"The 33"-Road Bike Racing - 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.

You have Zipps, so you don't need any other aero advantage, remember??

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.

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.

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...

http://bajolasruedas.iespana.es/fotos/1989fignon.jpg

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?

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.

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.

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.

http://www.analyticcycling.com/

Specifically,
http://www.analyticcycling.com/RiderAeroStudy.html

http://www.socalttseries.com/Training/Articles/AerodynamicsforTimeTrial/tabid/217/Default.aspx

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:) .

http://www.socalttseries.com/Training/Articles/AerodynamicsforTimeTrial/tabid/217/Default.aspx
That's a nice, concise summary... and written by the guy who invented my Q-Rings!

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.

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.

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.

^^^^
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.

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.

--Steve

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.

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.

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.

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.).

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.

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).

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?

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

No gloves. Shoe covers. Flip stem?

--Steve

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?

No gloves. Shoe covers for sure. Don't worry about the stem or the bike fit. You're bound to create more problems than you solve. Maybe spend some time on a trainer playing with the clip on positioning. DEFINITELY spend time practicing with them (which you know already!).

Just make sure you're really well warmed up. TT's aren't like road races where you can practically warm up during the race -- the effort the whole time counts. Do at *least* 20 minutes with a few efforts, more if you can.

Be early to your start time, that's another important thing to learn :) .

You're probably better gunning it up the hills, where your aerodynamic disadvantage is less important that going down. Run your threshold up the hill (350 is crazy high), and just give it everything you have left on the way down, since it's going to matter less. Just make sure you're in your drops the whole time!

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

Penguin, you need to come to Michigan, for some FAST TT'ing. Hell, *I* can do 25 MPH here.

Anyone have rec's for shoe covers, or claims for wattage reduction?

ok guys, how do shoe covers help during a tt? thanks, karen

The airflow over those velcro straps isn't the best in the world, and at the top of your pedal stroke, your foot is going faster than you are.

It minimizes that drag.

Just did the calcs, feet go ~3.6 MPH faster than your body.

Just did the calcs, feet go ~3.6 MPH faster than your body.

And ~3.6 MPH slower than your body (6:00 position). Sounds like an offset to me.

Except it isn't due to the non-linearity of power required to go a certain velocity. I.e., power required is proportional to velocity cubed. Let's say you're going 22 MPH. At the top of the stroke, your foot's going 25.6 MPH - which works out to need ~58% more power. At the bottom of the stroke, you're going 18.4 MPH - which works out to need only ~41% less power. If you're doing 120 RPM rather than 90 RPM, the numbers work out to be 81% and 52%.

Sure, it's small. That's what puts the O in OCP.

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.).
Unless your talking about 25mph-30mph or greater winds then for sure anyone racing a TT will be going faster than the tailwind...so even though they are facing less wind resistance there is still wind resistance. If you DID to a TT in say a 40mph sustained wind then for sure you would want the TT position into the wind otherwise you would be dead. :D

Unless your talking about 25mph-30mph or greater winds then for sure anyone racing a TT will be going faster than the tailwind...so even though they are facing less wind resistance there is still wind resistance. If you DID to a TT in say a 40mph sustained wind then for sure you would want the TT position into the wind otherwise you would be dead. :D

If flat ground speed (with no wind) = N mph and tailwind speed > N mph, then aero advantages minimal/ non-existent.

Sure, it's small. That's what puts the O in OCP.

Correct.

Profoundly, incredibly, spot-on, devastatingly, redundantly, incessantly, infinitely Correct.

If flat ground speed (with no wind) = N mph and tailwind speed > N mph, then aero advantages minimal/ non-existent.
Right that is what I am saying. But if you are racing in a TT you are avging what? 25 mph? 28 mph? So what are you doing downwind? 32mph? More? So your saying this TT you are questioning aero advantage about is being ridden in >32mph constant winds? And even if you were you would then be able to go even faster.

My point is that you will always be going faster than the tailwind so you will always want as much aero advantage as possible.

Unless your talking about 25mph-30mph or greater winds then for sure anyone racing a TT will be going faster than the tailwind...so even though they are facing less wind resistance there is still wind resistance. If you DID to a TT in say a 40mph sustained wind then for sure you would want the TT position into the wind otherwise you would be dead. :D


Incorrect. lol.
With a 40 mph headwind, I'd be home on the couch. Either that or more likely going in the opposite direction.

