This is an interesting perspective, and one that no doubt does have some merit.

I'll put a slant on this. Firstly, this opinion isn't scientific, it is more obervational, anecdotal and a wild-assed guess.

I've long thought that perhaps a disk will work well and produce tangible time savings for some riders, while much less so for others. This isn't a cop-out answer, but I think it depends on riding style. Also, I think the speed has a lot to do with it. At 21 mph average speed I doubt a disk (or any aero wheel) performs the same as at 24 mph average.

My sense is that average to smallish riders who tend to ride a shortish reach and a lowish cadence and trend toward a more powerful style are the ones who do best with a disk in most conditions. Riders who are lighter and have a lighter style may be too disrupted by the crosswind turbulence and maybe just palin freaked out by it to benefit much.

Interestingly, the wheel we have returned most frequently- and quite frequently come to think of it- by customers is not a disk or a wire spoke wheel. Nothing wrong with that wheel design or manufacture: Customers just try it, don't like the way it feels on the road and go with either a disk or a deep-section wire spoke wheel.

---

Tom Demerly
The Tri Shop.com

To firstly reply to TomD, if there is there is one thing I know, NOTHING about Jens's observation are "wild-assed guesses." This is a man who carefully calculates the Crr of each tire he runs, who spends money in the tunnel, and who probably eats, sleeps, and craps more aerodynamic issues daily than most of us will in a lifetime.

On a side note, I'm also really tired of the "21mph is TOTALLY different than 24 mph" bs. The flow regimes in both cases are basically indentical. We are not talking about bike vs. fighter plane here.

Anyway, with regards to Jens's original post, the disc is clearly an asset on the track, where even 1/10 of a second matters. It is also the obvious choice of rear wheel for seat-tube-less bikes like the softride, where it basically makes-or-breaks the aerodynamics. But when you look at a bike like say, the P3C, where everything is so shielded, will a disc really make that much difference over a H3 or 808? The answer here, to be Clinton-esque, depends on what your definition of the word "much" is. If you are racing the TdF, then one second matters. If you are racing IM, then maybe it doesn't so much.

There are certainly a number of very fast IM riders who have shunned the disc. I believe it was Thomas Hellriegel who never rode a disc (but don't quote me for certain on it being him) because he didn't like the way they cornered. Certainly, the extreme rigidity of a disc can be a liability on a technical course, especially compared with a spoked wheel. Add in the affect on comfort (vibration has a very really effect on power output), and you may be shrinking the advantage even more.

At the end of the day, you also have to square price with all other factors. Renn makes a really nice disc for less than the cost of almost any other wheel. There are also still lots of people riding frames that are not super-aero. And of course, the softride and titanflex are still quite popular.

There is also the issue of reliability with the track-testing method of German Triathlon mag, whcih many, including Josh, have taken issue with.

Zipp has published that the 808 is equivalent to a disc at up to 12* of yaw, so the question is then, how often are you at 12* of yaw, and that probably will answer your question...

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

What is your opinion on less aero bikes like the p2-sl where less of the rear wheel is shielded?

I have never ridden a disk. Do you notice a comfort difference between one and a spoked wheel like an 808 or 404?

Thanks a lot,
Dan
www.aiatriathlon.com

---

http://www.aiatriathlon.com

I don't think you can really make a judgement call on say a P3 vs. a P2. That is something only a wind-tunnel could tell you. Back-of-the-envelope, I'd think a disc would be better in the P2-SL vs. a P3C, but by how much I wouldn't have any idea. Probably very minimally.

The idea of "comfort" is so totally unique to each person, that it's tough to quantify. Will you notice riding a disc vs. riding a 404 or 808 or other spoked wheel? I would think so. But whether or not is a truly perceivable comfort difference, that's a personal question.

I think the real subject of the thread is to basically say, if you have a 404 pair or 808 pair, a disc is probably not going to be the huge difference maker you might imagine. Things that I find amazing, for example, are the number of peole with 999 pairs and regular helmets. One thing I'd be fairly certain of is that 808+aerohelmet is faster than 999+regular helmet...

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

i would personaly prefer by far riding a spoke wheel to a disc as i find it more comfy. but like rappstar says...it s very personal. i try 3 different disc in my life (because everyone told me they where fast..) and never like any of them....it just dosnt match my way of riding and all my best bike performance in triathlon have happen on a deep wheel but never with a disc. i just dont like them but it s very personal.

thomas is one of the very fast biker that dosnt really like disc and prefer to ride all the time on his Mavic cosmic carbon and there is also Norman stadler that was prefering to ride bora wheel but not a disc. everyone as is preference.

---

Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

Surely the real reason anyone rides a disc is so they can overtake other riders and demoralise them during the pass by changing up a gear with a satisfactory "wurrrrr.....Kathunk....wurrrrr".

---

---------------------------
http://www.nunnsontherun.com

So it was Hellriegel. I thought he was the one you said didn't like the disc when we discussed this back in February.

I think one of the nicest things lately is that with wheels like the Bontrager Aeolus (65mm and perhaps 90mm), Blackwell 100, HED Stinger/Jet 90, and Zipp 808, you no longer NEED to choose a disc to get a really deep wheel, giving people a lot more options than they once had...

