Saturday, December 31, 2011

posting slackitude and SF2G

For the first time this year since I started my blog in 2008, total posts have dropped.

Here's a plot of the rate of net posts during the year since 2008, when Cara convinced me to start the blog:

posts per year

I started a bit slowly this year, then rallied, catching my 2010 schedule. But then I started losing ground, finishing in a dead heat with 2009.

So what happened?

The answer is I started riding more. This is evident from the plot on my Strava page. Barely surviving through April, then my hours start to take off in May. Normal commute means I am in the train around 100 minutes with my laptop. SF2G means I leave home early, then have only my cell phone for my train ride home. More riding = less posting.

And that is a very good thing.

Here's another look at my SF2G schedule. I counted the number of Strava activities I had with SF2G in the title. Before the period of the plot I didn't have GPS so I'd need to check my old training logs. I may have been occasionally remiss in tagging my rides SF2G, so there may be a few not included here. But you can definitely see I started riding into work a lot more often.

SF2G rides

Through September 2010, at a previous job, I was more readily able to combine both, since I was more able to squeeze in lunch rides and even the occasional post-commute morning ride. I was on flex time, and could often do actual work on the train since much of what I did didn't require an internet connection (Caltrain has none). Now I need to be on the secure network to do "work", and in any case "face time" is more important, so working on the train then blowing out to join one of the Wednesday morning groups simply doesn't work any more. Working on the train in the morning often meant I spent the evening commute on the blog, but now if I ride in both commutes are blogless.

It's all good: I try for quality, not quantity. What really runs up the numbers is when I get hooked onto a topic, as I did with the Metrigear Vector. Serial posts on a topic become more efficient to get out.

A bit more on the SF2G rate: my SF2G's peaked in August: good weather, plenty of daylight for early starts. September tailed off, in part because I needed train time to prepare for the upcoming Low-Key Hillclimbs (scoring code, web pages). Then October-November my SF2G's were suppressed by not wanting to go into Saturday's Low-Key Hillclimb fatigued. December included holidays, and was also off.

For 2012? Who knows how the blog will go? I'll try not to set any goals. At some point I will have said enough and feel it's time to move on. But I'm not quite there yet.

Thursday, December 29, 2011

Running the Rocky Steps

This weekend I was in Philadelphia for the first time since I was a small child, visiting Cara's family. The house was only a mile from the Philadelphia Art Museum, and that got me very excited. Sure, we went to the museum (or rather the Perelman Building extension: a fascinating exhibition of Zaha Hadid's architecture), which was nice, but arguably far more famous than the museum itself is the steps leading to the front door of the main building, for these were the steps Rocky Balboa used to prove his fitness in Rocky, the Best Picture Acadamy Award winner of 1976. Here's a link to a YouTube version of the inspirational scene. You know you like it!

As I began the short run to the museum, I readied myself for the ridicule of bystanders. Here would be an adult living out a scene of a 35-year-old film: Heh! Look at that bozo! "Go Rocky!" Heh.

First, the statue. I had to take a photo. There's a long story on the statue, which was commissioned for Rocky III for the top of the steps. Some objected this was inappropriate for a museum, and it was moved away. But popular demand brought it back to the museum, to the side of the bottom of the steps: less intrusive. However, it still attracts a steady stream of tourists taking photos: I was just one of many during my time there. I never saw anyone taking pictures, or even looking at, any of the several other statues on the museum grounds.

Rocky statue

It was time to run the stairs! I felt strangely nervous. What if I couldn't make it? What if I doubled over, out of breath, like the "before" version of Rocky in the film? The horror... And then there was the mockery I was sure to suffer from surrounding tourists. I readied myself to ignore it.

But as I walked over the the center of the bottom of the steps, I was amused to find that several others were already on the steps, all running. And not just running: it was pro-forma upon arriving to the top to raise fists in the air, jumping up and down.

