Not a bad indoor trainer, this is my 2nd (or is it 3rd?) Elite. The roller always wears like that - amazing what hot rubber will do if you try hard enough. This is probably 8 years old, but it has shared the load with an even older - 13 years or so - Elite. The tyres of course wear even faster.
It's a magnetic resisitance unit. Not the best road feel but useful, especially when you run an iBike or similar power meter.
Once, long ago, this is what racing cyclists wore on their heads to ward off evil spirits (if they didn't wear a cap and a cabbage leaf as well, anyway). Now they wear plastic and foam. Which is weirder?
My 3rd bicycle, after the Alcon and an Apollo: it's a Viscount Sebring with a 'leather hairnet' hanging on the brake extension lever. It must be 1978!
The Alcon taught me about fixed vs freewheeling and basic stuff like puncture repairs and falling off. The Apollo introduced me to multiple (read 5x2) gears and brakes that didn't work in the wet; and the Viscount brought me into 'semi-lightweight' territory, just on the cusp of being a 'real' race bike. Indeed if I got rid of that bell and those silly 'hands-on-bars' brake extensions... and lowered the bars a tad!
This pic just brings back so many memories for me... apart from snapping this seat post (it creaked before it broke but I couldn't work out where the creak was coming from...) I have snapped seat rails (no particular warning) and a seat bolt (which left me with a 30+km ride home and nothing to sit on), and lunched a rear derailleur in the spokes of my rear wheel. Which of course broke a few spokes, too.
Ahh, spokes, Broken lots of those. Best effort was a lightweight wheel that survived a 100km road race only to unravel completely the next day. I've broken a few wheel rims, mostly by suddenly and unintentionally twisting them at right angles to my intended direction. And I've snapped the bolt that old-style stems used to secure the handlebars to the steerer tube, if you know what I mean. That results in a rather fabulous yet spooky loss of steering, BTW.
Most recently I couldn't work out what was rattling and occasionally squeaking in a strange metallic way - until it got worse. I found that I could make the sound go away if I stopped pedaling for a while, or (even better) pedaled backwards. So I deduced it was the rear hub... but what could go wrong with a hub? Ahhh, the ratchet, course.... and when it finally broke (I like to test these things to destruction) I had no effective connection between the pedals and the gears... in effect I had a permanent freewheel. Great for going downhill, not so good anywhere else...
The ibike is one of several ways to quantify power output on a bicycle. I chose ibike over SRM, Polar and PowerTap for reasons of ease-of-fitment and price - it's the cheapest option and the easiest to swap from bike to bike - although PowerTap has some advantage here as well.
The ibike measures power indirectly - it's not using actual load on a hub, BB or crankset - by crunching various fixed and variable values as you move through the air and over terrain.
I've found the ibike is almost certainly accurate on steep hills where air and rolling resistance are not such big factors. Going slowly up a hill means it's just a simple calculation using steepness of the climb, the altitude gain, overall weight and rate of movement forward. How Armstrong ever got up that Alpe d'Huez TT at something like a 450W average I'll never know. I can barely average 300W for about 200m before collapsing. (Slight exaggeration but it's something like that.)
I calibrate using online power calulators and the ibike is spot on with what you'd expect. Where it's not so good is getting an absolute value for air and rolling resistance - unfortunately these values change all the time depending upon your changing position on the bike and changing road surfaces (rough, smooth, potholed). So it's a 'one-size-fits-all' approach. OTOH it's super easy to fit and swap over to another bike.. so all my bikes (track bike as well) have the mounting and I just take it off one and pop it onto the other... and reset weight and tilt angle of course. That was the main selling feature for me.
