BMC has launched a brand new Fourstroke AMP LT eMTB, aimed at cross-country and downcountry riders the Fourstroke AMP LT features 120mm of travel and shares a lot in common, both in design and ride, with its non-motorized Fourstroke peers.
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This is BMC’s first e-MTB since its Speedfox AMP and Trailfox AMP quietly slipped out of the catalog a few years ago. A lot has changed in the best electric mountain bike sphere since then and the new Fourstroke AMP LT slots right into the emerging trend of lightweight e-MTBs. BMC has specced a German TQ motor and with some careful design and specifications has built one of the lightest of the peg e-MTBs on the market.
Design and specifications
BMC’s aim was to create an e-MTB that rides as close to the un-powered Fourstroke LT that BMC released last week. Geometry is very similar, featuring the same 66.5-degree head angle and 457mm reach in a medium. In fact, the only real changes BMC has made is a marginally steeper 77-degree seat angle, adding 13mm of stack, 3mm to the chainstays, and a slightly lower bottom bracket settling on a drop of 40mm. The shock also has a different tune to the one used on the Fourstroke LT, although the bikes we were riding had a pre-production tune.
Rather than go with one of the tried and tested best e-MTB motors, BMC choose German manufacturer TQ who approached them with its new lightweight motor fitted to a prototype bike. The capabilities and ride feel impressed BMC who saw it as an opportunity to electrify it's 120mm Fourstroke LT which was already under development.
The big advantage of a lightweight motor system like the TQ design, which is also used on the recently released Trek Fuel EXe, is that it saves a considerable amount of weight. The TQ-HPR50 motor and battery are claimed only to add roughly 4kg to the bike weight. TQ’s control over the components and circuits used within the motor also means the motor unit has a very compact size, building up into a bike that has the svelte figure of a non-motorized bike.
Lower motor and battery weight means that BMC hasn’t felt the need to spec e-MTB-specific components. Standard forks, wheels, and tires further reduce the grams with the Fourstroke AMP LT LTD version weighing in at a claimed 15.9kg.
That weight makes it considerably lighter than other lightweight e-MTBs like the Pivot Shuttle SL (claimed 16.5kg), Forestal Cyon (claimed 17.1kg), and Trek Fuel EXe (claimed 17.47kg). It even manages to beat Trek’s very cross-country-orientated E-Caliber by roughly 435g based on the manufacturer's provided weights.
The TQ-HPR50 motor itself puts out 50Nm of torque with a peak power of 300 watts and is paired with a 360Wh battery. TQ says that this setup will match the needs of riders, although there aren't any published numbers in the expected range. TQ does offer a bottle cage mounted Range Extender if you need more and the system uses some smart circuitry to drain the range extender first/charge the main battery first when fitted. The motor is controlled by an up-down button controller and the motor and ride stats are displayed on a simple black-and-white screen mounted in the top tube.
A partner app lets you configure the motor characteristics and pair your best MTB GPS computer or smartwatch to the motor via Bluetooth or Ant+ and record power and cadence data.
The frame is nicely finished as well with the ability to fit two 550ml bottles in side loading cages on the downtube (one 550ml and one 350ml on a small), a steering lock to avoid the controls damaging the top tube, and guided internal cables that can be easily accessed for maintenance.
My test bike was the Fourstroke AMP LT LTD version which meant I were treated to a smorgasbord of nice componentry. A Fox 34 SC Factory and Fox Float DPS Factory shock took care of the suspension while the SRAM XX1 drivetrain and RockShox Reverb dropper post used SRAM’s wireless AXS wizardry. The brakes fitted are G2 Ultimate and paired with SRAM Centerline Rotors (180/180 to keep the speed in check.
As mentioned previously, BMC hasn’t specced any e-MTB-specific components so the bike rolls on a standard DT Swiss XRC 1200 wheelset and fast-rolling Maxxis Rekon 2.4in tires.
The bike was finished with Truvativ's Atmos 7K stem and 760mm wide BMC MRB01 Carbon bars, with a Fizik Antares R5 to sit on.
Performance
BMC invited me to take the Fourstroke AMP LT and its non-engined Fourstroke LT out on a first ride during a recent press trip to get an impression of how the new e-MTB bike rides and compares to the non-motorized version.
This is the first of the new lighter-weight e-MTBs I have ridden and it's easy to see why a lot of people are preferring a lower-powered but more svelte e-MTB. Compared to any other e-MTB I have ridden, the Fourstroke AMP LT is very playful. It's easy to maneuver and flick around on the trail plus it jumps confidently without leaving you needing to rely on speed and momentum to muscle through successive jumps. Compared to the regular Fourstroke LT it still has some of that planted surety that e-MTBs are known for but not to the point that you feel like a passenger when trails get tight and technical.
Riders who are coming to the TQ motor from a full-powered e-MTB there's a good chance you are going to feel a little underwhelmed though. The focus on lighter weight has a lot of benefits, however, the lower-powered motor and less aggressive tires mean it doesn't have the sit and power-up capabilities. That said, there are plenty of riders who enjoy being engaged in a climb and the subtle extra oomph, alongside some rider finessing and skill, is going to be just enough to get you to the top while still feeling rewarding. Turbo mode is certainly noticeable on climbs although the trail and eco mode are far less obvious and feel more like a stiff tailwind than motor-assisted.
The Fourstroke AMP LT was extremely quiet, giving it a superbly refined ride feel. Not only is the motor silent, but there are also no rattles from the motor or battery, which is something I have experienced from other engines and bikes. The bike itself is also very muted with no chain slap or knocks, just the sound of tires on the trail and a backing track of freewheel clicks.
Early verdict
Silent, smooth, and agile, the Fourstroke AMP LT is as close to a regular unassisted bike as I have experienced. The trend of lightweight eMTB looks set to continue and those desiring a more traditional, rather than an augmented, assisted riding experience are going to love this bike.
The ride experience really does feel like it's under your own power, rather than full power. If you’re riding with big output e-MTB it's going to feel like you have brought a knife to a gunfight on steep climbs. That said, the low weight, fast tires, and zero pedal resistance will allow the Fourstroke AMP LT to put the hurt on those bikes when riding flatter, faster, on the limiter climbs, or technical twisty descents. On the descents, the Fourstroke AMP LT didn’t feel like it needed to be muscled around giving it a more playful and fun ride rather than the point-and-plow style of heavier bikes.
Tech specs: BMC Fourstroke AMP LT
- Price: $14,999.00 / €13,999.00
- Discipline: Cross-country / downcountry
- Frame: Fourstroke 01 Premium Carbon with Autodrop Technology
- Head angle: 66.5 degrees
- Seat tube angle: 77 degrees
- Reach: 457mm (medium tested)
- Fork: Fox Float 34 SC Factory
- Shock: Fox Float DPS Factory
- Wheels: DT Swiss XRC 1200 Wheelset, 30mm
- Tires: Maxxis Rekon 2.4in TR EXO
- Drivetrain: SRAM XX1 EAGLE AXS, 10-52 teeth 12-speed cassette
- Brakes: SRAM G2 Ultimate / SRAM Centerline Rotors 180mm
- Seat post: RockShox Reverb AXS
- Saddle: Fizik Antares R5
- Bar: BMC MRB01 Carbon 760mm
- Stem: Truvativ Atmos 7K
- Sizes: S, M, L, XL
- Weight: 15.9kg (claimed)
