Before I go out and spend a grand on some Zipp 404s, I was wondering if anyone has thoughts on how much performance gain one can actually attribute to their race wheels. The performance gain from adding aero bars was dramatic, but I suspect it will be much less so if I swap wheels.
About a minute and a half over 40 kms give or take some. Here’s Jim Martin’s results from his wind tunnel testing.
They are a definite improvement, although I don’t know about the minute and a half unless the conditions are ideal and your course isn’t too hilly. I also theink that there is the “need” vs. “want” issue. Do you “need” race wheels? No, your training set will get you around the course. If you’re like most of us though, you “want” race wheels because they are faster and the look really cool 
Isn’t the want vs need thing so true. I “want” a Cheetah just like Natasha rides. But then do I really need it since I’d still be just a middle aged, middle of the pack age grouper no matter I ride.
You can probably gain some time and save some cash by just getting a disk. A Renn will be a lot less the $1k and will give you most of the time gains.
Do you need a disk or race wheels, the answer is no.
A
I was out on a ride the other day with a guy that qualified for Kona at IM Florida on his P3 and stock Ritchey rims.
They are good, high performance and very aero - but they are fragile, there have been problems with them for years. You would want to use them for racing and only racing.
If your wheels are pretty marginal, you may be well served by getting what roadies refer to as “race wheels”, these are lightweight, have excellent hubs, are usually very durable, and are somewhat less expensive than Zipps. The Richeys fall in to this category, as do the Campy Eurus and Neutrons, and the Mavic Ksyriums. You can find these for between $500 and $700.
In general customers are usually surprised at the difference good wheels makes, and Zipp and Hed are the very best. I have never, ever had a customer “underwhelmed” by their race wheel expereince. Now, in fairness, once they pay the money it would be rare to get buyer’s remorse. But, I use them (and pay for them…) and I know they make a huge difference on race day. HUGE! How much? That’s a question for John Cobb or Steve Hed or Bill Vance (at Zipp).
I think a lot depends on your fitness, your psyche, and course conditions, but the bottom line is you NEED a bike that fits you and equipment in working order; you don’t “need” race wheels.
I reached my first podium last fall in the very first race I didn’t use race wheels for. I’d just sold my 650c tri bike and my race wheels are 650c, and my 700c Trek 5500 training/road race bike had cracked. So with just enough time to spare for some final training and adjustments to my position I bought a Giant TCR frame/fork and some admittedly fairly crappy Alex Rims wheels and somehow managed to have the race of my life. Third fastest bike split and third overall.
Of course, had I had a pair of 700c race wheels to use on that day I sure would have. It’s just that once I got on the bike and started cranking I never once thought about my wheels and how slow they were dragging me down - just my legs and how fast I was going!
-David in Taipei
Where can you get a H3 for $400???
I may be coming on some money really soon, and at that price i could afford that combo!!!
Thanks,
-Kevin
I have not yet bought a pair of race wheels but I have been researching them diligently. The best I can come up with by comparing numbers from the experts and with anecdotal confirmation (I think it was from ajfranke) going from standard box rim wheels to the best class aero wheels (something like H3 + disc or similar) would add 1/2 mph to your speed if you are around 21 mph.
Check your rankings, add 1/2 mph to your speed and then see what your ranking would have been - then decide if it is worth the $.
FWIW, I just don’t see how anyone can justify not getting a Renn disc for the back. I don’t understand how the cost/benefit analysis can lead you to any other rear wheel.
some guy up there says “just get a disc and save some cash”. that’s the worst possible idea!!!
here is the way to go if you don’t want to spend much but get some aerobenefit anyhow (my opinion, it’s a free country right?)
- get a front wheel with fewer spoke number than the original 28something spokes…(rolf, or something similar ~200$)
2)get a good race wheel in the front (Zipp404, Hed, Mavic Cosmic…) - get the above and a HED3 on the back, or a HED Deep or something similar, for lightweigts maybe a HED404 or similar
4)Once you have all that but no sooner!!! get a Disc, Renn is a good choice!
number one gives you most of the aero-advantage.
But yes, there is a big mental advantage to have a HED3 on the front and a Renn disc on the back, and make sounds like an aeroplane when you go 15m/h 
Why would you do that? Why buy a Hed 3 before buying a disk? That makes no sense to me especially if the person has another set of wheels and could save money by buying the disk.
I can see the argument over the importance of front wheel vs. rear wheel aeroness, but there is certainly something to be gained by having a very aero rear wheel and if it is a Renn it is probably the least expensive aero wheel (front or back) that you can buy.
I would do one of two things…
If money absolutely was the object then I’d get a Renn disk.
If money was just sort of important, but I wanted the biggest gain I could get with just one wheel, I’d get Hed 3 front (or a 404 if you are concerned about wind & weight).
If money wasn’t an object I’d get a Hed3/404 on front and a disk (pick your favorite) on the back.
I don’t know the drag numbers (savings) for a rear disk or a tri-spoke front, but I’d have to wager the $ per pound of drag saved would have to be very close for the two. Close enough that whatever toots your horn is really the deciding factor.
First, you forget one important thing, you can’t use the disk in all conditions!
If there is too much sidewind you won’t use a disk, believe me. In some races like Hawaii you’re not even allowed to use it. So if you only buy one wheel, then you need something you can use in any race you enter!
Second, you want to improve aerodynamics right? So if you want to save money, get the least expensive that improves your aeroness the most. So if you have the money to buy a Renn, get a aerodynamic frontwheel for the same price and you will improve your aerodynamcs more than with any Disk!!!
Front wheel first! No matter how aero your rear is, if the front sucks you’ll suck overall.
But hey, a Renn disk and a normal front looks way cooler than a HED3 in the front and a normal rear wheel! But that was not the question!
No. Your argument is flawed…
First, a discussion about buying one wheel or none at all is not a discussion about someone going to Kona. Forget that notion. That is a whole nother story. We’re talking MOP. If we were talking top AG or elite, we wouldn’t be having this discussion because they’d already have race wheels AND know whether they needed them or not.
Second, point to a very aero front wheel that costs $325. It surely must be less aero than a 404 or Hed 3. Is the aeroness still more of gain than a disk on the back? How do you know?
Third, handling, wind, and disks, is overstated at best. Wind affects the front wheel so much more than the back. And honestly, if it is too windy for a disk, it is probably too windy for a tri-spoke. But my point was use the disk when possible, use the training wheels when you can’t. That is a reasonable option. Why pay more for something that helps you less the majority of the time? Very, very few people would be unable to ride a disk in races more than 50% of the time due to conditions.
I hear your argument, but I don’t buy it.
If you can point to something that says a moderately aero wheel costing less than $325 saves you more drag pounds than a disk, then I’d buy it.
Ok you want some numbers huh?
here we go:
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The total drag of the wheels is in the range of 10% to 15% of the total drag on a bike. Drag improvements between wheels can reduce this by 25%, or 2% to 3% of the total drag.
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The drag on the rear wheel is reduced by 25% due to the seat tube.
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You therefore need a 25% drag reduction on the rear wheel in order to be at equal with your drag gain from the front wheel!
Wheel Cxo
Conventional 36-spoke 0.0491
HED CX 24-spoke 0.0379
HED3 0.0379
ZIPP 950 disk (flat sided) 0.0364
- Conventional vs. 24 spoke wheel => 22.8%
- Conventional vs. disk => 25.8%
this means that the disk is about 3% better than the 24spoke wheel
BUT
you need to be at least 25% better in order to have the same effect as the front wheel!
SO
The 24 spoke wheel is 22% better than the rear disk
Again, my point!
A little gain in the front has more effect than a huge gain in the rear wheel!