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

" Surely the real reason anyone rides a disc is so they can overtake other riders and demoralise them during the pass by changing up a gear with a satisfactory "wurrrrr.....Kathunk....wurrrrr". "

That said, I think there is some merit to the fact that if you feel fast on the bike, that's much better for the psyche than if you don't feel fast. It may not make much difference aerodynamically, but the psychological benefits could be big.

My sense is that average to smallish riders who tend to ride a shortish reach and a lowish cadence and trend toward a more powerful style are the ones who do best with a disk in most conditions. Riders who are lighter and have a lighter style may be too disrupted by the crosswind turbulence and maybe just palin freaked out by it to benefit much.

I don't see why a rider's riding style would have anything to do with it. Maybe the rider's actual weight.

I think, though, that the biggest factor affecting the benefit of a disc is the bike's frame design. If you have a frame like the PC that does an effective job of shielding the rear wheel, the importance of an aero rear wheel is already diminished, and the incremental difference between a disc and a deep section wheel becomes even more incremental.

If you're riding a traditional round tubed frame, or a beam bike, I would think that the benefit of a disc is greater.

---

"People think it must be fun to be a super genius, but they don't realize how hard it is to put up with all the idiots in the world."

No, no.. I meant my comments were wild-assed guesses. No the other fella.

---

Tom Demerly
The Tri Shop.com

   

I'm just kinda throwing this out there -- I really don't know. That's why the subject is a ? rather than an outright statement.

My trig is a little rusty, but if I have it right, at 30mph, it takes a 90 deg sidewind >6.5mph to exceed a 12 deg yaw. I suppose that probably happens a fair amount.

It's interesting that hour records have been made on both disks and tri/quad spokes:

---

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

I always liked hearing that sound. "wurrrrr.....Kathunk....wurrrrr". :)

For me I like passing people who have disks, it sort of lets the air out of them. I know they are proably thinking "what the $#@! that guy has regular wheels and just passed me".

It is interesting. Your computational ability- for whatever that is worth in terms of relevancy in this discussion- certainly trumps mine, no question.

I wonder if there is a segment of this assessment that transcends a computation, i.e., some subjective set of variables from that are different from one rider to another that may influence these results.

I don't know one way or another at all- again, I am simply guessing here. I wonder...

---

Tom Demerly
The Tri Shop.com

[reply]Obviously, wind and other environmental factors play a role -- it's just troubling that after a number of times, I have yet to observe a significant advantage.
<snip>
-jens[/reply]

thanks for the email yesterday jens, getting to finalizing today the rest of the data...

but that aside...

having recently gotten the kestrel4k and taking to the local tt, i find it's data to vary from wunerground. So you might want to invest in one for direct comparisons (even within the same 2hr time window).

I would be curious if you find the same results from the same type of "test", no, data gathering, with more accurate weather data....

all that said, the fact that both obree and boardman used tri/quad spoked wheels may or may not be applicable. Having just read the obree book (interesting read, albiet not a great book for book's sake) his equipment selection is strickly a sponsorship based decision.



just my nickel.

g

---

greg
www.wattagetraining.com

808's with a PT-SL rear hub are the new bomb Jens :) Of course you should run OFUT tubulars no more than 19mm wide and >200 psi on there to give everyone else a chance.

But you'll never really know what's best for YOU until you book some LSWT time and compare your disk and rear 808 over real-world yaw angles ;)

rmur

even them you wont know.....it s just a wind tunnel.....it s not a perfect answer to live by....

wind tunnel is very good but it isnt the same as outside. so...better go with what YOU beleive in so you have no douth in the middel of the race!!!!!

---

Jonathan Caron / Professional Coach / ironman champions / age group world champions
Jonnyo Coaching
Instargram

[reply]I always liked hearing that sound. "wurrrrr.....Kathunk....wurrrrr". :)
For me I like passing people who have disks, it sort of lets the air out of them. I know they are proably thinking "what the $#@! that guy has regular wheels and just passed me".[/reply]

This probably happens to me once or twice in a HIM, I just smile realizing I am spending a lot less power to ride that speed. :) The best one was when I first got the Renn and he had that lack-of-grease problem in the freewheel. I was flying past people squeaking like my bike chain hadn't seen oil in 10 years. I added an H3 to the front so now I have a cacaphony of whuuurrrr and whoooop-whoop-whooop going. It sounds awesome in a crosswind.

Anyway, Jens keep in mind that a track test of aero wheels is less than useless in the real world of tri. The majority of "aero" wheels are very, very similar in drag at 0 degrees on an indoor track, but there are vast chasms of differences at 10-30 degrees where the rest of the world rides. That German Triathlete mag test is functionally useless.

---

---

Course y'all know I'd have to go out and test it. Actually, I was testing another failed experiment and it was too windy, so I figured I'd slap a disk on and see what happened. So here's the raw data for my field test. Note that all the wheels had the same tires and tubes.



Spoked front and rear

mph (north)....watts.......mph (south).......watts.........avg mph...avg watts.

.......17.1.......79..............16.5...............92................16.8.......85.5.......

