On Bicycles, and.... what else is there?

I looked at how grade variability affected average power when climbing a hill. Honestly I thought the result was going to be larger, but the reality was it was a relatively minor effect. When the hill is very gradual, for example 1%, variations in grade of a certain fraction have little effect on speed. When the hill is very steep variations in grade are more significant, but since they increase power only via wind resistance, and wind resistance is relatively unimportant (assuming still air), again variations in grade have little effect. It's only important in the middle ground where speeds are high enough that wind resistance is relatively important but where grade variations have a relatively large influence on speed. A virtually equivalent logic applies to rolling resistance variation. A variation in rolling resistance about an average value (averaged over distance) will have the same effect as a variation in grade by the same absolute amount. So the effect of variabilit...

I've looked at this matter before, but one factor which I've seen continually neglected in all of the climbing power analysis estimates is the effect of grade variability. Road grade on climbs is almost never constant: it varies about a mean in some fashion. Yet the estimates are almost always done assuming constant speed, constant power. Now these estimates end up remarkably accurate anyway. Why? Because the grade variability effect is negligible? Well, no. It's because you're canceling one mistake with another. For example, you neglect grade variability, which always increases power, but you also neglect drafting, which always decreases power. How does grade variability increase power? It's because grade variability typically results in speed variability and speed variability yields variability results in variability in wind resistance and wind resistance, by virtue of being superlinear, is increased more by increases in speed than it is decreased by d...

Last time I described that the recursive algorithm I proposed for finding climbs in a profile was: identify all non-overlapping rateable climbs in a profile: If there's no rateable climbs of some minimum climb rating, then we're done. identify the highest-rated climb in a profile. identify all rateable climbs preceding this climb (recursive) identify all rateable climbs following this climb (recursive) I implemented this in Perl, which went a lot faster than it had taken to implement my previous, unsuccessful iterative approach. I tested this on randomly generated "profiles". I put "profiles" in quotes because they're not very realistic. I had to define a "minimal" climb, so this I decided was 5 meters gained in 0.1 km. This is a 5% (approximate) grade for only 100 meters. So to be identified as a "climb" the simulated road would need to be steeper and/or gain more altitude. Initially I used the conventional Fiets formula...

Recently I became interested in Jobst Brandt's climbing-descending algorithm for the Avocet 50. Jobst died recently, and I think it's safe to say the man was absolutely brilliant. Among his many contributions to cycling is the Avocet 50 altimeter climbing-descending algorithm, which has been the "gold standard" for determining total climbing on routes. For many years it was the most reliable determination of what a cyclist would consider "climbing", filtering out small altitude fluctuations which could easily be due to "measurement noise". But to compare Jobst's algorithm to mine I needed hill profiles. So I wrote a little code to make random hill profiles. But it gave unrealistic results: rounded profiles, where the hills were more like sine waves than jagged peaks. This wasn't too surprising because the algorithm I used was simple: generate random-normal distributed altitude points then convolve the resulting profile with a well-be...

Last time I analyzed some data from DC Rainmaker, probably riding around Paris, where I was surprised to find that he would have experienced less lateral chain deflection on a 1×11 set-up with a 44-chainring and an 11-25 cassette than he did with a compact 2×11 setup with 34-50 in the front and 11-25 in the back. This is because the 34-50 is a relatively wide chainring range, and one ends up having to chose between cross-chained options on the front: big ring with large cog os small ring with small cog, neither of which is a good choice, just to hit the mid-range of gears. Meanwhile the 1×11 is optimized for the mid-range. But what about rides with extreme terrain, climbing and descending? Here mid-range may be hardly used, spending most of the ride either in low climbing gears are large descending gears. Fortunately the second example I found, this time on the Di2Stats sample page , was highly representative. It's epic: a 60 mile ride with 9600 feet of climbing and descendin...

There's been an almost religious response to SRAM releasing 1×11 for the road. I find this puzzling, as to me it represents a valid choice for riding where super-wide range gearing isn't needed. And in the vast majority of the United States, the idea regularly riding extended steep climbs is at best a fantasy. It's restricted to European bike tours, etc. 1×11 provides basically the same gear spacing as 2×8, which honestly back in the day was fine, although also not for everyone, and those who wanted more went to triple chainrings. Today a lot of those who used triples back then are fine with wide-range 2×10 and 2×11 options. But if you want to avoid dealing with a front shifter, and maybe save a bit of weight, 1×11 can be an attractive choice. I was riding with an old colleague from Stanford Cycling, Mark, who's been riding SRAM 1×11 on hilly San Francisco Bay area rides and he loves it. But then he started racing with 2×6, and so learned to ride at a somewhat w...

