of the chainstay. Here's my original blog about receiving it almost 3 years before it broke... http://overthehillracing.blogspot.co.uk/2009/03/good-things-come-in-boxes.html
Rachel and Sarah got to the venue earlier than us, a necessary evil given that Rachel's race started at 10am, by the time me, Trev and Nick arrived, she was already finished, and had come away with 2nd place behind Mel Alexander (Cardiff Jif/JRA) in the elite race. I went for a pedal around the course with team mate Simon Ernest (you can read his excellent article here: http://simonernest.blogspot.co.uk/2012/03/its-not-about-bike.html), it was good to catch up with him and see what was in store for us during the race. Steve James' description of "like riding through nutella" is pretty apt, slippery, muddy, rooty, fun, a bit scottish was what i thought. I had no idea how my race would go, but i knew whatever, i'd leave smiling.
We were gridded up pretty quickly, a good thing given the chilly wind that was nipping at all of us as we stood waiting for the start, and off with a minute's gap to the elite riders. For the first time since i started racing expert, i managed to stay somewhere in the pack at the start, and even found myself moving forwards a couple of places once we got through the first few turns - perhaps all those competitive commuters at the traffic lights in London have done me some good after all! It was not to be however, and after some short battler with Tom Ward (Giant Radlett) , Ed Rose (Progression Fitness) and Richard Lewis (CC Basingstoke) i started to feel the lactate building up, and slipped backwards. With this inexorable slide came a shift of focus from riding for places to trying to ride smoothly and treating the experience as a valuable training ride, that was until i saw Richard suffering up ahead (sorry!).
I dragged my tired body across the line 16th, nearly 12m down on Jason Bouttell who tore the legs off the Sport category last year, and is showing no intention of slowing down this year either. Not a great result, but a few national ranking points and a good 1.5hrs of hard riding on my new bike to get me used to it, and most importantly i set the bar low; i can move forward from here!!
It was great to return to a course that was the scene of my first outing in sport way back in the heady days of 2006, and where i first got the bug for racing rather than riding. I wonder how i would compare to myself six years ago as a racer...
Wednesday 7 March 2012
The big debate
So it all started innocuously enough - the most poorly-guarded tech secret of the year came out with this post on cyclingnews.com http://www.cyclingnews.com/news/tech-colnago-launch-c59-disc . So after the cross revolution caused by discs, the industry was keep to get early-adopters on them on the road as well. Whilst superficially similar in appearance, the differences between a cross bike and a road bike go well beyond some extra rubber on the tyres, and whilst i can see the sense, to some degree, in disc brakes for cross, the idea of using them on the road had me scratching my head.
Being a physicist by training, i don't just scratch my head, i like to start drawing pictures and thinking about forces. This is where the putative "disc brake revolution" really falls down for me. So let's look at why...
Firstly, a bit of history. Disc brakes appeared on the mountain bike scene in the mid-90s, it's 20 years since Hope released their first disc brake for mountain biking, and it's fair to say that almost no mtb, whether intended for XC, Downhill, Enduro, Freeride, Gnar-Core etc etc comes with the previous incarnations of technology, the V-brake or the cantilever. So how did they come into the sport, and why are they so universal? The early-adopters, as is so often the case, were the DH crowd - they were tired of struggling with stiff v-brake levers that were unable to apply sufficient force to the rim of the wheel to slow them down, in spite of using wide tyres with well-designed treads. The difficulty of applying sufficient force compounded the all-too-common issue of "arm pump" where the muscles in the forearm become painful from pushing on the muscle sheath, and would cause a further reduction in control. In short, the technical sport of downhill was becoming more about who could cope with the arm-pain!
When disc brake technology crossed over from motorbikes through motorcross, at much the same time as oil damped (as opposed to elastomer-damped) forks, downhill riders were keen to adopt it. They could now leave braking later, relying on applying less force at the lever to generate the same braking force at the tyre, and had the added advantage that disc brakes were away from the wheel rims, meaning that in foul conditions they didn't suffer from the same fade and unpredictability that bedevilled v-brakes. Within a few years, discs were everywhere, the extra weight they added to bikes (they were significantly heavier than v-brakes at this time) more than compensated by the improved performance they allowed. With the improved performance of the brakes, the limiting factor became the tyres riders were using, the narrow 2" rubber of the 90s was too narrow to cope with the extra braking forces, and it was soon the case that DH racers were up-sizing to 2.5" tyres that could once again handle the job.
