thedeal
3515431368690009
The Showas are not official hrc factory kit but they are Showas factory kit and some in the paddock are saying better than Ohlins in some respects.
I know that Ohlins are the best for street bike (ss etc)
Showa,wp and Kyb for mx
<span style="color:#323D4F;Here are some things that may help to
better understand the new 2013 PSF forks. This applies to both the 2013
CRF450R and the 2013 KX450F.
<span style="color:#323D4F;What is the PSF?
<span style="color:#323D4F;It is a fork that is more of a pneumatic or
air fork than last year, but it is not a “spring-less” fork. Yes, it
DOES NOT have a large metal compression “fork spring” or set of fork
springs as you would find in a fork that we are more familiar with, but
that does not mean that it’s a “spring free” or a “spring-less” fork. In
fact, it would also be incorrect to refer to the 2013 PSF fork as a
pneumatic fork, as all fork designs prior to this have a pneumatic
component as part of their design and, well…we don’t want to lose any
respect for that.
<span style="color:#323D4F;Say what?
<span style="color:#323D4F;First off, the PSF still has a metal spring
in the fork called a “balance spring” or “top out spring”. In fact,
technically, it has four of these, two in each side. You could also call
this a “counter spring” as it counters some of the forces applied by
the compressed air. You will feel and see the effects of the
balance-spring if you remove the fork from the bike and let all the air
out – as the air is let out, the fork sucks down. No joke. More on this
later.
<span style="color:#323D4F;Now…the other part to this madness is
defining what a “spring-less” fork is because all forks and shocks often
have a mixture of metal springs and air springs. So…the 2012 CRF450R
had a total of six metal springs (not counting the “valving” mechanisms)
and two air springs. The 2013 CRF450R has four metal springs and two
air springs. And just to make things really interesting, the 06-12 YZs
and the 06-12 KX450F has four air springs, and six metal springs. Those
numbers will surprise or confuse a few suspension guys.
<span style="color:#323D4F;By the way, when you add or remove fork
oil, in the lower chamber of a closed cartridge fork or the open bath
chamber of the USDs, you are, in effect, adjusting the “air spring”.
<span style="color:#323D4F;So…no problem running about the track
calling the PSF an “air fork” but let’s not get too carried away in
thinking that this is some sort of radical approach to using air instead
of a spring.
<span style="color:#323D4F;So…air verses a metal spring?
<span style="color:#323D4F;What is really important to understand in
answering this question is the dynamics of progression. Progression is a
rate of change based on position. So…as you compress a fork, it becomes
harder and harder to compress. How much harder it becomes, each
additional millimeter, is a measurement of the fork’s progression rate.
Now...in most cases, suspension guys refer to progression as a change
that follows a linear rate, meaning that it doubles in force for each
equal increment in compression. So…if one inch of compression takes 10
pounds of force, then two inches of compression should take 20 pounds of
force. So…we usually think of linear rates as a normal or expected
path, and then use that as a guide to figure out how radical the rate
changes when it becomes non-linear.
<span style="color:#323D4F;So why does that matter?
<span style="color:#323D4F;So…now we get into some interesting stuff.
On the most part, metal springs are designed to progress at a linear
rate…and out of our control, the compression of air of a gas compresses
at a non-linear rate. So that’s means that you have to do some
interesting things to get a fork to behave like we want or need when the
metal spring is removed. This is the reason why the PSF has a
counter-spring – they are using a metal spring to counter the early
progression of forces that are related to the compression of air. So
there.
<span style="color:#323D4F;So what happens to a PSF if the fork seals leak?
<span style="color:#323D4F;In short, you’re hosed. In fact, it’s worse
than what people realize. Here’s why. First, most of the PSF forks will
be operating with a pressure rating between 33 to 40 PSI. Additionally,
there is not a lot of volume involved. What that means is that even a
small fork leak will have a dramatic effect. AND…making matters worse,
the more air you lose, the more the counter or balance spring is going
to want to pull (yes, PULL!) the bike down. So…if the fork seal leaks,
you are in trouble and most likely your day it done.
<span style="color:#323D4F;Could a leaky fork seal cause me to lose a race or have to pull out?
<span style="color:#323D4F;Very much. A change in pressure, of even
just a pound or two of air, is the equivalent of changing your forks
springs from something very stiff to something very soft. Imagine racing
and going from a .48KG spring to a .42KG spring within a few laps? That
could make certain jump launches and whoop sections very tricky if not
completely impossible to hit at any speed. You could also have a severe
failure which would quickly end your day….and could possible mean that
you won’t be going home in something that doesn’t have flashing lights
on top of it.
<span style="color:#323D4F;Yikes! What were they thinking?!?!
<span style="color:#323D4F;So…this is when it’s going to sting just a
bit. In the world of business and manufacturing there is this thing
called, “COGS”, which is short for “Cost of goods sold”. It is the cost
of the material that a manufacture uses to assemble the bike. So…if
Honda purchases a bolt for $2 and last year it cost $3, their COGS went
down $1 and that means they make $1 more per bike this year than last.
