Wheel Aerodynamics

Everything about building wheels, glueing tubs, etc.
CAAD8FRED
Posts: 226
Joined: Mon Jun 18, 2018 10:52 pm

by CAAD8FRED

3T claims there 45mm deep wheels that have a 32 mm width are more aero than their slightly narrower 60mm deep counterparts. Is this unique to the 3T design, or are wider, shallower wheels more aero?

jfranci3
Posts: 724
Joined: Tue Jul 26, 2016 5:21 pm

by jfranci3

https://www.cyclingweekly.com/news/prod ... ics-410068

This?
Because they are using a 30c tire and are cutting the yaw off at 7.5 degrees.

by Weenie


CAAD8FRED
Posts: 226
Joined: Mon Jun 18, 2018 10:52 pm

by CAAD8FRED

jfranci3 wrote:
Wed Apr 24, 2019 3:12 am
https://www.cyclingweekly.com/news/prod ... ics-410068

This?
Because they are using a 30c tire and are cutting the yaw off at 7.5 degrees.
Yea that. I’m a little unfamiliar with how tires affect wheel aero. Does a tire narrower than the widest point of the rim make it more aero? Wouldn’t the air still need to pass over the wider section at some point?

Edit: Enve 3.4 AR (disc) is 32 mm wide, do you think it would demonstrate similar qualities to the deeper, but narrower 4.5 (disc)?

alcatraz
Posts: 2257
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Use only as wide a rim and tire as you need to achieve adequate comfort or rolling resistance. Weight and road quality play a role here.

On the rear you can balloon the tire a tiny bit but avoid doing that in front.

Manufacturers claims are often exaggerated. I only read it as a dessert of fiction once I've already made up my mind to buy something.

robeambro
Posts: 616
Joined: Sat Jul 07, 2018 6:21 pm

by robeambro

CAAD8FRED wrote:
Wed Apr 24, 2019 3:55 am
jfranci3 wrote:
Wed Apr 24, 2019 3:12 am
https://www.cyclingweekly.com/news/prod ... ics-410068

This?
Because they are using a 30c tire and are cutting the yaw off at 7.5 degrees.
Yea that. I’m a little unfamiliar with how tires affect wheel aero. Does a tire narrower than the widest point of the rim make it more aero? Wouldn’t the air still need to pass over the wider section at some point?

Edit: Enve 3.4 AR (disc) is 32 mm wide, do you think it would demonstrate similar qualities to the deeper, but narrower 4.5 (disc)?
Plenty has been said about this. Without over complicating the matter, to fully optimise aerodynamics your tire should not be wider than the rim (in fact it should be very slightly narrower). In other words, you should try to match your tire and wheel width.

So it all depends on the tire/wheel combination. If you want to fit a 28/30mm tire (actual size, not claimed), then look for wheels with similar or slightly higher width. Among those, most likely the deepest will have better aerodynamics.

You will now understand that your question about Enves is irrelevant :)

bm0p700f
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Location: Glermsford, Suffolk U.K
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by bm0p700f

There new 45mm wide rim with a 30mm tyre maybemore aero than the 60 mm rimmef wheel with the same tyre but that's a fudge if that deeper rim had a tyre appropriate for its width it would be more aero.

Wider tyres cannot be more aero. They have more frontal aero. Rim and tyre width need to match.

For mettled roads 30mm tyres are getting a bit wide. I was riding first bridleways on my road race bike with 25mm tyre on Monday. 30mm tyres would have been better there but that's off road. Also off road speed is slower so how aero your wheels are becomes moot.

These aero wheels for wide tyres are utterly pointless unless you only racing on cobbles with them, which is not how most people ride.
Last edited by bm0p700f on Wed Apr 24, 2019 1:30 pm, edited 1 time in total.

alcatraz
Posts: 2257
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

I also find it interesting how wider tires don't need to be high performing in rr/aero.

If performance is important you'll notice a 25C tire balloons like crazy on a wide rim so you'll never really need 28C tires unless you are on 32mm rims and possibly only in the rear.

So I'm a bit puzzled why for example conti are phasing out 23C tires on tubeless performance gp5k and introducing 32C. Schwalbe makes more sense offering 23-28C.

Anyway, I'm offtopic...

TobinHatesYou
Posts: 4295
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

To me, the comfort gained from measured 31mm tires outweighs the slight aero gains achieved with measured 27mm tires in basically any road race. Even crits where positioning is key and being able to rail corners 1mph faster than others is huge. The only times I don’t want a wider tire is in a race against the clock like a TT.

My next set of wheels will definitely be 31-32mm wide.

robeambro
Posts: 616
Joined: Sat Jul 07, 2018 6:21 pm

by robeambro

I second the above.

