Any question answered...

If you speak of carbon monocoque spoked ones, couldn't a certain degree of off centre to the spokes give more fluidity instead?

Btw just found this

If you speak of carbon monocoque spoked ones, couldn't a certain degree of off centre to the spokes give more fluidity instead?

People have tried various degrees of sweep (both ways) and taper (also both ways), including scimitar blades and even left/right asymmetry, but none has been demonstrably superior to the 30 year old Specialized (now HED) design with its radial, constant cross section blades.

Does anyone know what time the Tour of Britain eighth stage starts on Sunday? The website seems to skip such useful info.

First rider at 11:01 for the TT, 15:30 start for the road stage. It's all in the race manual

Cheers, I was expecting it under the spectator section.

In reply to @mdcc_tester

Tnx tester. I wonder why wheels don't come with a drag coefficient. It's not hard to calculate. Put them on a work bench at a constant temperature, rotate them at a given speed and see when they stop.

Possibly because wheels tend to move through the air when they're turning. When they're on a bike. Hence the existence of wind tunnels.

Don't know if @danstuff is saying the same thing, but wouldn't that just measure the friction of the bearings not the wind resistance?

I guess both, and both are important. Even if not 100% reliable would still give a good idea?

Spinning the wheels stationary and riding into the wind at 30mph are two completely different loading situations. How long the wheels spin stationary is going to be a reflection of the moment of inertia and the friction in the bearings, not its real world aerodynamic properties.

It all depends on the speed you spin it. The faster, the more the aero intervention counts. But agree it's not the same thing

Is this for a slave bik?

No, it's to get 2 seconds earlier to the pub in a boris bike. I thought I could bend the spokes with my bare hands and teeth just before inserting the key. Only if the electronic chip hasn't already magically escaped from it in my pockets and implanted itself under my skin, giving my exact location to the Russian secret services and making me surrender to communism while quickly transforming me in a radioactive bald old man

oh
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I wonder why wheels don't come with a drag coefficient. It's not hard to calculate.

Wow, you really don't understand either wheels or aerodynamics do you?

It turns out that calculating the drag coefficient of anything is tremendously difficult, and measuring it isn't any easier. You need either a really big supercomputer or a big expensive machine, and you still only get the answer for the particular circumstances you've calculated/measured. Wheels are almost the worst kind of thing, since they roll along the ground. For example, a glider once it is out of ground effect and in coordinated flight is a pretty trivial problem compared with a bicycle wheel.

The total aerodynamic drag of a wheel (disregard rolling resistance and bearing friction for the time being, they are actually much easier to evaluate anyway) is the sum of the force needed to spin the wheel in a given flow stream plus the force needed to hold it still in the given stream. The characteristics of the stream will depend on what else is in the locale, typically the rest of the bicycle with its rider and a ground plane. The characteristics of the bicycle can have quite a large effect on the amount of drag added to the whole by the wheels, and the effect will vary with different wheels, so the lowest drag wheel will be different for different bicycles.

Even after you have found the drag for the condition of zero bulk stream velocity relative to the ground plane and zero yaw, you haven't really found a good way of ranking bicycle wheels, sine we seldom ride in such conditions. Even on a velodrome, a bicycle experiences yaw during cornering, and outdoors we have wind, which can add a fair amount of shear in the stream, since the boundary layer attached to the ground plane is right next to the wheel.

Even beyond mere drag parallel to the direction of travel, we have lift (aerodynamic loads which tend to push the bike sideways) and torque (loads unevenly distributed about the wheel centre which tend to steer it), both of which are significant factors in wheel selection.

My bad, didn't mean an absolute final coefficient true for all conditions. Just a compromise to easy rank them. A rolling drag? Wouldn't in most cases, wheels spinning for longer on a work bench after being launched at some considerable velocity, like twice as fast as they would on the road, or causing least drag in a wind tunnel give the same kind of results if pitched against each other? Just a twisted thought. Btw thanks for your time tester. And one more question pls. Why many carbon spoked wheels have drop shaped spokes' sections rather than knife sharp? Has it got to do with crosswinds or maybe safety? Tnx again

Wouldn't in most cases, wheels spinning for longer on a work bench after being launched at some considerable velocity, like twice as fast as they would on the road, or causing least drag in a wind tunnel give the same kind of results if pitched against each other?

No. The spin and run-down test tends to be dominated by moment of inertia. After you've equalised for that, by ballasting all the wheels to have the same I, and taken bearing friction out of the equation by mounting all the wheels on a reference axle, you end up measuring mainly spoke drag, so spoke section and spoke count tend to be favoured over rim shape.

If you measure drag of an isolated wheel in the wind tunnel, all you're measuring is the drag of an isolated wheel. Not very useful, since the wheels interact so much with the rest of the bike. You can generate a ranking of wheels that way, and people do, but it's a crude measure. Usually people measure power needed to traverse (and maybe rotate, although few bother with this even though it turns out to be quite significant) at a given speed, giving results ranging from <20W to >30W per wheel at 50km/h. If there's a huge difference on the isolated test stand, it's pretty likely that the rank order will not change when mounted on a bike, but the real fight is over single Watts, and for a group of wheels which are all within ±1W on a test fixture, the rank order is likely to be different on each complete bike to which they are fitted.

innit

Tnx. Yes, I didn't take inertia into account as different weights and different weight distributions would corrupt the results. So in theory you would have to take into account and subtract the force needed to spin them in the first place. It starts getting ugly. All of these thoughts started because I'm in the process of ordering a new set of traditional wheels where I can decide the spoke arrangement and rim profile heights. I will probably go for a smaller rim at the front with radial spokes and taller profile at the back with x3 pattern. Classic. Cheers

New one is 11spd, hence the bump in price.
Also, 105 cassette over tiagra.

11spd 105 is cheaper RRP than 10spd.

Then I give up and will have more coffee.
Maybe they're just being cheeky and trying to put the bump down to that?

Cheers, that worked.

I want to get a new helmet and also a new bag (backpack/messenger bag) for riding - but would like to try on both. Where might have a large stock of these things? I'm happy to shop around, I don't need either in a rush.