What does 5% or 6% or x% downgrade for next 6 miles mean?

[paesan]

I had different responses from different people. some people say that you are going down a 5% downhill and some say you are going down 5% of some equation involving miles divided by feet or something. Please tell me the true meaning so I can at least act like I know what I am talking about.

 

[milehiscott]

The answer is yes

Paesan,

The sign means that you are going down a 5% grade (downhill). In real life terms, that means for every 100' forward you travel, you go down 5' (remember all of the algebra that we all swore that we would never use?). The higher the %, the steeper the hill.

I know it doesn't sound very steep, but you will accelerate alot on 6% hills and it gets hard to stop.

Sorry, I don't remember the math to convert it into degrees of incline (like on a protractor).



If you don't like the math, just remember, anything over 6% is a big hill. Anything over 10% = :--) :{

 

[Joe G.]

Sonora Pass --- 26%!!!!!

 

[JWhitcomb]

Just to keep things in proper perspective, Sonora Pass is only that steep for a short while. We don't want to scare the bejeepers out of the flat landers to our East. And just to make things interesting the rest of the pass is still plenty steep.

 

[Thomas]

The percent-of-grade, when expressed as a decimal, is the tangent of the angle of the road with respect to horizontal.



A 6% grade makes an angle of slightly more than 3. 43 degrees with a horizontal plane.

 

[Doubleclutch]

I think Thomas just said... your brakes are going to get hot.

 

[Ron Bissett]

When you see this sign on top of hill most time it will have a truck in black shown and a cautsion trucks use lower gear . If you have a exhaust brake and its not on its time to flip the switch to keep the brakes from heating up . and if you don't have one to think of how you will keep control of your truck and or trailer , camper , heavy load . Slow down before starting down . Ron Bissett in LOUISVILLE KYOo. Oo. Oo.

 

[Boldt's Wagon]

With 18,000 lb GCVW, 3. 54 gears and auto:



5% means 3rd gear;

6% means 2nd gear at 55 mph:

7% means 2nd gear plus turn on air cond at 50 mph;

8% means 1st gear at 30-35 mph:

9% means 1st gear plus air conditioner at 25-30 mph:

12% means all of the above plus "OH Momma, why didnt I buy that 4x4 with low range"

 

[Jim Fulmer]

South of Moab, Utah catch hwy 46 to La Sal to Paradox, Colorado(nice valley). This is no where USA but a way cool drive, the pass is a 9% down grade with 15 MPH switch backs. I topped the hill at 35 MPH, went in to 2nd manual and rode that all the way down... ... ... No trailer, just my 6300 LB ride! That was Friday 12 July.



Jim

 

[sheldon]

Remember, a 100% grade is a 45 degree angle. Not straight up as many people have tried to tell me. It is always best to be slowed down before going down the hill than it is to try to slow down after heading down. That rule has kept me out of trouble well driving trucks with an inoperable jake. You can get down hills safely without an exhaust brake but you have to think ahead and stop to let the brakes cool at the first sign of sponginess. Besides, you get to enjoy the scenery more.

 

['956Wheel]

The percent of grade is expressed in a distance X elevation gain/loss, when trully it would be more realistic to express it in spinkter tension, a method understood by all.



Mike

 

[hammersley]

7% Max

If memory serves me - 7% is the MAX design allowed on the Eisenhower Interstate System.

 

[Doubleclutch]

Hey Boldt- good to see others utilize the "air brake" method of descent! A little load from the A/C does make a small difference. "Heat up/ Cool down".

 

[plntmgr]

We just completed 12. 5K from SoCal to Brownsville TX,Charleston SC, Atl, GA, Nashville TN,(I-24from Chat. TN. ),Flagstaff AZ. , Shasta,Ca, Ukiah(Hwy 20 west thru Clear Lake) to LA. We tow a 14K 32' Alpenlite(20,400 combined weight) and no exhaust brake. Dunnrite Trans. (ElMonte, Ca)reworked my transmission. We crawled down 6 % grades with caution(scruples or common sense) without the first hint of a problem. We had no brake fade or overspeed. I thank Tony every time we come to a grade. It was the best and most confident 6 months of my life. Enjoying Retirement.





'98. 5 2500, Auto, 3:54, STOCK, 60 Gal tank, Air Bags(Camping World) Reworked transmission( by Dunnrite Trans. )



')01 32' Alpenlite 32' Double slider