Trials is a series that's built on completing short courses of about a minute each, so it makes sense that Ubisoft and RedLynx would bring their motorcycle-driven series to mobile devices. Trials Frontier makes a valiant effort to reach the heights of its console big brothers, even in the face of familiar (and unwelcome) free-to-play elements. Though Frontier may not quite have the same addictive pull as its predecessors, it's a very solid racing game on its own and one that transitions well to mobile platforms.
Frontier immediately stands out from previous Trials games by introducing a story. A western-themed town is being terrorized by a notorious biker and it's up to the player to track him down and beat him in a one-on-one race. This element allows the game to add in various characters to offer missions and goals for certain trial runs.
Putting the borderline-silly narrative aside, Frontier does feel like a Trials game in many of the ways fans of the series would expect. A control scheme that relies on four virtual buttons in the bottom corners turns out to work very well, as I didn't have any troubles accelerating or attempting to perform tricks. The only trouble here is in navigating certain jumps, since there's really no way to slow down or otherwise manage acceleration, other than to jam on the brakes. Not being able to judge my speed hurts a bit when making some jumps, since I'll either overshoot a platform or hang just along the edge and fall backwards. Still, I managed to ride, jump, and crash, just as I would in other Trials games.
Frontier is a free-to-play game and that means there are certain freemium tropes that'll occasionally pop up. The most notable one is the fuel canister system, which determines how often you can race. On the surface, this appears limiting, especially since each race costs five fuel canisters. But by completing races and leveling up, the fuel canister counter will automatically refill and the max capacity will increase. I was able to complete Frontier sessions that lasted hours by continuing to level up and because the fuel canister quickly refills itself on its own every few minutes.
But one main issue that I had with Frontier is the idea of having to use those finite fuel canisters to retry a race. The Trials series is largely built on trial and error. If you misjudged a crucial jump by about an inch in previous games, then it was safe to try again. Since Frontier's free-to-play nature means you only get so many cracks at a race during a session, repeating runs for a price makes the idea of retrying until you get it just right a little less fun. Retrying in the middle of a run doesn't cost any fuel canisters, but there were many instances in which I finished a race by accident after making one last mistake.
While it may be easy to collect fuel canisters, attempting to upgrade your bike will all-too-often bring a gaming session to a grinding halt. New bikes can be built and upgraded by collecting parts along a prize wheel. Finding the right piece isn't as hard or as random as it looks, since the wheel can be manipulated by holding your finger along the piece that you want. The trouble comes after submitting those hard-earned pieces and having to wait periods of 15 minutes or more for installation, unless I shelled out gems or real money to accelerate the process. It's infuriating for impatient players and to anyone that just wants to get back to the game without having to pay this kind of toll.
Trials Frontier certainly tries its best to evoke the raw passion that goes into completing these obstacle-filled runs. In fact, it's a very solid racer with controls that work very well with touch screens, even if those controls can get a bit slippery. Even with some annoying free-to-elements that can be very difficult to swallow and take away from the Trials experience a bit, this winds up being a pretty sweet ride that stands out on its own. 
This review is based on an early iOS version of the game provided by the publisher. Trials Frontier is also coming soon to Android.