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How do you measure % of grade?(22 posts)

How do you measure % of grade?Aztec
Jul 16, 2003 7:43 AM
I want to know the steepness of a climb I do regularly. After watching the TDF and hearing them talk about the grades on some of the Alps climbs I'd like to compare that to something local.

The climb in question (Via Capri to Mt. Soledad in La Jolla (San Diego))is short but steep. Roughly 1 1/4 mile and climbs roughly 1,000 feet. Not sure of the exact height as I could never find an altitude listing for Mt. Soledad (San Diego) but your basically starting a sea level.

Anyone know a formula to determine average grade?
Is there an easy way to measure the actual grade in some sections of the climb?
rise over run for any section you want to measure. nmclimbo
Jul 16, 2003 7:52 AM
nm
Rise / Run x 100 = % grade...biknben
Jul 16, 2003 7:53 AM
In your case the Rise is 1000 feet. The Run is 1 1/4 miles or 6600 feet. The answer comes to 15.15%.

That will put a hurtin on most of us.

It's difficult to compare to the TDF. You can find local stuff that is plenty steep but not nearly as long as what the TDF riders are doing. When I was in your shoes, I remember thinking, "What's the big deal? My local climb is 15%." Then I realized that their 9% climb was 15 miles long and it started to sink in. Also consider the number given during the TDF coverage are averages for the entire climb. Certain sections may be well into the teens while others are mearly false flats.
15% - Is this for real?TheKid
Jul 16, 2003 8:37 AM
I calculated the percent grade for the first climbing section of the Ride Around the Bear and it is about 5%. 23 miles to climb 6,130 feet. I have no concept of what 15% would be? Is there a road in Los Angeles or Orange County that is close to 15% for any distance?
15% - Is this for real?paulg
Jul 16, 2003 9:14 AM
I have climbed short sections of roads that are as much as 24%. Mt. Washington, NH, for example has a 7.6 mile road that has an average of 12% (climbs almost 1 mile verticle), with sections of 18% and 22% at the very end.

So, 15% could be quite common.

Paul.
pittsburgh has a 37% and many in the upper 20swilsonc
Jul 16, 2003 10:05 AM
Pittsburgh may not have long sustained climbs, but its got some nasty steep ones. I'm planning on trying a ride this fall called the Dirty Dozen that does 12 of the more difficult hills in pittsburgh. here's a link to the % grades in Pittsburgh
http://wpwbikeclub.org/pgh_hills.html
OKAY, now I'm confusedjtolleson
Jul 16, 2003 5:42 PM
I've always considered myself to understand grade (rise over run). A 100% grade, if there was a theoretical possibility of such a thing, would then gain 100 ft vertically for every 100 ft traveled. In other words, it would go straight UP, right?

So, I went to your website and found the following definitions of grade...

A 0% grade is perfectly flat and a 100% grade is 45 degrees from the horizontal. The angle is the arctan of this number (37% = 20 degrees)

Is that right? If a 100% grade is 45 degrees from horizontal... shouldn't it be 90? waaah
It is confusing but...biknben
Jul 16, 2003 7:11 PM
The info you quoted from Pittsburg is correct. A 100% grade equals a 45 degree angle. Strange indeed. If you went straight up there would be NO run. In that case you don't move forward at all.
15% - Is this for real? Avg grade for Mt Washington 12%TheKid
Jul 16, 2003 10:28 AM
I was asking what rides would have an average grade of over 10% for a long stretch. I understand for short sections the road could be very steep, but for the total ride it would have to be pretty outrageous to average 15% on a road regulary used by cars. I would tend to agree with JS Haiku's gradient calculator.
Quote from Mt Washington Hill climb site...biknben
Jul 16, 2003 7:17 PM
Taken from hill climb web site: The Mount Washington Hill Climb is quickly becoming known as the toughest hill climb in the world and as Dick Devellian, past Race Director, says "This is the World Championship of hill climbing. If someone wants to say they are the best climber in the world then they need to prove it here on Mount Washington."

The Mt Washington Auto Road is 7.6 miles in length, has an average grade of 12% with extended sections of 18% and the last 50 yards is an amazing 22%!
---------------------------------

I'm doing the "practice ride" on Sunday. I'll let you know what I think. I put a MTB rear der. and cassette on my road bike this week.
Some L.A. climbsmapei boy
Jul 16, 2003 2:51 PM
According to the inclinometer function on my Specialized Speed Zone Pro computer (sorry Doug, I do trust the thing), Encino Hills Drive from Hayvenhurst to Mulholland Drive in Encino varies between 13% and 20% (mostly 16% to 17%) for a little less than a mile. Fargo Street in Echo Park in LA is fairly short, but it is officially measured at 32%. It is also officially the steepest street in the State of California.
re: How do you measure % of grade?dirthead
Jul 16, 2003 8:03 AM
The formula for % grade is rise/run.

