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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [cerveloguy] [ In reply to ]
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"So give us one legitimate reason why a cover would not be as fast as any other disc."

How many disc covers does Blackwell sell in a year? What is the price of the Zipp disc they sell versus a $60.00 cover? Same as any company. What "we" sell is the best and that's what you should be racing attitude. That's why I think this debate is crap.

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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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There's no doubt that John and Josh are in the business of selling expensive discs, but i wouldn't go so far as to question their integrity.

I think John's concern with a disc cover would likely be that it must form a tight seal at the outer diameter with the rim otherwise aerodynamics is compromised. However, if this is done, how can it not possibly function like any other disc?

There are minor factors such as weigh and dimples that may add up to a second or two gain. This is important to a pro TT'er looking for that last micro advantage, but to a MOP middle aged AG'er such as myself, the real world gain or the coolness factor is not worth the extra $$$$.
Last edited by: cerveloguy: Jun 29, 07 12:07
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [cerveloguy] [ In reply to ]
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I am not questioning anyones integrity, but I do think we need to see the data if such thoughts are to be believed. Seem fair?
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [cerveloguy] [ In reply to ]
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Also, some authorities have claimed that lenticular is faster than flat. Covers are lenticular.


No they're not. Lenticular means having a lens shape (i.e. double convex), and in a cross-section a lens has curved sides. Covers are instead cone shaped, with straight sides in a cross-section.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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There's a lot of heresay for sure. Hed publishes their data on their website and Zipp gives a good aero explanation on theirs. That German magazine has published their test results. The only test published involving a disc vs cover that I'm aware of is Kraig Willet's.

I'd really like to see more info on frame aerodynamics. If there is any area that needs to come out in the open more it's there.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [duncan] [ In reply to ]
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"Covers are instead cone shaped"

My bad. Thanks for the correction.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [cerveloguy] [ In reply to ]
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OK, here's one reason.. At "0" yaw. a flat disc will have less frontal area than a spoked wheel that has been covered. more frontal area is slower. You are correct that I have said that a disc is a disc and I still generally go by that but, in a hair splitting contest like this, then the covered wheels aren't quite as good, it can be because of ridges where the spokes are, gaps at the hubs or seams that are not quite right. For the money, covers offer a great performance increase, I just don't personally think they are as cool.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [John Cobb] [ In reply to ]
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I just don't personally think they are as cool.

Finally we have an honest and to the point ending to this madness...

As with most AG's bikes... it's all about the coolness factor and not how fast I can go..

I ride a zipp disc and it's cool;-)
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [John Cobb] [ In reply to ]
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No cover will ever sound like a disc either!
Rickeh
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [sjudice] [ In reply to ]
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The data out there making people favor their Xentis wheels was produced by Triathlon magazine in Germany. They did indoor velodrome testing showing that a pair of xentis MK1 on a P3 using an SRM was 3 watts faster than an 404, the next year they went back and did the same test using lots of different wheels. That year the Vuelta Carbon Pro (old 404 rim but with 12 spokes) won the test at -38 watts from baseline with Xentis at -37 watts, 808 at -36 watts and 999 at -29 watts, interestingly the Corima disc/3 spoke came in at -22 watts, Lightweight -27 watts with the Ritchey Carbon (404 rim) and Easton Carbon (404) rim being -28 and -29 watts respectively.

The problem with these tests is that they were done at zero yaw. The press in Germany really treated this as a breakthrough, claiming that discs are actually slower than spoked wheels or composite spoked wheels. The problem is that nobody took into consideration that the test was done on an indoor velodrome. This concept is something we've been trying with no success to sell to the US track program, that at 0-2 or 3 degrees of yaw, the skin friction of the disc makes for higher drag than a good aero wheel, but past 2-3 degrees of yaw, the disc dominates most anything. If you look at the Tour magazine data or any of the zipp published data, you see that this is not some revelation, but exactly what the data has been predicting for years, and for road and tri use this is a non-issue as 0 degree or near 0 degree wind angle is so unbelievably improbable, even on an indoor track a shorter or higher banked track will induce larger effective crosswind angles due to rider lean and stirring of the air by other riders and so on, but in this case they were testing at a rather large/shallow indoor track and actually managed to replicate almost exactly a lot of the low yaw wind tunnel data we have taken over the years. The problem of course is that this was published in a triathlon magazine and not a track racing magazine...

