The blog post used a .023 reduction of cda to compare the "light" wheel to the "aero" wheel to draw their conclusions. Can the smart people translate how many grams of drag .023^m is approximately worth? That seems like A LOT for wheels.

In terms of this thread's discussion, nobody is advocating using a box 32 spoke wheel over an aero wheel. But if you have something like the AL33, XR31, FLO30 compared to a Jet 6, how much of a aero difference are we talking about. If all of those shallower rims can be built up 200g lighter than the Jet 6, then what really is the net difference when accelerating?

I have a similar custom build (White industry hubs and CX-rays), but different rims. These are classy wheels.

Maybe it will blow my mind, and I wish I could justify a set of light wheels to find out. But that doesn't mean it's faster.

Review the other examples presented in the linked sources in Alex's article:

http://www.biketechreview.com/...63-wheel-performance

https://www.slowtwitch.com/...nd_Inertia_2106.html

If you are near a Performance Bike Shop you might still be able to find a set of HED Jet 5+ for 600$. That is a great set of wheels.

As someone else mentioned, the Bontrager Aeolus 5 Comp is a great wheel and sub-600$. They aren’t quite as wide as the Jets, but still accept a 25 with no issues. Register for a Trek email alert and they will probably send you a promo catalog with a 20% coupon on the back cover. They are also pretty common on eBay.

I never said it was faster. I said it feels different. A lot different. (Thought it is faster at low speeds, before aero takes over. But, none of us are riding at low speeds, right.)
Rotational inertia is proportional to the square of the radius of the rotational distance. So, it is not limited to 2x. It can get infinitely greater. I just picked 4x from another bike blog because I was too lazy to do the math myself to figure out the exact factor for a 311mm radius axis. I'm still that lazy. But, here's the formula for rotational inertia for a thin-walled cylinder (basically a bike wheel).

I = mr2

The main reason I suggested HED Ardennes is because they corner so well for me and you mentioned you were going to be racing crits.

I got a set early last year and took them to the mountains in Georgia near a city called Helen. I've ridden there many times up and down the mountains. I'm a fairly decent descender but when I used those wheels my bike felt like it was on rails. Taking the hard turns downhill at high speeds was easier than other wheels I've used.

Since they rode so well for me I felt that you would benefit from their performance as well.

This. I haven't raced criteriums in 30 years, but I am surprised that aero is such a strong discussion topic today for criterium racing. I always thought of criterium racing as lightest, most agile, quickest bike for burst accelerations and instant handling. I never recall wind playing much of a factor in my races. Maybe it was there, but it did not seem like it given the locations. And, I did my fair share of lead outs, but I was not often pulling alone for long.

The aero wheels in the discussion only begin to meaningfully separate for yaw angles that are higher than 5%. How likely is anything above a couple percent yaw in a criterium? If rare, then a 90mm aero wheel would be no different from a ~30mm wheel. And if that is true, I would pick the absolute lightest wheel that met aero minimums.

Shh... don't tell Howard!

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The point is, ladies and gentleman, that speed, for lack of a better word, is good. Speed is right, Speed works. Speed clarifies, cuts through, and captures the essence of the evolutionary spirit.

I feel like I am over-posting on this thread, but I have continued to ponder this... Most of the analyses like these focus on a few simple steady-state scenarios, like a solo TT, a hill climb, something with moderate rollers. Most of those situations have one major acceleration from a stop, and then bank on the conservation of energy over the hills.

But, I wonder if anyone has modeled something like a 40-lap criterium, where you may brake and accelerate 160 times around the corners plus a bunch of other times that the pack bunches and then opens back up. And, you are in a draft almost all the time. So, those couple-hundred accelerations become a pretty big deal. If you are mid-pack in a criterium behind the draft of other riders, how much impact would slightly more aero wheels (at >5% yaw) matter compared to the lower power require to re-accelerate lighter wheels?

Yes, all of our bearings are sealed cartridge bearings and replaceable.

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

Chris,
I see on your website the "pre 2015" and "after 2015" FLO30's use different bearings. Is there an easy way to identify which ones I have (other than a receipt, which I don't have)? Thanks!

Also I see posts here referring to:
HED Jet 6+ can be found for under $1000.
HED Jet 4/5 can be found for well under $1000 .

Where can these be found? I can't seem to find them anywhere.

All FLO 30s will use the 2012-2015 bearings sets. If you're doing a rebuild, buying a new freehub is easier than trying to replace the bearings inside of the freehub. You can replace the hub shell bearings on the front hub (2 bearing total), the hub shell bearings on the rear hub (2 bearing total), and then add a new freehub which will cover the other two bearings in the rear wheel.

If you have any questions, please let me know.

Take care,

---

Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

If we're talking about the direct effect that it has on acceleration, the question isn't the rotational inertia, but how much rotational energy is required to bring it to speed. That's .5*I*w^2. And w is v/r because bigger wheels rotate slower for a given bicycle speed. So:
E = .5*(m*r^2)*((v/r)^2)
= .5*m*(r^2)*(v^2)/(r^2)
=.5*m*v^2
Which is equal to the linear kinetic energy for that mass. Hence, it requires double the energy of non-rotating mass. The rim's mass is basically being accelerated to the speed of the bicycle in two different ways: once in the direction of the bicycle's forward movement, and once around the hub.

Now, inertia might be interesting if we're characterizing interactions between the bicycle and the rider. But I don't know how well anyone has ever characterized that...

If it's just the bearing... cheapest will be to replace them. Otherwise the Jet 5/6+ would be a nice wheel as well as the Flo 60s. IMO

^^^^

The Hed Jet 6+s go on and off sale. I got mine for 899 from Competitive Cyclist last year. They're not on sale now. The 5s are 1299 at mybikeshop.com now. I have not seen the 4s at under 1000.

I have a set of Flo 30s. I also have a set of the Hed Belgium C+ rims built with CX-Rays on American Classic hubs. The Flos are around 130 grams heavier. I have used both in crits and can't really tell the difference in a race. My Heds were around 750 and are just under 1500gms.

Flo is clearing their 60 aluminum rims at $199 (28 and 32 hole available. The Hed Belgium C+ rims are $150. For the extra $100, I'd consider building the Flo 60s on hubs of your choosing. If you increase your budget to $1200, I bet you could build them on a Powertap G3 hub. If you weren't concerned about the carbon rims, you could buy the AMP35/50 wheels from Powertap for $999. They had a 30% coupon back in December, but that may not be available.

A single good front aero wheel will be ~.018m^2 at zero yaw. A good ~30mm wheel with minimal aero spokes would be ~.020m^2. Figure maybe half that difference for the rear, so .003m^2 total, compared to a total CdA of ~.30m^2 for crit racing? So the drag difference is only 1% or so, maybe up to 2% if you have higher yaw. The .023m^2 example must be for really shitty wheels. But on the other hand the difference in weight isn't that great either. 300g (x2 for acceleration) out of 85,000g is only 0.7% difference.

The decision about rim depth for racing will depend on what sort of move will result in your best chance of winning or placing. Nobody wins a crit if they are constantly slowing down and speeding up, as that will wear you out in a hurry. You need to be near the front and stay there. Riding at a semi-steady pace will favor aero even when drafting. Occasionally putting your nose in the wind will favor aero. A solo flyer will favor aero. Sucking wheel the whole race with a sprint at the end might favor light wheels.

If you want light wheels, don't even look at clinchers. Get carbon tubulars.