In the mid 1970's to took my 1965 Corsa convert up Mount Equinox (3,840 ft, 14%+ grade and 5.2 miles). The Corsa pulled the grade easily in 2nd gear, in about 15 minutes. After about 15 minutes at the top, we started down among the carnage. About 1 in 4 cars were overheating at or near the top. About halfway down, there was the smell of burning brakes on every turn out. We passed two wreckers on the way up. Now 50 years later with many less manual transmissions cars, SUVs and motor homes; I doubt things have changed.
If you do go up, be sure you come down in 1st gear and stop at every turnout to let the line of cars behind you go by. You will pass them on the turnouts near the bottom. Do not attempt to tow anything. As others have said the Broadmoor, Manitou and Pikes Peak cog & rack Railway is well worth the money. Take a jacket as it is always cool and windy at the top. I have seen 10 inches of snow on the ground in late August.