How do you tell the difference between cartridge and dual chamber type forks?

[RickMatthews]

How can you tell the difference by looking at the two? Also what would my forks be on a 2003 125sx? Also are they the only two types of forks or is there more? Thanks.

[mikes300]

the caps are different, i dont think any of the KTM's had the twin chambers until 2007 though, definatly not on your 03, they were all the same then.

Mike

[Gary jp4]

There my be a way to tell externally but I don't know. Oh yeah the caps are different.

Those are the only two types I know of except if you go back far enough you get into conventional forks with the inner tubes on top and the outer tubes on the bottom. All the newer ones are refereed to as inverted forks. I think all the conventional forks were open chamber. The progression was conventional, inverted, and then inverted closed chamber. All the Jap MX bikes are closed chamber and have been for several years. KTM was kind of late in following their lead into the closed chamber forks.

Yours are open chamber forks.

You can look at a parts list from one of the online dealers like Munn or KTM World, and others.

Here are yours and you can see that there is no closed cartridge inside, only three different tubes plus the adjusting tube and dampening rod that just goes inside loosely as separate parts and assemblies. So they are called open chamber forks. When you pull the caps off every thing is open.

Here are the front forks from a 2008 125SX. 2007 was the first year with closed cartridges. You can follow everything with the lines that show what goes into what from the cap at the the top middle down and then back up to the left and then down to the bottom middle is all in a closed cartridge with the cap going into this. This all screws down into the outer tube and comes out in one assembly as a closed cartridge like most of the later Jap MX bikes.

[Gary jp4]

Well there you go as usual I am late with the long answer.

[RickMatthews]

I also heard you can tell the difference between the caps I can't tell the difference.

I dont know what he means in the difference between the two.

So mine is the open chamber forks? Does open chamber mean the same as cartridge? And closed cartridge means the same as dual chamber? I am trying to figure out which of those videos to watch.

[Layton]

Open chamber is the old style and is what is on the 2003.

All the rest are various names for basically the same thing

[mikes300]

I also heard you can tell the difference between the caps I can't tell the difference.

I dont know what he means in the difference between the two.

So mine is the open chamber forks? Does open chamber mean the same as cartridge? And closed cartridge means the same as dual chamber? I am trying to figure out which of those videos to watch.

yours are the same, pretty much, as the top video, your right they all have a cartridge, just weather its open or closed, yours are open, yes closed are also called dual chamber, because there is oil in the cartridge, and seperate oil in the outer chamber.

Mike

[Gary jp4]

The really old stuff, still on some road bikes, were called dampening rod forks in which the damping action came solely from oil being pushed through sets of small holes. A problem with a damping-rod forks are they can be soft and under damped during low-speed movement and suddenly turn harsh over the small stuff (like KTM's but worse). This is because oil forced through a fixed-size hole offers resistance related to its velocity. When the oil is barely moving, there's little resistance, but when forced quickly through a small hole the resistance shoots way up.

Newer forks like yours with pistons and shims that move through sleeves or inner tubes (cartridges) inside the forks are called "open chamber cartridge forks", and sometimes "open chamber" or "open cartridge" forks. These are what you have. The whole inside of the fork is open to the oil and airspace inside. A cylinder or cartridge (because it is not part of the outer tube of the fork) inside the lower section works like an open-chamber shock absorber. A piston slides through this cartridge, which is submerged in the oil. The small, flat metal shims that are stacked on top of the piston are forced through the oil as the suspension moves. This in turn forces the shim(s) away from the piston face. The thickness and diameter of these shims determines how much force is required to move it out of the way, and therefore how much damping you get. These shims can be fine-tuned better then a dampening rod to offer resistance even at low suspension speeds allowing more even dampening, but also "blow off" sufficiently to allow the wheels to move rapidly in response to sharp bumps.

The newest ones are called "dual chamber closed cartridge forks" for the reasons I gave above. Sometimes shortened, or in slang, and called "closed cartridge", "closed chamber", or "dual chamber", and what you are calling "twin chamber". The work the same way as, and are, cartridge forks, but the inner chamber is like a separate shock absorber within the fork tube.

Someone else might better tell why "dual chamber closed cartridge forks" are better for MX, but I think it has to do partial with using a pressurized closed chamber to prevent fluid foaming and keep it contained in the smaller dampening unit. This frees up the rest of the fork for heat dissipation, springing, and bushing. But, they do seem to be better. I don't think the off road/enduro folks care as much and in some cases even like the open chamber set up better.

[Gary jp4]

The forks in the first video are most like the ones you have. The ones they call cartridge forks.

[Rip Wheeler]

How can you tell the difference by looking at the two? Also what would my forks be on a 2003 125sx? Also are they the only two types of forks or is there more? Thanks.

I think the bound and rebound adjutments are swapped backwards for dual chamber forks ie rebound on the bottom, compression on the top. I may be wrong though.🤣👍

[Cactus73]

Open chamber or cartridge forks have the rebound adjustments on the top of the fork. Twin chamber forks have the compression adjustment on the top of the forks. Your bike has the open chamber type.