I just have a few random ideas that may help you get started... nothing scientific, nothing guaranteed, but you may like to consider these thoughts:
Ride a bit more than usual before your first race, and push yourself a bit harder to gain some confidence
Then have a rest day before the race, or just a short, easy ride
Get into bunches and practice riding with a group
Eat well, keep fats to a minimum and eat plenty of carbs with fruit, rice and bread in the mix
Don't ride hard if you are sick or injured, or overweight (see your doctor for help there before starting any exercise program)
Remember the rule of thumb: train in a week 3 times the distance of your race - so a 30km criterium means you should do at least 90km in a week, and you need to do that at least for a month prior to build your base
Remember the other rule of thumb: you lose whatever you gained after 3 days, so don't leave it 3 days between rides
Get to the race early and warm up gently but firmly - end the warm up with a cool down and build up to a race gear, but don't over-do it
Don't cool off completely before the race
Register for the race and get your number ASAP, don't leave it to the last minute
Ride around if necessary to keep warm
Don't miss the start
Follow the experienced riders, listen to them and watch what they do
Within the limits of what you can do be prepared to dig deep and grit your teeth to "hang on"
Don't cross wheels with other riders, one swerve and you'll be down
Don't show off in your first race, just absorb and learn
Sit on "in the draft", conserve energy, don't fidget, don't surge, be smooth - momentum is everything
Stay close to and follow experienced wheels carefully, certainly not in a jerky, sudden or unpredictable way
Do a turn when your turn comes, then pull off into the wind, allowing the next rider to shelter in your draft and easily come up to replace you
As you pull off do so gradually and slowly ease up, drifting to the back
If you feel comfortable ease back into the first 3rd of the bunch, otherwise go to the back again
Do what the others do, unless they are totally out of their minds!
Be there at the end
Have a go at the sprint but be realistic - don't get in the way.
Phil Thuaux is a local up this way, so here's a nice vid of his silver at the Sydney World Cup. I think 4.23 is his best, but anyone who rides 4km under 5 minutes is practically super-human. I think Phil started out on his sister's mountain bike - he was certainly pretty quick with little training...
Enhance your cycling - set some achievable goals and go racing!
Think of this blog as my attempt to inspire you to race. I am targeting the non-racer, the recreational rider who is quite fit and interested in the sport of cycling but for whom racing is 'something I can do later' or 'something that's just a bit out of my league'.
Firstly, never put off to tomorrow what you can do today. I first 'enquired' about bike racing when I was 16 and riding perhaps 100km a week, including 60-80km 'fun rides' on the weekend. Having not been involved in competitive sport in any organised way before - I was a total bookworm -I lacked the confidence to give it a go, so I put it off - for about 8 years, in fact! What a waste.
Secondly, you never know until you give it a go. In my case I only gave it a go after much encouragement by other riders. Luckily I lived fairly close (10km away) from the premier cycling resource in Sydney, Australia - Centennial Park. So for about 8 years I frequently rode to and around the Park. Just by riding around with other riders I got fitter and faster. I found that I could chase and catch other riders and that I had an undiscovered urge to improve - and even to race. I still didn't think I could do it, but the thought entered my head that I had a chance. Eventually I found another rider at the same level and we (at the urging of another rider - as it turned out the president of one of Sydney's bike clubs, Randwick-Botany) made a commitment to try a race together at Heffron Park. We were placed in D grade. He won and I came 2nd. Now for him that 'proved' enough and he didn't race again. But for me I was hooked. I came back and won D grade the following week and went from there.
That was more than 20 years ago and I'm still racing. You'll never know unless you give it a go - and there's a grade for everyone. Just get some miles in your legs firstly - say 80-100km a week for a few months - and find somewhere where you can ride with a few others. It will improve your fitness and your bunch riding skills. You'll need a bit of both, even in the lowest grade.
So that's my motivation out of the way - what about yours?
My personal recommendation is to just go riding, enjoy it and find some buddies to encourage you. Then leverage that fitness and skill to start racing. Of course there's lots more to it than that.
For instance, what are your goals? Ask yourself 'why am I doing this?'. Is it that you want to stay fit and healthy in the long term, and to get out there riding regularly you need extra motivation? Or is it to simply try out racing, just because you'd like to? Try to understand why you want to do it and feed off that motivation. Remind yourself why on those hard days when you question the whole idea. And review your goals regularly. You may want to find out how good you could be, given whatever constraints you may have. (I always had to work (or thought I did), for example, so doing more miles on the bike was always a balancing act.)
Goal setting helps you achieve something definite. Just ambling along seeing what happens may lead you somewhere interesting but it probably won't be exactly what you wanted to do, or be the best that you want to be. It may be great and exactly what you wanted. Or it may be so disappointing that you drift off and do something else.
By aiming at achievable goals you do a few things. You are taking aim, and aiming at something improves your chances of hitting it. You are also building a set of stairs, small steps that will make it easier to climb to a higher place. If you aim at the top rung straightaway you may actually get there - we all have our 'top rung' dreams - but by setting out intermediate goals you will get there more reliably.
Let's make a list.
1. Your first goal may be to start your first race. 2. The next to finish the race. 3. The next to finish with the lead pack. 4. The next to place. 5. The next to win.
You may find that you achieve several of these quite quickly, and that's very important. It's reinforcing to actually achieve your goals, it helps you to stay motivated and to want to do it again. Feed off that feeling by keeping achievable goals!
The beauty of bike racing is that these steps fit perfectly with the system. Whether you call them grades or categories, there are always rungs of the ladder. Plenty of people find their niche on one rung and just enjoy their racing in that grade forever more. They may go higher and then settle back. They may just find a balance that suits them. Some people enjoy the tactics, some like to win. Some like to help others win. It's diversity that makes the whole cycle racing scenario work. We all do what we enjoy and that keeps us all riding - and racing.
And the racing is varied, too
Road races can be 50km, 100km or 260km, or 2,000km in a 3 week tour for that matter. Criteriums can be 30km or 100km. Track races may be short 200m sprints or 4km endurance pursuits. It doesn't really matter what your personal strengths are because there's a niche for everyone. A big strong male or female rider may power along in a time trial and then get dropped on a climb. A wiry, thin rider may struggle on the flats and in the sprints but cream the big guys on the climbs. And in between there's an infinite range of possibilities. Now that's variety - and that's bike racing.
This looks interesting... a running-based anaerobic sprint test... not exactly cycling but interesting, and a useful way to calculate power over a 35m run... annoying yellow advert takes the eye, too. Uuuugh. Aaahh but it links to this Wingate test... all is not lost. Not a bad site, actually, full of info. Like this chart on "Percentile norms for Relative Peak Power for active young adults" - especially interesting, if you happen to have a power meter handy! An average sort of club racer, IMHO, would fall into the 90th percentile, surely? Having said that I'm neither young nor average (who is?) and I go right off the scale... remembering this is PEAK power, not sustained... and I'm not particularly overweight (nor skinny).
Maud, P.J., and Schultz B.B: 1989
And this..."Percentile norms for Peak Power for active young adults" is :
Maud, P.J., and Schultz B.B: 1989
Looks like they surveyed some pretty average active people... perhaps non cyclists?
How about the Human Powered Vehicle association? Or look at this technical exercise in analysing the forces at work on a bike. Or this interesting exercise by FLAcyclist in comparing the power required to overcome a hilly bike course vs a less hilly but longer one... and Analytic Cycling is a treasure trove that will have you staring at the computer for hours... STOP IT! Go outside and ride!
It's good to just amble along, ride when you feel like it and maybe race occasionally. But guess what? If you get away with it you are very lucky. Just "ambling along" will not boost your fitness, and riding when you feel like it will not build endurance or power. You have to have a dig - test yourself against your maximums - to make improvements. And you have to do it regularly enough that what you gained one day is still there to build on today. Even if all you want to do is a recreational ride, you are better off getting regular sessions in place than 'starting all over again' every time you ride.
I'm not a coach, a nutritionalist or a physiologist - but I do ride, and I'll tell you what I believe.
You must ride 3 times a week - minimum - to maintain your condition
If you want to safely and comfortably race 30km then you must train for 3 times that distance every week for a month (so 90km a week for 4 weeks is the bare minimum for a 30km crit)
Whatever you do in excess of that rule of thumb will give you the endurance and power to compete more comfortably (to counter attacks, even make attacks) - it's up to you how much more you can do!
Intervals on top of base miles will build speed and power
Train your weaknesses, not just your strengths
Whatever strength you gain in one session will be 90% gone within a week, so do regular sessions to maintain that power (ie the torque you can apply through those cranks)
Your endurance probably declines more slowly, but after 2 weeks you'll get that "starting all over again" feeling, so avoid long gaps between rides
Regular miles not only help you build endurance but also ward off injury.
To get more technical about it, a focused training program can - indeed will, if you stick at it and don't get sick or injured - increase your VO2max by 15 to 30% over a 3-4 month period . If you stick at it consistently for 2 years or more you'll see up to a 50% improvement. Consistency is the key. Think about it - you learned to crawl, then to walk and it took years to really get the hang of it. And once you did learn to walk yyou kept at it, day in, day out. So why would you expect to jump on a bike once in a while and just go fast? In fact you need to train your mind as well as your muscles, and to build firstly the endurance and pedalling skills before getting the most out of your cycling. You do that with a plan - a plan to do ride regularly!
