BULLS WILD FLOW EVO SL
We’ve ridden and tested a lot of Bulls’ bikes, and most of them have been powered by Bosch, Brose or Shimano motors. This is the first one we’ve ridden that’s been spec’d with the increasingly popular Fazua motor. Owing to the motor and battery that are housed inside the downtube as one unit, Fazua has made a name for themselves with a unique design that is far lighter than traditional mid-drive motors.
How light? By pairing the Fazua motor with a carbon frame (front triangle) and other light components, Bulls ended up with a bike that weighs a scant 42 pounds. That’s a pound less than the Pivot Shuttle, making it the lightest e-MTB we’ve reviewed yet.
The Wild Flow starts with 120mm of travel in the front and rear suspension to help keep the bumps from making their way to the rider. It’s in combination with the frame and a list of other high-end components that goes into the $6,000 price tag.
The suspension is provided by a Fox 34 Rhythm fork up front and a Fox Float DPS in the rear. Wheels are DT Swiss XRC 1200 spline carbon, which are both light and very strong. Tires are 29×2.35-inch Schwalbe Nobby Nics.
Drivetrain components are top-notch Shimano XTR, including a 10-51T cassette. That huge cog definitely helps in steep climbs. Bulls spec’d this bike with FSA carbon cranks. All these components are what contribute to the high price of the Wild Flow.
The brakes are the new Magura MT8, using what they call “Carbotexture,” which impregnates carbon fiber into the levers. It has a one-finger aluminum blade on each lever, and you can swap that for a carbon blade (about a $75 premium per blade). A four-piston setup on the front and rear offers incredible stopping power and also plenty of modulation. The four-piston calipers also offer a heat advantage over two-piston calipers, as they dissipate heat better to avoid brake fade on long descents.
This is the first American-spec’d (20-mph) bike we’ve ever tested with the Fazua Evation motor. It’s a remarkable system in that the motor and battery both fit in the downtube of the bike, and the normal bottom bracket is replaced with Fazua’s own gearbox that transfers the motor’s power to the front sprocket.
It’s an incredibly light system, weighing in at what a traditional battery from another system weighs. The combination of the battery, motor and gearbox weighs in at a smidgen over 10 pounds. The 7-Ah/250-Wh battery is less than half of the capacity most batteries offer, but at 3 pounds is so light that a second one could very easily be carried in a hydration pack. We’ve done two-battery rides with traditional 400- to 500-Wh battery spares (6–7 pounds) in a pack, and they’re cumbersome to say the least. A spare battery will run you about $500.
The display is simple and tiny. It has no LCD; instead, simply colored LEDs. There are four support modes. The first one—No Support mode—is just that; the system is on but there is no power going to the gearbox. In this mode, you notice no resistance through the system. It’s like you’re pedaling a regular, albeit heavy, bike.
Breeze mode (displayed in green) is Fazua’s version of Eco and offers 125 watts of power. River mode (displayed in blue) gets you going with up to 250 watts of assist. Rocket mode (displayed in pink) peaks at 400 watts of pedal assistance.
“If you’re on the fence about electric-assist mountain bikes, this bike will change your mind!”
You can ride the bike without the battery/motor combination, and you can get a cover for the opening to keep it clean while you ride. It’s available from dealers for about $86. There’s an app that allows you to track your rides if you like, keeping an eye on battery level, etc. We didn’t find it particularly useful. The battery level is shown on the display as 10 bars of whatever color indicated by the mode you’re in, in approximately 10-percent increments.
You have to remove the motor/battery to charge it. You will also have to pull down the battery to turn the system on if you’ve had it off for over eight hours. We found this slightly annoying, yet probably a good feature to have.
WHO IT’S MADE FOR
The Wild Flow is a solid cross-country performer, built like a tank, but the lightest e-MTB we’ve ridden yet. It’s aimed at more experienced riders who want full-suspension on a bike that’s fairly nimble, just enough power to make it easier to climb hills. It’s a lot of bike for the money.
On the trail this bike feels light, for a full-suspension e-bike that is. Just three years ago most of the bikes we tested were about 10 pounds heavier. That’s a massive difference in a short amount of time. It’s noticeable in putting it on a bike rack or carrying it upstairs, not to mention while riding. Because of this, the bike is pretty nimble in comparison to other e-MTBs. The weight is low, where it should be, to keep it stable as well.
This bike has nowhere near the power of a Bosch, Yamaha, Brose or Shimano, but that’s somewhat where it becomes really great. It’s so close to the feeling of a normal mountain bike, and the power delivery is almost subtle and so quiet that you can forget that you’re on an e-bike. If you’re on the fence about electric-assist mountain bikes, this bike will change your mind!
When going over 20 mph, the motor truly gets out of the way. You feel no drag at all from the motor system. The same can be said for when you put the bike in No Support mode. We found that we liked River mode (the middle level) the most, with Breeze a close second. We used Rocket sparingly on steep climbs, and it proved to be fantastic
Despite the lower overall level of assist, we were surprised that the battery proved good for almost 30 miles of riding when using the power sparingly. Riding more powerful bikes most of the time, we found this setup surprisingly enjoyable.
There were a couple of rides where we left it on Rocket the entire ride, and we still made almost 15 miles with almost 2000 feet of climbing. In Rocket mode, interestingly, when you are pedaling under assist then stop, the motor system continues for a second, which offers its own freewheel internally—a loud set of pawls that can be heard before the rear cassette’s freewheel is engaged.
The Nobby Nic tires are precise and offer good grip, even with a relatively narrow 2.35-inch width by today’s standards. With the 29-inch wheels, the angle of attack is better than a 27.5-plus-inch tire for getting over obstacles. The 120mm of travel was plenty for the type of riding this bike is meant for. We weren’t doing any really rocky, technical descents and the bike handled really well. The geometry is good, and because of the lightweight, it was so easy to throw around.
We spent more time riding this bike than we do a typical bike for review. It was that level of fun. It was the light weight and low levels of assist that make it a complete riot to ride. The Fazua motor is perfect for stronger XC riders who want less assistance than other motor manufacturers and like having zero motor drag when not using assist. If you like going on long rides, we’d definitely recommend springing for the extra battery. Even if you don’t take it on a ride, you can always have one fully charged and ready to go at any time.
BULLS WILD FLOW EVO SL
Motor: Fazua Evation, 250W mid-drive
Battery: Fazua 36V Li-ion, 7 Ah/250 Wh
Charge time: 3-3.5 hours
Top speed: 20 mph
Range: 15-30 miles
Drive: Shimano Deore XT, 1×11, 11-46T
Brakes: Magura MT5 hydraulic disc, 180/180mm
Fork: Fox 34 Float Rhythm, 120mm
Rear shock: Fox Float DPS, 120mm
Frame: Carbon front triangle, aluminum rear.
Tires: Schwalbe Nobby Nic 29×2.35”
Weight: 42 lb.
Color choice: Dark grey
Sizes: 44cm, 48cm, 54cm
Mountain Bike Action is a monthly magazine devoted to all things mountain biking (yes, that’s 12 times a year because we never take a month off of mountain biking). It has been around since 1986 and we’re still having fun.