Is all elevation equal?

CleeRider

Just a quick maths question that I can't get my head around...
If I have to climb 1000ft would I get to the top quicker on a constant 10% gradient (hard work but short distance) or a constant 1% gradient (easy but long distance)? Is there an ideal gradient for getting to the top quickest?

Lycra-Byka

Just a quick answer with no maths; I'd rather ride the 1%.

I know that on a rolling ride with the same elavation total as a steeper gradient ride, I feel less tired after it.

As for the maths........pfffff!

amaferanga

So you're wondering if you'd cycle ~3km up a fairly steep hill quicker than you'd cycle ~30km up a very gentle incline. The latter should take around an hour. If it takes you about an hour to cycle 3km up a fairly steep hill then you should probably find a new hobby....

supermurph09

I think the answer is somewhere in here........... http://www.flacyclist.com/content/perf/ ... outes.html

GiantMike

CleeRider wrote:

Just a quick maths question that I can't get my head around...
If I have to climb 1000ft would I get to the top quicker on a constant 10% gradient (hard work but short distance) or a constant 1% gradient (easy but long distance)? Is there an ideal gradient for getting to the top quickest?

10%, as long as you have the gearing to ride it efficiently.

YIMan

10%. The 1% is faster therefore more wind resistance and longer therefore prolonged impact of friction.

jameses

I think you need to keep the total distance travelled the same for your question to make sense - so 10km at 1% or 1km at 10% followed by a flat 9km.

My guess would be 10km at 1% would be faster since there isn't a huge amount of difference between flat and 1%, whereas that first km at 10% in the second option would be considerably slower.

MichaelW

For descending, it it much more efficient to descend a long shallow slope than to burn off momentum by braking on a steep one.
For climbing, you need to find a hill with a steep and shallow side and do some time trials.

rolf_f

JamesEs wrote:

I think you need to keep the total distance travelled the same for your question to make sense - so 10km at 1% or 1km at 10% followed by a flat 9km.

Not really. It is often the case that you have the choice of a short steep climb or a longer, flatter climb. The question isn't about overall distance but the quickest way to climb.

But note; in your scenario - at 10km an hour, the 10% climb would only take 6 minutes to cover leaving you 9km of dead flat to catch up. The rider on the 1% would be left for dead. What hammers your average speed in hilly country is not how much you climb but how long you spend climbing.

Initialised

I rode this route today (not my data, I was slower): http://connect.garmin.com/player/251354516

The 7 mile climb at 13 miles was a lot easier (7 miles in 40mins) than the 3 mile climb at 33 miles (3 miles in 30 mins) the total elevation gain was around 1000ft for both.

Go find some hills, ride them and provide similar anecdotal 'evidence' don't over think it, just ride.

rolf_f

Initialised wrote:

I rode this route today (not my data, I was slower): http://connect.garmin.com/player/251354516

The 7 mile climb at 13 miles was a lot easier (7 miles in 40mins) than the 3 mile climb at 33 miles (3 miles in 30 mins) the total elevation gain was around 1000ft for both.

Go find some hills, ride them and provide similar anecdotal 'evidence' don't over think it, just ride.

The person who posted the Garmin data rode the 7 miles in 26 minutes and the 2.7 miles in 10 minutes. So actually, the gradient didn't affect his pace that much. Mind you, looking at it, the whole speed record looks odd to me - there seems little relationship between the terrain and the speed. Maybe he was on a moped!

term1te

Looking at VAM or vertical ascent in meters per hour (or the Italian version there of) your VAM increases with gradient until you can't comfortably pedal any more. To gain 1000 foot in the sortest time, I'd take a 10% hill over a 1% any day. Looking at the data from a hilly ride in Strava, the largest VAMs are always associated with the steepest hills.

neeb

This^^^

Look at it this way - whatever the vertical ascent, you have to climb it, and that takes a certain amount of energy. Let's assume you are putting out a constant 250W. The steeper the gradient, the more of your energy is going directly into overcoming gravity rather than being shared between that and travelling a horizontal distance as well.

housemunkey

Steep as others have said, up to the point that you can't pedal efficiently. You have the same gravitational potential energy to gain either way, but the flatter it is the faster you are going which introduces extra losses due to friction and wind resistance.

term1te

One way to think of it would be to give that nice Herr Martin a race over 1000 vertical meters. I'll take the 10%, so I've got to ride 10km at 10%, not disimilar to the Alpe d'Huez. I've done that in around an hour. To beat me on a 1% incline the world time trial champion has to travel 100km in less than an hour. I'll back myself to win that one.

It would be interesting though to find the shallowest gradient at which he would beat me. Sounds like a question from an A level physics paper.

neeb

But I guess that if there was no air resistance and no friction whatsoever, you might make the ascent in the same time whether it was 10% or 1%... On the shallower gradient you could simply accelerate up to whatever speed was necessary (100km +?) such that all of your energy was being used to overcome gravity...

housemunkey

If you were purely acting against the component weight down a plane of you and your bike then it'd take the same time yes.

al_kidder

OK, the consensus is that gaining elevation is faster on a steep slope.
But how about going downhill. Is it quicker to take a steep downhill road, then ride flat, or take a long gentle decline to get home from the hill you went up earlier?

hatch87

Al Kidder wrote:

OK, the consensus is that gaining elevation is faster on a steep slope.
But how about going downhill. Is it quicker to take a steep downhill road, then ride flat, or take a long gentle decline to get home from the hill you went up earlier?

I'm voting steep hill flat. Aero takes over so the difference between speed on flat and slight down hill won't be much, and why wouldn't you go down a steep hil :?