Aero data from 19 wheels by Hambini

Everything about building wheels, glueing tubs, etc.
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by hambini

C36 wrote:
Fri Oct 19, 2018 5:30 pm
2 questions I am curious about.

- From the transient to stable drag it appears that even after 10 seconds we are still in transient state how long would it take to reach steady-state under ideal conditions (ballpark number)?Image
10sec is already extremely long to expect that nothing change (not counting bike movement).
- once we are in steady state (if it’s achievable in normal life) does it require a lot to lose it and go back to a transient one? Let’s say on an indoor velodrome, could the front wheel movement be enough to alway be in transient state ?

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In testing in the field, none of the measurements indicate the flow to ever be steady. It is always in some sort of transient state.

In a wind tunnel where you can fix the bike down, it's still not steady because the bike wheel is not perfectly symmetrical. You have spokes that come around 20 times per revolution to disturb the airflow and a valve that comes around once per revolution to disturb the airflow. So even if it's steady over the leading part of the front wheel it is definitely not over the trailing part of the front wheel.

However, for practical purposes, you are asking how long it will take for the flow to settle. Usually about 2 seconds at 30km/h. It gets less the faster you go.

HOpe that helps

by Weenie

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by kgt

hambini wrote:
Fri Oct 19, 2018 9:42 pm
Personally, I would rather ride on something that felt better and sacrifice the extra weight and 2W of Aero that I can gain by wearing hair gel under my helmet.

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by Stueys

Is it possible to quantify the advantages a disc specific rim gives? I’ve always assumed that a disc rim would be more aero as the engineer hasn’t had to disrupt the rim shape to cater for a brake track. But I’ve never seen any data on that.

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by Marin

hambini wrote:
Fri Oct 19, 2018 9:42 pm
rims with a novatec hub (Hunt)
Hunt use Hubsmith hubs I think. They don't look like any Novatec I know.

BTW I'm running Novatecs on most wheelsets now and they work very well for me.

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by bm0p700f

Hunt used to use novatec FS522-SL and the front AS511SL but they have changed to another manufacturer.

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by hambini

There has been a bit of speculation as to which companies sent the legal letters. To clarify, it was not Mavic.

A suitably sarcastic reply has gone back to the solicitors of the "influencers"

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by Calnago

I still think that if there is no merit in the letters received then you should have no worries about naming them and publishing those letters. If, on the other hand, you feel their threats have any merit at all, then best to keep them to yourself.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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by RyanH

Except that what has merit and what can cost you money (legally) are two different things. Hambini is fortunately in a more advanced legal system than us where you can actually be reimbursed for frivolous lawsuits, so at least there's that.

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by KotP

I think most guessed it wasn't Mavic ;)

While I know I'd love to see the legal threats, for reasons already stated I understand if they're not. But as a watcher of Hambini's videos for a while now and as he's not averse to occasionally calling out people as "c**ts" I'd truly love to see his reply to those legal threats. They're sure to elicit a chuckle :lol:

While far more advanced and technical, Hambini is sort of doing what weightweenies do when a manufacturer claims 800g for a frame and they post a photo of said frame on a scale reading 890g, if there's something wrong with that expect the courts to get inundated.

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by Philbar72

Stueys wrote:
Sat Oct 20, 2018 12:34 pm
Is it possible to quantify the advantages a disc specific rim gives? I’ve always assumed that a disc rim would be more aero as the engineer hasn’t had to disrupt the rim shape to cater for a brake track. But I’ve never seen any data on that.
would that not at least partially be offset by the brake itself.

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by Hexsense

Before a disc vs non disc version of the same rim, which is really hard to make a ton of things arguably equal and i'm not sure about usefulness,

How about disc vs disc first?

For people who already own disc brake aero bike,
Do Shimano's aluminum fan filled disc rotors more or less aero than shallow section normal looking Sram Centerline X (centerlock version, to make things equal) rotors?
Deep section rotor might win against shallow section rotor, just like deep disc wheels against shallow wheels. But Shimano's rotor (Dura-ace, Ultegra) are also so much wider than standard rotor at their fan blade and 'four spoke' arms. So i don't know how to guess the result.

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by TobinHatesYou

The airflow over the rotor is very turbulent, so the finned Shimano Ice-Tech rotors would do little to improve a bike’s aerodynamics.

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by antonio07

Help anyone ??
On the chart there is 2 Mavic Cosmic
One is the exalith braking surface 45mm and which one is the other Mavic Cosmic 45mm ??
Which is significantly worst at 50km/h ??


Last edited by antonio07 on Fri Oct 26, 2018 5:04 pm, edited 1 time in total.

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by ericoschmitt

Yes, Yoeleo prices have went up some $200 per pair, and they are aware of this test and thread. I checked their website a couple days after this test was out, and again now, and prices are higher.

by Weenie

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by AJS914

They have priced me out. I'm looking at Farsports or LightBicycle.

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