LC ESA Fork Oil Change
I’d never changed oil in USD forks before, and that ominous black lead entering the LH fork cap looked particularly daunting – what kind of sensitive electrickery might lurk beneath. Looking at the BMW manual didn’t assuage my concerns at all, noting though that it is written for an audience of factory trained, white coated technicians working in a sterile environment with a wall full of special tools. The Haynes manual makes the job look more manageable, so I bought a litre of fork oil, prepared my tools, and off I went.
All went pretty smoothly, albeit slowly, as I am meticulous in these matters, and as noted above, this was a first for me. In terms of the result, I followed the Haynes specification and bought 10W oil (in my case, Castrol), finding later that the BMW manual specifies 7.5W. Fork oil is a black art – even the Castrol label acknowledges that each manufacturer specifies their oil differently, so oils with the same rating on the label may be quite different in performance.
Initially on riding, it was hard to discern the difference with the new oil. Over time, though, I have concluded that the front end is damped a little more stiffly now. There’s a less pronounced difference between Road and Dynamic suspension modes. I tend to use Dynamic mode less now, as in Road mode the front end feels a little more controlled and gone is that little tendency for the front to feel as if it is falling away on vigorous tip-in as the suspension settles. It may also be my imagination, but I think I can feel the road surface (ripples, coarse paving etc) a little more. I don’t mind the extra firmness, but those who value comfort more than taut handling may like to seek out a lighter oil for their change.
In addition to the usual tools required for working on these bikes (Torx bits etc) you will need a 32 mm spanner to loosen/tighten the fork caps. The torque required is pretty low (20 Nm), so a tight fitting shifter (i.e. where the jaws are perfectly parallel) can do the job (adjustable wrench for you ‘Mericans). My big shifter went walkabout somehow so I ended up buying a combination spanner, and now have what must be the biggest, shiniest spanner in the suburb. A single layer of masking tape should be placed around the fork caps to prevent marking from your spanner/shifter.
A large shifter would also be better than the multi-grips I used for the internal ring that tightens up against the LH fork cap, but is not critical as this is an internal part so minor marking, if it happens, is not of concern. I forgot to measure the required jaw width, but probably around 36 mm.
I made my ‘holding tool’ as specified in the Haynes manual from a couple of large L brackets, cut, drilled and tapped to suit, then screwed together, with M8 screws to engage the holes in the plastic spacer tube. Pushing down on the tool compresses the fork spring so you can (with your third hand) place a slotted washer above the tube to hold in place. The Haynes manual doesn’t say so, but it’s pretty much a two-person job to compress the RH fork spring THEN insert the holding washer. The furry newsprint photo hints at this requirement. I had no additional hands available so I had to improvise (family members enter the garage only to access the car or dump things for storage). I used a ‘ladder strap’ from one side of the tool, through the bottom of the forks, then back up to the other side of the tool. With this knowledge, I would have made the holding tool wider, the technique being to tilt the tool so that the side with the screwdriver is as low as practicable, nip up the holding strap, then push down on the other side to bring the tool level whilst tightening the strap. The screwdriver provided a roller for the strap to move over as the tool pivots while the strap is being tightened.
A further tip for the single-handed mechanic is to ensure you have a means of firmly holding the fork upright. I used a household step and then some webbing straps to lash the fork in position, with some high density foam between the fork and the step handle.
As noted in the Haynes manual, a short piece of garden hose is needed to hold the damper rod in the fully extended position during reassembly of the RH fork.
A little piece of PVC hose will help adjust the fork oil levels when you get to that stage. Because the required amount is a tad less than a litre, I was happy to siphon a little excess back into the bottle rather than to waste, just to ensure I didn’t run short.
During the disassembly process, keep meticulous note of which way things go – both in sequence and orientation (easy to get a spacer or ring upside down). On the RH fork a plate is specified at the base of the internals, under the lower washer – oddly, either mine doesn’t have one, or it stayed in place. The sleeve between the fork outer and inner did come out though – no mention is made in the Haynes manual, so just be aware of it.
I suggest servicing the forks one at a time and doing the LH fork first. Once you have fully disconnected the electrical lead (which stays attached to the fork) then tie back the ‘bars to the rear of the bike so they don’t flop around.
Actually, disconnecting the electrical lead was the one area that stumped me for a while as I couldn’t figure out what was holding it onto the mount that attaches it to the LHS of the coolant reservoir. I eventually prised the whole thing off so that I could find the little tab that releases the female connector (which is attached to the LH fork lead) from the mount. The technique is to first separate the connector by removing the lower (male) part after pressing down on the outer tab. Then get a small screwdriver in behind the open mouth of the female connector and push the little tab towards the front of the bike. The connector will then slide upwards off its mount.
Before starting work, clean any grime from the forks so the forks are not scratched by grit when removing. Make a note of the position of the forks and fork caps so that they go back exactly the same (once removed, you will see marks on the forks at the triple clamp openings). I used a screwdriver blade on the bottom clamp opening to prise it a little to ease the fork out/in – again, to avoid any prospect of marking the forks. Some years ago I recall a mate had his S1000RR forks serviced at a dealer I won’t name and they came back with zig-zag scratches on them from the removal process – to be avoided.
I used a scrap of aluminium I had at hand for the slotted holding washer. This was not optimum as the paint flaked off a bit under tension. However, once I perfected the hold-down strap technique, the washer was almost superfluous anyway; it wasn’t under tension during reassembly, so there was no risk of paint flakes falling into the oil.
When removing the springs from the forks, do so slowly so that the oil drains off pretty well as you lift them.
I flushed my forks with kerosene (paraffin for the Poms) for good measure. It drains off really well (better than the fork oil) and an engineer friend assures me it comes from the same oil stock anyway, so a few residual drops are not going to impact adversely.
The Haynes manual doesn’t say so, but rather than just let the new the fork oil stand for a while to allow bubbles to escape (they seem not to of their own accord …) I pumped the LH damper rod slowly until no further bubbles emerged (there’s a lot of resistance) and then re-measured the oil level. The RH damper rod is easier to pump.
I also scribbled out a list of dot points of all the tasks before starting – I find this easier to follow in the workshop than the narrative of the Haynes manual, having already familiarised myself with the latter. I’ll try to find time to type it up for posting here.
Overall, the task isn’t as hard as might be imagined. I’ve attached a few iPhone photos to help illustrate the above, although in the heat the phone kept shutting down, so the one showing the strap is a one-handed iPad photo – hence the blur.
Non-ESA forks are pretty much the same technique as the RH fork, but oil level specs are different.
Some key torque values:
Bottom yoke bolts 19 Nm (tighten progressively)
Fork caps 20Nm
Top yoke 19 Nm
Brake calipers 38 Nm
Axle 50 Nm
Axle clamp bolts 19 Nm (tighten progressively) 19 Nm