There is lots of front wheels you can get for under 325$ that will give you enough advantage over a conventional wheel!
If you still don’t buy the argument, well it’s still a free world.
I agree your numbers support your claim, although I don’t agree with your math for the rear wheel. If I understand your 25% statement, the correct method for calculating the rear wheel drag would be to reduce the drag of the 36 spoke wheel by 25%, reduce the drag of the disk by 25% and then subtract. Divide by the new 25% reduced 36 spoke drag. That would still be a 25.8% improvement, but the absolute drag improvement (which is what matters), would be .009525 for 36-hole to disk vs. .0112 for 36-hole to 24-hole on the front. Or the front wheel is 17.6% more effective, so your point is made…
Unless you use someone elses numbers…
From the Hed website, averaged for 0-30 degree wind angles.
32-hole = .649
Alps = .383
H3 = .343
Disk = .295
In this case going from 32-Alps gives .266 lb improvement
Going from 32-disk gives .354 lb improvement.
If I apply the 25% reduction to the rear as you did the disk gives…
Are you ready?
.266 lb improvement!
So, using these numbers the benefits of 32-Alps & 32-disk are identical, however, a Renn disk still costs less, so we have a definite clash of conclusions.
Bottomline: As I said in the first post. Buy the wheel that toots your horn. That will be the best wheel…
Lucky for me I have a 404 front / Renn disk rear so I don’t have to sweat the details.
Justin on LI, I defy you to find anyone knowlegeable in aero who will tell you that, given one aero wheel, front or rear, who would then say, “put a disk on the rear” before they would say “get an aero front wheel”. At the rear you have more than just the seat tube to deal with. The fact is, air moving over the rear area of the bike has to deal with seatpost, seat stays, YOUR LEGS, etc., etc…that’s a lot of dirty air that the disk won’t help a lot with except to start putting the air back together at the tail end of the bike. Is a disk faster than a standard wheel on the rear? Hell yes. Is it anywhere near as fast as a good aero front? Not even close. Spend your money wisely, not on what looks cool or even looks “right”. Lets face it, an H3 front/standard rear would look silly to the unlearned. But it would certainly be faster than a standard front/disk rear.
I agree completely…
A H3 front would be more effective than a disk rear. No argument. No discussion.
But a H3 or an Alps or a 404 costs more than a Renn disk. So if I “spend my money wisely” which do I buy? It’s a $/lb of drag saved question. Cost is a reality and must be factored into the decision for most athletes. If cost isn’t an object then why are we having this discussion? Buy 6 sets of wheels for every type of condition.
I thought I made that clear in my first post.
Buy a good front AND rear, eat Ramen for two months, and none of this will matter.
it’s all about the watts my friends. sure your rear wheel is spinning behind a down tube but it’s not spinning in a vacuum. it takes energy to spin that wheel. roughly, a disc wheel uses about 3-5 watts to spin at 25 mph the best spoked wheels use in the high teens. if you slap a deep section or an airfoil spoked wheel on the front without increasing the surface area to the rear wheel you will have a large amout of instability and it looks goofy.
frank rehnelt, renn multisport
that’s not the point, that’s a whole other discussion.
at 25m/h what counts is aerodynamics.
make a back of the envelope calculation…the 7watts difference at 25m/h doen’t get you any faster when facing the wind at that speed.
Your Disk is cool man, way cool but you have to agree that at 25m/h you gain way more from an aero wheel at the front end if you disagree with that I would have to seriously doubt your knowledge to build an aerowheel, cause you’ll have a lot of big names against you (not me, I’m nobody).
thanks for making that great disk, which makes it finally afordable to buy one (after buying a front aerowheel and probably also a backaerowheel but not necessary).
And the numbers on the HED website…that’s one company promoting their own wheels. Don’t get me wrong they make grat wheels, I have a HED3 myself, the best wheel I ever had!
I’ll stop here because this discussion can go on forever. Ciao!