Enter the Plow King - Polygon's Crazy Six-Bar Mt Bromo eMTB Review

A bump gobbler with a complex suspension system.





E-Bikes. They cost more, weigh more, and are evolving at a pace that is far more rapid than mountain bikes. Polygon has decided to jump into the e-waters with both wheels. Not only is this the brand's first full-suspension offering, they are doing so with an all-new suspension platform dubbed Independent Floating Suspension (IFS). Polygon says its new bike offers and "enduroesque" ride experience. We say that's a bit like cutting your birthday cake with a chainsaw. Hang on, because things are about to get rowdy.

 


Highlights

  • Aluminum frame
  • 29-inch wheels
  • 160mm (6.3-inches) of rear wheel travel // 160mm (6.3-inches) fork travel
  • IFS 6-Bar suspension design
  • Internal cable routing
  • Shimano EP8 Motor - 85Nm torque (tested)
  • 504wh battery
  • Small through X-Large frame sizes
  • ISCG05 mounts - e*thirteen E-spec top guide included
  • Boost 148 rear spacing with 12mm through axle
  • Measured weight (size medium, no pedals): 54 pounds 3 oz / 24.57kg
  • MSRP $5,999 USD (tested)
     





Polygon offers the Mt Bromo in two trims, the N7 and N8. Both offerings have the same aluminum frame and use 29-inch wheels. Polygon does not recommend running a 27.5-inch rear wheel, even with a 2.8-inch tire. They say the bikes will work with a coil but are specced with FOX air shocks (DPS or Float X2) which are said to be tuned specifically for the bike. The 504wh battery can be removed via a 4mm Allen wrench and a release lever. Riders cannot fit a larger battery into the frame, but additional batteries are available for purchase.



Geometry

Polygon makes use of some fairly aggressive geometry on the Mt Bromo with a hearty 470mm reach on our medium test bike. Large frames jump to a 490mm reach. Regardless of size, the backend stays the same with 435mm chainstays throughout all sizes. The 70-degree seat angle translates to a 77-degree effective seat angle, per Polygon. A 64.5-degree head angle rounds out the key points.





We jumped on the Mt Bromo completely blind, not knowing a single statistic or figure, just that we had a medium. Despite being at the large end for typical reach numbers in this size, the bike did feel comfortable at first-take. The steeper seat tube angle was noticeable, and was more than likely the reason our bike felt comfy while pedaling.


Polygon Mt Bromo Anti Squat and Anti Rise Values

 


Polygon Mt Bromo Axle Path


 

Setup


We've found that we like to run our e-bikes with stiffer suspension than our mountain bikes. The additional mass of the bike and, generally, its propensity for hammering down hills call for a firmer arrangement. The rear shock was set to 190psi, giving our 170-pound tester 20% sag. The FOX 38 was set up with 100psi. Knowing our test track and the conditions, this setup mirrored what we used in our e-bike Test Session.




 

We set up our tires just for the day of riding at hand. In this case, dry, very loose (bordering on sandy) trails. Reveling in Schwalbe's Super Gravity casing 29x2.6-inch tires, we took the pressure down to the low 20's. The dual Magic Mary tires act almost as cut-spike tires and are a joy in the soft stuff.

Our Mt Bromo was not light, not by any measure we could discern from picking it out of the back of the truck at least. Knowing we were heading into the mouth of the beast (steep climb) we only messed with Trail mode for a little while before bumping the Shimano EP8 motor to Boost mode, where it lived for the day. The pull of the EP8 felt strong, even with the hearty, 1370g, Schwalbe tires.
 


The Lineup


Polygon offers the Mt Bromo in two builds, which are quite different from one another. Both the N8 (tested) and the N7 use 29-inch wheels, have 160mm of travel and feature 504wh batteries. Unlike our test bike though, the $4,399 N7 is a lower-powered and lighter-duty Shimano E7000 motor with 60Nm of torque, instead of the 85Nm on the EP8. The fork on the N7 downsizes from the FOX 38 to a Suntour Duroloux 36. Finally, the rear shock makes a dramatic step down to a FOX DPS Evol from the FOX Float X2 on our N8.





There are other small steps down in the drivetrain, brakes and wheels of the N7 as well. Riders will save a fair bit of coin with a retail of $4,399 on the Mt Bromo N7 compared to the $5,999 of our N8 test bike.
 

On The Trail
 

Spring conditions were in effect for our outing with the Mt Bromo. The day was crisp and clear, while the moto trail was dry and loose. When we need to make a quick shakedown with a bike, we make haste for the same network of moto trails that we used for our initial e-bike group test. It's a nice baseline from which to consistently suss out a bike's nature and e-bikes are allowed there.





Heading up the hill was a non-event. Polygon says they developed the IFS platform to climb in what they call the power zone -- the area where the anti-squat value is above 95%. Inside this zone the suspension will remain active and will not be adversely affected by pedaling force. From 0mm to 110mm travel (small to mid-sized bumps), the rider will able to be pedal full-gas while having the benefit and traction of active suspension. Putting the bike in Boost made the climb disappear with our motor feeling extra powerful. Just to make sure we weren't fooling ourselves, our test rider and videographer exchanged e-bikes (Canyon Torque:ON) with the same motor and battery size, both on Boost, using identical power and assist profiles. The Polygon took less effort to scoot up the hill -- not much, but noticeable. What we were unaware of was the trench we were digging for ourselves... More on that later.





