Mongoose Dolomite Fat Bike 72V 3kW Options

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Joecool   1 W

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Mongoose Dolomite Fat Bike 72V 3kW Options

Post by Joecool » Aug 05 2018 3:32pm

I recently bought a Mongoose Fat Tire Dolomite bike for a rear hub conversion. Im having a problem finding a rear hub motor that has long enough axles. The rear dropouts on the Dolomite are 190mm. Ive heard from some on here that you can push the frame in a bit to make it fit a 170mm axle. Thats about a decrease on an inch. The frame is steel. Have any of you guys made a conversion like this? A couple of mm does not bother me but about 25mm is a little more extreme. Im assuming the nylon lock nuts and washers would hold the frame in but Im a little worried about stress fractures, etc. Id really like to hear from someone who has done this and what their experience is with it over the long term. Im looking for a 72v 3kW rear hub. Some suggestions that Ive gotten on here are a MXUS 5000W direct drive motor. A Magic Pie Vector, (195mm axle), and a 12t MAC geared hub motor (170mm axle). I also found this on amazon about a mongoose Malus which is similar size to the mongoose dolomite.

What is the wheel dropout width,is it 170mm? Will it fit a fat bike electric conversion kit?
Answer: Rear wheel drop out is 185mm. The bottom bracket is 110mm and I've converted this to an ebike using a BBSHD 120mm kit from luna cycle. It becomes a very sweet ebike on which I've done over 400 miles in a few weeks.
By Amazon Customer on November 5, 2016
This bike will work with 170mm axle 'Fat Bike' rear hub motors. I have 2 of these, one with a Magic Pie Vector, (195mm axle) and the other with a 12t MAC geared hub motor (170mm axle). The forks will pull in a little but that is ok. Rear break caliper only needed a 5mm washer on the rear most bolt to properly realign after being pulled in for the 170mm motor axle. The frame triangle also easily fits a 'Large Triangle Battery' (14s9p) from EM3EV. see less
By Donald M. on September 2, 2017

Bullfrog   10 W

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Re: Mongoose Dolomite Fat Bike 72V 3kW Options

Post by Bullfrog » Jul 07 2019 10:02am

JC,

IMO you are going to run into several issues if you use a motor designed for 170mm dropouts on a Mongoose Fat Bike...all of which have 190mm dropouts according to Pacific Cycles who makes all of them. Besides bending the rear triangle you will have problems getting the brake disc mounted correctly and you will have issues with the deraileur working properly if the gear cluster is not in the exact same location as the unmodified bike.

QS makes a bunch of hub motors that would work and would be my choice if I was going to go with a hub motor.

The Bafang BBSHD is a pretty simple installation and works great...and is what I did.

Drawback of the BBSHD is that the power is transmitted through the bikes drivetrain so you are going to put a lot of wear on your chain and sprockets. But on the positive side you can gear the bike to work well off road.

Drawbacks of a hub motor are that they are heavier and you can't change the gearing so riding off road may overheat them depending on how and where you ride. But on the positive side the hub motors are super simple and reliable and don't put any wear and tear on your chain/sprockets.

My recommendation is to go with a hub motor if you are going to ride on paved surfaces and to go with a BBSHD if you plan to ride on unpaved surfaces. If you plan to ride some of both...well you'll just have to decide which way to compromise.

I ran a MAC 12T motor in a 20" wheel with a 40A controller off road and it would still overheat. I weigh about 200 lbs and I the woods where I ride are nt that hilly but the top speeds are around 15 mph so the MAC just couldn't operate very efficiently at the lower speeds and produced a lot of waste heat. A hub motor is going to be less efficient than the MAC because it won't spin as fast since it is a direct drive and the MAC has the planetary gear reduction BUT the DD hub motor will get rid of heat better than the MAC...another BUT...the DD hub motor will be heavier than the MAC.

One sweet thing about using a BBSHD if you are riding off road is that you can run a single speed and get rid of the cassette/freewheel and derailleur. Just gear the bike for about 18-20 mph top speed depending on how tight your trails are and you never have to worry about shifting. I run a 28 Lekkie or a 30 tooth Mighty Mini front sprocket on the motor and a 22-28 gear on the rear depending on which rear tire I am using.

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SamRich   100 W

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Re: Mongoose Dolomite Fat Bike 72V 3kW Options

Post by SamRich » Jul 31 2019 3:41pm

I fit a QS205 and a 45H 150mm on my dolomite, but I have DR bass dropouts welded on the inside that are 10 mm thick. So I think 170 mm hub will be fine.
I had to fabricate a spacer for the Disc brakes.
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I also chopped the downtube, but would not recommend unless you know what you are getting into:

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Overall the frame is great. Super sturdy and plenty of clearance to place controller and fenders.
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