The new 2025 Transition Sentinel on test

For MY 2025, Transition tweaked both the geometry and kinematics of their popular trail bruiser, the Sentinel. The new 2025 Transition Sentinel rolls into the new season with several new features, including the integrated BOOM Box – no, it doesn’t play loud music! However, the latest iteration of the Sentinel still generates 160/150 mm of travel, and keeps on rolling on 29” wheels, maintaining its downhill-focused trail character. We tested the new Sentinel to find out why the BOOM Box is still useful despite not blasting hip-hop while you’re riding and how it fares on the trail.

Clean lines, an understated look, and serious downhill potential are just a few of the typical features of Transition bikes. If you know Transition, this comes as no surprise, given that Transition’s team really knows how to get rowdy on the trails, as we experienced firsthand during our visit to Bellingham last year. And Transition bikes are built exactly to do that! So it’s for a good reason that the new 2025 Transition Sentinel looks rowdy even when stationary, letting you know clearly that it’s designed for uncompromising downhill performance. This aggressive trail bike has been an integral part of Transition’s portfolio since 2018, and while the overall appearance has remained largely unchanged, there are many exciting updates for 2025.

Although the new Sentinel relies on a slightly sharper, more modern design language, the improvements are mainly technical ones. Amongst the highlights is a new cable routing system, a redesigned chainstay protector, and an updated geometry and kinematics, which even allow you to convert the Sentinel to a mullet bike with a smaller 27.5-inch rear wheel. Additionally, Transition ventured into integrating a storage compartment into the frame for the first time – at least on their bikes with a carbon frame.

If you’re looking to get the new 2025 Transition Sentinel, you can choose between a carbon and aluminium frame. Prices start at € 2,120 for the alloy frame kit, going up to € 8,999 for the complete Transition Sentinel X0 AXS bike we tested, which tips the scales at 15.1 kg in size XL.

The new 2025 Transition Sentinel in detail

For this first ride review, we tested the 2025 Transition Sentinel X0 AXS, which relies on a full carbon frame. While at first glance, the new 2025 Sentinel might look pretty much unchanged from its predecessor, upon closer inspection you’ll notice several important updates. First, Transition’s engineers redesigned the cable routing system of the carbon frame, which now relies on simple, bolted plastic covers that hold the cables securely in place. This gets rid of the ugly cable mess around the cable ports, while at the same time ensuring a quieter ride on the trail.

One thing most bike manufacturers can’t get around these days is integrating a storage compartment into the frame. With the new 2025 Transition Sentinel, the American brand introduces the first iteration of their proprietary BOOM Box, which stands for “Burritos Or Other Munchies” – which makes it pretty clear what you’re meant to stuff it with! You can access your munchies by sliding the lever to the side and removing the lid. The lever is easy and intuitive to operate, and, unlike many other manufacturers, Transition chose not to place the storage compartment under the bottle cage. Instead, they integrated it deeper towards the bottom bracket, which allows for a lower centre of gravity, but also makes it harder to pull out the two storage pouches, because the bottle cage or the actual bottle might get in the way. The two pouches come standard with every frame and offer enough room to stow away a spare inner tube or tools, and inside one of them are small compartments for valuables. Fortunately, if you ever have to pull hard on one of the items inside the compartment, you won’t damage anything, because the sharp carbon edges are lined with sturdy plastic to prevent injury. If the BOOM Box storage isn’t enough, you can use the tool mount on the top tube to attach additional gear to your frame.

The chainstay protector has undergone a significant update too, and is now much bulkier, effectively preventing chain slap and paint chips. Additionally, a small fender on the chainstay prevents smaller rocks from getting jammed in the gap between the main frame and swingarm. A thin plastic guard on the downtube near the bottom bracket provides additional protection. However, we would have preferred it to be a bit wider to better cover the sides.

The spec of the new 2025 Transition Sentinel

For this first ride review, we tested the 2025 Transition Sentinel X0 AXS, which retails at € 8,999, and tips the scales at 15.1 kg in size XL. It comes equipped with a FOX Factory suspension. The 36 fork already features FOX’s new Grip X2 damper, which delivers exceptional trail performance. A matching Float X Factory air shock takes care of the rough stuff at the rear. FOX also supply their brand new Transfer dropper post, which offers an impressive 240 mm of travel and can be inserted all the way into the frame, ensuring maximum freedom of movement on the trail.

SRAM Maven Silver four-piston brakes do stopping duties, ensuring powerful, reliable deceleration in combination with a 200 mm rotor at the front and 180 mm disc at the rear. The Maven Silver edition features tool-free lever-reach and bite-point adjustments, and is pretty much identical to the Ultimate flagship model, except for a slightly heavier system weight. For most riders, this setup will be more than sufficient, while for those seeking even more braking power, upgrading to a bigger rear rotor should do the trick. As the X0 AXS name suffix suggests, shifting is taken care of by a SRAM X0 AXS Transmission drivetrain, which ensures butter-smooth shifting and relies on a direct-mount rear derailleur.

The top-tier model in the new Sentinel range rolls on an alloy wheelset, further underlining the bike’s focus: robust downhill performance without saving weight in the wrong place! The DT Swiss wheelset with XM481 rims is a sturdy companion for rough descents. The rims are paired with MAXXIS tires – an ASSEGAI at the front and a Minion DHR2 at the rear. Both tires come in the EXO+ casing and slightly harder MaxxTerra rubber compound. For the first tire change, we recommend reaching for the softer MaxxGrip compound at the front, and if you’re looking for even more downhill performance, you should use the tougher DoubleDown casing at the rear.

All spec variants of the new 2025 Transition Sentinel.

