Crafton is the final climbing segment and longest dirt portion of the 100km route. It comes along at the 71st kilometer and requires you to climb 5km of buffed single track. This is worth pushing for, as the trails and views are both amazing and the accomplishment you'll get from this will be worth it. If you can make it here, the rest is (mostly) all down hill. Still 20km more to go, but downhill nonetheless!
For those in the know or who want to look at it on the Google, the route is first climbing climbing Grape St. Trail (follow the singletrack, not the direct downhill). Then taking the construction site single track over to Yikes! trail and descending to the paved access road at the bottom. Once there, climbing back up 38 Special to the fire road is where you earn your bragging rights! This is one of the best trails around, with unencumbered views of the Santa Ana River watershed. Again, buffed singletrack, with several switchback sections to keep the grade reasonable. It's SoCal hardpan with slick ball-bearing like sand on top. There might be a dab or two.
At the top of 38 Special, you'll made the Crafton fire road. You can really open it up on until you get to Thunderbird Trail. That's a quick right and minor uphills, then a GREAT downhill singletrack! Descend down that, then climb half-way back up Three Hawks Trail to the college.
Whew, got all that? Crafton Hills College has water, but restrooms are closed on the weekend.
Exit the college onto Sand Canyon at the light (fast traffic here!). Turn left on Sand Canon and go for no more than 200 meters, then right at the cable gate into the Crafton Hills Conservancy property and back onto the 50km route. The 50km does not need to ride to Sand Canyon, but instead picks up the trail through the housing development (50K Cutoff on map below).
This also serves as a bailout option for the 100km. If you are planning on the 100, and just having a bad day, simply follow the 50km route at this point and it's still going to be a good ride!