00:00suspension is what allows your wheels to
00:02follow the road and what keeps your
00:04backside and spine from getting
00:06it's also a topic that confuses a lot of
00:08riders and i'm guessing
00:10part of that confusion comes from the
00:12language used to describe suspension
00:14it's pretty unique so today on revzilla
00:17i'm giving a class on suspension lingo
00:19let's open up the shot manual
00:30spring rate preload sag damping
00:33compression rebound hard soft fast slow
00:37these are all words to describe the
00:40of suspension but if you don't know what
00:42they mean that is if you don't speak the
00:44language of suspension
00:46then they're not going to make much
00:47sense to you so grab yourself some index
00:49cards and a sharpie because we're going
00:50to dive into some vocabulary
00:53first flash card spring rate
00:56springs are quite literally at the core
00:58of your fork and shock and they're there
01:00to isolate your backside from jolts and
01:02keep your wheels in contact with the
01:04by allowing them to follow dips and
01:05bumps in the pavement
01:07spring rate refers to a spring's
01:09stiffness and it's usually measured in
01:12kilograms per millimeter for our metric
01:13friends the rate describes how much
01:16force it takes to compress the spring a
01:19take for example this 450 pound per inch
01:22shock spring if you put 225 pounds of
01:25force in that spring
01:26it compresses half an inch put 450
01:31and it'll compress a full inch you get
01:34the idea but with that load to
01:36compression relationship in mind it's
01:38easy to understand why having the right
01:39spring rates for your body weight
01:41is important for a comfortable and
01:42controlled ride you need springs that
01:44are soft enough to handle bumps
01:46but stiff enough to resist bottoming and
01:48excessive chassis pitch
01:49while braking and accelerating next up
01:52spring preload and this is a really
01:55important one to pay attention to
01:56because it's easily the most
01:58misunderstood piece of suspension
02:00spring preload is how much the spring is
02:02compressed from its free length with the
02:04suspension component fully extended
02:06take this shock for example it's not on
02:08the bike so it's not supporting any
02:10weight and it is fully extended and yet
02:11the spring is still compressed a little
02:13bit by this threaded collar here
02:15that is preload and as we learned over
02:17at the hydraulic press when you compress
02:19the spring the harder it is to compress
02:21so with preload we've already compressed
02:23the spring a little bit and that alters
02:24how much force it takes to initiate
02:27it also changes the total force required
02:29to completely compress or bottom
02:31that suspension piece look at it this
02:35motorcycle shock might have say three
02:37inches of travel at the shock body
02:39meanwhile the spring has six inches of
02:41travel so the spring has a lot more
02:43available range of motion than the
02:44component it's attached to
02:46and what spring preload allows us to do
02:48is alter the range of spring stroke
02:50that's used while riding
02:52so adding preload will help prevent your
02:54suspension from bottoming by requiring
02:56more weight to compress the spring and
02:58more preload can give the impression of
03:00harder or stiffer suspension
03:02but it's important to understand that
03:03all you're doing with preload is
03:05altering the effective range of spring
03:08preload's primary purpose then is in
03:14if you've ever been around a
03:15conversation about suspension you've no
03:17doubt heard the term
03:19sag it's our next vocab word it is a
03:21foundational suspension metric
03:23and it's the first thing you're going to
03:24check and adjust when setting up your
03:27sag is a measure of how much the
03:28suspension compresses from a fully
03:31unladen position and there are actually
03:35there's free sag which is the amount the
03:37suspension compresses under the weight
03:39and then there's rider sag or laden sag
03:42which is how much the fork and shocks
03:43settle with a rider on board wearing all
03:47the easiest way to think about sag is as
03:49a measure of how much suspension travel
03:51is available to extend
03:52down into dips in the road what's the
03:56as a general rule for street bikes ride
03:59or sag should be about
04:00one quarter of total suspension travel
04:02with free sag being about one-third of
04:05you can find your bike's total
04:07suspension travel listed in the owner's
04:08manual or you can always look it up
04:12if you're unable to achieve appropriate
04:14sag figures with your bike's available
04:16if your rider sag and free sag figures
04:20that's a pretty good sign that your
04:21spring rates are off ideally you want to
04:23run springs that allow you to hit your
04:24rider sag and free sag figures with as
04:27little preload as possible
04:29and now damping for starters let's
04:31clarify that it's damping
04:33not dampening you dampen a rag
04:37to clean your face shield you damp
04:41the word literally means to reduce the
04:42amplitude of a mechanical oscillation
04:45and oscillating is exactly what a coil
04:47spring will do if its action is left
04:50okay so damping is what regulates the
04:52speed with which a component compresses
04:55and we get damping with oil forks and
04:58shocks are filled with oil that's forced
05:00through a hole or some other restriction
05:02as the component compresses or extends
05:04the oil's resistance to flowing through
05:06that restriction creates a damping force
05:08and that acts as drag to slow
05:10down and control suspension motion take
05:13it's easy to move the plunger back and
05:15forth when it's empty
05:18but when you're drawing water up into it
05:20or trying to force water out it's harder
05:21to move the plunger due to the water's
05:23resistance to flowing through the tip
05:25the same thing is happening in your
05:26suspension without damping the inertia
05:29of a wheel hitting a bump might push the
05:31all the way up through its stroke and
05:33then it's going to pogo back
05:35damping is important because it keeps
05:38spring action in check
05:39which is critical to traction comfort
05:44basically you don't want your suspension
05:47behaving like a pogo stick
05:48now that you know what damping is the
05:50idea of compression damping
05:52ought to be easier to understand
05:54compression damping is the damping force
05:56that's created as the suspension unit is
05:57collapsing or compressing
06:00hit a bump grab the brakes etc and the
06:02subsequent load transfer causes the fork
06:04or shock to compress
06:06and there's a dedicated compression
06:07damping circuit that imparts some drag
06:10rebound damping on the other hand is the
06:12damping force that's in play as the
06:14suspension unit extends
06:15after being compressed it's also known
06:17as tension which is why you might see 10
06:19stamped on the top of your fork
06:21or the bottom of your shock alright so
06:23those are the common nouns used to talk
06:25about suspension but there are also some
06:28verbs and adjectives used to discuss
06:30some common ones are hard or soft and
06:34slow and fast do not refer to the speed
06:36at which you're traveling but rather the
06:37speed at which the suspension component
06:40if you hear someone say slow or fast you
06:42know they're talking about damping
06:44however if you hear them say hard or
06:46soft they might be talking about
06:48damping or springs because both damping
06:51can cause a fork or shock to feel hard
06:54with that congratulations you are now
06:56fluent in the language of
06:58suspension if not no worries it can take
07:01a little while for this stuff to sink in
07:02and you know maybe just watch the video
07:04on repeat until it does
07:06but in any case now you should at least
07:08be familiar with the basic vocabulary
