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?
Saturday, 14 January 2012
The "Lethal Contraption"
The title of this post come from Rachel's pet-name for a bit of off-season engineering i indulged in. Whilst the name is tongue-in-cheek, if you decide to try making your own one of these, you do so entirely at your own risk, and i encourage you to take all reasonable safety precautions to protect yourself in case anything should go wrong. This includes wrapping the pressurised parts of the system in blankets, and wearing eye and ear protection, and only using this setup outdoors.
Not a lot of people know this, but the humble 2 litre fizzy drinks bottle is designed to withstand an internal pressure of 175psi before bursting. Your average person would find this (a) not very interesting and (b) not very useful, but it transpires that science-minded mtbers have been using this dry fact to great effect for some time. Well, mtbers and water-rocket enthusiasts...
Enter, stage right, the nightmare job that has bedevilled the days and nights of many an mtb rider and racer alike, seating tubeless tyres, or worse still non-tubeless specific tyres onto lightweight racing rims. Conventional wisdom suggests that it is "merely a case of getting a sufficiently snug fit between the tyre and whatever you're using to seal the spoke holes in the rim". Except most of us that have spent half an our furiously pumping only to be met by a soggy and uninflated mess of tyre, soap bubbles and latex solution know that this isn't quite the case. Those of us who are a little further from their student days than me and Rachel are faced with two choices: return to the humble innertube, which has served cyclists since 1891 when Edouard Michelin first set them loose upon the world, or indulge themselves with an expensive, and not very portable compressor. But thanks to our intrepid two-wheeled inventors, there is now an alternative possibility.
With a collection of bits and bobs you can buy from your local handy DIY emporium (the Mica home store in St. Andrews was particular good for this kind of thing) you can assemble for a couple of quid something that will do the same job as >£100 of compressor. To do the full Blue Peter thing, you will need:
2 Litre Pop bottle (note, it MUST be one that is used to contain fizzy drinks, if you use a bottle not designed to withstand pressure, it'll just burst before you have enough air in it, and you'll be picking bits of plastic out of your face for weeks)
Old track pump hose and nozzle (or do what i did, and treat your elderly track pump to a new hose etc, and use the old one for this contraption)
2 old innertubes with replaceable valve cores
2 jubilee clips
some rubber o-rings that will fit over the valve stems on the innertubes
a bulldog clip big enough to clamp over a kink the hose to prevent air escaping
eye protection, and a blanket/doormat to cover the bottle when full of air
Tools: drill bit which is the same diameter as your valve stems, vice/clamp, screwdriver for jubilee clips
Creating the "compressor" is pretty simple.
(1) Drill two holes in the top of the bottle (clamp it in the vice to do this), leaving a decent space between the two of them. Cut out the valve stems from the inner tubes, leaving a small amount of the rubber from the tube around the bottom of the stem to aid sealing.
(2) Push an o-ring over each valve, and down to the bottom of the stem, and then insert the valve through the holes in the lid so that the stems will stick out of the bottle top like a pair of antennae. Use the little metal rings that come with innertubes to secure the valve stems to the bottle lid, and to squash the o-rings to form an airtight seal.
(3) Remove the valve core from one of the valve stems, and push the free end of the track pump hose over the top. Secure the hose to the valve stem with a couple of jubilee clips to make sure you have another airtight seal.
(4) Finally, wrap several layers of duct tape around the curve of the bottle at several positions along its length to give it a bit more structural strength.
(5) Test the whole rig-up by filling the bottle with water (an effectively incompressible fluid, and therefore much less capable of storing lots of energy) and then kinking the hose and securing it with the bulldog clip. Attach a track pump to the open valve, and pump up to 120psi. Assuming the pressure doesn't drop, and water doesn't spray everywhere, you have a working tubeless compressor.
To use the compressor, kink the tube near the track pump head, and secure with the bulldog clip. Pump the chamber up to around 120psi, attach the pump head to the valve of the tubeless tyre you're trying to seat, undo the bulldog clip and hopefully the inrush of high pressure air will be enough to seat all but the most stubborn of tyres!
Et voila, a tubeless compressor for a few quid!
Not a lot of people know this, but the humble 2 litre fizzy drinks bottle is designed to withstand an internal pressure of 175psi before bursting. Your average person would find this (a) not very interesting and (b) not very useful, but it transpires that science-minded mtbers have been using this dry fact to great effect for some time. Well, mtbers and water-rocket enthusiasts...
Enter, stage right, the nightmare job that has bedevilled the days and nights of many an mtb rider and racer alike, seating tubeless tyres, or worse still non-tubeless specific tyres onto lightweight racing rims. Conventional wisdom suggests that it is "merely a case of getting a sufficiently snug fit between the tyre and whatever you're using to seal the spoke holes in the rim". Except most of us that have spent half an our furiously pumping only to be met by a soggy and uninflated mess of tyre, soap bubbles and latex solution know that this isn't quite the case. Those of us who are a little further from their student days than me and Rachel are faced with two choices: return to the humble innertube, which has served cyclists since 1891 when Edouard Michelin first set them loose upon the world, or indulge themselves with an expensive, and not very portable compressor. But thanks to our intrepid two-wheeled inventors, there is now an alternative possibility.
With a collection of bits and bobs you can buy from your local handy DIY emporium (the Mica home store in St. Andrews was particular good for this kind of thing) you can assemble for a couple of quid something that will do the same job as >£100 of compressor. To do the full Blue Peter thing, you will need:
2 Litre Pop bottle (note, it MUST be one that is used to contain fizzy drinks, if you use a bottle not designed to withstand pressure, it'll just burst before you have enough air in it, and you'll be picking bits of plastic out of your face for weeks)
Old track pump hose and nozzle (or do what i did, and treat your elderly track pump to a new hose etc, and use the old one for this contraption)
2 old innertubes with replaceable valve cores
2 jubilee clips
some rubber o-rings that will fit over the valve stems on the innertubes
a bulldog clip big enough to clamp over a kink the hose to prevent air escaping
eye protection, and a blanket/doormat to cover the bottle when full of air
Tools: drill bit which is the same diameter as your valve stems, vice/clamp, screwdriver for jubilee clips
Creating the "compressor" is pretty simple.
(1) Drill two holes in the top of the bottle (clamp it in the vice to do this), leaving a decent space between the two of them. Cut out the valve stems from the inner tubes, leaving a small amount of the rubber from the tube around the bottom of the stem to aid sealing.
(2) Push an o-ring over each valve, and down to the bottom of the stem, and then insert the valve through the holes in the lid so that the stems will stick out of the bottle top like a pair of antennae. Use the little metal rings that come with innertubes to secure the valve stems to the bottle lid, and to squash the o-rings to form an airtight seal.
(3) Remove the valve core from one of the valve stems, and push the free end of the track pump hose over the top. Secure the hose to the valve stem with a couple of jubilee clips to make sure you have another airtight seal.
(4) Finally, wrap several layers of duct tape around the curve of the bottle at several positions along its length to give it a bit more structural strength.
(5) Test the whole rig-up by filling the bottle with water (an effectively incompressible fluid, and therefore much less capable of storing lots of energy) and then kinking the hose and securing it with the bulldog clip. Attach a track pump to the open valve, and pump up to 120psi. Assuming the pressure doesn't drop, and water doesn't spray everywhere, you have a working tubeless compressor.
To use the compressor, kink the tube near the track pump head, and secure with the bulldog clip. Pump the chamber up to around 120psi, attach the pump head to the valve of the tubeless tyre you're trying to seat, undo the bulldog clip and hopefully the inrush of high pressure air will be enough to seat all but the most stubborn of tyres!
Et voila, a tubeless compressor for a few quid!
Saturday, 31 December 2011
A season to look forward to
It's new year's eve. The tradition on new years is to take stock of the year, decide what has gone well and where you need to improve, and carry that enthusiasm for change into the coming year. But the truth is, i'm too excited about the year ahead to spend long looking back on the past 12 months. As a cursory nod to this most incontravertible tradition, however, i can give a month-by-month review of the year.
