# Gradient percentages



## compo (19 May 2012)

I have never really got my head around hills expressed as percentages like 10% etc. such as we see on the Giro and other mountain stages of races. I am used to 1 in 10 and the like. Anyway is a 10% climb a climb of 10 feet every 100 feet (or metres if you are foreign) and multiples of it, or have I totally misunderstood it. Keep it simple please, my education stopped at 12 years old. Seriously. I said climb, but I assume it is the same measurement for descents as well.


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## musa (19 May 2012)

If I'm not mistaken, I believe its do with the level of steepness

Correct me if wrong please


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## jdtate101 (19 May 2012)

Good Old wikipedia to the rescue:

http://en.wikipedia.org/wiki/Grade_(slope)


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## compo (19 May 2012)

Quote from Wikipeda:
as a _percentage_, the formula for which is




which could also be expressed as the tangent of the angle of inclination times 100.


Yes!!


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## oldfatfool (19 May 2012)

10% is 1 in 10,
25% is 1 in 4,
50% is 1 in 2,
100% is 1 in 1

So it is quite possible to have a gradient over 100%, though I wouldn't suggest it on a bike it is one scary drop: 106% on a funicular




http://www.myswitzerland.com/en/tra...le-railways/lake-gelmer-vertical-thrills.html


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## musa (19 May 2012)

compo said:


> Quote from Wikipeda:
> as a _percentage_, the formula for which is
> 
> 
> ...


 
run is the length of road per say
rise is the height on the hill if you want to call it that so (rise/run)*100


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## musa (19 May 2012)

d = run​Δh = rise​l = slope length​α = angle of inclination​


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## MontyVeda (19 May 2012)

musa said:


> If I'm not mistaken, I believe its do with the level of steepness
> 
> Correct me if wrong please


 
I thought it was to do with how slopey a hill is?


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## musa (19 May 2012)

MontyVeda said:


> I thought it was to do with how slopey a hill is?


 
yeah, exactly what I've written


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## compo (19 May 2012)

Mars Bar to Oldfatfool with my thanks.

His explanation made sense. No doubt all the others did as well even if I couldn't make head nor tail of much of it!


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## Gary E (19 May 2012)

Basically there are 3 gradients:

_ Hard_
_ 'kin' hard_
_ and get off and walk!_

Hope this clears things up for you


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## MontyVeda (19 May 2012)

compo said:


> Mars Bar to Oldfatfool with my thanks.
> 
> His explanation made sense.
> ...


 
what doesn't make sense is why 1:10 (or 10%) is such hard work


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## oldfatfool (19 May 2012)

MontyVeda said:


> what doesn't make sense is why 1:10 (or 10%) is such hard work


 
I know a meagre angle of incline of 9 deg (10%), looks sack all on a Protractor


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## youngoldbloke (19 May 2012)

MontyVeda said:


> what doesn't make sense is why 1:10 (or 10%) is such hard work


Depends which way you're going. Isn't it something to do with gravity? 
Re the OP - I was brought up on the '1 in 10' system. Nowadays I divide 100 by the % number on the signto give me a rough idea - for example 12% = 100/12 = 8 (and a 1/2) = 1 in 8, more or less. 8% would be 1 in 12 (and a 1/2), 7% = 1 in 14 (and a bit), and so on.


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## ColinJ (19 May 2012)

oldfatfool said:


> 106% on a funicular
> 
> 
> 
> ...


Er, how many Swiss Francs does it cost _not_ to be sent down on that thing!


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## byegad (20 May 2012)

10% is not that steep but ride it for 4 miles and you'll damn well know you've been climbing. In theUK we rarely get long hills but on the continent they do. The Tour de France riders average silly speeds up hill, but put them up Limber hill outside Glaisdale in the NY Moors which is 33% and they'll struggle. Not anywhere as much as me, but they will struggle!


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## jonathanw (20 May 2012)

http://ccgi.pinniped.plus.com/cols/

a few to check out if you're up this way

I've been up the bealach na Ba twice and the bealach na gaoithe from both sides (which gets to >25% at one point), this week and the bealach rattagan both ways a couple of weeks ago. 

There are plenty of workouts to be had without going to france, just shorter, thankfully


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## Melonfish (20 May 2012)

Gary E said:


> Basically there are 3 gradients:
> 
> _ Hard_
> _ 'kin' hard_
> ...


Hah, beat me to it! 

yeah what he said!


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## albion (20 May 2012)

The % sign is just an abbreviation.

Whilst you get 1 in 10 or 1 in 8 when using percentage the larger number is never shown.
So 10 in 100 becomes 10% and 15 in 100 becomes 10% or 15%.

If you need to get back to a 1 in 10 scenario to perceive then simply place a decimal point before the lst digit.
So 10% =1 in 10
15% = 1.5 in 10
25% = 2.5 in 10


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## smutchin (20 May 2012)

The reason a 10% climb is so hard, even though it doesn't look very steep, is that resistance due to gravity is considerably harder to overcome than wind resistance and rolling resistance, the latter being the main factors that slow you down on flat roads. 

Also, what byegad said - the big climb at the end of yesterday's Giro stage wasn't all that steep, but it went on for over 20km and the likes of Hesjedal were racing up it faster than most of us can go on the flat for that distance. But that's because they're professionals who get paid to train hard. Cav may be a poor climber by those standards, but he could still easily leave any of us mere mortals behind on a climb like that. 

d.


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## Dan B (20 May 2012)

MontyVeda said:


> what doesn't make sense is why 1:10 (or 10%) is such hard work


It's a statistical reminder of a world that doesn't care

View: http://www.youtube.com/watch?v=5tg8aGYXgZM


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## PK99 (20 May 2012)

smutchin said:


> The reason a 10% climb is so hard, even though it doesn't look very steep, is that *resistance due to gravity is considerably harder to overcome than wind resistance and rolling resistance, the latter being the main factors that slow you down on flat roads*.
> 
> d.


 
putting some numbers on that:http://bikecalculator.com/wattsUS.html
for a 150lb cyclist
Pottering along on the flat at 15mph = 100W 
5mph up a 10% hill = 192W

200lb rider
15mph flat = ~100W
15mph 1.5% hill (the slope of a well laid garden patio) = ~200W


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