# "The 33"-Road Bike Racing - Speed vs predicted speed given watts

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.

Pages : [1] 2

jmX
10-20-11, 07:54 PM
I did my FTP test on a flat unobstructed 20mile long course (out and back) on smooth pavement at sea level with very light winds today. I'm making progress and all is well.

As somebody who'd like to eventually do the local time trials, my question is more about a curiosity I have wondering why my speed numbers are so much lower than what formulas might predict.

Obviously there are a million variables and I understand equations and their inputs are all approximations, but the data spit out from http://www.analyticcycling.com/ForcesSpeed_Page.html is so far off from my numbers I wonder if I'm missing something. In fact, it estimates I should be able to go the speed I did at 150 watts, which is a huge delta between what I actually put down.

Even if I enter worst case scenario type numbers I can't get the speed that low in the calculator.

The FTP test results:
http://connect.garmin.com/activity/123071041
Avg power was 239w WITH zeros. I'm 6'1"@159lbs. I'm not wearing MC Hammer pants or any baggy clothing. Was in either the drops (5%) or clip-on aerobars (95%). If I ride solely in the drops I'm about 0.5mph slower.

So analytic cycling predicts 24.7mph at 239w, compared to my 20.7mph at 239w. 4mph is a huge difference at these speeds. Anybody have input?

Grumpy McTrumpy
10-20-11, 08:04 PM
I'd say you underestimated the area part of CdA

for me, at 240w with my normal road bike in the drops, I would expect 22ish under those conditions. I assume I am smaller than you.

24.7mph at 239w is something I have only seen on my TT bike with full aero gear. It's a touch on the slow side (maybe half a mph) so I tend to see those numbers on windier days or on courses with slightly more elevation gain.

Nate552
10-20-11, 08:27 PM
I'd say you underestimated the area part of CdA

for me, at 240w with my normal road bike in the drops, I would expect 22ish under those conditions. I assume I am smaller than you.

24.7mph at 239w is something I have only seen on my TT bike with full aero gear. It's a touch on the slow side (maybe half a mph) so I tend to see those numbers on windier days or on courses with slightly more elevation gain.

Agreed. 24.7mph at 239w is pretty dang aero. I'm a tiny guy and get really aero, and for example, on my TT set up I'm at roughly 210 watts to 25+ mph. On a road bike I wouldn't be close to that.

mollusk
10-20-11, 09:17 PM
You could try using this calculator:

http://www.noping.net/english/

hammy56
10-20-11, 09:41 PM
Agreed. 24.7mph at 239w is pretty dang aero. I'm a tiny guy and get really aero, and for example, on my TT set up I'm at roughly 210 watts to 25+ mph. On a road bike I wouldn't be close to that.
pfft.

RChung
10-20-11, 10:01 PM
Anybody have input?
Yup. Either 1) your power meter is off; or 2) you're a parachute. Or maybe both. Check your PM, then check your CdA.

You could try using this calculator:

http://www.noping.net/english/
That thing is terrible.

wanders
10-20-11, 10:56 PM
You could try using this calculator:

http://www.noping.net/english/

That thing is terrible.

I actually comes pretty close for me. +/- .3 mph for the Lowes Motor Speedway TT series.

RChung
10-20-11, 11:27 PM
I actually comes pretty close for me. +/- .3 mph for the Lowes Motor Speedway TT series.
Oh, I didn't mean that it was wrong in an absolute sense. I meant that it's nearly impossible to find the parameters he used to set that thing up, and it's not very flexible in that you can't really customize them. If you happen to be lucky and your CdA and Crr match his models then you're golden, but if you're unlucky the default values can be way off -- and in general, the default parameters for recumbents are optimistic and the parameters for conventional bikes is pessimistic.

jmX
10-20-11, 11:45 PM
the parameters for conventional bikes is pessimistic.

And yet even that one gave me a 22.5mph at my wattage in the drops, not including my aerobars. I don't think my powermeter is in error just based on what I see from other powermeter users in my weight bracket on hill climbs on strava, but anything is possible. I use a garmin edge set to autocalibrate with the powertap , and I wasn't aware there was any way for it to read high. I thought the failure mode for these was low readings. Is that not the case?

The only thing that comes to mind is the tall head tube on my Roubaix. The stem is at -8 degrees w/0.5" of spacers, so I can go a bit lower but that could affect my hip/torso angle and I'm generally pretty happy with my fit. Wheels are 32mm deep in front, 46mm in back. GP4000S @ 100psi.

I'm skinny, and look like every other cyclist out there so again it's why I'm a bit shocked at how far off the estimates are. I don't feel like I'm an outlier when it comes to size and position on the bike.

Fat Boy
10-20-11, 11:59 PM
So analytic cycling predicts 24.7mph at 239w, compared to my 20.7mph at 239w. 4mph is a huge difference at these speeds. Anybody have input?

I just dug through some data to find a similar effort for me. A few months ago I did a constant 67 minute SST effort around a closed loop at exactly 239 watts. I covered 23.2 miles. Average speed, 20.7 mph. Now I'm shorter and lighter than you (I usually do SST work on the hoods) and we've got a hundred other variable to factor, but I was pretty interested to see how it matched your numbers.

RChung
10-21-11, 04:33 AM
And yet even that one gave me a 22.5mph at my wattage in the drops, not including my aerobars. I don't think my powermeter is in error just based on what I see from other powermeter users in my weight bracket on hill climbs on strava, but anything is possible. I use a garmin edge set to autocalibrate with the powertap , and I wasn't aware there was any way for it to read high. I thought the failure mode for these was low readings. Is that not the case?
Either 1) your power meter is off; or 2) you're a parachute; or 3) it was windier than you thought. Or maybe all three. Check your PM, then check your CdA. If your PM is reading right and the wind really was negligible then .44 m^2 for CdA while on the aerobars means you're a parachute. That's street clothes on bar tops of commuter bike territory.

Grumpy McTrumpy
10-21-11, 07:39 AM
Here's some laps I did at 230w at an outdoor velodrome, on my road race bike with normal kit and helmet, in the drops.

It was not a completely calm day, but the wind wasn't a major factor. The average speed came out to 22.9mph but I would expect that was a bit high due to wheel circumference issues. Bet on 22.5

I do have a rather small frontal area though. Some folks have big shoulders that are just impossible to hide. I am not one of them. I also have a pretty aggressive position on the road bike.

http://gallery.me.com/andrewwilliams4/100070/velodromelaps/web.jpg?ver=13192005400001

the faster part (where my speed is sitting above the average line) is around 250w and 23.5mph indicated (actual maybe 23.2)

It would not surprise me at all if a larger rider would be at 21mph for the same power for the overall 12 minutes, since I have large teammates who show similar numbers. It also would not surprise me if a rider with a higher handlebar position would have similar numbers to the larger rider.

Fat Boy
10-21-11, 10:56 AM
OK, now I'm worried my PT is reading high! It zeroes at zero, so I don't know what else I can do. Live with it until the pedals come out, I guess, as the precision seems good even if the accuracy is lacking.

AzTallRider
10-21-11, 11:06 AM
The FTP test results:
http://connect.garmin.com/activity/123071041

What's with the periodic drops in speed, power and cadence. It looks almost like you had stoplights?

gregf83
10-21-11, 11:37 AM
So analytic cycling predicts 24.7mph at 239w, compared to my 20.7mph at 239w. 4mph is a huge difference at these speeds. Anybody have input?One suggestion would be to find a better course where you can put down steady power. I don't know how big an impact it has but you have a fair number of periods where you're coasting for 10 seconds at a time. I see dozens of power spikes between 400-500W. If nothing else, eliminating those spikes should boost your AP.

Also the sections where you're having to slow down are costing you at least a minute.

Fat Boy
10-21-11, 11:40 AM
It's a bike path. I'm guessing the coasting times are underpasses and bridges.

ericm979
10-21-11, 12:43 PM
That bike path is not flat. The file shows 561 feet of elevation gain.

jmX
10-21-11, 12:59 PM
Indeed it's a bike path (more like a bike highway) through a very urban Southern California. It snakes under probably a dozen roads along the 10 miles and I was coasting the decline then going 400-500w up the short incline on the other side. Each one is probably <20 seconds, and I doubt my speed on those ever got under 18mph. I do not believe these affected average speed much.