I had no plans for that, so felt safe. And up I went: taking the stairs two at a time, the biggest challenge to me was to not become disoriented and miss-step. This happens to me on stairs: I'm fine at first, but as I proceed, I feel increasingly out-of-phase with the stairs, until I'm fighting just to keep running without tripping.

I hadn't reviewed the video before running, and so had been mistaken that Rocky runs all the way to the museum doors. After the first steps, there's a broad mezzanine around a fountain, then a final short flight of steps to the front doors. This made a better interval for me than to just do the initial set. Yet others around me stopped upon arriving at the mezzanine. But better safe than sorry: I ran the whole way.

After reaching the top, I had a nice view of the city.

view from the museum doors

Once simply wasn't enough! I had to do it again. I decided three would be a good number of reps, then continue with my run. But after three, I reset my goal to five... then eight... then finally ten. After my tenth repetition, which I did single-step instead of double as an experiment, I decided I'd had enough, decended, and then began running along Kelly Drive of Cycling Classic fame. During the entire time I was on the stairs I was never the only one running there: there were a constant stream of runners, most slower, one faster, running the steps. It was incredible.

full step times
Strava times up full steps. It's unclear from data whether slow time on last iteration is due to running steps one at a time or due to fatigue.

I was convinced that surely I'd outrun Rocky. To check, I uploaded my data to Strava for segment timing. To my shock nobody had defined a segment, so I defined two: one to where Rocky stopped, another to the museum door.

So then I timed the videos. I already linked to the original film. I timed him there at close to 13 seconds. I was crushed: my best time via the Strava segment, which starts and finishes on the steps to provide some room for error, is 18 seconds (note only a few of my attempts match the segment, since the stairs are wide relative to the stair length, and I started from various positions). But then there's a sequel where Rocky comes back, now a star, fitter and faster than ever. Here's a link to that sequence. His time there: 10 seconds by my timing. I wasn't even close.

The key is while I took the stairs two at a time, Rocky takes them 4 at a time. Impressive! Obviously I have my work cut out for me if I want to challenge Apollo Creed myself.

Monday, December 19, 2011

San Bruno Hillclimb: Jan 1

It is traditional that the top 3 men, top 3 women, top 3 juniors, and the Endurance Award winner of the Low-Key Hillclimb series are all awarded a free spot in Pen Velo's long-running San Bruno Hill Climb, held every year on Jan 1. I finished 4th, just out of the "money". But yesterday I signed up anyway, paying the entry fee: it's not often I have fitness and opportunity this time of year to do the climb.

The USA Cycling page has it listed as a "time trial", but that's incorrect. It's a mass-start race, riders starting in waves from the base of Guadalupe Canyon Road near Bayshore, climbing to the "saddle point" marking the top of Guadalupe. Then from there it's a sharp right into the state park, down a short descent past the ranger kiosk, an immediate right turn over rough pavement a short straight, another right, pass back under Guadalupe Canyon, then the narrow, sometimes rough climb to the summit. Here's the profile:


The rating listed on the plot uses my algorithm, which is normalized to Old La Honda being 100. The rating is lower because of the relatively lower average grade. However, given the distance, the times aren't that much faster than Old La Honda road, the difference depending on conditions (San Bruno is much more exposed to the wind).

It opens with surprising steepness, then levels out for a traffic light. Past this light (annoying on non-race days when it's too often red) the road climbs somewhat steeply again until the grade lessons, then flattens completely at the Guadalupe Canyon "saddle". Radio Road passes underneath, visible to the right, while to the left is a clear view to the summit. Then comes the tricky bit: the net 270 degree turn onto Radio Road and back under Guadalupe Canyon. You absolutely don't want to fritter away any seconds here, but given the poor road condition, taking a corner too hot is a real danger.

