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Re: Trek TTX is Faster Than the P3C [Rappstar] [ In reply to ]
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ETTX (and SSL variant, for that matter) to original TTX...relative to the bold stuff anyway.

There used to be a nice "side by side" (top and bottom, really) picture of the two right here...tried calling it up last night and the pix weren't there anymore. Odd, since one of them was mine. Maybe you can resurrect?

Carl

Carl Matson
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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...even the Kestrel KM40 (not the Airfoil, due to tube shapes)...
Funny, I noticed the same thing about the KM40 vs. the Airfoil. I'd only ever seen a KM40 until Interbike, and I was suprised that the downtube of the Airfoil Pro seems to be much worse with some hard angles and a relatively wide "flat spot" running down the middle. Wonder if they sacrificed aero for stiffness...

Have you tested your Softride vs. a P3C? Just curious to hear what you found. I'd also like to see someone resurrect a Zipp frame and test that, as they certainly seem to be better executed beam bikes than the Softrides in terms of aerodynamics.

the CAT Cheetah, I've heard, is also one of those bikes that people love to love, but that doesn't actually do as well as people think. The only "test" I've ever seen is the TOUR velodrome test, which I don't put much stock in. Lotus, no doubt. Corima's wheels are nothing special in terms of aero, and I've never see any data on the Fox, so I don't know. A lot of these are the bikes that people believe must be fast. But I'm not sure how many (except the Zipp & Lotus, where I've heard confirmed numbers) actually are really special.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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The Zipp 2001/3001, Lotus, Cat Cheetah, Corima Fox, Softride, and even the Kestrel KM40 (not the Airfoil, due to tube shapes) all bring something special to the table that just can't be replicated under UCI rules. I am not saying that every one of these bikes is faster than a P3C, but I know some of them are

And you know this how?
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Re: Trek TTX is Faster Than the P3C [Carl] [ In reply to ]
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ETTX (and SSL variant, for that matter) to original TTX...relative to the bold stuff anyway.

There used to be a nice "side by side" (top and bottom, really) picture of the two right here...tried calling it up last night and the pix weren't there anymore. Odd, since one of them was mine. Maybe you can resurrect?

Carl
These:



"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Trek TTX is Faster Than the P3C [Rappstar] [ In reply to ]
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yes...those exact red X's.


weird...that it would happen to me on both my home and work computers. were it one or the other the explanation would be easier. I'm assuming everyone else can see those as actual pix...?


Carl

Carl Matson
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Re: Trek TTX is Faster Than the P3C [Andrew Coggan] [ In reply to ]
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Thanks for the response. What I am gettting at is: Let's say at 30mph you have your rider and and your smoke gun and you see perfect airflow from their shoulders down to their butt. If you then slow down to 18mph and the airflow is the same, I agree with your linear relationship. But if at 18mph the airflow breaks off mid way down the riders back, wouldn't that negate the linear relationship?
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Re: Trek TTX is Faster Than the P3C [sdmike] [ In reply to ]
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Thanks for the response. What I am gettting at is: Let's say at 30mph you have your rider and and your smoke gun and you see perfect airflow from their shoulders down to their butt. If you then slow down to 18mph and the airflow is the same, I agree with your linear relationship. But if at 18mph the airflow breaks off mid way down the riders back, wouldn't that negate the linear relationship?
Except, were air to break off the riders back at one speed and not the other, it would happen at 30mph, not 18mph. Really, though, the Reynolds numbers of the flows are within the same regime. People have this idea that 20mph and 30mph are totally different worlds. Physically, they are not. 300mph and 30mph are very different. But 30mph vs. 20mph, the flow is basically identical. And any increased turbulence (which would cause separation) would occur at the higher speeds, not slower.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Trek TTX is Faster Than the P3C [Rappstar] [ In reply to ]
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Thanks for helping me through my mental block. ;)
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Re: Trek TTX is Faster Than the P3C [Rappstar] [ In reply to ]
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"People have this idea that 20mph and 30mph are totally different worlds."