If you look at the Tour magazine data from 2005, you see this predicted almost exactly, they are showing the 808 and xentis both having slightly lower drag than the disc at zero yaw with the xentis ever so slightly winning, but get to 5 degrees and it is not contest anymore and at 10 degree the difference between the disc/808 which are almost identical and the xentis is about 80 grams of drag or roughly 10-11 watts additional to maintain the same speed.

Bottom line is that some creative rim shaping makes a wheel like the 808 faster than a dis at around 0-4 degrees of yaw and again at 8-12 degrees of yaw (as verified in both Zipp and Tour mag data within grams of each other) but past that, the disc kills everything. Cees is right that there is some increase in tire rolling resistance due to increased side loading, but the side loading of the disc at say 20 degrees is about 3800 grams which is considered minor compared to the 40000 grams of vertical load the tire would see with an 80kg bike rider system with 50/50 weight distribution, although nobody has a good way of measuring this, however, at say 20 grams of drag a disc has more than a 100 gram drag advantage over any other wheel, so it would take a lot of RR to offset the gains.

As for covers, the BikeTechReview data has been discussed by a lot of people I know in the industry and there are a few things to be aware of, first the disc used was borrowed from somebody, it is a 1992-1992 Zipp 19mm wide disc with 20mm braking zone that was ground parallel, this is an old technology that was replaced years ago as the lip between the body and brake surface causes considerable drag...construction similar to this is still used by quite a few manufacturers, but is really not ideal. Also, the tire on the wheel was quite used and not the same tire used in the other testing, and was from my understanding rather used as this wheel belonged to somebody. As a result, the data for the real disc is far worse than anything anybody else from Tour magazine to us to John Cobb has ever recreated for even a similar disc much less a modern one, so in that way I think the comparison between the two wheels is a bit misleading in that particular test. Also, the disc cover wheel used was a very meticulously constructed and maintained wheel with very nicely sealed edges and no apparent blend problems between rim and skin. This test does show that a cover can make for a very efficient wheel, but having said that, there are two issues people always overlook with covers. First, a cover is not lenticular, it is conical, not that is affects the data too much, but the conical wheel tends to have both more surface area and more frontal area than a lens or flat disc, so at lower yaw angles the performance suffers. At higher angles the wheel performance is entirely dependant on the care taken in assembly, as I said with the original Zipp disc construction and the construction of most clincher and even some modern tuby discs, a 0.030" (0.75mm) step at the skin/rim interface will cost you 6 watts or possibly more. So while a cover can be made quite fast my experience is that almost all of the ones I see in IM pits and such are not constructed or maintainted to their potential. As someone who used to use and manufacture covers before I worked for Zipp I can tell you that I used to spend hours before every event tweaking and maintaining the thing to get it just right, the best is to permanently silicone bead the one half to the rim using C clamps and wood blocks to get the surfaces exactly flush...the other side really should have a valve hole cut in it and do the same for it's asembly as taking the thing on/off can really throw the alignment out and create discontinuous surfaces, I had a coach that drilled all of this into us as juniors without any data, but I can now say after having spent hundreds of hours in the wind tunnel that he was spot on.

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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [John Cobb] [ In reply to ]
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"I just don't personally think they are as cool. "

Now the real reason!!

I can't certainly argue with that point, your wheels are cool. But wouldn't it be cool to see somebody at the local tri on an old bianchi 12 speed with a disc cover smoke the field. Saw a woman win her AG this way one time. Now that was really cool.

Performance wise there is little doubt a disc is a disc is a disc. And that includes covers. We're grasping for straws mentioning the things you did.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [joshatzipp] [ In reply to ]
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"So while a cover can be made quite fast my experience is that almost all of the ones I see in IM pits and such are not constructed or maintainted to their potential."

I brought those points up in my previous posts. If it isn't fitted correctly then maximum aero advantage is lost. I'm not an engineer but that's just common sense. I was always quite meticulous when fitting mine.

