What's grade%

[dewdo]

Last year I drove US hwy 15A going west into Yellowstone from Wyoming with my 11. 5 camper. I ended up going down an 18 mile 10% grade followed by another 8 miles of 8%. Hairpin turns all the way and the exhaust brake was useless since I could never get about 25 mph. Smoked the brakes. The name of that particular stretch of highway is OMGH. That stands for "Oh My God Hill. " Never will travel that way again.



Dewdo in the other Washington

 

[John Berger]

There is an 8% grade on I-26 just north of the NC-SC state line. I run it 4 times a year during my trips to Bristol, Tennessee for the Cup races. The sign is posted at the top of the grade heading east or down the grade. There is another one further north on Highway 19/23 that is a 9 % grade. I'll try to get pictures next month when I go up that way. I'm taking my travel trailer and looking forward to taming that grade on I-26.

 

[SteveH]

Re: Re: What's grade%

Originally posted by 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.

In my post, I stated that I have never seen this kind of grade on a normal highway. We can all find driveways or mountain off-roads that are considerably greater than 6-8%, but face it, a 26%grade would eliminate every rig that is out there pulling any kind of trailer. Butte hill is a long pull and is 5-6% and semi's are slowed down to 20 mph. Raton pass is about the same and every pickup with a large camper and every semi is going about 30 mph. I drive these passes every year and know what I see. What would these all do on a grade that is 4 times greater than these passes? 26% on a state highway - No way!

 

[wyosteve]

Steve H. I know Raton pass well. Pulled it twice in the last month with a 20' gn horse trailer loaded w/ 4 beasts and a 32' enclosed car trailer. Was able to stay in 5th all the way up around 50-55, but the engine temp got so hot it melted my boost gauge tube both times. EGT's were fine, just coolant temp got close to the H mark. Glad I don't have to do that one every day.

 

[illflem]

Steve, the thread that had the picture of the 26% sign is gone but here's another discussion of Sonora Pass. I don't believe it is 26%, but it is at least 20.

 

[SteveH]

Originally posted by illflem

Steve, the thread that had the picture of the 26% sign is gone but here's another discussion of Sonora Pass. I don't believe it is 26%, but it is at least 20.

Thanks for the new thread. They are in a part of the world that I have never traveled in. I can't imagine a major state highway being anywhere near that steep. I don't think a semi could even pull something like that. Makes me want to go out that way and ride one or two of them!

 

[DNelson]

I always figured grade vs. degrees this way: 100% grade is 90 degrees (vertical), and 0% is flat. Do the percentage math and you have the degrees, given the percentage. Thus, a 50% grade is 45 degrees (god forbid!), and a 7% grade is about 6. 3 degrees.



Don

 

[Thomas]

Don,



It doesn't work like that. From a mathematical point of view grade is the tangent of the angle that the road makes with a horizontal line—expressed as a percent. Your "45° angle" has a grade of 100%, and the 90° angle has an undefined grade.



CJ Johansson, in his post further up, has prepared a table of more commonly encountered grades as well as a method for converting angle of road to horizontal to a grade expressed as a percent.

 

[Joe G.]

Steve,



If any big rigs run that road they are logging trucks and they go places you can't believe. We have some BAD roads that are state highways. For example hwy 299 goes between Redding and US101 and hwy 36 goes between Red Bluff and US 101. Both towns are on I5 and it's almost the same distance, about 150 miles. It takes about three hours on 299 and eight hours on 36. There is a sign near each end of that stretch of 36 that says that trailers are not recomended. They ain't kidding!!

 

[Forrest]

Not recommed for towing

Joe G. , I think you're right. From the Hwy 395 side just N or Bridgeport, there is a sign to that effect. It's got hairpin corners & you can smoke the breaks solo

 

[Joe G.]

You got it. It's not only state highways that are bad. US 101 has some places in Mendocino County that have a sign that says that trucks over 40' from the king pin to the rear axle are not recommended. It's a problem for Eureka since the feeder state highways also have a sign like that. The biggest trucks don't come here. There was an engineering study of building a bypass for the three mile section just entering Humboldt County from the south. Something like 240 million bucks just to get around three miles. The proposal was rejected so we still have to drive thru Richardson's Grove to get into the county. The bark is knocked off the trees on both sides of the road. Meeting trucks is a thrill.

 

[Steve M]

If you have a particular hill in mind, send the DOT of your state an e-mail. I did this and they responded the next day with the grade in question and the length. They were real friendly about it.

 

[merryman]

Last Feb, returning from Az. , we came through Death Valley, (a low of 260' below sea level), then west through Ridgecrest Ca; then west through Lake Isabella. We gross 19. 7K

From Lake Isabella west, the road suddenly got STEEP, we pulled down to 20 mph and the curves were something else.

After many miles of this, on a hairpin curve, I could read the sign for on comming traffic, it said;

"Trucks use lowest gear 11% grade next 9 miles", and it was another 8 or 10 miles to the top, then similiar grades down the west side. I won't be hauling the fiver over that again.



Vaughn

 

[Ethdee]

Sonora pass.

 

[mbrolin]

Joe,I know what your saying. Our return trip from MM was up 101. Trouble was that the places we were spending the night were not on 101. Another spot we found was between Gilroy and Watsonville on Hwy 152. We saw too many of those kingpin signs on our trip. Course the highlight was when we stayed at the Manchester KOA. That was a 36 mile pleasurable drive pulling the 5er on HWY 1. Didnt bother me so much as the wife. She had the oceanside view and no guard rails. I might add that the wife and I were on a 30% grade this weekend. Went on a 5 1/2 mile hike. That 30 ft rise per 100ft walked sure takes the wind out of you even with the switch backs. Course the wife gets real leery when I mention going on a hike. Must have been that 10 mile hike last fall.

 

[John Berger]

Here's the link on Sonora Pass. I'd like to run this thing someday (with my truck and on foot).



http://www.chainreactionbicycles.com/sonora_pass.htm

 

[Joe G.]

Michael, some of the road on hwy 1 is really beautiful. Once we had a friend visit us who lives in Mattoon, IL. The country around there is dead flat. We took her on a scenic tour of the coast in Mendocino County. It terrified her! Here we were pointing out the beautiful views and she was staring at the ocean down the cliff we were driving along. No guard rail of course.



John, thanks for posting that. That road separates the sissies from the rest.

 

[SteveH]

Originally posted by Ethdee

Sonora pass.

Hi Ethdee,

Did you take this photo? When blown up to 400% the background behind the 26% is obliterated and the letters showing the 26 are much darker and different from the other lettering. I made it show 39% on my machine by editing the numbers and it still looks like a normal photo when viewed in normal size. Mmmmmm. Still not sure. But - maybe.

 

[Power Wagon]

Originally posted by Steve H





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%.

Wyoming Hiway 22, from Jackson to the Idaho Border, where it turns into Idaho 33, goes over Teton Pass. It has several miles of 10% grade in a single long pull. I got stuck behind some guy towing a little aluminum (row?) boat behind an F150 with a Triton. Not only would he not pull over, but at the only straight stretch where you can pass, I met a string of rv's. It stunk so bad that everyone in the car (my station wagon) was pretty much sick by the time we got to the top and he pulled off.

 

[Thomas]

32% grade

I was going to wait until I took a photo of the sign on the steepest road in Los Angeles but decided to post a URL instead. After you click on the link, search the page for Fargo .





Fargo Street in Los Angeles