Power required to do 32kph (20mph)
Power required to do 40kph (25mph)
I’m only interested in road bike data.
Please include as much detail as possible. It needs to be a flat road, no wind if possible. Definitely not tailwind numbers. Include detail on quality of road surface. I’m also very interested in the the w/kg you need to hold these velocities. Rider weight, height and build would also be great. Bike and clothing too.
I’ll start.
32kph (20mph) - 190w - 3w/kg Hands on hoods - Zero attempt to be aero
40kph (25mph) - 297w - 4.7w/kg Hands on hoods - Semi puppy paws position
Smooth tarmac
Older aero road bike
Aero road helmet
Tightish race fit jersey and shorts
Rider
63kg
170cm
Mid athletic build
Broad shoulders for height
Just a note, the speed needs to be very close, particularly at 40kph(25mph). Just 1kph slower will generally be 20w lower. I’m interested in a casual riding position for the slower speed. Just your comfortable all day position.
Hit me with your data
If you don’t have it, it’s worth testing it. It’s a fun project to add into your next ride.
I assume you are trying to measure your CdA and Crr? This question is very hard to answer. Not sure it’s possible in a meaningful way.
Best comparable route I have is a military route which is open for the public and quite nice to work out on (flat for some KMs, not many people on it).
After around 120s of acceleration after full stop (when inertia is up), I got an avg. of 31.4km/h for 4km with NP of 147W and 158W (31.6km/h, other direction). Not sure the route is 100% flat.
Bike is an endurance bike with 30mm tires, but I have short arms, so I usually sit quite aero (stretched out) on the bike.
In my experience speed depends a lot on inertia. During endurance rides I often get 30+km/h with not much watts, but it takes time (or rolling down a bit) to reach the speed. Every small bump in the road / short stop etc. reduces it. I am saying this because it’s hard to measure/feel when you reach the point where acceleration has stopped and you are only working against resistance.
This was by yourself and not in a group? Was this on a TT bike? Not saying this isn’t possible but it seems highly unusual. Then again I’ve never lived somewhere flat. The numbers you posted are consistent with TT bike numbers.
That looks low to me also…but I’m also nearly 20kg heavier. They dont look…super duper low to me. I’m just going off of memory and not hard data, but I’m pretty sure I’m around 210 watts at 20mph on the hoods. 6’, 185lbs, flat ground, cross bike with 55mm deep wheels.
Yea that makes sense. Tad bigger…but bike probably a shade faster on the road.
I’m honestly only really confident about my numbers because when I’m in shape…I shoot for zone 2 rides around that wattage and generally cruise around 20mph when it’s flat and calm. I think my 25mph numbers are substantially higher than any shown so far…but I’d just be guessing.
By tad bigger I mean 1” taller and 20lbs heavier. And I do a lot of endurance rides on pancake flat ground. In the summer when it’s warmer, on the rare no wind day it’s something like 19.5mph at 200W.
Obviously this depends a TON on terrain, road surface, and conditions- even without hills, good road surface make a huge difference over slower road surafaces, and in flat coastal areas, wind can really slow you down if it’s swirling or a headwind vs a crosswind. With those caveats, I do a fair amount of riding inland on the Jersey Shore each summer where it’s pan flat with generally decent surfaces, sometimes windy but rarely block headwinds. Here’s some rough numbers for road and TT bike:
Rider info: 5’9", 160, FTP low 300s (I don’t measure FTP and train off effort vs power, so those are rough estimates)
Road (at the time venge disc with a good position, tight kit, CLX 50 wheels and s-works turbo tires)
20mph: 200W
25mph: 290W
TT (I have a very dialed aero position, but this is just with regular road helmet and 404s, estimate 20W less in TT helmet, skinsuit, disc/deep front):
20mph: 175W
25mph: 250W (though haven’t ridden up there since dialing my aero position a bit more. I did 27mph in a 40k TT in full race kit at 286W last year, that included some wind and decent but not pristine road surfaces)
On my TT bike it takes about 225w to do a sub four hour century. I’ve gone 27mph for 100 miles with around 270w on my TT bike.
I live in south Florida. It’s flat albeit it’s still not easy holding this power without stopping and maintaining a proper position. I encourage anyone to try it and if you’re in the area let me know, I’ll pull you around for 4 hours.
Sounds like your position is great. The flattest century here has over 3k of elevation gain and numerous starts and stops. A century along more popular routes with some climbs is likely to have 7000-10000ft of gain lol, so 25mph is not gonna happen.
I wish I had some decent climbs in our area. Central and north Florida are hilly and I really enjoy riding in that area. The route I mainly do for these type of rides is flat and has no stops and when the wind is low it’s a nice.