The new 2025 Transition Sentinel is available with either an aluminium or carbon frame, and as either a complete bike or a frame kit with shock. Both frame kits come standard with a RockShox Super Deluxe Ultimate shock, retailing at € 2,190 (alloy) and € 3,990 (carbon), respectively. Both variants are available in three colours.

If you want a complete bike, you can choose between two alloy models and two carbon variants. While at first glance there’s no aluminium bike with a top-tier spec – like our carbon test model – the highest-spec alloy version features many components from Shimano’s reliable, robust XT series. Additionally, the RockShox Select+ suspension delivers an excellent performance on the trail, and only forgoes the Buttercups of the Ultimate flagship model. Priced at € 5,490, the Sentinel Alloy XT offers a solid foundation at a fair price, and its components shouldn’t hold you back on the trail. That said, you’ll have to do without the BOOM Box on the aluminium frame.

The geometry of the 2025 Transition Sentinel

The new Transition Sentinel is available in six sizes, XS to XXL, whereby the smallest XS size has smaller 27.5” wheels. All other frame sizes roll on 29” wheels and can be converted to a mullet bike. Overall, the new 2025 Sentinel is longer than its predecessor, with reach values growing by just 15 mm between sizes XS and S, and in 25 mm intervals between all other sizes. Our test bike in size XL combines 505 mm reach and a relatively short 460 mm seat tube. Overall, the seat tube is short across the board, allowing you to choose the frame size based on your desired reach.

A flip chip on the lower shock mount allows you to convert the Sentinel from a full 29er to a mullet bike with a smaller 27.5” rear wheel. The chainstay length grows with the frame size too, though only with certain sizes. In other words, there are three different chainstay lengths across six frame sizes, with sizes L through XXL sharing the same 448 mm chainstays. Transition’s engineers also tweaked the head angle slightly, which is 0.4° steeper than its predecessor at 64°. To bring the Sentinel in line with modern standards, Transition also steepened up the seat tube angle, which on our test bike measures 77.9°. However, since the seat tube angle varies depending on saddle extension, the angle is steeper on smaller frame sizes.

Size	XS	S	M	L	XL	XXL
Top tube	527 mm	549 mm	577 mm	605 mm	632 mm	660 mm
Seat tube	360 mm	360 mm	390 mm	430 mm	460 mm	490 mm
Head tube	100 mm	100 mm	110 mm	120 mm	130 mm	140 mm
Head angle	64°	64°	64°	64°	64°	64°
Seat angle	79.8°	79.3°	78.7°	78.3°	77.9°	77.96
Chainstay	436 mm	442 mm	442 mm	448 mm	448 mm	448 mm
BB drop	15 mm	25 mm	25 mm	25 mm	25 mm	25 mm
Wheelbase	1,173 mm	1,208 mm	1,237 mm	1,273 mm	1,302 mm	1,332 mm
Reach	415 mm	430 mm	455 mm	480 mm	505 mm	530 mm
Stack	592 mm	615 mm	621 mm	633 mm	642 mm	651 mm

The 2025 Transition Sentinel on test

As soon as you swing your leg over the saddle, the new 2025 Transition Sentinel feels very roomy at first. The generous reach and the long-travel dropper post, which can be inserted all the way into the frame, ensure a central pedalling position that leaves plenty of room for your limbs even when riding seated. Uphill, the new Sentinel puts you in a comfortable, not overly-stretched pedalling position, which is perfectly suitable for long days in the saddle. When climbing fire roads with a steady, smooth pedalling cadence, the Horst Link rear suspension remains pleasantly neutral. However, on technical uphills that require harder pedalling, the rear suspension bobs noticeably, making it worth reaching for the climb switch to save energy. Overall, the new 2025 Transition Sentinel is a solid climber but doesn’t rank among the best in its category.

Transition clearly focused on downhill performance with the new Sentinel, and this becomes evident as soon as your tires dig into the first berm. With its central, integrated riding position, the Sentinel makes you feel at ease from the get go, encouraging you to keep your fingers off the brakes for a few more seconds. The Sentinel eagerly responds to this, rewarding an active riding style with its progressive rear suspension. When you push hard on the trail and through corners, the Transition generates speed without feeling jittery. The rear suspension always remains active, generating tons of traction and allowing you to decelerate quickly with last-second braking manoeuvres. However, in tight sections, the long frame feels slightly cumbersome, requiring a little extra strength and balance to flick the rear end around hairpin switchbacks. In faster trail sections, on the other hand, you can really open the tap! Even on long, fast trail laps, the Sentinel is always easy to control without feeling too stiff, which would otherwise drain your energy. At the same time, it impresses with precise handling and responds to steering inputs with great eagerness.

Who should take a closer look at the 2025 Transition Sentinel?

Despite the many updates and new features, the new 2025 Transition Sentinel remains true to its character. If you’re looking for a trail bike that lets you push hard without shying away from tough sections or needing many adjustments to the setup, the new Sentinel is an excellent companion. However, it doesn’t climb as eagerly as some other bikes in its class.

Conclusion about the 2025 Transition Sentinel

The new cable routing, updated detail solutions, and the revised geometry and kinematics of the 2025 Sentinel all make a clear difference on the trail. The newly integrated BOOM Box is well-designed and consistently implemented in the frame, though its position makes it a little finicky to operate. Riding uphill, the Transition is comfortable but not the most efficient bike out there. However, when gravity takes over, you can really let loose without having to make compromises, which is partly due to the consistent spec.

For more information, visit Transition Bikes’ website.

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Words: Peter Walker Photos: Mike Hunger, Peter Walker, Transition Bikes