Turning the Mt Bromo around and heading back down revealed an absolute monster. True, the Polygon may go up the hill with ease but the joy of this bike is blitzing the downs. We'll touch on the faults in a minute but out of the gate, the Mt Bromo is a bump-eating, trail-taming beast of an e-bike. We were genuinely surprised to later find out this bike only has 160mm of travel. When it comes to straight, fall-line riding where only nerves will slow you down, the Mt Bromo may be unmatched.




 

Trails usually have turns, the good ones do at least. This is where the rider needs to grab that monster by the horns and assert who is in charge. The Mt Bromo will turn, and turn well at high speeds, but as a rider, a firm hand is required. There is no place for subtlety here. We aren't installing thumb tacks with a hammer, tapping ever so lightly. No, we are lining up and one-timing that thing. This is how you turn the Mt Bromo, with authority and confidence.

Our test track doesn't have bike park jumps. It is riddled with sets of moto whoops that make for delightful doubles and triples. This was where the Mt Bromo just would not comply. Because trail features like this are about timing and subtlety, the Polygon is not up for the task. It was not a pop bike, it was a business machine and we would look to Polygon's Independent Floating Suspension (IFS) 6-bar design as the leading culprit here.




 

Early on, in lobbing off some lips down the hill, our return to Earth was met with a loud clack at the rear end. We gave it a few more rounds and found that we were burying our Float X2 shock all the way to the bottom of its travel and very firmly, finding its limit. At a mere 20% sag, this was surprising and definitely a first.

At the end of our testing and filming, our battery was on life support with just one, lonely red bar remaining. Again, we were pretty surprised by the Polygon. The Torque:ON our videographer used, also on Boost, had three bars of battery left. This was curious, as the Torque:ON also uses the smaller 504wh battery. In our POV footage, we noticed two bars showing on the display during our final descent before a short, but steep climb back to the truck. A full bar nuked on that last climb does not make us anxious to tackle a extended rides with any hint of Boost. We took the Mt Bromo out on some smaller excursions and found the battery to drain faster than other bikes we've tested. We aren't sure if our bike has a hot tune or a lackluster cell, but it's clear those Super Gravity casing tires take a whole lot more energy to spin. The battery life on our Polygon was below standards, per our experience.


Build Kit


FOX X2 Performance Elite Shock


Dear FOX, we are sorry for what we did to your shock...repeatedly. We were unaware the X2 could make such a definitive thud when hitting bottom. We appreciate the big-shock-that-could, despite our repeated violent hits, the X2 did not blow a gasket or seal. Bravo. The FOX 38 with minimal FIT GRIP damper was a bit of a spec hit, but it formed flawlessly.


Motor and Batteryv


We may have had too much wind in our ears or perhaps we've grown numb to it, but for some reason we did not notice the typical EP8 motor rattle.

A 504wh battery is considered small these days (versus 630wh or even bigger), and it was a choice that Polygon willingly made. They cited the lower weight and smaller size of the 504wh battery as a virtue. To then mate that with some of the heaviest tires on the market and such a heavy-hitting spec seems counter-intuitive to us. We griped about the Santa Cruz Heckler having a short battery life but the Polygon takes the cake. Like so much in life, the best times are fleeting. Riders will need to learn battery management skills to get the most out of their day with the Mt Bromo.


Long-Term Durability


Polygon is launching a new suspension platform with the Mt Bromo. This particular design has a whole lot going on, with plenty of pivots, subsequent bearings and linkages. We don't doubt the quality or craftsmanship here, not one bit, but that's a lot of action happening on a burly bike, capable of mowing down entire mountains.





Regardless of build quality, taking time to go through every bolt, pivot and bearing for regular maintenance is going to be a significant task and deep cleaning will not be easy. There was also one troubling area - the derailleur and rear brake line routing. When cycling the rear shock to show the linkage at work, we heard a squeak sound coming from the back of the bike. The brake and derailleur lines exit the top of the downtube and then route into the elevated chainstay. When the suspension is fully compressed, the chainstay slides across both the rear derailleur housing and the hydraulic brake hose. It's a constant motion as long as the suspension is moving and when dirt gets in there, the erosion will be real. Polygon has put a protective sticker under the chainstay, so they see it. The chainstay wearing thin isn't our worry, so wrapping the brake hose with some kind of protection should be done at a minimum.
 




Every part on our Mt Bromo is built to be durable. Not one component here has us stressed. There is a nice guard protecting the motor and plenty of nice touches like bumpers on the downtube and adequate frame protection. The fork bumpers are identical to what we saw on the Marin Alpine Trail E2, and through that test, we learned the adhesive that helps keep them secure should be monitored after wet rides or washes.



What's The Bottom Line?


Through our test, we received mixed messages about Polygon's new e-bike. On one hand, it has a small battery to save weight and a lower-spec model that runs a small motor, trail shock, and mid-sized fork. On the other hand, our test bike has downhill tires, burly suspension and a ride quality that is more like Grave Digger than Robby Gordon. The only flies in the ointment are the suspect battery life and potential vacation days needed to service the suspension in a meaningful way.

Our bottom line? The Polygon Mt Bromo is the hardest charging, fastest and confident rig we have ridden in recent memory. Forget your jibs, watch that battery life, and ride the trail like it was your last day on this rock.


Visit polygonbikes.com to learn more about the all-new Mt Bromo.


 


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