Mongoose dolomite fatbike? 7spd, disk brakes, INEXPENSIVE

[wesnewell]

This is the MXUS 3000 V1, with 45 mm stator, so the motor is a little wider than most I would assume. IIRC it requires 142mm dropouts minimum with a 220mm axle. With the rear wheel off, the rear dropouts on the Dolomite were 205mm, but can be squeezed in considerably. When I mounted the motor I pulled them together enough to hve a couple of threads beyond the end of the axle nut and screwed the jamnuts out to there before tightening them. Not a problem except for the disc brake caliper, which I moved in to match up to the disc using longer mount bolts and washers. A single solid block would have been better for this, but I don't think the washers on each bolt will cause a problem.

 

[diggler]

No way no TA eh?...
You've never ran this big of a motor either.
Very interested in hearing how everything works out for you in the long run.
You used the stock rim right?
I suppose the washers and bolt don't matter on the brake cause of regen right?
Did you have a build thread for your fat bike?
I hear yah about the cold. We had sleet, snow, slush then rain here in mn today. I'm not doing any riding till I get my custom fenders in for the fat bike.
http://stores.bigomfg.com/specialized-fatboy/
Here is a link to full coverage fenders for fat bikes. Took me a long time to find this guy. Only other option I saw for full coverage fenders was mkfenders and there beautiful wood fenders but cost like $500. The guy worked with me for two weeks getting all the measurements. I wanted more coverage on the front tire so he's sending me two rear one's then I can cut to where I want and use the cut off peace as a rear mud flap.

About the freewheel. I'll have to figure things out when I get there but I could epoxy Doc's TA to the inside then mount derailleur to the inside or outside of the TA.

O and broke my bb is 100mm I think that's pretty standard on fat bikes.

 

[wesnewell]

I was going to use the stock rim but probably would have had to drill it for 12g spokes so I ordered a new rim Weinmann DHL101. It got belayed due to weather and took a couple of weeks to get here. I don't use TA's. Bike has steel dropouts. With torque washers and jam nuts on both sides, there's no need for TA's. And yes, I do use regen braking. Probably won't ever need the rear brakes, but they seem to work ok with the washers. If I had a drill press, I might make a solid block spacer.

 

[diggler]

Cool you always seem to simplify things quite a bit.
I got TA's from the Docbass coming, MXUS 3000 and 18 fet Infineon (programed for me) in the works from teslanv.
I'm prob most exited about fenders for the moment though. I got douched hard today going 16 miles in cold dec rain. :lol:
just need to figure out how I'm going to mount batteries. Is there any threads on here about DIY pannier boxes?
Cant wait to hear back about your bikes performance. I want to see how that rim holds up too. Are you pretty happy with it so far?

 

[diggler]

Wesnewell.

Couldn't you put a dick brake rotor spacer on the hub instead of moving the caliper?

 

[wesnewell]

If i had rotor spacers. I didn't and washers and bolts were local and cheap, where rotor spacers would have cost $40 for 10 2mm spacers, and then I'd need 6 longer bolts.

 

[diggler]

okay. Just wondering if it were possible.
Thanks

 

[diggler]

Dan J peddleton
How is your build goin?
Sorry didn't mean to take over your thread.

 

[danjpendleton]

Diggler its okay. i ended up going with a 39t chainring and 8.3 mm triple chainring spacers, 17mm bolts(i think). it pushed my chainring far enough in to get all 7 speeds operable. I didnt like the black chainring nuts so im waiting on some silver ones

 

[diggler]

Nice you got everything lined up!
I'm struggling with that right now. http://endless-sphere.com/forums/viewtopic.php?f=6&t=65638

 

[2old]

For anyone planning a similar build, the recent incarnation of Dolomites has a 32 hole rear rim. My motor is 36 hole and new rim is necessary.

 

[ambroseliao]

As of today, the Mongoose Dolomite fatbike is selling for $192 over at Target.com! That's a $48 price drop! Ships for free but there's a $30 oversized handling fee added. $222 total shipped to CONUS.

http://www.target.com/p/mongoose-men-s-dolomite-fat-tire-mountain-bike-navy-red-26/-/A-15666264

 

[ebikedelight]

For anyone planning a similar build, the recent incarnation of Dolomites has a 32 hole rear rim. My motor is 36 hole and new rim is necessary.

well that sucks.

I guess Ill go with a mid drive kit now , which may be better since it will give more torque power with such a heavy bike and 4" tires.

 

[2old]

Keep in mind that the Dolomite, like many fat bikes, has a 100mm bottom bracket for chain line issues and requires either a $500 kit or other modifications to install a mid drive.

 

[duffmanaudio]

It's 191 at walmart. I think Site to store is free.

 

[2old]

Looks like free shipping (not just to store) at Walmart. Glad my garage is full and the lone Dolomite is being converted for a friend at his shop.

 

[lbeck37]

