Vir Fortis is designed to go anywhere, big tyres and big wheels gives a massive amount of traction.
Vir Fortis is not just strong, it is light too: a medium frame weighing in at just 1550g and letting you float over the wildest trails like a cloud. It looks sharp: cables are routed internally to avoid snagging and keep things clean, and a single mounting point on the downtube gives you the option to add a bottle cage.
..Read moreWith a race-winning pedigree, Vir Fortis inspires you to explore the outer boundaries of the trails. Its slackened off geometry gives a characterful ride and is compatible with tyres up to a chunky 4.8". It’s carbon frame and fork gives precise handling and trail bike feel.
It has taken on some of the roughest rides in the wildest terrain, and come out on top.
At a glance
- Fat, light, and comfy for wilderness exploration
- Frame: Sonder Vir Fortis, high grade T700 carbon
- Groupset: SRAM GX Eagle / 1 x 12 / 10-50
- Brakes: SRAM Guide R
- Fork: Vir Fortis, high grade T700 carbon
- Seatpost: Love Mud Membar, 31.6 mm
- Wheelset: Love Mud Hurlyburly
- Tyres: Schwalbe Jumbo Jim / 26 / 4
Hand laid carbon fibre frame and fork
Using Toray’s highest grade of carbon, T700, this frame is manufactured in a clinical environment to the highest standards. The result is an extremely strong, lightweight frame that is a blast to ride! Guaranteed for 5 years

Trail bike inspired geometry
The Vir Fortis take fun to the next level by slackening the bike out a bit, giving it a more relaxed, playful character. With natural air suspension from the enormous tyre volume Vir Fortis is ready to roll over all terrains.

Internally tapered head tube
Who would choose to be a head tube? You might as well step into the ring with Mike Tyson. It is a critical junction point where forces are distributed around the frame and steering precision is won or lost. Vir Fortis uses a fully integrated internal headset and a fork with a tapered carbon steerer tube to make sure you hold your line over broken ground.

Disk brake compatible
Once rolling you will be surprised by how you can carry your momentum which is why you are going to be thankful for the stopping power of disc brakes. The Vir Fortis carbon frame is fully compatible with disc brakes.

High spec builds
If you’ve a dream build in mind, please get in touch and we’ll do our best to source the parts you want.

Build | Vir Fortis GX Eagle |
---|---|
Frameset | |
Frame: | Sonder Vir Fortis Frame |
Fork: | Sonder Vir Fortis Fork |
Shock: | |
Headset: | FSA Orbit C-40-ACB Headset / 7.8mm Spacer |
Seat Clamp: | Love Mud Silent Partner / 34.9mm |
Group Set | |
Brake Front: | Sram G2 R / 950mm |
Brake Rear: | Sram G2 R / 2000mm |
Rotor Front: | Avid Centreline Rotor / 180mm |
Rotor Rear: | Avid Centreline Rotor / 160mm |
Rear Mech: | SRAM GX Eagle Rear Derailleur / 12 / Long |
Rear Shifter: | SRAM GX Eagle Trigger Shifter |
Chainset: | SRAM GX Eagle Fat Crankset / 175mm / 30T |
Bottom Bracket: | SRAM Bottom Bracket / Fat |
Chain: | SRAM GX Eagle Chain / 120 Links |
Cassette: | SRAM XG1275 Eagle Cassette / 12 / 10-50 |
Finishing Kit | |
Stem: | Love Mud Piskie Stem / 31.8mm / 35mm |
Seatpost: | Sonder Membar / 31.6mm / 400mm |
Saddle: | Sonder Abode / Black |
Tape/Grips: | WTB Wafel / Black |
Handlebar: | Sonder Aspect Riser |
Wheelset | |
Wheels: | Love Mud Hurlyburly Wheelset |
Front Tyre: | Schwalbe Jumbo Jim / 26inch / 4 |
Rear Tyre: | Schwalbe Jumbo Jim / 26inch / 4 |
Tubes: | Schwalbe Fat Inner Tube / 26inch / 3.5-4.8 |
Weight | |
Frame: | TBC |
Built: | TBC |
Pedals not included with full builds |
Sizing
It is important to get the right size bike, if the bike fits it will be faster, more comfortable and easier to handle. You can also take into consideration the standover height to ensure you pick a bike that will be a good fit. If you measure your inside leg and ensure there is a minimum of an inch from the toptube to your crotch this will give you enough seatpost adjustment to find your optimum saddle height. Generally we recommend: Small Riders between 5ft 2in and 5ft 7in Medium Riders between 5ft 6in and 5ft 10in Large Riders between 5ft 9in and 6ft 2in
Size | Small | Medium | Large |
---|---|---|---|
ST - Seat tube | 406 | 457 | 505 |
TT - Top tube | 580 | 605 | 625 |
HT - Head tube | 100 | 110 | 130 |
HA - Head angle | 68.5 | 68.5 | 68.5 |
SA - Seat angle | 73.5 | 73 | 73 |
CS - Chainstay | 445 | 445 | 445 |
BB - BB drop | 60 | 60 | 60 |
FO - Fork offset | 45 | 45 | 45 |
WB - Wheelbase | 1103 | 1123 | 1145 |
SO - Stand over | |||
RE - Reach | 406 | 423 | 437 |
SK - Stack | 586 | 595 | 614 |
Frame Weight: S: TBC; M: TBC; L: TBC |
Fork Weight - uncut: TBC |
Toray T700 carbon fibre |
Headset: IS42/28.6 | IS52/40 |
Seat post: 31.6 mm |
Seat tube OD: 34.9 mm |
100mm BSA BB shell |