2017 CUBE Reaction Hybrid HPA SL 500 Review


Technical Specs & Ratings



Reaction Hybrid HPA SL 500


Class 1


Front Suspension



Hydraulic Disc



482.4 Wh

482.4 Wh

48 lbs / 21.79 kgs


FSA 1.5E ZS, Tapered, Top Zero-Stack 1-1/8" (OD 44 mm), Bottom Zero-Stack 1-1/2" (OD 56 mm), Threadless, Internal Cups

CUBE Performance Pro, 85 mm Length, 5° Angle, Three 10 mm Risers, 31.8 mm Clamp

CUBE Rise Trail Bar Pro, 720 mm Length

CUBE Performance Grip, Rubber, Flat

CUBE Performance Post, Alloy


CUBE Branded, Selle Royal MTB

Hydraulic Disc

Shimano Deore BR-M615 Hydraulic Disc with 180 mm Rotors, Shimano Two-Finger Levers with Adjustable Reach


More Details

Video Reviews

Written Reviews

The CUBE Reaction Hybrid HPA SL 500 is a hardtail electric trail bike that seems uniquely well suited to urban environments. With a 100 mm travel air suspension fork from RockShox, offering remote lockout, you’re not going to experience efficiency loss from bobbing or sluggish steering from a steep head tube angle as you would with most other trail models that have smaller wheels and different forks. Transitioning from street to trail is a breeze, you don’t have to reach down and tinker with a compression clicker, just pull the lock lever and the rigid fork becomes supple. Large 29″ wheels with 2.35″ wide tires offer a lower attack angle that spans cracks and gives you forward momentum. This isn’t so much a quick twitchy bike as it is a solid, smooth, momentum type bike. Interestingly though, the two smallest frame sizes come with 27.5″ wheels… and that’s meant to bring the stand over height down and provide a similar experience for petite riders. The Reaction Hybrid comes in six different frame sizes! That’s amazing to me, but it could be the deciding factor for a young rider or extra-tall adult. Fit is a big deal when you’re riding further and enduring rugged terrain. Again, this is a cross country setup meant for packed Earth vs. rocky rutty terrain. The hardtail design isn’t going to be as comfortable, but it does provide an excellent platform for mounting a rack with trunk bag and panniers. Make sure, if you go this route, to get a disc brake compatible rack like this. And, depending on your ride plans, many Bosch Certified electric bike shops can even wire in lights that will run off of the main ebike battery. Motostrano can do this, and I met with the owner, Joe Witherspoon, to conduct this review. He was actually preparing to do a 50+ mile ride going from roads to a trail and then camping. They chose this model (and similar hardtail units from CUBE) because of the efficient but powerful motor, sturdy frame design, stable cargo platform (racks), and widely available Bosch battery packs (because they had extras laying around from other bikes that could be swapped-in for long distance riding.

Driving this e-bike is one of the best mid-motors available on the market today, in my opinion. The Bosch Performance Line CX is a mountain specific drive unit that ranges from 250 watts to 570 watts peak, offering up to 75 Newton meters of torque. It’s extremely responsive, measuring rear wheel speed, pedal cadence, and pedal torque, over 1,000 times per second. And, it uses a smaller chainring with reduction gearing to improve grab and increase mechanical advantage. In practice, this motor in particular is a bit louder than the other Bosch units. You can hear it whining at the higher RPM levels and especially at the highest power level. That said, it actually supports you at up to 120 RPM while most other drive unites I have tested fall short. For someone like me who has a knee injury and likes to spin vs. slow and steady, this motor is a winner. There is some pedal friction produced by the reduction gearing, as the chainring spins 2.5x for every crank arm revolution, but that hasn’t stopped me from pedaling beyond the max assisted speed of 20 mph. Note the alloy chainring protector that doubles as a guide. And, not also the 11-speed drivetrain with higher specced Shimano Deore XT derailleur. This derailleur offers a one way clutch, a little grey lever that can click into an up or forward position. The up position increases tension which reduces chain bounce and chain suck (if you get the chainring really muddy and it starts to grab the chain and suck it upwards). Protecting the sensitive parts of your drivetrain becomes more relevant when using a centerdrive motor because it exerts force into the same chain, sprockets, and derailleur as you… but might not be as smart as you. Well, in my experience, the Bosch controller is one of the most responsive and proactive unit around. While it doesn’t offer physical shift sensing like the older Impulse motors or some BBS02 kits from E-RAD, it does use software driven “shift detection” which sounds like micro-gaps in power. When these gaps are presented during shifts, the chain can jump easier and maybe not wear out your components. This said, it’s still advisable to ease back when pedaling, reduce the torque signal to the controller to manually reduce strain.

