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Thread: What's the %

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    What's the %

    Can someone explain what a 6% or 10% grade hill really is?
    I read posts that describe rides with hills of various grades
    but I have trouble visualizing how steep that really is.
    I can visualize 45 and 90 Degrees. ( canít ride it though ) but 6% of what ???
    6% of 90 Deg. Would be 5.4Deg ???


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    Rides again HiYoSilver's Avatar
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    I had to relook it up as not obvious.

    slope== % road grade

    Grade is defined as the ratio of the change in elevation (or vertical distance) to the change in horizontal distance.
    If a 3/4 -mi stretch of road has an average 8% grade, then what is the corresponding change in elevation over this distance. Express the answer rounded to the nearest whole number of feet.

    ans
    316 feet

    Thus grade % == Distance/elevation change
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    Last one to the top... Little Darwin's Avatar
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    +1

    In order to get an angle if given the grade, you need to use trigonometry.

    However, for reference a 100% grade would be 45 degrees...

    And from reading in the forums, a grade of over 10% seems to be considered a significant climb.
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    Senior Member DaveTaylor's Avatar
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    O.K. Here is something a little easier to visulize: A 6% grade will rise 6 feet every 100 feet. Similarly, a 10% grade will rise 10 feet every 100 feet. So, say you are looking out your front window and your property is 100 feet wide and one side is 10 feet higer than the other, that's a 10% grade, quite steep!

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    Just shy of 400W ranger5oh's Avatar
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    That last guy's post is correct.... just a little hard to read .

    Basically... just divide vertical distance travelled by horizontal distance travelled.

    6% grade is 6 feet up and 100 feet over.

    6/100 = .06 = 6% grade

    9/100 = .09 = 9% grade

    and so on....

    [edit] - like 3 people posted in between me and dgreg... thats who I was referring to.
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    Thanks everyone I understand. Now that I see it in print
    I remember that from a long to ago. It's funny how easy
    it is to forget things you don't need at the time.

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    One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.

    Most states set a maximum grade of between 6 and 8 percent for recently constructed roads. So think about a steep climb in your area and it is probably in that range.

    The steepest grade that I know of in the US is a 22% grade which happens near the end of the road up Mt Washington in New Hampshire (overall that road has a paltry 12% grade)

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    Berry Pie..the Holy Grail GrannyGear's Avatar
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    [QUOTE=sauerwald]One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.

    QUOTE]

    I'm thinking of Interstate 5 going over the "grapevine" that divides central from southern CA....surely that is more than 3%? Anybody know?
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    [QUOTE=GrannyGear]
    Quote Originally Posted by sauerwald
    One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.

    QUOTE]

    I'm thinking of Interstate 5 going over the "grapevine" that divides central from southern CA....surely that is more than 3%? Anybody know?

    I thought the steepest grade was 6%.
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    [QUOTE=GrannyGear]
    Quote Originally Posted by sauerwald
    One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.

    QUOTE]

    I'm thinking of Interstate 5 going over the "grapevine" that divides central from southern CA....surely that is more than 3%? Anybody know?
    We have freeway grades (I-70) of 7% in Colorado. Heck, you couldn't make it over the Rockies at 3%. It would be impossible, unless you extended the highway, and built it up, almost to Kansas!

    Where in the world did that 3% figure come from?

    http://www.tfhrc.gov/pubrds/pr97-12/p18.htm

    Applications such as static warning signs, truck speed limits, and educational videos
    at state weigh stations have all been used to minimize this condition. The Dynamic Downhill Truck Speed Warning System (DDTSWS), developed in 1995, provides specific information to individual truckers before they enter the steep grade sections. The first DDTSWS was placed west of the Eisenhower Tunnel in the westbound lanes of I-70. DDTSWS uses inductive loops, WIM technology, and a VMS. First, the trafAc loop detectors trigger the system. Then, WIM determines the truck weight, speed, and axle configuration. Finally, an algorithm within the computer system computes a safe speed based on this information and alerts the driver through a VMS. Since its deployment, truck-related accidents have declined on these 6-percent and 7-percent grade sections even while the volume of truck trafAc has increased by an average of 5 percent annually. Currently, British Columbia, Oregon, and West Virginia are designing and constructing similar systems.
    Last edited by DnvrFox; 06-15-06 at 01:13 PM.
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    feros ferio John E's Avatar
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    For those familiar with the Los Angeles area, the southbound grade on I-405, from the San Fernando Valley toward the Los Angeles basin, has a maximum grade of 6%.

    When I lived in L.A., my favorite killer ride was Tuna Canyon, just north of Topanga in the Malibu hills -- something like a 10-12% grade over a distance of 3 mi / 5k km.
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    Quote Originally Posted by sauerwald
    One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.

    Most states set a maximum grade of between 6 and 8 percent for recently constructed roads. So think about a steep climb in your area and it is probably in that range.

    The steepest grade that I know of in the US is a 22% grade which happens near the end of the road up Mt Washington in New Hampshire (overall that road has a paltry 12% grade)
    If this were true, they sure lost the rule book as what is allowed. We just pedaled on US freeways from CA to AZ and NM. 6% is more like what we have seen.
    Also, recently constructed roads have exceptions. (always exceptions) We measured up to 15%.

