At what gradient does cycling stop being efficient?

rick_chasey

As the title suggets.

We know cycling is the most efficient way for a human to travel.

For a given effort you go further that say, walking or swimming.

However, that surely must change when you start gaining height rather than just distance.

At what gradient is it more efficient to walk up (or indeed, use another type of equipment way of moving?)

Edit: when I mean walk up, I guess I mean WITHOUT a bicycle...

Smokin Joe

It's always quicker to cycle up a hill than walk, unless it is so steep you can't keep moving.

rick_chasey

Smokin Joe wrote:

It's always quicker to cycle up a hill than walk, unless it is so steep you can't keep moving.

But is it more efficient? Could you, say, run for the same effort that it takes you to cycle, and get to the top quicker?

simonaspinall

Even if you were going up a one in 3 or one in 2 I think you'd be going faster!

Depends on what your muscular functionality/coordination is used to - If you're used to pedalling then it's easier - I was out of breath walking up a hill the other day, but if i was on the bike i would've been up it in a jiminey with a monkey on my back!

Buckled_Rims

I suppose they'll come a time when the calories required to travel a set distance on a bike will be more then walking that same distance on the gradient.

It'll come down to your weight, bike ratios and steepness of gradient (ignoring other small factors such as tyre friction, crank length, aerodynamics etc).

Radioactiveman

Hmm

Did a short MTB ride (6.5 miles) sunday took an hour and ten minutes. Did the same route the next day running instead and it took an hour. However I have no idea how much energy I expended on each attempt so no way of working out efficiency

father_jack

legs don't have gears so biking will be more efficient.

finchy

Rick Chasey wrote:

Smokin Joe wrote:

It's always quicker to cycle up a hill than walk, unless it is so steep you can't keep moving.

But is it more efficient? Could you, say, run for the same effort that it takes you to cycle, and get to the top quicker?

No, you couldn't run up a hill more quickly and with the same effort. I run up hills fairly regularly for fitness, and believe me, running up anything steeper than say 8 or 9% at a high pace is absolutely exhausting.

Go and try it out. Find a steep hill which goes up no more than about 50m vertical gain and see if you can do it more than 3 times, fast. It hurts!

nwallace

When climbing a hill, cycling becomes less efficient than walking when some bastard has decided it's steep enough to be closed to traffic and made steps.

DaSy

My wife ran up Ventoux the day after I rode it a few years ago, and she maintained around 6.5mph, and overtook a fair few cyclists.

When we went back earlier this year, and booked in at the same accommodation, after describing who I was and that I had stayed with them before, they didn't remember me until I mentioned my wife came with me last time and she ran up and back on the Ventoux...they immediately remembered me, well, her!

father_jack

put 20kg on a backpack then walk up a 400' hill. Then put 20kg on bike pannier and go up the same hill in 1st gear. Even with the extra weight of the bike, it'll still be easier on the bike.

SteveR_100Milers

Try cycling up a vertical cliff.....

Interesting thread, which no one has answered yet - what gradient dos it become more efficient to use your legs. Well I know i can walk to the top of pen y fan, but no way could I ride the same route, so there has to be a crossover of efficiency somewhere.

finchy

SteveR_100Milers wrote:

Try cycling up a vertical cliff.....

Interesting thread, which no one has answered yet - what gradient dos it become more efficient to use your legs. Well I know i can walk to the top of pen y fan, but no way could I ride the same route, so there has to be a crossover of efficiency somewhere.

I think that Rick was talking about climbs which are doable by both bike and walking. I would suggest that it really depends on the rider. You and I might struggle to get up a certain gradient on a bike but Cadel Evans wouldn't.

eh

Well I know i can walk to the top of pen y fan, but no way could I ride the same route

If it was tramac to the top and you had low gears it wouldn't be that bad. I don't remember the storey arms tourist route being all that steep at all. Fit riders on mtbs can get up insanse slopes and normally the limiting factor is traction and front wheel hitting rocks, roots etc.

cougie

Blimey Dasy - averaging 6.5mph up Ventoux running is pretty damn good. Whats her 10k time ?

deptfordmarmoset

I get confused by what ''efficiency'' means. When you go up a hill aren't you in some way storing up potential energy in terms of altitude gained, a bit like a stretched rubber band that ''wants'' to return to its untensed state? Because whenever I turn round and ride back down my bike seems super-efficient.

The brakes less so...

pneumatic

Surely there comes a time when your gear inches (distance covered by the tyre per revolution of the pedal) are equal to or less than the distance travelled by your foot as it goes over the chainset. If you had a 175mm crank, that would be the gear combination that only delivers only 350mm of forward motion on the bike.

At that point, you have to consider what takes more effort, turning the crank, or just placing your foot in front of you and shifting your weight forward. Without the bike, you are n kilos lighter, too.

As has been noted, though, how much energy you use will also depend what your body has been trained to do.

I know that, if there was a cycle path adjacent to the stairs in my house, it would be easier for me to climb the stairs than to cycle up the path.