Nothing like a little myopia, eh?
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Re: Trek TTX is Faster Than the P3C [Andrew Coggan] [ In reply to ]
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Because I've tested every one of the bikes I mentioned except the Cat Cheetah and Lotus on the same track under the same conditions with the same (and different) position/wheels/aerobars/etc. The numbers are obviously only good for me and are dependent upon my body, flexibility, riding style, etc. I have held and measured a Cheetah though, and it's every bit as well designed as the Fox in most parts, and better in several.

The order of performance has been:

1. Zipp 2001 (this was/is not mine unfortunately)
2. Softride Rocket TT w/ custom internal cable routing and fairing to fill the poorly executed area in front of the rear-brake and some work around the beam joint. A Bonty speedbottle works really well there.
3. Corima Fox - I had to do a lot of work to get this to fit me reasonably well. It was really too small for my leg length although the TT length was fine. Had to build a custom seatpost to acheive proper seat height and angle.
4. Kestrel KM40 (despite it's lower level of aero performance, this is a fast and comfortable bike that I prefer to ride most of the time)
5. Aegis Trident

Some of the ordering on the lower end (3, 4, 5 changes with different wheelsets. The KM-40 specifically does better than the other two with Nimble Crosswinds).

Now obviously I am not working with Trek or Cervelo's funding and I have constrained myself to bicycles that use 650c wheels, but I suspect there aren't more than two or three non-professional fitters/aerodynamics folks out there who spend more time testing than I do. I am working with minimal wattage that doesn't seem to improve that much with training, so the application of my brain is all I've got.

Chris
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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On the track, as in 0° yaw?
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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I have never seen an independent test that shows any of those bikes to be faster than a P3C, and certainly none of our internal tests do (and we don't really have a reason to fudge our internal tests, but of course that you can't verify that). As for pedaling, it has a very small effect, simply because the velocity of the foot is only around 10% of the air velocity. The velocity of the rest of the leg is even less. It certainly would be possible, though quite difficult, to make an articulated mannequin. and it would likely affect the aerodynamic similarities because those joints then need to be covered, etc, etc.

And you do realize that when people test a live rider with pedaling legs, he is not actually pedaling at normal speeds, so it's not the ultimate either. But when the whole bike industry does tests without riders or nonsensical tests with riders that can't repeat their position accurately, I am pretty happy that we develop a method that is over10x more accurate than the live rider method.

As an example for UCI-illegal bikes that don't benefit from this, if I take a KM40, I can improve the aerodynamics by adding a well designed seattube (we have actually done stuff like that, just for fun). Bottomline, the downtube can aide the flow off the front wheel (though not many do), the seattube can aide the flow over the rear wheel (again not many do), the toptube is great structurally without much drag (and taking it out requires the downtube to be larger), removing the seatstays sounds nice until you see how big the chainstays have to become to take the load. There really aren't very many things that make sense to do differently if you toss out the rules. And certainly nobody will make a non-UCI legal bike that is more aero than a UCI-legal Cervelo, simply because the potential gains aren't there. And frankly, because we can afford to spend much more effort on research than anybody else, simply because triathlon is a much more important market for us than for the other companies. And we can do that on a legal or illegal bike, that makes no difference. CSC is certainly not holding us back from making an illegal bike, I wouldn't know why.

I hope this explains our reasoning a little bit, gotta get back to work now.


Gerard Vroomen
3T.bike
OPEN cycle
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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Because I've tested every one of the bikes I mentioned except the Cat Cheetah and Lotus on the same track under the same conditions with the same (and different) position/wheels/aerobars/etc. The numbers are obviously only good for me and are dependent upon my body, flexibility, riding style, etc. I have held and measured a Cheetah though, and it's every bit as well designed as the Fox in most parts, and better in several.

The order of performance has been:

1. Zipp 2001 (this was/is not mine unfortunately)
2. Softride Rocket TT w/ custom internal cable routing and fairing to fill the poorly executed area in front of the rear-brake and some work around the beam joint. A Bonty speedbottle works really well there.
3. Corima Fox - I had to do a lot of work to get this to fit me reasonably well. It was really too small for my leg length although the TT length was fine. Had to build a custom seatpost to acheive proper seat height and angle.
4. Kestrel KM40 (despite it's lower level of aero performance, this is a fast and comfortable bike that I prefer to ride most of the time)
5. Aegis Trident

Some of the ordering on the lower end (3, 4, 5 changes with different wheelsets. The KM-40 specifically does better than the other two with Nimble Crosswinds).