Additionally there are 2 slow bridges that I had to cross at probably 13-17mph, each one lasting 30-60 seconds and on an out and back that makes a total of 4 times, plus one time I had to slow to 2-3mph to do a tight u-turn on the course. I can see that taking 0.2-0.3mph off the average.

RChung, as for it being windier than I thought, my out speed and my back speed were nearly the same so there wasn't much head/tail wind. WKO+ reports out speed was 21.2 @ 240w, back speed was 20.2@239w. Maybe there were light crosswinds.

Grumpy, thanks for the input. Maybe I'm just way too upright. I've been thinking about getting rid of the spacers so maybe I'll work those out over the winter. Had hand pain from extra weight I was putting on the hoods last time I tried though. It is probably time to evolve my fit a little as I was professionally fitted when I was brand new to the sport a year ago.

FatBoy, pretty interesting how our numbers matched up. I have to ask, just how fat are you? ;)

It appears I'm many years off from a good 40k TT, at least on this bike.

Racer Ex
10-21-11, 01:59 PM
You'd be shocked at how a few position adjustments can move your wattage at a given speed. Tires, wheels, helmet...all things things also factor in.

rpeterson
10-21-11, 03:34 PM
Got a picture of your position?

mollusk
10-21-11, 05:01 PM
That thing is terrible.

I have found it to be pretty accurate for me using "road bike tops and drops" whenever I have real power data to compare to it.

Of course if you have real data from a wind tunnel or carefully controlled coast down tests you can do better.

jmX
10-21-11, 05:36 PM
Got a picture of your position?

Here's my imitation of a parachute, aka, my current position on the bike.

Aerobar animation:
http://jmx.ls1howto.com/pics/2011/2011-10-20_aerobar_anim.gif
URL: http://jmx.ls1howto.com/pics/2011/2011-10-20_aerobar_anim.gif

Aero fit:
http://jmx.ls1howto.com/pics/2011/2011-10-20_aerofit.jpg

Dropbar position:
http://jmx.ls1howto.com/pics/2011/2011-10-20_dropfit.jpg

Nate552
10-21-11, 05:51 PM
Holy Head Tube! How far are your local TT's? Are you planning on doing them on that road bike?

Racer Ex
10-21-11, 06:13 PM
Holy Head Tube! How far are your local TT's? Are you planning on doing them on that road bike?

He's in my neck 'o the woods. 20k and under for the most part.

It's a truly horrible aero position... I'm surprised you're slower in the drops (same wattage same course?).

There's a lot going on there with your fit.

jmX
10-21-11, 06:31 PM
I can appreciate the feedback, but would wish for a bit of constructive criticism if possible. The primary use of the bike is endurance and climbing, I never bought it under the pretense of time trialing. Doing my FTP test on the aerobars yesterday was me A) doing an FTP test, and B) checking if it's feasible to attempt a TT on this bike. From the responses here I'm gathering that's a no, but I'd still like some details and feedback on why.

The local TT is a semi hilly 11mi. Aside from TT's, I do solo organized timed centuries about 3 times a year and would think that going down this path will yield quite a bit of time on those as well.

The non-aerobar fit you see is the fit from a well known local fitter. Me slapping aerobars on it is just that and nothing more.

RChung
10-21-11, 08:00 PM
Here's my imitation of a parachute, aka, my current position on the bike.
Hmmm. Well, so maybe your power meter is okay after all.

Racer Ex
10-21-11, 08:14 PM
Santiago Canyon?

You can get a decent TT position on most any bike.

For both the aero and standard road position you're too high...you're presenting a huge amount of frontal area and what you're presenting is essentially a big bucket for the air to grab. I'd also be inclined to have you on a smaller frame or try a shorter stem when you start pulling spacers. It looks like you're reaching. As you drop the bars you're extending the reach down and forward.

Suggestions on the aero position:

Arm rests are way too far forward, and the whole thing is, again, way too high. You want to shrink all those openings between the legs, knees and arms. Ideally your back is flat and your head isn't sticking up above your shoulders. A pic from the front would be very helpful.

For comparison...

