Cartridge vs Damping Rod Forks

[S750WP]

Cartridge Forks

 

I am often asked the question, "Why cartridge forks? What's so great about them?" Riders know they're better but don't know why. Let's clear the air.

Let's say you're bopping down the road, you charge into a corner and hit the brakes, the font dives radically and the bike feels like a wallowing pig. The later on you hit a square-edge bump and it feels like your wrists are going to break. Wait a minute, First the bike was too soft, then too harsh, What gives?

 

Well, perhaps the problem is your basic fork design. Internally, there are two types of forks, damping-rod and cartridge. If you have an old-style damping-rod fork, you're fighting and uphill battle (there are excellent solutions for that design but we won't get into that now).

 

A damping-rod fork is fairly simple: all that happens is oil is shoved through fixed orifices. This type of damping is call "velocity-squared" damping. The faster the wheel moves vertically, the more oil is shoved through the holes.

 

This is an important point. The speed of the bike is not nearly as critical as the shape of the bump. If you have 2-inch high bumps that's square-edged, the wheel has to move vertically very quickly, even at low speeds. On the other hand, if the 2-inch bump has a ramp that's 2 feet long, you can imagine that the vertical wheel velocity is much less. Now, of course, the bike speed does matter: if you double the bike speed over particular bump, you will double the vertical wheel velocity.

 

If the vertical velocity is doubled, the oil-flow rate through the damping holes is doubled. The interesting thing about fluid flow through fixed orifices is that the damping resistance is not doubled but instead increase with the square of the velocity; in other words, it increase by four times.

 

This situation is sometimes referred to as hydraulic lock. At some point the damping force increases so rapidly that the eintire bike defelects instad of the suspension absorbing the bump.

 

 

 

The problem is that "fixed orifice" damping-rod forks are too progressive. Fixed-orifice forks have very little "low-speed" damping and a lot of "high-speed" damping (vertical wheel speed). With very little low-speed camping, the fork dives excessively, and with a lot of high-speed damping you'll get a harsh spike: the worst of both worlds.

 

Another limitation is revealed during revalving. Typically, revalving a damper-rod fork involves enlarging or reducing the holes, or installing thinner- or thicker-viscosity suspension fluids (there are other solutions). This decreases or increase the damping through the entire speed ranges, to the bike is better handling the spike but will be better at handling the spike but will be even worse under hard braking, or vice versa. These changes will get you in the ballpark but almost always have compromises.

 

One solution is a cartridge fork. Mechanically, most cartridge forks use bending-shim-type construction instead of fixed orifices. This means there's a damping piston with a series of shims (they look like thin washers). The shims are stacked up against the face of the piston. When the oil flows through the piston, it forces the shims to deflect away from the piston face.

 

This creates damping at very low velocities. At very high wheel velocities, the shims deflect more and don't create as much high speed damping as fixed-orifice-type designs, meaning that the spike on square-edge bumps is reduced. With a cartridge fork, the damping is less progressive than with damping rods.

 

 

 

An added advantage of a cartridge fork is that the damping curve can be modified, or revalved, in a much more precise manner. For example, if you need less high-speed compression damping but the low-speed is perfect, the high-speed can be modified without affecting the low-speed compression because each circuit is affected by different shims when properly set up.

 

So, if your bike already has a cartridge fork, great. Inherently, the cartridge fork is headed in the right direction; it has more tunability and can be dialed in to your riding requirements and ability.

 

Does this mean any cartridge fork is better than any damping-rod fork? No, that depends on the valving and setup, including spring rate and oil level. Being a savvy suspension turner requires a knowledge of advanced engineering theory, the experience of extensive testing and art. something to remember is, the best you've ridden is the best you know.

 

Is there any hope for the damping-rod fork? Yes, but it takes more than a little creativity and...well, that's another story.

 

Paul Thede is the creative force behind Race Tech in Pomona, California, which has been modifying and creating suspension products for the last 10 years

 

 

 

--------------------------------------------------------------------------------

Magazine: Sport Rider

Issue : August 1994

[henRRy]

I was looking for this ...Thanks man .. Nice info...

