Just finished my gravel build with Industry Nine Ultralight 235 TRA wheels and while I love the wheels, the spokes are huge and round. I’m curious to know what the aero penalty is going from bladed spokes to round spokes, to I9 TRA spokes. I realize gravel culture kind of ignores aerodynamics but the road-side of me is pretty concerned with aero stuff and my A gravel race is flat and fast.
Well there is 100% a penalty. I’m not sure it is something I would stress about though. I don’t have data in front of me, but I know it is out there. If I remember correctly you’re losing a few watts; probably you can count the difference in watts on one hand.
Keep in mind that the I9 aluminum spokes are HUGE vs to those round steel ones tested in the comparison above (and most other similar ones). So the advantage of a bladed steel spoke over the round aluminum I9 will be more than just about any listed tests (unless someone actually tests them).
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9s over a 40k TT according to their result. I would imagine since surface area is linear, twice the area would yield twice the time loss, or 18s over about an hour. I feel like that’s not much.
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Some. I’d expect more than what was indicated by that Flo study because of both the spoke size as Chad mentioned and I’d expect that a gravel race would see higher average yaw angles than you’d see at road speeds.
Probably some. Not enough to lose sleep over that’s for sure. .
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I really wouldn’t worry about it.
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The FLO test seems somewhat flawed. They used a Flo 30 wheel which has the longest spokes. Anyone that cares about aero doesn’t ride a TT with a 30mm wheel. My guess is that if they did the same test with 60/90mm wheels or 90mm/disk wheels the difference would be much less. But hey, maybe even 5 seconds is meaningful at elite level for a 40k TTs.
In the case of a gravel build, the lack of aerodynamics on your big fat gravel tire on the leading edge will certainly dwarf any tiny gain you’d get with aero spokes.
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Even 20s over 40k is like 3W
Yea, I’m not looking to change anything. I was just curious since the spokes for these wheels are huge.
Better to have some durability out on trails than skinny spokes!
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For sure. So many more considerations for gravel.
To be fair though, giant unaero tires will not lessen the benefits of aero spokes. At least J doubt it would…
I’d get em cos they’re good spokes, if I was getting new wheels made. But it’s not a worthwhile investment if you already have good serviceable wheels, if you’re only hoping to save time.
Round spokes for sure have some aero penalty associated but it’s not dramatic. Definitely non-zero but also definitely not first order. Other things to consider! You will also notice aero spokes will make cross wind riding considerably more twitchy…AND if you do decide to go with aero spokes make sure the spoke is absolutely parallel with the track of the wheel. It’s easy to get them a little off & then you’ll have an overall aero penalty vs round spokes instead of an advantage. Heaven forbid one of your aero spokes works its way to an orthogonal position.
I would have said the opposite but different regions probably do different things. I think one of the most charming things about gravel is that you can run whatever in the heck you want & anybody who doesn’t like it can get stuffed. So if you want aero spokes I say get alternating fluoro yellow & fluoro orange aero spokes.
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throwing away watts, do you have aero bars?
Haha I did consider getting the anodized spokes… But the shop gave a good deal on the wheels when I bought my frame so they are what they will be. Can’t change them now.
The region I’m in typically has super hilly gravel races so I’m confident in my wheel choice but always looking to understand aerodynamics more, especially with this flat race I’m doing later this year.
No, nor do my bars have any purchase area for clamping. Most races around here are too hilly and this flat race will be more like a road race with a front group pace-lining. I don’t expect to be hammering solo off the front.
Basically this. You do lose watts with the extra drag from round spokes, but not really because the rim and tire son’t make a tidy leading edge.