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Old 05-07-07, 02:38 PM   #1
patentcad
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TT aero advantage question

In the TT I did Saturday most participants used regular bikes since it was mostly uphill. But there was one fast, flat section (I was doing 25mph or so) that was nearly a mile long. I'm curious: on a typical rolling TT of say 12 miles or so, how much faster would the aero position of a TT rig make you vs. a typical racing bike, expressed as time saved? 20 seconds? 40 seconds? There must be research on this stuff.

I'm assuming this would be a minor factor on a mostly uphill course, but I'm sure anyone who had a TT rig would have used it on these roads Saturday (and they did), it was not all pure climbing.
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Old 05-07-07, 02:53 PM   #2
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You have Zipps, so you don't need any other aero advantage, remember??
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Old 05-07-07, 03:02 PM   #3
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Probably a lot. You've zipps already though, so you're good to go

I'm trying to finagle a deal on a TT bike, since I've got stage races coming up... I've been Merckxin it and my TT is strong like bull, at 25.7mph. I figure with Aerobars, aero helmet, skinsuit, aero position, and aero wheels I'll be doing some low level flying.
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Old 05-07-07, 03:10 PM   #4
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Quote:
Originally Posted by UT_Dude
You have Zipps, so you don't need any other aero advantage, remember??
Just answer the question.

I doubt it's 'a lot', but with all the weenies here, there MUST be a link to some exhaustive study with graphs and charts.

The first person that says 'lose 5lbs and get a PowerTap' gets whacked with a 700 x 23c inner tube.

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Old 05-07-07, 03:14 PM   #5
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d) Not enough information

It will vary quite a bit for obvious reasons. From nothing to 90 seconds or so.


The other answer is, ask this guy...

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Old 05-07-07, 03:16 PM   #6
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Haha, OK . It depends a *lot* on how you're positioned. If you're already using clip-ons, you won't gain as much (though you will still gain, because TT bikes can put you in a more aero position than clip ons.... and also in a position that generates more power).

It's hard to quantify it without some more details. Were you using clip-ons before? How steep were the climbs? Perhaps an average speed from your TT?
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Old 05-07-07, 03:30 PM   #7
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Quote:
Originally Posted by UT_Dude
Haha, OK . It depends a *lot* on how you're positioned. If you're already using clip-ons, you won't gain as much (though you will still gain, because TT bikes can put you in a more aero position than clip ons.... and also in a position that generates more power).

It's hard to quantify it without some more details. Were you using clip-ons before? How steep were the climbs? Perhaps an average speed from your TT?
Forget the High Point TT, too uphill. I'd like to do more traditional TT's with rolling to flat terrain. No clip on bars now. Just interested in TT bike vs. regular bike with drop bars comparison.
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Old 05-07-07, 03:30 PM   #8
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Quote:
Originally Posted by TheKillerPenguin
Probably a lot. You've zipps already though, so you're good to go

I'm trying to finagle a deal on a TT bike, since I've got stage races coming up... I've been Merckxin it and my TT is strong like bull, at 25.7mph. I figure with Aerobars, aero helmet, skinsuit, aero position, and aero wheels I'll be doing some low level flying.
I thought you had some clip-ons you were using for TTs? If that is the case, that is not Merckxin it; he was before the invention of clip-ons. You have more likely been Lemonding it; he was the first to use clip ons in the TdF in '89.
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Old 05-07-07, 03:33 PM   #9
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I used aerobars twice last year for stage races, I'd imagine with minimal advantage since I'd only had 2 days to setup and practice my position before each race (if you haven't seen the picture of my position at Owasco, if you need a laugh I'll post it ). But, that's not what I'm referencing.

My fastest TT ever was done w/o aerobars, and was 10mi @ 25.7mph.