Once under Guadalupe, Radio Road really comes into its own. This climb begins moderately, but it becomes progressively harder to hold onto a gear until at a sweeping left turn the grade hits its peak of almost 10%. Now it's the end game: first a right turn which appears it might be the end, but following that a second sweeping right leading to the finish line at the radio towers (watch out for the 6-inch gap in the metal plates on the road!)

mind the gap

Here's a Strava segment:

As I write this, I'm 18th, a result I got in a training ride on November 13th. I'd like to improve that time on Jan 1. Unfortunately a lot of other riders are also likely to post good times on Jan 1, so if I can just hold my position in the rankings, that wouldn't be too bad! But I think I can reasonably hope to just crack the top 10 when the day is done, conditions permitting.

It's a fun race to watch as well as well as ride. 2007 was an off year for me: I'd ridden well at the Low-Keys in fall 2006, but IEDM and other factors got in the way of me keeping enough fitness to make riding San Bruno worthwhile. Instead I took photos. Here's spectators near the summit watching riders pass below:

spectators at San Bruno

The view of Guadalupe Canyon Road below is nice:


Here come the leaders! It's newbie Chris Phipps leading hillclimbing Low-Keyer Tracy Colwell! San Francisco is in the background. Chris would go on to take the win.


The next year, after I had done the Youth Hostels International "Christmas" bike tour out of San Diego, returning the day before, and was tired but at least had some fitness. So I gave it a shot. I did not ride a smart race. Here's the results.

On Guadalupe Canyon, I resisted the surge of riders near the front, preferring to ride a steady power the whole climb. This works for a climb which is a steady grade in consistent conditions, but San Bruno has neither. First there's the false flat where being in a pack is a benefit, so the faster lead group will gain time on slower trailing groups. Then there's a chance to recover on the descent and turn, so it pays to be slightly in the red going into this section. The worst part was the wind: it was a strong head wind on Radio Road that year and so whatever group you were in, you stayed in. Bridging gaps was extremely hard. The real race was to the park entrance, and I arrived there with way too much left in the tank.

In 2009 I was in Southeast Asia. But this video shows conditions aren't always ideal on San Bruno mountain:

San Bruno Hillclimb 2009 from Chris Stastny on Vimeo.

2010 I missed as well (more focused on running, and the forecast had been for rain), then in 2011 I was woefully out of shape due to 11 hours days at work at my then-new job.

But back to 2012....

As I noted, it's tough coming into Jan 1 ready to go. As is the case most years, this year I'm traveling to the east coast to visit family for Christmas week, during which time I won't have a bicycle. I'll probably run a bit and go to a YMCA or other local gym where I will ride a stationary bike and do some light lifting and core work. Hopefully things go well.

Thursday, December 15, 2011

Fairwheel Bike's Project Right @ NAHBBS in March

I'm very excited about the 2012 North American Handbuilt Bicycle Show in the first weekend in March. (I was tempted to ride the Death Valley Double Century, but the two conflict.... Death Valley can wait.)

Fairwheel Bikes, which has been stealing a lot of attention from the big boys at Interbike the past few years with their ultra-light project bikes, is delivering a new project to the show: "Project Right". I just came across this today, having seen their latest blog update. Here's the frame:

Check that out: the left side of the rear triangle is completely missing, and there's no seat stays. This is really only an incremental change from the trend taken by Cervelo and Pinarello. Cervelo reduced the seat stays to mere formalities to provide vertical compliance, while Pinarello has been a leader (in marketing at least) in focusing material on the right chainstay, since that's the side where force is transmitted via the drivetrain.

Here's the Cervelo R5 in its most expensive form (the R5-Ca). As an aside, I finally came across one of these "in the wild", on the bike path in Sausalito. It looked really nice. I've stopped obsessing over how outrageously expensive it is. If people want to squander money, bikes is a fairly harmless way to do it. Anyway, notice the super-skinny seatstays:

You may as well cut those out: they're hardly providing structural support.

So that's what Fairwheel is doing: no seatstays, only one chainstay. Seems like a progression of a trend. But it's hardly new.

Chris Boardman's Lotus Superbike had a similar concept:

Nothing of interest on the left side; all support for the rear wheel is on the right. This bike was based on the Windcheetah, which Mike Burrows designed in 1982:

But the idea goes way, way further back than that. Documented by Jan Heine in his book, The Competition Bicycle, here's a Labor bike from 1906:

The design was to allow for quick wheel changes.