The most excellent Inner Ring blog recently posted statistics on World Tour and Pro Continental professional cycling wins so far in 2015: the link is here . These numbers have come into focus due to Tinkoff-Saxo's owner, Alexei Tinkoff, sacking long-time team manager Bjarne Riis. Bjarne has been managing the team, and its predecessors, since it was founded as Team CSC in 2000. Cycling is novel relative to most team sports in that there's no definitive overall standing. The UCI repeatedly cooks up various rankings but these are always consigned to the depths of trivia: it's a sport which is very much in the moment, who wins the race today, with certain races mattering more than others. So on what's important and what's not as important is more a matter of consensus than anything else. No two people will fully agree, except perhaps those who think the Tour is the only game in town. And those "fans" are generally derided by the "purists". I...

Upon returning from a trip from KAUST in Saudi Arabia last week I connected through Frankfurt Airport. I was a bit grumpy because security had just confiscated my package of delicious Jeddah figs claiming they were a liquid hazard. It wasn't just that I was to be denied of the chance to share what I'd been finding so delicious during my 6 days at KAUST, but just as equally it seemed wrong for such fantastic fruit to go to waste, all over a ridiculous policy bourne of international paranoia. But my mood was slightly lifted when I spotted in a newsstand across from my gate the golden apple of German journalism: Tour Magazine. Depite a painfully long and even more painfully slow line at the stand, I risked being late to my boarding to buy it. And I wasn't disappointed. Edition 2015.03 of Tour had a quantitative review of 3 of the lightest frames you can buy: Trek Emonda: The Trek Emonda line is actually relatively heavy. Only the top-of-the-line SLX with the pricey vap...

Despite an early afternoon meeting for which I risked tardiness if anything went wrong, I felt a strong need to test my fitness on the Noon Ride, Wednesday edition, which climbs my favorite climb anywhere: Old La Honda Road. After the cheap LR44 batteries I'd last installed in my Powertap gave up the ghost a few weeks into my Basel Switzerland experience, I found some superior 357's (silver oxide) in a local combo department store / food store. This should have had me up and running but I didn't have the tool to remove the cover on the hub. I eventually brought it to a local shop, to see if the guy there could remove it with an open-end adjustable wrench, but it was too tight and the metal wrench risked damaging the flats on the hub cover. So I decided I didn't need power all that much in Europe and to wait until I got home. Indeed, the cover was on quite tight for some reason, and after applying some Tri-Flow to the interface between the cover and the hub, applyin...

For Low-Key Hillclimbs I have a mass-adjusted climbing score, which is based on the product of the rider mass and the rate of vertical ascent. This isn't a power calculation, but is related to power, and the units differ from power only by a factor of the gravitiational acceleration, which is roughly constant. The natural units of mass for international sports is kilograms, but this is the United States, and people here are more accustomed to dealing in pound-equivalents (pounds formally being a unit of force or weight, not mass). So rather than require riders to calculate their mass in kg, which they may be less likely to recall than their weight in pounds, I default to having them enter pounds, with an optional unit specification which can allow for other units (I presently support pounds, kilograms, stone for my Britophiles, and slugs to be pedantic). But people mess up. One friend specified his mass as "10 stone 8 pounds", a mixed unit I can't handle (my parser...

Low-Key Hillclimbs week 1 is done, and it's the first time Montebello was coordinated by someone other than Kevin Winterfield or me. Huge thanks to James Porter for taking the controls while I'm away from home and getting the series off to a successful start! We had an issue with water: surprisingly, 450 ml/rider wasn't enough at the end of a climb for which the median climbing time is well under 1 hour. But otherwise the day wasa big win. A big feature this year was the unusual (by historical standards) heat: the temperature was as high as 95F/35C for the day. This isn't especially hot, but it is by San Francisco Bay area standards, where the ocean breezes and the bay tend to maintain moderate temperatures year-round. Inland, at the central coast, things heat up. Bill Bushnell photo With Low-Key Hillclimbs, week 1 is the anchor. It's almost always Montebello Road (1998 excepted), and thus provides a certain standard for comparison for year-to-year. Rider...

For a long time I've been alarmed by the trend in carbon bikes to go to fatter and fatter tubes in a never-ending quest for higher stiffness-to-weight ratio. Indeed the trend predates carbon fiber: it goes back far further, to Cannondale, and before that, Klein with their fat-tube aluminum bikes. To save a relatively small amount of mass, giving up a large amount of wind resistance. But then as the quest for lighter carbon frames started approaching a limit, there was an effort to gain performance elsewhere. So wind resistance got renewed interest. Starting perhaps with the Kestrel Talon, there were a series of "aero road" frames which, at the cost of around 200 grams more or less, performed much better in the wind tunnel. These frames had a hard time catching on with professional riders, however. Road cycling is performed mostly in packs, with fatigue and avoiding crashing both major factors, so optimizing the bike is a lot more than optimizing speed at a given po...

Andrew Coggan published the following data on Twitter, showing a cyclist's power-duration data from two separate years: In the above, FTP is power which can be sustained for 1 hour. FRC is "functional reserve capacity" which represents how much work over FTP can be done. I've never myself tried to extract that, but it's a nice concept: similar to anaerobic work capacity in the critical power model. I extracted the data as best I could from the plot using PlotDigitzer, then fit my 4-parameter model using an envelope fit: The philosophy on the envelope fit is that only a limited number of durations represent a rider's best effort; most durations are part of longer efforts and so are sub-optimal for that particularly time duration. The fit only has validity if there are actually as many quality efforts as there are parameters in the model. So a 4-parameter model requires at least 4 quality efforts. The philosophy on the mean fit is to treat all duratio...

