Turbo Levo FSR Expert 6Fattie, an electric fat-bike from Specialized

Specialized Turbo Levo FSR 6Fattie’s story actually starts around 5 years ago when Specialized launched their first e-bike, the Turbo S. At that point even Specialized’s founder Mike Sinyard wasn’t convinced that e-bikes were a way forward, pointing out that the impetus actually came from a small team of their engineers in Switzerland.

It wasn’t long before the Turbo S far exceeded their expectations though, and new offices were built in Switzerland more or less specifically for their Turbo line. With the street focused Turbo S selling like hotcakes, it was time to focus on a new challenge.

In typical Specialized fashion though, this couldn’t be just another mountain bike with a battery and motor slapped on it. No, it needed to look and ride like a Specialized Stumpjumper just with a little extra ‘jump’. The end result is the Turbo Levo FSR 6Fattie.

Specialized claims that during the development of the Levo FSR their goal was to create a mountain bike with pedal assist built in, not an e-bike with mountain bike tires. That may sound like splitting hairs, but what they really wanted was to retain that classic Specialized handling and mountain bike feel with the addition of the pedal assist which included a short 459mm chain stay.

For their engineers, that meant a completely custom design with their own motor and batteries that could be cleanly integrated into the frame. Custom batteries were built to keep the silhouette of a solid down tube – as well as allow space for a water bottle. A custom motor was sourced that wasn’t the most powerful on the market at 250w/530w max, but was nearly silent and could be tuned to the desired torque curves. Basically hidden under the plastic motor shroud is the motor brace that Specialized claims is their largest forging to date. Imagine a donut with a brace in the middle to provide the stiffness needed to harness the combined power of the rider and the motor.î

Just as important as the motor, the battery plays an important part in not only the bike’s range, but how it looks. In this case, Specialized has two different batteries – one for the S-Works and Expert models with 504Wh and a slightly lower 460Wh battery for the Comp and below. Each battery is built with 40 cells in two rows, 20 on top and 20 on bottom. The larger watt hour batteries use a 3.5v cell which Specialized says is the same cell used on the Tesla model S, only the Tesla uses 6-7k cells versus the Levo’s 40! Smaller capacity batteries use a 3.2v cell, but the two batteries are interchangeable so if you purchase a bike with one of the lower watt hour batteries you could upgrade to the longer lasting model.

As for total battery life, Specialized estimates that each battery should be at 100% performance for roughly 700 complete charge cycles. That means if you were to completely deplete the battery every day, you’d get almost two years out of the battery before it’s capacity diminished. That’s a lot of riding. At that point the battery would still work, but it would be like an old laptop that just doesn’t hold a charge like it used to and could be recycled and replaced with a new battery.

In order to work, every e-bike has to sense both speed an torque. Torque is sensed within the motor at the crank, but speed is a little more difficult. Specialized didn’t like how most e-bikes use essentially a spoke magnet with a speed sensor bolted onto the chainstay, so they found a better way. The magnet is now attached directly to the brake rotor with the sensor hidden in the dropout. That makes the system a lot more robust and less prone to getting kicked or knocked off after a crash. It is important to know that without this magnet though, the system will not work – a fact Specialized employees were reminded of when they once swapped wheels after a flat.

Each bike uses a custom crankset from Praxis Works along with a steel narrow-wide chainring. The steel ring is used for obvious reasons to cut down on wear, though Specialized claims drivetrain wear has been similar to what they’ve seen on the spectrum of classic bikes. Technically the crank uses a standard BCD so you could change the ring (within the confines of the built in chainguide), but with the pedal assist Specialized expects most riders to be happy with the 32t ring. The cranks are also a good bit shorter than what you’ll find on a classic bike (down to 165mm) along with a 7mm higher bottom bracket.

Other component highlights includes a RockShox Pike RC 140mm fork, and a custom Fox Float Factory DPS rear shock with Autosag and their RX trail tune that did a fantastic job keeping the 135mm of rear travel in check. Braking duties were taken care of through the SRAM Guide RS, though all the bikes feature upsized rotors with 200mm front/ 180mm rear.

Turbo Levo FSR 6Fatties will be sold in S-Works, Expert, and Comp builds which all utilize the same M5 Premium Aluminum frame with 140/135mm of travel. The Turbo Levo FSR Comp 6Fattie is also offered in a women’s version along with the Turbo Levo HT 6Fattie which is offered in men’s and women’s. The Turbo HT Comp Fat comes in a single build with pedal assist and 4.6″ tires. U.S. pricing is yet to be determined, though from the possible figures we’ve heard, it’s not as steep as you might think. Sold with a 2 year, 1,500 km warranty, the Turbo Levo FSR 6Fattie series will soon be available in the U.S. but only in limited quantities.