Excellent question, btw! It has woken me up this morning and got the old brain going again!

rick_chasey

johnfinch wrote:

SteveR_100Milers wrote:

Try cycling up a vertical cliff.....

Interesting thread, which no one has answered yet - what gradient dos it become more efficient to use your legs. Well I know i can walk to the top of pen y fan, but no way could I ride the same route, so there has to be a crossover of efficiency somewhere.

I think that Rick was talking about climbs which are doable by both bike and walking. I would suggest that it really depends on the rider. You and I might struggle to get up a certain gradient on a bike but Cadel Evans wouldn't.

It's a more hypotheical question.

term1te

I was thinking along similar lines recently. If you only measured height gain per unit time, what would be the best gradient to cycle up? So if I wanted to gain 100m in the shortest possible time would a 5% hill be quicker than a 10%?

I guess the optimum would be the steepest one you can manage with a sustainable power output?

simonaspinall

I thinnk I know what method I'd have rather used when it came to the inevitable descent!

rick_chasey

pneumatic wrote:

Surely there comes a time when your gear inches (distance covered by the tyre per revolution of the pedal) are equal to or less than the distance travelled by your foot as it goes over the chainset. If you had a 175mm crank, that would be the gear combination that only delivers only 350mm of forward motion on the bike.

At that point, you have to consider what takes more effort, turning the crank, or just placing your foot in front of you and shifting your weight forward. Without the bike, you are n kilos lighter, too.

As has been noted, though, how much energy you use will also depend what your body has been trained to do.

I know that, if there was a cycle path adjacent to the stairs in my house, it would be easier for me to climb the stairs than to cycle up the path.

Excellent question, btw! It has woken me up this morning and got the old brain going again!

Interesting; are we including stairs?

What if you had to walk/climb/crawl up the adjacent cycle path?

Pross

Presumably gravity would have just as much of an impact on running / walking so the relative efficiency remains the same. Wouldn't like to try swimming up a river on a 10% gradient!

SteveR_100Milers

eh wrote:

Well I know i can walk to the top of pen y fan, but no way could I ride the same route

If it was tramac to the top and you had low gears it wouldn't be that bad. I don't remember the storey arms tourist route being all that steep at all. Fit riders on mtbs can get up insanse slopes and normally the limiting factor is traction and front wheel hitting rocks, roots etc.

Blimey, what are you doing wating your time posting on here then!! Note steep, its hard enough to walk briskly up!

serioulsy though I would find it harder to ride up that gradient on any kind of bike than I would by walking, so for me anything around 40 degress + of inclication is easier by foot, and I will assume easier means more efficient (i.e. less effort for given speed, or simply faster walking for the same effort).

Monty Dog

It's going to be somewhere around 40% - any steeper and it's difficult to main smooth power delivery / traction of the back wheel. It's not some much about efficiency but economy - a bike will always be less efficient due to the extra energy required to move the extra mass, whereas economy is about the ability to maintain a consistent power output over a period of time i.e. with the right gearing, you can keep going for longer on the bike and the effort expended / metre travelled is less

rick_chasey

http://en.wikipedia.org/wiki/Bicycle_performance

Cleat Eastwood

Thats just what I was going to say.

pneumatic

Rick Chasey wrote:

http://en.wikipedia.org/wiki/Bicycle_performance

I didn't like the bit at the end about shaving kilogrammes off riders to make them go faster up hills. I knew it was true, but seeing it written down as a scientific formula makes me depressed, so I am off to the fridge for some comfort!!

simonaspinall

Rick Chasey wrote:

http://en.wikipedia.org/wiki/Bicycle_performance

My brain hurts after reading that

spen666

Monty Dog wrote:

It's going to be somewhere around 40% - any steeper and it's difficult to main smooth power delivery / traction of the back wheel. It's not some much about efficiency but economy - a bike will always be less efficient due to the extra energy required to move the extra mass, whereas economy is about the ability to maintain a consistent power output over a period of time i.e. with the right gearing, you can keep going for longer on the bike and the effort expended / metre travelled is less

I am not sure I agree with you fully.

I am not sure that everyone on this thread is talking about the same thing when talking about efficience.

My view of efficiency here is the amount of energy needed to get to the destination.

It is my understanding that riding a bike requires less energy than to walk/ run the same distance owing to resistance etc.

If I am right, then a bike is more efficient as long as you are able to ride it. Ie if the slope is too steep to ride up, then it is not efficient to push bike & walk than it is to just walk.

Therefore I conclude a bike is more efficient until you reach the gradient when you can no longer ride it effectively

blackpoolkev

my guess is that the crossover point comes when you need a gearing ratio where your front cog has less teeth than your rear cog.

pneumatic

blackpoolkev wrote:

my guess is that the crossover point comes when you need a gearing ratio where your front cog has less teeth than your rear cog.

Not sure about that. I went up Alpe d'Huez on 22x32 and, although it took a while ( ), I am sure it was quicker and easier than walking up would have been.