.......19.1.......106.............18.8............129................18.95.......117.5.......

......20.4.......127..............19.9............145.................20.15.......136.......

.....23.2.......176...............23.7............219................23.45.......197.5.......

.....25.2.......225...............25..............262...................25.1.......243.5.......

Spoked front with disk.

mph (north)...watts.....mph (south)......watts.......avg mph.......avg watts..

.....25.8.......210.................25.1.......271..................25.45.......240.5......

.....28.1.......276.................27.1.......322..................27.6.........299..........




I hosed the FA calcs there, so ignore them. Bottom line, the disk does appear to do better. I get a CdA of .236 for a crappy spoked front and a disk vs .246 for two crappy spoked wheels. HOWEVER, it's curious that the disk actually does a tiny bit worse than the spoked wheel when riding into the wind (though, from the numbers it looks like the wind might have increased).

- jens

---

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Yes discs are overrated - yet so are all aero wheels in my opinion....

My stock wheels (Velomax Circuits) seem to be as good as anything (909's, Alps, Renn).

The only time I noticed a big difference in wheels was when I taped certain tubulars on - then I went a lot slower.....

How much time do you think the best aero wheels save per 40k over wheels like the circuits? I'd guess 30-60 seconds tops (maybe less). Difference between aero wheels = approaches 0....

Dave

I love that picture of Boardman. Perfect positioning personified - and the results to back it up!

Fleck

---

---

Steve Fleck @stevefleck | Blog

Read Dan's article in Inside Triathlon "wheel review" it ans. some of the questions. It came in the mail yesterday.

He also talks about clinchers vs Tubies.

---

Train safe & smart
Bob

To answer the original question, I do think that discs are overrated for indoor track racing, which is where the Triathlon De and Rennrad tests were done. Our website is all screwed up at the moment as we are updating it, so I've attached a screen shot of a graph showing this below, but almost all wheels with semi-aero rims and bladed spokes are nearly identical at zero degrees of yaw, which is what you see indoor on the track.



(note how compressed the Y axis is compared to the Tour graph below in order to accomodate the 32 spoke box section wheel!!!!)

In fact the disc is generally slightly less aero at zero than a low spoke count deep section wheel at zero. This is what you see in the Triathlon De testing, as the winning wheels were deep section low spoke count with the winner being a Vuelta wheel using a variant of our 404 rim with only 12 spokes. The 808 and Xentis wheels also outperformed the dual disc combination, but when you look at the data for zero degrees of yaw, this is predicted by the wind tunnel data. The Xentis wheels are interesting because they took the fact that composite spoked wheels have lower drag at higher yaw angles and pre-angled the spokes of the wheel, so that two of the are angled to the left about 10 degrees and two to the right about 10 degrees, this makes it one of the most aero wheels at zero, but much less so at higher yaw angles.

The key to the disc wheel working is to have a little wind. At yaw angles higher than about3-4 degrees, the disc becomes the fastest thing going, and nothing can touch it until yaw reaches 40+ degrees. The Tour magazine testing which was a combination of wind tunnel and computer simulation (also on our website but currently not working so I've attached a screen shot) shows this really well as the disc they used as a baseline was slightly less aero than an 808 or xentis at zero, then the 808 and disc were nearly identical to 12.5 degrees, and the 808 began increasing again in drag and the disc kept decreasing out to 30 degrees.



This means that the 808 would be somewhere between identical to slightly faster than the disc at low wind speeds and slightly less fast at higher wind speeds. Their mathematical model assumed 8-10mph winds on a roughly circular course, and they predicted that the discs would save 72 seconds per 40k over a set of ksyriums and the 808s would save 68 seconds, so an advantage of only 4 seconds. Now if the wind speed were set to 12mph, the results would skew more toward the disc, or if they were set at 6mph it would skew toward the 808, so really you need to look at the course and wind speed relative to rider speed to determine when and where a disc will be most advantageous.

Also, in the end it really depends on how much time you need, for some people the 4 seconds saved using rear disc over a rear 808 are pretty trivial, for others they are very, very large (one age group at masters nationals last year had the top 3 guys in the TT separated by less than 4 seconds, so for those guys 4 seconds are huge). Sadly, the place where a disc would really be awesome more than any other would be kona, where the wind speeds and angle are pretty constant and most years we see the effective yaw angle for top riders at 15-20 degrees, a zone where a disc could literally save 4-6 minutes over an 808 and 5-7 minutes over a hed3 and at higher yaw angles could save as much as an additional 10 minutes at Kona!!!

So in terms of competitive advantage, the person who rides the disc on the windy day when the competition is most likely to forego it, is the one with the biggest competitive advantage.

---

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

What was the setup that produced these results? Did it include a bike + rider attached to the wheels, or were they stand alone in a wind tunnel?

   

When I scrutinize the two graphs you posted (the one from Zipp and the one from Tour), I see some interesting differences in the relationship of the two disks to the 808s. It looks to me like the Comete (lens shaped) does much better than the dimpled Zipp disk above 15 deg yaw. I wonder if this isn't some confirmation of the Greenwell data.......



-jens

---

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers