I give up.......

The cutout is not there just for aerodynamics,it allows the frame to have shorter chainstays while using aero tubing,shorter chainstays might cause bad shifting but allow the rear tire to be closer underneath the rider,this is good with a lot of weight being applied the the front tire because of aerobar use

So, well executed rear wheel cut-outs are slightly faster, poorly executed ones are slower, and having the wheel close to a poorly done cut-out can slow you down... this is news?

Big deal. Seems pretty intuitively obvious to me.

You might also note that John doesn't actually say he tested a cutout in this particular test - he tested a "tube shape leading into a cutout." When he mentions that he turned the tube around backwards and it ran faster, it indicates to me that he wasn't testing a cutout, but an aero-tube. This is useful info, but how does one use it effectively?

Methodology is everything in these sorts of tests, and there isn't nearly enough information in this quote to draw any kind of conclusions - which is pretty common in JC quotes, and which makes sense: why would John want to give useful info away for free to his competition?

MH

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
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FOUR SECONDS!! That's it, life as we know it is going to grind to a halt.

Can I ask the question - who really cares about this sort of stuff?

In the World Championships in the ITT, for the very top riders in the world, who's livelyhood is based on performance, yes, this may be a critical issue. But in triathlon, where the bike makes up just one third of the event, why is so much time devoted to debating/discussing these aerodynamic details.

I love standing at the exit of T1 in a big triathlon. I see all manner of bikes tricked out with the latest and most expensive aero-gear, but the rider is positioned on the bike like a parachute and usually has clothing flapping in the breeze adding to the reverse umbrella profile!

But those four seconds for the wheel gap - I suspect is still critical!!

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Steve Fleck @stevefleck | Blog

Fleck some of us are not tri-guys but time trialers,yea four seconds,if even correct will not matter much,but some of us do not have kids,so we talk bikes,So why are you wasting your time replying??

Looking specifically at the P2K vs the P3- their cutouts are radically different, yet the rear-center is the same on both bikes. Granted you couldn't get that short a rear-center with no cutout and an aero tube, but the cutout on the P3 is clearly intended to be more aero than the cutout on the P2K, as it offers no advantage in rear-center distance.

Comparing the aero data on Cervelo's website, the P3 is claimed to be 29 seconds faster per 40k than the P2K (cat1 rider, excellent position) and 1:14 faster per 40k than the Cervelo One. I agree with others that in the grand scheme of things these savings are relatively small in the context of a triathlon (I can surely find ways to waste more time than this in transitions) but this is not insignificant if you're battling for an AG title or a Kona spot.

I think that the conclusion of Cervelo's tech article sums it up pretty nicely, actually:

Conclusion
As was already indicated in Jim Martin’s article, considerable time savings can be obtained through the use of aeroframes. However, it is even more important to ride in an aerodynamic body position. Therefore, when choosing a frame, one should look at the geometry as well as aerodynamic characteristics of a frame.

Randall,

My apologies. I do know that there are more than just triathletes here.

I reply becuase of the irony that I see out there amongst traithletes, which I will state again: Large amounts of money spent on aerodynamic do-dads, but very little work/effort/time put into dialing the the things that really count when it comes to aerodynamics: positioning and clothing.

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Steve Fleck @stevefleck | Blog

Fleck no apologies needed,i agree its all about the engine,here in Tallahassee i have tried to get a few guys to come out for a weekly 7 mile tt but have had no sucess,I just wish i did not get caught up i all of the aero stuff,my fastest time were still set on a round tubed frame i built in 1987

Any triathlete who is serious about improving their cycling performance should be going to bike time-trials on a regular basis. I am still surprised that this outstanding training opportunity is not used to a greater degree.

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Steve Fleck @stevefleck | Blog

Fleck,

this irony is rampant throughout our culture. Just another quick example is people spending >500 bucks on a golf driver that they won't even use 18 times in a round of golf and that will hit the ball 4 yards farther. People in general (including me) love to spend money. too bad I don't have enough to buy everything I want.

It is interesting thogh

no kidding, it is a great opportunity for advancing their bike splits, I wrote and article on it here: http://timetrial.org/triathletes.htm

The difference between the P3 and P2K may also be related to the aero seatstays. Just a thought.

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I don't work here, I just live here

   

Just returned from my 7 mile tt i try to do on Thursdays After sending emails and making phone calls i was the only one to show,WHEN will i learn,people do not want to hurt but will spent $500.00 bucks to go four secounds faster

"i was the only one to show"

You're making me feel really guilty. Our roadie group, which is about a third tri-geeks, was doing a TT on early Sunday morning. I woke up and noted it was raining so went back to bed.

Of course I live a half hour away. It was bright and sunny there even if it was p*ssing rain in my backyard.

The rear wheel cutout is one small part of the overall bicycle system. I expect my TT bike to have lots of small improvements that add up to something big. Even if it only 4 seconds, why give those 4 seconds away?

I think of all the things you can do to go faster without actually training as free speed. Here's my equation for free speed:

Free speed = internal cable routing + rear wheel cutout + aero tubing + aero seatpost + aero fork + aero bars + aero wheels + 170 PSI Conti GP tubulars + shaved legs + aero helmet + skinsuit + perfect position + bike that handles well with me in my perfect position + perfect tune-up + proper gear ratios

Anyway, maybe there are a couple of other secrets I left off, but you get the idea. . . Why not dial in the details? Most of them are not that expensive and they all make you go faster for no effort.

Fortunately for the young but poor bucks out there, all of those changes to the machine don't have much to do with the motor. If you can cruise at 400 watts you will wail on any bike and certainly blow by 99.9% of the riders out there.

The problem is some of these things only help at speed(not 15 mph) then you wear a floppy jersey or jacket with straps sticking everwhere on your shoes then the biggest watering system,even the extra strap on you helmet, and the seat bag for your spare tubes,or maybe even carry a spare tubular,Great buy the fast stuff i sure have but train your ass off also.

I hear what you are saying, but what I often see is people going for 2/3 of your list of details, then doing something else, bad positioning, bad clothing choices, etc . . that essentiually negates all the other gains to the point of why bother with all the funky aero stuff.

However, you are right to say that if you are going to go in that direction you should go all the way, particularly with the REALLY importortant things: Body position, Wheels and clothes

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Steve Fleck @stevefleck | Blog

It's unfortunate, but thjat 15 - 20 minutes of TT "hurt" is probably going to do more for their triathlon cycling performance than anything else they will do. I am still mystifyed why this reasource is not tapped into by many triathletes.

In my prime, years ago my bike training through the late spring and summer consisted of the following: A long hard group or solo ride on the weekend. A 10 mile or 20 mile ITT on thursday nights and one other bike work out - usually a choice of intervals, hills or a tempo ride. That's it - three workouts a week and a total of abpout 150 miles/week. Result: 5:00 flat Ironman bike splits and under 1:00 40K times for Olympic distance triathlons. I am still of the belief, that the key workout was the all-out once a week TT.

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Steve Fleck @stevefleck | Blog

Fleck and all, I also agree with what's being said- essentially that the engine is more important than the bike. What I don't get is that every time someone posts a question/comment about the "aero"ness of something, there is a backlash to the effect of "if you worried about the engine as much as you worried about the bike you'd be faster". The implication that anyone that is concerned about being aero is just lazy and is looking for a shortcut bothers me. Can't we just assume for a moment that the person asking the question is already working the engine and is looking for additional advantage via smart equipment setup- and just answer the equipment question?

Simple observation. Go to a local midweek evening 10 or 25 mile TT and see how many of the local triathletes are out there? Not many in my case, which is a shame 'cos I could do with less competition, those darn cyclists are just too fast!
SteveMc

In Tallahassee Fl the tri guys were always the one you could count on to be there, The Cyclists ( myself)then a few years ago nobody, i thought tris must have died,but then a woman tri club pres did a weekly tt and it was almost all tri people( i only got to do one fell and broke collarbone)The cyclists in this town will not come or even compete in the state championships,Right now i am so mad at this very thing i could go on a real long rant.

Interesting that your observations are completely different to my own. Even though I'm UK based, and the difference between the old school cycling community and the brash triathletes is possibly greater, I'm very much of the opinion that most triathletes don't know how to time trial well. I think there are three main areas: peddling technqiue, gear selection and position WHILE remaining focused and powerfull over the distance. Time trialists have learnt from experience how to get the most out of their bodies, shaving seconds off a 10 miler (or minutes off a 100 miler) is their goal. A flash bike won't give you that knowledge or training benefit. The one triathlete who seems to be aware of these aspects is Natasha Badmann 'cos she has sussed out Hawaii (which does have a very TT like bike course). [The pro-men are racing each other so theirs is a different story]
Racing aside, the training benefit of hammering at a high intensity, trying to catch someone in front before the the guy behind comes flying past is exactly what you need come race season. None of this semi-drafting ding donging that goes around in every triathlon, just you and the clock... for 50p why don't more triathletes do it?
SteveMc

Stevemc please get a soup box and tell the world,i have invited/emailed/called,everything but beg a few guys to come out but no show,some in this town do a Wednesday night ride so they will not do a hard effort before but then will not do one after,i am training for USCF state champs and its always good to have a group of people to Time trial with,some to clase some to try to keep from getting caught.I bet from the 50 uscf cyclists in this town three will go to our state tt race,and no tri people will go,and its less than 3 hour drive(great in florida)I give up!