URSA Major Titanium Fatbike Frame

Chumba USA

The Chumba USA URSA Major Titanium Fatbike Frame is Made in the USA!

Custom build quotes available on request.


  • Oversized 44mm head tube fits tapered forks and straight steer forks
  • Headset ZS44 Upper / EC44 Lower
  • Designed for use with 100mm Suspension or Rigid 483mm - 490mm forks
  • 31.6mm Seatpost and 34.9 Seatpost clamp
  • English threaded 100mm bottom bracket
  • Paragon Machine Works sliding dropout inserts can be configured geared, singlespeed or Rohloff


  • Made in USA!
  • Ursa Major frames use the strongest oversized 3AL-2.5V titanium tubes
  • The custom 6AL-4V drive side chainstay yoke has a built in ISCG-05 tab for skid plates
  • The shaped downtube has plenty of room for a Bluto fork in 360 degrees of rotation
  • With 3" - 5.0" Tire compatiblity the Ursa Major offers one of the shortest chainstay lengths out there for both tire sizes, 435mm with a 4.0 tire and <455mm with a 5.0" tire.
  • The frame can be used with 190 Quick release hubs or 197 thru axle hubs, depending on the chosen Paragon Machine Works insert
  • 3 bottle mounts on sizes Large and XL, 2 Bottles on sizes small and med
  • Rear rack mounts