What is "Spring Preload", "Rebound Damping", & "Compression Damping"?
Nobody
"Rebound Damping Force", and "Compression Damping Force" for the front and
rear shocks, but unfortunately, it does not explain what the heck these
words mean.
I want to try experimenting with different adjustments, but before I do, it
would be helpful if I knew what I was adjusting. Can you guys please
define these three terms (in a simple layman way) for me please? Thanks!
GSJCB1
<<<Can you guys please define these three terms (in a simple layman way) for me
please? Thanks!
============================================
OK ..... you're request is my command:
----------------------------------------
"PRELOAD":
The distance that a spring (or set of springs, in the case of the front forks)
is compressed from it's fully relaxed free length, (typically by an externally
adjustable threaded mechanical device on modern sportbikes). This initial
compressing of the spring, is an adjustment that is utilized to control how far
the bike's suspension "sags" down, when the weight of the rider is applied, as
he/she sits on the bike. More "preload" (turning the adjuster CLOCKWISE) is
required if the rider is heavier than the "target" weight setup by the factory,
and less is required if they are lighter. "Target" weight for most sportbikes
is in the 150-165 lb. range. If a heavy passenger and luggage is to added to a
bike for a long trip, adjusting this "preload" stiffer (especially on the rear
shock) to compensate for the significant extra weight, is very critical to
maintaining the bike's normal handling characteristics.
----------------------------------------------
COMPRESSION:
Compression is the hydraulic resistance (oil movement through small restricted
passageways inside the suspension components : forks or shock) that is
exhibited when the bike hits a bump in the road, and the wheel is being pushed
upwards towards the chassis. This is adjustable by a small screw at the bottom
of each fork tube and at the top of the rear shock (on most modern sportbikes),
to provide more or less resistance to this movement. Usually referred to as
setting it "softer" or "harder", with "harder" being done by turning the
adjuster screw in the CLOCKWISE direction. It's really a matter of "rider
choice" as to where this particular adjustment ends up being set on a
particular rider/bike combination.
-----------------------------------------
REBOUND:
Rebound is also controlled internally by the restricted movement of oil through
small passageways inside the forks and shock. The only difference is that this
"rebound" hydraulic resistance is occurring when the wheel is moving in the
opposite direction ..... downward, away from the chassis (for example, when the
bike comes over the top of a rise in the road and the forks extend or swingarm
drops downward). This is also adjustable on most modern sportbikes, with a
small brass headed screws that are located at the TOP of the front fork tubes,
and at the bottom of the rear shock. Turning this adjuster in the CLOCKWISE
direction will cause it to "rebound" more slowly (more like molasses in the
winter time). If this adjustment if too "soft" (too far counter-clockwise)
the bike may feel like it's springing upward in a "Pogo-Stick" fashion, when
coming off of rises in the road or recovering from bumps.
As far as the starting settings go, if you haven't got much experience and are
unfamiliar with these adjustments, I'd suggest setting the compression and
rebound at the level specified in your owners manual first .... and making only
SMALL changes from there to suit your own tastes (1/4 turn increments at most).
----------------------------------------------
Regarding the "PRELOAD", if your weight is more than 190 lbs. I'd suggest
turning the adjusters slightly CLOCKWISE from the factory settings on the front
forks and the collar on the rear shock. If you're less than 150 lbs. I'd go
slightly counter-clockwise on each of these adjustments. I could get into the
details of describing "rider sag" and how to measure it and then adjust the
preload accordingly.... but from your request on "keeping it simple" I think
that might be a bit more than you're looking for right now.
Best of luck with your basic suspension setup on your bike, and happy riding!
Gary ("The Deerhunter 3")
Zak Smith
>"PRELOAD":
[ snip ]
>and less is required if they are lighter. "Target" weight for most sportbikes
>is in the 150-165 lb. range. If a heavy passenger and luggage is to added to a
>bike for a long trip, adjusting this "preload" stiffer (especially on the rear
Just to be clear: preload has no effect on spring rate, only ride height and
available travel.
-z
--
# Zak Smith, EE/Unix Geek, INTJ. z...@computer.org http://apollo.demigod.org
# Fort Collins, CO, USA. "Powers are cool." - me
GSJCB1
<<<Just to be clear: preload has no effect on spring rate, only ride height and
available travel.>>>
========================================================
You're absolutely correct in that statement, Zak. Thanks for the additional
input to insure clarity on the matter. The limited space available for a
posting here on the newsgroup, does leave lots of room for potential
misinterpretation.
Hopefully I didn't give the impression that the "spring rate" would be changed
by the increasing/decreasing the "preload" adjustment, in my original reply?
