What's grade%

[HEYBOSS]

This may be a stupid question but I'm curious to know.

What is or better yet how does one know what a hill's % grade is?

 

[Gary - K7GLD]

Well, ummmm, first we gotta know WHICH hill yer talkin' about...



Grade percentage is based upon how many feet the road rises in a distance of 100 feet - thus, if a road climbs 5 feet per 100 feet traveled, it's a 5% grade...

 

[swamp rat]

Or if you're headed the other way, how much a road drops per 100'.

 

[Thomas]

Here you go—it's rise over run.



For simplicity, imagine a road with no curves. Also imagine your movement from one place to another as having two components—vertical (Rise) and horizontal (run).



If, in traveling from one spot to another , you travel so that the rise is 7 feet and the run is 100 feet, the slope is 7/100 or . 07 or 7%. Notice that in this example your actual distance traveled is more than 100 feet.

 

[CBratten]

The easiest way to explain this is :If you are going down a grade that is 6% , every 100 feet ,you will drop 6 feet. The % is an average for the entire grade,in some parts of the grade it will be more and in some it will be less.

 

[HEYBOSS]

Ok, now how does one know how many feet a hill has on the rise or drop?

 

[Koa Man]

Two ways you can determine the % grade of a hill. Use a clinometer, I have a Suunto, but several other companies make them. Another way is to take a 48 inch level, put one end on the high side of the grade, adjust the level till it is level and measure how many inches it is from the bottom of the level on the other end to the ground. Divide that number by 48 and that is the percent grade. If it is 3 inches from the level to the ground, that would be a 6% grade. 12 inches would be a 25% grade. I think the results will surprise many people. Most hills are not as steep % wise when actual measurements are taken. 8% grade is a monster.



Oh, be sure to take your measurements when there is no traffic or safely on the side of the road. Would hate to see a fellow TDR member get run over by a Duramax.

 

[HEYBOSS]

TDR member get run over by a Duramax.



I think I'll be safe taking the measurements on top of the hill. I don't think the Duramax will make up in time to run me over!

 

[Oasis-3]

Runover by a Duramax

The Duramax would have to be going down that 8% monster grade

 

[SteveH]

Most states post the degree of grade when it is 6% or more. I don't know about how it works now, but special Federal intervention and a permitting process was necessary for any highway receiving federal money if the grade was over 7%. I don't think I have ever been on an 8% grade, travel from Tex, CO, MT, WY, SD, ID, WA, OR, UT and have never seen one that I remember, but then again I put my tea water in the micorwave today and forgot to turn on the microwave, so who knows?

 

[Scollins]

Originally posted by Steve H

Most states post the degree of grade when it is 6% or more. I don't know about how it works now, but special Federal intervention and a permitting process was necessary for any highway receiving federal money if the grade was over 7%. I don't think I have ever been on an 8% grade, travel from Tex, CO, MT, WY, SD, ID, WA, OR, UT and have never seen one that I remember, but then again I put my tea water in the micorwave today and forgot to turn on the microwave, so who knows?

Well, it is not on a freeway or highway, but there is a street with a 20% grade (!!!) in Tukwila, WA. This is just off I-5. I think this hill would be an awesome test of towing abilities between Cummins/Navistar/Duramax equipped trucks.

 

[Bob Beauchaine]

In June of 1999 on Utah Hwy 12 between Escalante and Boulder I found some 12% grades - not very long but very steep.

Happy Trails

 

[mbrolin]

I know there is a 10% and 8% grade on Hwy 253 between Boonville,Ca and Ukiah,Ca. Gives the ebrake a good workout with the 5er in tow. Not sure of grade on the Grapevine going into LA. I do know its a long pull and a long ways down into the San Joaquin Valley. Theres a 10mile 6% grade just east of where I live going into the Cascade range. Been on quite a few trips where there are steep grades pulling the 5er. The Cummins loves to pull these grades loaded. Naturally not going to set any speed records going up or down but it can be done safely.

 

[Joe G.]

One of the Sierra passes has a grade of 26%. I think it's Sonora. A picture of the sign was posted some time ago but I can't find it with a search.

 

[SteveH]

Originally posted by Joe G.

One of the Sierra passes has a grade of 26%. I think it's Sonora. A picture of the sign was posted some time ago but I can't find it with a search.

If you find it I would like to know exactly where it is. I'm aware of some dirt trails that surpass the 7% grade and drive all over the northwest, thru Colorado, Wyoming, New Mexico, Ariz, Idaho, Montana, and have never seen any grade on a state highway that was over a posted 8%. Guess I need a picture of a sign where the true grade, as determined by the state it is in, is over 8%.

 

[CBratten]

The grade for the Monteagle Mountain(Tennessee) is 6%. I deliver

Propane gas to homes on the Tims Ford Lake. Don't know the grade on the drive ways,but is a lot more than 6%. Have to pull the truck in the drive and back out, if not done this way the front end comes off the ground when the liquid runs to the rear of tank.

 

[wyosteve]

Steve H. I agree with you, most grades in the west are from 5-8%. The most I've seen is Wyo. Hwy. 22 from Jackson Hole across Teton Pass to Driggs, ID. It's posted at 10%. I'd have to see a 26% to believe it.

 

[Doc Tinker]

OK - Someone tell me what the grade is on that hill going into Big Bone Lick State Park, in Kentucky.



Doc

 

[Joe G.]

I found the thread. The picture of the sign is no longer on photopoint.





https://www.turbodieselregister.com...did=18191&highlight=sierra+and+pass+and+grade

 

[CJ Johansson]

OK, for you non-math wizzes, another way to figure % grade is this:



%grade = tan(angle) * 100



So, just to give you an idea just how flat those big hills really are, study this for a moment:



deg %grade

1 1. 75%

2 3. 5%

3 5. 2%

4 6. 99%

5 8. 75%



Most people have an understanding of angles, it's kinda surprising that most roads have a slope of only 4 degrees or less. That 26% grade that was mentioned converts to a mere 14. 6 degrees.



I've got a hay field that's mostly 22 to 24 degrees, or 40-44. 5% grade Needless to say, it's... ummm... interesting to drive up and down that field, even more interesting to side-hill it



-cj