When Transition launched the Sentinel three years ago, they were way ahead of the curve in figuring out how geometry for today's all-mountain/enduro frames would progress. With their introduction of Speed Balanced Geometry, they changed the entire industry’s take on short offset forks, reach numbers, and head angles. When we originally reviewed that bike, we said this “is a downhill bike masquerading in trail bike attire. If gravity is your game, and you’re looking for a flat-out destroyer 29’er, the Sentinel should be on your short list.” It has stood the test of time, and is just as relevant today as it was when released in 2017.

Although the 120mm travel Smuggler might have been more appropriate for most of us, the Sentinel still flew off the shelves, helping spread a “big bikes for everyone” train of thought that has maintained its grip to this day. But people got used to it. We learned how to steer very slack bikes with lots of trail around tight corners. We learned how to keep our weight up on the front wheel so that we could corner these long bikes properly. We like it, and we’ve kept asking for more.

Fast lines on the new Transition Sentinel

In a lot of ways Transition hit the nail on the head with the first Sentinel, but as you’ll come to find, these folks are not ones to rest on past laurels. As with the 2020 Scout, this new bike is a refinement over its predecessor, incorporating a sexy new design philosophy filled with hard, fast lines and a slew of clever updates and improvements. Not only that, but it’s one hell of a fun ride, so much so that I’ve just ordered one. I don’t yet have much time on it, but I’m looking forward to a summer full of long rides, and will most certainly be telling you my long term thoughts. In the meantime, let’s take a first look at what this gorgeous looking machine is all about.

Design

You’ll recognize Transition’s updated 2020 aesthetic from the Scout. Angular, large form factor tubing and a more sparse graphic treatment than the previous Sentinel gives it an entirely different feel. It just screams of high speed and bold lines . It’s all new and all carbon; that’s front and rear triangles, as well as the rocker link. No word of an aluminum frame in the future, which speaks to the upper echelon of bike design and manufacturing that Transition has worked their butts off to get to. Hidden in this gorgeous frame are a whole bunch of little secrets, which we will discover below.

Hidden in this gorgeous frame are a whole bunch of little secrets, which we will discover below.

Suspension

The stock shock set-up on this bike gives it 150mm of travel (just under 6”), 10mm more than the previous version. Transition has also re-worked the kinematics of their “GiddyUp” four-bar suspension to make it more progressive. This allows for a wide range of adjustability and usability. If you like a super plush, bump gobbling bike that feels like you’re riding on a cloud, run 30% sag or more. If you’d prefer a very responsive poppy ride that feels more like a down-country bike than an enduro rig, bump up the air pressure to 25% sag, and you’ll have just that.

The changes they’ve made also mean the new Sentinel is now coil-compatible, which we’re certainly happy about. The simplicity and consistency of coil-sprung suspension, along with the downhill intentions of this bike, make for exciting prospects in building it up as a mini-DH rig that’ll take bike-park duty in the summer and all-day cruises in the winter.

As with everything on this re-designed Sentinel, Transition’s engineers have taken what they’ve learned over the past three years and tweaked things like anti-squat and chain-growth. Through small changes in where the pivots are located, they’ve improved the bike’s pedalling efficiency (less bobbing, even with the shock open) while improving the wheel’s ability to move out of the way when it encounters a bump.

All this makes for a more supple entrance into the bike’s suspension, with a bit more support as you push through turns and off of lips, and a nice coddling caress of increased bottom-out protection when you accidentally case the landing.

Transition smoothed out all the rough edges (while conversely giving the frame sharp edges!) and refined it into a weapon that is versatile and capable enough to be your one bike.

Geo

The original Sentinel was longer and slacker than previous bikes, which turned a lot of heads. With that bike, Transition hit a sweet spot, and they have not deviated much on the new model. Reach stays about the same across the board, head angle goes from 64 to 63.6 degrees, and top tubes get a hair shorter due to the even steeper seat tube angle. I tend to think that this style of all-mountain/enduro bike will settle at these sorts of numbers - in my experience getting any longer or slacker has diminishing returns, and reduces the fun-factor.

In addition to steeper seat tube angles (they vary on each size, but 77 degrees on average up from 76.4), an uninterrupted seat tube allows riders to run extremely long seatpost droppers. A 5’9” rider can now run a 200mm post on a medium frame, and small riders can run seatposts longer than 100mm. This is a huge benefit, allowing everyone to reap the benefits of getting your saddle completely out of the way when you’re attacking steep terrain.

Space for up to a 2.6" rear tire.

Details

There was a time, back at the old shop, when I’d chuckle about a silly goof that Transition made, like routing their external cables over their logo. We all still rode their bikes over the Yetis we also sold because they were so much more fun, but there was always some small oversight that would crack us up or make us shake our heads in confusion.

Those days are long gone, and Transition’s attention to detail, amazingly, seems to surpass the fun-factor that they build into each and every one of their bikes. There are a number of design features on this new Sentinel that really speak to how much thought, time, and effort Transition has put into it.

One important detail that can be easily missed (they are hidden from view) are the little shields that cover their pivot bearings. The shields provide an additional barrier over these very important and very difficult-to-change parts. This feature is beneficial regardless of whether you live in an ever-wet area like the Washington based brand does, or in the dusty deserts of Utah, where the fine sand gets into every nook and cranny.

The flush-mounted chainstay protector wraps around the inside of the rear pivot.

Another hard to see detail is the extension of the flush-mounted chain and seatstay protector, which extends to the small shelf created by the inside of the drive-side chainstay pivot. On many bikes this space creates a pinch point that will occasionally suck your chain in. On this bike, that flaw turns into an opportunity to muffle additional noise.

Tubes-In-Tubes technology has evolved into a higher form, and now instead of just providing foam tubing through which to route your lines inside the frame (therefore eliminating any rattling), Transition has molded tunnels into the frame so that you no longer have to fish around for your lines. This is a boon to any mechanics, whether you’re at home or at the shop. Speaking of mechanics, they will rejoice to find that Transition has opted to leave the rear brake externally routed. This eliminates having to uncouple a brake hose from your lever body to change it. An uncommon occurrence, but a tedious one, especially if you find you don’t have a spare olive and barb sitting around.

Aside from the water bottle mounts (which fit a large bottle on everything but the small frame) you’ll find another set of mounts under the top tube. This is not an attachment for a mini-me size water bottle, but a tool accessory mount. Wolftooth Component’s B-Rad mount and accessories fit tidily on here, further reducing the need for bulky back/hip packs.

Lastly, with the continued popularity of wide tires, Transition increased clearance in the rear triangle to accommodate up to 2.6” tires. I personally like running a narrower tire in the back, but based on all the requests we get for 2.6” rear tires, I know that’s not the case for everyone.

Hannah Bergemann with her Spicy Thai Transition Sentinel

Final Word

In 2018, riding the 35 lb aluminum Sentinel, we concluded the bike was “a downhill bike masquerading in trail bike attire.” We loved it, but it was hard to think of it as a total quiver killer since it’s heft and at-the-time revolutionary geometry edged it out of do-it-all territory. But with the 2020 Sentinel, Transition smoothed out all the rough edges (while conversely giving the frame sharp edges!) and refined it into a weapon that is versatile and capable enough to be your one bike. It will soon be mine, and I’ll look forward to telling you more about it!

- Dan at Fanatik