Grand Ridge is both an oldie and a new trail: while new residential development wiped out some of the trails we rode in the past, a new trail system has been under development by King County Parks and the WTA. (Check out wta.org for work parties.) You access it the same way as ever: by climbing up from I-90. The trail can also be accessed from the top of the Issaquah Highlands development.
The main trail winds north across Grand Ridge towards Duthie Hill Park.
This is a great XC work out, with great climbing practice. Plus, it can be linked with trails on the south side of I-90 to create longer loops. This trail connects with Duthie Hill Bike Park and 1 short mile of road riding to continue up to Soaring Eagle for a suburban epic.
The climb from I-90 up to the plateau is a grunt, but not too long. When coming from Duthie Hill, the long climb up to Grand Ridge Drive is even more of a grunt, and is pretty darn hard to clean on a single speed. With gears, it's still a fairly physical ride.
THIS TRAIL IS NOT AN OFF LEASH AREA.
The south end of the trail starts on the RR grade on the north side of I 90 between Exits 18 and 20, and the north end of the trail starts across from the south side of Duthie Hill park, on Issaquah Fall City Road.
For the south end, the best place to park is on Sunset way (I-90 Exit 18), just as you drive down into downtown Issaquah. The parking lot is on either side at the bottom of the ramp on Sunset Way. From the parking lot head north over I-90 on paved trail which becomes the gravel RR grade that heads east along the north side of I-90. After a mile or so you reach the first Grand Ridge trail that heads up the hill to the left.
For the north end, the best place to park is the Duthie Hill parking lot. The address is 26150 SE Issaquah-Fall City Rd, Issaquah WA 98029. Click here for a Google Map to the lot: http://goo.gl/maps/V1T0C. It's on Issaquah-Fall City Road just west Issaquah Fall City Road and Duthie Hill Road intersection.
There is also access to the Grand Ridge trail from two points in the Issaquah Highlands Central Park, one from the powerlines by the soccer fields, and another from the tennis courts. If you park by the tennis courts, ride south along the retention pond and find the trail at the south end. If you ride down the road under the power lines, just past the soccer fields you will find the trail on your left.
A third option for parking is at High Point (I-90 Exit 20), on the north side of I-90. But there have been a number of break ins there, so this lot is best avoided.
You can also join the trail from the Issaquah Highlands via Harrison Way and then Grand Ridge Drive to where it intersects the trail. DO NOT park on Grand Ridge Drive.