Aero wheels give about a minute and a half compared to a 32 spoke over 40 kms. Look at table 3a:

http://home.hia.no/~stephens/aero.htm

I already have a Zipp 404 on the back. Think there is any real advantage with the disc?

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''Sweeney - you can both crush your AG *and* cruise in dead last!! 😂 '' Murphy's Law

Um...in a short race.....



...nope....



You may notice the same time savings by shaving your head to loose the weight of your hair, possibly getting lighter brake cables (half worn pads for weight savings too).

There seems to be so much voo doo attached to the disks. All of them. If I was you and I had the 404's...I would look at the disk wheel as a psycho sematic performance improvement device. If it makes you feel faster (and look cooler - god knows that is why I got the 909's) - then great, you have a great disk that will offer great improvements.

Oh...and it is cool in a race to have people tell you as they pass you that they heard you coming by the "whomp whomp whomp" of the disk wheel.

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What if the Hokey Pokey is what it is all about?

Man, I have to tell you, I am a HUGE believer in disc wheels. I think they are faster aerodynamically, stiffer for better power transfer and may be the best choice in nearly all environments. Almost everyone in the time trail stages of the Tour de France is using a rear disc, even in team time trials. I can't immediatly produce supporting evidence, by my personal race results suggest a disc is the fastest rear wheel for me in almost all circumstances.

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Tom Demerly
The Tri Shop.com

.....absolutely! Every study ever done shows the disc as being faster. Another post basically says it is no faster than shaving your head....which would you rather do? ....or why not do both?

Why are you only using it in two races? The only race I'm aware of where it is not allowed is IMH (I Think), and I'd use it there if allowed. Unless you are doing an up hill time trial it will be faster.

Congrats on the new disc!!!

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

david's enthusiasm notwithstanding our original poster's question remains a good one. the man already owns a 404 rear. if a disc's savings over a standrd box section rim is 1.5 to 2 min ( a figure i have seen often enough) then what is the savings from a 404 to a disc? certainly we can assume it is no greater than half the previous savings, and likely less than that. so, call it 30 seconds to 50 seconds over 40k or so. a race number flapping in the wind would be considerably more. 400 - 800 bucks for 40 seconds? i would say what i would do with that pile of benjamins first. . . .something that would gain me those 40 sec inside the first mi of the run. . . . but that would be another thread. :)

In the book "High Performance Cycling" by Asker Jeukendrup PHD, John Cobb and Jim Martin have co-authored a chapter on aerodynamics. They have a neat little chart with riders on different wheels at power levels of 100, 200, 300 and 400 watts. The time advantage the 100 watt rider is much greater than the 400 watt rider. For 40 kms a 200 watt rider on standard rims has a time of 67:43, on aero rims 66:46, on composite rims(tri-spokes) 66:44 and on tri-spoke front with disc 66:32.

You can see that the biggest gain is with aero rims like your 404's over the standard box rims. According to Cobb/Martin the tri-spoke gain over good aero rims is minimal and running with a disc should make you about 14 seconds faster than with the disc. If you can produce 300 or 400 watts the time difference is 13 and 11 seconds over 40 kms.

I was quite surprised reading this as I always assumed that a rear disc would make more difference. Either Cobb/Martin have underestimated in their calculations or there is a hell of a lot of marketing hype associated with discs. They are faster according to this data, but not by much.

So guys, don't shoot me. I'm only the messanger. This is what Cobb and Martin say in the book.

t-t-n,

Maybe you didn't read his post!? He is getting the disc as a present; so, when he has it why not use it since it is almost always faster.

You seem to be answering "should I get a disc if I already have a 404?" That wasn't the question. I'm not in to snappy responses, but your attemp to dig at my response to what the question really is doesn't make much sense.

Your new year going OK?

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

sorry david, i did not intend to offend. i was speaking to his direct question of "how much gain will i see with the disc" , with respect to his 404. it seemed most of the responces were in reference to a standard wheel, and not a 404 rear. if yours was not i missed that - this is possible, as you are correct in noting i did forget about the gift part. still, i find the basic question of 404 vs disc to be an interesting one.

. . .and i think cerveloguy's quote of 14 sec makes it all the more interesting. . . .

Point taken.

See Tom Demerly's post above. I do agree that if you aready have a 404 the the issue is tighter. I have a Coprima 4 spoke that I got before discs were allowed at IMC and have used at IMH. Every other race (tri) I have ever done has been with the disc. Whether it's 1 sec, 14 sec, or a min, it is faster. I also find it stiffer for acceleration, and precise in cornering. I do note that I am bigger built and control has never been a factor for me; although, as I believe Dr. Coggan has pointed out, the rear wheel has very little effect on control.

Peace.

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

I would only plan to use it in two races because all the other races I plan to do, Columbia, Timberman, Duke, even our local sprint race with a nine mile bike, have significant hill work. I might use it also for Montauk sprint, but I really don't see any bennifit in dragging that thing uphill.

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''Sweeney - you can both crush your AG *and* cruise in dead last!! 😂 '' Murphy's Law

I don't know the science, but I haven't found that to be the case. There was a long thread on the old forum mostly by the tech guys (Coggan, et al) with the basic conclusion that a disc is faster at almost all applications. The races you mention have some hills, but certainly aren't mountainous. I'd just say that I (and I'd contend science confirms) would use it.

I'm sitting trying to think of the hilliest course that I have used the disc on - IMC, etc. There was an old race around here (in the 80's) in Danville Va, that the old Triathlete Mag rated the toughest course East of the Mississippi, and I used a disc with no problem.

Wait 'til you get it and ride it. I think that you will love it. Heck, even if it is just emotional (I am a sensitive guy;-)) I like riding it.

Great present to get!

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

 "What kind of gain do you think I'll get with the disc?" (As opposed to a rear 404)

According to the data presented above, it looks like about 8-10 seconds for your duathlon and about 28-32 seconds for your half iron.

I realize it's a gift, but I agree with ttn... a lot of money for that kind of time savings.

I think this is what the "geek" is in the word "tri-geek". Tri-geeks should really be called techno-geeks for our willingness to depart with our hard earned cash for the latest gollygeewhiz new fangled cooley high tech toy that comes along, whether it's proven or not.

I have been as guilty of this as anybody but I have made a New Year's resolution for 2003 "I will not spend any more money on tri-geek gear this year unless it can be proven with genuine scientific study that it will make me faster."

And for me what I consider being "faster" is slow for many of you. My second New Year's resolution is that I will train harder in 2003 and will actually make an effort this year to improve my running.

However, if someone bought me a Renn disc for a present I certainly wouldn't say no to it.

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Want: 58cm Cervelo Soloist. PM me if you have one to sell

Vintage Cervelo: A Resource

It seems we all have an opinion on disks.........THE TRUTH IS OUT THERE......i just don't think we've found it yet.

All i can say for myself is that when i use my disk over my HED Alps, i seem to be able to run like the wind and feel very light on my feet.

I have no idea weather it's a faster wheel (the disk) because everytime i race there are different conditions......wind/rain /no wind/ sunny/ hilly/flat and so on and so on.....i just have not yet found the same conditions on the same course to measure my times. throw in the fact that i race at different levels during my season.....ie. heavy training/no training/race fitness/race weight etc etc and to try and find out that the disk is faster.......#$@k knows.

ALL I CAN SAY is that when i use the disk, i run very fast. This may be because i require ALOT LESS EFFORT to pull the darn thing that i have bucket loads of energy left up my sleeves.

Paulie