- Premium hardtail electric fat bike with all the fixins, highlights include rear rack bosses, tubeless-ready tires and punched out rims, RockShox air fork with remote lockout and high torque Bosch CX motor
- Quality 180 mm hydraulic disc brakes from Shimano for excellent stopping power and modulation, impressive light weight for such a large electric bike at ~52.5 lbs, quick release rear wheel and removable battery to reduce further
- Available in two frame sizes for improved rider fit, angled top tube lowers stand over height but classic diamond frame is still stiff, strong and compatible with many hang-style racks (especially with the battery off)
- Would be nice if the front wheel was also quick release but the 15 mm thru axle is nice for improved handling and strength, no throttle mode for help managing those precarious moments in deep sand or snow but that keeps it Class 1
$0 (0 €)$18,000 (16,920 €)
0 lbs (0 kg)220 lbs (100 kg)
0 mph (0.0 km/hr)50 mph (80.5 km/hr)
0 watt3,000 watt
0 in (0.00 cm)22 in (55.88 cm)
0 Newton meters250 Nm
Fat tire electric bikes have grown in popularity over the past few years and mainstream brands have taken note. At least one major company introduced a mid-drive powered fat bike with front suspension during the 2015 / 2016 season but the Bulls Monster E S is the only model I’m aware of that’s powered by Bosch and available in the US. This ebike uses the CX variant of the second generation Bosch Centerdrive which offers more torque, a faster response time and a nicer interface than the other system I’ve tested… some of this is my opinion of course but features like display removability, integrated Micro USB charging and forward compatibility with larger batteries (namely the new Bosch Powerpack 500) make it a standout against Yamaha, Brose and Impulse. This performance however, is reflected in the price.
The Monster ES costs ~$4,300 which stings for many mainstream consumers but to be honest, I think it’s priced well. You get a near complete upgrade on all of the components, two frame size options, a two year comprehensive warranty and a fat bike that’s relatively light weight made from high grade Aluminum alloy. My favorite part is the rack interface at the rear, there are four threaded eyelets for adding a cargo rack which transforms this beast into a “go anywhere” commuter. Sand, snow, rain or shine won’t stop this bike and weather / terrain aside… larger riders might feel that the aesthetic suits their presence and build more than smaller bikes. I love that the bright accents aren’t overdone but that the bike offers some color and fun. It’s a cool looking bike with a battery and motor that match the color scheme and are mounted in a way that sort of blends with the frame and tires. There’s also a tough aluminum skid plat bolted to the bottom of the motor, protecting it from rocks and other obstacles you might encounter on adventurous rides.
Perhaps my only gripes with this electric fat bike, aside from the price tag, are the lack of quick release on the front wheel, basic rubber grips that don’t lock and the limited availability at dealers right now. Bulls is relatively new to the US market and while they’ve expanded into roughly 20 dealers at the time of this review, it’s not a bike that everyone is going to be able to find locally and take out for a test ride. Take note however, brands like Bosch only partner with companies they trust and Bulls has been accepted in Europe and parts of Asia, selling ebikes for several years now. Some of the premium parts used on this model include Shimano hydraulic disc brakes (both large 180 mm) with ICE Technology rotors meant to dissipate heat, an 11 speed Shimano Deore XT drivetrain and RockShox Bluto air suspension fork with remote lockout. A couple of areas I think could be improved by Bosch include adding a battery percentage readout on their display and perhaps higher power output on the USB port built into the display so that phones and some other portable electronic devices could be charged and not just maintained when plugged in.
Overall, it’s a bike that gets the job done with instantaneous feedback from pedal assist that measures wheel speed, pedal cadence and pedal torque 100 times per second. The chainring is extra small with just 15 teeth for improved torque and climbing power. The motor spins that chainring roughly twice as fast as the cranks rotate and this produces a natural feel while pedaling while empowering to motor to operate efficiently. It starts and stops super fast but there is a bit of an electronic whine or whir produced when pedaling at higher RPM. It’s something you see (or hear) with all of the current Bosch e-bikes. In optimal conditions (flat pavement with a ~160 lb rider using Eco mode) you should be able to reach up to 60 miles per charge with the standard 400 watt hour pack or you can pay more for the newer 500 watt hour and go ~25% further. Both batteries look the same and are removable to reduce frame weight if you’re transporting the bike. I do appreciate the traditional, stiff triangular frame (which hangs on many car racks easily) but it presents a higher stand-over height so it’s cool that the top tube is angled down to take that into account and shave off an inch or two for people with shorter legs. Cables and electrical wires are all internally routed for protection and a nicer look as you see with more expensive models.
