How to Service Mongoose Fat Bike Bottom Bracket

How to Service Mongoose Fat Bike Bottom Bracket


the first order of business in this
miniseries is going to be removal of the bottom bracket and this is important
because when these come from the factory they’re usually way too tight and they
usually don’t have very much grease inside of them the problem with that is
between the tightness and the lack of grease they’re gonna wear out fast and
leave you with tons of issues when it comes to peddling so what I suggest is
removal of the bottom bracket and then really load these things up with grease
and then you can go back through and reinstall them knowing that it’s gonna
be lubricated and set properly okay so the first thing that you’re gonna need
to do before you can actually remove the bottom bracket is you’re gonna need to
take your crank arms off now when you receive the bike it’s gonna have to
crank arms it’s gonna have the drive side crank arm that has the sprocket as
part of the crank arm and then it’s gonna have the other side which is just
an arm now one of the things you need to know is that these have a square tapered
hole and this actually fits onto the spindle that runs through the bottom
bracket and connects the two crank arms together when you receive it it’ll
actually have a 15 millimeter bolt holding it on now mine’s changed a
little bit because I’ve put new crank arms on it but what you’re gonna need is
you’re gonna need a socket wrench with a 15 millimeter socket you’re going to
need to take those bolts out now when you remove the bolts the crank arms will
not come off and in fact they are gonna be on there very tight really the only
good way to remove them is to use a crank puller now this is a maybe a
slightly higher end crank puller but you can get them as just a small piece and
what happens is this outer collar threads into a cut thread inside the
crank arm and then basically you just spin it and it’s gonna push the crank
arm off and I’ll demonstrate that for you on the bike the very first thing
you’re going to need to do is you’re going to need to remove the chain from
this bracket up here and you can simply just kind of pull on it and bring it in
towards the frame and then your crank arm should be loose now once you’ve got
the chain off it’s a matter of actually taking those bolts out so on yours you
would use that 15 millimeter and take these loose now on mine I’ve actually
got an Allen so it’s a 10 millimeter allen and basically it just goes
there loosen it and out comes the bolt now what you’ll notice though is that
this crank arm is still on there super tight it’s not coming off without that
special tool so what we’re gonna do is we’re gonna use our crank puller and
what you want to do is take that outer collar you just want to thread it down
until it’s flush with the end of the other piece and then you’re gonna take
it and you’re gonna put it in there and you’re simply going to thread it into
the threads that are cut into the crank arm now once it bottoms out you’re
actually going to want to go a little bit tighter what I found is majority of
these use a 7/8 wrench however if you don’t have that an adjustable wrench
will work just fine do is you’ll run this in until it’s completely tight and
then all you need to do is hold the opposing crank arm and run this one tool
down and what this is going to do is it’s going to pull the crank arm off of
that spindle so just bottomed out and now you can kind of work with the other
arm and it’ll loosen up pretty easily and then voila pops up and we’ll do the
same thing for the other side the next step in the process is to
actually remove your bottom bracket cups now that’s this piece here and you’ve
got a matching piece on the other side but it’s got a bunch of slots cutting
now to pull this side all you’re going to need is your adjustable wrench and
basically you’re just gonna take it and now just so you know on the drive side
it’s gonna be reverse thread so you’re going to want to go forward instead of
backwards when you when you crank this thing off can’t lose pretty easily once
this comes off your spindle will actually be free on the inside and
you’ll also have a bearing in there and it should be very heavily greased if
it’s not it needs to be so you can pull that bearing out set it aside and then
you can actually pull your spindle through now mine’s got this little
sleeve on it and basically it just keeps from moisture from dropping down the
seat tube into the bottom bracket from causing issues however years may not
have that especially if yours is just a new Mongoose we’ve got the bike spun
around and now you can see the other side of the bottom bracket Cup now this
actually has this adjustable collar on it and then it’s got a threaded Center
section they do actually make a special tool it’s a spanner that fits into these
little notches cut into this for removal now I don’t have one because this is
actually a really old style bottom bracket so it’s not in my tool set
because my tool sets a little newer so what I’ve always just done is used a
screwdriver and a rubber mallet now I’m sure I’ll get some flack for this but
it’s the simplest and easiest way and I’ve been doing this for a long time and
never really had any issues and basically you just tap it until that
comes loose and then you pull that threaded piece off and then the cup
itself will thread right out of the bottom bracket on the frame once that’s removed you’ll also see
there is a set of bearings in there that should be very heavily greased if they
are not they need to be and this is the most important thing when you buy a new
Mongoose is to make sure these things are loaded up with grease because they
come sometimes almost dry ok there you’ve got it that was the removal of
the bottom bracket super easy only takes about 5-10 minutes if you’ve never done
it maybe 20 now when you get this thing apart this is kind of what you’re gonna
see so you’ll have that first piece with the two flats that we removed with the
adjustable wrench this is your bearing that sits inside of here you’ve got your
spindle your next bearing you’ve got the other side your cup and then you’ve got
the slotted collar that threads down on the cup now before you go back together
you’re gonna want to grease the heck out of this thing and I greased every single
surface I load these cups up with grease i grease the entire spindle i grease
everything and I use a bicycle specific grease made by dual Co and it works
actually very well to lubricate everything it does a great job when you
go back together make sure that you put this piece on first this is the piece
that you need to install with the adjustable wrench and tighten it down
until it’s snug then you can put your bearing on your spindle kind of
demonstrate put your bearing onto your spindle make sure that the cage is
facing away from the race on the spindle then you’ll put it through your bottom
bracket and it’ll sit inside here then you can put your other bearing in onto
the spindle same thing make sure that the cage is facing away from the race
then what you’ll do is you’ll install this you thread this into the bottom
bracket until it touches and then you’re gonna take this collar and you’re gonna
thread it on there and you’re gonna run that down until it hits the bottom
bracket on the actual frame itself and then what I do is I just kind of spin it
a couple times to make sure it’s not too tight and I make my adjustments as
necessary so sometimes you might have to take this off tighten this in even a
little bit further and then tighten this down even more
all right quick and easy so that was the first episode in this Mongoose
miniseries that I’ll be doing now make sure you go ahead and hit that subscribe
button because I’m going to come into you with a lot more on this bike how to
grease your hubs how to disassemble the headset and remove it and I’m even going
to make a makeshift paint booth for this thing and I’ll show you guys how to do
it in your garage so subscribe give it a thumbs up and if you have any comments
or suggestions throw them down below thanks again you guys