[Guest rookie517]

now wonder i found tis articles so familiar

hehee

[Guest buja]

whoa haha, cool man....u actually spend ur time surfing fer such stuffs, unlike most of the guys here who surf for pornie stuffs...heh

 

dun lk at me !!!

[Guest mutoo]

inverted fork is which kind of fork arhh?

[Guest aiya4]

inverted fork is which kind of fork arhh?

 

haha, the one your bike is using now la!

[Andy]

ya, how to check what kind of fork we are using? If there anyway we can see or check to determine whether iszit a damping rod or cartridge fork?

[Guest mutoo]

 

haha, the one your bike is using now la!

 

i know rvf is inverted fork but my question is inverted fork is a damping rod or cartridge fork?

[S750WP]

Mine is a damping rod, check your service manaul and see wat fork you have.

 

Check this website for the original article with sketches of the difference.

 

http://www.racetech.com/articles/CartridgeForks.htm

[Guest ZZR-Pilot]

RVF is using Cartridge fork

 

Well that explains the bike's high price...

 

Anyway, I keep hearing about Gold Leaf Emulators that you can retrofit on damping rod forks to emulate cartridge forks. Sort of a cheap(-ish) upgrade if you want to race damping rod forked bikes.

[kata_killer]

But wat abt d cost???

[henRRy]

CBR R model is CATRIDGE FORK>.

 

 

[Guest rookie517]

CBR R model is CATRIDGE FORK>.

 

 

 

if it have a rebound clicker on top, it is a cartridge fork

if it has only preload, damping rod fork

 

be it USD or conventional

[tOngEh]

Super 4 damping rod!

[TSP Racing Team]

Originally posted by rookie517@Apr 30 2003, 05:08 PM

if it have a rebound clicker on top, it is a cartridge fork

if it has only preload, damping rod fork

 

be it USD or conventional

cartridge type fork can com with only the the preload on the top....

 

anyway, race tech has got the fork emulator done specifically for damping rod forks. done it on a gold wing and the results were good. couple with proper spring rate, oil level, oil vicosity, it has got the charactoristic of the cartrdge fork.

 

i also use other race tech products on my race bike...shock tech and tsp does all the setup for me. race tech has got some really cool stuff. go check their website at http://www.racetech.com. those people who have them in singapore are, shock tech suspensions, sporting motorcycles, teck tai, teo spray, unity...... go to tis ppl, they'll give you proper advise....

[The_Sheriff]

Originally posted by henRRy@Mar 23 2003, 12:39 AM

CBR R model is CATRIDGE FORK>.

 

 

:cheer:

Only the Fireblade CBR 4000 RRR model is the catridge type. The rest of the CBR400; L, N, an Hurricane series are the damping type.

 

[Non Stop Racing]

eh it be good if any expert here can list out the kind of forks of 2b 2a class 2 bikes and show a list out

 

eg sp- bah bah fork.

 

s4- dam fork

cbr-dam fork

rvf -cart

 

etc etc . any ?

[TooToo7]

Originally posted by Non Stop Racing@Apr 29 2004, 01:05 AM

eh it be good if any expert here can list out the kind of forks of 2b 2a class 2 bikes and show a list out

 

eg sp- bah bah fork.

 

s4- dam fork

cbr-dam fork, cartridge fork (R models)

rvf -cart

 

etc etc . any ?

[Guest quatryu]

I accepth with information:

The problem is that "fixed orifice" damping-rod forks are too progressive. Fixed-orifice forks have very little "low-speed" damping and a lot of "high-speed" damping (vertical wheel speed). With very little low-speed camping, the fork dives excessively, and with a lot of high-speed damping you'll get a harsh spike: the worst of both worlds.

 

Another limitation is revealed during revalving. Typically, revalving a damper-rod fork involves enlarging or reducing the holes, or installing thinner- or thicker-viscosity suspension fluids (there are other solutions). This decreases or increase the damping through the entire speed ranges, to the bike is better handling the spike but will be better at handling the spike but will be even worse under hard braking, or vice versa. These changes will get you in the ballpark but almost always have compromises.

 

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