January - snow, move, cold, tired, no riding.
February - work, learn, learn more, still cold, ride a bit. Race - mud.
March - sudden warm, ride more, Race- mud, mechanical, Race2 - dry, fast, flat, boring. April - ride with new friends, race with old friends, discover Kemback
May - birthday, more riding, great weather, tanlines
June - Transgermany, crap weather, more riding, great views
July - Rain rain go away, more mechanicals
August - Lost for what to do
September - December: 3 Peaks, blurrrrrr...
Next Year poses something of a change for me, and for the XC community as a whole. The regionalisation of the NPS is a fantastic opportunity for the improvement of racing in the UK, but i suspect its implementation will be less than perfect, and realistically it could represent an initial step backwards for XC. This conveniently coincides with a shift of focus for Team AW as a whole, and also a certain level of, not boredom exactly, but lack of enthusiasm for XC for me. The coming season then will be built around other things. In the main they are: Gorrick Spring Series (these races i'm hoping will form the cornerstone of my early-season speed development - the quality of the Elite/Expert fields almost automatically designates me as an also-ran!), Crystal Palace Crit Series (they're amazingly close to home, and i've always wanted to be able to race crits for training and a bit of bunch-racing practice), CRC Marathon series (well the middle three that don't clash with other grander aims), and then selected other races.
These come mostly from my wishlist of races i have wanted to do for a long time, and in no particular order are:
Roc Lassagais - Part of the UCI Marathon Series in the Cevennes National Park
Stategg Marathon - Another UCI race, but based in Switzerland
Grand Raid Cristalp - depending on how work commitments work out, i really want to give this one a go next year
Kielder 100 - Has to be done again, it really bothered me missing it last year.
But it all kicks off tomorrow, the first race of 2012 is also on the first day - and probably the closest of the whole year too, as Rachel and I head over to Herne Hill to race the new year's day madison. From there, it's a slow, gradual build to April where my rather modest aim is to not be last....
January - snow, move, cold, tired, no riding.
February - work, learn, learn more, still cold, ride a bit. Race - mud.
March - sudden warm, ride more, Race- mud, mechanical, Race2 - dry, fast, flat, boring. April - ride with new friends, race with old friends, discover Kemback
May - birthday, more riding, great weather, tanlines
June - Transgermany, crap weather, more riding, great views
July - Rain rain go away, more mechanicals
August - Lost for what to do
September - December: 3 Peaks, blurrrrrr...
Next Year poses something of a change for me, and for the XC community as a whole. The regionalisation of the NPS is a fantastic opportunity for the improvement of racing in the UK, but i suspect its implementation will be less than perfect, and realistically it could represent an initial step backwards for XC. This conveniently coincides with a shift of focus for Team AW as a whole, and also a certain level of, not boredom exactly, but lack of enthusiasm for XC for me. The coming season then will be built around other things. In the main they are: Gorrick Spring Series (these races i'm hoping will form the cornerstone of my early-season speed development - the quality of the Elite/Expert fields almost automatically designates me as an also-ran!), Crystal Palace Crit Series (they're amazingly close to home, and i've always wanted to be able to race crits for training and a bit of bunch-racing practice), CRC Marathon series (well the middle three that don't clash with other grander aims), and then selected other races.
These come mostly from my wishlist of races i have wanted to do for a long time, and in no particular order are:
Roc Lassagais - Part of the UCI Marathon Series in the Cevennes National Park
Stategg Marathon - Another UCI race, but based in Switzerland
Grand Raid Cristalp - depending on how work commitments work out, i really want to give this one a go next year
Kielder 100 - Has to be done again, it really bothered me missing it last year.
But it all kicks off tomorrow, the first race of 2012 is also on the first day - and probably the closest of the whole year too, as Rachel and I head over to Herne Hill to race the new year's day madison. From there, it's a slow, gradual build to April where my rather modest aim is to not be last....
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