Elevation charts and percents

[nikkoblu2]

Not quite sure if this should be in the "newbie" threads, but you ladies have always been so great responding here...what the heck.

I'm thinking of doing the Fall Foliage ride in Hazleton, PA in October (charity ride). I've done the 50k (which had some brutal hills) and am thinking about doing the 100k. I'm hoping for an explanation of the percentages used in elevation charts.

I'm certainly familiar with degrees. If someone said "it was a 45º hill" I would be able to visualize. But, I don't understand the meaning of percentages.

I remember a roadie saying on this ride the last time I did it "there's a 10% hill". I was thinking 10 degrees at the time and what's the big deal. Holy hold my socks on...talk about flying!

The elevation starts at about 1,950 ft at -4%. It has a total ascent of 2,021 feet and a total descent of 2,005 ft. It ends back at 1,950 ft at +4%.

I understand the feet, but the percentages just aren't clicking. Anyone?

[OakLeaf]

It's the ratio of elevation gain to horizontal travel. You have to visualize the hill as a right triangle.

A 45° angle (no such thing in roads AFAIK!) would be a 100% grade because the two sides of the right triangle are equal, as you travel the hypotenuse.

If you gain 100 feet in 1000 feet of horizontal travel (not surface travel), that's a 10% grade.

[nikkoblu2]

Exellent explanation Oakleaf! You da bomb! Fortunately, I actually do remember some of the stuff I learned in geometry.

[Rebecca19804]

Thanks nikkoblu2 for posting this as I've been wondering the same thing!

A 45° angle (no such thing in roads AFAIK!) would be a 100% grade because the two sides of the right triangle are equal, as you travel the hypotenuse.

So Oakleaf, if I'm understanding this right, this example means:
45° angle = gain 1 foot in elevation in 1 foot of horizontal travel
= 1:1 grade [I get ratios ]
= 100% grade
= IMPOSSIBLE?!

[TrekTheKaty]

This sounds doable. 2000 ft in a metric sounds like "rolling with a few big hills." Our local club has the following rankings:

Flat
Rolling
Moderately Hilly--I can do these, but it slows my pace considerably
Hilly or "billy goat"--DH goes to these alone!
(with the possibility of "a few big hills")

I pulled up the course map and it appears to start at the "top", go downhill, then flat to rolling with a big hill at the end. Personally, I would conserve and be ready for end. Maybe even going out for a training ride on the end of the course, if possible.