aero wheels - what effect do they have?

MattFT

OK, so I've figured out that for climbing, you want the lightest things you can get, as long as they're stiff enough.

But aero - when and where would you use aero wheels? I get the TT thing. But would you use them, e.g. for a sportive or group ride in rolling countryside?

Is there a best "all round" wheel of, perhaps, 30mm deep section but as light as you can get it?

Mr752

An aero rim of 40-60mm depth doesnt have much effect on performance until you spin it up over maybe 20mph. They are very good when you ride fairly flat routes, fast. Some can be a handful if you hit crosswinds. They wont magically make you quicker, you still have to have the abilty to get them upto speed and hold them there.

greasedscotsman

Mr752 wrote:

An aero rim of 40-60mm depth doesnt have much effect on performance until you spin it up over maybe 20mph. They are very good when you ride fairly flat routes, fast. Some can be a handful if you hit crosswinds. They wont magically make you quicker, you still have to have the abilty to get them upto speed and hold them there.

And they make your bike look cool...

Lemond75

Have a read of this:

http://www.rouesartisanales.com/article-15441821.html

Surprised me how little difference there is in terms of aerodynamic drag between wheels and how little difference wheel weight makes in terms of inertia. Whilst the pros will be looking to gain those extra couple of watts each aspect of wheel design makes, for the average rider it's barely discernable. It also makes you question the comments you read so often in magazines and on forums such as this that light wheels get up to speed so much more quickly than heavier wheels.

Having said all of that I've got some Mavic Cosmic Carbones and they make me feel like I'm going faster than my standard wheels cos they look good and sound great.

The power of the mind.......

sungod

the faster you go, the more benefit from better aerodynamics, power rises as the cube of velocity

but the % of total drag that wheels represent is small compared to the biggest lump - the rider - so good position is important

saving weight will reduce total energy needed to climb a given distance, but again the biggest lump is the rider

when climbing it's not common to brake, so acceleration losses are minimal, compared to a rider+bike weight of, say, 80kg, cutting 400g on wheels will give a 0.5% energy saving

if you are doing a lot of accelerations, coming out of corners in a race for instance, light wheels can save a fair bit of energy, there may be more benefit here than for steady climbing

there's little public info on the aero performance of most wheels, and what there is from manufacturers is not consistent, so it is hard to compare, the data on that site mentioned by Lemond75 is probably the best independent info out there

if you use zipp's figures, for the 101 (30mm) they claim a 14w saving - unclear vs. what - but that figure is at 48km/hr, i think at 40km/hr the saving would be about 8w, and at 32km/hr about 4w

assuming the 101 is typical of 30mm wheels then unless you can do well over 40km/hr a lot of the time the benefits are small

i can't think of any 30mm clincher wheels that are especially light, so unless you are using tubs i'd either go for super lightweight shallow rims (use aero spokes) or a much deeper rim

to answer your final question, you really need to do the maths - a superlight rider will get a bigger % benefit from saving weight on wheels, but if you are a heavier rider, then on climbs where you can keep a reasonable speed, you may get more % benefit from deep rims than from light wheels

using the 400g saving above, assuming it's for light wheels vs. 60mm rims saving 27w at 48km/hr, if you climb at 300w going 23km/hr this saves 3w, so you'd have a benefit of 1%, vs. the 0.5% of the lighter wheels

MattFT

Thanks sungod and Lemond75. Very interesting stuff. So it's really only when you're really cranking that you're going to get the benefits of aero. And as I don't TT and mainly ride in groups, I'd be on a wheel most of the time anyway. I'm a 70kg rider, so perhaps light is the best thing to go for. And while I agree with you greasedscotsman, I'll save some cash and have a slightly less cool bike I think

P_Tucker

Lemond75 wrote:

Surprised me how little difference there is in terms of aerodynamic drag between wheels and how little difference wheel weight makes in terms of inertia. Whilst the pros will be looking to gain those extra couple of watts each aspect of wheel design makes, for the average rider it's barely discernable. It also makes you question the comments you read so often in magazines and on forums such as this that light wheels get up to speed so much more quickly than heavier wheels.

Marketing is brilliant. It can make people believe practically anything.

Anonymous

I've owned some 'top' carbon wheels but have had my best racing results when using a bargain basement A Class Alex Rims front wheel that came on my TT bike and open pro rear.
It really is marketing.

