-160-millimeter front and rear travel
-Aluminum frame only
-Shimano E7000 motor, or EP-8 on higher-end model
-Familiar, nimble geometry
-Supportive suspension on the descents
-Supple suspension on the climbs
-Limited range of 504WH battery
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I love it when I can’t decide where to start when I’m writing about a bike. When I think about the Polygon Mt. Bromo, so many compelling bullet points rush to the doors at once. There’s geometry. There’s suspension design. There’s spec and there’s value. Oh, and there’s the fact that this is an e-bike. So, let’s all just calm down and take this one step at a time. I’m going to start with value, perhaps to the chagrin of Polygon.
I say “chagrin” not just because it was on my word-a-day calendar this morning, but because Polygon would probably rather not be known as a budget bike manufacturer. They’re way more than that. Alongside their sister brand, Marin, Polygon just happens to own their own factories in Indonesia. That makes it easy for them to offer good bikes at a good value. It cuts out the middleman that the majority of brands deal with, and also makes them more maneuverable. Hold on to the potential for puns in the word “maneuverable” for a minute while I talk about the company’s maneuverability. E-bikes take a long time to develop, so you often see them released with outdated geometry. But every single number on Mt. Bromo could go toe to toe with any modern 29-inch enduro bike, e- or not. The 64.5-degree head angle perfectly suits the matched 160mm front and rear travel. And the 490mm reach on a size large frame is almost too big, meaning it’s exactly right. That size large can also bury a 200mm dropper post to the collar. There aren’t enough OEM-priced 200mm droppers out there, so I’ll forgive Polygon for speccing a 170, but chances are, you can run a dropper that’s one size up from what you normally would.
The most exciting number, though, is the 435mm chainstay. Rear-center length is a main frontier in e-bike design. When you put a motor around a part of the bike that once just had a bearing, it takes up a lot of space. Long chainstays are fine, but they make e-bikes feel … well, like e-bikes. They make it harder to maneuver and harder to get the front wheel off the ground. That’s why it’s so cool to see the attention Polygon paid to that part of the bike. In fact, they designed the entire suspension design around it.
Independent Floating Suspension or “IFS” is the acronym of choice for this new design. It essentially uses a dual-link design to put the pivots well above the motor and chainring without resulting in any strange anti-squat values. In fact, it isolates suspension forces from drivetrain input as well as a perfectly executed DW Link bike from Ibis or Pivot. That’s especially rad on an e-bike, when you’re going to be attacking technical climbs you wouldn’t on a traditional bike. Climbs where any hang-ups are going to be more severe and more frequent. I had none on the Mt. Bromo. That design also allows the rear wheel to be tucked right against the motor and still leave room for 2.6-inch tires. The seatstays then actuate the shock through a swing link. The forces against the shock were designed around hot new buzz term of a “straight progressive leverage curve,” meaning there’s a firm platform throughout the entire stroke. That’s important when the shock has to hold up the weight of the battery and motor. Then, there’s a steeper ramp-up before bottom out to keep them from falling through the last bit of travel in hard hits. It pairs well with the short chainstays, and I found myself having no trouble getting the Mt. Bromo off the ground and popping in and out of corners.
But that’s all relative. This is not one of the new breeds of ultra-light e-bikes. There’s no carbon version, no trail build. It’s not using a custom battery or a gravel bike motor. Although the higher-end N8 build comes with Shimano’s new EP8 motor, I wanted to test the lower-priced N7 with the slightly lower-torque, very slightly higher-weight E7000 motor. Most of the rest of the upgrades to the N8 won’t save significant mass, so you can expect this to be an over-55-pound bike. That’s with the lower-capacity 504-watt-hour Shimano battery. That battery was a bit of an odd choice. As is, the Mt. Bromo will only be meant for short loops. The weight meant the Eco mode was nearly useless, and the Trail mode, even maxed out to its highest assist level through Shimano’s app, felt a little pedestrian. With enough Boost mode mixed in, I usually maxed out about a 3,000 feet of ascending.
Although the geometry is familiar and well suited for the bike’s platform, the weight kept reminding me I had to ride the bike differently. It took a split second more planning, and ideally, a bit more traction to quickly toss it around. If it’s extremely important to you that an e-bike ride just like your traditional bike, this will not do it. But the thing is, you’ll be spending three times the price of this bike if you want one that does.
$4,400. That is one of the least-expensive full-suspension e-bikes out there from a major brand. And it didn’t get that affordable by being grandfathered in as a five-year-old model that has long paid for the tooling behind its design and manufacturing. Every aspect of the Mt. Bromo’s design was meant to resist compromise and keep up with those bikes that are three times its price. I did lament the underpowered 400-series Shimano brakes, but besides wishing for some lighter, more supple trail-oriented tires, that’s the only real shortfall in the spec. And for $6,000, you get that higher-powered EP8 motor, a Fox 38 fork and a mostly XT build. That’s my favorite of the many exciting things about this bike. Like it or not, e-bikes are getting more people onto the mountain, and bikes like this are lowering the barrier to entry and ensuring people have a better time when they get in.
Find it at polygon.com/mountain-ebike