To add a bit of final clarity, the "preload" only results in raising the entire
resistance curve (from initial point of shock/fork movement, all the way to end
of it's effective travel), higher on the scale, but the curve (or "rate")
remains unchanged. The "rider sag" is the key factor that one is shooting to
optimize, with this adjustment.
If anyone got the impression that the "spring rate" would be changed by
adjusting preload from my original posting, I apologize.
Cheers and happy riding, and suspension tuning!
Richard Fay
>
> Just to be clear: preload has no effect on spring rate, only ride height and
> available travel.
But it can have that "perceived" effect if your bike has a rising rate
rear linkage.
Richard
+ICEPHREAK
> Just to be clear: preload has no effect on spring rate, only ride height and
> available travel.
For the mostpart true, but we wouldn't want our friend to die a sudden and bloody
death when he realizes his preload adjustment has altered his front-wheel rake to
the point where a simple sidewind would highside him.
(obvious exaggeration, of course)
Revised point:
Preload has no effect on spring rate. It only affects ride height, available travel
and, athough minimally, steering response.
For the complete lowdown, search out and buy The Sportbike Performance Handbook by
Kevin Cameron
http://www.amazon.com/exec/obidos/ASIN/0760302294/qid=930697775/sr=1-1/002-1245409-7024222
+ICEPHREAK
GSJCB1
<<<For the mostpart true, but we wouldn't want our friend to die a sudden and
bloody death when he realizes his preload adjustment has altered his
front-wheel rake to the point where a simple sidewind would highside him.>>>
===================================================
The intent in answering the original questions that were posed by the
originator of this thread, was to educate him on the basic "concepts" of what
these various adjustments (preload, compression and rebound) on a motorcycle,
are intended to accomplish. Hopefully any adjustments that he would ultimately
make, would be done in concert ..... front and rear. Thus if done properly,
the rake and trail numbers that would result, should be optimized for overall
bike control, performance, and resultant safety.
To minimize the risk of "going too far", I had suggested he start at the
settings indicated in his owners manual, and make only fine adjustments from
that position.
There's only so much information and detail that you can effectively share
within the limited space and capabilities of this electronic medium. We can
only hope for the best.
Cheers, and good riding for all.....
Bill Wakeling
>
>The distance that a spring (or set of springs, in the case of the front
>forks) is compressed from it's fully relaxed free length, (typically by
>an externally adjustable threaded mechanical device on modern
>sportbikes). This initial compressing of the spring, is an adjustment
>that is utilized to control how far the bike's suspension "sags" down,
>when the weight of the rider is applied, as he/she sits on the bike.
>More "preload" (turning the adjuster CLOCKWISE) is required if the rider
>required if they are lighter. "Target" weight for most sportbikes is in
>the 150-165 lb. range. If a heavy passenger and luggage is to added to
>a bike for a long trip, adjusting this "preload" stiffer (especially on
>critical to maintaining the bike's normal handling characteristics.
>----------------------------------------------
>
>suggest turning the adjusters slightly CLOCKWISE from the factory
>settings on the front forks and the collar on the rear shock. If you're
>less than 150 lbs. I'd go slightly counter-clockwise on each of these
>adjustments. I could get into the details of describing "rider sag" and
>how to measure it and then adjust the preload accordingly.... but from
>your request on "keeping it simple" I think that might be a bit more
>than you're looking for right now.
>
>Best of luck with your basic suspension setup on your bike, and happy
>riding!
>
I am 206 pounds and have never adjusted anything in regards to the
suspension on my bike. Based on your statements/explanation above,
should I be adjusting my preload? If so, how do I determine when it is
set correctly? I bought the 97 ZX6 used so I do not know if it was left
at factory defaults.
Bill
GSJCB1
<<<I am 206 pounds and have never adjusted anything in regards to the
suspension on my bike. Based on your statements/explanation above,
should I be adjusting my preload?>>>
Hello Bill,
Assuming that the fork springs and shock spring on your ZX6 are original, and
assuming that the previous owner was not close to your 200 lbs.+ weight and had
already done the "preload" adjustment to compensate ..... then YES, you should
be adjusting your preload!
As I mentioned in an earlier posting in this thread, it's pretty difficult to
walk someone through the whole step by step process, via a newsgroup posting
.... but I'll try to give you the basics.
