- Love 'em or hate 'em
press-fit bottom brackets are now really common.
And let's face it whilst they do get a bad rap
the vast majority of us
don't have a problems with them whatsoever.
What the principal criticisms levelled at them
is that they are hard to work on.
But actually,
fitting and replacing them is relatively simple,
you just need the right tools,
which is one of these,
which is a 'Bearing Press'.
And then,
something to knock your old bottom bracket out with,
one of these or one of these.
To know whether or not you have a press-fit bottom bracket
firstly ask yourself these questions;
"is your bike newer than about 2010
and was it really expensive?"
Because if it was older than 2010
the chances are it is highly unlikely you will have
a press-fit bottom bracket.
And if it was an entry-level or mid-range bike
then it too is unlikely that you have a press fit.
If however the answer to these questions was "yes",
and "yes"
and you still don't know if you got a press-fit,
you gonna have to take your cranks off.
And then what you're looking for is
for any form of indentations for a tool
to actually bite into,
so that very simply means you will be able thread
or unthread your threaded bottom bracket.
Where as a press-fit bottom bracket,
as you can see,
is completely smooth.
Once you've established that you've got
a press-fit bottom bracket
you are then confronted with many different standards.
But broadly speaking,
there are really just two types of bottom bracket.
Firstly, there are those that have a nylon or a metal cup,
with bearings already pressed inside
and the whole assembly is pushed inside
your bottom bracket shell.
And then you also have this type which is very simply
a cartridge bearing that is then pressed into cups
that are already built into the frame,
so that's like a BB30 style.
When it comes to working on them,
the difference between them is really only apparent
when you are removing the bottom bracket in the first place,
which we're gonna do now.
Let's start with the cup type first
so the BB86.
As I said, you need to push the whole cup out
and to do that, you need a tool like this
which is a Park Tool BBT-90.
The way it works is that you push the tapered end
through the bottom bracket
and then this sprung prongs at the end
compress as you push it through the bearing
and then expand outwards
just after you got it through that initial bearing
And then you can tap the other end
and the whole cup slides out.
Now, probably didn't escape your notice
that it actually takes quite a bit if force
to tap one of these cups out
and it's for that reason that these are not really designed
to be reusable.
So, you fit it and then
when it's worn out you tap it back out.
It's not a job that you do regularly,
pushing them in, taking them out.
If your bike is in a workstand like this
and you are hitting the bottom bracket out
do make sure that you brace the bike
really firmly by the downtube there
so that it's just not dangling from your seatpost.
With BB30, you need a tool like this
which is effectively a drift to tap your bearing out.
So you thread it through your bottom bracket
until it comes to rest behind the bearing
on the opposite side of the bike.
And then you square the whole tool up
using that plastic guide,
then you can simply tap it out.
Now, that guide is really important
because if you don't have it
then you can effectively push your bearing out an angle
which can damage your frame and certainly your bearing.
And so it's for this reason
that although you could potentially try
and bodge this whole procedure using a punch and a hammer,
it is really, really risky because as I say
you can damage your frame.
Which, you don't want to do.
Okay, so it's reassembly time.
First step is to set up our Bearing Press.
To do that, we need to select the right adapters,
and so the right adapters
is effectively the one that has the same diameter
as your crank axle.
And then the same external diameter
as your bottom bracket shell.
So, in this case is a Shimano crank
which is 24mm and is a 44mm bottom bracket shell.
Okay?
You'll see that it fits in there very snugly,
as if it's meant to.
Then we thread one side onto
our bearing press.
Then we need to thread that through our frame
before threading the other side
onto your bearing press.
And then cinching it all together
with the lock nut
like that.
Simple, right?
The press itself works in a really straightforward way;
you simply turn
that lever there and you'll see
that it's pushing the cups together.
Now, the reason you use a Bearing Press
is that the adapters hold everything straight,
as does the fact that you're pushing
both cups in at the same time.
Again, the fact that it's going straight
is extremely important.
One final question that needs answering
before we do press our bottom bracket back in
is to whether or not you put grease on the cups.
General rule of thumb is
if you are using a metal frame then you want to put grease
or locking compound on the cups
and that prevents it creaking.
And that includes in fact
an aluminium sleeve inside a carbon frame.
However, if you are pushing them into a carbon frame,
then the general consensus is you push them in dry
because grease can potentially soften
the inside of the carbon
which is not what you want.
So, this instant
we're going carbon on carbon
so we're going in dry.
With BB30, however
always grease up the bearings.
Ah.
Done.
Again, just like with removal
you could potentially try and budge this procedure.
Either with a home-made press
and some blocks of wood as drift.
Or indeed, dare I say it,
a hammer and a block of wood.
But the fact is,
you are in all likely talking about
a really expensive frame here
and such a poor cost-cutting exercise
simply, it doesn't add up when you weigh against
how much it would cost to either repair or even replace
your frame.
And that is what we're talking about here
if it goes wrong,
it really could be quite bad news.
So, this is one of those workshop jobs
where you need to invest in the right tool
but you're only investing in it once.
And then you can do the procedure as much as you want,
for free.
Well, hopefully
despite that last severe word of warning
I haven't actually put you off doing this procedure,
it is reasonably straightforward
as long as you have the right tools.
Now, make sure you subscribe to GCN.
If you do like doing workshop jobs yourself
we have a Maintenance Monday video for you
every single week.
Now, if you need a bit more information
about bottom bracket standards,
and who doesn't?
We have a video on that exact subject.
So hopefully we'll explain it for you
and get to it just down there.
Or, to actually do a more rudimentary job
but one that is essential for this procedure,
taking your cranks off,
click just down there for step-by-step guide.