Agreed, you tend not be caught out by such conditions that would make me want to block my vents. Personally if it’s really cold I’d rather have something covering my ears than just something blocking the air flow onto my head.

Not really – the maths actually says that it’s exactly double (though that’s at the outer edge of the tyre, it’s reduces proportionally towards the axle centre.

Only for acceleration, not for climbing (which is when most people worry about weight). Proper scientific analysis shows that you expend a tiny amount of energy on acceleration, even in a group changing pace a lot – not that the peleton yesterday was doing much changing of pace with “motorbike” Wiggins sitting on the front! Far, far more energy to be saved by aero wheels than you lose by having to accelerate them.

Actually I realised the numbers are easy – to accelerate a 100g rim from stationary to 30mph costs 18J (KE = 1/2mv^2 – times 2 to account for the linear and rotational KE). So even if you’re making a standing start acceleration like that once a minute, the wheel only has to save 0.3W in aero drag to be worth it!

if the slidey helmet protector thing weighed less than either of those you’d get one instead?

Only if I didn’t already own those, didn’t mind my ears being cold and didn’t have to still carry the weight of the slidy vents around with me when it wasn’t cold 🙄

That’s because bikes are under the weight limit anyway, so they may as well introduce other benefits. We didn’t see any aero components used until the weight limit came in, and it would be interesting to see if their proliferation would remain if it was dropped.

I think we have only just seen the start of proper analysis being done for performance gains and trade offs rather than just using common beliefs.

For example with components/frame design it was all about lighter is better. But know is recognised that aero can be more important than a few 100 grams.

so, a clip on slidey vent for the winter months;

problem solved 😉

As someone pointed out above it’s the “aggregation of marginal gains”. Team sky were using closed helmets in the tour on some days too.

Cav can win or lose by the tiniest of margins so every advantage helps. The guys were all wearing skinsuits as well I think. In the sprint aero would matter and if you arrive a little bit fresher because of your kit then even better.

I can see the advantage of a closed helmet for winter riding or wet weather riding because it would keep you head warmer and dry. No where to clip my light to though.

Going slightly OT (well maybe) with all this talk of marginal gains, aerodynamics etc. I noticed that both Cav and G had not shaved yesterday. Were they conforming to the road cycling old wives tale that you shouldn’t shave on your biggest days as it saps strength? I remember Lemond actually stating that he had done so for one of the TTs in the Tour, I think 1990.

aracer – interesting to do the maths though I’m not sure proper aero wheels are only 100g heavier than lighter ones but the point stands. Plus, aero gains are always going to vary significantly depending on the situation – speed, climbing, shelter from the pack, etc

@ speaker2animals – almost certainly, and I suspect that they only ate the middle bits out of their bread rolls as well

Don’t underestimate the power of psychology.

you shouldn’t shave on your biggest days as it saps strength?

Or more practically for me and many others I know, it avoids shaving rash which can be a pain, literally, when you then sweat lots and/or have a helmet strap rubbing it. Just another distraction that you don’t really need.

not sure if anyone else has said this, but I wouldn’t want a bike helmet with slidey pointy vents in things in that are going to stab me in the head if I crash.
I believe cycle helmets are supposed to crack and fragment on impact whereas ski helmets have a hard shell which keeps the form of the helmet after impact.

..this is a part of the reason why we don’t use motorcycle helmets on a bike. Helmet design is a compromise but any weight that does not add to the protection is unhelpful.

TJ – you don’t, I don’t but plenty other mountain bikers do wear moto helmets (and have done for years). Leatt style neck braces have recently become commonplace in DH to help protect against rotational injuries.

Leatt style neck braces have recently become commonplace in DH to help protect against rotational injuries.

The cynic in me would also say the provide a nice set of flat pannels to stick sponsors logos over what arent flapping arround in the breeze and therefore being easy to photograph.

that’s not cynicism
that’s actively pursuing cynicism, which there must be another word for

you’re right Brakes it’s not being a cynic, it’s being a fanny.

Leatts cover a fairly large area of the riders jersey, which funnily enough usually has sponsors logo’s on 🙄