Powering the Reaction Hybrid HPA SL 500 is… you guessed it, a 500 watt hour battery. This is Bosch’s newest Powerpack, which only weighs 0.3 lbs more than the older Powerpack 400 but offers 25% more power and fits into the same physical casing. It’s backwards compatible in fact, and that’s what I meant earlier about bringing extra packs. If you already own a Bosch powered electric bike, maybe a city model, and you buy the Reaction here for going off-road a bit, your battery packs would be interchangeable. So anyway, I absolutely love the way this e-bike looks and part of the beauty is in how they positioned the battery. Not only is it low and center on the frame, but it’s extra low and partially inset. The Aluminum downtube cups the pack, offering some physical protection, and is painted to blend in with the black plastic casing. Same situation down at the motor, and the motor is also blended into the frame and tipped up to maximize ground clearance. Whether you decide to park your bike near an outlet and charge without removing or take the battery off and store in a cool, dry environment (for best longevity) the battery charger uses the same plug type and offers a fast 4 Amps of power output. The charger weighs less than two pounds, so it’s also easy to toss into a bag for longer rides or commuting. You can easily tell roughly how full the battery packs are because Bosch has built-in an LED charge level indicator on the left side of the pack. And this uses a five bar readout for 20% increments, which is good enough for the battery but a bit less precise than I would have wanted for the display.

And on to the display, it too has a 5-bar battery infographic which leaves something to be desired when you drop down to the last tick. Do I have 20%? or am I down to 3%? Who knows… and who knows why Bosch didn’t go with a ten bar readout or maybe a percentage number as they have with their fancier Nyon display panel. The small Purion display is what you get with the CUBE Reaction Hybrid HPA SL 500 and it tends to be less vulnerable to damage if the bike tips or crashes, but is not as easy to interact with, and is not removable like the Intuvia. It also does not have an active Micro-USB charging port (just a diagnostics software update port). For those who wish to upgrade, select shops can order the Intuvia and install manually. The most important features are still there however, such as current speed, current assist level (Off, Eco, Standard, Sport, Turbo) and range. You have to hold the minus key to cycle through trip stats like ride distance, total distance (odometer) and range… but it’s worth it, because you get more detail about how far the bike might go in each level of assist and based on remaining battery and your last mile of riding. It’s very dynamic and handy, I have made the call to switch from Sport to Standard on a few occasions just to be sure that I could make it back to the car without running low on battery power. And now, as of 2017, there’s a software update to convert the Sport mode to EMTB mode on Bosch CX equipped models. This new mode offers a full range of power that gets activated based on how hard you are pushing (in addition to the other signals), it’s more like a torque sensor, and this frees up your hand and focus to navigate varied trail terrain. It works well, they clearly tested this a lot so that it wouldn’t overpower you or make you feel like you’re working harder than you want. Seriously, this is difficult to get right and I have had some lackluster experiences with some other torque sensors like the TMM4 strain sensor that some companies use. In short, the display does a good enough job and blends in nicely… furthering the stealthy look of this electric assist mountain bike.

CUBE is a European brand with only a handful of dealers in the US and Canada right now, but they do a great job with style, quality, and value in my opinion. This model isn’t particularly affordable at $3.8k, but it’s just one of many in their wide range of skews. You can opt for a lower-end drivetrain, lower capacity battery pack, less-fancy fork etc. etc. and the color schemes do change. Thankfully, many of their bikes come in several sizes, and that means you can find a fit for your body and your budget. A couple of extra quick-tips I wanted to share about the display is that you can press the walk mode butt and then hold plus to have the bike move itself forward. This is particularly handy if you’ve got a loaded rack and have to dismount for a technical or steep section of trail. You can hold the minus button and tap the power button to switch from kilometers to miles. And, if you work with your shop to add lights (if you’re into early or late commuting or trail rides) you can hold the plus button to activate them through the display. Yes, the Purion is fairly capable, but it does not show you a clock, trip time, max speed, average speed, or shift recommendation arrows and I have found that it functions best when pressing the + and – keys near the edge of the display vs. down low near the bar mount. CUBE went the extra mile with their paint job and matching hardware here, and they also try to protect it with one of the nicest slap guards I have ever seen (protecting the top and bottom of the right chain stay and matching the paint color) as well as a clear plastic sticker along the bottom of the downtube to prevent chips and nicks in the paint. Big thanks to CUBE for partnering with me on this review, and to Motostrano for letting me review one of their demo bikes and even taking a test ride with me! I have to admit, there are times where I make a purchase decision purely based on looks, and this particular color scheme and frame design has me wanting. It’s easy to love because I trust Bosch and feel that the product would hold its value, be serviced well, and have batteries and parts available for many years down the road.


