Calculating hill gradient

balzaccom · Sep 1, 2008

There is a very short section of Highway 108/Sonora Pass in California that is posted as a 26% grade. And it's above 8000 feet. I have ridden some of this road, (not all of it!) and can tell you that it is steep. How steep? I'll let one of you more tech-successful people do the calculations from Kennedy Meadows to Sonora Pass...and yes, there are some flatter spots along that path!

wim · Sep 1, 2008

Obsessed.

If you really want to know the exact grade of a short stretch of road, do what I did to settle an argument: get a straight piece of tubing, tape a long carpenter's level on it and measure rise and run on location as shown by yours truly here in the photo. Keep your ears open for cars . . .

Touch0Gray · Sep 1, 2008

rise over run, just like a roof

runningdog · Aug 9, 2009

Here is a calculator http://www.csgnetwork.com/inclinedeclinegradecalc.html

jiggs · Aug 10, 2009

if you download googe earth and search for the hill

than go to tools, click on rulers, and in that window click on paths. you can click all the way along the road in short pieces so you can go around corners, that will get you the distance. Than put the cursor on the start, mark the elevation, and go to the finish and mark the elevation. Divide the total elevation (in feet) by the distance in feet,( 1 mile = 5280 feet) and you will get the degree of climb (close enough)

JoelS · Aug 10, 2009

17% is super hard. And one that goes on for 4 miles? I don't buy it. There's probably a section that steep, but not the entire climb.

I did a road today what has a good section of 16% (about 1/4 mile) followed by a 12% false flat for a hundred yards, and then a couple hundred yards of 14%. Numbers off my Garmin while riding. That hill is stupid hard and the whole thing is about 3/4 of a mile.

I've done a few sections of 20%, but that lasted like 50 feet and could easily be powered up. The last 500m of Mt. Diablo are just crazy, but manageable.

There is one climb near here, Mix Canyon. The 2nd half Avg is 13.4 for about 2 miles. It starts out shallow and ends at something like 24% for the last 1/2 mile or so. I haven't been brave/stupid enough to try to climb it. The only way back down is the way you went up. That makes me nervous.

I like to climb, but some of the steep stuff is just flat out painful. And I need a compact. That should help over the standard double I'm using now.

Touch0Gray · Aug 10, 2009

it really isn't that hard

to calculate with topo maps ....it is rise over run... period...I am no math wizard but it is simple arithmetic.

The USGS has excellent websites!

Blue CheeseHead · Aug 10, 2009

Here is a sign that I can tell you is not correct. It was a steep descent, but it certainly did not average 18% for 2 miles. Perhaps a short sections within that 2 miles pitched to 18% (Meyers Grade for those of you doing Levi's ride)

Now, this is the hardest section of road I have ridden. It is on Skaggs Spring Road. 708' in .89 miles = about 15% average. Maybe by legs were burning from all the other climbing to get to this point from Lake Sonoma, but this secton is where I learned about the virtues of riding a serpintine path up the road (oh and I didn't mind my triple with a 27 either

). My Garmin had 19% for a good portion of that climb.

MattSoutherden · Aug 10, 2009

Some pics from Honister Pass in the Lake District National Park (England), from a ride I did a couple of months back.

There are also Hardknott Pass and Wrynose Pass which join Eskdale to Langdale. Both of which have sections over 30%. Anyone who's a complete maniac can sign up to the Fred Whitton Challenge which does all three, and more, in one insane sportive.

erleichda · Aug 11, 2009

I think MMR is not TOO far off. You'll get varying answers depending on what distance of the hill you map. But I often map an entire street from bottom to top and look at what portion of the hill is what % at what distance merely as a comparison. Looking at the west hills of portland, for example, I see that the gentle gradient I have ridden maxes out at 8%, with most at 6%. The steepest route over the hills is half the distance (2mi instead of 4) and has sections reported as 12% with much in the 7-8% range. I am sure it isn't entirely accurate but makes enough intuitive sense to use casually.

A local (eugene, OR) testifies that his mapping program is more accurate for elevations but doesn't calculate the grade for you at ridewithgps.com

wim · Aug 11, 2009

To find out the absolute maximum grade percentage, you can't beat a long straight rod, a bubble level and a centimeter rule. Support one end of the rod on the road. Lift the other end up until the rod is exactly level. At a marked distance (say, 2 meter) hold a centimeter rule at 90 degrees to the rod and measure the rod-to-road distance. Grade percentage is rise over run x 100.

Example: 2 meter (200 centimeter) level rod rises 40 cm = 40 / 200 x 100 = 20%.

jasonwells4 · Aug 11, 2009

dave_gt said:
Again, it ain't rocket science!

I think you get the idea from the posts here that the 20% is either calculated wrong or, most likely, exaggerated!

Just think about a 20% grade...that is 20 feet up for every hundred feet you travel. THAT is extreme! I doubt you will find that anywhere on paved roads. Most likely 10-12% for short stretches.

Come visit SF. We have a couple 31.5% hills!

http://en.wikipedia.org/wiki/Filbert_Street_(San_Francisco)

jasonwells4 · Aug 11, 2009

JoelS said:
The last 500m of Mt. Diablo are just crazy, but manageable.

Yeah, my garmin edge measured that as 17%.

untoothedyouth · Aug 15, 2009

jiggs said:
than go to tools, click on rulers, and in that window click on paths. you can click all the way along the road in short pieces so you can go around corners, that will get you the distance. Than put the cursor on the start, mark the elevation, and go to the finish and mark the elevation. Divide the total elevation (in feet) by the distance in feet,( 1 mile = 5280 feet) and you will get the degree of climb (close enough)

I cant figure out how to "mark the elevation". It keeps telling me that it is still 0meters at the start of the climb and at the end.

jiggs · Aug 15, 2009

just put the cursor on the begining of the climb and move

untoothedyouth said:
I cant figure out how to "mark the elevation". It keeps telling me that it is still 0meters at the start of the climb and at the end.

it to the end of the climb. Read the elevation at the bottom and subtract the bottom reading from the top reading for the total climb.

jiggs · Aug 15, 2009

excuse me but I think 2 metres is a bump not a hill.--

wim said:
To find out the absolute maximum grade percentage, you can't beat a long straight rod, a bubble level and a centimeter rule. Support one end of the rod on the road. Lift the other end up until the rod is exactly level. At a marked distance (say, 2 meter) hold a centimeter rule at 90 degrees to the rod and measure the rod-to-road distance. Grade percentage is rise over run x 100.

Example: 2 meter (200 centimeter) level rod rises 40 cm = 40 / 200 x 100 = 20%.

sorry about that.

jiggs · Aug 15, 2009

BTW the Mount Washington auto road bicycle hill climb is

about 4740+ feet of elevation over 7.6 miles and is about 11 % gradient and is steeper than any Tour de France climb. It does have a short section at the top which is 22% I believe. My results for that on, Bob Schofield
MALE AGE GROUP: 65 to 69

Place O'All Race# Age Time Rate Name Age Sex Race# City/state
===== ===== ===== === ======= ==== ======================== === === ===== =======================
1 241 790 67 1:32:28 4.9 Bob Schofield 67 M 790 Hamiolton ON
2 320 782 66 1:39:16 4.6 Bill Chapman 66 M 782 Concord NH
3 361 781 66 1:44:43 4.4 John Cederholm 66 M 781 Marion MA
4 381 783 66 1:47:13 4.3 Tom Fortmann 66 M 783 Lexington MA
5 384 787 66 1:47:34 4.2 John Marshall 66 M 787 Addison ME
6 486 789 67 2:09:24 3.5 Lockett Pitman 67 M 789 Westcliffe CO
7 492 785 65 2:13:04 3.4 M C Malboeuf 65 M 785 Warrreb VT
8 500 788 69 2:15:32 3.4 Jackson McCarter 69 M 788 Travelers Rest SC
9 509 786 69 2:18:15 3.3 Richard Marriott 69 M 786 Mirror Lake NH
10 511 784 69 2:20:18 3.3 Bill Hamilton 69 M 784 Marblehead MA
Record 1:31:22 by Harry Parker in 2001

wim · Aug 16, 2009

jiggs said:
sorry about that.

Sorry, you don't understand the procedure. The 2-meter rod is placed on any part of the steepest section of a climb. It doesn't matter how long that steepest section is.

Dajianshan · Aug 16, 2009

http://veloroutes.org/tools/

jiggs · Aug 16, 2009

hey that works. That is the best calculator for gradient

Dajianshan said:
http://veloroutes.org/tools/

I have seen, I know that the calculation detemines one section of the hill only and depends on where you start and finish. I rode a section yesterday that rises 600 feet but the first 100 feet is really only 2 or 3 % so I calculated the 500 feet because that was much steeper.

Calculating hill gradient

balzaccom

wim

Touch0Gray

runningdog

jiggs

JoelS

Touch0Gray

Blue CheeseHead

MattSoutherden

erleichda

wim

jasonwells4

jasonwells4

untoothedyouth

jiggs

jiggs

jiggs

wim

Dajianshan

jiggs

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