When you first visit the Stealth Electric Bike web site, most people are drawn to the aggressive lines and impressive performance figures of the Stealth Bomber. However, more and more people are looking more closely at the Bomber’s smaller brother, the Stealth Fighter, and for some very good reasons. Besides the obvious cost difference between the two models, there are quite a few other compelling reasons why someone might prefer the Fighter over the Bomber. So let’s have a closer look at the Fighter to better understand why Fighter E-bike sales are pushing ever closer to the flagship Bomber.
Specifications for the Stealth Fighter from the official web site
| Speed « USA » Mode Engaged : 20 mph « Competition » Mode Engaged : 32 mphPerformance Range : Up to 35 miles Noise @ 50 km/h : 65 dBPower « USA » Peak Power Engaged :750 Watts « Competition » Peak Power Engaged : 3.000 Watts Electrical Cost |
Drive Train Transmission : 2 Speed internal gearboxSuspension Front Travel Standard : 180mm (upgraded : 200mm) Rear Travel : 200 mmBrakes Front Hydraulic Standard : 6 pot – 203mm (upgraded : 8 pot – 203mm) Rear Hydraulic Standard : 6 pot – 203mm (upgraded : 8 pot – 203mm)Weight Weight : 75 lbs (env. 34kg)Economy Cost : Less than $.01/mile Zero Emission |
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.
The Fighter gives the impression of being quite a small bike, mainly due to the 24” wheels. However the actual wheel base is slightly larger than a standard mountain bike. Climbing onto the bike you soon realize just how tall this bike is with a massive 14” of clearance at the bottom bracket. That’s around 2” more than a normal downhill bike. This ground clearance together with the generous suspension travel makes getting over logs and other rough terrain a much easier proposition. As you gain confidence, you soon find yourself attacking obstacles you normally wouldn’t dare to have a go at on a normal bike. Having 3kW on tap, you tend to come up to the obstacle and give the throttle a blip to lighten and lift the front wheel over. Then a slight back-off so the back wheel doesn’t hit too hard, then another quick blip and you’re over. In no time this becomes quite intuitive allowing you to tackle increasingly difficult terrain at speeds normally reserved for dedicated gas powered trail bikes.
The bike handles just about any hill you can throw at it with enough power to flip over backwards before it actually runs out of pulling power. Of course constant hill climbing is going to heat up the motor and I did find the HS3540 building up quite a bit of heat during offload testing. It’s obvious you need to treat the bike with some mechanical sympathy and use some common sense when tackling steep terrain. Sand is another area where mechanical sympathy is required as this puts a huge stress on the motor. There have been some reports of motor failures under these conditions. Subsequently I believe warranty on the motor has been amended to exclude operation of the bike under sandy conditions.
With an as tested top speed of 55-kph (34-MPH) the bike makes an excellent commuter also. Although stopping at a set of stop lights will draw a lot of looks and questions from other riders, when you’re mobile, the bike’s sleek lines allow the bike to stay relatively anonymous with most people not taking too much notice at all. Good for staying under the radar. 25-28-MPH (40 to 45-kph ) seems to be the sweet spot for the bike in relation to battery efficiency. Cadence is comfortable at this speed so it’s easy to provide some pedal assistance (whether for exercise, or to extend the battery range). This in combination with keeping the motor at around 80% of its top speed equates to reasonable economy, and sees typical figures of around 17 watt hour per km. These figures are in line with the factory advertised economy figures.
In summary, if you are after a bike-like experience that still offers some serious electric performance, then the Fighter may well be the right choice for you. One other consideration should be your build and height. Riders who are 6′ plus may find the riding position a little less than optimum. However, I am 6’3″ and still found the bike reasonably comfortable to ride. The other consideration is body weight. Riders over 200lb will need to make an informed decision whether the Fighter is the right fit for them. The Fighter will certainly handle a heavier rider however; the rear shock will need to run a higher pressure which in turn will provide a less compliant ride. General consensus is that larger riders should consider the Bomber over the Fighter in most cases.
Editors note:
Story Submitted by John “Kepler” Wessel of Melbourne Australia, a respected E-bike builder and enthusiast, who owns both a Stealth Bomber and a Stealth Fighter (lucky guy).
The Stealth Fighter is available now for purchase world wide from the Stealth .
We leave you with picture show of the big brother to the Fighter, the Stealth Bomber:
