I’ve got a LBS trying to get me into the QR Seduz vs. the K-Factor as a first Tri Bike because of the more aero frame. However, I’ve been told by a friend and experienced triathlete that wheels and helmets have a bigger impact on aerodynamics than frame. Can someone point me to literature…or a thread that has plenty of pontifications on this subject? Grazie
You’ve basically thrown a steak into a pirhanna tank with this one. Plenty of threads on this topic if you search, but that won’t stop people from responding. I’m with you - wheels and helmet are more important, and any aero features behind the rider (which blocks their effect) aren’t worth paying money for. I, however, am in the distinct minority. If you are short on cash, spend it on other things than a super-aero frame.
I know I’m being lazy, just don’t have the time to search. If someone is willing to give me the down and dirty, cool.
I’ll bite.
An aero frame is faster than a non aero (round frame). This holds true for each and every tube on the bike. Stick a rider on the bike, and the advantage of aero shaped seat stays are virtually negated.|Forks and down tube are the most obvious bits that need to be aero profiled, along with the base bar of your cockpit, as these hit the wind first.
The drag reduction of an aero frame compared to a round tube frame is minimal at best. Especially compared to the huge ( in comparison) drag reductions from disc, aero, or trispoke wheels. Aero helmets also reduce drag by a more substantial amount than frame tube profiling
can o worms now opened
Let me interject one thought. What is an aero frame, and does the Seduza meet the criteria?
aero helmet, and aero wheels have a bigger impact, than getting an aero frame… but aero frames are sexy
Don’t fret the minutiae. Only once you’re pulling seriously top percentage splits will you start to get upset over having a non-aero frame (and even then, only if you already have all the other aero gear and lost on a prize by a few seconds!). Its benefits are really small and I’m sure that wheels/helmet would be better (benefits more significant, but still not enough to overcome a great training plan vs a decent one). Even then, I have a “$1500” bike and still beat almost everyone with a $30 helmet and a tri bike, but no aero wheels or anything else spectacular.
If it helps you sleep better, spend a couple bucks on it, but if it’s any real money, put it toward a helmet, which can be bought for way less than $200 and has a demonstrable time savings or, if it’s way more than that, drop it into wheels.
Look at the picture from the front of a triathlete and you’ll see that the frame represents a really minimal air signature. Most is rider, and even the parts that are frame will not be all that much saved with the frame particulars. A circle is, afterall, a pretty aerodynamic shape to begin with.
A circle is, afterall, a pretty aerodynamic shape to begin with.
By circle I’m assuming you mean cylinder. And you might want to do some research before you claim a cylinder is a low drag shape…
The K-Factor isn’t exactly a “non-aero” frame. It may be a little less aero than a Seduza but it has rear dropouts so you can snug the rear wheel up behind the seat tube, a nice aero fork, aero seatpost and will allow you a good aero position. The $2100 deal on the 105 equipped k-factor seems like a steal to me. There was another question about this frame recently and a link to the review Tom Demerly wrote about the K-Factor on his site. I don’t think there are many people who would notice a difference in their times riding the Kuota compared to the QR unless the fit was way off (the QR frame will be a more agressive setup).
Let me interject one thought. What is an aero frame, and does the Seduza meet the criteria?
Ah yes, the million dollar question.
The aero-ness of a frame is, for me, defined by two things.
- Does it let the rider adopt an aerodynamic flat backed position?
- Are the frame tubes profiled or otherwise shaped to improve aerodynamics?
Is my P3-SL more aero than my Giant tcr? Yes - according to wind tunnel testing, and by lookng at the tube profiles
Can I measure the difference? No
Can I get a more aero riding position from using it? No.
Was it worth the extra money, on a buck per second of time saved scale? No
But it does look cool
Is my P3-SL more aero than my Giant tcr? Yes - according to wind tunnel testing, and by lookng at the tube profiles
Can I measure the difference? No
You might not be able to, but I can 
Seriously, with a good powermeter and a modicum of care, you should be able to actually detect the a difference.
Was it worth the extra money, on a buck per second of time saved scale? No
That’s a personal decision 
But it does look cool
To tell the truth…from a “looks” standpoint, I’m actually not a big fan of the P3 style seat tube. I know it works great, but I actually prefer the “look” of the P2C seat tube. If only they’d “close up” the gap where the seatstays meet…then again, then it may be just as fast as a P3C
Hmmm…I wonder if I could make a “tool bag” that would fit in that gap…hmmmm…
To answer your points…
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I have not joined the ranks of the power metered up. Basically cos I don’t want an ergomo, a Powertap is not disc compatible ( Don’t tell me about wheel covers, I’m not trading my Mavic disc for a PT and covered wheel) and I can’t afford an SRM yet. Therefore I can’t measure any difference between the two bikes.
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Yes it’s a personal opinion. If I followed any kind of logic regarding this sort of thing I’d never change bikes, wheels etc. Is a Mavic comete worth the extra over a Hed, or X-treme etc?