BTW, although I've been a staunch defender of covers and like to keep you industry guys honest about this, I actually owned a "real" disc as well for my P2K. An older 650c Spengle (later became Xentis) that I paid $100. for on ebay.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [sentania] [ In reply to ]
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"My opinion is that when comparing "race wheels" to "race wheels" no matter the manufactuer you are talking seconds over the course of an Ironman, whereas "training wheels" to "race wheels" is minutes."
- - Precisely. I could spend the megabucks for the Zedtech 999 w/ceramic bearings and shave 90 seconds off my IM time, but that still won't fix my problem, because it's under the hood - just not enough horsepower coming from the engine room.


Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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"there is very little difference in any of the similar wheels (size, shape) from each manufacturer."
- - Very true. Christopher Kautz talked me out of dumping my old HED Cx in favor of an H3, because he said I'd gain 8-10 seconds over 40K. I've never been beaten by 8-10 seconds.

"Same thing for a disc versus a 80/90/100 rear wheel."
- - Big error there. The primary advantage of a disc is the reduced egg-beater turbulance from spokes passing the seat and chain stays. No way a spoked wheel can get close.


Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [joshatzipp] [ In reply to ]
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In Reply To:
The data out there making people favor their Xentis wheels was produced by Triathlon magazine in Germany. They did indoor velodrome testing showing that a pair of xentis MK1 on a P3 using an SRM was 3 watts faster than an 404, the next year they went back and did the same test using lots of different wheels. That year the Vuelta Carbon Pro (old 404 rim but with 12 spokes) won the test at -38 watts from baseline with Xentis at -37 watts, 808 at -36 watts and 999 at -29 watts, interestingly the Corima disc/3 spoke came in at -22 watts, Lightweight -27 watts with the Ritchey Carbon (404 rim) and Easton Carbon (404) rim being -28 and -29 watts respectively.

The problem with these tests is that they were done at zero yaw. The press in Germany really treated this as a breakthrough, claiming that discs are actually slower than spoked wheels or composite spoked wheels. The problem is that nobody took into consideration that the test was done on an indoor velodrome. This concept is something we've been trying with no success to sell to the US track program, that at 0-2 or 3 degrees of yaw, the skin friction of the disc makes for higher drag than a good aero wheel, but past 2-3 degrees of yaw, the disc dominates most anything. If you look at the Tour magazine data or any of the zipp published data, you see that this is not some revelation, but exactly what the data has been predicting for years, and for road and tri use this is a non-issue as 0 degree or near 0 degree wind angle is so unbelievably improbable, even on an indoor track a shorter or higher banked track will induce larger effective crosswind angles due to rider lean and stirring of the air by other riders and so on, but in this case they were testing at a rather large/shallow indoor track and actually managed to replicate almost exactly a lot of the low yaw wind tunnel data we have taken over the years. The problem of course is that this was published in a triathlon magazine and not a track racing magazine...

If you look at the Tour magazine data from 2005, you see this predicted almost exactly, they are showing the 808 and xentis both having slightly lower drag than the disc at zero yaw with the xentis ever so slightly winning, but get to 5 degrees and it is not contest anymore and at 10 degree the difference between the disc/808 which are almost identical and the xentis is about 80 grams of drag or roughly 10-11 watts additional to maintain the same speed.

Bottom line is that some creative rim shaping makes a wheel like the 808 faster than a dis at around 0-4 degrees of yaw and again at 8-12 degrees of yaw (as verified in both Zipp and Tour mag data within grams of each other) but past that, the disc kills everything. Cees is right that there is some increase in tire rolling resistance due to increased side loading, but the side loading of the disc at say 20 degrees is about 3800 grams which is considered minor compared to the 40000 grams of vertical load the tire would see with an 80kg bike rider system with 50/50 weight distribution, although nobody has a good way of measuring this, however, at say 20 grams of drag a disc has more than a 100 gram drag advantage over any other wheel, so it would take a lot of RR to offset the gains.

