How To Service A MTB Dropper Post | Mountain Bike Maintenance


– Dropper seat posts are everywhere, including in the firing
line of muck and grime. A good thing to do to keep
it running better for longer, is a quick tear down rebuild. I’m going to show you
how to do that today. (crashing sound) In this video we’re going to be servicing a cartridged based system, such as this Crankbrothers Highline. A Rockshox Reverb or a Fox Transfer uses a slightly different system and cannot serviced in this way. As you can see, I’ve already
removed the seat post from the bike. If you grab some masking tape, you can just put a bit
on your saddle rail. This will make getting it in
the same position again easier and also, you can apply
some to the gear cable, which actuates at the
bottom of the seat post. This means it won’t
drop back into the frame and potentially make your job a bit harder when you’re reinstalling the post. You can also make a note of
how far the saddle is sat in the frame, using the
indication marks on the seat post. For this service, I will be
using a 10mm Allen key, a 5mm Allen key
and a 2.5mm Allen key. As well as that, I’m using quite a small flathead screwdriver
and a hammer that’s got, we call a toffee hammer, something that’s got a non-metal option, which is always very useful. Also things to use are a
nice slick suspension grease, some isopropyl cleaner
and some blue towel. The first thing I’m going to do is actually disconnect the cartridge from the top of the post. You do this by removing
the seat clamp assembly with your 5mm Allen key. So I’ve removed the seat clamp
there, the whole assembly and I’m going to move it to one
side, leave it somewhere safe and come back for it later. Now, at the top of this seat post is this very small 2.5mm bolt. This isn’t something you
actually need to remove because all the serviceable
parts can be accessed via the bottom, but I
just thought I’d show you how easy it is to do. This is a really, really,
really small bolt. So, yeah again, put it somewhere safe. If you leave it there, I
promise, it will disappear and it will never come back,
so I’m going to put it over with the seat clamp assembly,
somewhere nice and safe. So the cartridge is
disconnected at the top half. Now what we going to do,
is we’re going to take out this whole assembly out the bottom. You can use a vice to clamp on there, or there is a 10mm interface,
which is nice and easy. If this is a bit tight,
maybe get some towel on it just to get a bit of purchase. There we go. Relatively easy to do. Then it should just come out by hand. So this part is a moving
part, so sometimes these here, on some styles they can, kind of, corrode and things like that, the
actuator at the bottom. These ones tend to be
quite well finished alloy, so it should be okay. A bit of friction at the
lever can actually lead to corrosion or stiction in this part here, so if that is the case it’s always worth maybe a drop of lube, bit of elbow grease and cleaning that up. And now, because the cartridge
is disconnected at the top, we can actually just
pull the whole thing out and lay it down. Like I said, this service is doable without undoing that bolt, it just means everything
protrudes out the bottom, but it’s relatively simple to do and the next thing I’m going to be doing is taking off this collar. This is where your main seal sits, that keeps out the elements. This is really important
to keep running smooth. Often if there’s a lot of
stiction in the system, if it’s really slow to a turn,
this is your main culprit. You can see that this whole tube here is just going to slide off
and it’s really important, we’re going to give that a clean in a bit. Just below the main seal is this bush, which can also give you
problems on some posts. What happens is grit gets in there and what is quite a close tolerance fit, if there is any muck that gets in there, you get the really horrible grinding, when you get the white
marks dripping down the back of your post and it makes it
really, really slow to a turn. So this one luckily, it has
a little mark just there and we can just pull that straight off. As you can see on this seat post, we have what we call the keys here. Now what these do is
they stop that, kind of, side to side play. If your seat post has
developed a lot of play, the chances are that these are worn, but they’re actually made to wear and what I mean by that is
these are replaceable parts that stop the expensive
seat post being a write off when it develops play. So it’s a really simple job to do. They do have a little slot there. So using a small flathead
screw driver we can just get underneath in there and prize them up. Like I said, this is a replaceable part and it’s actually
designed to be consumable to save your seat post and
make it last for longer. And the last part of the
assembly that I just need to use this screwdriver to remove is this small little snap ring that sits just at the
bottom of the shaft there. Yeah, we’re just going to take
that, put that to one side and what that means is that this seal can just come straight off. You do have to remove the
keys to access this seal and having it off certainly
makes it a lot easier to lube. So now the seat post is completely apart, this is the time for a good inspection and a thoroughly good clean. As always on suspension parts, use a beam of light to check along and this will really,
really aid your inspection to see any small details
that might go missed in normal light. Now we’re about to rebuild our seat posts. I do strongly advise being
careful which grease you use. You want to be using a suspension grease. If you’re using a normal assembly grease, it is just too thick, it’s too viscous and will create friction and
your seat post will be so slow and that will be the reason,
so a nice, thin grease. Now, we want to be using
a generous amount of lube for that interface, so before
we even assemble the post, we’re going to put a
healthy serving into here and I also want you to
think about the channels that these keys work in. If you imagine the way a seat post works, especially on some bikes
that have slightly slacker seat tube angles and
potentially quite a heavy rider, all that force from these two small keys is being put down, the
force is coming this way from almost behind and down the bike and it’s being forced that way, so these relatively small pieces have to take quite a substantial load. It’s also worth noting that if your bike does suffer from that and your bike does have
a slack seat tube angle, maybe try and move your weight
in line with the seat post. Not vertical, but in line. This will actually keep your
seat post smoother for longer and reduce the load that it has to take. When we’re putting on this seal here, if you try and force it
just through this way, it won’t like it at
all, so we start there, I think almost at 45
at the post, rotate it and it will just pop on. We’re going to slide
that up and out the way, before reinstalling this assembly
of keys and bushings here. So I’ve got my keys here and I’m just going to snap
it in by hand and then, with the soft part of a hammer. (hammer banging) I’m just going to run along
it, make sure it’s well seated and then I’m going to visually inspect it to make sure that top part
is parallel with the post. If it’s at an angle, well then it’s not installed correctly. I’m going to pop that snap ring back on and then we’re going to just
slide the seat post all together. (chill music) This seal here only really
needs to be done up. Hang tight, that sort of territory, you don’t need to be swinging off it. So there we go, that’s
the seal all serviced. Basically all we’ve got to do now is reinstall the cartridge. So I’m going to drop that in there, reach for that very small 2.5mm bolt and just nip that up with
these small alloy bolts. Don’t put a lot of talk that way. When you come to actually
make sure it’s nice and tight, do it with a nice,
decent quality Allen key. If you do it with a ball headed
one, it will just, kind of, cause the bolt damage, which is obviously the last thing we want. So with this seal here, with this O ring, it’s really important
that it’s not pinching, it’s not coming at an angle and it’s not interrupting anything those threads are trying to do. So what I would do is actually
just put it on the table and slide the whole thing down like so and then just thread it in. Now, once that’s kind up, hang tight. Yet again, we’re just
going to nip this up. You don’t need to be swinging off it guys. Now we just need to reinstall the seat clamp assembly on top. The orientation is really important here for how we install this seat clamp. Bit of a rookie error is
to put one of those parts back to front and your seat
position will never be right, so just take a bit of extra care. Also, although these ones seem to be okay, some seat posts do suffer
from these bolts, kind of, working loose over time,
so it’s worth cleaning them with an isopropyl alcohol,
removing all the grease and putting a bit of retaining compound. Now, the reason it’s really
important to clean them is that retaining compound
won’t be able to work properly if it’s contaminated with grease, so just be careful for that. These ones are okay, but just, you know, if that’s something you do suffer from, just put a little dab on there. (chill music) And there we have it. That’s how to service a
cartridge based seat post, such as this Crankbrothers Highline here. That’s all you’ve got to
do, refit it to the bike and you are good to go. Now, if you want to
stick with the channel, you can see the maintenance video I did where I did a realtime
service on a rear shock. That’s worth checking out, so
click down here for that one and if you want to see seven ways you’re destroying your mountain bike, click down here to go for
that one with the Dodster. Thank you very much, don’t
forget to like and subscribe and hit that notification bell. We’ll see you next time.