You want the front suspension on your ZX6 to "sag", about 32 - 36 mm, from the
fully extended dimension, when your full riding weight is applied with you
sitting on the seat. You can slip a "zip tie" (plastic "ty-wrap") around the
smooth portion of your fork tube, and use it as a sliding gauge to indicate the
travel distance when you sit on the bike, with someone holding it so you can
put your feet up on the pegs. After the zip tie has been pushed down the fork
tube, by your weight compressing the suspension the required distance, you will
then get off the bike and have a friend pull upward on the handlebar to get the
front tire to be just skimming the ground, so that the forks are fully
extended. At that point you will take an accurate ruler and measure the
distance from the "zip tie", to the edge of the black rubber dust seal on the
fork tube. This distance should be the target 32-36mm of travel. If the
number is too great, turn the "preload" adjusters on the top of the forks
CLOCKWISE a few lines distance ....if it's too small of distance, go
COUNTER-CLOCKWISE. I suspect with your 205 lbs of weight, if the ZX6 has it's
stock fork springs installed, you'll need to screw the adjusters most of the
way down to achieve these target numbers.
In the rear of the bike, find a reference point on the tail section (you can
attach a piece of tape temporarily to the bodywork), DIRECTLY VERTICAL from the
center of the hollow portion of the rear axle. While you're still off of the
bike, have a friend pull up on the rear of the bike, to allow the swingarm to
fully drop to its extended length, and measure the distance between the center
of the axle and this reference point on the tail section (and write it down on
a piece of paper). Now have one friend hold your bike while you sit on it
with your feet fully on the pegs, and have a second friend measure the distance
between these same two reference points. The difference between the two
numbers is the rear "rider sag". You should set your preload on your rear
shock to achieve a "rider sag" measurement of between 25-30mm. Again if the
distance is too great, go clockwise with the preload adjuster (or a larger
"number" if your shock has the collar type with stepped ramps with numbers from
1 - 6 etc.. on it).
Well that's about the best I can do for you Bill, in a quick form. I hope
that I was able to give you at least the general idea on this process, and if
you have any specific problems when you try the job on your bike, drop a line,
and I'll try to fill in any gaps for you.
Cheers, and good luck with the bike!
Gary
CBRrider
I have a few questions regarding this topic. I just recently bought a 97 F3
from a guy that weighed ~140 pounds or so. I weight 195 and when
travelling on the highway, the bike reacts VERY harshly over EVERY little
bump. Even at 70 mph, it gets unsettling. If I was to ever go for a high
speed run, it feels like I would catch air over these little bumps that my
car doens't even notice. Last year, I had a 98 YZF600 which was bought new
and I left the suspension alone and it felt MUCH more composed and it soaked
up the bumps better even at ~140 mph. What suspension "tweaks" would you
guys suggest to get a smooth, well handling, and composed setup for someone
of my size riding a CBRf3? I've also noticed that this bikes "dances" more
from wind gusts and passing trucks than my YZF.... would this have something
to do with my suspension setup? It just feels like the whole suspension is
fubar, it feels soft and almost wallowly around corners, but extremely harsh
and uncomposed at speed on the straights.... PLEASE HELP!!!!!!!!! =]
GSJCB1
<<< I just recently bought a 97 F3 from a guy that weighed ~140 pounds or so.
I'd suggest you go back one posting within this thread, an read the information
that I gave about the process involved in setting the "preload" on the ZX6, for
the rider that was just over 200 lbs. Your situation is likely similar, and
would benefit greatly from getting the "rider sag" on your bike optimized.
Have a read, and give the process a try. You'll likely net some amazing
improvments in the bike's handling performance on your subsequent ride!
Cheers,
Big Dog
GSJCB1 wrote in message <19990704021153...@ng-fq1.aol.com>...
>In the rear of the bike, find a reference point on the tail section (you
can
>attach a piece of tape temporarily to the bodywork), DIRECTLY VERTICAL from
the
>center of the hollow portion of the rear axle. While you're still off of
the
>bike, have a friend pull up on the rear of the bike, to allow the swingarm
to
>fully drop to its extended length, and measure the distance between the
center
>of the axle and this reference point on the tail section (and write it down
on
>a piece of paper)
Could you measure this first distance using the centerstand? In other
words, while on the center stand, is the swingarm extended to the desired
length?
GSJCB1
<<Could you measure this first distance using the centerstand? In other
words, while on the center stand, is the swingarm extended to the desired
length?>>>
============================================================
ABSOLUTELY, Big Dog ..... this method would work perfectly, if your bike is
equipped with a center stand. Make sure the bike is rocked forward slightly,
where the rear tire is not resting with any of its weight on the ground, to get
a true "topped out" measurement.
The only reason I didn't mention this option in the original posting, is that I
mostly deal with the more "hardcore" sportbikes these days in my suspension
seminars, and these bikes don't offer the rider this luxury (for the sake of
weight savings, and potential ground clearance). If you've got it ..... by all
means "use it!"