Now obviously I am not working with Trek or Cervelo's funding and I have constrained myself to bicycles that use 650c wheels, but I suspect there aren't more than two or three non-professional fitters/aerodynamics folks out there who spend more time testing than I do. I am working with minimal wattage that doesn't seem to improve that much with training, so the application of my brain is all I've got.

Chris

But your assertion was that one or more of these bikes is more aerodynamic than a P3C, yet you apparently haven't tested the latter. So again I ask: how do you know that the P3C isn't the fastest of all?

BTW, I wouldn't describe the Fox as "well designed", as it is common knowledge that it performs very poorly from an aerodynamic perspective...
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Re: Trek TTX is Faster Than the P3C [Andrew Coggan] [ In reply to ]
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Felt testing put the Lotus, Zipp, and Felt DA all ahead of the P3C. I don't recall all of the details, but at the very least those 3 were mentioned. We've been down this road before and dug up the relevant posts by SuperDave etc.

I haven't tested any 700c bicycles because I don't have any 700c aero wheels, and because there aren't any of those bicycles around here to borrow unfortunately. I am hoping to test a P2 eventually, but my attempts to purchase one have so far been unsuccessful.

Anyway, just to put my money where my mouth is (one is bigger/more plentiful than the other, but whaddaya gonna do?), I will happily transport myself and my Softride to the SD LSWT and pay for my own tunnel time during a "Cervelo Week" if they will provide a P3C for me to compare to.

Chris
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Re: Trek TTX is Faster Than the P3C [Tom A.] [ In reply to ]
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They've re-worked the front end a bit... wider fork baldes, fork crown is much different, and the downtube comes closer tothe front wheel.

*
The Dude abides.
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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But of the three bikes you just listed (Felt, Lotus, Zipp), only two were on your original list, and then you added a bunch of bikes that don't have anywhere near the credibility of the two that were (Zipp, Lotus). And, both the Lotus and Zipp are not-UCI legal, but for entirely different reasons, basically negating the idea that there is a common UCI-illegal design that is faster. The Felt DA is UCI-legal, and so is the Walser, and both of those are also at the top of the heap. So of the maybe five fastest bikes - Zipp, Lotus, Felt, Walser, Cervelo - three of the five are UCI-legal. Add in the Trek, which got this whole thread started, and you have four of the six. So where is the compulsion to design a UCI-illegal frame?

And, to Dr. Coggan's point, you've not tested a P3C (or even a P3), yet both of those bikes ARE readily available in 650c sizes (though not your size?).

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Trek TTX is Faster Than the P3C [gerard] [ In reply to ]
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I appreciate the time it took for you to reply and the information contained therein. The fact that you have not had any illegal frame test faster than a P3C during internal tests sounds interesting, but I remain skeptical given that you've not listed what has actually been tested.

If you can tell me that you've tested Lotus, Big Mig's hour record Pinarello, Ulle/Riis Pinarello from 1997 TDF, GT Superbike I & II, Obree's Old Faithful (frame, not the position), BMC TT01, Softride FASTT, Carbonsports Total Eclipse, then I am inclined to believe you. I don't think that is a claim you can make, and despite the amount of time, energy, and money you've put into the SD LSWT to develop your bikes, I believe your research applied to some alternative tube schemes would result in something truly impressive.

I am willing to be wrong, so tell me I am.

Chris
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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Felt testing put the Lotus, Zipp, and Felt DA all ahead of the P3C. I don't recall all of the details, but at the very least those 3 were mentioned.

http://forum.slowtwitch.com/...post=1516581#1516581

:-)