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I like it, but P3’s and P3c’s are getting far too common. Need to stand out somehow, so I’ll trade for something else. The new Isaac joule aerotic, or a Teschner perhaps?
Mind you, that takes us back to point 2
As for filling the gap on the P2c, I’ve got some balsa wood somewhere
Tom A-
I’m in the same boat for new bike soon, and also thinking of the K-Factor vs. P2/Dual/etc.
In your post, are you suggesting that with a power meter and identical position set-up, you could tell a difference in the frame tube shape in number of watts? If so, what do you think it would be?
And for my information, for the MOP’ers, what are we talking about over 40K, or 112miles? Seconds or minutes (able to quantify?)
I’d think position is most important, helmet/wheels about the same, and tube/frame shape a distant follower, no?
Thanks.
I ride a round-tubed old QR ti frame. A Hed 3 with a CarbonAero fork are my biggest “aero bike” adaptations. It’s the engine. Once you get your position TOTALLY dialed, then I’d say start thinking about the totally molded-to-the-wind aero frames. But that’s just me, and I’m often accused of being an old codger.
In your post, are you suggesting that with a power meter and identical position set-up, you could tell a difference in the frame tube shape in number of watts? If so, what do you think it would be?
Yep…but don’t just believe me, here’s Andy Coggan’s take on it:
http://forum.slowtwitch.com/...earch_engine#1344248
Somewhere in that thread Andy alluded to the fact that he measured his P2T to be .020 - .030 m^2 of CdA higher than his identical position on his old Hooker. This is approximately equivalent to 2 to 3 seconds per km difference. You do the math
He also revealed a short time after that post that in his wind tunnel visit, his wife’s new P3C track frame was the lowest drag frame to grace his household. Sooo…I guess one could surmise that the difference between a P2K type frame and a P3C would be of the same magnitude…and those are some of the more “slippery” frames out there.
In the “specialized transition thread” from last week I linked to a couple of different methods for measuring CdA with a power meter. A simple search would find those. From my experience with those methods, measuring a difference of the magnitude listed above would be pretty easy.
And for my information, for the MOP’ers, what are we talking about over 40K, or 112miles? Seconds or minutes (able to quantify?)
Minutes.
Over 40K, you’re talking 1:20 to 3:00 for the above example. All other things being equal, of course.
I’d think position is most important, helmet/wheels about the same, and tube/frame shape a distant follower, no?
Sounds pretty good. On a “bang for the buck” basis, I’d list the priorities for reducing “resistance to forward motion” as:
- Position/clothing
- Tires
- Helmet
- Wheels
- Frame
- Bars, cranks, brake levers, etc.
A circle is, afterall, a pretty aerodynamic shape to begin with.
By circle I’m assuming you mean cylinder. And you might want to do some research before you claim a cylinder is a low drag shape…
In this context, it is pretty aerodynamic because the numbers clearly tell us that an aero vs non aero doesn’t make a big difference in a time trial. It’s really that simple.
OK, here are some estimations from Martin and Cobb’s article, “Bicycle Frame, Wheels, and Tires,” in High Performance Cycling, edited by Asker E. Jeukendrup (2002, Human Kinetics Press).
They estimate 40K times for a rider putting out 100, 200, 300 and 400 watts. I’ll use the 200W numbers, since that’s probably closest to a typical MOPer.
Here is the comparison for a standard (round tube) frame vs. a semi-aero frame (aero down tube, all else round) vs. a full-aero frame (e.g., they have illustrations of a P3 and a Softride):
67:43 vs. 66:57 vs. 65:39
Standard wheels vs. aero rims (e.g., HED Alps) vs. HED 3s vs. disc/HED 3 front:
67:43 vs. 66:46 vs. 66: 44 vs. 66:32
So, you’re looking at about 2 minutes between best and worst frames. The difference between a Seduza and K-Factor is likely much smaller–how much I wouldn’t hazard a guess.
The drag reduction of an aero frame compared to a round tube frame is minimal at best.
The drag reduction of a well-designed aero frame compared to a round tubed frame can be as much, or more, as a set of aero wheels.
The question is…how many of these well designed frames are there? I can think of 2 from one manufacturer, one from another manufacturer and one more from a third manufacturer.
Other than these, I think wheels, etc. are the better investment.
A circle is, afterall, a pretty aerodynamic shape to begin with.
By circle I’m assuming you mean cylinder. And you might want to do some research before you claim a cylinder is a low drag shape…
In this context, it is pretty aerodynamic because the numbers clearly tell us that an aero vs non aero doesn’t make a big difference in a time trial. It’s really that simple.
See Andrew Coggan’s post in this thread and some other threads where he estimated the wattage savings of a P3Track. If you are referring to the MIT “data” tossed around here, also see the recent posts raising serious questions about the validity of bike testing data from MIT.