Bike porn

Maybe these?

Maybe, they certainly look closer. I though maybe Ambrosio Excursion but again I haven't seen those with red decals.

Is that so the back wheel doesn't fill up with snow?

Had some (mylar?) covers back in the eighties that would convert your spoked wheel into a disc. Rubbish idea.

^
Froome?

You no know John Tomac? Sheeeesh. Kids.

Does this rely on a optimum speed?

Yes, speed is one of the factors used to calculate a drag coefficient. IIRC that drawing's from a NACA paper, so I suspect the relevant speeds are rather higher than those achieved by most bikes.

blah blah Reynolds Number blah blah fineness ratio blah blah.

Basically, a circular cross section will get flow separation at a very low speed. The higher the speed, the longer the aerofoil has to get to avoid this. You always trade induced drag (shit that happens in the wake vortex, plus pressure build up on the nose) for skin friction (shearing between the boundary layer and the free stream), so each aerofoil is optimised for a specific speed. For bicycle frame tubes, the ideal fineness is somewhere around 6:1, i.e. the tube depth parallel to the flow should be around 6 times its width. The UCI limit on depth (orthogonal to the tube axis) of 3 times the width doesn't let you achieve this even after taking the angle of the tube axis relative to the free stream into account.

Interesting.

6:1 would mean a ~120mm rim depth. ish. Would they be unridable? Or are wheel rims subject to the same 3:1 rule?

UCI don't limit rim depth, but CTT do, in effect. Wheels are more complicated, though, because the rim is spinning too, generating a bunch of extra skin friction. The old Zipp 1080 was about 130mm deep once you include the tyre, so clearly such a depth is usable on front wheel.

...the rim is spinning too...

Right, hence the use of golf-ball dimples.

http://www.kumocycles.com/uploads/5/3/3/9/5339917/7826496_orig.jpg

Right, hence the use of golf-ball dimples.

Golf ball dimples aren't there because the ball is spinning, they are there because they delay the flow separation. They only have to be all over the surface because you never know what the orientation of the ball will be. On a sphere which is constrained from rotation (e.g. a motorcycle helmet) you can achieve the same gain by adding a trip at the right place, without the losses you get from roughening the whole surface of a golf ball.

Yes, I meant golf ball dimples on Zipps rims (which spin). I guess rims can't use a trip.

They could, other rim manufacturers do.

We'll give Zipp the benefit of the doubt that their dimples do actually test faster than the same rim shape without them, but that's not to say that somebody else couldn't come up with a different shape which is faster still and doesn't need a rough surface to work.

Lew has his vortex lip which he has introduced to Reynolds wheels, from possibly unreliable memory.

See USE Nano Surface Finish wheels

Re: Klein

Why do people insist on putting Garmins on their stem? Out-front mounts exist, people!

Stem mounts are free with Garmins and easily interchangeable. Out front mounts expensive, only for oversize bars afaik, and harder to put on loads of bikes.

You can always use a shim to make them fit narrower bars.

The amount of extra bits I'd need to fit mine to my bars, it'd end up costing more than I spent on the Garmin. Stem mount it is then.

Stem mounts are free with Garmins and easily interchangeable. Out front mounts expensive, only for oversize bars afaik, and harder to put on loads of bikes.

Sorry this is the porn thread; no expense spared.

p.s. aren't barfly mounts about £20?

The amount of extra bits I'd need to fit mine to my bars, it'd end up costing more than I spent on the Garmin. Stem mount it is then.

SRAM Quickview, <£12. The adapter for 205/305/605/705 is under £4. How little did you pay for your Garmin?