I did a 12-mile TT last weekend. Mostly flat with a couple rollers and some wind. Three members of my club who raced have PowerTaps and are really, really into the data. Out of the 3, the guy that had the best time had, by far, the best TT setup (Scott TT bike, deep wheels, helmet, skinsuit, professional fit, etc.). The next fastest had the same body weight and a higher average power output, but was still down by about a minute. He had a full TT setup but not quite as high end. The third guy was lighter by a kilo or so than either of the other 2 guys and produced more power then either of them, but came in a couple minutes down. He had a road bike with clip ons, and an aero helmet.

It's obviously not a controlled scientific test, but it sure convinced them of the benefits of being aero.

Yup. I can beat people in TT's because i'm *that* much more aero on my bike and with helmet/skinsuit/etc. Even if I can only average 260W (just a number, not real neccessarily), if I lose 10-15W of resistance from my skinsuit, 2-3W from my shoe covers, 30W from my wheels, 10-15W from my helmet, and (a total guess) 40W from my position.... That's somewhere in the neighborhood of 100W. That's absurd.

Three things matter during a TT: the engine (most important still), Aerodynamics, and pacing. Number 1 is hard to change (in a short time, obviously in a long time, it's the cheapest and most effective to change). Numbers 2 and 3, however, with the right equipment (TT bike, power meter), can make you overcome (to some extent) your losses in power output.

Last September I did a 10-mile TT on a road bike with aero bars, 30mm wheels, aero helmet, skin suit, shoe covers, and no gloves. I finished in 22:05 at an average of 308 watts.

Last week I did the same 10-mile TT with very similar weather conditions on a TT bike, Zipp wheels, aero helmet, skin suit, shoe covers, and no gloves. I was very tired from the previous week of training, had a horrible time generating any power, and actually threw up on myself about 5 minutes into the TT. I finished in 21:50 at an average of 286 watts.

I strongly believe that what allowed me to finish in less time with fewer watts was better body aerodynamics due to the geometry of the TT frame.

--Steve

on a TT bike

Zimbo,

I think I read on you website a while back that you got one of those $995 specials from BD. How do you like it? Any regrets not getting one of the $1495 Cervelo Duals or maybe the low end Felts? Been looking at it and wonder if its worth it to go for the more expensive or just get the cheapo and spend the rest on wheels.

Thanks,

Reading all this I feel that I'll be hosed up at Cascade with my clip ons and Zipp 303's, even if I can put out 330-340 Watts for the TT. I will have a skin suit, aero helmet, no gloves and shoe covers though. :)

On my road bike, my seat to handlebar drop is about 9cm, so I think that even with clip ons I can get into a fairly aero position. What is the typical saddle to bar drop for a TT bike?

What other differences between the 2 geometries effect aerodynamics?
Seat tube angle? (Can adjust seat to compensate)
Wheelbase? (Can't do anything about that)
Anything else?

You'll be fine. My drop's only 13cm, and most people you're racing will likely be in a similar position (unless you race cat 3 or higher). I wouldn't mess with other parts of your bike, it's hard to get it set back in your happy place without messing stuff up.

Any regrets not getting one of the $1495 Cervelo Duals or maybe the low end Felts? Been looking at it and wonder if its worth it to go for the more expensive or just get the cheapo and spend the rest on wheels.

No regrets whatsoever. I opted to spend $995 on the bike and buy used Zipp wheels.

--Steve

You'll be fine. My drop's only 13cm, and most people you're racing will likely be in a similar position (unless you race cat 3 or higher). I wouldn't mess with other parts of your bike, it's hard to get it set back in your happy place without messing stuff up.

He does.

You'll be fine. My drop's only 13cm, and most people you're racing will likely be in a similar position (unless you race cat 3 or higher). I wouldn't mess with other parts of your bike, it's hard to get it set back in your happy place without messing stuff up.

I'm Cat 2, but I'll do stage races as a Master until I get a real TT bike. I think I'd be embarrassed going against the Pro/1/2 guys in an NRC race with clip ons. In the Masters (Cat 1-4) there will be the full range from guys with no aero equipment at all to guys with full pro set-ups.

Just track down a used Felt or something on Craigslist. Should be able to get one fairly cheap, and their frames are great for the money.