How steep was it?

[Desert_Captain]

Here is a shot I took last fall while visiting our friends in Nevada City, (northern California gold country). It was taken just outside of Nevada City/Grass Valley. Fortunately this steep section of the road is only a little more than a quarter of a mile. In the winter it is totally impassable even with 4 X 4 and necessitates a serious detour. I've seen my share of steep roads down here in Arizona, 8% to 10% is not unusual but this one takes the prize. :E

[JiminDenver]

There is a stretch going up to Jefferson Lake outside of Jefferson Colorado that is extreme. We took the Cree up it with out 75 E 100 with a 300 inline 6. Going up was one thing, coming down was another. The 2500 lb Cree had no brakes and the van had drums. Luckily it's a shorter drive.

Our first trip with this trailer we decided to take the short route between Horse Tooth and Red Feathers. It may have been shorter but the speeds were much slower. The paved was 2 lane with 30-50 mph curves. The dirt was a logging road that at times had the Expy down to 15 mph in first and had hairpins at 10-20 mph warnings. There was beautiful scenery coming into the area from the backside, we even saw a moose. On the way home we took the long way, it took much less time.

[Desert_Captain]

OP here: Yes, I was just trying to share an interesting experience. Wasn't looking for a remedial math class. I guess it is impossible to post anything here without someone wanting to argue. :S

The folks at Cal Trans have been engineering the roads in California for quite some time and if they post a sign that says "31%" trust me it is a 31% grade (and yes that is 31' of drop for every 100" of horizontal travel. If anyone out there knows more than the engineers at Cal Trans I am sure they would love to hear from you. Break that down anyway you like, it is a very freaking steep road.

In conclusion all I can say is "lighten up", downshift and please don't ride your brakes. :R

[roy67ss]

smkettner wrote:
Percent means parts of 100. 31% is 31 foot rise over 100 foot forward distance.

BINGO

And the winner is ....... smettner

I am a highway project manager and have been building highways since 1970. The percent signs mean exactly what smettner said. 7% = 7x vertical rise per 100x horizontal run.

No ifs ands or buts!

[AH64ID]

ReneeG wrote:
Usually the percentage of incline is relative to the terrain and not that bad.

Huh? Percent slope is relative to only one thing, 45 degrees. At 45 degrees you go up/down 1 foot for every 1 foot horizontal.

There is nothing relative to terrain.

The steepest paved road I have towed on was over 20%, and I have been no dirt that was steeper but I am not sure how much.

[kknowlton]

I think the OP was just trying to make the point it was a freakin' steep hill and beware. Then it turned into math class.

:B

[noe-place]

Right Shadow4, I think the OP was just trying to make the point it was a freakin' steep hill and beware. Then it turned into math class.

[shadows4]

dave54 wrote:

pappcam wrote:

Fishinghat wrote:
The grade in degrees is normally a percentage of a 45 degree angle. So, 31% would be about 16 degrees. That's still a very steep hill, but "doable". A 31 degree hill would be about double in slope and I'm not sure a typical wheeled vehicle could navigate it.

On the other hand, I've never been there and it could be much different than what I think the sign implies.

I'm thinking the sign maker confused degrees with percentage.

Percentage slopes actually are a percentage of 45 degrees so that is about a 16-17 degree slope. The sign does display percent and not degrees so the sign maker is correct.

?????

Percent slope is feet rise for a 100 foot horizontal distance. (or meters, or yards, et al, as long as the unit of measure is the same for both).

A 45 degree angle is a 100% slope. 31% is a 17.22 degrees.
To convert % slope to angle use the inverse tangent function on any calculator with trig functions.

I wouldn't know an inverse tangent if I saw one! All you had to say is it's friggin steep!!! LOL

[dave54]

pappcam wrote:

Fishinghat wrote:
The grade in degrees is normally a percentage of a 45 degree angle. So, 31% would be about 16 degrees. That's still a very steep hill, but "doable". A 31 degree hill would be about double in slope and I'm not sure a typical wheeled vehicle could navigate it.

On the other hand, I've never been there and it could be much different than what I think the sign implies.

I'm thinking the sign maker confused degrees with percentage.

Percentage slopes actually are a percentage of 45 degrees so that is about a 16-17 degree slope. The sign does display percent and not degrees so the sign maker is correct.

