Workshop: Service the seals on your Fox 32 fork
By Ashley Smith, Mojo | Wednesday, February 17, 2010 9.45am
For suspension forks to work effectively they need to be in as friction-free an environment as possible. That seems easy until you look at the grubby places we mountain bikers ride our bikes.
Given the relatively low weights and forces at work when riding a mountain bike off-road (in comparison with, say, aircraft undercarriage struts on landing) the fork has to be clean and well lubed if it is to be able to move rapidly enough to isolate you from the shocks.
To keep the outside out and the insides nice and oily, forks are ﬁtted with seals. Telescopic forks usually have upper leg ‘stanchions’ and lower leg ‘sliders’, and the two pieces should move over each other with minimal effort. Here Ashley Smith from UK distributors Mojo shows you how to service Fox Racing Shox's 32 series forks.
Step-by-step guide to servicing the seals on a Fox 32
Time: 45 minutes
Tools: Mallet; pliers; 10mm socket and socket driver; socket T handle; Float Fluid x2; crush washers x2; 2mm and 5mm Allen keys
1 Read the manual
Tucked inside your fork box you’ll ﬁnd a Fox Racing Shox owner’s manual CD, like the one pictured. This contains all the technical notes on working with your fork: service intervals, best care advice and suggested air pressure guides. Of course, most people never refer to the instructions, but it’s handy to know where they are next time you get yourself into a pickle.
2 Ride your bike
With any maintenance task on your bike you need to know what you’re dealing with before you rip into the job. Engineers like a report sheet, so make one. Then go for a ride and concentrate on what’s happening with your fork. We might only be dealing with the seals today but spotting anything unusual could save you a lot of cash in the long run. Keep an eye on odd feelings or noises and, if they persist, you may need more extensive work done.
3 Make some notes
Your fork has been set up a certain way – probably by trial and error and, most likely, by you in a hurry. Chances are that you yourself don’t know what settings you’re running on your fork. Write the current settings down and keep them safe; you may be happy with them and want to dial them in straight away after your service, or you may want to improve the performance by altering your settings.
4 Chocks away
Your fork seal service can be done at home with the bike resting upside down on the ground. We recommend giving your fork a good wash before you begin the strip-down, as it will reduce the amount of work you’ll need to do later. Then remove the front brake from the sliders. Remember to put the bolts and spacers in a safe place. Give the callipers a clean while you’re there – they’re usually manky.
5 Rebound off
With the front wheel removed the ﬁrst job is to remove the red rebound adjuster from the bottom of the right leg; with the bike upside down, it’ll be staring you in the face. Use a 2mm Allen key to undo the small threaded grub screw and slide it off. Place it in the same safe place you put the front brake hardware.
6 Base nut 1
Using a 10mm socket and driver you can undo the small black base nut from the bottom of the same leg: it’s under the red rebound adjuster you’ve just removed. You’ll need a socket to do this job properly as there isn’t enough space behind the dropout of 9mm forks (and even less on the QR15 models) to get a spanner in there without damaging the paint on the fork. They’re sold individually, so you can buy only the ones you need.
7 Base nut 2
You can now move onto the base nut located on the bottom of the left-hand leg (the one the brake normally ﬁts to). This one can be accessed using the same 10mm socket and driver you used on the left leg. With the second base nut removed you’ll be left with two short threaded sections of damper rod protruding from the bottom of the sliders.
8 Crush washer
As you unscrew the base nuts you’ll see a small thin black washer with a slightly conical proﬁle. This is a crush washer that helps to seal the holes in the bottom of each leg. They may be in the recess at the bottom of the base nuts, or more likely on the threaded section of the damper rod. Gently ease them up the threads so as not to damage them and store them safely. Damaged crush washers must be replaced (£7.50 for 10).
