Intro
If you have never had your Cannondale lefty serviced or even
looked at by a Cannondale dealer, then the chances are your
fork is well overdue a service or at the very least a bearing
migration reset! Over a period of time, usually about every
25 hours of riding the main needle roller bearings migrate upwards
in their races and become misaligned to each other! This is
perfectly normal as they are free floating bearings between
an inner and outer race, it has little effect on the performance
of the fork with only a light metalic knock and a reduction
in travel of the fork, HOWEVER! if this is left unchecked the
fork can become damaged and may need new bearings and races
as they will become damages and in extreme cases could cause
a fatal accident of the fork failed drastically!
I am going to try to help you by showing you how to carry out
the simple proceedure of resetting your Lefty's bearing migration
plus how to change the fluid in your fork and just generaly
keep on top of the forks maintenance to unsure it lasts as long
as the bikes life (Hopefully).
Tools needed for migration and service:
- Workstand, (not completely necassary but much easier with)
- 19mm spanner
- 9mm spanner
- Shimano Hollotech II external bottom bkt tool (# TL-FC32)
- 24mm socket
- 5mm allen socket
- 4mm allen socket or key
- Torque wrench which goes from 7 Nm
- Cable tie cutters/ snips
- Syringe with measuring markers on the side (preferably in
CC but not important)
- Good quality 2.5wt fork fluid (more than 180 CC)
- Good quality fork grease
- Paper towel or clean rag
- Some thing to catch waste oil and something to dispose the
waste oil into
- Some kind of Alcohol or other evapourating cleaning fluid
that won't leave a greasy resedue on components such as a
brake cleaner spray
Most Importantly, Use the Cannondale Pdf as a reference
if something I have put in here doesn't make sense or you need
more help, there are more pictures on the Cannondale Pdf which
may help with assembly, see bottom of this howto guide for final
word and link to Cannondales Pdf.
Step one
Place the bike in a workstand then with the
fork still attached to the bike, release all the air from the
SPV schrader valve then use a 24mm socket to release the SPV
device in the bottom of the lower leg, DO NOT continue unscrew
this bolt head or oil will pour out!!!! Just release the initial
tension on the bolt head so that it is easier to undo once the
fork is removed.
Then using a 5mm allen key socket, remove the
front brake caliper and tuck somewhere out of the way, release
the self extracting front wheel hub and remove the wheel/ hub
assembly (do not try to remove the wheel until the nut is completely
unscrewed or you will strip out the last few threads on the
retaining nut/ spindle)
Release the top cap on the lefty with the Shimano
BB tool (# TL-FC32) but do not undo yet, you will probably now
have to release the 4mm allen screws on the face plate of the
stem to rotate the handle bar forwards in order to remove the
top cap on the Lefty, Wind in the Red rebound dial gently until
it is fully wound in (clockwise) counting the clicks so you
can return it to the same place when the fork is rebuilt! Once
done carefully remove the top cap on the lefty taking
care when you do, *If the fork does have bearing migration
there will be force on the cap when you remove it, so press
down on the cap and unscrew it a bit at a time so you are ready
when it pops up (mine was not a really strong force and I had
fairly severe bearing migration but just be aware)* you may
have to hold the red rebound knob to stop it turning while you
unscrew the top cap.
Next release the Lefty clamp bolts just enough
to enable the fork to be loose and carefully slide it downwards
to remove, removing and placing the bump stop safely aside ready
to be fitted when the fork is reinstalled.
Step Two
With the fork clamped (NOT TO TIGHTLY) in the
bike stand, push the lower section of the leg upwards to expose
the rebound and spring assembly and remove the two half pieces
at the top of the spring carrier place to one side safely (observe
that they have a words TOP printed on them, if not then place
down in a way so that you know which way up they go when you
rebuild the fork), unscrew the rebound knob BUT
be very carefull when you do as there are two ball bearings
and a spring inside the lower section of this that won't be
exposed until you remove it(best to use a rag to wrap around
it ready to catch the bits, then remove the rebound rod, it
should just pull up out of the centre! If it doesn't
then it is Siezed in like mine
was! Not to worry, it is easily fixable!
Now unscrew the two top rings that hold tension
on the main spring, the top ring is a lock ring for the bottom
ring so needs to be unscrewed first! Count how many
turns you unscrew the lower ring when you unscrew it as this
is the Preload/Sag setting that the fork is currently set to!
Wind them both up well out of the way, screw the plastic wrap
(DO NOT CUT OFF) that goes around the springs upper section
downwards so that you can see the 9mm flats on the rebound assembly
and using a 19mm spanner on the top carrier and a 9mm on the
rebound section flats, unscrew the two assemblies and lift off
the upper spring carrier then remove the spring (the bottom
has a white plastic bump stop attached) and place safely aside.