As for covers, the BikeTechReview data has been discussed by a lot of people I know in the industry and there are a few things to be aware of, first the disc used was borrowed from somebody, it is a 1992-1992 Zipp 19mm wide disc with 20mm braking zone that was ground parallel, this is an old technology that was replaced years ago as the lip between the body and brake surface causes considerable drag...construction similar to this is still used by quite a few manufacturers, but is really not ideal. Also, the tire on the wheel was quite used and not the same tire used in the other testing, and was from my understanding rather used as this wheel belonged to somebody. As a result, the data for the real disc is far worse than anything anybody else from Tour magazine to us to John Cobb has ever recreated for even a similar disc much less a modern one, so in that way I think the comparison between the two wheels is a bit misleading in that particular test. Also, the disc cover wheel used was a very meticulously constructed and maintained wheel with very nicely sealed edges and no apparent blend problems between rim and skin. This test does show that a cover can make for a very efficient wheel, but having said that, there are two issues people always overlook with covers. First, a cover is not lenticular, it is conical, not that is affects the data too much, but the conical wheel tends to have both more surface area and more frontal area than a lens or flat disc, so at lower yaw angles the performance suffers. At higher angles the wheel performance is entirely dependant on the care taken in assembly, as I said with the original Zipp disc construction and the construction of most clincher and even some modern tuby discs, a 0.030" (0.75mm) step at the skin/rim interface will cost you 6 watts or possibly more. So while a cover can be made quite fast my experience is that almost all of the ones I see in IM pits and such are not constructed or maintainted to their potential. As someone who used to use and manufacture covers before I worked for Zipp I can tell you that I used to spend hours before every event tweaking and maintaining the thing to get it just right, the best is to permanently silicone bead the one half to the rim using C clamps and wood blocks to get the surfaces exactly flush...the other side really should have a valve hole cut in it and do the same for it's asembly as taking the thing on/off can really throw the alignment out and create discontinuous surfaces, I had a coach that drilled all of this into us as juniors without any data, but I can now say after having spent hundreds of hours in the wind tunnel that he was spot on.
so, in your opinion, is my rear 808 faster with or without a cover in rolling terrain and moderate wind conditions??
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [Cousin Elwood] [ In reply to ]
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"- - Big error there. The primary advantage of a disc is the reduced egg-beater turbulance from spokes passing the seat and chain stays. No way a spoked wheel can get close. "

I generally agree with this statement, but if you look at the drag numbers provided by Hed you will see that their Stinger 90 is very close to a disc until about 12 degrees when the 90 starts to go up and the disc continues to go down. Like I said, I generally agree with the the idea that a disc is the fastest rear wheel, and I always seemed fastest when running a Zipp disc in the rear with an 808 up front. Than t being said, I am just not convinced any more of a significant difference between a 90 rear and a disc rear. I can see 5-10 seconds per 40k, but not much more. I guess it all depends on the wind- right?

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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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Hey tjs
Well I have been on a Spinergy Rev-X (very fast) a Renn 575, and I sold that wheel this season to get an American Classic 420 with a Powertap SL hub with a wheel cover. and I can’t tell difference between the Renn and my 420 with the wheel cover. It’s it a custom cut one from wheelbuilder.com.
But having the wheel cover and the power meter is the best, Hands down!
If you want to go faster I feel very strongly that is the way to go.
Dan…

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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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Well well well I think we all can agree. Aero wheels are faster than no aero wheels. All the disks are pretty fast, disc covers are fast, but maybe not so cool. Pretty much a 50mm or trispoke front is pretty fast, a deeper one may be faster under some circumstances but maybe harder to handle. A deeper rear is about as good as a disc in a lot of situations.
WE CAN SPLIT HAIRS TILL THE COWS COME HOME, AND IT DON'T MEAN SQUAT.

Buy your wheels from John, Steve, Cees or Josh and you will go faster than you are going on no aero wheels. Buying a bunch of them probably will not make you go any faster. Do we have to argue this for the next ten years on a daily basis.? Enough already.

I think it is sort of rude to be"Calling someone out on that one" especially since we know Josh, John, Cees, and Steve have spent hundreds of hours in the tunnel and we have spent little if any. Yes we all have our bias as do they, but all the aero wheels are gooing to make you faster than none and if you reach around and scratch your butt a couple times one wheel may end being slower than another. And I think if you read carefully what the experts say it is very hard to get a picture of a wheel in all the possible real world conditions in the tunnel.

