Cadillac

I mentioned to a friend that on a particular route I was slow climbing the hills.
I said that although I was doing 20 km/hr on the flat, I was riding only 5 to 8 km/hr up the steep hills.
He said, "It doesn't matter how slow you go up a hill because you can always make up for it on the downhill so that it will even-out your speed."
While his "theory" sounds plausible, it seems to me that in practice it doesn't hold up.

Can you comment?

feher

It doesn't hold up because when you descend, your potential energy is
lost due air friction. Air friction force is proportional to the square of your
speed. So the faster you descend, the worse^2!!

oldokie

Measure your time over a given distance that includes up/down and test the theory. I think it would be true for me. I cruise about 11-12 mph on my bike (heavy Hybrid with bags and lots of stuff) and typically drop to 6-7 mph on the up's but often run about 20-24 mph on the down side if I do some peddling.

rm -rf

For example:
2 miles at 20mph = 6 minutes. (2/20 x 60)

But going up a mile takes too long:
Up 1 mile at 10mph = 6 minutes.
Down 1 mile at 40mph = 1.5 minutes.
Total 7.5 minutes.
Going up slower would be worse. And even 100mph downhill wouldn't help.

If you went up at 13.33mph (4.5 minutes) and down at 40mph, you would break even.

ericgu

It's false, because you spend much more time riding slowly than you do riding quickly.

If you go up a half-mile climb at 10 MPH, it takes you 3 minutes. If you go down it at 20 miles per hour, it takes you 90 seconds.

Your overall time is therefore 4.5 minutes for a mile, which gives you an average of....

13.3 MPH.

edmcnierney

I think you need to measure it yourself. After 1,000 miles of riding with my Garmin Edge 305, I can confirm that on hilly rides I average about 5 - 9% faster than on flat ones.

I live near a rail-trail that's very nearly (but not completely) flat. It drops about 200 feet in 11 miles one way, and I always go out and back. It's flat enough that there is no coasting - you pedal all the time.

My other rides are loops in slightly hilly central Massachusetts. I may slow down to 9 - 10 MPH on the uphills in spots, but hit 35 - 37 MPH on the downhills. If I went up a half-mile hill at 10 MPH I would be going a heck of a lot faster than 20 MPH coming down that same hill! All courses are loops ending at the starting point.

On downhills you also have the opportunity to coast and rest a bit, too.

I have ridden about 600 miles of hilly courses and about 400 miles of the flat rail trail. My overall flat course average is 16.4 MPH, and my overall hilly course average is 17.5 MPH. So I'm almost 7% faster on the hilly rides. I suspect that's small enough to be dominated by individual style/performance so I would guess that some folks are faster on the hills and some are faster on the flats.

godspiral

+10
Also, the physics momentum you're supposed to get back going down is absorbed by air resistance, and more importantly, the practicalities of braking.

roadfix

Basically, you spend 2 hours climbing this hill at a snail's pace, but only 5 minutes flying down this same hill. You'll never make up for the lost time spent climbing that hill........time being the major variable in calculating average speed.

edmcnierney

Do you go down hills 24 times faster than you go up them? If not, then your math isn't helpful. We can all invent numbers. I think it would be helpful if other posters with actual personal data (real experience) could post them, too. We're all able to make up numbers to prove our points.

For example, if I can cruise 20 MPH on the flats, slow down to 15 MPH on a 1-mile uphill, then come down that 1-mile downhill at 35 MPH, guess what? I did those two "hilly" miles at an average speed of 21 MPH - about 5% faster than the flats.

I suspect that gentle, rolling hills may produce a different result than huge ups and downs. And your gearing and ability will matter, too. So I'd certainly like to hear real data from other riders - thanks!

thebulls

Not exactly true: The fastest average speed you can attain on a climb and descent is twice your climbing speed. Suppose you ride up a one mile hill at 4 mph, so it takes you fifteen minutes. Now turn around and ride back down at an infinite speed so the descent takes precisely zero seconds. Then you've ridden two miles in fifteen minutes for an average speed of 8 mph. So you've "evened-out" your speed somewhat, but there's a limit to it. That's partly why the TdF guys who are fast in the mountains win the Tour.

Richard Cranium

Hills are one aspect of cycling that proves that "weight" matters. The other aspect of cycling that hills prove is that "power" matters. When climbing speeds fall well below your current "average" speed, the kind of speeds necessary to regain "average" become unobtainable. To see just how critcial it is to maintain pace - do a few more math problems subbing in 6mph for 8mph. Just 2mph difference on a half-mile hill........

6mph for a half-mile - 5minutes requires == 18mph for 4.3 miles to regain 15mph
8mph for a half-mile - 3min 45secs requires == 18mph for 2.4 miles to regain 15mph
12mph for a half mile - 2min 30secs requires == 17mph for 1 mile to regain 15mph

EDM, you're comments are too goofy to refute. But no one rides more efficiently on hills. And the idea that "on a hill" you can manage 15mph while climbing - will "give back" 35mph on the downhill is ridiculous. And even if it did, it would not be for a very long period of time or distance. No one "gets" 35mph payback or a grade that only slows them to 15mph.

15mph for a mile - 4mins == 30mph for an entire mile to regain 20mph, not likely, since at the top of the hill you are starting from 15 mph. More likely you would need 24mph for two miles. Even if you were on perfectly smooth road and riding in a vacuum it would take more power to crank up to 35mph.

roadfix

Those were arbitrary numbers I picked out of thin air just to illustrate a point to show people who're not into numbers and formulas. I hope it made some sense to the OP....

Edit: Although I picked those numbers out of thin air, theoretically say someone on a trike winches himself up a steep climb at 2mph and descents back down at 48mph.......now that is possible...

gpsblake

Another way to look at it.

Downhill 1 miles at 60 mph = 1 minute
Uphill 1 mile at 1mph = 1 hour

Total Miles: 2.0
Total Time: 1 hour and 1 minute.

Average speed: 1.98 mph

orcanova

Ditto that it is a false assumption, for the reason already stated: you spend most of your time climbing and very little descending. In addition, your descending speed is going to be more of a constant. Notice how on a long descent you reach a certain speed and stay there? That's based mostly on your mass, wind resistance, and slope. A given rider on a given bike will usually top out around a particular speed, once the wind resistance balances out with the gravitational pull. However the speed of the climb is what will change your average speed since your descent is more or less constant.

Well, in actuality your climbing becomes more or less a constant too, but you can increase it significantly with a greater effort, whereas a greater effort on the descent yields you hardly anything...

Here's somthing to read...

https://www.sportsci.org/encyc/cyclin...ingupdown.html

knoregs

my average speed is always down on rides with big climbs... for example the ride I've got planned Monday is about a 140 miles with two 'decent' climbs... for those of you familiar with Vermont they are rt 108 south from Jeffersonville to Stowe going over Smugglers Notch and rt 17 west from Waitsfield to rt 116 in Starksboro going over Appalachian Gap... the Smuggs climb gains almost 1800' and App Gap gains probably 1600'...

my average speed will be about 1-1.5 mph slower than 'normal'... normal being a ride with plenty of climbing but in the form of rollers... the descents will not even out the two climbs!

Cadillac

Since I originally posted this question, let me add another ingredient.
First of all (as demonstrated by several posters), mathematically the overall speed is not "evened out"
However, if I am riding at 20 km/hr along the flat, just before the rising hill, my speed does not decrease until I am into the hill.
However, once I am at the crest of the hill, my speed is back to 20
Then I pedal like a mad-man so that my speed increases to 50.
But when I reach the bottom along the flat, my speed for some distance is well above 20.
Does the increased speed at the bottom help to "even out" my average speed?

In practice, on a hilly route of 42 km, my overall average is 20 and yet along the flat I am doing 20.
Yet going up the hill I am doing only 10.

How is this possible?

Richard Cranium

Probably the easiest way to understand why hills alter cycling efficiency is this:

All the energy you "store" by climbing a hill and overcoming gravity is "released" when you go down a hill to the same altitude at which you started climbing.

However, while you were climbing you also had to produce energy to move through "air". The only way a hill could begin to give back the same amount of energy downhill as when you climb would be by "giving" you a tailwind above the speed at which you descend. If you slow down 10mph on the hill, then you need at least a 10mph tailwind ABOVE YOUR CURRENT SPEED going downhill just to break even!

The "big deal", is that the ability to climb at just 1 or 2 mph difference returns an incredible amount of distance or speed on the downhill. Anyone who has ridden a hilly route with good riders, knows just how this works out - when amplified over 100 mile ride. Those guys are already gone and at home showering while you're 15 miles from the finish.

orcanova

Pedalling like a madman burns up a lot of energy for a little return. Over the summit of a climb, yes, briefly ratcheting it up thelps get to descent speed a little mor quickly, thus gaining a few seconds...that is all. After that, let gravity take over and work on your form descending for greatest efficiency. IF you are in the middle of a descent and have leveled out to, say 40 MPH, and you hit the cranks hard to get to 43-45 MPH and stop pedalling, you will level back out to your previous 40...assuming the gradient is reasonably consistent.

