Spire Alloy Eagle 70

Introduced in 2021, the Transition Spire is a long-travel 29er built for aggressive enduro riding and steep, high-speed descents. With 170mm of suspension travel front and rear, it sits at the burliest end of Transition’s single-crown lineup. The frame is available in both carbon fiber and aluminum, utilizing the brand's GiddyUp four-bar linkage to balance big-hit absorption with a supportive pedaling platform. While it shares visual DNA with the rest of the Transition family, the Spire is distinctly shaped for riders who prioritize downhill stability over low-speed agility. It is a bike designed for enduro racing, bike park laps, and rugged backcountry lines where carrying momentum is essential. Despite its downhill-adjacent intentions, the platform maintains enough versatility to handle long transition climbs, making it a practical option for riders who earn their descents but refuse to compromise when the trail points down.

$4,199

Image pending

Build

Size

Stack	619mm
Reach	460mm
Top tube	577mm
Headtube length	100mm
Seat tube length	390mm

Fit and geometry

The Spire’s geometry is defined by its length and slack angles, creating a highly stable platform that places the rider squarely between the wheels. A flip-chip at the lower shock mount offers high and low settings, adjusting the head tube angle between 63 and 62.5 degrees while altering the bottom bracket height by 7mm. In either setting, the front end is exceptionally slack, which pushes the front wheel far ahead to resist tucking on steep descents.

To balance this long front center, Transition utilizes size-specific chainstays. Small, medium, and large frames feature a 446mm rear center, while the XL and XXL sizes grow to 452mm, helping taller riders maintain front-wheel traction. The effective seat tube angle is notably steep, measuring around 78 to 79 degrees depending on saddle height and frame size. This upright posture keeps the rider’s weight forward during seated climbs, counteracting the slack head angle and preventing the steering from feeling overly light. Across the size run, reach numbers are generous, stretching from 430mm on the small up to 535mm on the XXL, paired with short 35mm or 40mm stems to keep steering inputs direct.

Full specs

Frameset

Frame

Transition Spire Alloy 170mm

Fork

RockShox Domain Gold RC, 170mm

Rear shock

RockShox Super Deluxe Base, 205x65mm

Groupset

Shift levers

SRAM Eagle 70 MMX

Rear derailleur

SRAM Eagle 70

Cassette

SRAM XS-1270, 12-speed, 10-52T

Chain

SRAM Eagle 70

Crankset

SRAM Eagle 70 DUB, 30T, 165mm

Bottom bracket

SRAM DUB (threaded, BSA 73mm)

Front brake

SRAM Maven Base

Rear brake

SRAM Maven Base

Front rotor

SRAM Centerline, 200mm

Rear rotor

SRAM Centerline, 200mm

Wheelset

Front wheel

WTB ST i30; Novatech D791SB; Pillar double butted

Rear wheel

WTB ST i30; Novatech D902SB; Pillar double butted

Front tire

Maxxis Assegai 3C, EXO/TR, 29x2.5

Rear tire

Maxxis Minion DHR II 3C, EXO/TR, 29x2.4

Cockpit

Stem

RaceFace Aeffect R, 40mm

Handlebars

RaceFace Chester 35; SM: 780mm width, 20mm rise; MD/LG/XL: 780mm width, 35mm rise

Saddle

SDG Bel Air 3

Seatpost

SDG Tellis dropper; SM: 150mm, MD: 170mm, LG: 200mm, XL: 230mm

Grips

ODI Longneck V2.1 Lock-On

Builds

The Spire lineup spans three primary builds, split between one carbon and two aluminum frame options. All models are equipped with 29-inch wheels, 170mm forks, and four-piston SRAM Maven brakes paired with large 200mm rear rotors.

The flagship Carbon Eagle 90 build features a RockShox ZEB Ultimate fork and Vivid Ultimate shock, offering extensive damping adjustments. It utilizes SRAM’s GX Eagle Transmission for wireless shifting and rolls on DT Swiss EX 1700 aluminum wheels wrapped in Schwalbe Magic Mary and Albert tires.

The mid-tier Alloy Eagle 90 shares the exact same wireless SRAM drivetrain and ZEB Ultimate fork as the carbon model, but swaps the rear shock to a Super Deluxe Ultimate and moves to slightly heavier DT Swiss E 1900 wheels. This build represents a strong value for riders who want top-tier suspension and shifting without the carbon price premium.

The entry-level Alloy Eagle 70 steps down to a RockShox Domain Gold RC fork and a Super Deluxe Base shock. It relies on a mechanical SRAM Eagle 12-speed drivetrain and rolls on WTB ST i30 rims with Maxxis Assegai and Minion DHR II tires. Across all builds, Transition specs short 165mm cranks to help mitigate pedal strikes given the low bottom bracket.

Alloy Eagle 70

$4,199

Selected

Alloy Eagle 90

$5,599

Carbon Eagle 90

$7,699

Reviews

Reviewers consistently characterize the Spire as a highly capable descender that manages to avoid feeling like a lifeless plow. At high speeds, the chassis offers immense stability, giving testers what one described as an "I’m Loic Bruni!" (Bebikes) sensation when pushing through rough terrain. The suspension kinematics provide a supple initial stroke that "pitter-patters" (YouTube) over trail chatter, while retaining enough mid-stroke support to keep the bike eager to jump and change lines.

However, testers noted distinct tradeoffs to this aggressive design. The bike requires speed to function properly; on flat or mellow trails, the long wheelbase can feel sluggish and requires extra rider input to maintain momentum. Additionally, a few reviewers found the frame—particularly the aluminum version—transmitted noticeable feedback on repetitive square-edged hits, leading to hand fatigue on extended rock gardens.

Climbing performance was a frequent point of praise, defying expectations for a 170mm-travel platform. Testers found the seated position comfortable and efficient, allowing them to grind up steep access roads with minimal front-end wander. When the trail points down, that same geometry provides a massive margin for error, delivering a sense of security even when "dropping into an elevator shaft" (PinkBike). Ultimately, reviewers agree the Spire rewards an active, aggressive pilot looking to tackle the steepest tracks available.