All-new Polygon Mt. Bromo eMTB throws large journey by way of 6-bar linkage suspension
Polygon’s first-ever full-suspension e-mountain bike takes a new approach to their linkage to deliver 160mm of rear wheel travel with 29er wheels and a really short chainstay. Combine that with modern geometry, a choice of Shimano EP8 or EP7 motors, and a big battery to make a big bike for big days.
With their analog mountain bikes, Polygon uses a more traditional four-bar linkage for their Siskyu, and the NAILD suspension for their wild-looking XQUAREONE bikes.
Named after a volcano in Polygon’s home country of Indonesia, the area inspired them not just in name, but also because this is where they test their mountain bikes.
Polygon Mt. Bromo eMTB tech details
Let’s look at the suspension first, because that’ really what sets this bike apart. By using a “6-Bar IFS” (for “Independent Floating Suspension”) linkage design plus an elevated chainstay, they were able to move all of the pivots above the motor housing while still keeping that weight really low on the bike.
Here’s how it works: The lower main pivot floats between two links, allowing it to move in space as opposed to having a fixed location on the bike.
As the rear axle moves upward in response to a bump, the bottom linkage moves up with it, which pushes the front link forward. We’ll have video of this in our review.
Combine that with Shimano’s motor’s already compact motor unit and they could get 435mm. That’s just 17.13″, which is really short for any 29er, full suspension or not.
To get a full 160mm of travel out of that without the wheel moving into contact with the frame, they gave a mostly vertical axle path. Put it all together and they say it gives you the nimble handling you need for precision technical riding and climbing, but all the travel and traction you want to rip the descents.
Polygon spec’d 29er wheels front and rear, trading the mixed wheel size trend for maximum roll over performance. It comes with 2.6″ tires front and rear for plenty of grip, too. While they say you could put a 27.5×2.8″ on the rear, any rubber gains would be negated by putting the BB in a precariously low position.
And that’s because the BB is already low, and the angles are already slack. The bike has a 64.5º head angle and pedal-friendly 77º seat angle. Bottom bracket height is 345mm. Here’s the full geometry chart:
A short offset fork adds a bit more trail longer for stability on the descents. This means they’re relying on the short rear end to keep it nimble, something we’re testing on the bike you see pictured here…stay tuned for a full review later this Spring.
Polygon Mt. Bromo specs & pricing
We’re testing the higher-end Mt. Bromo N8, which gets the EP8 motor and Fox Performance suspension. Here’s the highlights for both models:
N8 Spec overview
• Fox 38 Performance
• Fox Float X2
• Shimano STEPS EP8, 85Nm, 504Wh
• Shimano M8100 XT 12 Speed
N7 Spec overview
• SR Suntour Durolux
• Fox Float DPS
• Shimano STEPS E7000, 504Wh
• Shimano M6100 Deore 12 Speed
The motors assist up to 20mph (32km/h) for USA and Indonesian markets, and 25km/h in Europe and Australia. Range is estimated up to 60 miles (100km) per charge, but that’s with light use and mostly eco mode…expect about half that with more aggressive real-world use.
While the Fox 38 Performance fork doesn’t have the high/low speed compression adjustments of the Factory-level models, the GRIP damper still allows basic low-speed rebound compression adjustment.
The STEPS remote and Shimano’s dropper remote get close, but manage to clear each other and allow a good bit of position adjustment to fine tune the cockpit.
Considering the spec, Polygon’s bikes are a relative deal at $5,999 for the Bromo N8 and $4,399 for the Bromo N7. They’re available through BikesOnline for North American customers, or hit that link below for global info. Bikes are available for pre-order now and start delivery in July 2021.