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Old 05-07-07, 03:34 PM   #10
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http://www.analyticcycling.com/

Specifically,
http://www.analyticcycling.com/RiderAeroStudy.html
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Old 05-07-07, 03:50 PM   #11
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http://www.socalttseries.com/Trainin...7/Default.aspx
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Old 05-07-07, 03:53 PM   #12
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Quote:
Originally Posted by TheKillerPenguin
I used aerobars twice last year for stage races, I'd imagine with minimal advangate since I'd only had 2 days to setup and practice my position before each race (if you haven't seen the picture of my position at Owasco, if you need a laugh I'll post it ). But, that's not what I'm referencing.

My fastest TT ever was done w/o aerobars, and was 10mi @ 25.7mph.
OK -you were definitely Merckxin it. You are going to be damn fast if you ever Zabriskin it .
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Old 05-07-07, 03:53 PM   #13
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Quote:
Originally Posted by obra3
That's a nice, concise summary... and written by the guy who invented my Q-Rings!
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Old 05-07-07, 03:56 PM   #14
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Ah... OK, that helps a lot. On a regular TT course, you can pick up something on the order of minutes depending on the length using a TT bike over riding in your drops. The effect is less pronounced if the course goes mostly uphill (AKA, not an out and back...if it goes downhill too, aero is good..).

Honestly, though, a lot will depend on how you're fitted. Some people opt for more aero, less power (you go for this if you're a weaker rider), some people opt for less aero, more power (the inverse...you get the idea). When i'm on my Cervelo, I go faster mostly because of the aerodynamics, but because of the way we could arrange my saddle position, I actually put out slightly higher wattage too. Summarize? Fit matters.

Other stuff, specifically having an aero helmet (though really only if you're riding a TT bike position), and a skinsuit can drop quite a bit of drag too.

If you add it all up, you can drop your time fairly significantly. Think like...3 mins over 20k might not be too rediculous.
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Old 05-07-07, 03:58 PM   #15
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flat to rolling terrain, .5 mph to 1 mph, depending on 1) how aero your position alredy is in the drops, 2)how aeroyou set the bike up with tt bars,and 3) how well you produce power in the tt bar position.

There's a thread in the road cycling forum, where a number of people claim 2 mph, but either there road position just totally sucks, or they're getting a big plecebo effect.

, I've found the whole deal, trispoke front, disc rear, booties, TT helmet, arendul TT waterbottle, and aerobars is only worth maybe a fraction over 1 mph in my personal expereince. YMMV.
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Old 05-07-07, 04:01 PM   #16
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I don't know about the .5 to 1mph bit. I've ridden TT's in my drops, jersey/shorts, Atmos helmet, then i've ridden TT's on my Cervelo, skinsuit, Garnea Rocket Helmet, deep wheels, etc, and all in all, it's considerably more.
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Old 05-07-07, 04:10 PM   #17
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^^^^
the .5-1mph was for just the TT bars. Full deal for me is just a little over 1mph, but thats comparing a road bike with Zipp 404's and a decent position in the drops.
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Old 05-07-07, 04:17 PM   #18
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It's not the TT bike itself that reduces your drag but rather the fact that you're likely able to put your body in a much more aerodynamic position on a TT bike due to frame geometry than you would be able to attain on a road bike.

To maintain a speed of 27.5mph on flat terrain, I must generate about 30 more watts on my road bike (with 30mm wheels, aero bars, skin suit, and aero helmet) than on my TT bike with Zipp wheels. I'd predict that 25 watts of this is due to body position rather than the aerodynamics of the equipment itself.

Unfortunately, without acclimating oneself to a more aggressive TT position, it's not uncommon to see a dropoff in power of up to 50 watts on the TT bike compared to the road bike. So it's actually possible for the unacclimated athlete to go slower on the TT bike.

But I'm talking about a flat TT course and I know Patentcad was asking about a hilly course. Eh, well.

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Old 05-07-07, 04:23 PM   #19
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Patent, read the articles above. I actualy rode High point with my full TT setup last year and did well, but not outstanding. I WAS blying through the flat section and those rollers though.

