Stealth Bomber Electric Bicycle
Firstly the Stealth Fighter weighs in at 34kg or around 75lb compared to Bomber’s 116lb or 53kg. It has a full Cro-Mo frame and rear swing arm which are both light and strong. In fact, Stealth is so confident about the strength of the frame and swing arm, they offer a conditional life time warranty on these components. Stock forks are presently single crown RST items with a 180mm travel. Rear suspension is taken care of by a DNM air shock which provides a very healthy 200mm of swing arm travel. Both shocks are fully adjustable in relation compression and rebound making the bike’s handling and compliance very easy to tune to your liking. The rear shock also has an easy to access lockout so you can push hard on the pedals without losing energy to the suspension.
The Fighter uses a straight derailleur-free chain line that incorporates a two speed Schlumpf bottom bracket. These are a great unit that utilizes a planetary gear system which provides a 1.65:1 overdrive through the pedals. This makes it possible to pedal assist the bike even at the upper end of the bike’s speed envelope. Gear changes are made by kicking a button on each side of the cranks. This may sound a little awkward but you soon get use to the action. It’s also quite nice not to have the handle bars cluttered up with a gear shifter.
One of the important features of the pedal drive line on this bike is that there are no tensioners or derailleur to knock off or damage when riding through rough terrain. This does however come with a compromise in that the bottom bracket moves with the suspension. Purists will argue this is a bad thing however with the bottom bracket mounted directly below the suspension pivot point, very little movement with the suspension is produced. In fact, while riding it’s difficult to notice the movement at all.
The Fighter uses a custom-spec Crystalyte hub motor for an electric drive. (read our review on this hub motor here) The motor is based on the HS3540 however it uses a custom wind to meet its design speed of 50kph at 48V. Also includes higher spec bearings and hall sensors together with a longer axle to suit the beefy swing arm. It has a 14-tooth single speed free wheel and a 38-tooth chain ring. This gives the bike good low speed pedal assist together with high speed assist via the Shlumpf’s second speed overdrive.
The motor is laced into a high strength 24” rim using seriously strong heavy duty spokes. It would take some crazy off road action to ever come close to breaking this wheel. 3” wide Razor Back knobby tires are fitted as standard equipment with 2 ½” Schwalbe Crazy Bob tires a small cost option for urban / dirt jump duties. It’s worth noting that the Crazy Bobs are in fact “Moped rated” so you can be confident they will handle the stresses of day to day high speed commuting. Speed wise, I found 31-MPH to be a fairly conservative figure that is reached quickly and easily. Winding the bike right out on flat road saw a max speed of 34-MPH so that’s a nice little bonus.
Controller duties are taken care of by an 18-FET custom Crystalyte controller. Although the Fighter uses a 48V power system, high voltage componentry is used throughout including high powered 4110 FETS and 100V capacitors. A 65 amp limit is set within the controller giving the bike a total output of just over 3000 watts. A half twist throttle is used together with a regen button on the left-hand side that provides significant braking force while at the same time returning some energy to the battery.
With regards to power output, all Stealth bikes are shipped out at set current and speed limits to suit the specific countries’ statutory and legal requirements. In the case of the US market, The Fighter is set to 750W which in turn provides a top speed of around 20-MPH. Should the purchaser prefer to operate the bike in “competition mode” and have the full 3000W available, a minor internal modification needs to be made to the bike. The decision to activate competition mode then falls squarely with the purchaser.
To complement the controller, a direct plug-in Cycle Analyst E-bike computer is built into the frame of the bike. (read our Cycle Analyst article here) Being direct plug-in, the CA takes information directly from the controller and in turn feeds back information to the controller in order to limit current and also act as first line of low-voltage protection for the battery pack. It also allows the rider to program a maximum speed limit and maximum power limit up to the set 3kW threshold.
The Fighter has three layers of battery protection. Firstly, the low voltage feedback from the Cycle Analyst. This is set to reduce power to the motor when the low voltage limit is reached. As the power reduces, typically the voltage will begin to rise slightly again allowing the bike to continue to operate, but at a reduced power level. The next level of protection is from the Battery Management System (BMS). If the BMS low-voltage threshold is reached, power will be cut to the motor completely. To reset this, the power needs to be cycled to the controller. This allows you then to get a few more miles out of the bike under very light acceleration. The third level of protection is built into the actual controller and its basically a fail-safe, should the other two systems fail. The CA is always the first line of defence with the BMS second and finally the controller as a third. Battery management is of the utmost importance with electric bikes, and Stealth has certainly taken excellent care of this.
The bike uses a LiFePO4, 48V / 1.0kWhr battery pack complete with a built in BMS system to ensure the pack is kept in a healthy balanced state. Stealth states that the pack is good for 1000 cycles which in real terms is around 6 to 7 years of operation based on you riding the bike 3 times a week over this period. The battery is designed for quick removal and replacement also so it’s a simple task to swap over battery packs if you go for the optional second pack. Once the side panel is removed from the bike, the battery can be unplugged and withdrawn from the generously-sized battery compartment. Charging time is only 2 hours with the charger being nice a compact and easily to stow in your backpack should you want to bring it with you.
Stock brakes are the Gator 6-pots with 203mm discs back and front. These give you some serious fade-free stopping power and are more than ample for the bike. There is also an 8-pot Gator brakes option available, or if you want the absolute best, the Magura MT8 system is also listed as an option.