9 Damper rods
With the crush washers safely removed you can now thread the base nuts back onto the damper rods. When both are in position use the 10mm socket and driver and a mallet to give them both a sharp downward tap. This releases the dampers. The reason for fitting the base nuts for this step is that it stops the damper rods from disappearing inside the sliders. Now remove both of the base nuts.
10 Slider removal
The time has come for the clever bit: slider removal. Give the dropouts a gentle waggle to try to free them a bit. Then, holding the stanchion and the sliders, try to pull the sliders upwards (effectively down the stanchions) and off the bike. There can be a degree of hydraulic lock holding them in place – cycle the sliders up and down a few times to try to break the lock, they’ll eventually ride freely up the stanchions for removal.
11 Smiles apart
By this point you should have the stanchions fully exposed with their damper rods pointing upwards and looking wet with clean oil. The stanchions contain the fork’s oil so whatever you do, don’t knock the bike over at this point or you’ll have fork oil everywhere; if you’re a kitchen mechanic, you’ll be for the chop.
12 Lip seal wipe
This is the point where you’re going to have to pretend to be a surgeon operating on a patient, as care is needed when cleaning the feathered edge of the wiper seal. We use a little fork oil (applied with a lint-free cloth) as it’s what the seals are designed to be in contact with.
13 Foam ring out
Use something long and thin but not sharp (we used the ball end of a long 2mm Allen key) to gently probe inside the open end of the rubber seal. You’re trying to hook out the thin foam lubrication ring from under the bottom of the lip seal. When you have the foam ring hooked be careful not to pull it too hard, as it’s very easy to break or tear – if that happens it will need replacing with the ofﬁcial Fox part.
14 Cleaning the ring
The colour of the ring will give you a fair indication of the state of the inside of your fork. If it’s an even yellowy colour, the oil inside the fork is in pretty good shape. If it’s dark or sticky – or worst of all has particulate stuck in it – then the oil will need replacing (refer to the Fox manual for exact oil levels). Clean the foam ring with degreaser and a lint-free absorbent cloth to work out the old oil.
15 Refitting the ring
The foam ring should be ﬁtted dry as it’s much easier that way than if it’s dripping with fresh oil. Gently pinch the foam ring and ease it through the seal. You should be able to get the leading edge of the seal into position fairly easily. Carefully poke your index ﬁnger through the seal and feel around until you can sense the foam ring taking its seat at the foot of the rubber seal. When done, it’s onto the other one.
16 Lube the foam ring
The foam rings are designed to be soaked in a speciﬁc lubricant which keeps the rubber lip seals and stanchions running smoothly over each other. With the foam rings in position, tilt the fork (so the ﬂuid doesn’t just drip to the bottom of the sliders) and drip some ﬂuid onto the foam. Use your index ﬁnger to gently massage it in without moving the seal from its seat. (Float Fluid £10 for an 80ml bottle).
17 Slider refit
This might be the point at which your impatience to get the job ﬁnished takes over; don’t let it. The lip seals rely on being a very precise ﬁt and having clean, undamaged inner edges. If you hurriedly jam the sliders down onto the dampers, you can easily damage the seal edge. You also need to line up the damper rods with the corresponding holes in the sliders. Now replace the crush washers, base nut and rebound adjusters. Job done.
Straight shooter: All Fox Racing Shox forks come with a small threaded hole in the front side of the left leg, just where the arch begins. This is designed to hold the small 2.5mm Allen headed bolt, which attaches your front brake hose guide to the fork. Take care when ﬁtting this bolt to the fork as it’s very easy to get them cross-threaded.
A clean ﬁnish: At the end of each ride, give the outside surfaces of the fork a wipe over with a clean rag, possibly with a bit of water disperser like GT85. Obviously if the bike is ﬁlthy a wash is the ﬁrst step, but once it’s drip dried, give the fork a wipe to remove any stubborn dirt.
Rubber gloves: Fork oil is nasty stuff to get on your skin, so we recommend you invest in a box of protective gloves. We use the Park Tool ones which work well and cost about £25 for 100 pairs. That should last you a few years.
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