Mongoose Vinson Fat Bike

The Mongoose Vinson is a Fat Bike similar to the Mongoose Dolomite and Hitch, although with some very useful improvements, the most obvious being frame weight reduction due to the use of aircraft-quality Aluminum alloy, reducing the mass by a good 10 lbs. when compared to either the Dolomite of the Hitch. It also makes for a much more solid and responsive bike. In fact, fully converted with battery, the total bike weight is less than 76 lbs.

Improvements also include better groupset: The Derailleur and shifters are SRAM X-4, with a 3X8 gear configuration as opposed to the Dolomite’s 1X7 Gear drivetrain, and grip shifter. The disc brake calipers are better quality, and the paint job is tougher than the lower cost Dolomite and Hitch bikes. Overall, we were quite pleased with the quality of the base bike, even though the cost was a few hundred dollars higher than the Dolomite and the Hitch. In our opinion, this was money well spent.

We were not content to just add the electric kit, however, and did make a few upgrades to the frame. These included:

  • Shimano M355 hydraulic disc brake levers & calipers, with an Avid Cleansweep 200mm rotor for the front and 180mm rotor on the rear
  • DNP 7-speed 11T-28T freewheel (For better pedaling ability at cruising speeds)
  • Headset replaced with a solid-feeling FSA "The Pig" DH Pro
  • Likewise with the Stem to the super-strong Truvativ Hussfelt Downhill

For the motor/electrical components, we opted for a higher speed winding on this fat bike, and decked it out with the highest power controller paired with a CA V3 to run the show. The Electrical/motor system consists of:

  • MXUS 3000W 5T Fat Bike motor (7.1Kv)
  • Xie Chang 18FET x 4110 65A Programmable controller (Overclocked to 70A)
  • 60V – 20Ah Triangle Lithium Battery (1.2KWh)
  • Cycle Analyst V3 display that can regulate the throttle, power and even protect the motor from overheating. (This was critical, since we wanted to run the 5T motor at 70A battery/150A Phase for burst power)

To accomplish this installation, we took detailed measurements of the bike’s rear drop-outs and developed custom Stainless Steel torque arms for this specific frame. Reason being that common universal torque arms are problematic in that they come loose over time, they are a maintenance headache, and despite being “universal”, they do not match every frame.

The Torque Arms install on the Vinson in much the same way as the Dolomite:

  1. The torque arms are slipped onto the motor axle.
  2. The freewheel side requires a 3mm spacer between the axle flat and the torque arms, to give a little clearance for the chain.
  3. The brake side also requires a 3mm spacer, mainly to give a little extra clearance for the wire bundle so it doesn’t chafe on the motor cover.

Since the Fat Bike motor axles have flats to fit a 170mm drop-out, the thickness of the 3mm spacers, and the pair of ¼” torque arms increase the total width of the assembly to about 187mm. The Vinson has a common 190mm drop-out width, which allows the torque arms to fit cleanly on the inside of the frame.

The brake side torque arm uses the ISO spacing of the disc brake caliper mount holes, with the torque arm fitting in between the frame and the caliper adapter. (We provide longer M6 bolts for the caliper mount in our torque arm kit).

Performance

With the added current of the high-power controller, the 5T motor puts out nearly as much total torque as the Dolomite’s 6T motor. The real benefit of the 5T motor is higher maximum speed. Whereas the Dolomite’s 6T motor topped out around 32 MPH, this bike can reach up to 40 MPH using the 120% mode of the Xie Chang controller. (The three-speed switch mounted on the handlebar allows us select between three power/speed levels:

  • 50% speed/power, which results in a maximum speed of about 20 MPH, which is the legal limit in most US states. (Legal Mode)
  • 100% speed/power, which allows the controller to operate at its peak efficiency, and results in a top speed of around 34 MPH (Cruise Mode)
  • 120% speed/power, when you want to get off the line really fast, and maintain the highest possible speeds of up to 40 MPH. ("Ridonculous" Mode)

One of the most critical aspects of the build was integrating the motor’s temperature sensor into the Cycle Analyst which monitors the temperature of the motor’s coils: When the coil temp reaches 100 degrees Celsius, the CA begins to limit the current output to the motor. If the motor continues to get hotter, the CA will shut off power completely when the stator temp reaches 120 degrees Celsius. Once the motor temperature falls below 100 degrees, the CA will allow power to the motor again. This prevents the catastrophic failure of the motor overheating and shorting out the phase wires or the hall sensors.

Extras that we really enjoy:

  • Hydraulic Disc Brakes help the bike to stop well, and the Shimano brake levers are much nicer looking that the typical mechanical ebrake levers.
  • Front & Rear Fenders/mud guards will keep the rider drier in muddy & wet riding conditions, and add a coolness factor to the bike.
  • Headlight that plugs directly into the CA. One of the reasons we love being a dealer for Grin Tech. They have great accessories for the Cycle Analyst.

Conclusion

The Vinson Project has been a great success, and we think, once you have had a chance to ride our demo model, you will be convinced. There is no better Electric Fat Bike on the market that can compete with our MXUS-Vinson.



Hydraulic EBrakes rock with awesome stopping power.



Rugged DH Headset and Stem, topped with the definitive CA3 for precision system control. Super-strong Stainless Steel Torque Arms safely transfer motor power to the frame.

From the Evergreen State to yours: This is one smart-looking powerfully fun ride for all sorts of road and trail adventures.