A roller coaster wheel assembly. The underfriction wheels are on the bottom. The three sets of wheels clamp onto the track.
On roller coaster trains, underfriction, up-lift, or up-stop wheels are a device to keep the train from jumping off the track under intense movement. The design was patented in 1919 by John A. Miller.
| Roller Coaster Descriptions | |
| Basic Elements | Brake Run • Lift Hill • Launch Track • Station |
| Advanced Elements | Bunny Hill • Headchopper • Inversions • Pre-Drop • Tunnel |
| Lift/Launch | Lift Hill (Cable Lift • Lift Chain • Elevator Lift • Ferris Wheel Lift • Thrill Lift • Tilt Section)
Powered Launch (Cable Launch • Counterweight • Friction Wheels • Flywheel • Hydraulic • LIM • LSM) Continuously Powered |
| Technology | On-ride camera • On-ride soundtrack • Train • car • Track • Transfer Track • Underfriction • Wheel |
| Other | POV • Queue Line • Rollback • Theming |