  • I love the aesthetics of this bike… matte black with gloss accents and branding, angled motor integration for shorter chain stay and higher clearance, semi-integrated battery pack, internally routed cables, beefy 29″ tires
  • Notice how the hubs, spokes, and even the Alex rims are black with minimalist grey accents, they complete the look and make the tires look bigger than they are, also, the rims use reinforcement eyelets for improved strength
  • One of the nicest slap guards I have ever seen, it matches the paint job perfectly and does’t protrude and won’t come off like a neoprene+velcro guard, it’s rubber and thicker than the clear sticker guards and it wraps the top and bottom so you get more chain stay protection
  • Bottle cage bosses and rear rack bosses, so you can bring fluids, accessories like pumps or folding locks, and even load this up with a trunk bag or panniers for multi-terrain commuting without having to wear a backpack
  • Excellent drivetrain, the Shimano Deore Shadow Plus is great for trail riding because it offers eleven speeds to climb with and has a one way clutch (the little grey lever) which tightens the chain when in the up position, this reduces chain bounce and chain suck if you’re in muddy terrain
  • Great brakes, you get Shimano hydraulic disc brakes with adjustable-reach levers for those who have smaller hands or wear gloves, considering that this ebike comes in six frame sizes… it might be supporting a younger rider or someone who is just petite and I think it would do a great job accommodating them
  • CUBE didn’t just make six frame sizes and stop there, the two smallest frame sizes (16″ and 17″) come with smaller diameter wheels at 27.5″ vs. the 29ers on the larger models, this brings the entire bike down closer to the ground so shorter riders can still get a cross-country feel for their body size
  • Both wheels offer quick release for easy trail maintenance and portability, same with the battery pack, it’s easily removable and can be charged on or off the frame, given that it weighs ~5.7 lbs, I usually take the pack off when transporting bikes by car rack or even just lifting them
  • To me, this would be a great urban platform because it offers large efficient wheels and a cross country fork with limited 100 mm travel and remote lockout, you can easily transition from packed trails to urban streets and paths, or if you spend most of the time on pavement you could swap out the tires for some 29er slicks like these Schwalbe Big Apple 29″ x 2″
  • The chainring has a black alloy chainring guard to keep your pants from snagging and also prevent the chain from bouncing off track as easily, some other bikes use a plastic guard which just doesn’t seem as tough
  • There are lots of Bosch certified dealers in the US that can provide warranty support and you get a comprehensive two year warranty on the motor, battery, display which is above average… they should last well if you take care of them, and many shops know how to wire-in lights so you can run them right off of the battery pack
  • There was a software update in 2017 which activated EMTB mode, basically turning the Sport level (second highest) into a full-range torque sensor, so you can ride in one assist level and get power feedback based on how hard you are pushing, it’s great for mountain biking where you need to stay focused on the trail vs. clicking buttons
  • The battery pack mount works with the older Bosch Powerpack 400 and the design of the cases for both this and the new Powerpack 500 are just so well done, you have an integrated loop handle at the top for secure carrying and there’s an LED charge level indicator built into the left side so you can know how full it is even off the bike
  • It sounds like most CUBE electric bicycles that run with Bosch motors can have walk mode enabled, and this can be useful if you go off-road and decide to walk and push your bike through a particularly rough section, some other brands have disabled this
  • I noticed a mounting point towards the end of the left chain stay and Joe explained that there’s a CUBE kickstand that could be added to this bike, that’s awesome for those who do plan to spend most of their time in an urban environment and don’t want to lean their bike against a wall constantly, most mountain bikers take them off to reduce rattling and snags


  • The Bosch Performance Line CX motor is responsive and powerful, but it’s also the loudest motor in their lineup, you may notice a high pitched whine when operating the highest levels of assist or spinning faster, but this is usually mostly obscured by the sound of the knobby tires on off-road terrain
  • Notice the smaller chainring, it rotates at 2.5x for every crank arm revolution which means there is increased pedal friction, it doesn’t create drag when coasting, but you will work slightly harder when pedaling on a Bosch motor like this than with some of the competition that uses standard sized chainrings
  • Even though I feel that the battery and motor integration are very well done here, this is still less stealthy than fully integrated batteries and some of the newest super-compact motors, for those who don’t want to be noticed at all, it could be a drawback… but it’s about as good as you can get with the Bosch Powerpacks, keep an eye out for the Powertube integrated battery in 2018
  • Bosch makes several displays and the Purion is their most compact, but it lacks a few readouts and doesn’t have a dedicated i button to cycle through menus, you have to hold the minus key instead, which is slower
  • The Micro-USB port on the display does not allow for charging, just software updates, and this display is also not removable like it’s bigger brothers, the Intuvia and Nyon (which is only available in Europe right now)
  • To me, CUBE is a high-quality but value-driven brand and I was surprised to learn that the Reaction Hybrid HPA SL 500 is priced at roughly $3,800 because that’s the upper end for an alloy hardtail, but the styling is there and you get an air fork and the larger battery… so I guess it makes sense ;)

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