Assume The Position, Boy
Ah, takes me back to those happy days at school. The psychological bullying, physical abuse, and the ever-present threat of being used as a human toast rack for a hot buttered crumpet.
Errr . . . ANYWAY, Joe Friel wrote a recent couple of posts (here, and here) about posture on road bikes. It’s stuff that we should all know, but following advice is often harder than knowing about it. There’s lots to consider when you bring aero bars into the mix, but on your basic road bike, it’s rotating the hips forward, and flattening out your back that counts.
The air resistance you feel on a bike is made of three components:
- Forward pressure resistance as you create your bow-wave. “How low can you go” is the basic way to minimise this.
- Drag resistance as your body creates a low pressure, high turbulence area in the air behind you. Make your back flat rather than curved by rotating your hips forward & arching your back down. Fancy gizmos like aero helmets also help.
- Drag & forward pressure on the bike & it’s add-ons. I read somewhere that a bottle & cage accounts for 2% of the drag on a bike. So on a short race, maybe its worth not having fluids on the bike? Or an aero bottle starts to sound attractive on longer rides. And you wouldn’t believe how much difference deep wheel rims make. You get the idea.
So I’ve been working on my posture over the last couple of weeks, making a conscious effort to flatten my back. Yes it makes a difference - average speeds moving form 17 to 18 mph over 30-40 miles.
But today I was out with a rucksack on. Only a small, close-fitting one, that’s got just enough space for my laptop, notepad, a couple of items of clothing (for the sake of decency, we won’t mention which items here), and my camera. There was also a little space for a couple of extra items, which was convenient, as I stopped by the Quickrelease.tv studios on my way to see today’s client, to pick up the consolation Schwag that Carlton Reid had offered for my video competition entry.
Nice bloke, Carlton. A little shorter than I’d imagined (i.e. ‘normal’ sized rather than the 6′15″ in my head), but that’s just the internet for you. And I’m very happy with the great Schimano Schwag that he gave me.
But how is all this related? Well, there was a light headwind on the way out today, but that turned into a tailwind for the return journey. On Saturday’s ride (no rucksack) in similar conditions, I’d averaged 18.2mph. Today, it was a real struggle to get up to 16mph.
The rucksack I had on was about the closest fitting & most aerodynamic way I can think of to carry the luggage I had. But my average speed was still down by 12%.
The lesson from this? Luggage slows you down - not just from a weight penalty, but drag is also a factor!
- Type: Cycle
- Date: 10/15/2007
- Time: 09:37:33
- Total Time: 1:18:45.00
- Distance: 21 miles
- Average Speed: 16 mph