?????

Percent slope is feet rise for a 100 foot horizontal distance. (or meters, or yards, et al, as long as the unit of measure is the same for both).

A 45 degree angle is a 100% slope. 31% is a 17.22 degrees.
To convert % slope to angle use the inverse tangent function on any calculator with trig functions.

[time2roll]

Percent means parts of 100. 31% is 31 foot rise over 100 foot forward distance.

[pappcam]

Fishinghat wrote:
The grade in degrees is normally a percentage of a 45 degree angle. So, 31% would be about 16 degrees. That's still a very steep hill, but "doable". A 31 degree hill would be about double in slope and I'm not sure a typical wheeled vehicle could navigate it.

On the other hand, I've never been there and it could be much different than what I think the sign implies.

I'm thinking the sign maker confused degrees with percentage.

Percentage slopes actually are a percentage of 45 degrees so that is about a 16-17 degree slope. The sign does display percent and not degrees so the sign maker is correct.

[Gale_Hawkins]

BTPO1 wrote:

pnichols wrote:
I wonder how steep Old Priest Grade is in CA?

We went up that once in our 3-speed column shift Dodge 3/4 ton camper van and it barely could pull it in first gear, as only 3-speed manual shift gearing results in a tall first gear - plus we had over-diameter sized tires on it which made all of it's gear ratios even taller. (We got 18 MPG out of it's 318 V8 on camping trips, however ... this was using 1972 V8 engine technology.)

I found an article on Old Priest Grade and it mentions that it is a 22 degree slope. BTW last time we were there RVs' were prohibited from using it, had to use CA120, which was full of switchbacks and very slow but beautiful.

Thanks for that info on Old Priest Grade. In Sept of 2011 we took it up by accident. As soon as I got on it I saw the sign of NO RV's so I said I will just turn around our old 32' MH on a P30 chassis and cut the dash air per the sign.

Well there were not places to turn around. At WOT we were making about 15 MPH. I did not panic too bad because I was too busy watching my nose and tail. I had to be careful on the curves I did not slap the rock wall or a vehicle going down depending on the shape of the curve and that nose was not too much on the other side of the road at same time. I think it was about 4 miles and I was very glad to see the top sign at the top.

The temp gauge kissed the red zone but never entered it. I am not sure if the kids ever realized the danger we were in. Thankfully the 454 TBI never missed a lick but had we lost one plug or plug wire we would have been stuck at best. I have watched people doing it on Youtube and it was not fun for me to watch.

It was my worse grade experience on the 8000 run to the Pacific by way of Yellowstone and back by way of the Grand Canyon.

[BTPO1]

pnichols wrote:
I wonder how steep Old Priest Grade is in CA?

We went up that once in our 3-speed column shift Dodge 3/4 ton camper van and it barely could pull it in first gear, as only 3-speed manual shift gearing results in a tall first gear - plus we had over-diameter sized tires on it which made all of it's gear ratios even taller. (We got 18 MPG out of it's 318 V8 on camping trips, however ... this was using 1972 V8 engine technology.)

I found an article on Old Priest Grade and it mentions that it is a 22 degree slope. BTW last time we were there RVs' were prohibited from using it, had to use CA120, which was full of switchbacks and very slow but beautiful.

[Veebyes]

31% is nasty. Very close to a 1/3 grade. They are rare. I England grades are expressed as a 1/?. A 1/7 grade is not uncommon. A 1/5 or 20% can be found in places like the Lake District.

I have a short piece of unpaved roadway/track on my property that must be around the 35% mark. You get a good run at it & don't stop.

[jasult]

you didn't stop half way and take pics :B

[pnichols]

Thanks for that interesting "Steep Streets" link above!

I notice that at least one of those steep roads is restricted to 4X4 vehicles, only ... and that the reason seems to be so that low-range is available (and required) due to the steepness of the grade.

FWIW, our GMC 4X4 Z71 offroad pickup has a non-stock front axle engagement system setup I installed so that the truck can be in low-range, but still only be in rear wheel drive if desired for special situations. We use this 4X4 drive setting when pulling up very steep roads that are also paved. This provides extreme pulling power for towing trailers, etc. when on very steep paved roads ... which could otherwise ruin gears due to 4X4 low range drive system wrap-up on hard surfaces.