I've just completed installing a Bafang BBS02 36V 500W mid-motor in a Dolomite without changing the motor (i.e not purchasing the $500 kit) and doing nothing to the bike except narrowing the bottom bracket to the chain-stays and making an offset left crank by bolting two cranks together.
The whole installation was much simpler than I expected. I purchased the bike just to see if it was even close to possible to install a BBS02 kit from another bike I have. I really expected to discover it was not possible to do without cutting and welding chain-stays or that the final setup would be a mess with a poor chainring alignment or something else and that I would return the bike.
When I got the bike I stripped the bottom bracket and did some trial fitting and measuring and discovered that if the right side of the bottom bracket was trimmed all the way to the chainstay (and the chainstay was dented in about 2 mm) and a non-offset chainring (I had one from SickBikeParts) was used then the front chainring would line up right in the middle of the rear cassette!
I was going to use the Bafang (48T?) sprocket but it made the chain too short and I didn't have any chain. I think you could use the Bafang sprocket (it has to be flipped to clear the chainstay) but it will not line up well with the rear cassette. The sprocket I had from SickBikeParts happened to be the same 32T as the Dolomite, it had a large enough center hole and after I slotted the (5) attachment holes it was a perfect fit!. The sprockets are cheap at SickBikeParts.
Of course the bottom bracket was still too wide but when I trimmed the left side down to almost the chainstay I was able to put the motor brace, which I had ground off about 2 mm where the nut seats, and the nut which cinched down very well with almost full thread engagement. I performed the first cuts on the bottom bracket with a saws-all and completed the trimming with an angle-head grinder.
I purchased two left cranks from a local bike shop and discovered that if (after cutting one end off each crank) I sandwiched one crank to the other I got the 1" offset I needed to clear the left chainstay. I bolted the cranks together with two 5/16" grade 8 bolts. I don't really notice the Franken-crank when riding and it doesn't really stand out when you look at the bike. The Bafang right-side crank doesn't have much offset and was just barely hitting the chainstay so I put a left-side crank (with enough offset) on the right side. I'm not sure if I will sick with this (the backwards pedal threads is a problem with matching pedals and maybe unscrewing) but it works for now.
Everything works well, the motor works really well with the bike and makes up for it's weight and drag from the tires. I took it out on the beach and it worked great, even in soft sand. It behaves like a little dirt-bike in the sand, it has to get a little speed to get up on the sand and then it wallows sometimes but it's a lot of fun. It's easy to shift gears quietly by touching one of the brakes to cut the motor and releasing it when the shift is done. The battery is a 14.5Ahr down-tube-mounted one from Lectric Cycles which fits well and is easy to mount and dis-mount.
If there is interest I can post more info.
BTW- The front wheel shutters front and back (the brake chatters) when I apply the brake hard. I've cleaned the disc and checked the steering head which helped but did not fix it totally. Anyone else have this problem?

 

[ebikedelight]

Lbeck37...I am extremely interested in your project , but I would need you to post photos and clear instructions for each part of the process because this sounds quite advanced . Its good to know this can be done using a stock mid drive and some mods.

 

[lbeck37]

I took some pictures and reduced their sizes below the 512Kbyte limit. Here's the first 3 of 10.
--Larry

 

[ebikedelight]

Thats impressive , and it saves alot of money compared to buying the newer modified BBS02 that is made for fat bikes.

When cutting down the bottom bracket, did you have to rethread both sides of the B.B ? If so, what size tap was used ?

 

[lbeck37]

Here's some more pics of my Mongoose Dolomite w/Bafang BBS02 36V 500W motor and 14.5Ahr (522 Whr) battery.
--Larry

 

[lbeck37]

Here are pics showing how close I trimmed the bottom bracket, pretty much right up to the chain stay. The Mongoose has a 100 mm wide BB but the chainstays are bent in and welded like they would to a much narrower BB. This allowed me to narrow the BB enough to get the nut on the Bafang without messing with the chainstays. Other Fat Tire bikes are not like this, their chainstays are welded out near the end of the BB, where they should be for strength. Maybe Mongoose originally thought they would use a 100 mm wide BB?
--Larry


View attachment 1

 

[lbeck37]

I didn't have to thread the bottom bracket. The Bafang doesn't use the threads in the BB. You take all the stuff out of the bottom bracket leaving just the shell, and then you slide the Bafang's "snout" through the shell, slide the motor support bracket (with ridges that jam into the BB and help prevent the motor from moving) over the snout and then thread the nut on and tighten it tight That's all it takes to install a Bafang BBS02 into a bike with a 68 mm wide BB. Surprisingly Mongoose bent the chainstays in far enough on the Dolomite so that I could be trim enough on both sides to get the BB narrow enough to let me get the nut on the Bafang snout.
--Larry

 

[cjh]

I think tahustvedt used a 170mm SR Suntour XCT Left Crank Arm which gave another 19mm offset. If you combined that with a little cold bending like e-waka did you would have your 25mm/1" offset without the cut and bolted look.

http://endless-sphere.com/forums/viewtopic.php?f=28&t=63250

http://endless-sphere.com/forums/viewtopic.php?f=28&t=62518

http://endless-sphere.com/forums/viewtopic.php?f=28&t=65663

 

[ebikedelight]

I didn't have to thread the bottom bracket. The Bafang doesn't use the threads in the BB. You take all the stuff out of the bottom bracket leaving just the shell, and then you slide the Bafang's "snout" through the shell, slide the motor support bracket (with ridges that jam into the BB and help prevent the motor from moving) over the snout and then thread the nut on and tighten it tight That's all it takes to install a Bafang BBS02 into a bike with a 68 mm wide BB. Surprisingly Mongoose bent the chainstays in far enough on the Dolomite so that I could be trim enough on both sides to get the BB narrow enough to let me get the nut on the Bafang snout.
--Larry

When you get a chance, Id love to get some stats from you about this mod ..like

1. how much do you weight and how much does the entire bike weigh now

2 . top speed on flat road and top speeds in each specific gear

3. climbing abilitiy

Thanks for all your help. Im thinking I am gonna do this mod soon.

If I do this mod, I will probably offset the left crank/ pedal by getting 2 crank arms and cutting the circular part of the crank arm that attaches to the crank , completely off , then line it perfectly up to the inside to the other complete crank arm so both holes line up perfectly and it can be fastened to the crank . The hole on the outside crank may need to be drill out a bit wider , but leave the inside crank hole alone so it will fit tightly once the nut is put on.

This should give you the offset needed, and be barely noticeable .