Training Tip 1 - find your balance and train without injury
Is more always better than less? Up to a point, sure. Ride LOTS! But yes, there is a limit. It's hard to say what's too much but listen to your body. If you feel bad, especially if you are putting in the miles and not improving, or if your heart rate is staying up when it should go down (at rest, say), take a break, lower the intensity and see if that helps. Another clue is when you can't get the heart rate up - like you used to hit 192bpm but now a maximum effort still feels like a max effort but you only hit 182. It would be nice to correlate that with workload - maybe you aren't actually working as hard as you thought- but if true then you may indeed have overtrained.
But don't kid yourself. If you have built up a base level of miles over a few months - say at least 100-200km a week - and then do some hard interval sessions on top, it is unlikely you have overtrained. Maybe. But not likely. Sudden intensity without base miles may injure you, but not overtrain you. However if you were doing 500-700km a week and laid on more on top of that then yes, overtraining is a possibility. Take a break, just in case. A week of slow riding won't hurt you!
To be a bit more scientific about it - and I'm not a coach, this is just my somewhat informed opinion - optimum training intensity varies by just a few percent between individuals, so there are some rules of thumb we can all follow to keep us improving. Such as:
It is generally believed for example, and we have ample evidence to justify this belief, that maximum aerobic improvement occurs at around 85% VO2 max, give or take a few percent
That's about 90% of your max. heart rate. So regular training above this level will increase the potential for injury without a corresponding lift in your cardiovascular adaptation - which is to say you are trying too hard, could become overtrained or injured - so back off a bit
Now lower levels of exercise - say 55% max HR for 60 minutes or even 65% max HR for 45 minutes - may modestly improve, and at least maintain, your overall conditioning... but...
Whilst that may be enough for you to stay in C grade, what if you want to get better, faster? Long steady distance training, say 50 to 70% of max HR for hours on end, will do little more than maintain status quo. Yes, it could burn off fat - a good thing. Yes, it will build endurance...
But if you are looking to increase your top end (maybe to avoid being dropped in your frenzied local crit, or to attack and break away, win and go up a grade) you need to hit the high notes. That's the 85-90% max HR mark.
It's finding a balance between too much high-intensity training and not enough that's hard. And why you pay big bucks to the experienced coaches to get that sort of result.
Of course we don't want to spend big bucks, so it's down to YOU. Hopefully in the above are some clues to improving your condition without injury.
Cycling and data. Well I was hooked on bike data long ago - firstly by writing down how far I rode, then how long it took... which gave me an average speed. Then I collected more detailed data on max speed, then heart rate and finally power output. It just gets better and better (the data collection, not the output). Here's a reassuring story I found in the NYT about similar obsessive behaviour.
ibike - part 2 - mounting it on the bike and setup
No real problems here. The ibike is just like many other bike computers and comes with a bayonet-style mount that sits on your handlebars. I chose the standard size but there is also the larger vesrion if needed. Follow the instructions though, as you need to keep the ibike absolutely 'rock-solid' on the bars. I tried using old tyre as padding at first, just to make removal easier, but settled on the double sided tape provided instead. It's easy to fit, just plan where the wire goes first. It has to get down to the forks, where the magnetic pickup gets strapped on. I kept my old speedo in place and mounted the new gear on the opposite side of the bars and forks.
Mounted it looks like this...
And the mounting itself looks like this....
All in all - dead easy. Lots of twist ties to play with but no harder than a regular 'wired' bike computer. The screws that affix the ibike mount to the bars are a bit fiddly, but it's easier on a stand, or turn the bike upside down.
Once connected I powered it up and went into setup mode. All the expected stuff: time, date, total bike and rider weight, plus the 'turn 180' exercise which levels the unit. Again, good clear instructions and I used them (for once in my life). I also zeroed out the wind (I was in a garage) and took a guess as to altitude (later riding down to sea level to make that accurate - hey I was only out by 10m!).
All up - simple and quick.
ibike - part 1 - the purchase experience
OK, so I chose the ibike.
The first hassle was the ibike shop on the web. They revamped it a bit since but you can't login to the shop without first clicking on a product and pretending to buy it (then the 'log-in' option finally appears). And when you try to log-in the login ID box is unclickable without 14 'tabs' to get you there. I tried 3 different browsers and 2 PCs... they all had the same trouble. Not everytime, just 9 times out of 10. Anyway, the tab-tab-tab until you get to the correct input box works. (Must admit I just logged in fine, so who knows?)
Enough whinging. I bought it online and found that the 'tracking' option didn't work for International US Post. Not to worry, I guess. 10 working days later it turned up fine, but opened by Australian Quarantine Services. Must have looked suss with 'Velocomp' written on the box... hmmm. Go figure.
The box looks like this:
Which is fine, although for around $A600 it's a trifle underwhelming. Still, it's the technology we are buying, isn't it?
And opening it up we find the device itself, which is tiny and very light (which is good, right?):
It's showing average Watts here in this pic but it will also show maximum values.
And then I mounted it on the bike... well 2 bikes, actually. I had bought an extra mount, so I could swap from bike to bike with ease, something I saw as a killer feature of the ibike over almost all its competition.
Wednesday, April 11, 2007
Power to the people - power meters for serious cycling
When I started this riding gig I was 16 and it was 1973. The bike was an Aussie-made Alcon, circa late 1930s and well looked after, if hand-painted. 28inch tyres, 40spoke wheels, diamond outrigger with sliding adjustment for handlebar reach and just 2 cogs on the back. On one side of the wheel was a freewheel and the other a fixie. Cool way to get started, eh? Even cooler was the mechanical odometer that clicked over incrementally with every turn of the front wheel. Ahhh, data! I started writing it down. Curiously it made me ride a bit more, just to get a scrap more data.
In the 1980s I found myself with electronic assistance in my data habit: a cycle 'computer', although all it really did was count wheel revs using a magnet and show elapsed time. It did allow me to see my current and average velocity, rather than doing the usual sums at home after the ride. And it was more accurate than some of the guesstimates I had to make. Now that sort of technology got a bit better over the last 25 years or so, but essentially remains as it was: a bunch of data based on wheel rotation over time, displayed on an LCD. (Although some of these new options are very sophisticated: check out BikeBrain for example)
Now this did make me ride for longer distances, and do more miles each week, as I could actually and accurately see when I had slacked off. And being data-obsessed I just wanted to push teh totals ever higher. Funnily enough I still had to chase down attacks, stick with the peleton over varying terrain and avoid being dropped, irrespective of what the displayed velocity was. But now I could also go 'ah, look at that average' after a hard crit.
The next leap forward in this history lesson was to the heart rate monitor. In my case it was the mid 90s and a Polar HRM. So now I could match perceived exertion against both time and distance, as well as estimate my caloric budget. It again made me ride, just to get data. Bizarre, I know. I wanted to exceed 200bpm on my local tough climb and set ever higher averages, so again I could go 'wow, that was a tough ride'.
Which brings me to my newest desire: power measurement. Up to now I've calculated it after the ride, inexactly, and longed to know how many Watts it really took to ride that hard crit. SRMs, offering measurement at the crank seemed a great option. But SRMs were (and remain) waaay too expensive, especially now I had kids to feed. The hub-based CycleOps option was still a bit rich (and what if I swapped wheels?) and Ergomo Pro was again a tad exxy and suffered (like the SRM) from being integrated into the bike. The Polar option was both expensive and tricky to set up. So I looked at the next-best options - the German HAC4 and other options from Germany and Italy, which calculated power from time, speed and altitude gain using accelerometers or barometric changes. Of course this only works on hills, but it was an option. Some of these options don't offer download, so it would be a 'write down later' sort of thing - like back to the 80s.
The HAC4 looks great options-wise but is a bit expensive compared with low-end 'real' power meters. I also looked at GPS units like Garmin's and wondered why no-one had integrated the coolest features into one unit. Maybe one day, I guess.
Anyway, I flipped a coin and went with the simplest, cheapest real-time data logging power meter I could find. The ibike. It back-calculates power by measuring the opposing forces - wind, friction and inclination - and comparing it to real speed (using a magnetic pickup). Easy to fit, easy to use. It looks the goods but does rely upon (a) your calibration accuracy and (b) unimpeded airflow. Which is to say that it misreads power if you aren't good at entering data (weight, aerodynamic and friction data, basically, although the latter is derived by the "coasting" test) or have impeded airflow (in a bunch, maybe, and certainly in a sharp corner).
I ummed and ahhed about this for weeks (whilst watching the Aussie to $US exchange rate fluctuate, too) and wondered if I really needed to spend $A580 on a gadget. I decided it was now or never and pressed the "buy" button in the ibike website. I'll tell you more later...
OK, so now I'm getting into it. It's addictive. I'm a data junkie and it's making me get out on the bike and ride, just to see what it looks like when I sprint, chase a car or climb a hill. Then I want to compare sprints, compare hills... goddamn it, I wish I had one 20 years ago! (But they didn't exist at this price, of course.)
That's the good side of the ibike - real data that makes sense. You've got to set it up right and do the coast-down test properly, as per spec, and make sure the battery is delivering the goods. But once done it's great. Of course today I punctured and swapped front wheels, but because it's just a magnetic pickup there was no sweat. I could even swap bikes as I've got a spare mount and pickup already on bike number 2. So I think ibike is still looking like a pretty good thing.
Bad news? It goes a bit screwy if you watch the Wattage display too much (it seems to jump around constantly, especially on the flat, only settling down when efforts are made, in a sprint or in a climb) - but when you download to the PC the odd figures seem to have disappeared and clarity returns. And the peak figures on the LCD don't always match the data logged. The battery seems to play a part in this, as does road surface - bumps and corners definitely throw it off.
So on to the fun.. the screenshot on the left shows power in blue and bike speed in green. You can see steady state on the left, then I accelerate to catch a slow-moving Toyota 'Landbruiser' that pulled out in front of me. You see both power and speed rise as I chase, peaking at around 865W and 45kmh or so; then as I get into the draft speed stays up (for a while, I didn't stay on as there's a nasty climb around the corner and I'm not that fit!) whilst power falls off sharply. The ibike seems to handle 'sucking wheels' pretty well. You can see that power falls away rapidly to zero until I hit the climb and have to get pedalling again. Speed falls away too and you can see me approach 300W on the lower part of the 10% climb (the bump on the right).
The next sreenshot shows a zoom-in on that power peak. You can see the effort to accelerate, the speed rising and then the power clearly falls off as I get into the draft, despite speed continuing to rise. In fact the car eventually accelerated, having suddenly realised that the rider they pulled out in front off at that T-junction was still there... and I let him go, as you see the speed dropping again. Wow.
Even better, the power breakdown (the colored box centre-screen) shows what was happening at the point where the cursor sits... all of that green in the pie chart is acceleration. The cursor itself is the black vertical line right on the power peak. So it all makes sense. When I move the cursor into the 'draft zone' the proportions all change... as you'd hope.
Bottom line? It works!
ibike - part 4 - the software install
Well the software looked good enough sitting on the CD-ROM, and it seemed to install on my PC OK - and I followed the instructions - but it failed to find the USB driver first up. I followed the instructions again, went through the whole install and once again it failed to find the driver. So I went manual in control panel and found the driver had indeed installed correctly on my hard drive, it's just that the "automatic, preferred" search doesn't look there... of course. Wonder if this happens to everyone? Anyway, it really does extract and copy it to your ibike program folder, so a bit of searching will find it. It's just a manual approach is needed when 'auto' fails. Once loaded it all worked.
The software is simple. Connect, download all or some files... ooops, it crashed. And the ibike itself froze. OK, this has only happened once, but again I followed instructions, restarted the software and took the battery out of the ibike. I popped the battery back in and it fired up again and has worked flawlessly since. In fact it works better now than before. The battery started life reading 2.80V and fell to 2.70V during the 2nd ride, before recovering to 2.78V. However after refitting (and perhaps putting the cover back on a bit tighter?) it reads 2.82V pre-ride and hasn't fallen below 2.77V. The instructions say to get a new battery if it falls below 2.75V before a ride. Perhaps my first-day glitches were battery related?
Anyway, back to the software. It's good enough. It loads up the whole ride as a .CSV file and you can 'play' with power, wind speed, elevation, slope and bike speed for starters. You basically can graph it as you like it, including looking at neat breakdowns of acceleration, hill and friction readings at any point in the ride. And you can probably read and modify it in any spreadsheet, too, given that it's saved as a .CSV (but I haven't tried - yet). It's simple, but does the job for a data junkie like me. It's strange though that the ibike itself displays slightly different maximum values than that logged in the data file. That aside, overall it's what I expected.
Thursday, April 12, 2007
ibike - part 3 - the 'coast' setup
Right, so it's mounted and ready to go. We have total weight, it's leveled (so it can tell if it's climbing or descending) and it seems to be sensing wind speed OK. Now we need to calculate the aerodynamic drag and the friction between road and tyre. Now we can estimate this pretty well, but the "coast" test will actually time your deceleration run - ie measure the drag induced by you and your bike on the road. So out we went, ibike and I, on our Look KG76 for test number 1.
It's harder to find a flat, smooth quarter-mile of road than you'd think. Slightly uphill is good, downhill is bad, bad, bad as it distorts the results. So naturally I chose a road that looked flat-to-uphill but actually wasn't, so I got some fantastic results. Fantastic as in no way could it be real.
Look at this: 1459W, man! Beat that!
Oh well, back to the "coast" test. In fact I kept finding roads with dips, declines, potholes, corners and really smooth fast bits. Which raised a question or 2 in my mind. Like how accurate is it when road conditions vary? And how is it calculating wind speed, let alone direction? I guess it's a straight subtraction of total airflow "in" minus forward velocity, and angle isn't relevant, but the final figures look odd... anyway, wind aside, if I calibrate on a smooth fast road presumably I'll get errors unless I only ride on that exact same smooth fast road... so are the errors small enough that it won't matter? Or when I get to new territory should I re-calibrate?
So I chose to retest a few times (OK, about 5 times) and compare. Firstly the ibike captured the whole thing, despite my many, many retests - which is good - and secondly I never again got the sort of fantastic result I got with the first coast test. Instead of 1459W I was now in the region of 600-1000W tops (I was getting tired, too, after countless sprints!!). So which 'coastdown' is correct? Hmmm.
Now if you look at the screenshot on the left (of the ibike software) you will see a few strange things. Firstly it shows maximum Watts on this same ride as 1495, yet the LCD display showed a maximum of 1459! Oddly similar but dyslexically different. On the right of the pic you will see the figures for a precise moment in my ride. Using those figures (28kmh wind speed, 8.9% slope etc) you could indeed calculate that a 72 kg rider at 47.5kmh on that slope is indeed putting out about 2100W, not the 'fantastic' figure of 1459/95. But to me, fallible old me, I could have sworn the road was (a) almost flat and (b) that there was little if any wind.
If you take me at my word, that it was a flat road with nil wind then Kreuzotter calculates it as 715W. I'm happy with that. So - assuming a multiply-by-2 glitch occurred - there's an error of more than a percent or 2, isn't there? Hence my scepticism and need to rerun this "coastdown" test until it checks out against 'expectations'. Or am I too harsh? Did the mostly flat road dip and climb suddenly for an instant, or did I pull up on the bars, lifting the front wheel a tad (I was sprinting, after all)... and maybe the wind suddenly gusted? No, I reckon it was a glitch.
So, I think I've got the "coast" test figured out and I'll keep it "as is" for now until I see questionable figures. Certainly my max power figures have come back to earth. Some doubt remains over what happens if you ride very different terrain, but it's easy enough to re-do the coast setup if on super-smooth or super-rough road. Perhaps do the coast test just before a race on a new circuit? Certainly do it if you swap bikes, but that's a test I'm going to do later, just to see what the diffence may be... I suspect it'll be neglible, though, unless my race wheels really are that much better!
Interesting article on track cycing in the UK... quite a turnaround for the UK, which was long mired in road TTs and inadequate outdoor tracks. The BBC reports that as well as a development program for trackies, "facilities are obviously also crucial. Britain has three indoor velodromes - in Manchester, Newport and Calshot near Southampton - with a fourth planned in London for the 2012 Olympics. The Manchester velodrome is the busiest in the world, with cyclists using it from 8am to 10pm most days, and the track is now practically worn out." It seems to be paying off in medals.
Right Brain (40%) The right hemisphere is the visual, figurative, artistic, and intuitive side of the brain. Left Brain (70%) The left hemisphere is the logical, articulate, assertive, and practical side of the brain
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