I have done actual measurements of hills in the past. What I did was take a long straight board (8' 2x4) and a 48" level. Start at the bottom of the hill and place the board on the road with the level sitting on top of it. Raise the downhill side of the board until it is level. Measure the distance from the end of the board to the road, this is your rise. Your run is 96", the length of the board. Now you can use the formula rise/run to determine the %slope. You will need to do this at as many places as possible going up the hill and average the results. This will give you a good idea of the % grade.
re: How do you measure % of grade?paulg
Jul 16, 2003 8:03 AM
Looks like you got the answer for figuring average grade. To find out grade in specific areas of the climb you would need to measure the slope angle with a level protractor. The tangent of the angle x 100 gives you % grade. For example (this wouldn't be something you could ride), but if the slope measured 45 degrees, tan (45)x100= 100, or a 100% grade, meaning the rise and run are equal.

Paul.
fyiDougSloan
Jul 16, 2003 8:23 AM
M_Currie "percentage true slope vs. road distance variation" 7/3/03 8:24pm
J's amazing gradient calculatorJS Haiku Shop
Jul 16, 2003 8:40 AM
2% sprinting big-ring (53)
5% springing little-ring (39)
7% looking for beer on roadside
9% groveling 39/29
12% groveling 30/32
15% 20 rpm, wishing for anvil from sky
18% walking
if >18%, in car with 4wd
My personal cadence record (low)jtolleson
Jul 16, 2003 9:32 AM
was 30 rpm on a 17% stretch. Just miserable.
Thanks for the replysAztec
Jul 16, 2003 8:55 AM
15% is probably not completely accurate as I don't know the true gain in elevation. It may be 850 feet, it may be 1,050. Somewhere in that range.

No doubt the tour riders are taking on much longer climbs and they are getting into them after 100 miles and previous climbs. They are studs.

If I am short on time I'll generally climb to the cross on Mt. Soledad from 2 or 3 different routes including Via Capri once. If I'm going for a longer ride I'll generally see how I feel and then try and finish with Via Capri. Yesterday we did 30 miles after work and then finished on the climb. As I was snailing along at 3.8 mph up the hill I had lots of time to think about the grade.
If you're interested...No_sprint
Jul 16, 2003 9:07 AM
I have a file with about 20 local LA climbs, their distance, elevation gain, and true average grades with notes on steepest pitches. If you know any part of LA you can try to compare. I believe climbing grade is greatly exaggerated by people for the most part. In my opinion a one mile climb of 10% average grade with peaks at 14/15% is pretty darn nasty.

I can email it to you if you'd like.

No_sprint
at
yahoo dot com
Topographic maps.Chen2
Jul 16, 2003 11:11 AM
It's easy to calculate % grade from a topographic map, within reasonable accuracy limits. Pick two points on the map, read the elevations using the contours, measure the distance. Then you have the "run" and "rise". This works well if your measurements are along a straight road. Sometimes I use maps from www.topozone.com, they are free but the scales 1:50,000, or 1:25,000 aren't as easy to use as the more standard 1:24,000 which is the same as 1" = 2000'. If you have access to the DeLorme software (not free) it will print topo maps 1:24,000.
~Al
A few points first:Alexx
Jul 16, 2003 12:52 PM
The "run" mentioned is HORIZONTAL distance, not the inclined distance. At 15%, the error will be better than 10% from one to the other.
As far as "what does a 15% grade look like?", well, the steepest mountain climb on an intersate (El Cajon, Cajon Summit, 4th of July pass, Donner Pass, Cabbage Patch, Snoqualmie, etc...) is never greater than 8%. Pavement will start to slump downhill at around 20%. Most loaded tractor-trailers are only able to pull 15% in the lowest gear, at maybe 3 mph.
error not nearly that muchDougSloan
Jul 16, 2003 12:59 PM
Check my "fyi" post above. The error is very negligible. You can use the road distance for the run.

Doug
Sky MountiDathon
Jul 17, 2003 2:44 AM
I have this little gadget on my handlebars that allows me to see the percent grade very easily. Really neat item.

http://www.velimpex.com/about_inclinometer.php?pg=about_inclinometer&secpg=about_inclinometer&PHPSESSID=2d9d966c0e78b577aeb428c726f039b0