223982

If you want to try some stems I've got a box full (PM me), as do most local LBS. If the shop won't let you try a "take off" they are kinda lame.

I'm pretty much doing all the SoCal TT series, I would suggest that you go ahead and give it a shot. They are very low key and friendly. Most TT folks are just racing against themselves and are happy to help out a new racer. I can give you some suggestions on the course.

Racer Ex
10-21-11, 08:18 PM
Hmmm. Well, so maybe your power meter is okay after all.

Or it could be reading low.

(Don't take any of this stuff personal jmX...the curmudgeon factor is high in the racing forum)

Nate552
10-21-11, 08:51 PM
I'm going to make some recommendations based on you TT'ing on that bike, for 20K-ish TT's. First, Racer Ex's position examination is correct. Second, you're not a big guy (weight wise), so getting small should be your absolute goal. You HAVE TO GET LOWER. You have a challenge though, because of that head tube, and your frame is too large. Assuming you'll keep that bike, and use clip on aerobars....here's what I would do if I was you.

1) Buy an adjustable stem. Remove your current stem, take off spacers, install adjustable stem and go as low as it allows. Get your elbows to the same height as your TT. I'm not kidding.
2) Get a TT seat. Is your seat tilted down in that set up? It kind of looks like it. Look at ISM, Cobb, etc. Chances are, that stock seat won't be comfortable for this.
3) Maybe find some clip ons that have a lower stack height.
5) Report back with new position

If you're committed to the TT and am willing to do some mechanic work....
1) Cut cables
2) remove road handle bar and stem
4) install TT bars and shifters
5) recable
6) go faster

echappist
10-21-11, 09:06 PM
RX, how much saddle-to-bar drop do you got there? also, are you scooting forward in that photo?

jmX
10-21-11, 09:34 PM
RacerEx, a smaller frame? Half the bike shops I went to were trying to fit me on a 61cm, but I was pretty sure that was too big. I went for the 58cm. Unfortunately my aerobars are non-adjustable. I'll be looking for some with a low height and adjustibility this month it sounds like. I know they make shorter ones intended for road bike use, and what I have are not that type. I can adjust my stem to -16 degrees and drop spacers, so that'll give me another inch or two. Santiago Canyon is the TT i've had in mind, but looking at the results I'm not even near the ballpark as far as times go. Thanks for the advice...I'll probably come out to an event early 2012. Like you said, I'm mostly wanting to compete against myself but it'd be nice not to be in last place by 4 or 5 minutes :D Know of any triathlete shops in OC where I could peruse clip-ons?

Nate552, sounds like you're on the same page as RacerEx. My seat is a Romin, which is supposed to be great for being low. It isn't angled down at all. I'll look at road clip-ons with a low stack height. I think HED makes a good set.

I'm pretty comfortable in my current position, even up to 10 hours of riding, so I'm a bit hesitant to evolve it. The end goal is fast 100 mile events, solo, so things have to stay reasonably comfortable. I'll make tweaks and report back.

carleton
10-22-11, 12:11 AM
I can't recommend the LOOK Ergostem highly enough.

It's heavy and expensive, but worth it.

http://02d5d89.netsolhost.com/images/Parts/LookErgoStem_08.jpg

10-22-11, 05:18 AM
[QUOTE=jmX;13397154]Here's my imitation of a parachute, aka, my current position on the bike.

Aerobar animation:
http://jmx.ls1howto.com/pics/2011/2011-10-20_aerobar_anim.gif
URL: http://jmx.ls1howto.com/pics/2011/2011-10-20_aerobar_anim.gif

Not trying to offend you or anything, but that is a pretty upright position for an aerobar.
It doesn't surprise me at all that you have these numbers when your aerobar is actually positioned higher than your saddle.
Ar you having back issues or something like that?
Your headset is huge, which leads to your handlebar being very high and on top of that the aerobar is mounted above that bar.
If at all possible, get a 45 degree stem and flip it upside down ... then install an aerobar under your handlebar.
Another option is to remain like this and be slow ;)

Nate552
10-22-11, 07:38 AM
I'm pretty comfortable in my current position, even up to 10 hours of riding, so I'm a bit hesitant to evolve it. The end goal is fast 100 mile events, solo, so things have to stay reasonably comfortable. I'll make tweaks and report back.

