CBR600F3 Suspension set up Question
SuziRider
My suspension on my 95 F3 seems extremely harsh now that the bike has 20,000
miles on it. When it was new, it seemed to just float over the bumps,
maintaining good wheel contact through most road surfaces. I have it pretty
much at the stock settings still, since higher ones just make it worse for my
wt of 150 lbs in leathers.
How can I tell if it is time for a rebuild, rather than just in need of an
adjustment?
As the rear damper and forks and fluids age, how should the dampening settings
change?
GSJCB1
Hello Sue,
I saw your posting about your suspension woes, on your Honda F3. I know that
when you had ridden with us on Christmas day, you had mentioned that the bike
wasn't feeling right for you, but I didn't realize (at that time) that the bike
had accumulated so many miles since any suspension R & R had been performed.
At that time, I had given you a quick suggestion on front pre-load
modification, but it sounds like more work may be required to get things into
full working order.
Typically as a bikes suspension racks up the mileage, the oil in the forks and
shock gradually "breakdown". This breaking down of the oil, generally results
in a DECREASE in the amount of actual "dampening" (slowing) effect that these
suspension units will deliver. Your description of the bike's feedback as:
***********
"my 95 F3 seems extremely harsh now"
***********
would seem to contradict the typical softness that "tired" suspension
components normally exhibit. It is possible, however, that the suspension is
actually traveling into further into the limits of the stroke of the spring's
travel (due to the reduction in the amount of fluid dampening), and thereby
placing it in the stiffer portion of the "rising rate" of the rear suspension's
travel. ("Rising rate", means that due to the mechanical leverage changes that
are engineered into the rear suspension linkages on most modern sportbikes, the
shock appears to become STIFFER as the suspension compresses itself further
into it's total stroke). Many bikes come from the factory with "PROGRESSIVE"
front fork springs (though I'm not sure if the F3 does), which also seem to get
"FIRMER" as they compress more of their coils into "coil bind", further into
their stroke. The lack of fluid dampening, may once again be allowing the
forks to reach this range of their stroke, more easily, resulting in a stiffer
feeling over repetitive bumps.
I think that the most important thing to do on any motorcycle, BEFORE spending
a ton of money on complete rebuilds, revalves, and fancy "gold valves", is to
just do a good "BASIC SUSPENSION SETUP" exercise. This begins with setting the
static spring "sag" on the front and rear of the motorcycle with the rider's
weight in place. This one adjustment is SO critical to a bike's performance,
yet is neglected in the majority of street rider's bikes, due solely to
inexperience. The final adjustments are for compression and rebound dampening
(if the bike is so equipped), to place them in the proper working range for the
riding style of the rider. These adjustments can temporarily be used to
compensate for the faded dampening that the suspension parts are providing at
their original factory settings (if the unit's fluid and seals, are not TOO
badly deteriorated). IF the combination of ALL of these adjustments is NOT
capable of achieving the desired suspension performance, then it may be time to
result to at least a fluid replacement, and possible seal rebuild. The final
step of actually having more sophisticated modifications done, (i.e. "shim
stacks changed", fluid viscosity changed, stiffer/softer springs, etc...) can
be left as a final option, when all the low cost options have been exhausted.
I'd be happy to help you perform this "BASIC SUSPENSION SETUP" procedure, on
your bike (as it would take less than an hour), at your convenience. The only
reason it would even take the full hour, is because I believe in showing the
person what steps are being done (and how to do them), so that they can learn
from the experience, and be able to handle future adjustments without much
assistance. Let me know (via EMAIL) if you're interested, and we'll work out
the details.
Happy riding...............Gary ("The Deerhunter 2")
Robert Kennedy
In article <19971227060...@ladder02.news.aol.com>,
GSJCB1 <gsj...@aol.com> wrote:
> Hello Sue,
> I saw your posting about your suspension woes, on your Honda
> [ good general suspension advice deleted ]
The one thing Gary failed to mention is that one of the main reasons a
suspension can feel harsh is that some component is binding or
sticking rather than traveling smoothly. A number of things can cause
binding, but the most likely in the situation of a bike with 20K
street miles is that a minor tipover caused the fork tubes to get
tweaked in the triple clamps.
I would recommend checking the alignment of the fork tubes in the
triple clamps, or if you're feeling really ambitious, pull the fork
tubes out and check them for straightness before reassembling the
front end and checking to make sure everything is aligned right.
There is a chance that one or more components is actually bent if the
bike's been through anything worse than a minor tipover. In such a
case the bent piece(s) should be straightened, of course.
-- Robert Kennedy
GSJCB1
Hello Robert,
Thanks for providing some additional follow-up on possibilities for the
suspension "stiffness" that the rider was complaining about. You're absolutely
right about any mechanical aspects (i.e. bent/twisted fork tubes, etc..) of the
suspensions freeness of movement causing a symptom that would feel, to the
rider, like merely too stiff on the suspension adjustments. I hadn't really
considered those factors when I originally responded to her question, as her
bike appeared to have been "crash free" from it's appearance when we had ridden
together a few days prior. But appearance doesn't always prove to reflect the
history of what the bike may have been through in the past. Thanks for the
reminder.
Your comments made me also think deeper into any other possible mechanical
aspects that could cause a stiffness feel on the bike, besides just the fork
issue that you mentioned. In the rear of the bike, if the linkages for the
suspension have been subjected to lots of wet weather riding (especially after
20,000+ miles), the original factory grease may have been displaced to the
point where there is binding (or even rusting of the bearings and pins) in
their movement. This binding can result in the feeling of an overly slow
acting and "stiffer" feel to the rear suspension on the bike, than the actual
spring and shock dampening would provide alone. I have seen this occur on a
few older bikes that belonged to friends of mine, and was corrected by a good R
& R on all of the linkage components.
Lots of considerations, on what initially seems like such a simple issue, huh?
Happy riding.............Gary ("The Deerhunter 2")
P.S. Have you given any more consideration to the "track sessions" that we had
previously discussed, as I hadn't heard back from you?
SuziRider
Thanks for all the advice people have been sending me. Now I'm probably just
further confused! I guess the thing is to just monkey with the various
adjustments until it gets sorted out.
BTW: The forks are true, I had them checked at the shop not too long ago[ after
I hit a pothole and dented a rim], and the seals ,etc all seem to be fine from
inspection. The bike was throughly gone over at a 16,000 miles/4+ hour service
not too long ago (have 20k on it now).
It is probably a matter of the factory suspension being set for a rider of 165
lbs, while I weigh about 20 lbs less now, and most guys of the helpful variety
weigh about 175-205(or more), so they just know from their personal experience
that suspension always has to be cranked up, not lessened.
SirGarytheDeerHunter has suggested an adjustment in the sag may be in order,
which is probably true.
I was wondering if anybody else who is a hard-core sport rider whose weight
has changed around can let me know what adjustments they had to make to their
bike's suspension. What has to go up, and what down? Do you need more
dampening with less preload to counter the added 'springiness', or less to
match the softer spring rate? And would that create excessive dive? It is an
endless circle....
Thanks,
Sue
GSXR11JOSE
Hi Suz.
Let Gary help you with your suspention "set-up". He helped me with mine. He
knows what he is doing. After setting up mine it made a HUGE difference.
Jose
andy.b...@aspect.com
In article <19971227230...@ladder02.news.aol.com>,
suzi...@aol.com (SuziRider) wrote:
> I was wondering if anybody else who is a hard-core sport rider whose weight
> has changed around can let me know what adjustments they had to make to their
> bike's suspension. What has to go up, and what down? Do you need more
> dampening with less preload to counter the added 'springiness', or less to
> match the softer spring rate? And would that create excessive dive? It is an
> endless circle....
I don't know about the "hard core" part, but my weight has changed
(upward) over the last couple of years. It didn't change the ride
quality much, but did affect the ride height at each end, which created
different sensations, such as slower steering and a tendency to wallow
around the steering head in sweepers with a dip in the middle (because
the rear spring was too soft). As far as I can tell, from all the stuff
I've read and all the people I've talked to, you can divide the various
adjustments into two groups: those with absolutely correct or incorrect
settings, and those with correct settings relative to rider preference
and perhaps road conditions.
Before changing anything, make sure you have a record of the stock
settings so you can return to them if need be. Sometimes the manual will
have those settings, while other times you must record the current
settings by noting where the preload is set, then counting the number of
clicks of compression and rebound. You really should do this to
establish a reference point. If nothing else, it'll make you feel better
as you start to monkey with the settings.
Absolute Setting - Preload: ---------------------------------------- Most
people agree that preload should be adjusted so that the first 1/3 of
suspension travel is used up with the rider sitting on the bike
statically. This doesn't seem to change over time, unless the rider's
weight changes substantially. This is the most critical adjustment and
can best be made with the help of two friends; one to hold the bike
upright with you sitting on it and the other to take measurements. This
setting will involve the most work to arrive at, but once done, you
shouldn't have to change it.
To make this adjustment, move the bike to a level, well lit place. The
first thing you want to do is establish reference points to measure wheel
travel from. For each end of the suspension, find a fixed point on the
bike and on the wheel from which to take measurements. In the front, you
might use the bottom of the lower triple clamp against the top of the
fork slider. In the rear, you might use the top of the swingarm right
above the axle, against a fixed point on the frame or bodywork directly
vertical from the axle. As you sit on the bike these points will move
relative to each other, and it is the difference between the distances
that you're going to adjust.
First, measure the distance between the reference points with the
suspension unloaded. For this, you need two people, one to unload the
suspension and the other to measure the reference points. To unload the
suspension, you can lever either wheel off the ground by tipping the bike
up onto the side stand. Measure each end this way and record their
values. You might label them F_EXT and R_EXT, for "front extended" and
"rear extended", respectively.
Once you have these measurements, get the third person to hold the bike
upright while you sit on the bike, dressed for a ride. Both brakes
should be off to let the bike pivot freely on its axles (part of the
reason for the level place). You'll want to take two more measurements at
each end of the bike. You want to negate the effect of "stiction" in the
weighted measurements. To get the first measurement, let the bike extend
to its natural sag without your weight. Then slowly ease onto the bike
to avoid bouncing the suspension. Measure the reference points and
record the distance at each end. You might label them F_WT_1 and R_WT_1.
Then, while you remain seated, have the "measurer" depress the
suspension further and let it rise slowly, again without bouncing.
Measure the reference points again and record the distance. Label them
F_WT_2 and R_WT_2. These distances should be a bit different, owing to
"stiction" in either the fork or shock. Average the two values for each
end to get the midpoint: F_WT_MIDPT = (F_WT_2 + F_WT_1) / 2 R_WT_MIDPT
= (R_WT_2 + R_WT_1) / 2
Now, calculate the difference between the midpoint values you just got
from the distance of the fully extended suspension. That difference
should be one third of the total suspension travel for that end of the
bike. Your owner's manual should list the suspension travel figures; if
you can't find them, a dealer can tell you. Adjust the preload up or
down as needed to raise or lower the bike under your weight until you get
measurements at a third of total travel.
If the front total travel is 4.25", then 4.25 / 3 = 1.42 = F_TARGET
If the rear total travel is 5.25", then 5.25 / 3 = 1.75 = R_TARGET
If (F_EXT - F_WT_MIDPT) > F_TARGET, the preload for the front is too
low, If (F_EXT - F_WT_MIDPT) < F_TARGET, the preload for the front is
too high, If (R_EXT - R_WT_MIDPT) > R_TARGET, the preload for the rear
is too low, If (R_EXT - R_WT_MIDPT) < R_TARGET, the preload for the rear
is too high.
Relative Settings - Compression & Rebound
---------------------------------------------------------------------- To
some extent, compression and rebound are adjusted "to taste." The best
setting for you *may* be affected by preload adjustments, but probably
not much if the adjustment wasn't too radical. The damping rates are an
adjustment to control the speed with which the wheel moves in response to
the road surface rising or falling away. The factors working on the
suspension are things like how sharp the bumps are, how fast you're
going, how much the wheels (and other "unsprung" parts) weigh and how
much spring tension (preload) there is. I usually start with the stock
setting, then adjust compression or rebound independently, while checking
for certain behaviors from the bike. This part isn't especially
scientific (at least the way I do it), and you may be able to get more
detailed advice from others.
First, understand that the damping rates will be optimized for a certain
ride quality. A setting which works for a big hit at low speed may not
be the best for closely spaced ripples at high speed. The damping needs
to be set for the ride quality that you most prefer. If you're looking
for a "less harsh" ride quality, you may want to have generally softer
compression and rebound settings. If you're racing, you tend to look for
the settings that give you the best traction on the greatest percentage
of the track. Ultimately, compression and rebound need to be balanced to
each other.
When setting compression, I personally tend to turn it up until I find
the point where a hit (on the type of terrain I'm most concerned with) on
the leading edge of the bump doesn't upset the chassis. It's "seat of
the pants," but you can feel when the chassis starts to pitch over the
bump. Try to disregard what happens on the trailing edge of the bump, as
you'll deal with that through rebound. Setting compression this way
tends to give a setting which will allow the wheel to track the leading
edge of the bump all the way to the top without going any higher. The
wheel may go higher if the damping is too soft, because the suspension
will continue to move. You won't feel it much through the chassis in
this case. If the damping is too hard, the wheel may also go too high
because the chassis pitches upward and you're essentially jumping the
bump as a result. You *will* feel this. So to make it simple, I keep
turning compression up until I feel the initial hit, then back off a
click or two.
I usually set rebound last. Rebound's job is to return the wheel to the
ground without upsetting the chassis. Here, I typically turn it up until
I feel the bike drop a bit after hitting the bump. If you go over a
series of fast bumps with this setting, you'll feel the suspension "pack"
as it gets progressively lower with each hit. Then I back it off to the
point where I don't feel this. If you're riding near the traction limit,
you'll also notice an increase or decrease in grip, which correlates to
how accurately your suspension is keeping the wheels on the ground.
ab
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