Only registered users can comment.

  1. I'm trying to find a project Moongose Fat Bike to overhaul it for fun, love the videos! What bottom bracket would you recommend to get to replace the factory one?, Thanks!

  2. What is the new crankset/bottom bracket..I am looking to replace the stock bottom bracket but don't know what size I would need. Thanks

  3. This ROCKS! I've been wanting to upgrade my BB, but wasn't sure how to remove the little slotted collar. Just ordered a cheap crank puller and the BB and will be checking back in once they arrive. Thanks for sharing, and keep up the vids!

  4. I just tried that and it tore up the crank threads on my mongoose malus. Good news is those arms aren't going anywhere so I just skipped the grease and put the bolts back on. The bike is new and at least I have a year on the warranty. But kinda wished I was able to grease the bb like you said. Thanks for vid, not many have put up fat bike vids like this.

  5. Another great video. I will be getting a used Hitch so hopefully the BB isn't already ruined. Do you take suggestions on budget bikes to look at?

  6. Can you provide the measurements for the spindle? ALso I live in AK was told I should use a crank with external bearings made for the cold? what are your thoughts? i told like the fact that you have play around with tightening the bottom bracket you used. Is there an alternative bottom bracket that would eliminate this need, even if it's more expensive? Great job by the way!!

  7. Useful tks. Does anyone here know parts needed to put a smaller sprocket on the mongoose dolomite because it's unrideable up a hill. I bought a 28T/74mm sprocket thinking i could switch sprockets but looks like I need a new crank set. I'm guessing this is a common issue. The factory gearing seems impractical for anything other than flat.

  8. I am working on a Mongoose that was purchased in Sept. 2018. I noticed that the spindle is length is different on each side, between the race and the end of the spindle. When you disassembled the bottom bracket, the longer end of the spindle was on the drive side w/ the non-adjustable cup, and the shorter side of the spindle was on the non-drive side with the slotted adjustable cup. I am going with the orientation that you showed on disassembly (Drive-side/long end – Non-Drive/short end). Thanks for a great video. It helped me understand the proper removal technique of the cups.

  9. Thanks for making this vid. Just bought a brutus and havnt messed with bikes since early 90's. And wasnt sure how to check to see if my bearings are greased properly. This helped me understand the bb. When i do it I'll be using your advice. Thanks again.

  10. I was going to get finnish line grease for my bearings, should I spray out the original grease that comes with bike? Thanks so much

  11. That axle is from the 90s..throw it out and replace it with a REAL Bottom Bracket. Say a Shimano UN55. A UN26 will do but the UN55 is strong as hell. I cringed when I saw your axle…its not even a bottom bracket.

  12. Good deal. Thanks for the tip on the YST bearing set.
    I won't need it to be super smooth because I won't be pedaling much with the 3Kw motor I'll be adding to the bike, but I like the idea of keeping crud out of the bearings.

  13. Do you know the measurement of the bottom bracket itself? I want to upgrade my bottom bracket of my Schwinn Biggity (Which I bought from Canadian Tire) fat bike which is essentialy a Mongoose Malus in the US, thanks.

  14. this mini series has helped me so much with my fat bike mongoose. i feel like I'm ready for these upgraded components.

  15. Hello Budget friendly biking, I am based in Morocco and I have a fat bike, I am looking for Spindledo you guys sell the parts? Thank you

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