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How do you figure grade percentage?(12 posts)

How do you figure grade percentage?keith m.
Mar 22, 2001 6:57 AM
for those of you who are talking about grade percentage, I would be interested to know how you are coming up with it. Are you riding with an altimeter? how do you know how many feet you've climbed in order to calculate x distance?
Good question. Anyone know....JamesT.Kirk
Mar 22, 2001 7:51 AM
Does anyone know where you can find grade info? Online resources? If you don't have an altimeter, it would seem to be hard to calculate it yourself.
Mar 22, 2001 7:52 AM
rise/run x 100
Mar 22, 2001 7:58 AM
So a 45 degree angle is a 100% grade? Right?
And a 20% grade would coorespond to an angle of 9 degrees.
Gosh, seems like it would be steeper.
I know the 20% grades I've climbed felt
like they were going straight up.
Two things you should never do ...Humma Hah
Mar 22, 2001 9:25 AM
First, never look down upon areas you thought were steep when you fly over them. It is really disheartening to see what insignificant wrinkles you've been whining about.

Second, if you use the topo map program to determine grade, resist using the 3-d map option at 1:1 scaling. Always use a large vertical exaggeration, or you will get the same effect as above.
what my physics professor told usDog
Mar 22, 2001 2:12 PM
This was incidental to something else, but he said that if you painted a bowling ball, the paint would be relatively thicker than the mountains and atmosphere of the Earth. Now that makes it seem insignificant.

I know what you mean. When I've flown over the monster hills around here, I can barely even find them from the air. Sure, you can pick out the peaks, but what roads go over the peaks?

cue ball analogyJiggy
Mar 23, 2001 7:53 AM
if you blew up a cue ball to the size of earth, it would have bigger mtns and deeper oceans
All the many ways ...Humma Hah
Mar 22, 2001 9:21 AM
Grade is rise over run. I have several ways to get it.

Yes, I do have an altimeter computer on the cruiser ... possibly the only cruiser in California that has or needs one. On any given hill I can get starting and ending altitude within about 5 ft. Alas, the odometer reads in tenth's (it could easily read feet to the nearest wheel rotation, or have a button to give grade, if only Cat's Eye had thought of it. Using tenths of a mile, if you check altitude just when it clicks over, you get 528 ft/tenth.

Or, I have a GPS unit, which can give feet from point A to B pretty well, but is not very accurate for altitude.

I have a protractor level from Home Depot, which I can put on a reference spot on the bike and measure degrees (I use the chainguard on the cruiser. On a roadbike with a horizontal top tube, that would work.) I convert degrees to grade in my head by the following process, which gives a pretty close answer, within about half a percent up to something in excess of 30 degrees:

Divide degrees by 2.
If >4, subtract 1.
If >12, subtract 2.
If >20, subtract 3.

I've been told there's a gizmo for boat trailers that measures directly in % grade. You can also use a carpenter's level and ruler to measure grade.

But the most convenient way I've found was provided by Doug Sloan. Get a topo map program (we use Topo USA, costs $99 and gives you 15-minute topo maps of the whole US!). Trace your route on the map, and it gives a profile chart, and you can measure grade right off the map. The latest version is supposed to be even easier to use to make profiles.
I use Delorme's TopoUSA...biknben
Mar 22, 2001 1:45 PM
You can trace a route along a road and then check its profile. It provides stats like Percent grade and other tidbits.
How I measure gradesDog
Mar 22, 2001 2:03 PM
5%=slows me down a little, sort of like a headwind
10%=man, this is hard, better back off a little
15%=out of the saddle frequently, hr around 95% sustained
20%=legs crying out for relief, front tire gets light, standing nearly all the time, you know it when you feel it

Yea but ...Humma Hah
Mar 22, 2001 2:20 PM
For me its ...

2%=feels like a stiff headwind
5%=better watch the speed or I'll get anaerobic
8%=out of the saddle and suffering at or a little above AT
12%=not for long, even in my off-road gearing.
15%=can climb about 115 ft if fresh.
20-25%=can climb a 20-ft hill with a running start.
I.E. : Are you all saying that.......Skip
Mar 22, 2001 3:19 PM
5 degrees road inclination = 9 1/2% grade
10.5 degrees road inclination = 19% grade
15.5 degrees road inclination = 28.4% grade