The reason being that mass and wind resistance find an equilibrium much as a skydiver would on a free fall. If you are racing and need a few extra seconds for a gap, you might spend that energy. Otherwise those few seconds really don't change your average speed, so you are best saving that energy and recovering on the descents so you can spend it on the next climb.

You will gain more time on a descent by exercizing good form than you would pedalling like a madman...

To illustrate...my lazy form on a descent usually yeilds me about 40 mph, and my efficient form gets me about 45 mph.

roadCruiser76

The riders in the TDF averaged significantly faster speeds on the level stages as compared with the mountainous ones. On the level ones they were often averaging 27-28 mph. On the mountainous ones they were averaging closer to 20 mph - some were even below 20 mph. Also, on the flats the riders for the most part all stayed together, whereas in the mountains huge time gaps opened up and some riders (memorably Tom Boonen) had to drop out.

To answer the question of which is faster, consider an extreme example. Suppose you were riding a 100 mile course where you first rode 50 miles up a mountain and then 50 miles down. Suppose going up it was so steep you could only average 5 mph. It would take you 10 hours to ride this first half. Even if you could somehow (impossibly) do the descent instantaneously, your century time would still be 10 hours - not too good. In all likelihood you'd be able to do a flat century much faster than the 10 mph average you would have attained on this mountainous course. Basically, just mentally picture a course with a hill so steep and long that you could barely move up it - there is no way that descending that same hill again could possibly regain all of the time lost on the ascent.

reneuend

I think the absolute true test is to ride on hilly terrain and compare the distance and avg. speed to riding on flat terrain. There are a lot more factors involved then simply the speed uphill vs. the speed downhill.

I live in a hilly area and average around 16 mph on a 20 mile course.

I recently went to work at a client in Indianapolis, which couldn't be flatter. So, now I ride there during the week. My average went up to 22 mph over a 20 mile course. This includes stops of which there are a lot more of around Indy then back home. I probably would get a more accurate comparison if I removed the stops from the readings.

edmcnierney

The problem is that that doesn't answer the question. It just throws together a set of extreme, hypothetical numbers that have no relevance to the real world. As we've seen earlier in this thread, one can also invent numbers that "prove" the opposite.

Too many people sitting around in front of the computer typing instead of getting out there, riding, and reporting some real data

edmcnierney

Yes, but that's irrelevant to this discussion because the mountain stages in the TdF are uphill. They don't get to go DOWN L'Alpe d'Huez, do they?

All of the five mountain stages in this year's TdF ended at a higher elevation than they started. In total they ended over four kilometers higher than they started! Only two of them even come close to being level:

Stage 10 - start 79m, end 202m
Stage 11 - start 325m, end 1830m
Stage 15 - start 785m, end 1850m
Stage 16 - start 716m, end 1705m
Stage 17 - start 484m, end 975m

Measured by the winning rider's speed, the two fastest stages in the 2006 TdF (outside of the ITT and prologue) were the decidedly NON-flat stage 12 and stage 18; the two "out-of-the-mountains" stages that dropped about 500m and 800m respectively from start to finish.

The slowest speed for a winning rider? The rather flat stage 2!

Marcello

Here's my real data. I just finished the Seattle Randonneurs 1000k brevet, which went over three mountain passes. The first day we went over Stevens Pass, and I did the last 8 km of climb in exacly one hour at 8 km/hr. On the first few km of descent I was doing close to 60 km/hr, which means about 8 minutes to do the first 8 km of descent. Total time for 16 km: 68 minutes, 14.1 km/hr average. On a flat stretch of road, I would usually average twice that speed, about 28 km/hr.

gpsblake

I'm not a big MPH junkie but on smaller hills, I tend to do my greatest MPH. Maybe it's because I keep up my normal pedal rate when climbing up a small hill while I can still go fast down a small hill.

But on steep hills, my MPH drops like a stone in water.

munkyv22

Flat land I ride about 21Mph. Climbing most hills I ride about 12-14 Mph, Descending I ride between 30 and 50 Mph, depending on the hill.

What does that all average out to? I dunno. I just thought I would share.