As I'm riding 17km each way to work now, I thought it'd be interesting (just like The Smiths song) to see what difference it does make which bike I take. I've already covered the difference weight makes and concluded that, while a lighter bike is faster, the vast majority of resistance is wind resistance. I compared two different bikes, a traditional English 3 speed town bike and a light touring bike. So in one corner we have:
Weight: 20kg+ in riding trim
Riding position: Raleigh bars about 1" above saddle
Tyres: 37mm Schwalbe Delta Cruiser @ 55psi
Drivetrain: Sturmey Archer 3 Speed hub gear
Riding position: Drop bars set 1" below saddle
Tyres: 28mm Panaracer Pasela @ 80psi
Drivetrain: 2 x 7 Derailleur
This is the route below, it starts at Bow Road tube station, heads west along Cycles Superhighway 2 through central London, over the Southwark bridge then continues along Cycle Superhighway 7 and finishes at Earlsfield rail. The distance is about 17.6km, with an overall climb of 130m which makes it essentially flat. The route involves a lot of traffic lights, as well as a lot of traffic including but not limited to, chock-a-block London buses, crazy taxis, irate BMW 4WD's and large trucks. I averaged 5 trips each and averaged them, effort was reasonably consistent at a 7/10 effort most of the time. I define 10/10 as all out, so 7/10 is more like a tempo effort which you could sustain for a few hours.
View Bow Rd to Earlsfield in a larger map
First up we have the times for the Raleigh, note that the times are in decimal format. Also the 52m time was correct, I think I had a strong tailwind and I put in a slightly harder effort as well. The 67m time was into a headwind and I didn't feel well that day so I took it easy.
62.43, 67.08, 60.62, 52.01, 56.75
Average time 59.78 - 59m47s
Now we have the times for the Randonneur, I'll admit that I did hammer it down some of the straight flat parts where there were long stretches between traffic lights.
57.53, 60.33, 53.50, 54.93, 56.75
Average time 56.6 - 56m36s
So you can see the difference is 3m11s, which is a difference of 5.6%. This certainly is noticeable, while not huge it seems to feel about right after fiddling with the bike calculator previously. I would attribute it mostly to the lower more aerodynamic position of the Randonneur as well as the higher pressure faster rolling tyres and less so the lower weight.
I think though that this really shows how versatile the Randonneur style of bike is, I define the Randonneur as basically a road bike mixed with a touring bike, a sort of jack of all trades. It has most of the speed of a road racing bike, but with most of the practicality of a touring bike, it won't substitute either one but blends the best characteristics of both which is really well suited to commuting and recreational riding. Comparatively, the Raleigh is slower, but lower maintenance, easier to ride in any clothes, better braked and more suited to adverse weather due to everything being sealed. What the French call the randonneur style of bike is really synonymous with what people in the UK call a "winter/audax" bike, or the traditional English club bike, they are all basically practical bikes suitable for day rides or light touring but equally suited to general riding, they are fast and practical.
This is really one of my favourite styles of bike, mostly because it's so versatile. Walking into a typical bike shop here is much like in Australia; bikes are divided mostly into Road or MTB, occasionally you get Town/City bike but generally the former is the dominant divider. To me this seems ridiculous because both Road and MTB are recreational sport bikes mostly made for racing or recreational riding. While generally in London there are a lot of cyclists on all sorts of bikes, and now most shops will have good city bikes with full mudguards, hub gears and sensible riding positions, it's almost impossible to find a Randonneur style bike or even a full touring bike. The funny thing is that 30-40 years ago, most road bikes had mudguard/rack eyelets and clearance for sensible size tyres, they have slowly "evolved" into much more niche sporting equipment that you will struggle to fit with any practical components.
I'd personally love to see a revival of this type of bike, most people don't race and most MTB's never see the dirt. A town bike is great around town, but insufficient for a hilly weekend ride, the Randonneur can do both pretty well, ride to the country on Sunday, ride to work on Monday. It really is about as close as you can get to a do-it-all type of bike, which is why I have built mine the way I have. There are lots of minor variations like hub gears, different styles of racks, geometry etc, but the basic idea is the same - a bike you can go for a adventure on but still ride to work the next day.