Unscrew top lock ring
Unscrew bottom lock ring to release tension
on the main spring
Lock rings released and wound upwards
Unbolt the upper spring carrier assembly
Spring with white plastic stop at the bottom
Now that the spring and upper carrier are removed
the siezed rebound adjuster rod should be easier to get to,
spray some (not loads) of unseizing spray (I used Wurth Rost-off
Ice, its german and kinda expensive but very good) I used a
small set of mole grips and gripped near the top of the rod
and gently tapped the grips to try to knock out the lever upwards
the also gently tapped the rod on the top back down and a 9mm
spanner to gently twist the rod in the rebound assembly, add
a little more spray and repeat all proceedures until the rod
has worked loose! DO NOT try to hurry this process or you will
cause damage to the rod and or rebound assembly, just be patient
and it will come loose, if there are marks left on the rod just
file them off and rub smooth with emery tape. Likewise a small
thin round file from a home hobby needle file set should clean
out the round assembly hole that the siezed rod was inserted
into.
Step Three
Hopefully you now have the unsiezed rebound
knob removed, (I'll come back to this later)
Now turn the fork over in the stand and unscrew
the SPV 24mm chamber assembly that you slackened off at the
beginning (did you?) you may need to use a 16mm spanner or socket
and keep winding the SPV volume adjust (red) hex at the same
time as you unscrew the 24mm so they both come out together!
Carefully remove the SPV chamber assembly, it is a little tight
as there is an O-ring to seal the system which may make it a
little tight to pull out of the fork (it will have fork oil
on it) place in a clean spot to avoid contamination!
Removing SPV chamber
Drain oil out
Now unclamp the fork and drain the fluid into
a suitable container, there will be a little oil in the rebound
assembly but it is only a small amount that a rag can cope with,
refit the rebound rod if you like? and use this to help push
the rebound assembly downwards and out of the bottom of the
fork (BE READY TO CATCH THE REBOUND ASSEMBLY ONCE IT COMES OUT
OF THE BOTTOM) again place this somewhere clean to avoid contamination,
in the fork upper leg should be the black rubber bump stop which
slides down onto and fits at the bottom of the rebound assembly
in the upper leg (the main spring with white plastic stop sits
on top of and against this when refitted)
Pushing out rebound assembly
Catch the rebound assemblt to avoid damage
Ok you are now down to the bare bones of the
fork apart from removing the bearings which is something you
really don't want to get involved in unless you really know
what you are doing! (don't be tempted unless you have done plenty
of reading up on how to strip/ rebuild the needle bearings in
a lefty, it is a nigtmare if you get the shims mixed up and
they don't go back exactly the same in exactly the same place)
Now cut the cable ties and unscrew the gaiter
boot and air filter clamps so that the boot and filter can be
worked up onto the fork upper and out of the way. If the fork
is extended and retracted you should be able to see the clean
sections on the bearing races, look at these races and inspect
for damage/ rust/ cracks (minor wear by light discolouration
is not a problem) but any of the afore mentioned problems and
you should get the bearing and races replaced! 88Aid is the
Premier Lefty Service centre in the UK and your local Cannondale
dealer should be able to send the fork off to them, I hear that
they turn around a fork service in about a week, so replacement
bearings shouldn't be a problem at all!
As well as looking for wear on the races you
will be able to see if any of them have migrated and are mis-aligned
to the others by comparing the cleaned away grease area! if
not then simply add some clean grease the the bearing races
and cycle the fork a few times to check the marks all line up,
see pictures for examples.
Slight darkening is not a problem but check
for rust and ridges etc
Migrated bearings!
Step Four
Resetting bearing migration is a bit of a pain
if it has been a while since it was done or has never been done,
not because its difficult to do but because it takes a fair
amount of physical effort if the bearings are very migrated!
To reset the migration simply hold the two sections of the fork
(upper leg and lower leg) and retract the lower into the upper,
then very quickly and with force extend them to their full length,
you should hear a top out knock, which apparantly changes its
pitch when the bearings are reset! personally I never noticed
any difference in the noise!
Check the entire fork length (measured from
the top of the upper leg by the threads for the top cap to the
bottom of the lower leg) its better to measure this when the
fork is stripped as it is easier to achieve and I found I couldn't
get it to full length before stripping the fork, it should measure
720-730mm, if this length is not achieveable then Cannondale
say that the fork may be damaged and need to be looked at by
an authorised repairer and should not be ridden!
Bearings reset, grease marks line up!
Step Five
Now that the bearings are reset refit the rebound
assembly taking care not to damage the light blue seal at the
bottom of the shaft! then using a clean object keep the assembly
up inside the fork lower while you refit the black rubber bump
stop down the shaft of the rebound assemly via the upper leg
bore (see piccy below)
Then refit the coil spring with the white plastic
bump stop down and over the rebound assembly so that the white
plastic bump stop sits against the black rubber bump stop, now
refit the upper spring carrier piece and add a little Loctite
242 to clean/ ungreased threads of the rebound assembly and
screw together the rebound assembly and upper spring carrier,
then using the spanners you used to undo the two pieces, resucure
tightly taking care not to over tighten! wind down the spring
preload lower ring until it contacts the spring then turn it
at least 1 full turn (or more if it was set
to more when you counted the turns when unscrewing it to strip
the fork) then wind down the upper lock ring to hold the lower
ring firmly in place! Wind the black shrink wrap that is around
the Main spring back up towards the top and apply fresh grease
to the spring! Carefully reinsert the rebound rod, if it doesn't
go fully home, DO NOT try to force it down, carefully turn and
waggle it or remove and try refitting it again until it drops
home fully,
Refit the two halfs to the upper spring carrier
(if you removed them?) stops with the words 'top' facing upwards
and extend the fork to make the two lock rings sit against the
top of the upper leg by the threads, add a small amount of grease
to the two halfs and refit the rebound assembly adjuster knob
but do not screw down hard till it stops, or if you do unscrew
it slightly by a quarter of a turn or so! Then refit the top
cap and secure down until it stops but do not use the tool yet
to nip it the last 1/4 turn. slide the fork boot back down to
its normal place and secure with the clamps and new cable ties
as required, slide the Air filter back down above the boot making
sure that the holes do not face the front/ rear, they should
be to the side so as not to be in the direct line of rain/ dirt,
and secure as with the boot!
Carefully refit rebound assembly without damaging
the
lightblue seal!
Black rubber bump stop.
top cap
Step Six
Now turn the fork over and carefully measure
out approx 155 CC of 85/150 fork oil (2.5wt) taking care not
to get any contamination into the fluid or fork, add the oil
to the fork through the lower leg opening, then take the SPV
chamber and make sure it is NOT decompressed and sucked inwards
(like a flat tyre) if it is then either press the Schrader valve
to make the rubber bladder pop back to its normal shape OR as
with mine its normal shape was slightly crimped and not perfectly
round, so I took my shock pump and added a very very slight
amount of air to make the bladder perfectly rounded (be carefull
as it will pop off and land in dirt if you add too much air,
it fits back on very easily so don't worry if it does pop off,
just make sure it's very clean before refitting) Now have some
clean wrag or cloth ready around the lower leg and very carefully
and very slowly lower the SPV bladder into the lower leg, when
it gets near to the bottom the excess fluid in the fork will
be forced out of the fork and run down the lower leg, fully
screw the SPV chamber into the lower leg and secure to stop
any leaks!
Take the fork out of the clamp and using a couple
of pieces of wood or a large socket that fits the lower leg
outer circumference (to stop you damaging the SPV chamber schrader
valve) press down on the fork to cycle the fork a few times
until all the fluid is circulated around the fork internals
and rebound assembly! Now turn the fork back over and clamp
again and remove the SPV valve/bladder, the level will have
dropped so you need to add more fluid! once added carefully
and slowely refit the SPV valve/bladder as before and secure
as before (makig sure it is NOT like a flat tyre remember, if
so add air like before), it should now be fully bled!
Step Seven
Slide the fork back into the clamps remembering
to refit the frame bumper before sliding the fork into the top
clamp! Secure the clamp bolts to 7 Nm torque (Alloy Leg only,
Not Carbon Leg) then secure the top cap a further 1/4 turn with
the special tool, refit the wheel and secure to 15 Nm torque,
then refit the brake caliper and secure, with the handle bars
resecured and the wheel back on the floor you can now torque
the SPV chamber to a setting of 10 Nm.
Set the Air pressure in the SPV Chamber to a
minimum of 30 Psi and a maximum of 100 Psi (what ever you had
it set to before you stripped the fork) and reset the round
to what ever you had it set to before stripping the fork! NOTE
the rebound knob only adjusts 14 clicks from Min to Max, the
clicks are hard to feel BUT the rebound knob should turn easily
and the click can be felt just about, if the rebound knob is
hard to turn and no end stops felt then the knob has been turned
in one direction too far and has become siezed, you will need
to remove the top cap of the fork again and screw the rebound
knob to a middle position and refit the cap, then taking more
care adjust the rebound to your desired setting!
And Finally
Here is a link to Cannondale's lefty
Pdf
Make sure you try the fork on the road at slow
speed to make sure it is functioning correctly and the brakes
work and all other functions/ components are safe, Before taking
the bike onto the trail proper!
NOTE!
www.27gears.com Accepts No Responsibility
for damage to any component or injury to any rider caused from
following this/ these guides to maintaining your fork/ bike/
components! you do so at your own risk, you should always where
possible have your bike repaired at an authorised repair centre!
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