You do see the benefit in a TT though but even then, most of us are racing against ourselves so no need there either really.

They do look and sound good though...

Bar Shaker

sungod wrote:

when climbing it's not common to brake, so acceleration losses are minimal, compared to a rider+bike weight of, say, 80kg, cutting 400g on wheels will give a 0.5% energy saving

When climbing, you accelerate the wheels with every pedal push. On a steep climb, you may be going from 7mph to 10mph on every pedal revolution.

The inertial mass is very significant when climbing.

For the aero effect of wheels, consider that the top of the wheel (and especially the spokes) is travelling into the air at twice the speed of the bike. The spokes may well be hitting the air in front of you at over 55mph on a fast flat. They will create a lot of resistance.

oldwelshman

Bar Shaker wrote:

sungod wrote:

when climbing it's not common to brake, so acceleration losses are minimal, compared to a rider+bike weight of, say, 80kg, cutting 400g on wheels will give a 0.5% energy saving

When climbing, you accelerate the wheels with every pedal push. On a steep climb, you may be going from 7mph to 10mph on every pedal revolution.

The inertial mass is very significant when climbing.

For the aero effect of wheels, consider that the top of the wheel (and especially the spokes) is travelling into the air at twice the speed of the bike. The spokes may well be hitting the air in front of you at over 55mph on a fast flat. They will create a lot of resistance.

You go from 7mph to 10mph every rev? wow, is that possible?
So after 10 pedal revs your climbing at 37mph? 8)

oldwelshman

I use mine only in certain races and smooth roads.
The benefit is more noticable on the track especially for pursuit where speed is 30mph +.
Mine are expensive ones but to me they are not wort the money in my view I would even describe them as crap. They are stiff so the ride on our roads feels bumpy, the rear wheel flexes badly so not good for climbing and so bad it rubs on brakes so I have to open them.
I much prefer my dura ace clinchers for racing and they are much better for climbing.
For non racing, non TT ing riders who generally do sportives and club rides they are not much use.

sungod

Bar Shaker wrote:

sungod wrote:

when climbing it's not common to brake, so acceleration losses are minimal, compared to a rider+bike weight of, say, 80kg, cutting 400g on wheels will give a 0.5% energy saving

When climbing, you accelerate the wheels with every pedal push. On a steep climb, you may be going from 7mph to 10mph on every pedal revolution.

The inertial mass is very significant when climbing.

<...>

no

this argument has been beaten to death in other places

angular momentum is conserved

Anonymous

Light stiff wheels feel really great when climbing but you are talking a couple of seconds difference at most for me.
Fine if you have ambitions in a hill climb competition but in terms of time saved there is a lot of exaggeration and emotive language used in reviews.
If buying aero or light wheels, yes they feel great and look great and in the case of aero wheels, sound great, but be under no illusions that they will turn you into cancellara or contador.

That said, I'd always rather have light, stiff aero wheels in a race or on a big pleasure ride. Because of the placebo and nice feel.

sungod

^^^this

aero wheels are just more fun, the look, the sound, the feel

life is too short for boring bits

Lemond75

Looking at the results of the various tests on the rouesartisinales website the best overall wheel set looks to be the Shimano 7850 CL 24's. They found them to be almost as aero as some of the deep section wheels and performed well in the inertia test.

Shame I only found the website after I'd bought my wheels!

oldwelshman

Lemond75 wrote:

Looking at the results of the various tests on the rouesartisinales website the best overall wheel set looks to be the Shimano 7850 CL 24's. They found them to be almost as aero as some of the deep section wheels and performed well in the inertia test.

Shame I only found the website after I'd bought my wheels!

Seems like I chose well I have two pair of these and also a pair of rs20 which are very cheap and good enough to race on for sure.

Nap you must have great roads where you live mine feel great on smooth roads of ital but not on the pothole ridden and chipping surfaced roads of herts and beds.

Pokerface

Lemond75 wrote:

Have a read of this:

http://www.rouesartisanales.com/article-15441821.html

Surprised me how little difference there is in terms of aerodynamic drag between wheels and how little difference wheel weight makes in terms of inertia. Whilst the pros will be looking to gain those extra couple of watts each aspect of wheel design makes, for the average rider it's barely discernable. It also makes you question the comments you read so often in magazines and on forums such as this that light wheels get up to speed so much more quickly than heavier wheels.

Having said all of that I've got some Mavic Cosmic Carbones and they make me feel like I'm going faster than my standard wheels cos they look good and sound great.

The power of the mind.......

Doesn't that article say that a ZIpp 808 wheel can save you up to 15w of power at 50kph over some spoked wheels? From the Aero point of view? If so, that is a LOT.

P_Tucker

Pokerface wrote:

Doesn't that article say that a ZIpp 808 wheel can save you up to 15w of power at 50kph over some spoked wheels? From the Aero point of view? If so, that is a LOT.

Indeed. But how much time do you spend riding at 50kmh?

Taking the Fulcrum Racing 5s as a base case - they're £150 bog standard wheels - they're only 11w off the 808s at 50kmh. I believe (but am happy to be corrected) that air resistance increases as the cube of speed - thus at 40kmh (a more likely speed for amateur racers like us) the saving would be 5.6w - still worth it perhaps - and at 30kmh (a reasonable speed for a sportif) the saving would be 2.4w. And this ignores the extra weight of the 808s, and for the OP says he tends to ride in groups - thus lessening the benefit further.

So to sum up, the OP could spend an extra 2 grand and not be able to tell the difference outside of a lab - 2-3w is inside the quoted margin of error of every power meter on the market AFAIK.

Headhuunter

cadseen wrote:

I really notice them on fast going in road races, especially downhill.

As I am a light rider i used to have to pedal to keep up with heavier riders downhill.
With the deep sections i dont need to pedal if I dont want to.

Isn't that another myth? That heavier riders descend faster than light ones? I read or heard somewhere that it makes little or no difference. Not sure of the science behind it though....

pbt150

Nope, that one's true. A heavy rider will (normally) go down hill faster than a light rider because whilst they have ~the same air resistance, the heavy rider's gravitational potential energy can overcome it more easily.

They'd both go the same speed if they were descending in a vacuum.

Pokerface

Despite the 'science' telling me otherwise, for some strange reason I can't keep up on my club's fast chaingang when using my spoked wheels, but CAN when using my 404s.

Not sure if it's the aerodynamics, the placebo effect, better tyres or the pound of rotational weight that makes the difference - but N=1 - they do make a big difference to me.

starlet_gt

Headhuunter wrote:

cadseen wrote:

I really notice them on fast going in road races, especially downhill.

As I am a light rider i used to have to pedal to keep up with heavier riders downhill.
With the deep sections i dont need to pedal if I dont want to.

Isn't that another myth? That heavier riders descend faster than light ones? I read or heard somewhere that it makes little or no difference. Not sure of the science behind it though....

I'm 62kg's and have real trouble keeping up with bigger riders on the downhills!

MattFT

thanks all for your thoughts. So it seems like the science suggests the improvements are minmal. 2 or 3W isn't going to do too much for me. But the bling/placebo affect is something I hadn't thought about

sub55

MattFT wrote:

thanks all for your thoughts. So it seems like the science suggests the improvements are minmal. 2 or 3W isn't going to do too much for me. But the bling/placebo affect is something I hadn't thought about

Well that sort of depends, some of the posts that suggest aero wheels only make a difference at say 25mph plus are misleading, if not plain wrong. This was an old myth . The reality is ,in terms of time saved ,the slower you are the bigger the difference. This would apply more in a tt than a crit , granted. But the very fact that if your going slower, you`ll be out there for longer so the 3 watt saved , saves you more time overall.

rick_chasey

Aero-wheels, what effect do they have?

They make crosswinds more, erm, interesting...

Bar Shaker

Next time you are out on your bike, hold your index fingers pointing out straight, with your hands on the hoods. Point at, say / \ those sort of angles.

An aero rim will slightly reduce the drag from the air that your fingers are feeling.

It will probably reduce this drag by 50-65% for the forward facing quarter of the front wheel. The feeling on your finger will give you an idea of how much drag you are saving.

NWLondoner

Rick Chasey wrote:

Aero-wheels, what effect do they have?

They make crosswinds more, erm, interesting...

Thats ok.

i only ever seem to have head winds

Must admit to have been caught out once or twice with my EA90 Aero's. Last time was going around swiss cottage in heavy traffic :shock:

Serves me right for being a skinny fecker