% Grades of Climbs/Hills. What does it mean?

General cycling advice ( NOT technical ! )
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Heltor Chasca
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% Grades of Climbs/Hills. What does it mean?

Postby Heltor Chasca » 15 Nov 2014, 5:45pm

I went for a 30 miler into Bath via Wellow (Alternate route up Hinton Hill. Eek!) and tried out my Runtastic app. Apart from the plethora of stats it tells me my average grade of climb was 8% and my max was 56%. Yes my lungs burnt, but what does it actually mean? Please explain simply. My maths is pretty dismal. Thank you...hc

BigG
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Re: % Grades of Climbs/Hills. What does it mean?

Postby BigG » 15 Nov 2014, 6:11pm

Something is wrong with your system. 8% is not likely to be an average grade (a rise of 8 m vertically in 100 m horizontally), it is quite a steep hill. Common around Bath of course but far too steep for a railway track. The steepest railway bank is less than 3% and anything above 2% is a major incline. 56% is not only impossible for railways, it is also impossible for cyclists. Your c of g would be so far back when seated that you would do an unintentional wheelie and overbalance backwards.

Mark1978
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Re: % Grades of Climbs/Hills. What does it mean?

Postby Mark1978 » 15 Nov 2014, 6:36pm

2% is a noticeable incline but you can maintain a good pace. 6% it's very much a hill. 10% is a hard hill. 20% is bloody hell you're kidding right (even in a car). But still rideable. 30% is wall like and I've never ridden or driven up one but they do exist. Anything more is basically unknown.

Mark1978
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Re: % Grades of Climbs/Hills. What does it mean?

Postby Mark1978 » 15 Nov 2014, 6:38pm

A friend told me that for an average grade over a full ride then anything over 1% is 'not flat' and anything over 2% is very hilly. From my experience this seems right.

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Heltor Chasca
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% Grades of Climbs/Hills. What does it mean?

Postby Heltor Chasca » 15 Nov 2014, 7:12pm

I'm confused! I've drawn out the 100/8 on some graph paper that my 12 yo donated to the cause and it's not that much of a slope. I've also drawn out the 100/56 slope and it looks steep as are some of the hills between Shoscombe, Wellow and Hinton Charterhouse. Here's a rough plan of my route. (Most of Route 24 actually doesn't follow the old railway from Radstock)

http://cycle.travel/map/journey/8609

To put a spanner in the works my 12yo pointed out that a road sign out of Kilmersdon towards Haydon and Charlton is marked 9%. It's one of the steepest round here. I just don't get it

EDIT: In Mike Carter's book 'One Man and His Bike' (which is brilliant) he mentions a 25% climb in Cornwal out of a fishing village. I'm stumped.

BigG
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Re: % Grades of Climbs/Hills. What does it mean?

Postby BigG » 15 Nov 2014, 9:54pm

The 9% road sign you mention is undoubtedly correct. 10% is about as steep a hill as I can cope with in some semblance of comfort. Anything steeper is a painful grind. Whatever your drawing shows, I can assure you that 56% is absolutely unrideable and undriveable in anything short of a specialised trials car. 8% may not look much on paper, but it is a steep hill in normal parlance. Mark1978's descriptions are absolutely right.

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CREPELLO
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Re: % Grades of Climbs/Hills. What does it mean?

Postby CREPELLO » 15 Nov 2014, 10:23pm

There was some conversataion on this topic a while back..
viewtopic.php?f=7&t=86786

andrich
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Re: % Grades of Climbs/Hills. What does it mean?

Postby andrich » 15 Nov 2014, 10:24pm

The steepest hill that I know of is from Boggle Hole on the Yorkshire coast. It used to be signposted one in Two and a half, which I believe is 40%.

sreten
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Re: % Grades of Climbs/Hills. What does it mean?

Postby sreten » 16 Nov 2014, 1:08am

Hi,

What a hill looks like on paper and its actual slope are very different.
(Of course this does not apply to the perception of real physicists.)