I took the bike into sand (both soft and firm) and it performed well when I let some air out of the tires. Again, these are higher-end Schwalbe tires with a layer of puncture protection and the ability to be run tubeless to reduce weight. So the bike stood up to the challenges of riding in sand but it did kick some up onto my legs a bit (no fenders), the 100 mm air fork suspension took the edge off of the bumpy parts and I was able to steer alright. It’s amazing how much help you’re getting from an electric assist bike… having ridden bikes like this without power on sand, it’s nearly impossible. The only question mark in truly rigorous terrain like this is the lack of throttle because there are times when it’s nice to just get help starting from rest or power through a difficult section without worrying about shifting gears. Most mid-drive electric bicycles just don’t offer throttle mode. This is a Class 1 electric bike that will be legal in more locations (like mountain bike trails) but without the throttle there’s a bit more balancing and work to be done. Rest assured however, it’s very possible and quite enjoyable. Another consideration with fat bikes is that if you’re spending this kind of money for a bike and then actually ride it near the ocean with salt water there may be corrosion and rust happening, especially if you don’t rinse it immediately after each ride. I wrote a guide about this here and included some pictures and feedback from a hardcore rider in Europe who uses a Bosch powered bike. So the way I’d approach this thing is as a weekend warrior where there’s a rack for hauling, a good drive system delivering excellent climbing and range, a nice suspension setup and fun off-road capable tires that could be enjoyed on the weekends and taken care of on those special beach or salty snow days. It’s just something I’d baby a little because it’s so capable and can really last if you do. Big thanks to Bulls for partnering with me for this review.
- Robust drive system with additional protective metal paneling below the motor, offers 75 Newton meters of peak torque output for excellent climbing or slogging (the Bosch CX offers 15 more Nm than the standard Bosch Performance line)
- In addition to the metal push guard, there’s an oversized alloy chain guard protecting the chainring and keeping your chain from bouncing off on bumpy terrain, an extra-large rubber slap guard protecting the chainstay and I like that you get metal pedals but would probably upgrade from the cages to a Wellgo platform like this for increased surface area and traction
- Name brand tires from Schwalbe, the Jumbo Jim model offers “Snakeskin” puncture protection and can be run tubeless for decreased weight and improved low-pressure performance, the punched out rims reduce weight and look cool
- Awesome suspension setup… you get a RockShox Bluto air fork with remote lockout, 100 millimeters of travel performance and a 15 mm thru-axle for strength
- Great utility potential with this bike given the seat stay bosses so you could add a rack and fit a trunk bag or panniers, make sure to get a fat bike rack that is disc brake ready like this
- The bike is available in two frame sizes for improved fit whether you’re tall or short, the top tube is angled down for lowered standover height, reinforced seat tube bumps up for strength and would work well with a 30.9 mm thudbuster to improve comfort (long or short travel would work), nice name brand Selle Royal saddle that’s color matched to the bike
- Motor and battery weight are kept low and center for improved handling and I love that the controller provides shift sensing feedback to spare the chain and sprockets if you’re shifting under load (extra important off-road or in soft environments with hard pedaling, especially given that this bike has 11 speeds)
- The battery can be charged on or off the frame and I like how it blends in with the black frame and is designed into the downtube with a little cup at the bottom, the Bosch system is forward compatible with the new 500 watt hour pack but comes with the 400 watt pack standard here
- I was really impressed by the weight of this bike at ~52.5 lbs, yes I was on the smaller frame size but that’s still good for a fat-ebike and I attribute it to the nicer components, premium frame and air fork
- The price point also wowed me considering the nicer components and solid two year warranty (with five on the frame) at ~$4,300 it’s a very complete package including 180 mm hydraulic disc brakes with XT rotors from Shimano
- The Bosch Intuvia display panel is intuitive to use, large and easy to read, backlit for use at night, it includes a Micro USB charging port on the right side for maintaining a phone or charging a headlight (or other portable electronic device) and it’s completely removable! I love that there’s also a button pad break out box positioned near the left grip for adjusting power and readouts on the fly without taking your hand off
- The Bosch Centerdrive is one of my favorite ebike motor systems because it’s efficient and durable but it does not offer a throttle mode (that keeps the bike a Class 1 here), the downside is that sometimes on snow and sand it’s nice to have extra help when you can’t pedal easily (something a Class 2 would offer)
- No bottle cage bosses on the seat tube… it looks like there might be room but given the up-release battery design that Bosch offers maybe it would be a tight fit, at least you have the option for adding a rack
- No quick release on the front wheel… just the back, that makes transporting and flat fixes a bit more time consuming
- Given the larger, heavier wheels and tires used on this and most fat bikes, I was surprised that the rear wheel wasn’t using a 12 mm thru-axle… just a standard 11 mm skewer
- The grips work alright but aren’t locking so they can spin easier if you really bear down or get them wet or hot riding, cheap to upgrade but given the price of this bike kind of a low point
- One area I really feel like the Bosch system could be improved is with the display panel because it only shows five battery bars vs. an actual percentage estimate (or more bars), there’s a big difference between 20% remaining and empty when you’ve got a bike this big to haul back home
- The second generation Bosch mid-drive (that the CX is built on) produces a distinct whine because the sprocket spins at about 2x pedal rotation… this makes it super responsive but that noise is more noticeable than the Brose and some Impulse 2 motors (or even Yamaha)