It took a little longer for XC riders, and especially racers to embrace the new technology, which initially required significant extra weight, not just for the levers, hoses and calipers, but also because frames had to be built much more robustly around the anchoring points for the brakes (a simple bit of physics, rim brakes apply their force approximately 30cm from the centre of the hub, whereas disc brakes are around 8cm from the axle, and so apply ~4 times the force of rim brakes to the frame where they are anchored). When i started mtbing again as an adult (back in the heady days of 2003), discs were pretty ubiquitous even on
lower-end models. There were still design issues however, as people discovered that the shape of fork dropouts and placement of the caliper were vital to keeping the wheel in the fork when braking hard - there were a couple of high-profile accidents in 2003 in fact that highlighted this problem, and made us as a community realise that even the mature technology of disc brakes required extra development and thought to become as trusted as v-brakes had been. As they became more universal, people discovered that there were potential problems that had not been noted on the race course, where by definition, descents tended to be short, and racers extremely competent. Particular problems seemed to arise from your average rider descending for long periods of time in mountainous areas - the heat build-up in brakes that are in constant use for a long time was too great, and was causing the fluid to boil
You might very well ask, what was the point of that wander down history lane? Well, given that there is all this history of the development of discs for offroad use, we might viably ask, what can we learn? Well, there are a number of points that are relevant, where the brakes have superceded previous technologies, what changes in technology they have elicited, and what their limitations are. I think factually, it's pretty uncontroversial to say that over the course of an XC race on dry tracks, it makes little difference if you're riding discs or not. Hydraulic disc brakes come into their own where the rider requires:
(1) repeated or continual hard braking (better tranfer of force from lever to point of application - note this mechanical advantage is lessened by using cable discs) - this lessens rider arm fatigue.
(2) resilience to foul conditions - the hydraulic lines are unaffected by mud (not so cable discs, which by their nature have many problems in common with vees), all discs are further from the tyre and not as likely to be coated with mud and sludge, and allow better frame clearances (although these are often limited by other factors anyway!).
Like anything though, they have their limitations. These are particularly
(1) They are less good at dissipating heat than rim brakes - the brake rotors are generally made of steel, which conducts heat better and has a higher specific heat than aluminium rims, but there is also many times less thermal mass in a rotor than in a rim. If you have problems with aluminium or carbon rims overheating on descents, then discs are not the answer, especially given that based on the design of the system, overheating can result in two possible outcomes - either the brakes clamp on (closed hyrdaulics) or the fluid overheats and they cease to work (open system). Either is pretty bad!
(2) The braking force you can apply is limited by the width of the tyre - if you're able to apply more force you're more likely to run out of traction, and given that disc brakes work better in the wet than v-brakes, where tyre traction is lower, this is a particular worry scenario.
(3) They apply significantly more force to the frame requiring much stronger frame designs, which means extra weight in the short term, whilst designers get their finite-element work done in the longer term. There is also the potential for front wheels "popping out" under hard braking with fork designs are based around much weaker caliper brakes.
Bearing these plusses and minuses in mind, it seems hard to justify the need for disc brakes on road bikes - they're just not necessary, and in the wrong situations could even be detrimental to rider safety. The plusses do not address problems that are common amongst road riders and racers, who rarely have to cope with repeated hard braking(and live to tell the tale) or muddy tracks, and the minuses seem to be too great for the same people. The only conclusion i can come to is that this is a way to sell us, the consumers, something we don't want or need. I am prepared to change my opinions in the face of well-reasoned, physical arguments, but i have so far heard nothing to make me deviate from my opinion above. It will be interesting to watch the adoption or not of disc brakes on the road...
Next week, i'll piss off the 29er consortium - stay tuned :).