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    Quote Originally Posted by CyberDaug
    Can someone explain what a 6% or 10% grade hill really is?
    I read posts that describe rides with hills of various grades
    but I have trouble visualizing how steep that really is.
    I can visualize 45 and 90 Degrees. ( canít ride it though ) but 6% of what ???
    6% of 90 Deg. Would be 5.4Deg ???
    If you ride horizontally 100 feet and the road also rises 6 feet you have a 6% grade.

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    I ride offroad and I always judge a hill by the distance ridden divided by the Height climbed. This is where the metric scale gets easy as I have a hill that is just under 1 mile long on the map but I round up or down and I take that as 1500 metres. It has a 200 metre height climb, so that is easy. It is a 1 in 7 1/2 hill or 100/7.5 or 13%, so that equals a hill I don't want to climb Twice in a day.And that will be an average and some parts are over 20%

    My legs tell me how steep a hill is, so forget %age offroad. Now on the road we have little signs that say the %age of the hill. Have never been able to work out if that will be the steepest part of the hill or the average for the hill. Then there is a hill I remember from my Youth. A 1 mile almost straight road covered over with trees and that goes straight up the North Downs. (as opposed to the South Downs I now ride) I used to use it on my crosscountry road training runs. Park the car at the top of the hill, do a Hilly circuit of about 10 miles that did include an even steeper hill going down, and finish up sprinting up that hill. Still remember the sign now as it used the old form of hill marking and this was 1in4 or 25%. No wonder I now have no knees.


    Now forgive if I upset some people here but a hill is something you are going to feel. 6 ft rise in 100ft is a pimple. However 600 ft in 10,000 is going to hurt. even if it just a gentle slope-Initially.

    This is from the rider that stuggled last week up a 5% slope for 800 yards. Have to get used to these small gears on the road bike.
    Last edited by stapfam; 06-15-06 at 02:45 PM.
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    There's a couple climbs on a route I do for training in the NC mountains that measure at 20+%. They are not really long, but one of the stretches goes from 10% immediately to 20% and it is a very distinctive road grade change. It can really psych you out. I popped a wheelie the first time I went up it....

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    just over the next hill cruzMOKS's Avatar
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    My driveway is 22% and I have pulled my front wheel off the ground a few times.
    Enjoy the ride.
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    Cruz
    According to DeeGee 50 + ers don't post after 10 pm,
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    Quote Originally Posted by cruzMOKS
    My driveway is 22% and I have pulled my front wheel off the ground a few times.

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    Quote Originally Posted by CyberDaug
    Cruz
    According to DeeGee 50 + ers don't post after 10 pm,
    you don't want to prove him wrong now do you?

    (How come nobody posts after 10 o'clock in this forum? Are you all in bed? Isn't anyone a nightowl? What am I supposed to do -- get a life? Or hit the sheets? C'mon, I want fresh, thought provoking, informative, insightful or at least funny posts late at night! Geesh! Is that asking too much?

    l . . .
    C'mon dude, they're all resting so they can ride better the next day. Lack of sleep really messes up the rides.
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    Me and the cat... Pamestique's Avatar
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    I have driven roads in California that post a 10% grade. The steepest grades I ever rode were in Utah and Texas. Utah had long hills (a mile or so) at 15% and in Texas, thankfully these were very short, but the grades were close to 20-25%. Gads, they seemed straight up and down!!!!! If you stop in the middle, just start walking...

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    feros ferio John E's Avatar
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    Quote Originally Posted by cruzMOKS
    My driveway is 22% and I have pulled my front wheel off the ground a few times.
    That IS steep! Some of my friends in Los Angeles had to get a special variance for a 19% driveway.
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    I don't use grade as a measure, I like to use puke factor. If I feel like I want to puke when I get to the top than it must have been a pretty good grade. This whole conversation has me thirsting for a climb up l’Alpe d’Huez, what do you say?

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    Senior Member jazzy_cyclist's Avatar
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    My shared driveway is about 1/3 mile and 8-10%; my heart rate gets up there by the top.

    But I think Stepfam had a good point -- I could do 10% for a 1/2 mile, but I couldn't do it for 2 or 3. So I think there's a big difference between a sustained hill versus the "rollers" where I live.

    I lived in the Bay Area a long time ago, but I don't remember what the grade was on those hills in San Francisco - probably up to 15% I'd guess.

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    Quote Originally Posted by sauerwald
    One way to think about it is this:

    On US freeways, the maximum allowable grade is 3%, so think about the steepest freeway climb you can, it is probably 3%.
    I think 3% is the maximum for a class 1 railroad. Actually 2% is very steep for a railroad.

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    Hwy 40 Blue Hwy 40 Blue's Avatar
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    All I know is, I once did a loaded tour with 40 pounds of gear on the bike, and I came up to a series of hills and the sign said some of 'em were 13%, and I ended up walking a lot. Those pedals would not turn.

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