8m in a 100m slope might not sound like much, but 11mph is 5 m/s
so it would take you about 20 seconds to climb 8m, and in a minute
climb 24m. Say an average storey is 4m, thats 6 floors per minute.
(In high risers 3m per storey is nearer, thats 8 floors per minute.)

So cycling 1km up 8% at 11mph will take you 200 seconds, 3 min 20 sec.
In the same time you will have ascended 20 floors of a building, I don't
know how often you do that but I can tell you continually ascending
floors at 10 seconds per floor becomes rapidly very difficult, except
for the uber fit, its very hard work. (I live on the 13th floor).

All I can say about 56% is you've never seen a 56% hill, they don't exist,
not in any tarmac sense, its an utterly ridiculous slope and none of
the hills you mention can possibly be anywhere near that steep.

rgds, sreten.

OldBloke
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Re: % Grades of Climbs/Hills. What does it mean?

Postby OldBloke » 16 Nov 2014, 3:37am

Heltor, from your cycle.travel map it looks like your steepest climb is from the valley between Midford and Combe Down up to Combe Down. From the isos it looks like it climbs 110m (from 40m up to 150m) in about half a mile (say 800m). That give you a gradient of about 13.75m climb per 100m. That is just an estimate, so your gradient will probably be somewhere between 13-15%.

Unless you are pretty fit that will be a hard climb.

OB

tim-b
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Re: % Grades of Climbs/Hills. What does it mean?

Postby tim-b » 16 Nov 2014, 6:33am

Hi

The % is an average over a distance, rather than a spot %

Here's a segment for a climb off the B3110, which was the first near to you that I found on a quick search (it's a bridleway from Hinton Charterhouse) You can look at it in 2D, 3D and spin it around

The average gradient (segment stats) is 6.2%, in 1700m it rises 103m, but the average max is 14.8% for a distance of 204m (2D view, hover your mouse over the red segments) I assume that the 37.1% is over a much shorter distance
Just to add to the confusion, you can't simply divide 103m by 17 to get the average % (works out at 6.06%), it needs to be done using the average of regular % readings

Regards
tim-b
~~~~¯\(ツ)/¯~~~~

pete75
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Re: % Grades of Climbs/Hills. What does it mean?

Postby pete75 » 16 Nov 2014, 7:20am

Heltor Chasca wrote:I went for a 30 miler into Bath via Wellow (Alternate route up Hinton Hill. Eek!) and tried out my Runtastic app. Apart from the plethora of stats it tells me my average grade of climb was 8% and my max was 56%. Yes my lungs burnt, but what does it actually mean? Please explain simply. My maths is pretty dismal. Thank you...hc


56% - a climb of 56 of feet vertical for 100 feet horizontal. Unskiable never mind uncycleable. What these figures mean is the runtastic app isn't working properly.

MikeF
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Re: % Grades of Climbs/Hills. What does it mean?

Postby MikeF » 16 Nov 2014, 9:13am

I prefer the old type of designation eg 1 in 10, 1 in 8, etc., rather than percentages. That way I don't need to do mental maths and it's much easier to visualize. :wink: I know you can argue about whether that's a tangent or a sine, but for small angles (slight gradients) there's little difference.
"It takes a genius to spot the obvious" - my old physics master

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Mick F
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Re: % Grades of Climbs/Hills. What does it mean?

Postby Mick F » 16 Nov 2014, 9:23am

I agree, ratios make more sense.

We live on a two-chevron hill of 1in4, and that's steep enough for me, thank you! :lol:
Mick F. Cornwall

Mark1978
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Re: % Grades of Climbs/Hills. What does it mean?

Postby Mark1978 » 16 Nov 2014, 9:41am

GPS is notoriously bad for altitude. Some apps try to correct this using map data but that too can be sparse and often inaccurate. So you often see this sort of error when looking at grade over short distances.