I really look forward to seeing the Fairwheel Bikes project "in the flesh" at the Hand Built Bike Show.

Monday, December 12, 2011

Old La Honda Road: another PR

I had a good year at the Low-Key Hillclimbs this year. Often by the time October rolls around fatigue from the year is starting to kick it. Last year I came into the series fairly fresh and fit, but then started a new job and my fitness went straight downhill from week 3 (my first) onward.

I finally started exercising at a reasonable rate again in April this year, a mixture of running and some cycling (mostly long commutes to work), and surprised myself with a sub-1:31 half marathon in August: I considered that good given my lack of formal running background. So I knew I had some fitness but wasn't sure about how I'd do on the bike. I did a few climbs of Diablo before the series, just to get some climbing legs, and was surprised my times weren't so bad. But for the Low-Keys, you've got to be better than "not so bad". Everyone seems to raise their game for the series.

But despite my worries I did pretty well. So as the series wound down, Tim Clark asked me if I was going to try for an Old La Honda time. Old La Honda is, to me, the most prestigious climb for times. More riders know their Old La Honda times than any other.

I've been adding some volume to rebuilt my aerobic base prior to the San Bruno Hillclimb on the New Year: during the series it was more about working hard Saturday to Tuesday then being fresh for Saturday.

So I got in some solid work Thanksgiving weekend, then the following weekend. I was pretty tired on Monday, so went super-light on my usual Monday weight room workout. Tue I felt a bit better, but a work meeting kept me from either riding in or riding at lunch. So I was starting to feel fresh again Tuesday night: a good change to give Old La Honda a shot on the Wednesday noon ride. It wasn't optimal: a few days of light work following my recovery would have been better. But I valued the chance to ride with the group rather than try a solo effort.

My last PR attempt on Old La Honda had been successful: in July 2009 I had set out to break 17 minutes and was delighted with my result, 16:49. It was a redemption against having failed miserably at the Diamond Valley Road Race the weekend before, where failing to follow through on my previous two strong races there, I'd been dropped on the first lap. For that attempt I'd ridden a very steady pace, turning my 36-18 gear until near the top, where I upshifted to my 17-cog.

It might seem surprising I'd not tried again. But a good run at Old La Honda requires that I be fit and rested, and that I'm willing to bring my Fuji with its climbing wheels on the train. The key thing here is fit and rested. Devoting a three o r four day block to a good Old La Honda time is a luxury in which I rarely indulge. So most of my rides up the hill are for training only, typically on my Ritchey Breakaway with clincher wheels, carrying water bottles, a heavy tool bag, and a pump. Almost always I've I'd done some sort of hard ride the day before, as well.

So I risked bringing my Fuji SL/1 with it's light wheels and 180 gram Vittoria Corsa time trial tubulars on the morning train and from there to work. At lunch, I met Mark Johnson and we rode along glass-strewn Central Expressway on our way to the ride start: a serious risk for the ultra-thin tires and no spare. But we made it, and I felt fairly good.

Doing good OLH's from the Wed Noon Ride used to be compromised by a fast pace over Arastradero and Alpine Road, then jamming to the sprint at Woodside. But no longer: the focus is now, thanks to Matt Allie's leadership, strictly on the climb. So the ride to the base is at a nice warm-up pace.

Conditions were fairly good for the attempt. The road is in historically good condition, most notably the upper portion which was repaved within the past few months. And winds were forecast to be light, from the north, a tailwind (winds are generally blocked by the trees on the climb, but every little bit helps). Cool temperatures had me carrying more weight in clothing than I'd prefer, but as we approached the climb and were stopped by construction crews on Portola Valley Road, Peter Tapscott offered to carry my jacket and empty water bottle for me. My excess mass was in my long-sleeve undershirt, my heavy long-fingered gloves, my compression tights, additional calf compression socks,and the wristwatch I'd forgotten to remove before leaving my office. All of this adds up, probably worth 2-3 seconds on the climb, the wind resistance from the gloves maybe an additional second. But I couldn't pick the weather and I wasn't going to help myself by under-dressing. Some recent emergency repairs to my bike due to a broken Power-Cordz added some additional weight: at least another second there. It all adds up.

As we hit the base of Old La Honda I made a tactical error. My plan had been to start a bit back, then move up to the early pace-setters, essentially shaving a second or two. But this back-fired, as nobody took control of the pace, and I was stuck in traffic. I went to the extreme left of the road, moved up, and went to the front myself. Not the best way to start: I should have hit the bridge marking the start of the climb at speed and carried momentum up the initial slope.

I was joined by Chris Zappala, who'd mentioned he'd commuted to Palo Alto from San Francisco earlier that morning. Despite the hard ride in the cold, he was ready to ride, so I got on his wheel for early pacing. As I climbed I looked down at my cassette to assess my gear. I had a 12-23 cassette, so tried to count the number of cogs between the chain and the end of the cassette and figure out which gear it was. Was it 17 or 18? It felt as if we were going fast, in either case, but I doubted if I was spinning the 17 that I would be able to sustain that pace.

I came across James Porter and Greg McQuaid climbing together. I'd expected them on the noon ride itself but they'd clearly decided to leave early on their own. Tim Clark was going to be with him but I didn't see him. Greg was recovering from a broken collar bone so I didn't expect him to be in top fitness right now, so I focused instead on riding with Chris.

Chris eventually faded, as expected given his morning commute, and I moved ahead. I hit the first mailboxes in 5:50-something, the fastest I'd ever done. That didn't seem to necessarily be a good thing. Then I noticed that I was indeed in my 17 cog, so downshifted to the 18. This put me back to where I wanted to be, gear-wise, but not where I wanted to be feel-wise. I was becoming distressed, struggling to maintain pace through the steeper corners, and there was still a long way to go. In 2009 I'd still be climbing seemingly effortless at this point.

I came upon Tim Clark, whom I was able to catch. For awhile he served as a nice rabbit, but eventually I caught him and he cheered me on as I passed. But I was feeling a growing sense of despair. I tried to suppress all negative thoughts, to simply push onward, but I couldn't deny that I was struggling.

I shifted down into my 19.

Now it was official: I'd gone from "get back onto pace" to "minimize losses". Sub-17 was still possible, I told myself, keep up the pressure, don't let up. Even if I were to miss 16:49, I still wanted to make Strava page 1, which required 17:08. This was no time to indulge in self-pity!

I looked down at my computer and saw 16-even with a few turns left. I knew that these turns always eat up way more time than expected: it always seems time accelerates here. But I kept pushing, all hope of smooth form now gone.

There it was: the mailboxes, then the stop sign. As I approached I looked again at my computer, the first time since I'd seen 16. 16:35 it said just as I went to hit the lap button at the stop sign. I'd done it: a new PR. Official time (from the Garmin) = 16:36.31.

It was with interest that I uploaded the data from the Garmin, and sure enough, the numbers tell me what I already knew from my gear selection: I faded.

To generate this plot I differentiated my altitude versus time, then applied a bi-exponential convolution with a 5-second time constant to smooth the data. To avoid issues with the smoothing at the beginning and end, I excluded the first and the final 500 meters. This generated the data with the red points. I then did a non-linear regression, fitting a decaying exponential to the result (the exponential versus distance, as opposed to time, but the two yield essentially equivalent results). This fitted function is plotted with the dashed curve. On the left of the plot is the rate of ascent represented as meters/hour ("VAM"). On the right I show the projected Old La Honda time for each VAM. The green background is sufficient to break my previous PR of 16:49. Red implies I'm losing ground versus that result.

You can see I obviously started way too fast: a 15-minute Old La Honda pace. Some people can do that (Ryan Sherlock beat 15 minutes the weekend before my ride, although Eric Wohlberg has the unofficial self-timed record at 13:50). I cannot. So as the climb progresses, the trend line has my climbing rate decrease at 3.4% per kilometer. Finally at around 4.5 km I crack fairly badly, my pace dropping even below this decaying trend. But I rallied toward the finish and regained some of that lost time.

Honestly: if I'd known my pace was going to be this far from uniform, I'd have said no way would I have been successful. But I was successful, which tells me that I am able to go out fairly hard, too hard, and still retain enough to do well for this interval. This is important for the San Bruno Hillclimb on 1 Jan, where there are considerable draft advantages for staying with a pack near the beginning, and given my experience here, it seems I can afford to go into the red to hold onto early wheels there. San Bruno is a relatively tactical climb, as there's an unavoidable recovery half-way as the route descends and turns under the main road on which it begins. Then from there the winds can make it very difficult to bridge gaps which may have formed on the first portion. So holding onto a good group is really important.

Anyway, it will be fun to see how it goes. I'm hoping for good weather on Jan 1.

Monday, December 5, 2011

Level of Service Analysis and Bus Rapid Transit

Here's a good story: from the excellent StreetsBlog San Francisco, What's the Hold Up for Van Ness BRT?.

San Francisco has no meaningful intra-city subway, and most of the street car lines were ripped out early in the 20th century. Street cars were mostly privately owned, and they couldn't compete with the massive public support provided to car infrastructure under political pressure from the car companies. So en masse, street lines were paved over, except for a skeletal few: there's a few key MUNI lines, and a few cable car lines which cater to tourists. BART runs through downtown, but just makes a few stops in the city, designed primarily to connect San Francisco to the East Bay. It's original goal of surrounding the Bay was gutted by first Santa Clara County opting out in 1957, then San Mateo County in 1961, each preferring to focus on expressways; Marin dropped out soon after [Wikipedia] (what an unbelievable tragedy).

So San Francisco is stuck with buses for the vast majority of its area as public transit. Yet despite being carless, I take the bus only a few times a year. Why? Because it's increadibly slow and unreliable. If I decide now I want to get somewhere, more often than not I can actually run to a destination before I'd arrive by bus. It wouldn't be uncommon that I could arrive at my destination before I'd even stepped on the bus, since delays of up to 40 minutes for the next bus are not at all uncommon with buses running on a nominal 20 minute interval. Even with an even start I can often outpace the bus by foot. And by bike it's simply no contest.

So San Francisco proposes to give buses priority lanes. This is called "Bus Rapid Transit", the idea being to package bus lines like more expensive "light rail". You step on the bus, it zips down its own lane triggering traffic lights as it goes, and presto-magicko, you're at your destination in no time. Awesome! Public transit problem solved!

Streetsblog image: BRT Geary
BRT Geary (Streetsblog San Francisco)

Solved, except that infrastructure projects must go through environmental impact analysis (CEQA) and a big part of environmental impact analysis is the effect on automobile traffic. This makes sense since automobiles are responsible for an enormous environmental impact: noise, pollution, resource depletion, and public safety. No brainer in this case, right? After all, an efficient bus line will take drivers off the roads by providing a timely, more efficient alternative, reducing the environmental impact of cars! No-brainer, let's go!

But wait! CEQA uses an analysis based on a fixed "level of service" (LOS). The assumption is a certain number of cars will use the road each day, and if you slow these cars down, they'll generate more congestion, their engines idling all the while. With this logic, the more car lanes, the better, as the fixed number of cars on the road will then zip to their destinations with a minimum of "impact".

This is obviously absurd. Build more lanes, more people drive, those who drive drive more often, and when they drive they drive further. This is seen time and time again in the data, in study after study. Cara was in Amsterdam recently, reporting on the enormous number of cyclists using the bike paths, cycling providing clearly superior local transport the cars, which are relegated to narrow roadways. There's a nice video here.

The LOS logic? Pave over the bike lanes: extend the roads by adding lanes. This will have the cars generate less exhaust during their trips. Sure, bike riders will be slowed as they struggle to find space on the public roads, but there's not much environmental impact from a slow-moving bike, while slow-moving cars are spitting out exhaust fumes and making noise every extra second of their trip.

I'm sure the Dutch would laugh with well-deserved contempt at this stupid demonstration of the pathetic state of U.S. public education were we to suggest this to them. And they'd have a point.

The problem with the LOS standard has been well known in San Francisco since the 2006 injunction against all new bike infrastructure in San Francisco, an injunction which was lifted only last year. The bike program, it was decided, needed to provide an environmental impact analysis, and analysis which was not able to claim that if you make a city better for cyclists maybe, just maybe people would replace car trips with bike trips, reducing the need for car lanes. The bike program was eventually able to survive even that silly standard, and is progressing well today due to the unrelenting political pressure of the San Francisco Bike Coalition. We can only hope BRT is able to get past the LOS hurdle as well, and even better that the LOS standard be quickly and definitively revised to recognize that driving a car a certain number of times each day is not an inevitable fate.

Sunday, December 4, 2011

Strava power estimation: Cortland Hurl

The Cortland Hurl is the only significant climb on the SF2G Bayway route. According to Strava, it gains 25 meters in 400 meters, an average grade of 6.3%, although the grade is non-uniform. It starts out fairly gradual, then steepens, then gets gradual again towards the top. I like to make a good effort here when I'm feeling good during morning commutes. Typically I'm behind at the top of the steep bit, but I tend to do fairly well on the final gradual portion. If I'm having a good day, depending on who's there and how they're riding, I have a chance to be first to the top.

I've not ridden with a power meter for a year now. I sort of lost interest: I just like riding my bike and I don't care what the power meter data are, so why carry around a heavy, expensive Powertap wheel? Strava gives me a fairly good idea how I'm doing with its segment timings.

However, in addition to speed numbers Strava also produces power estimates. In fact, it will use these estimates for reporting a rider's best effort over different time intervals. I have suggested to them this is a mistake: only power meter numbers should be used for this purpose, since their estimate is unreliable.

Since I had a lot of data for Cortland (28 rides + one I reject because I dropped my keys along the way and had to turn back to fetch them), I figured it would be interesting to compare Strava power to PowerTap power, plotted versus VAM which is considered a decent surrogate for power/mass ratio on climbs. I also compare these with "hand calculations" using the usual power-speed model. Here's the result:


The analytic calculations assume constant speed and constant grade and no net acceleration. Assuming start and finish speed are the same, they are thus a lower bound estimate given the assumptions used. For assumptions, I show three. One is using a "realistic" estimate for total mass and for CdA, the coefficient for wind resistance power. For this one I set my body mass to 57 kg, my bike mass to 8 kg, but then added in 4 kg for equipment and clothing and what I was carrying on my back. I assume a 0.5% coefficient of rolling resistance. CdA was set to 0.5 meters squared. For a second estimate, I eliminated the clothing + equipment mass and reduce CdA to 0.4 meters squared, assuming no back pack. In a final estimate I eliminate all wind resistance.

As can be seen in the plot, the Powertap measurements are almost always more than the Strava estimates. Strava estimates start out fairly well aligned with the zero-equipment-mass ("naked") estimate of power, except for my fastest runs where the Strava estimates become much lower, dropping as low as the zero-wind-resistance estimates. There's a few Strava estimates which are clearly anomalously low.

The Powertap data fall above even my highest analytic power estimate. This is as they should, since as I noted my analytic estimate assumed uniform speed and grade, and thus underestimate wind resistance near the beginning and end of the segment. Wind resistance is superlinear, so underestimates during faster than average portions are of a lower magnitude than overestimates during slower than average portions.

So what do I learn from this? Basically you shouldn't trust Strava power estimates. But if you do care about them, you should make sure clothing + equipment mass is included in bike mass. I had not done this. It all adds up: toolbag, pump, water bottles, clothing, shoes, helmet: you'd probably be surprised at the result if you bundled it all up and put it on a scale.