You're not evolving it, you're changing it for TT's. Your goals, 100 mile events and 20K TT's are very different and require completely different set ups. You can keep your road position, you're just swapping stems for the TT (or TT training rides). When you're done, put your current stem back on and you're back to your road position. I know we don't have to tell you, but a TT bike would solve this.

I can't recommend the LOOK Ergostem highly enough.

It's heavy and expensive, but worth it.

An excellent tool for experimenting with positions.

RChung
10-22-11, 09:05 AM
(Don't take any of this stuff personal jmX...the curmudgeon factor is high in the racing forum)
What?!? I thought I was being kind by not linking to this:

RChung
10-22-11, 09:08 AM
I can't recommend the LOOK Ergostem highly enough.
One of my buddies had one of those. He said it was great in concept but it kept slipping and he couldn't recommend it highly enough.

Racer Ex
10-22-11, 09:37 AM
RX, how much saddle-to-bar drop do you got there? also, are you scooting forward in that photo?

11cm to the tops, 26cm to the drops. I always ride on the nose in the IAB position.

RacerEx, a smaller frame?

That's what it looks like, but remember I'm just looking at a picture and can't really reference saddle position and the like. And you're also in the racing forum; a lot of us ride smaller frames than what would be considered "normal", as do the pros. Bike shop tend to fit people on the seat tube, racers tend to fit themselves on the top tube and also look at head tubes. You'll see a lot of stems in the 110-130 length.

I'll probably come out to an event early 2012. Like you said, I'm mostly wanting to compete against myself but it'd be nice not to be in last place by 4 or 5 minutes :D

A lot smaller and not as fast a crowd at the winter races, so you'll have less people blowing past you. And the gaps are pretty big front to back. Plus if you really stink it up, the next time you have huge room for improvement. ;)

Know of any triathlete shops in OC where I could peruse clip-ons?

We don't use the "T" word here. But no, I don't. New to the area. Lots of stuff online, if you want an opinion on something you find drop me a PM. The adjustable stem is a great place to start.

I'm pretty comfortable in my current position, even up to 10 hours of riding, so I'm a bit hesitant to evolve it. The end goal is fast 100 mile events, solo, so things have to stay reasonably comfortable. I'll make tweaks and report back.

As Nate said, 100 miles is different than a TT. I set Tri folks up according to distance...Ironman will certainly be less aggressive than a sprint. That noted, I can do 100 miles pretty easily in the set up in the picture, though not all of it in the IAB (invisible aero bar) position. And my position has evolved slowly; making smaller changes, adapting, change again, adapt, Etc. What's counter-intuitive is that I've had less back issues the lower and further out I've gone. Long theory on why this is the case, and won't bore folks with it.

Remember if you can get lower you're going to go faster on less watts...which makes those 100 milers go by a lot quicker for the same effort.

jmX
10-22-11, 05:47 PM
So, I went to -16 degrees and got rid of all the spacers. I was as comfortable as usual today on a 90minute ride. The aerobars are still a good 1.5-2" above the base bars so that'll be the next change. I also moved my hands back so I was grabbing the aerobars about 3/4 the way out rather than up at the "ski tips" and it seemed to feel better on my lower back. So shorter lower aerobars (ie, ones for a road bike) will be a good change.

Carlton, that does look like it could be a solution if I really want to TT this bike. Thanks for that, I feel like I've seen that referred to a few times on fit sites.

Are you having back issues or something like that?

It's an endurance bike, as my focus is endurance. The same bike for smaller people has a much shorter headtube, so it's compounded by the fact I'm 6' 1".

You're not evolving it, you're changing it for TT's. Your goals, 100 mile events and 20K TT's are very different and require completely different set ups. You can keep your road position, you're just swapping stems for the TT (or TT training rides). When you're done, put your current stem back on and you're back to your road position. I know we don't have to tell you, but a TT bike would solve this.

I hear you. I suppose in the last 24 hours of reading these replies my main priority is now a more optimal day to day position, and have it be the fit that would be used for timed centuries. A short TT position is looking more unlikely and thus less important. The stem referenced above or some other steep angle stem seems like a reasonable option if I pursue that path.