By using the centerstand, you won't need any assistance doing the fully
unloaded portion of the measurement, but you'll still need help with the
"laiden" version. So buy your Buddy a beer, and have at it.
Good luck with the suspension tuning!
NOSPAMn...@gte.net
to bike? (42-46 mm front and 25-30mm on the back). Or is that a good
general rule no matter what bike your riding to adjust for your
weight?
GSJCB1
<<<Does the degree of suspension '"sag" that you stated differ from bike
to bike? (42-46 mm front and 25-30mm on the back). Or is that a good
general rule no matter what bike your riding to adjust for your
weight?>>>
============================================================
Very good question, that I'm glad to see shows you're taking this concept to
heart.
Well it's impossible to really target 100% of the bikes on the road with the
numbers that you repeated above. To be "spot-on" accurate, you need to take it
on a bike by bike basis. Between sportbikes and cruiser bikes there's some
differences, while there are significant differences between dirtbikes (or dual
purpose bikes) and streetbikes (13" of travel, vs. 5" of total travel
available).
The numbers I originally quoted (and you reprinted in your reply) were only
intended to give a "starting point", and then only for the general category of
modern (1990's and above) sportbikes (e.g. GSXR's ZX's, YZF's, CBR's, etc....).
The common rule is to set the front suspension's "rider sag" at something in
the neighborhood of about 30-33% of it's total travel, and the rear at about
20-25% of it's total travel (as measured at the center of the wheel). That
general formula, is where the 42-46mm in front, and 25-30mm in the rear, "rider
sag" numbers originate from. These numbers would calculate out nicely for a
bike like a 96-99' GSXR-750.
If a rider were to refer to their owners/shop manual for their streetbike, and
find out what the "total travel" dimensions on the front and rear of the bike
are ...... they could do the math to calculate the starting point to target for
the "rider sag" numbers, to be adjusted by the "preload" on their specific
bike. They could then go up or down from that starting point, to achieve the
desired handling characteristics of their choosing.
Sorry that I can't give all the answers, for all the bikes in such a posting,
but hopefully I've shared enough of the "tools" with you, to allow you to do
the remaining "busywork". If you lived in the San Francisco Bay Area, I'd
invite you to attend the free "Basic Suspension Seminar" that I'll be
conducting on the 23rd of July.
Cheers, and happy suspension tuning!
NOSPAMn...@gte.net
are others that glean this information also. I wish I could attend one
of your suspension clinics, but I'm not in the Bay area and it's quite
a ride from Dallas. Do you do other clinics as well, cause gems like
this make the newsgroups worth reading.
GSJCB1
<<<Thanks for the expertise. I really appreciate it and I'm sure there
are others that glean this information also. I wish I could attend one
of your suspension clinics, but I'm not in the Bay area and it's quite
a ride from Dallas. Do you do other clinics as well, cause gems like
this make the newsgroups worth reading.>>>
===============================================================
Hello "ncognito",
Glad to hear that you found the information on suspension setup personally
useful, and I hope that others on the newsgroup can also net some value for
their own application.
Regarding your question "do you do other clinics", well I do work as an
Instructor for one of the track riding schools ("DP Safety School") that
conducts their programs at Laguna Seca, Sears Point and other various tracks
here in the Northern California area. The classroom lectures that are taught
at these events, are often my responsibility, so I do get my hands into that
side of the motorcycle education arena as well.
I was fortunate enough to have a book published about a year ago (called
"SPORTBIKING: The Real World (The Advanced Riders Handbook)", in an attempt to
try to help share some of the advanced riding skills that I've been blessed
enough to learn over the many years I've been involved in this sport. While
it's nice to gain knowledge on these matters for personal use, it's that much
better to share them with others!
Cheers and happy riding ......
Gary ("The Deerhunter 3")
on sportbike riding techniques is an area that I get involved in during my
various motorcycle travels.
Big Dog
GSJCB1 wrote in message <19990706233453...@ng-cl1.aol.com>...
>I was fortunate enough to have a book published about a year ago (called
>"SPORTBIKING: The Real World (The Advanced Riders Handbook)", in an attempt
to
>try to help share some of the advanced riding skills that I've been blessed
>enough to learn over the many years I've been involved in this sport.
While
>it's nice to gain knowledge on these matters for personal use, it's that
much
>better to share them with others!
Gary,
Just bought your book (Borders had to order it directly from your publisher,
took a few weeks) last weekend ... didn't know you were the author. Hadn't
had a chance to start it, but hope to this weekend. It had good reviews on
Amazon.com -- although I'm sure you already knew that!
Anyway, thanks for the suspension info!
Big Dog