Aerodynamics studies as we've seen for frames (XXs faster in a 40k TT!!), or wheels (X watts at 45kmh!), rolling and ideal pressure tests on tyres (X watts in RR gained on a nearly-smooth surface at X PSI!) are indications. Nothing more. It is science, but it is not some kind of immutable law of physics, that translates equally from the lab to the road.

Yeah sure, Tour Magazin tested via modelling that aero frames are faster even on an hilly course. However, I'd be curious to see how they modelled the descents, where in theory an aero frame is faster if it is a straight lane with no corners, but in practice it may be very technical and not allow an aero frame to gain as much, since it would not really reach such higher speeds - the Cannondale whitepaper talking about terminal velocity on a descent is really funny to read on this regard. (Not to mention that in a race setting, all of this modelling is thrown out the window easily).

Yeah sure, that aero frame that is tested to be 10w faster at 45kmh? For a short crit that sounds awesome, but what if after one hour sitting on it my core, my entire body starts aching cause the frame is too stiff for me, and I can't put out as much power as I would on a slightly more forgiving frame?

Yeah sure, deeper wheels have better aero, but what if we corner slower as a result of crosswind sensitivity? Do we still gain overall?

Yeah sure, bicyclerollingresistance seems to imply that some tires are faster, and higher pressure is better, but what is the ideal tire pressure on MY roads? The pressure that will reduce rolling resistance and whatnot? The pressure that will allow my body to stay in an aero position throughout the ride without pain? And what if the fastest tire does not inspire me confidence when cornering?

Disclaimer: I do not hate aero, in fact I am an aeroweenie, but I like to take things with a pinch of salt. These are all questions that lab tests DO NOT answer and that a lot of people on this forum DO NOT ask themselves. Besides training, looking at the data from a critical perspective and finding the bigger picture is what will make you faster.

TobinHatesYou
Posts: 4295
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

It’s obviously not about hating aero. I want the most aero rims for the tires I ride...that means 31mm or wider. 3T, ENVE, Cannondale, HED, and a few others get it.

bm0p700f
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by bm0p700f

Im just old fashioned and think tyre are wide enough. I would dispute the claim that wider is not a penelty if you doing a race averaging 40kph a narrower tyre will be faster unless it's an off road crit. Not sure there are any of them.

Not all 25mm tyres balloon on wide rims.

Gravel bikes are turning into xc bikes and road bikes are morphing into gravel bikes.

The roads are bad in the u.k and still 25mm tyres ( the right ones) are quicker. There no way they are slower.

AJS914
Posts: 3539
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

I've love a 30-32mm wide rim running a 28-30mm tire. There are so many sections of rough, bumpy road where I'm pretty sure that a 50-60psi tire would be faster.

I'm stuck though at 27mm (25mm GP4000) and 75/80psi is as low as I'm comfortable running.

BoSoxYacht
Posts: 109
Joined: Thu Oct 01, 2009 8:39 pm

by BoSoxYacht

AJS914 wrote:
Wed Apr 24, 2019 5:11 pm
I've love a 30-32mm wide rim running a 28-30mm tire. There are so many sections of rough, bumpy road where I'm pretty sure that a 50-60psi tire would be faster.

I'm stuck though at 27mm (25mm GP4000) and 75/80psi is as low as I'm comfortable running.
BoSoxYacht wrote:
Fri Mar 29, 2019 3:46 pm
Light Bicycle 56mm deep (23.09mm internal, 30.47mm external) and 30mm Schwalbe G-One Speed tires, measured 31.65mm @ 60psi.
It's like riding on a cloud

bm0p700f
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Location: Glermsford, Suffolk U.K
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by bm0p700f

There may be a few section of road where a 30mm tyre is faster but not your whole route.

I know when putting 28mm real width tyres on the same rims in my look and 24mm real width tyres I am not slower on the narrower tyres. Difficult to say if I'm faster as there too many variables on the road but having ridden a 200 mile ride on the narrower tyres there are no comfort issues I did not get with the larger tyres on solar length rides. Same tpi too for the differing within in fact the same tyre.

TobinHatesYou
Posts: 4295
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I used to think 25mm would be ideal particularly for racing until I started actually doing it. bm0p700f, it’s clear to me you don’t race at all. For any remotely lumpy race right now I am using 202s with 28s, reserving my 5.6s with 25s for only the smoothest courses and non-technical crits.

Reduced fatigue = free speed
More stability = free speed
Confident cornering = free speed

Even TT/Tri guys are switching to 28s.

And of course all of this applies to daily riding as well.

by Weenie


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