% increases in power required to improve average TT speed

robkit

my point of view at the moment is that i'd rather ride everything on my standard road setup than choose all the aero kit for time trials. main reasons:

- quite a way from being "top 5" competitive in time trials, so I figure whats the point of worrying about the aero advantages needed to win when my purpose of riding TT's is currently more for road training
- some years ago i went under the hour for 25 miles using a low profile bike, almost boardman-like flat back (benefit of having no belly as a junior!), aero hat, skinsuit, aero wheels, etc. My fitness was mediocre, in fact with hindsight it's like I was cheating compared to the effort required now on a road setup.
- Catching someone in a TT is always a satisfying moment, but I just LOVE the look on peoples faces when you come past them on the drops of a road bike with a nice draggy vented helment as well (apparently boardman discovered this was worth 20 watts over no helmet at hour record pace).

i seem to need about 260 watts to do 23mph in this arrangement. wish i could comment about 25mph, but my fitness isnt there yet and i'm estimating a hike of 50 watts!

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acoggan

Never seen a hooker? My, what a sheltered life you've led!

In addition to frames and forks, Hooker made many proprietary parts, including an aero seatpost, aero brakes, aero stem or one-piece handlebars, as well as an ultra-narrow (60 vs. standard 100 mm) front hub that attached to their fork via a recessed Allen bolt (i.e., no quick release lever sticking out in the wind). Unfortunately, like many bike part manufacturers here in the US at the time (late '90's), they relied upon CNC machining of raw aluminum, rather than forging the parts. The result was a high failure rate - in particular, the hubs tended to crack across the flanges between the spoke holes. Since they got out of the bike business after only a year or so, replacements were practically impossible to come by...thus, when I was down to my last hub (I started w/ a training wheel and a race wheel, then luckily was able to get a blank, unpolished hub shell from a teammate who used to work for Hooker), I decided it was time to retire the bike and move on to something a little more practical.

velomanct

today i rode some flat stretches. took me 320watts to go 24mph. and 260watts to go 22mph. this is with hand on the hoods, no aero gear. perhaps my powermeter is misreading?

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Mansmind

unless you're riding with a parachute behind you

it may be, sounds like a logical place to look.

velomanct

Okay, I just did a hillclimb, which is very steady grade straight road for 1 mile. using analyticcycling.com and topozone.com (to determine exact average % grade), I plugged in all my numbers.
10% grade, 90kg total weight, 5 m/s equals 485 watts
at this speed, which I held steady for a good portion of the climb, my average watts were 457. I think it matches up very well if you factor in error, for example I can't ride a 100% straight line for 2 minutes up a climb.

conclusion - powermeter is accurate. end of story.

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wilmar13

Ok having just read this thread, I have to side with VelomanCT based on my own experiences. I am 1.93M (6'4") and 90Kg (197lbs) but there is no way I can go 25mph on a flat with no wind at even 300watts no matter how aero I am. Since I don't ride on a track, there is no way to make an apples to apples comparison, but usually my rides (with lots of climbing though) end up being in the 20-23mph avg with avg power output at 290-350 watts. Generally with no wind riding on the drops, I need about 380 watts to go 25 mph...yeah this is a std. road bike with swiss cheese helmet and non-aero wheels, but...

With all the talk about CdA as a function of height and body weight I wonder if everyone is thinking about the one thing that you can't control on a standard bicycle (legs). I mean, yeah you can work on your upper body form, etc. to improve it, but you can do nothing about the frontal area of your legs unless you are on a recumbant. Maybe VelomanCT has long legs and that is a major reason for the differences? Am I way off on this?

mises

You could use a lower BB bike which would reduce the total frontal area of the bike/rider. Might save 2 or 3 watts. ;-)

Mansmind

I've wondered about this myself, but outside of keeping your kneeds relatively close to the top tube, I'm not sure how much one person can gain over another. Good point though.

Hard for me to compare to the other numbers you mention, I'm apparently not nearly as powerful. One of the normal 20 milers I ride requires 270 watts average to ride at ~18 mph. There's about 1000 ft. of climbing in that particular out & back so there's nothing level about it.

I have very little "flat" area to ride in around here, and what little I have suggests ittakes me a lot less than that to ride at 23-24 mph (245 watts or so).

This is an interesting topic.

Mansmind

I've done the same thing before (to check my power meter). The last time I rode this particular hill at 4.5 ms. It's 9%, 92 kg total weight, which gives me ~400 watts using their calculators. The average on my meter for that particular climb was about 10 watts higher than that as I recall.

wilmar13

Nah I don't think so, unless you radically change the geometry of the bike your legs extend the same amount relative to the wind either way...

wilmar13

I have never seen anything that was truely flat and windless... I always considered a flat windless road to be analogous to the fountain of youth...



Just for clarity, I wasn't suggesting it had anything to do with form, the opposite actually. I was saying that the frontal area of your legs can't really be changed with a std. bike, so if your legs have more frontal area (long or wide or combination) than the next guy of same height and weight and aero position (Cd) you are stuck with with more drag all else equal and will need to make more power to overcome it.

velomanct

I got some pics of me racing yesterday. You can clearly see that I am bigger than everyone else around me. Just by looking at this pic, you can understand why it takes me considerably more power to go at X speed than most other riders. I'm on the red cdale, yellow/purple jersey.

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ric_stern/RST

just because you're big doesn't mean you can't be more aero, as some of the other posters have said.

ric

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Woofer

Your arms *can* shelter some of your legs.

I only do one or two time trials a year so I am not an expert.

I am about 172 cm tall, weight 71 kg +-1 kg and did a flattish time trial this weekend on a pursuit bike averaging 24.5 miles per hour with an average wattage of 235 at the cranks. YMMV.