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May
17
comment Trainers: Fluid or Mag
Here's an example: I just hopped on my CycleTek fluid trainer with my Power Tap-equipped bike. The trainer can handle 1000 watts but in my highest gear ratio (52x12) at 60 rpm my wheel speed was only ~31 km/h, and the trainer could only produce about 300 watts of resistance at that wheel speed. I would need a higher gear ratio to produce "high intensity" power at low cadence. The alternative, of course, is not to do this at low cadence. Many fluid trainers can produce adequate load if the wheel speed is high enough. That means high power at high cadence.
May
17
comment Trainers: Fluid or Mag
Right, the issue isn't whether there are trainers (either magnetic or fluid) that can create enough load -- the issue is whether they can create enough load at low rpm. "High intensity" usually means "sprint intervals" which are supra-VO2Max. In a sprint interval on the road your cadence is typically up around 120 rpm or higher and you're using a relatively low gear to accelerate up to speed. On a trainer the roller speed will need to be high, so you'll need to use a higher gear. You'll need an even higher gear still to do this at low rpm.
May
17
comment Trainers: Fluid or Mag
OK, thanks. The short answer is you're going to have a hard time finding a fluid trainer that will provide that kind of load at low rpm (and you won't be able to find a magnetic trainer that can provide that load at all). I'll do the calculations and provide a more complete answer tomorrow -- unless someone else wants to do the calculations and write-up and I'll upvote that.
May
17
comment Trainers: Fluid or Mag
Also, in order to give a good answer to your question, it would be good to know what speed you can maintain when climbing, the slope of that hill, your cadence on that hill, and your total weight. Knowing those things will help to determine whether a fluid (or magnetic) trainer can provide the appropriate load.
May
17
comment Trainers: Fluid or Mag
I haven't looked at the specifics of the TCT high intensity low rpm workout. How high is high intensity, how is it measured, and how low is the rpm?
May
15
comment Does Bike or Rider Weight / Groupset affect cruising speed on the flat
How are your watts being measured? And, the guy who claimed to be able to cruise at 30mph at 250 watts must not be riding a bike like yours -- that would imply very low rolling resistance and a CdA of around .145 m^2, which is lower than most unfaired recumbents and in the range of several faired recumbents.
Apr
23
comment When Mark Cavendish says he's sprints at 1500 watts how long is that for?
Cavendish is listed as 69 kg so it couldn't possibly be 30 seconds -- 1580 watts/69 kg = 23 watts/kg, which is twice what world-class riders specializing in track sprints put out. World-class track sprinters can average 23 watts/kg for 5 seconds, but it's much more common that in informal articles like this people (not just Cavendish) are quoting their one second maximum.
Apr
5
comment Headwind when riding in a loop
It's good to be skeptical but decreased drag at non-zero yaw is a fact verifiable both in wind tunnels and on the road -- the only issue is the magnitude of the effect. If you race in events where seconds (or fractions of seconds) separate placements, it certainly can be both relevant and significant; if you don't, it won't be either.
Apr
4
comment Headwind when riding in a loop
By chance, Damon Rinard (who translated the Pivit article referenced above) happened to answer a question about decreasing drag with non-zero yaw earlier today.
Apr
3
comment Headwind when riding in a loop
Effective drag can decrease with non-zero yaw (that is, the effective CdA can decrease). This has been shown not only for components like wheels and frames in wind tunnels but also for riders on complete bikes. That said, this is a small effect and it depends on the yaw angle (which depends on the loop, the rider's speed, and the the wind speed and direction) so from a practical perspective it's rarely important. I've upvoted your answer because it addresses the OP's direct question -- I was only mentioning this for completeness' sake.
Apr
3
comment Headwind when riding in a loop
This is a good and conventional answer but incomplete. The fuller answer, which may not be what the original questioner intended, depends on the the shape of the loop and how the rider's aero drag varies with yaw angle. Imagine a loop shaped like a triangle, with two outbound legs heading upwind but not straight upwind, and the inbound leg heading straight downwind. Now, add this twist: at non-zero yaw, some (but not all!) bikes/riders experience lower drag than at zero yaw. That is, they "sail." In this case, they can go faster on the loop with some wind than in a calm.
Mar
29
comment hill climb tt pacing strategy for short steep hills?
Well, first, bicycles.stackexchange prefers questions that can be answered, not just discussed; but, second, I try to know and do as little training as possible. Coaches and racers do ask me for advice and information but not about training.
Mar
29
comment hill climb tt pacing strategy for short steep hills?
A second issue is how the OP measured his power: with an on-bike power meter on hills, or indoors. Estimates of what he can sustain for X minutes can differ depending on how it was measured and the grade he tested on, especially when the anaerobic component is large.
Mar
29
comment hill climb tt pacing strategy for short steep hills?
Constant power output is time-minimizing only when the conditions are constant. If the slope varies (or the wind blows differently on different parts of the course) the time-minimizing strategy is to vary power. The optimization problem is finding a (varying) pacing strategy that gets you to the top of the hill in the shortest time while meeting constraints on energy expenditure. That's a difficult and interesting problem, particularly when the durations are so short and the work rate will be above VO2Max.
Mar
17
comment Why do some triathlon seatposts go straight up and down instead of at an angle?
Nice answer. As you no doubt know, that slowtwitch.com article was written by Dan Empfield.
Mar
16
comment Why do some triathlon seatposts go straight up and down instead of at an angle?
I view it differently, but I don't have a problem with your answer. Vertical seatposts and steep geometry are a frame response to the desire to get as far forward as possible. The UCI imposed that rule to prevent even more forward frame designs. The vertical seatposts we see today are just a point along a continuum. In a completely aero-focused world frame designs would be even more radical. There's nothing magic about vertical.
Mar
16
comment Why do some triathlon seatposts go straight up and down instead of at an angle?
Nice. You might want to add something about the 5cm setback rule -- it shows that riders would want to go even farther forward if they were allowed to.
Mar
15
comment Why do some triathlon seatposts go straight up and down instead of at an angle?
I don't have time to give a full answer to this question, but it's because TT and Tri bikes have a steeper seat angle than road bikes. This is a side-effect of aerobars, which are used on TT and Tri bikes. You can get more info from this interview with Dan Empfield, the primary inventor of the Tri-specific bike here. It would be good if you would summarize the article and submit the answer to your own question.
Mar
7
comment Any experience with shaft driven bikes?
Although you can't change the gearing from the drive itself, there are internally-geared hubs that are compatible with shaft drives.
Feb
26
comment Advantages and Disadvantages of Bar light vs headlight.
I believe this is closely related to this question: bicycles.stackexchange.com/questions/8781/…