referring to fig1 the invention is shown including a u - shaped frame 12 rigidly mounted to a conventional skate boot 10 . the frame 12 may be manufactured from reasonably rigid materials such as lightweight metals , synthetic thermoplastics , thermosetting polymers and co - polymers , polyolefins , polyurethanes , phenolics and the like . the frame 12 has a plurality of throughbores 14 for receiving axles 16 . referring also to fig2 each axle 16 receives a set of bearings 18 . the inner races 20 of the bearings 18 may frictionally engage an axle 16 or maintain close tolerances therewith . the axle 16 threadingly interengages a nut 17 . counterbores 21 in the hub 22 receive the outer races 24 of each bearing 18 . the counterbores 21 may frictionally engage each outer race 24 or maintain close tolerances therewith . a spacer 26 is interposed between each bearing 18 and the frame 12 . each spacer 26 protects its constituent bearing 18 from contamination . each spacer 26 also compels the inner race 20 of its concomitant bearing 18 axially against the hub 22 such that the outer race 24 is urged against the shoulder 28 of the hub 22 . the hub 22 is intended to be rugged to endure the punishing terrain of backcountry trails . further , the hub 22 is dimensioned and configured to maximize axial distance between the bearings 18 . increased bearing spacing will increase bearing life because the bearings 18 will sustain largely normal forces rather than non - normal forces which distort the configurations of the bearings 18 . increased bearing spacing will also permit the hub 22 and the tire 32 to define a large volume 23 containing fluid . each hub 22 includes a lip 30 for receiving the lip 34 of a tire 32 . lips 30 and 34 sealingly interengage . a throughbore 36 in each hub 22 receives a valve 38 for introducing fluid or pressurized air into volume 23 . the valve 38 may be of the presta -, schraeder - or pin - receiving - type . referring again to fig1 the three tires 32 is intended to have a low profile for keeping the skater &# 39 ; s center of gravity as low as possible . the tire 32 is also intended to have a wide tread for exceptional traction on backcountry trails . the hub 22 and tire 32 are intended to define a large volume 23 for a comfortable ride over rough terrain . the invention also includes a brake 50 for arresting the skater &# 39 ; s motion . the brake 50 comprises an elongated member 52 including an attached durable pad 54 . the member 52 may be molded integral with or fixed to the frame 12 . the pad 54 may be attached to the member 52 with threaded fasteners ( not shown ), but may be attached by any means having similar capability . referring to fig3 the invention is shown including scrapers 34 . while skating on backcountry trails , skaters will likely encounter mud , rocks and other debris . the scrapers 34 having a smooth arcuate surface 35 are located proximate each tire 32 for cleaning the tires or preventing debris from binding the tire 32 against the frame 12 . each scraper 34 may include a threaded shaft 46 at each end of the scraper 34 , each of which being received in one of the slots 48 in the frame 12 . each scraper 34 may be adjusted in the slots 48 , radially with respect to the tire 32 , and fixed with wing nuts 40 . referring to fig4 the scrapers 34 may also be biased against the frame 12 and toward the tire 32 with a spring 42 at each end of the scraper . biasing the scraper 34 is purposed at maintaining continuous contact between the scraper 34 and the tire 32 . the spring 42 mounts to a boss 44 and the shaft 46 of the scraper 34 . the present invention is not intended to be limited to the embodiments described above , but to encompass any and all embodiments within the scope of the following claims .