Aero road bike wheels

[mat205125]

These aerdynamic wheels are used for time trials, triathlons, and for sprints, but the tour racers use "normal" spoked wheels for the main stages. Why?

[fixedwheelnut]

Mainly because they are a more comfortable ride and less prone to sidewinds etc which could cause havoc in group riding.
Aero rims are generally stiffer and give a harsh ride not good for three weeks in the saddle

[navier_stokes]

As said above. There are different grades of "aero" too though, from fully covered wheels, to ~2 inch deep sections to < 1 inch deep sections to no aero section at all. The no aero section have less inertia and so are used on hilly almost always used on medium to very hilly stages where as some people opt to go for the medium aero section wheels on some stages with fewer or less demanding hills.

Basically the larger the aero profile/section the less resistance and higher inertia meaning work on the straights is easier, but it also means slower acceleration and harder work up the hills.

Full aero:
http://www.parker-international.co.uk/ProductDetai...

Large section aero:
http://www.parker-international.co.uk/ProductDetai...

Shallow section aero:
http://www.parker-international.co.uk/ProductDetai...

No aero section:
http://www.parker-international.co.uk/ProductDetai...

[Nick_F]

Away from the mountains, most of the Tour field will ride on 50mm rims most of the time - although some will use a non-aero rim if it's very windy, as it was today.

Very deep section - 100mm - rims can be better than tri- or quad- spokes for the front without breaking the rules or behaving like sails, too. I don't know if the fact that the Tour is not a UCI-sanctioned event this year means that the rules are different?

[pawsmcgraw]

http://www.zipp.com/Portals/0/Technology/Documents...


This gives an idea of the areo worth, if with a little poetic licence from Zipp but its pretty near from the wind tunnel data i've read from various other tests.
I'd reckon now though, there's very little in it when it comes to running areo wheels, why wouldn't you unless your a fly weight or its rough as hell with cobbles.
A good example is Mavic ultimates are 1130g and zipp 303's the same, give or take a few grams.This is climbing wheel weights now, yet better than a climbing wheel on the flat?Its almost a no brainer!Even carbon sports(obermayer alp duez) pure climbing wheel at 960g the pair is an areo wheel.
The most areo wheel there is at present is a mavic IO , but at 750g its way heavy.
http://www.mavic.com/track/products/iO.M21101.aspx
There is a fair few combos in this years tour though, no uci, anything goes

Edited by pawsmcgraw on Tuesday 8th July 07:53

Edited by pawsmcgraw on Tuesday 8th July 07:54

[Sway]

The problem with using even very lightweight aero wheelsets in the hills is the issue of their weight distribution compared to normal rim section wheeelsets.

Rotating mass requires more energy to accelerate, the further the mass is from the axle the greater the effect. Extra mass placed in the hubs makes little difference, mass placed in the rims gives a noticeable effect. (there is a potential sidenote regarding schreader inner tube valves, water, and an unrideable shop demo!)

Aero rims are heavier than normal rims, but they use less or very light spokes and hubs as the rims are able to support greater loads. This allows for comparable wheelset weights.

They do however require a lot more energy to accelerate, as their mass is concentrated as far from the hub as possible, so still no good for hills.

As an ex Fir Antara user, I have to admit that for a day or two I'd still use aero, but then I've never ridden the Tour...

Sam

[pawsmcgraw]

I agree with your theory 100%, thats always the case hence why the tyre weight is of equal importance.However, rims today, such as a 303 zipp or a oberymayer, or even a mavic ultimate weigh in at sub 300grams.Ten years ago, this weight was unthinkable in an areo rim.Today, the purest of climbing rims isn't a significant amount less.

[Sway]

pawsmcgraw said:

I agree with your theory 100%, thats always the case hence why the tyre weight is of equal importance.However, rims today, such as a 303 zipp or a oberymayer, or even a mavic ultimate weigh in at sub 300grams.Ten years ago, this weight was unthinkable in an areo rim.Today, the purest of climbing rims isn't a significant amount less.

Fair play Paws, should have mentioned that my experience is five or six years old....

and you are indeed right about going for light tyres as well, although in my case my wheels were full carbons rims and therefore tubulars.

[homer mode] hmmm, tubs!![/homer mode]