The Tapeworm, Mr DNA, Crop Circles, Parasite Trails

View of Tapeworm Trail system

Overall: 5

Aerobic: 4

Technical: 5

Steepness: 2

Flow: 9

Singletrack: 100%

A study in flow, Tapeworm can show riders how to get a good way.




Avg: 4.5mi



Elevation Change

Avg Ascent:600'

Ascent Incline



Avg: 1.5hr





The endless hairpin curves require some attention, and soon everything else drops away as riders work first gear and their brakes to avoid slow motion crashes.

First came Mr DNA, then the eponymous Tapeworm in 1997, followed by Crop Circles in 1998, then finally the New Parasite.

Like the McKenzie River Trail, extensive use has worn this carefully laid out trail system, but it's still a lot of fun.

Tapeworm is not a destination trail, but it is a must-ride (at least once) for any Northwest rider.

The 3.5 turn, double-spiral Crop Circles can be seen while approaching the Renton airport.

New Parasite has many log features, adding to the stunts built on The Tapeworm.

The trail system was designed to be one-way.

Riding the other way will damage the trail, and the other riders may damage you as well, so it's not recommended.

Be sure to not leave valuables in your car while riding.

Directions: See Map. View Larger Map. No Map?.

The Tapeworm Trail Topo Map

Loop Directions

tapeworm - the good kind

Tapeworm Area Topo Map

  • TH: From Phillip Arnold Park, ride Beacon Way to the power lines, then turn in at the concrete barriers and ride .3mi to the trail on the left.
  • .6mi: There are several trails to the left, from the dirt road, so if you miss the first trail then take the next one. All lead to Mr DNA, near the substation.
  • .9mi: Back near the substation, having finished Mr DNA, turn away from the substation again, starting Crop Circles. This trail begins with a straight ride to the far end, then a series of 'tapewormy' switchbacks, approaching the substation before turning back again and coiling into and back out of the Crop Circles. Those not having fun yet are trying too hard. Now ride over to The Tapeworm.
  • 1.9mi: At the entrance to The Tapeworm, note the 'Begin' sign. No directions required. Just be ready for a lot of short climbs and plenty of stunts to ride if desired.
  • 3.4mi: Having completed The Tapeworm, ride over to New Parasite and practice clearing logs, then ride back to the park.



Best Area Guide


Trail Rankings

Ranking consistently applied to all of the listed trails.

  • Overall Rating: Ride quality and challenge
  • Aerobic: Ascent challenge
  • Technical Difficulty: Terrain challenge
  • Steepness: Average incline
  • Flow: Uninterrupted riding
  • Elevation Change: Total elevation gain
  • Ride Difficulty: Terrain challenge






Forums can be used to organize rides, announce events, and comment publicly (or privately).

Comments marked private will only be seen by your friends (and the moderator).

The Terms of Use page lists the public posting guidelines. Please keep it clean.

Although forums are monitored, the Comments page is a faster way to get page errors and information corrected.