|Lots of switchbacks on the Pines to Palms Highway|
To get a good look at the climbing required, check out the route profiles at California Bike Rides. The first day is the shortest, only 50 miles, but it looks like it's uphill the whole day. You start around sea level, and end up at about 4,000 feet. There are two category 3 climbs and one category 4. Day three is the longest (102 miles), but after mile 15 it's downhill for the next ten miles. The toughest climb of the tour is at the start of day four. It's a category 1 climb, with nearly 4,000 feet of climbing in the first 15 miles. After that, there are three more category 4 climbs before the day finishes with around twenty miles of downhill.
Below is a video that shows some of the 2010 edition of the ride. At one point during the third day, you can see a road sign that indicates they are going down an 8% grade.