I'll take a guess. Between southern california and central cal there is what is known as "the grapevine". The major highway from north to south that cuts through the angeles national forest. It is not uncommon for truckers to lose their brakes when going down it. It's on the I-5 just past Six Flags Magic Mountain. I drive around it when rv'ing.
I tried to find something on the internet that would answer your question. Couldn't find it there.
But.....It may not be the steepest but I suspect that the average grade over distance from Denver to the Eisenhower tunnel entrance is the winner. From the time you leave Denver going west on I70 until you get to the East Tunnel entrance is a LONG STEEP climb.
For RV's it is miles and miles of 30-45 MPH full throttle driving. Course it depends on your RV. 600 HP Newells don't have much trouble. 1973 Winnie's with a 318 Dodge are really slow.
Don't worry, take your time, use a lower gear on the down hill side and you will have no problems. You must use lower gears in an automatic transmission too. If you are using the brakes on the downhill side shift to 3 or 2 or 1 to keep the speed down. Other than that, enjoy.
I gotta agree with you Larry. The Eisenhower tunnel grade is pretty **** steep on the west side too ... and long. I'd have to rank em this way ... Eisenhower tunnel, Freeway that traverses the Smokey Mts., and then the Grapevine. I'm sure there's others, but my poor ol 32' V10 SeaView by National huffed and puffed over all three of those last summer, Ike definetely got it panting more than the other two. Elevation may be a factor too, Denver is what? 5,000' or so, the Ike tunnel, I believe, is pretty close to 11,000.
We stayed at Breckenridge (in the Ike tunnel neighborhood) for Thanksgiving. That was 11,500'. Talk about altitude sickness! Constant headache, pant like hell climbing stairs, big time insominia, (lay in bed all night long and concentrate on your next breath!)
You are correct. Denver is at 5200 feet which is why it is called the mile high city. The Ike tunnel is 11,100 plus or minus 50 depending on wether you are going east or west. Breckenridge is 9600 feet and the Tiger Run Resort in Breckenridge is one of the best RV parks in the country. You can manage that altitude quite easily and have an enjoyable base from which to xplore the rockies.
Exactly so! We walked around town w/no problem. Conversely my wife and I were completely out of breath when climbing the stairs at the time share. My 33 year old son and his wife who live in Ft. Collins weren't bothered too much. My 30 year old son, who is a fireman in Maui and in excellent shape, was almost as breathless as we were! That tells me there is a little something to be said for acclimination. Next time we are foregoing the view for a little common sense!
I-90 St. Regis Pass Montana * * * * * BAD ( not advised )
hwy 89 between Us 395 in Nevada and little town of
Markleeville, CA * * * * * * BAD ( don't do it period )
Grapevine in California * * semi-BAD
* = no sweat
* * = a little aggravating
* * * = a pain in the caboose
* * * * = Try to avoid if possible
* * * * * = be prepared for over heating of engine when towing
* * * * * * = just flat out don't do it !!!