NOW…the driving factor for the PSF, (and the SFF) was to reduce to cost,
and the driving factor for reducing COGS was the recession that started
in 2008, which hit manufactures VERY hard. So...the PSF is not about
evolving the technology, it’s about reducing costs. HOWEVER, if you can
evolve the technology some small amount and also reduce cost, then it’s a
good thing. But…we are giving up reliability to gain a small margin of
performance.
<span style="color:#323D4F;Is the PSF a better fork than the standard SSS?
<span style="color:#323D4F;Not really…I mean, it’s here and it’s not
going away. The PSF can certainly be tuned to operate as a better fork,
and performance wise, it might be better out of the box as a SSS, but…in
the real world, in which most of us spend some money to tune our
suspensions, the SSS has a big advantage.
<span style="color:#323D4F;Is the PSF not an engineering marvel?
<span style="color:#323D4F;It is not. In fact, if you started with a
clean slate of designing a “spring-less” fork that offered maximum
performance, this would not be the design. This may have something to do
with why Yamaha is not on board with the PSF, (just assuming). However,
it’s a great compromise between performance and keeping the cost of a
bike low. The 2013-14 SHOWA SFF A-Kit is a much better example of a
pneumatic fork that is ideally engineered. There are also a collection
of high-end downhill mountain bike forks that offer much more
performance over cost reduction.
<span style="color:#323D4F;Does the PSF use the same main seal as other forks?
<span style="color:#323D4F;No. It is a new seal that seals better and
will last longer. However, it also has a higher static friction rating
than a 06-12 seal.
<span style="color:#323D4F;Could I use a standard seal from a 48mm KYB fork?
<span style="color:#323D4F;Yes…and no. Yes, in that it will fit and
work, but…as with most things, there is always a balancing act between
durability and performance. I'm sure we are not too far off from
suspension companies coming out with a "PSF seal" with various claims.
To be honest with you, SKF makes a 48mmHD seal, (part number KIT48KHD)
which would really be the best seal for the PSF. I would upgrade to
this...day one.
<span style="color:#323D4F;Is there something that can be done to keep the fork from failing if the fork seal fails?
<span style="color:#323D4F;Not really. I mean, you could create
something that seals the inner cartridge from the main seal but all that
means is that you just have two seals, which is not much different than
just having one seal with multiple sealing lips. So again, durability
and performance. And certainly, anything that happens with the fork tube
(nick or dent) is going to cause a leak regardless of the seal or
number of seals. I mean, this is a telescopic fork, so…you can run…but
you can’t hide.
<span style="color:#323D4F;Is there anything I can do to make a fork seal last longer and/or not fail?
<span style="color:#323D4F;Yes…don’t wash your bike.
<span style="color:#323D4F;Say what?
<span style="color:#323D4F;When you wash a bike you wash away a layer
of oil on the lower tube (and shock shaft) that actually helps the seal
to seal and to stay healthy. Additionally, when most riders wash their
bikes they leave water behind on the lower tube and due to the minerals
in hard water, that’s like leaving little sanding pads on the fork that
are destined to destroy a seal. The moral of the story? If and when you
wash a bike, clean the suspension chrome (front and rear) of any water
and then lube the tube. A rag with some suspension fluid is best. WD-40
is the worst, (it's a reactive solvent that destroys seals). And never
spray anything around a brake rotor.
<span style="color:#323D4F;Can I take a PSF and easily convert it to a metal compression spring type set-up, as in last year with the SSS fork?
<span style="color:#323D4F;Easy and low cost? No. You can’t simply
just drop in last year’s cartridges with a spring, which if you could,
would run you about $1000 if you purchase the parts from a dealer. In
other words, there is no quick fix to this issue.
<span style="color:#323D4F;Will the fork change as the outside air warms up, or as the fork warms up?
<span style="color:#323D4F;Yes…and this too will be a big problem for
some riders. All gases follow what is called “ideal gas laws” and that
means that as temperatures change, or as you change altitude, the
effective spring rate of the fork will change…and to be honest with you,
it won’t take much. So…in some cases, you may need to adjust the air in
the fork two to three times per track day ride. Even the use of the
front brake will heat the fork and cause the spring rate to change.
So…expect more build-up in the right fork leg than the left.
<span style="color:#323D4F;Will running nitrogen in the fork help?
<span style="color:#323D4F;Yes and no. Nitrogen will still rise in
pressure as outside air or any gas does, (still follows the same laws)
however, nitrogen inherently runs cooler because it takes more energy to
heat it up. Neat…eh?
<span style="color:#323D4F;What was the deal with Pro Circuit saying that the fork didn’t change much when they lost air?
<span style="color:#323D4F;They were not talking about the KYB-PSF,
but were referring to the 2013-14 SHOWA SFF A-kit that they are testing,
which is a very different fork.
<span style="color:#323D4F;So why does the SFF A-kit not fall down into the stroke when lower chamber pressure is reduced?
<span style="color:#323D4F;Because it has different chambers, each of
which are pressurized. So...redundancy. And I would assume that is does
not have any counter/balance springs.
<span style="color:#323D4F;Let me know what questions you guys have and I’ll try and address them.
<span style="color:#323D4F;Dave Johnson
<span style="color:#323D4F;SMART Performance Inc.