The 2021 Sentinel is Transition’s new all-mountain bike, enduro bike, trail bike, call-it-what-you-want bike. The new Sentinel gets an additional 10mm travel outback bringing it up to 150mm, paired with a 160mm short offset fork to round out Transition’s Speed Balanced Geometry. This 29″ full suspension bike is carbon only, for now at least. We have all the tech and geometry details on the 2021 Transition Sentinel right here.

2021 Transition Sentinel

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  • Intended Use: All-Mountain/Enduro/Trail/Everything
  • Wheel size: 29″
  • Suspension Travel: 150mm/160mm
  • Head Angle: 63.6°
  • Effective Seat Angle: ~77°
  • Frame: Full carbon, 148mm boost spacing
  • Claimed frame weight w/shock: 3.2 kgs

For 2021, the Transition Sentinel is a little slacker in the head tube at 63.6°. It now has an actual seat tube angle of 70.8°, but the effective angle is still a healthy 77.5° in medium. As you might expect, this effective seat tube angle slackens off to 76.4° in XL and, wait for it… 75.9° in XXL!

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For 2021, Transition have seen fit to add an XXL frame size to the lineup with a generous reach of 521mm and a seat tube length of 490mm. The small Sentinel actually loses 5mm of reach for 2021, bringing it down to 420mm. The medium reach remains at 450mm, while the large and extra large frames gain 1mm, bringing them up to 476mm and 501mm, respectively. The chainstay length has increased by 5mm to 440mm, consistent across the frame sizes. Transition’s Sam Burkhardt says this gives the bike better balance and more front wheel traction.

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Notably, the seat tube of the new Transition Sentinel is 10mm shorter across the frame sizes. It is also straightened up to provide a lot more seatpost insertion length to give riders more room to run a super long dropper. The small frame comes with an impressive 150mm drop, the medium gets a 180mm while the L-XXL frames get 210mm droppers. Tire clearance has also increased to 2.6″, though you might want to be a little more reserved in muddy conditions and run at 2.4″ or 2.5″.

Party time leverage curves…

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In designing the new Sentinel, Transition wanted to improve small bump sensitivity and the bottom out control. To achieve that, the initial leverage curve is higher with a lot more progression through the travel with a linear change. This gives rise to what Transition say is a really consistent ride feel, ramping up evenly through the travel. Increased mid-stroke support allows the bike to recover faster with successive big hits. They say its 24% overall progression works well with both air and coil shocks. The stock Sentinel features 150mm rear wheel travel spec’d with a 62.5mm stroke shock, but you can run it at 140mm with a 57.5mm stroke shock.

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The Transition Sentinel features a full carbon frame made from Japanese Toray fiber with a tailored blend of 24T and 30T materials optimized for the right balance of frame stiffness, strength, and impact toughness. Transition’s unique latex coated EPS molding process allows for sharper frame lines and tighter edge radius control with maximum strength to weight ratio and less wasted material.

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The full carbon frame features 148mm boost dropout spacing, a 44mm/56mm press-in headset and a threaded bottom bracket. Pivots are serviced by Enduro Max sealed bearings with bearing shields on the main pivot. The frame is protected by a molded rubber chainstay protector and a seatstay and downtube protector. Rear brake cabling is externally routed while the derailleur cable routing is fully guided internally through the downtube and chainstay. The front triangle features water bottle bosses on the downtube and an accessory mount on the underside of the top tube.

2021 Transition Sentinel 29er Geometry

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Availability

The 2021 Transition Sentinel will be available as a frame only with a FOX Float X2 Performance Elite shock, in Ti Grey or Loam Gold colorways. It will also be available several complete models including SRAM X01, GX and NX groupset builds. Head to the Transition Bikes website for full details on pricing and availability.

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TransitionBikes.com

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