For my part, I've found that I do best when I take full advantage of what Mother Nature offers, bu tucking and coasting on descents, and saving energy for climbs. On roller coaster hills, I'll often begin the extra effort phase as I near the bottom of the hill, to hit the climb at maximum possible speed, then try to maintain momentum through the climb as far as possible.
BTW- when I spoke of hitting the bottoms of hills at max speed, I was referring to roller coaster terrain, where there was a down then up situation. But I know from experience that many cyclists let hills psych them out, and slow down considerably when they see a climb ahead. If time is important, this is highly counterproductive, but can be a hard habit to break.
You may not keep the gig long if the hammering fast to get there fatigues you so much
they notice your job performance suffers .
they are not paying you for your athletic prowess getting there ..
doing that on the way home is your own Business ..
so I say early to rise , leave yourself flat tire time on the way in..
Race-Train on the long way home.
We're all different, with some having good short time power, and others having better mid time power. I have two routes for a climb on my way home daily. One involves a wall, the other a long grade. The distances are the same, but I find that charging the wall consistently knocks time off the trip, even though I'm slow for a while at the top. The fact is that I don't handle the power+ needed for long grades as well. OTOH, I don't know if I'd get the same results if the steep hill was longer than my sprint range, and I needed to gear down and lose time on it, or for that matter if the grade was longer and shallower.
So it's not only about physics but about physiology too.
For the OP - Another thing to consider is that I think most of us, including you, are probably already, instinctively, pushing a little harder on uphills, and coasting a bit on downhills. So if you then decide you want to speed up even more, should you compound that uphill effort, or are you already getting that benefit, and should you seek extra speed where you've been slacking, namely the downhills?
Okay, I did my own math and I think the consensus is correct, you get more benefit from speeding up your ascents (if you aren't already working harder on that part of your ride).
Here's how it makes sense to me. Let's say I have 5 segments of 15 minutes each, with constant effort:
I cruise on the flats at 20 kph for 5 km,
I go down a gentle slope at 28kph for 7 km,
I go up a gentle slope at 12 kph for 3 km and then
I ride level but into a headwind at 16 kph for 4 km.
Each segment takes 15 minutes.
I decide I want to shave 3 minutes off my total by doing one of the segments in 12 minutes. It doesn't matter which segment it is, to complete it in 12 minutes, I have to go 25% faster for those 12 minutes.
The uphill section is the one that will take the least effort to increase my speed by 25%, because it has the least increase in air resistance.
Anyone can ride fast on the flats and downhill, but climbing is a whole nother ball game. Some dude on a SSFG passed me before I even had a chance to warm up on the ride home tonight. I paced him for 5 minutes, not drafting, waiting to make a move. When I came to a slight uphill section, I passed and easily dropped him. Point is, if you want to go faster, work on climbing.
But there's another consideration, too: it's fun to go fast. So you should maximize your effort on downhills to go faster, because then you get the reward sensation of going fast, which motivates you to ... go faster. There's more to life than maximizing efficiency.
I've just recently moved and so have started commuting again. It's a whopping 5.5 miles door to door. I'm out of shape, and new roads etc. However, I managed to knock 10 minutes off my commute this morning compared to the previous two, just by waiting! The wind was 5mph this morning instead of 20mph... I managed it in 25 minutes, which includes a very sedate ride along a MUP by the creek.
- Are you at the optimum weight for your body's height and bone structure?
- Do you get enough sleep?
- Have you eliminated non-nutritive calories and strange dietary chemicals, substituting healthy foods?
- Tried a season of interval training on the bike and resistance/core training when not on the bike?
You will go faster.
Even better, you can hit, say, 54 mph if you tuck yourself into a more aero position - and you can't tuck into a real aero position when you're hammering as hard as you can.
So if you really want to go fast on a real downhill, coast and tuck yourself into a really aero position:
Faster commute, don't ride a cargo bike.
And how do you know you're going faster when you pedal down a 10% grade compared to when you get into an aero tuck? Do you actually measure your speed?
Anything over 10% or so, you WILL go faster even in a half-ass aero tuck than hammering away.
Because a 150-lb rider descending a 10% grade is getting about 1500W of power from gravity. And the more aero you get, the faster you go. And the faster you go, the more power you get from gravity.
Why do you think pro racers get into those aero tucks to descend? Do you really think you're stronger than they are? Just like almost all of us here, you're heavier and weaker. Pro riders have less to gain from a tuck because they're lighter, and more to gain from pedaling because they're stronger. Yet pros tuck and coast.
You can say you're faster pedaling downhill all you want. Go ahead.
But if your goal really is to go fast, learn something.
Fine. I am vaguely aware of the amounts of energy consumed by wind resistance vs. hills and other sources of resistance. Just trying to add another point of view - all work and no play make Jack a dull boy. And, in my particular case, my panniers full of work clothes and lunch tend to reduce my aerodynamic efficiency as much as I gain from an aero tuck. And yes, I do have drop bars and know how to use them. Cheers!
Already mentioned was to go faster on the uphill to get more bang for the buck (less wind resistance).
The second reason to go harder on the climb is a more constant speed:
20 miles at 20 mph takes one hour.
If you ride 10 miles uphill at 10 mph + 10 miles downhill at 30 mph (same speed delta), it will take 1:20.