Being a physicist by training, i don't just scratch my head, i like to start drawing pictures and thinking about forces. This is where the putative "disc brake revolution" really falls down for me. So let's look at why...
Firstly, a bit of history. Disc brakes appeared on the mountain bike scene in the mid-90s, it's 20 years since Hope released their first disc brake for mountain biking, and it's fair to say that almost no mtb, whether intended for XC, Downhill, Enduro, Freeride, Gnar-Core etc etc comes with the previous incarnations of technology, the V-brake or the cantilever. So how did they come into the sport, and why are they so universal? The early-adopters, as is so often the case, were the DH crowd - they were tired of struggling with stiff v-brake levers that were unable to apply sufficient force to the rim of the wheel to slow them down, in spite of using wide tyres with well-designed treads. The difficulty of applying sufficient force compounded the all-too-common issue of "arm pump" where the muscles in the forearm become painful from pushing on the muscle sheath, and would cause a further reduction in control. In short, the technical sport of downhill was becoming more about who could cope with the arm-pain!
When disc brake technology crossed over from motorbikes through motorcross, at much the same time as oil damped (as opposed to elastomer-damped) forks, downhill riders were keen to adopt it. They could now leave braking later, relying on applying less force at the lever to generate the same braking force at the tyre, and had the added advantage that disc brakes were away from the wheel rims, meaning that in foul conditions they didn't suffer from the same fade and unpredictability that bedevilled v-brakes. Within a few years, discs were everywhere, the extra weight they added to bikes (they were significantly heavier than v-brakes at this time) more than compensated by the improved performance they allowed. With the improved performance of the brakes, the limiting factor became the tyres riders were using, the narrow 2" rubber of the 90s was too narrow to cope with the extra braking forces, and it was soon the case that DH racers were up-sizing to 2.5" tyres that could once again handle the job.
It took a little longer for XC riders, and especially racers to embrace the new technology, which initially required significant extra weight, not just for the levers, hoses and calipers, but also because frames had to be built much more robustly around the anchoring points for the brakes (a simple bit of physics, rim brakes apply their force approximately 30cm from the centre of the hub, whereas disc brakes are around 8cm from the axle, and so apply ~4 times the force of rim brakes to the frame where they are anchored). When i started mtbing again as an adult (back in the heady days of 2003), discs were pretty ubiquitous even on
lower-end models. There were still design issues however, as people discovered that the shape of fork dropouts and placement of the caliper were vital to keeping the wheel in the fork when braking hard - there were a couple of high-profile accidents in 2003 in fact that highlighted this problem, and made us as a community realise that even the mature technology of disc brakes required extra development and thought to become as trusted as v-brakes had been. As they became more universal, people discovered that there were potential problems that had not been noted on the race course, where by definition, descents tended to be short, and racers extremely competent. Particular problems seemed to arise from your average rider descending for long periods of time in mountainous areas - the heat build-up in brakes that are in constant use for a long time was too great, and was causing the fluid to boil
You might very well ask, what was the point of that wander down history lane? Well, given that there is all this history of the development of discs for offroad use, we might viably ask, what can we learn? Well, there are a number of points that are relevant, where the brakes have superceded previous technologies, what changes in technology they have elicited, and what their limitations are. I think factually, it's pretty uncontroversial to say that over the course of an XC race on dry tracks, it makes little difference if you're riding discs or not. Hydraulic disc brakes come into their own where the rider requires:
(1) repeated or continual hard braking (better tranfer of force from lever to point of application - note this mechanical advantage is lessened by using cable discs) - this lessens rider arm fatigue.
(2) resilience to foul conditions - the hydraulic lines are unaffected by mud (not so cable discs, which by their nature have many problems in common with vees), all discs are further from the tyre and not as likely to be coated with mud and sludge, and allow better frame clearances (although these are often limited by other factors anyway!).
Like anything though, they have their limitations. These are particularly
(1) They are less good at dissipating heat than rim brakes - the brake rotors are generally made of steel, which conducts heat better and has a higher specific heat than aluminium rims, but there is also many times less thermal mass in a rotor than in a rim. If you have problems with aluminium or carbon rims overheating on descents, then discs are not the answer, especially given that based on the design of the system, overheating can result in two possible outcomes - either the brakes clamp on (closed hyrdaulics) or the fluid overheats and they cease to work (open system). Either is pretty bad!
(2) The braking force you can apply is limited by the width of the tyre - if you're able to apply more force you're more likely to run out of traction, and given that disc brakes work better in the wet than v-brakes, where tyre traction is lower, this is a particular worry scenario.
(3) They apply significantly more force to the frame requiring much stronger frame designs, which means extra weight in the short term, whilst designers get their finite-element work done in the longer term. There is also the potential for front wheels "popping out" under hard braking with fork designs are based around much weaker caliper brakes.
Bearing these plusses and minuses in mind, it seems hard to justify the need for disc brakes on road bikes - they're just not necessary, and in the wrong situations could even be detrimental to rider safety. The plusses do not address problems that are common amongst road riders and racers, who rarely have to cope with repeated hard braking(and live to tell the tale) or muddy tracks, and the minuses seem to be too great for the same people. The only conclusion i can come to is that this is a way to sell us, the consumers, something we don't want or need. I am prepared to change my opinions in the face of well-reasoned, physical arguments, but i have so far heard nothing to make me deviate from my opinion above. It will be interesting to watch the adoption or not of disc brakes on the road...
Next week, i'll piss off the 29er consortium - stay tuned :).
Seasoned Professional or Impassioned Amateur
I spent a very pleasant week last week in Boston at a physics conference. You might think that the two things are mutually exclusive, but i have to admit that i relish any opportunity to indulge my inner geek, and 8000 people who have the same interest in the amazing variety of the world around us gave a perfect vent to that! One evening, i was having dinner with my PI (Principal Investigator, just like in Magnum PI, perhaps an over-fancy term for boss!), and he proffered the opinion that the physics world divides roughly into two camps. So let me introduce the two groups of protagonists:
On the one hand, we have the seasoned professionals, the people who pursue their art with an enthusiasm borne of the pride they take in their achievements. These are people who can work enormous hours driven by their contribution to history - they publish incredible papers, but they could turn this laser-like focus to other avenues and be successful.
On the other, we find the impassioned amateurs. people who's love of the subject matter in particular drives them forwards, and who would probably still do physics in their spare time. They achieve not through a drive for success but through sheer nosiness, and through a fascination with the rules of the world.
This is not to say that either group is in some sense "better" or more successful than the other, it's merely an expression of people's motivation for doing what is, after all, not always a very rewarding subject!
It occurred to me that the same is true almost universally, but that it also equally applies to cyclists - there are people who race bikes to taste the sweetness of victory and to push themselves to be as good as they can be (the professionals) and there are the people who race their bikes because, win or lose, they love every minutes that they are on two wheels. I think i know which camp i fall into in both physics and cycling, but it's an interesting thought experiment to imagine myself in the other camp. So which is it, do you consider yourself an amateur or a pro?
On the one hand, we have the seasoned professionals, the people who pursue their art with an enthusiasm borne of the pride they take in their achievements. These are people who can work enormous hours driven by their contribution to history - they publish incredible papers, but they could turn this laser-like focus to other avenues and be successful.
On the other, we find the impassioned amateurs. people who's love of the subject matter in particular drives them forwards, and who would probably still do physics in their spare time. They achieve not through a drive for success but through sheer nosiness, and through a fascination with the rules of the world.
This is not to say that either group is in some sense "better" or more successful than the other, it's merely an expression of people's motivation for doing what is, after all, not always a very rewarding subject!
It occurred to me that the same is true almost universally, but that it also equally applies to cyclists - there are people who race bikes to taste the sweetness of victory and to push themselves to be as good as they can be (the professionals) and there are the people who race their bikes because, win or lose, they love every minutes that they are on two wheels. I think i know which camp i fall into in both physics and cycling, but it's an interesting thought experiment to imagine myself in the other camp. So which is it, do you consider yourself an amateur or a pro?
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