BTW, in the independent testing conducted for Project 96, the Lotus finished dead-last among the aero bikes, whereas IIRC the Hooker (which in my hands is slower than the P3C) bested the Zipp 2001. Now there very well could be some reasons other than just random error for this reshuffling, but my point is that I don't think you can necessarily rely on cross "study" comparisons that don't even include all of the bikes in question to draw really firm conclusions.
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Re: Trek TTX is Faster Than the P3C [Large] [ In reply to ]
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Coming from a gov't economist, nice use of "ceteris paribis!" A better translation would be, "all else being equal" but you got the idea of it.
In grad school, I had the good fortune of getting the noted economist Jagdish Bhagwati as the professor for one of my econ courses. With his Indian accent, it sounded like he was saying "get her asparagus." It took us days to figure out what he was talking about. Great course, though, and this is coming from someone who is abysmal in economics.
[OT]....Not sure who the gov't economist is, but it's neither ceteris paribas, nor ceteris paribis...I like asparagus which comes closest
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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Big Mig's hour record Pinarello, Ulle/Riis Pinarello from 1997 TDF, , Carbonsports Total Eclipse,
I don't see that they need to bother testing those - the carbonsports looks like a brick wall with a bike behind it - the HT is so wide and the cable stops are mounted on the side. The Pinas were chunky too, the Sword always looked like a bad copy of the Zipp - if Pina had been able to make a good bike before the rules changed then I'd expect them to have something good once the restrictions came in. As Gerard has said before - what evidence is there to suggest that a company that can't make a fast legal bike will be able to make a faster illegal one. Rather like the weight limit - everyone can make make a bike that is under it but not everyone can make a bike that is under 6.8 and safe/durable/nice riding.
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Re: Trek TTX is Faster Than the P3C [Rappstar] [ In reply to ]
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No, I can't score a P3C or Felt 650c in my size, since I have a 36.5" inseam. P2 classic and P3 alu are both options, but given that Cervelo asserts that the P2C is faster than the P3 alu, I didn't think it was worth bothering with that one. I am still intending to put a P2 classic through it's paces vs. the Softride.

I am in no way asserting that Cervelo isn't doing their homework or working tirelessly to create some beautifully aero bikes. I also don't believe the TTX design is faster (though maybe in the same range) they are clearly both using a lot of FEA and CFD as well as tunnel time to develop the bikes. What I don't like is discounting entire designs based on poor implementations of a core idea (like removing tubes). With the advances in carbon over the past 10 years, certainly a narrower, better shaped softride/zipp could be constructed using the expertise of Cervelo's engineers.

Chris
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Re: Trek TTX is Faster Than the P3C [zebragonzo] [ In reply to ]
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No, I test on a 3/8 mile auto race track. Very windy most of the day, but calm in the morning. I test with wind direction/speed, temp, humidity, etc all being recorded at 5 second intervals on my laptop. It's good to have an in with the physics department where I went to high school.

Chris
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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No, I can't score a P3C or Felt 650c in my size, since I have a 36.5" inseam. P2 classic and P3 alu are both options, but given that Cervelo asserts that the P2C is faster than the P3 alu, I didn't think it was worth bothering with that one. I am still intending to put a P2 classic through it's paces vs. the Softride.

I am in no way asserting that Cervelo isn't doing their homework or working tirelessly to create some beautifully aero bikes. I also don't believe the TTX design is faster (though maybe in the same range) they are clearly both using a lot of FEA and CFD as well as tunnel time to develop the bikes. What I don't like is discounting entire designs based on poor implementations of a core idea (like removing tubes). With the advances in carbon over the past 10 years, certainly a narrower, better shaped softride/zipp could be constructed using the expertise of Cervelo's engineers.

Chris
Except, and I'll agree with Gerard here just on aero principles - a well designed seattube should be more aerodynamic than having a the leading edge be your wheel. You have much more control over the shape, and it isn't moving, and tire choice won't make any difference. So I don't see that a beam bike actually is (or even should be) better.

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp
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Re: Trek TTX is Faster Than the P3C [chicanery] [ In reply to ]
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I am still intending to put a P2 classic through it's paces vs. the Softride.

Just a note that Endurosport in Toronto still has a limited selection of classic Cervelo P2 frames( all 650c wheel size) in stock that can be built up ala cart with any gruppo you want. This is the frame/bike that first put Cervelo on the map. Call 416.449.0432 and ask to speak to Dan or Peter for more details.


Steve Fleck @stevefleck | Blog
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Re: Trek TTX is Faster Than the P3C [Fleck] [ In reply to ]
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That is who I have been trying to get one from for ages. It just doesn't seem to happen. You gave me the tip originally, so thanks for that.

Chris
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