After the last comparison, which was a ride with some steep hills in San Francisco, I did a few more rides comparing Vector to Powertap. On that previous ride, my maximal power curve had been somewhat depressed on the Vector. Further investigation showed it appeared to be due to two points where cadence anomalously dropped on the Vector (but not the Powertap). Since Vector multiplied force by cadence by crank length to get power, if any of the three is off, the power is off. The first of these two rides was a spin around Mountain View at lunch, stopping along the way to drop a package at the post office, then pick up some cherries at the local market (Ava's), then after a bit of a loop, a stop at Trader Joe's for figs and apricots. I made good use of my handlebar bag, combing some solid power efforts with fresh summer fruit for the afternoon. Here's the maximal power curve from that ride: The next day I rode into work with SF2G, the Dawn of the Dead variant of Bayway....

Last time I compared Powertap to Vector on my Winter Allaban, I had failed to properly set the crank length on the Garmin 800. I'd set it on the Vector, but the menu item on the Garmin is a bit tricky to find, as it only appears when it is in communication with a Vector, so if you scan the menus without activating the Vector and pairing the Edge to the Vector you'll never see it, as I did not. I actually first confirmed my Edge was asserting the wrong cranklength by running the settings.fit file through fitdump. But this is a digression. I basically repeated my first calibration ride, heading steep 14th Street to Buena Vista in San Francisco and doing one-legged climbing on a more gradual grade, then riding home and doing a sprint. I previously did three comparisons where the maximal power curves of the Powertap and Vector were remarkably coincident after I scaled one of the powers by an empirically determined factor close to the 85% value which I later discovered was the r...

Thursday of both last week and this week I did a sprint workout. This involved cruising over the Sunnyvale Trader Joes, buying some rice tortillas, goat chedder, and organic blueberries, stuffing them in my pocket, then cruising residential Sunnyvale streets to the Steven's Creek trail. Along the way, on roads of relatively smooth pavement and with enough length between intersections, I do some sprints (4 each of the weeks). Then I cruise the Steven's Creek trail back across the freeway mess and do a few more (2 the first week, an extra the 2nd week when I sprinted for a green light). I'm not sure how much these help the sort of riding I do. But I think improving the top end potentially offers benefits at lower powers, as well as if I need to put in hard efforts to close gaps. I've not been a position where I was sprinting to win races in quite a long time. But sprint repeats challenge multiple aspects of riding: muscle strength, neuoromuscular coordination, pedal ...

After last week's disappointment on Old La Honda, I did a sprint workout the following day (Thursday), then rode in at tempo on Friday with Jason. But there was no riding through it. I was cooked. I needed some days off. Saturday & Sunday were total "rest" (actually doing home stuff which absolutely needed doing). Monday and Tuesday I was still feeling fatigued, so I took the train to work, riding only to-from the train. Finally, today, I felt energetic again, ready for another try at Old La Honda. Like last week, Greg and Kieran set a ferocious pace from the start, with Mark in tow. I let them go. But unlike last week, I wasn't in a chase pack, but rather solo. But also unlike last week, Mark didn't try to hang with the leaders too long. He dropped off and paced himself very nicely the rest of the way. And the whole rest of the way I chased him. I focused on trying to maintain a steadier pace this time: keep a cap on it at the beginning when I felt ...

I typically use my Powertap on training rides, but when racing, I've not done so since I placed third Ross's Epic Hillclimb up Pine Flat Road in Sonoma back around 2008 or so, At the climb, I'd decided the added weight of my Powertap wheel was worth it for the pacing advantage of power. Unfortunately, my battery died on the start line, so I carried the substantial extra mass of the Powertap up the hill for no advantage. Despite the lack of power, though, I had arguably the best climb of my life, staying with a critical surge I might well have not gone with had I been pacing off the meter. That surge led into a flat/slightly descending part where being with the group was a critical advantage. When the climbing began again, steeply, I felt as if I was going to crack, but then most of the others cracked more. Without the weight of that wheel I may well have been one place better. But power is also useful for post-ride analysis. But for that, I rely on the standard power...

Two posts back I proposed an algorithm for calculating maximal power data with a variable expiration date. For each duration, instead of retaining a single power point, I retain a list of power points where each retained point is the highest power for points of that age or newer. So going back in time for a given duration, the points are increasing power order as well as increasing age order. If my most recent effort was my highest power effort, then I have only one point in the list. In the opposite extreme, if my power decreases every activity going forward in time, I would have every activity in the list. But obviously that would be exceptional. Far more commonly powers at a given duration are sometimes higher, sometimes lower, so the number of retained points will be between the two extremes. Uploading activities to Strava on a near daily basis, it is not unusual for a user to have 1000 activities or more. So ideally this list needs to retain only a small fraction of the to...