Change Reaction is an expert-level one-way DH trail on the upper mountain of Park City. The trail runs from the middle of Charlie's 9K down to Webster Road just above the Midmountain Trail. It's 1.1 miles long with 575 feet of elevation loss. With a starting point of 9250 feet elevation, the expected riding season will be July through October.
Most riders will start from the big parking area on the Guardsman Road in Bonanza Flat, 1/2 mile west of Empire Pass. Go uphill across the road to the singletrack, which will take you east and uphill 0.7 miles to meet 9K where it branches away from the ridge doubletrack.
To return to the these upper mountain trailheads, there are several options. Most will require that you descend from Charlie's 9K to Midmountain, then select a climbing trail such as Corvair, Tour des Suds, or Boulder to the east. To the west, you can take Tommy's Two Step, Three Candles, Keystone, and Shadow Lake to the 9K trail.
The trail can be reached through the Empire Pass parking area. Take the doubletrack west past the top of Corvair, then turn right onto 9K 0.1 miles after leaving the parking area. This is a fairly small parking lot, so on weekends you'll probably need to find another starting spot. It's 2.5 miles from Empire to Change Reaction.
From the lower mountain
All routes to Change Reaction must climb to Charlie's 9K trail. First, get to the Midmountain Trail. The most direct routes from town are Jenny's and Mother Urban. If you're starting from Deer Valley, simply ride west on Midmountain.
Apex: Take upper CMG to Thaynes Road to Apex and climb to 9K.
Fat Lip route: At Three Candles, go left on Keystone. Transfer to Fat Lip. At McConkey Road, connect to Stiff Upper Lip. At 9K, go right 0.5 miles.
Corvair: Climb directly to Empire Pass from Midmountain and head west to 9K.
Boulder: Climb Boulder but fork right onto Moosebones. At the road, connect to Upper Corvair for the climb to Empire Pass and 9K.
Although most of the descent is in deep forest, you'll cross a couple of large ski-slope meadows. Near one of these, you'll cross over Fat Lip.
As you approach the bottom, the trail has a more raw character, with loose dirt on rooty steep pitches.
Quick POV scouting Change Reaction when it first opened...
Empire Pass: As you enter Park City, follow the signs for Deer Valley and Guardsman Road. Get on Bonanza Drive heading south uphill. At the roundabout, turn toward Empire Canyon (SR 224). Stay on that road for about 3.5 miles. Go through the roundabout in front of Empire Canyon Lodge and head uphill on 224. When the road reaches Empire Pass, turn right into the parking area at the top of the mountain. The 9K trail is reached via a short connector on the ridgeline.
Pine Creek/Bonanza Flat trailhead: On the Guardsman Road about 1/2 mile west of Empire Pass, turn downhill into the trailhead. The connector to the 9K trail is across the road from parking. It's around 0.7 miles up to the 9K trail, which you'll find on the opposite side of a doubletrack on the ridge.
Toilet at Empire Pass and Guardsman Road trailheads.
When driving up Empire Canyon as above there's parking just uphill from the Midmountain Trail. Just after the road makes a turn to the right, there's parking on the left side of the road. Park here if you'll start your ride on the Midmountain Trail, then coast down to the trail, which is just above the turn in the road.
GPS tracks (right-click and "save as...")
Park City trails (over 150 tracks)
Change Reaction area trails
Change Reaction LAPS route