One of my favorite antidotes is how fast was my HED deepdish wheels when I got off a TT in the rain and there was probably a quart of water in each rim? Does the yaw angle factor in there. At the time they were supposed to be the fastest wheels in the world.
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [G-man] [ In reply to ]
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I don't see where we disagree, and I am not sure what the purpose of your post was in reply to me. I didn't call anyone out so I am a bit lost. That being said, I think a cool thing would be for one of the wheel makers to come out with some sort of test data that doesn't claim their stuff is *always* the fastest. When was the last time you saw this? Everyone claims their stuff is the fastest and that is a bit, well, misleading, or at best incomplete to say the least. It's about time folks are held accountable for their claims. If your going to say is x is faster than y then you should eb able to prove it- or not say anything. I don't see this as unreasonable.

My only point is this; I don't think there is any real difference between any of the wheels out there. That being said, I do think my 999 set was the fastest I have ever owned. It may or may not be faster than anything else, but I always had my best results on them.

BTW- how did you get a quart of water in your wheels? That sounds a bit odd. Are we talking the Jets or something?
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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Quote:
That being said, I think a cool thing would be for one of the wheel makers to come out with some sort of test data that doesn't claim their stuff is *always* the fastest. When was the last time you saw this? Everyone claims their stuff is the fastest and that is a bit, well, misleading, or at best incomplete to say the least. It's about time folks are held accountable for their claims. If your going to say is x is faster than y then you should eb able to prove it- or not say anything. I don't see this as unreasonable.
Let me guess... You didn't major in business or marketing?
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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"if you look at the drag numbers provided by Hed you will see that their Stinger 90 is very close to a disc until about 12 degrees when the 90 starts to go up and the disc continues to go down."
- - I'm not an engineer, nor do I play one on TV, but I believe the numbers HED is giving are for aero drag only, not rotational drag (caused by egg-beater). Having upgraded a few years ago from a HED Deep (90mm ~Stinger) to a disc, the disc yielded >90 seconds faster over 40K, based on real world trials at seven races in one season. Also, top speed on all races showed a higher number (downhilling +40mph). That's anecdotal, but there was a clear and significant improvement at every race.

"Than t being said, I am just not convinced any more of a significant difference between a 90 rear and a disc rear. I can see 5-10 seconds per 40k, but not much more. I guess it all depends on the wind- right?"
- - I do find the disc a bigger advantage on a windy day, because I don't have the wind-related handling issues of the guys riding 404s, 808s or some such equal f-r setup. Having the disc on the back really minimizes the wind push on the front wheel (I run a Cx, which is similar to a 404, maybe a tad deeper). For 5-10 seconds, I wouldn't have bothered to buy the disc, although I do think it has cool factor. If it was only 5-10 seconds faster, I'd be hard pressed to identify any difference. 5-10 seconds could easily just be me having a bad day or a few extra morons who ride to the left and bollix my pacing when I need to pass them without getting killed.


Cousin Elwood - Team Over-the-hill Racing
Brought to you by the good folks at Metamucil and Geritol...
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tjs] [ In reply to ]
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well i have 404's (tubs) and i inquired at my bike shop about getting a rear disk cover on my 404 as i run a powertap sl. well the owner of the shop suggested i just stick with my 404's without the cover as we said my wheels where already aero and the covers don't sit flush and may cause more drag. But he did say if i just had regular wheels that yeah i should buy the rear disk cover.

my 2 cents.

although now i wish i would have bought the 808's




Like T says, "Remember it is all about the Bike because it is all about the Run!"
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [tury] [ In reply to ]
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RENN KAISER BABY!
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [TGL] [ In reply to ]
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In Reply To:
Quote:
I just don't personally think they are as cool.

Finally we have an honest and to the point ending to this madness...

As with most AG's bikes... it's all about the coolness factor and not how fast I can go..

I ride a zipp disc and it's cool;-)

For coolness then it has to be Campagnolo Bora wheels. Zipps are too common.

So what do you want? To be cool and ride Boras and be a little slower? Or ride Zipps which are not as cool but are faster?

Coolness rating:

Campagnolo Bora
Easton
Zipp
HED
All others

________________________________________________

Pasadena Tri Club
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Re: Please; people with REAL data (wind tunnel or otherwise)...Is a disk still the fastest? [TGL] [ In reply to ]
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Nope- when I went to college I wanted an education :). As for now I prefer to make an honest living. I do work in business though so go figure...
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