RacerEx, I knew the T word was a no-no around here, thats why I used it. :D Lower did feel pretty good today, and pretending my aerobars were shorter seemed to help my back quite a bit. Thanks for all the input.

RChung, are you the Chung of Golden Cheetah fame? If so, thanks! I'm a bit of a math nerd myself as you may tell from the software in my sig.

carleton
10-22-11, 06:21 PM
One of my buddies had one of those. He said it was great in concept but it kept slipping and he couldn't recommend it highly enough.

I call "user error" on that. I've used my Ergostem during fit experiments on the track for years. I'm a relatively strong guy (I can produce over 300NM of torque, 1900N AEPF, and 2K watts) and haven't had the stem move.

Here is a photo of Zhang Miao of China using the Ergostem at the 2009 UCI Track World Championships where I assume he's warming up for the Kilo where he placed 15th with a respectable 1:03.427.

http://www.bikeforums.net/attachment.php?attachmentid=224078&d=1319325633

EDIT: It may not be the stiffest on the market, like say, a Thomson X4 or 3T ARX. But, it's certainly strong enough for road TT use where, even at world-class levels, forces are a fraction of what a rider like Zhang Miao might produce on the track during a standing-start event like the 1KM time trial where a rider goes from 0 to +40MPH (+65KPH) within 200-250M.

224078

carleton
10-22-11, 06:37 PM
For those not familiar with the forces involved, here is Sir Chris Hoy starting a Kilo. He's up to over 40MPH (65KPH) before he settles into the aero tuck.

This is not using an Ergostem. I can't find a video of a rider doing a kilo using that stem. But, based on Zhang Miao's splits from the event, his start was within tenths of a second of this.

No road TT rider puts forces on a stem like this. This effort is in the rage of 2,300-2,500W, in case you were wondering.

RChung
10-22-11, 06:44 PM
I call "user error" on that. I've used during fit experiments on the track for years. I'm a relatively strong guy (I can produce over 300NM of torque, 1900N AEPF, and 2K watts) and haven't had the stem move.
Lighten up, Francis. This was last century, it wasn't a threadless stem, it had the old post and expansion bolt so maybe Look has changed the design since then. Or maybe he stripped a thread. I was making fun of "can't recommend it highly enough." What, you get a commission on these things? Cuz it seems like I struck a nerve.

RChung
10-22-11, 06:49 PM
RChung, are you the Chung of Golden Cheetah fame? If so, thanks! I'm a bit of a math nerd myself as you may tell from the software in my sig.
Hmmm. I'm the guy who worked out the VE algorithm that shows up as Aerolab but I didn't think that I was famous for it. I'm hoping I'm more famous for my matinee idol good looks.

carleton
10-22-11, 06:51 PM
Lighten up, Francis. This was last century, it wasn't a threadless stem, it had the old post and expansion bolt so maybe Look has changed the design since then. Or maybe he stripped a thread. I was making fun of "can't recommend it highly enough." What, you get a commission on these things? Cuz it seems like I struck a nerve.

Haha. No. I was just being thorough. I didn't mean to come off as intense :)

I've had other people say they wouldn't use it because they fear it might slip. I don't want this guy to miss out on a good product because of one guy's experience, especially if it will solve a problem. I think it's probably one of the best cycling purchases I've made so far.

carleton
10-22-11, 07:12 PM
jnX,

Here's my 2 cents on your aerobar position:

http://jmx.ls1howto.com/pics/2011/2011-10-20_aerobar_anim.gif

Are you using a lay-back seat post? It appears so in this animated image. If so, you are making a relatively low 73 degree seat tube and making it even lower, which brings you backwards. Many TT bikes are more aggressive. Like 75-76 degrees (seemingly almost vertical). This rotates the rider forward using the bottom bracket as the axis.

My Tarmac came with a slightly set-back seatpost. I replaced it with one that didn't set back at all.