As for the TT bike, it really depends on how well you can adapt to the position, but I am about 2.5-3 mph faster on average on rolling terrain and even moreso on flat terrain. I am also VERY good in the TT position vs. my road position so take that into account. If you are thinkig Somerset TT, go with the TT bike if you have one.
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Old 05-07-07, 04:27 PM   #20
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Thanks for the info boys.

I really did enjoy the TT immensely. First it focused my training for the better part of two months. Then the race scene was very warm and friendly - moreso than many mass start events in my view. Then in the even itself: virtual zero crash danger, no getting dropped, much closer to running a 5K race for whatever time you can record. You see how you stacked up on a website the next day. Very cool. Very neat way to focus my training. I love climbing, but there are limted uphill TT's, so I'm thinking about picking 4-5 TT's of various types annually. But if that's the focus of much of my riding/training, I'll research TT bikes.

Which dovetails nicely with Celticfrost's prediction that I would soon acquire more bike schwag.

Correct.
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Old 05-07-07, 04:29 PM   #21
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Quote:
Originally Posted by DrWJODonnell
As for the TT bike, it really depends on how well you can adapt to the position, but I am about 2.5-3 mph faster on average on rolling terrain and even moreso on flat terrain. .
I don't get close to that difference. Guess it shows I don't spend enough time on my TT bike.
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Old 05-07-07, 04:33 PM   #22
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What about headwinds and tailwinds?

I'm presuming that the more aero into a headwind, the better.

But alot of TT's are out and back, so at some point that headwind will be a tailwind. How much of a benefit is aero then? Also, is there some point where aero is a DISadvantage with a tailwind? There's probably some other factors to consider as well (surface area of rider, wind speed, etc.).
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Old 05-07-07, 04:38 PM   #23
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Bicycling Magazine did an interview with some guys from MiT who studied the aero position for cyclists and if I remember correctly, they ranked a series of items based on wattage saved or something along those lines. Someone who still has the article feel free to correct me (I long-since discarded the magazine), but I think the ranking of most valuable items was something loosely like:

1) disc wheel
2) aero bars (these two might have been around)
3) aero helmet
4) aero front wheel
5) bottle on your seat tube vs. the down tube

Again, someone feel free to correct that list, add to it, etc. I'm going off of memory.

In terms of seconds saved, I have no real idea. Hopefully the wattage numbers associated with the article would be of some use though.
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Old 05-07-07, 04:52 PM   #24
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I come up with 2-2.5 mph difference riding my TT bike over my road bike. That doesn't include other aero gear. Like I said, though, I put training time in on my TT bike and the saddle position lets me generate more power (25W? that's a guess).
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Old 05-07-07, 05:00 PM   #25
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I've got a TT coming up at the Cascade stage race. It's a new course that climbs 900 feet in 7.5 miles (about 2.3% ave grade), then turns around and comes back down the hill.

I don't have a TT bike, so I'll be going with clip ons. I did one race with clip ons last year and it was a disaster. (note: practice with the clip ons!) I didn't put them on tight enough and they were nearly vertical within 2 minutes of starting.

I'm glad the TT is the first stage. That way I can put the bars on before I leave for the race and get in a few practice rides, and not have to worry about putting on the bars between stages.

I also don't have a disc wheel, but I suppose it would really help on the 2nd half of this race.
I'll be using my Zipp 303's since they're the most aero wheel I have.

I will at least have a TT helmet and a skin suit (and my H2O bottle on the seat tube).

Anything else I can do? Gloves or no gloves? Shoe covers?

Also, do you guys think that even effort is better, or use more effort on the first half?
According to this velocity predictor:
http://w3.iac.net/~curta/bp/velocity/velocity.html

The difference between 320W and 350W is about 50 seconds on the climb, but only 15 seconds on the descent. Does this sound correct?
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