Wednesday, May 27, 2015

Effect of variability in rolling resistance coefficient on cycling power

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 variability in the coefficient of rolling resistance, by a given fractional amount, can be written almost by inspection by swapping rolling resistance and grade in the previous formula:


ΔP/P = 3 (σCRR / CRR)2 × αwCRR (1 - αw) / (1 + 2 αw) ]2

This will generally be less than the effect of fractional variations in grade, assuming grade is generally larger than CRR.

The definitions are the same as last time:

parameterunitsformuladescription
fmacceleration(grade + CRR)×gravitymass (and speed)-proportional power
fwmass/distance1/2 ρCDA2speed-cubed-proportional power
CRR1coefficient of rolling resistance (for example 0.4%)
CD1coefficient of wind resistance (for example 80%)
ρmass/volumemass-density of air (for example 1.1 kg/m3)
Aareaeffective cross-sectional area of bike + rider (for example 0.4 meters2)
αRR1CRR/(CRR + grade)fraction of mass-proportional power due to rolling resistance
αw11 / (1 + fmm / fws2)fraction of power due to wind resistance
αm11 / (1 + fws2 / fmm)fraction of power due to mass-proportional power

Monday, May 25, 2015

Grade variability and climbing power

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 decreases in speed. So if instead of maintaining a constant speed v, if instead I am v + Δv for half the climbing time, then v - Δv for the 2nd half of the climbing time, the average wind resistance power is increased, assuming still air and no drafting:


[ (v + Δv)3 + (v - Δv)3 ] / 2 - v3 =
[ v3 + 3 v2Δv + 3 v (Δv)2 + (Δv)3 - 3 v2Δv + 3 v (Δv)2 - Δv3 ] / 2 - v3 =
3 v (Δv)2

So the fractional increase in wind resistance power from grade variability, for a given average speed, is:


ΔPw/Pw = 3 (Δv)2 / v2

Note this is just the aerodynamic portion of the power.

This is very simple, but it's in terms of speed, not grade. You can ride a variable grade at a constant speed, and in this case the average power will be calculated using the average grade as is typically done. However, this would result in a variable power, and according to Coggan's normalized power approach this would result in a lower power than could be attained by riding at a constant power, going faster on the flatter portions and slower on the steeper portions. Indeed, I think it's clear that this is almost always done. Essentially nobody rides climbs at constant speed.

So I need a relationship between grade and speed. The key here is that I neglect inertia, which tends to make speed more constant than otherwise. But inertia is only sustained over short distances, so I'm assuming grade variations to a resolution of no better than 10 meters distance or so.

Speed versus grade is a nonlinear problem: a cubic equation. So to estimate this effect you use linear analysis: linearize the nonlinear function.

Back in 2009 I analyzed the effect of grade on VAM, and a part of that calculation was the effect of grade on speed. This calculation begins with the following approximation for power, which is fairly standard in still air:

P = fm m s + fw s3

where fw is the coefficient of power on speed-cubed, fm is the coefficient of power on mass (gravity times rolling resistance coefficient plus grade), m is mass, and s is speed. It's not hard to go from this equation to the following using the chain rule:

∂s / ∂grade = ‒ m s g / (fm m + 3 fw s²)

where fm = ( grade + CRR ) × g, where grade is the road grade, CRR is the coefficient of rolling resistance, and g is the acceleration of gravity (not to be confused with road grade).

The result of this is if there is a variation in grade σ2grade, there will be a corresponding variation in speed σ2s:


σ2s = σ2grade × [m s g / (fm m + 3 fw s²) ]2

So the result is, recognizing that the average value of (Δv)2 ≡ σ2s:


ΔPw/Pw = 3 σ2grade × [m g / (fm m + 3 fw s2) ]2

This equation has too many constants and it's hard to get a grasp for what it means. However, if I define mass-proportional and wind-resistance unitless fractions of retarding force (and of power) αm (mass-proportional) and αw (wind resistance proportional), then I can write this as follows:


ΔPw/Pw = 3 σ2grade × [m g s / (αm + 3 αw) P ]2

But αm + αw = 1, so this can be slightly simplified:


ΔPw/Pw = 3 σ2grade × [m g s / (1 + 2 αw) P ]2

given that ΔP = ΔPw, since climbing power depends only on the average VAM (and is insensitive to speed fluctuations while rolling resistance power depends only on the average speed.

Then if I define αCRR is the fraction of the mass (or weight)-proportional power which is due to rolling resistance, I can multiply and divide by grade, then observe the numerator is a power due to grade, and I can simplify it further:


ΔPw/Pw = 3 (σgrade / grade)2 × [ (1 - αCRR) (1 - αw) / (1 + 2 αw) ]2

This is all in unitless quantities and so is easier to grasp. It works for everything except zero or small average grade (for which you should use one of the previous forms).

The nice thing about unitless quantities is they tend to be more universal without requiring specific estimates for a given rider. For example, suppose we're dealing with a grade which varies 20% about the mean (for example, σgrade is 1.4% with a mean grade of 7%), and 15% of the power goes into wind resistance, and rolling resistance coefficient is around 0.4% (so responsible for around 0.4% / (7.0% + 0.4%) ≈ 5% of the mass-proportional power), then I get a 1.5% increase of aerodynamic power relative to the assumption of constant speed.

If I want to convert this to fraction increase in total power, I need to multiply by the fraction of total power which is aerodynamic power:


ΔP/P = ( ΔPw/Pw ) ( Pw / P ) = ( ΔPw/Pw ) αw

I then get:


ΔP/P = 3 (σgrade / grade)2 × αw [ (1 - αCRR) (1 - αw) / (1 + 2 αw) ]2

So going from that 1.5% I need to multiply by my assumed 15% total power from wind resistance and that brings me to 0.23%, so a small fraction of the total.

I think this is a typical example which implies a persistent underestimation of climbing power in time trial like efforts of 0.2% just considering the effect of grade variability. Of course there's other sources of variability which will have similar effect, for example variations in speed due to non-uniform efforts, such as in mass-start races where tactics come into play (going more conservatively at the base of a climb, attacking toward the finish, etc). But the result ends up being fairly minor assuming I didn't make any errors.

An interesting aspect of this formula is that variations in a grade of a given fraction have zero influence in limits both where grade is zero (because fractional variations of near-zero are near-zero) and also in the limit of no wind resistance (because for climbing power variations in speed average out). It's only in the middle range: climbing hills fast enough that wind resistance is still a factor, that the grade variations are significant.

In summary, here's a description of the parameters I used in this analysis:

parameterunitsformuladescription
fmacceleration(grade + CRR)×gravitymass (and speed)-proportional power
fwmass/distance1/2 ρCDA2speed-cubed-proportional power
CRR1coefficient of rolling resistance (for example 0.4%)
CD1coefficient of wind resistance (for example 80%)
ρmass/volumemass-density of air (for example 1.1 kg/m3)
Aareaeffective cross-sectional area of bike + rider (for example 0.4 meters2)
αRR1CRR/(CRR + grade)fraction of mass-proportional power due to rolling resistance
αw11 / (1 + fmm / fws2)fraction of power due to wind resistance
αm11 / (1 + fws2 / fmm)fraction of power due to mass-proportional power

Sunday, May 24, 2015

Team bio passport for pro cycling?

Watching the Astana supremacy in the final kilometers of today's stage at the Giro gave me an idea...

The biopassport is based on the assertion that there is a statistical uncertainty in testing values. But the more data you have, the tighter the bounds which can be set under a given threshold of certainty. If you're examining data from 8 riders in a batch, while any one of them may exhibit variations consistent with normal variation, if they exhibit correlated variations then that becomes less consistent with random chance.

So does it make sense to apply testing protocols to teams as a whole in addition to individual riders? If the team fails analysis while each individual on a team passes, do you eliminate the whole team from the race?

It seems a promising idea. No two-year bans, of course:, that would be unfair to individual riders, but disqualification from a race, at least.

The key is you're introducing an additional source of variation in addition to temporal variation for a given rider: you're adding interpersonal variation. So you can't just average everyone's statistics together. But you can, perhaps, analyze trends in each individual's numbers, and to analyze these variations in a batch.

Maybe I'm being unfair but I'm having difficulty being really interested in this Giro.

Inside Trail Reservoir Dogs 35k report

I had my misgivings about the Ohlone 50k on Sunday, for which I'd registered. I wasn't sure how I was going to get there. I'd tried going down the entry list for other runners who live in San Francisco, checking for them on Strava to see if they lived close, and none did. So I tried to send messages to those I could find on facebook to see if we could coordinate somehow a ride out. But I got only one response, in the negative. He was staying in Pleasanton the night before, relatively close to the "finish" in Del Valle where we were to meet for a shuttle ride to the start of the point-to-point run. Maybe I should try to get a hotel as well, I thought. Then I could ride to the finish on my bike. Or, more fun, I could try camping out in Del Valle. But that involved carrying a tent and sleeping bag and making reservations which probably weren't available still.

It all became irrelvant when I checked the event website to see that the run had in fact been canceled. My first reaction, I have to admit, was relief. It freed me from working out the start line logistics.

But even though I'd been feeling less than excellent from allergies and the after-effects of a steep ramp up in my cycling, I knew I wanted to follow through and do a race during the weeked. The first place I checked, Inside Trail Racing, was hosting the Reservoir Dogs 35k on Saturday. Saturday was a day sooner than I'd planned to run, but the race was 15 km shorter (actually 17 km), and one less day recovery since my hilly ride on Thursday would be compensated by the shorter distance. I'd be okay.

I was by now very comfortable with this distance since I'd done rather well at the Woodside Crossover 35k five weeks prior, and presumably my fitness was a bit higher now. I just needed to treat the race with respect. And that meant eating and drinking far more than I do on training runs, which is none (for eating) and little (for water). I just needed to run a steady, sustainable pace and I should get to the finish.

Logistics were simple: BART to Orinda than an 8 km ride to the boat launch area where registration was held. If anything, it was a suitable warmup for the run. I got there nice and early, right near the opening of registration, and I had no problem getting in.

It was damp, overcast, and cool but these are fine conditions for running. They'd take some of the pressure off hydration and electrolyte consumption. Of course the heat affects everyone and I like to think I take it better than a lot of other runners for a given amount of acclimation but in San Francisco that acclimation is very limited. It's been colder in May than it was any month of the so-called winter.

This was going to be fun. The trails around Briones Reservoir are apparently restricted access so there wouldn't be much opportunity to run these otherwise. And given how nice the bike ride is around the nearby "three bears loop" I expected it to be scenic. And in an understated way this turned out to be accurate.

Being early gave me plenty of time to check out the approach to the finish. There was a gravelly fire road leading to a right turn, then a short steep drop to a very short flat run to the finishing arch. No problems. But I was glad to have seen the turn because under the pressure of a race finish it can be easy to miss something which may be by any reasonable standard completely obvious.

image
Scenic view from Reservoir Dogs (Lets Wander photography)

A key today was going to be to know what I wanted going into rest stops, get what I wanted, and leave with minimal delay. But this would generally include drinking from cups, getting a few salt pills, and eating something like some fruit or some chews. With the rushed plans I didn't have anything on my own. In fact despite including it on my pre-race checklist I recently posted to this blog I'd forgotten to bring Enduralytes, which are a good idea since finding them at the aid station tables can be a time sink. So the focus was on these three things: 1. if I am out of water, hand my water bottle to a volunteer, 2. drink cups of sports drink, 3. get a gel or some chews, maybe with a piece of fruit, 4. take 2 salt pills, 5. get back my water bottle, 6. get out of there.

I was amazed by how few people were there: there had been around 60 for the 35k on the reg list. But in the minutes before the start people showed up. And soon enough it was the usual Inside Trail Racing scene by the start arch.

After a nice speech warning us about a potential cattle drive but saying nothing about bees, it was time to move forward to the start line. I positioned myself in my favorite spot: around 3rd row. This turned out to be good placing. The lead guys shot out quickly, people behind seemed to stay behind, and I was fine running my own pace.

When things had sorted themselves out, my race became a race of 3. First I overtook Madison McCarthy, who, it turned out, was the lead woman, visiting family here from her home in Ashland Oregon. She said she was here with her boyfriend Brett Hornig, who works at Hal Koerner's famous running store there. Brett had signed up for the Ohlone 50k, as had I, and like me had signed up day-of for this race instead. Madison told me they both hoped to win. That was a bit bold, I thought, as I thought perhaps she was slightly underestimating the local runners. But they succeeded: Madison by a comfortable margin, Brett by only 19 seconds.

I followed her for awhile, as her pace was good, but on a climb I felt I could go faster and so went past. I thought maybe that would be the end of it but then I reached the first rest stop.

I like to do quick stops and I felt I succeeded here, but even a quick stop is slower than none, and Madison trotted on by as if the stop weren't there. That was a game I wasn't going to play. So she was gone.

Leaving the first stop, which was the 10 km turn-around, the course did a loop around Briones Reservoir. The half-marathoners would turn around at rest stop 2, but the "35k" runners would circumnavigate the reservoir with a little out-and-back to reach stop 3. So here I was, just running along, trying to not dig myself into any sort of hole, but of course not letting myself slack off enough to get caught from behind,

But after not too long I heard footsteps approaching from behind. Damn. But as the runner passed we started to chat. It was Ron Poggi, who'd just recently run the Boston Marathon. I have a thing for the Boston Marathon and so we talked about that race, about CIM which I've run, and about trail running. This was great because it kept my mind off the distance. It was fun just running and chatting, something I rarely do.

We finally overtook Madison again, and then reached the second stop, the half-marathon turnaround.

Now one thing I didn't mention about this leg was anything about bees. I never saw any bees, never heard any bees, and wasn't stung by any bees. However, the half-marathoners, starting a half hour later, were not so lucky: a hive located right on the trail attacked a substantial number of runners, causing at least one to choose an alternate route back to the start/finish. I later apologized to a finisher from that race for angering the bees.

Reaching the half stop, I again made a decently quick stop, but once again Madison skipped it. Ron was faster than I was, having stopped but only very briefly, but I was able to recatch him. Together we once again reached Madison.

"Are you going to skip all the stops?" I asked?

She confirmed that in fact that was her plan, that she does unsupported 3 hour runs at home, and that she hoped to do the same in this race.

"How much water are you carrying?" I asked. She had a hydration vest, but it didn't look very full.

"24 ounces," she said. 24 ounces? I contemplated the water bottle at my belt. That was probably 18 ounces. But I was supplementing that with cups of Tailwind I drank at the stops -- typically 2-3 per stop, and that bottle was close to empty. I'd refill it at stop 3, then finish that as well.

As I noted, I'm a fan of training on less water than I race. If nothing else it teaches me I can get by without water so when in a race I run out I don't suffer a mental melt-down. The same with food. I know I don't need calories to run 3 hours, but if I do have the calories, that's bonus. So I want to be consuming more in a race than I do in training. And given that, if I'm able to carry enough to last me 3 hours, then I'm carrying too much weight.

Slight digression here. Consider that running is around 1 kcal per kg of total mass. The more the total mass, the more the energy cost of running. But it's not really that simple. Weight affects running's energy cost in multiple ways (see blog post here for analysis). One is the center of mass bouncing up and down, which is affected by the full body weight and all the weight carried on the body (although technically if you carry it in your hand you can isolate it from up-and-down motion). Another source of energy cost is the cost of accelerating your legs and feet each footfall. Weight which is on the feet, for example shoes, is more relevant here. The total energy cost has to be proportional to weight assuming all weight is increased proportionally. But if you increase weight on the upper back, for example, where water is stored, that's going to affect the center of mass motion, but that weight is not being accelerated as the feet are. It will have a reduced effect relative to the average of all mass, which includes the feet. So a 1% increase in mass, if that mass increase is in a relatively inert position, then it will slow less than 1%. I did some calculations on this matter and I concluded that the faster the running cadence, the greater the fraction of energy going into leg accelerations, the lower the fraction going into center-of-mass bouncings. The lowest energy cost came where these were equal. So I'm going to assume a 1% increase in weight is going to slow you 0.5% if it's on the upper back.

She was carrying 24 ounces of water plus a pack which probably had a mass around 200 grams. That's a total of 900 grams. An alternate is a smaller belt pack with half the water but to stop at a rest stop along the way. I'll assume that's 450 grams saved peak. But when running on average the water will be half-full. Instead of 900 grams her pack on average has a mass of 550 grams. So the savings is 275 grams. I'll further assume her mass was around 55 kg. Then the time cost of that extra mass over 3 hours is 27 seconds.

27 seconds is plenty of time to refill a bottle at a rest stop. It might be cutting it close, though. But a key consideration is that there is recovery during this rest. It's what I call "the elasticity of rest". If I hold you up 27 seconds you'll be able to run the rest of the race faster than if you'd not rested for those 27 seconds. But physiologically, at least, it seems unlikely that 27 second stop will result in gaining more than 27 seconds on the rest of the run. You get only a fraction of it back. But you definitely do get a significant fraction because I find I always regain some of the distance I lost in stopping when I leave an aid station relative to runners who run on through. So I suspect you could spend significantly longer, for example up to 45 seconds, at that stop and still do better than running through and carrying the extra water.

But there's an additional effect: which is fatigue. Carrying extra mass causes added fatigue on muscles, both to the legs which need to work harder, and to the shoulders which must support the weight isometrically.

So the end result is: carrying the added weight is worth at least 27 seconds total. When you consider the benefits of the rest gained at the stop and the lower muscular effort associated with running less encumbered, I view the aid station stop a big win. But even more, if I stop at the aid station I'll probably consume more than if I try to do it all while running. That's probably good, too.

So back to the race...

I managed to recatch both Madison and Ron approaching the third stop, which came around kilometer 20. I was first to this stop but then things went terribly wrong. After handing my bottle to the volunteer for refilling, I wanted salt. I looked at various plates with items laid out and didn't see the salt pills. "They're right there!" the volunteer said. I looked and still didn't see them. "There -- in the bottle!" Sure enough the bottle was there, the lid closed off. Okay -- I opened the lid and tried to pour some into my hand. A bunch spilled into my open palm. I put them into my pocket, withdrew my hand, and closed the bottle.

Next I got a slice of watermelon which is always a good option. But I needed to drink.

"Water!" I said to the volunteer, then found the water cups. I grabbed a Tailwind cup, then another, then a third, drinking all of them. The volunteer seemed concerned I was drinking Tailwind rather than water. I'd changed my mind, so assured him Tailwind was fine.

Off I went, Madison and Ron long gone, and to make things work at first I tried to exit in the wrong place, and lost a few more seconds going out through the proper gate. I need to check my data for how long all this took, and in truth it was probably only 2 minutes max, but given I just did an analysis justifying 27 second water stops, 2 minutes is an eternity.

But I was done, and as I ran I decided to try some of those salt pills. But then I noticed my pocket was inverted and the salt pills were nowhere to be seen. My hand had inverted the pocket when I'd withdrawn it. I should have put the pills in the pouch attached to my water belt instead. That's more secure.

Anyway, all I could do was run at my pace, and I hoped to recatch Ron at least, since I suspected Madison was the stronger runner.

On the plus side I was feeling fairly good and could see Ron up ahead when the sight lines were sufficient. At one point I estimated he was 40 seconds ahead and if we were running approximately 300 second kilometers than that put him 130 meters ahead of me. If there were 13 km remaining then I had to go 1% faster, 3 seconds per km, to catch him. I could do that, right?

But rather than close the gap grew. We came to one sweeping open section with long line of sight and ahead I saw a few runners on the trail. I wasn't sure if one was Ron. But I was sure that was a lot more than 130 meters.

On I went, passing close to a cow (fortunately he was a friendly cow). Then reaching a gate which I tried for a few seconds to open, only to realize I was supposed to go around the gate, not through it. If this and the turn-around aid station snafu were the worst navigational issues I had all race, it was navigationally a very successful race.

I knew the last rest stop was the 10 km turn-around, which means 5 km from the finish. So I expected to see it at 30 km on my TomTom watch. But approaching the intersection I approached a runner coming the opposite direction. "A quarter mile to the stop!" he said. Wait... this was less than 28 km.

I ran on. Approaching the stop, I saw first Madison ("go, Dan!") and Ron ("go, Dan!") returning on a trail which paralleled the dirt road I was on. They had a big lead. I wasn't going to catch them.

But that didn't mean I could slack off. I approached the aid station with two things in mind: 1. drink coke, 2. get 2 salt pills. And there I was.

It didn't go as smoothly as I wanted as there was some congestion with a slower half-marathon runner and a volunteer helping him, but I managed to get out there relatively quickly having accomplished my two goals. My water bottle was empty, so I briefly contemplated putting some water in it, but dismissed that due to the congestion. It was only 5 km, and I was well hydrated. Further I didn't drink any Tailwind here. I've learned the hard way sports drink + Coke makes a frothy mix which doesn't sit well.

The Coke kicked in and I was in end game. I passed several slower half marathoners along the way here. The distance passed a lot faster here than it had on the outward leg, when we covered the same trail in the reverse direction. I figured the finish was around 33 km on my watch based on hitting the aid station at around 28, but just in case I was wrong, I held a little back. I looked for the "mile to go" chalk mark I'd seen on the outward leg to be sure.

I never saw that chalk mark, but I reached what I recognized as a grassy trail I'd run on the way out. And then I saw him. It was Ron, up ahead, going slowly.

He heard me coming and picked up the pace. Okay, so this was going to come down to the finish. It's at this point in the race I try to detach myself from my body, to ignore pain. The resolution to pain is to finish sooner, not run slower. So I kept the intensity up.

Then Ron slowed to a walk. I quickly reached him, and as I passed, I shouted "Go, Ron! You're almost there!!!" He mumbled something and I didn't slow down to ask more.

I was on the gravel road now: the finish wasn't far. Then there it was, the right to the short steep descent to the finish. I came upon the rear of a fit-looking guy at the top of the little descent, but he slightly gapped me there. I followed him soon over the line.

Then, all the goodness I was feeling in the end game, all the Coke-and-adrenaline induced rush, left me and I was a quivering mess. But that feeling passes soon enough. I sat down, I ate a few salty-nutty-bars, I ate a few more salty-nutty-bars. Gradually I regained my humanity.

I got a chance to talk to Ron and he said he'd had stomach problems. I smiled a bit at this, not because I like to see other rivals have difficulty, but instead because it justified my approach at stopping at all the aid stations to make sure I had what I needed. The gap to Madison was several minutes, the gap to the runner behind me was 12 minutes. Both of these gaps were significantly larger than even the time I squandered at aid station 3. But in the end it paid off that I never experienced weakness the whole race. And my result was good: 10th out of 60, 1st in age group. Ron was in the next age group up, winning that.

One thing, though, is I probably took too much salt. Enduralytes are low on sodium chloride, but the salt pills they use here are high. This caused me to bloat up a bit in the day after the race. It was cool and I probably didn't need the salt at all, especially since Tailwind has electrolytes. Next time I'll bring Enduralytes to avoid any issues.

Next race: I'm not sure. Maybe the Rodeo Beach Inside Trail racing four weeks after this one. That borders on racing too often but my recovery from this one is going a lot better than from my preceding two races.

Saturday, May 23, 2015

professional cycling doping rumors

I saw this on a favorite cycling forum, where I "redacted" some of the key details.

Spoke to a friend and reliable source, employee of a large pro team. His sentiments about the tweet is that basically everyone agrees with it and openly think that has organized doping going on to some extent and/or still has back channels to Schumi. Also, the common belief is aligned with what Voigt and TSP said in that if the UCI didn't give the license they would have their pants sued off by entities with very deep pockets so they had little choice. A final rumor is that some riders are using new peptides similar to those that were recently banned like GW-501516, a new type of growth hormone and IGF that aren't tested for yet, and various banned anabolics in suspension form during training camps so that the ultra short half-life times won't show up on test results. If the rider were to take the substance right after a ride the glow time would only be around 6-8hrs for a normal dose and thus out of the system by the morning when testers typically show up.

Okay, so this is all just someone's rumor, so take it for what it's worth.

Thursday, May 21, 2015

New Cannondale EVO, CAAD-12, and stack-reach geometry

I heard at the Tour of California that the new Cannondale Evo is basically done, and I further read there's a new version of the CAAD10 which will be called the ... drumroll.... CAAD12. So what about the CAAD11? The answer is they're skipping the CAAD11 to make room for that to be used for the lower-level version of the new bike. If it's like the Evo and CAAD10 the two bikes will be very similar except for that the Evo bike is carbon and the CAAD is aluminum.

I've ridden very few bikes (I always say I want to test bikes but it's surprisingly hard to make time to do this). The Evo is the 2nd to last bike I've test ridden (the latest was the Parlee ESX, the name supposedly short for "Essex". Yeah. Right). Anyway, Evo was a [i]very[/i] nice bike: the handling was spot-on, it felt good, there seemed to be no penalty for its stiffness, and it went against the fatty tube syndrome which had been in full fashion at the time it came out. Fatty tube is alive and well in the Trek Emonda, but I don't like it: it seems overkill for any but the most powerful riders and flaunts wind resistance. Just going to narrower tubes helps there, as well as looking better to my aesthetic.

So what changes do I expect for the new Cannondale?

One obvious potential change is some tube shaping in the style of the Cervelo RCA/R5. Scott did something similar with their Addict, following the Foil which was more overtly aerodynamically tuned. But the Addict took the approach of "we're going to focus on weight, stiffness, comfort, and (new for the Addict) tire clearance but if we can make it more aero we can". Even with this approach, not compromising too much in the other areas, you can make a big difference. The same was true earlier with Cervelo. They have the S-series for aero weenies but that doesn't mean you ignore aerodynamics in the R series.

Another Cervelo thing is stack-reach geometry. Stack-reach design means you start with a stack-reach chart, typically a smooth line or curve, and design bike dimensions to fit on the curve. The traditional approach is to focus on top tube length, then do ad hoc adjustments to head tube length, head tube angle, and seat tube angle to make the top tube length work. But since these changes are typically done un-smoothly, the result can be a rather strange looking stack-reach progression. Here's how Cannondale "stacks up" against some other designs:

stack-reach

You can see all the other bikes here, including of course Cervelo, follow relatively smooth stack-reach curves, while the Cannondale curve is a mess.

So who cares? Indeed, if a given size happens to fit, you care only about that stack-reach. Nobody forces anyone except a sponsored rider to choose a given bike line. Suppose a shoe company sold a shoe and the size 42 tended to run wide but the size 44 ran narrow. Well, you go into the shoe store and try on your size and if it doesn't fit, you try someone else's shoe. Would it be better if both 42 and 44 ran narrow? It would make things simpler, but you happen to have size 42 wide feet that wouldn't do you any favors. But stack-reach design does make sense and I wouldn't be surprised to see Cervelo go there.

Then there's disc brake design Yadda yadda. Call me carmudgeon. Discs are more expensive, heavier, more complicated, and require a stiffer and heavier fork and a heavier front wheel. So I don't care about disc brake designs. My brakes work well enough to send me flying over the bars and I can't brake harder than that.

So these two factors: semi-aero design, and stack-reach geometry, would both show a lot of Cervelo influence. And Cannondale recently hired Damon Rinard from Cervelo. Damon was formerly at Trek around the time they came out with the latest Madone, another stack-reach design with aero emphasis. So if Damon Rinard has any influence I expect Cannondale to follow this path, unless they're too tied to their traditional sizes.

Wednesday, May 20, 2015

sprinter speeds crossing the finish at the final stage of the 2015 Amgen Tour of California

Here's a finish line photo of the final stage of the 2015 Amgen Tour of California:

ATOC photo finish

I love photo finish images because the "x-axis" which is usually position in most photographs, is time instead. There's only one spatial dimension. The camera records a slit image of what is crossing the finish line at a given time. So if you measure the "width" of a bike crossing the line, that's how much time it takes for the bike to cross the line. If I assume all bikes are the same length, then speed is inversely proportional to the amount of time taken to cross the finish.

Here's a typical bike geometry chart, in this case for Trek's racing bikes, which have "H1" and "H2" geometry. Note the wheelbases vary from 97.4 to 101.8 mm, a range of 4.5%.

In contrast the Specialized Tarmac goes from 970 mm to 1013 mm, a very similar range.

Cannondale: 962 mm to 1012 mm.

In all, wheelbases seem to vary by around 5% among bikes across the full size range. To get total bike length you need to add on a wheel diameter, and those are very similar (basically all the pro riders @ ATOC were on similar 25 mm tires. I saw only one team on 23 mm). But the sizes vary less between manufacturers than they do between sizes. So generally larger bikes will have longer wheelbase than smaller bikes.

I counted the number of pixels on the full-resolution image of each rider from the front of his front wheel to the back of his rear wheel. Stage results are here. Here's the pixel counts:

place  rider           team              pixels
1      Mark Cavendish  Etixx-Quickstep   262
2      Wouter Wippert  Drapec            265
3      Peter Sagan     Tinkof-Saxo       251
4      Tyler Farrar    MTN-Quibeka       255
5      Tom Van Asbroek Lotto-Jumbo       266

The interesting thing here is that Mark Cavendish was pretty fast, not the fastest but still pretty fast, despite crossing the line in a very unaerodynamic position: a full victory salute. He'd obviously lost some speed by this point.

But there is the issue of the 5% variation in wheelbase, which is around 13 pixels. That's a big source of uncertainty, although I could correct for it by looking up the specific wheelbase of each rider's model and size of bike. But I can also measure just the front wheel length crossing the finish line. Front tires, as I said, should all be essentially the same size with the standardization to 25 mm tires:

place  rider           team              pixels
1      Mark Cavendish  Etixx-Quickstep   107
2      Wouter Wippert  Drapec            107
3      Peter Sagan     Tinkof-Saxo       102
4      Tyler Farrar    MTN-Quibeka       105
5      Tom Van Asbroek Lotto-Jumbo       ???

The result is similar. Sagan was fastest, Farrar next, and Cavendish and Wippert slower but not as slower as you might expect from the parachute-like victory salute. If he's that fast in the salute, how fast was he going before that?

Here's a video of that sprint from Wouter Wippert's bike cam:

That's simply amazing.