When you bring the saddle forward and up (the measurement from the top of the saddle to the BB spindle will be exactly the same) this will force your bars down and forward into a more agressive position. This puts more weight on your hands, arms, and shoulders as well as add neck strain from your head rising up to see down the road. But, your upper body will displace less air as you will be lower. You'll have to find a balance somewhere. But right now, you are sort of in an upright riding position.

You've got to find a happy medium between this:
http://jmx.ls1howto.com/pics/2011/2011-10-20_aerofit.jpg

and this:
http://ayearonthebike.files.wordpress.com/2011/03/corvos_cancellara_time_trial.jpg

BTW, the TT position isn't supposed to be comfortable for long 10 hour touring rides :) This is one reason why some people own multiple bikes. But, in lieu of buying another bike, you can make adjustments to your current bike. Just be aware that, generally speaking, what is more aerodynamic is less comfortable.

Racer Ex
10-22-11, 07:50 PM
http://ayearonthebike.files.wordpress.com/2011/03/corvos_cancellara_time_trial.jpg

BTW, the TT position isn't supposed to be comfortable for long 10 hour touring rides :)

Spartacus has done 6 hours rides on his. The most I've done is around 3.5 hours. If you're set up correctly and well adapted, you should be able to crank out some pretty long rides. Most people aren't set up well though. And even folks I've positioned for Ironman length events are still fairly laid out.

The problem most people have with TT positions is either they aren't right, or they rarely ride the bike. Or both in a lot of cases.

carleton
10-22-11, 08:07 PM
Spartacus has done 6 hours rides on his. The most I've done is around 3.5 hours. If you're set up correctly and well adapted, you should be able to crank out some pretty long rides. Most people aren't set up well though. And even folks I've positioned for Ironman length events are still fairly laid out.

The problem most people have with TT positions is either they aren't right, or they rarely ride the bike. Or both in a lot of cases.

Good point.

jmX
10-24-11, 08:02 PM
Alright, today I took the FSA 9mm headset cap off my Stumpjumper and swapped it with the 20mm Cane Creek one on my road bike, that bought me another 11mm of drop, so I've lost about 1.5" of bar height since the photos were posted. I did 60 miles yesterday with just a 1" drop and it was fine, so hopefully the extra 11mm are fine too. We'll see.

I plugged all the data from the FTP test and weather stations into Golden Cheetah and my CdA = 0.42, or a frontal area of 0.83m2 at 0.5 drag coefficient. My CdA before the aerobars was 0.45'ish (based on 2 rides), and the CdA with the extra 1" drop was 0.41 (based on sat/sun rides). Aerobar pads are still 1.5"-2" above the base bar so that is the last problem I can really tackle.

Impressive how quickly aero starts to matter on a bike.

Racer Ex
10-24-11, 10:30 PM
Impressive how quickly aero starts to matter on a bike.

And the impact is greater the faster you go.

There are a few people I know that are pushing sub .2 CdA on their TT bikes...Nate being one of them.

You're on the right track and it's good you've been able to drop the bars with no impact. I would suggest riding this position for a bit then start looking at drop stems; you also might want to consider a bar with a greater drop, I use a much more traditional bend, newer bar designs (like head tubes) are biased towards a higher position. If you want a reference point, check out where your drops are in relationship to the front wheel, then look at the pic I posted.

carleton
10-24-11, 10:43 PM
And the impact is greater the faster you go.

There are a few people I know that are pushing sub .2 CdA on their TT bikes...Nate being one of them.

You're on the right track and it's good you've been able to drop the bars with no impact. I would suggest riding this position for a bit then start looking at drop stems; you also might want to consider a bar with a greater drop, I use a much more traditional bend, newer bar designs (like head tubes) are biased towards a higher position. If you want a reference point, check out where your drops are in relationship to the front wheel, then look at the pic I posted.

This is a good point. I used to eyeball how deep a rider's position was by how deep their drops were. But, I soon learned that that's is irrelevant due to stem rise, spacers, and head tube length. It's better to look at:
- How close the hands (or forearms in the TT tuck) are to the top of the tire.
- The drop of the hands/forearms from the saddle height. But this is more proportional to the rider's height. Taller riders will have a deeper drop than shorter riders. Note that the base of your forearms are above your saddle.

Here is some food for thought:

"Aero positioning for road bikes" with clip ons: