Mongoose Dolomite/Hitch Fat Bike conversions

The fat bike kits are our most popular kits we sell. Our YouTube video showing the Mongoose Dolomite with the 6T MXUS conversion is by far our most viewed video.

The Dolomite and the Hitch are close cousins from the Mongoose lineup. Both are 7-speed fat bikes and have very similar frame designs. The differences mainly lie in the fact that the Hitch is a bit lighter due to some frame design improvements and lighter rims. When we began researching potential fat bike donor frames - only the Dolomite was available, and we designed custom torque arms specifically for this frame. However within a couple months' time the Dolomite appeared to be discontinued with the Hitch looking to replace it. So we focused our engineering efforts on making new torque arms for the Hitch, which are similar in concept, but designed to fit a slightly different drop-out geometry of the Hitch. Recently the Dolomite has become available again at sites like and If you are purchasing a new fat bike for a conversion, we recommend the Hitch for its lighter weight. currently has the best pricing we have found on the Mongoose Hitch. While the rest of this article will focus on the build of the Dolomite, the Hitch would be identical in build process.

To get the process started we had our motor manufacturer - MXUS, make a customized "Fat Bike" version of their 3000W (45mm) direct drive hub motor. We are the only retailer selling this version of the MXUS motor in North America. All our fat bike kits include a "Fat Bike" MXUS motor, laced into our favorite 26" x 10mm double wall fat rims.

We then went to work designing a torque arm set that would allow this powerful motor to be mounted into an otherwise light-duty frame. The purpose of the torque arms is to prevent the motor's axle from spinning out of the drop-out slots. If you can imagine the torsional force needed to provide upwards of 50 foot-pounds of acceleration in a 29" diameter bicycle tire, you begin to understand that the forces at the axle are extreme and need to be countered by a very strong mounting bracket that we call a "Torque Arm". Here is what the torque arms look like by themselves ->

These torque arms are machined from 3/8" thick stainless steel with their geometry specific ONLY to the Dolomite. (We also sell a similar torque arm set for the Mongoose Hitch). The torque arms are what make the Dolomite and Hitch frames able to take the high power loads of our MXUS "Fat Bike" motors without damage to the frame. Below is a mock-up of the bare motor (without the rim & tire) with the torque arms installed. Notice that the torque arms mount on the inside of the bike's drop-outs.

When installing the Motor/wheel into the frame, pre-mount the torque arms onto the motor axle first, then slip the axle into the frame's drop-outs. Once the motor/wheel is mounted and the torque arms are secured to the frame - the rest of the build is pretty straight forward.

We recommend mounting the controller on either the downtube (under the triangle) or on the seat tube with the wires exiting the controller towards the ground so that water cannot easily infiltrate the controller housing. Wiring up the Controller to the motor requires connecting the phase wires (3 of them) and the hall sensor wire bundle with a single multi-wire connector.

The throttle, ebrake(s), and 3-speed switch are mounted to the handle bars with matching connectors mated at the controller which accepts battery voltages between 44.4V nominal (12S Lithium) and 82V Nominal (22S Lithium), with output up to 45 Amps of current - approaching 4000 Watts.

Depending on which motor winding you choose (5T for faster speed per volt, or 6T for more torque per amp) it's possible to attain top speeds up to 40 MPH - and as our YouTube video title suggests, an "INSANE" amount of torque!

We sell a 60V nominal (16S Lithium) battery that is designed to maximize the available triangle space of both the Dolomite and Hitch frames for a perfect fit.

As our YouTube video demonstrates, this set-up is very capable of providing outstanding performance in all kinds of terrain. It is also a great option for street riding, and always gets lots of looks and smiles from passersby.

Note: the Mongoose Dolomite and Hitch Frames include the expected low-end components that accompany a very low-cost bike. While the frames themselves are very suitable, we do recommend upgrading some of the standard bike components to provide even better performance and comfort. These might include:

  • Suspension front forks like the Rockshox "Bluto" fat bike fork are an excellent upgrade.

This fork would require a special headset that converts the standard 1 1/8" straight steerer tube to a tapered steerer tube, such as the Cane Creek "Tapered Conversion" headsets.

  • Other upgrades such as Avid BB7 mechanical disc brake sets, and our custom matching Front wheel would also be worthy upgrades.

Overall, the Mongoose Dolomite and Hitch bikes provide an excellent starting platform to build an "Electric Fat Bike", and we think the kits and upgrades we sell will give you the highest performance at the most reasonable price.

Check out our related story featuring this product conversion: Jan-2016 FatBike SnowDay.

FatBikes are cool!