Spring preload vs. air assist?
- Thread starter keen
- Start date
I'm not positive on the marzocchis but most air assist forks have a gas chamber to accomplish two things, to keep bubbles from forming in the fork oil and to create a bottom out resistance. What this usually does is create a progressive ramping, more progressive with more air pressure. Since your fork also has coils, the preload feature which just tightens the spring should work the same as a straight up coil fork. Although they should work fairly independently, if you crank up the air pressure too high, this will affect your preload to some degree because depending on the system (floating piston or not) you either create a bigger air volume that must be displaced or just a greater air pressure which must be compressed.
So to answer your question, I would set the preload using just the spring adjustment just like a normal coil fork. Once that is set play around with the air pressure to get just enough to avoid bottoming or to find a progressiveness that you like.
So to answer your question, I would set the preload using just the spring adjustment just like a normal coil fork. Once that is set play around with the air pressure to get just enough to avoid bottoming or to find a progressiveness that you like.
Its all about rate on a Marzocchi. Some forks/shock use a stable platform system to adjust compression damping threshold. In plain English: You set the damper to the speed you like it. Adjusting the air assist (spv) controls the amount of force needed to open it. This is how they filter out low-speed hits. But once enough force has hit the compression damper to overcome the spv, it works like normal.
What Marzocchi did was give the rider the ability to adjust how progressive the fork is. Some of their employees started fooling around with this setup a few years ago.
How it works: Any open bath fork has an air space above the oil. As the fork compresses, the space become smaller, meaning that the air pressure goes up, so that the fork gets more progressive. Now you can adjust this. Air is much more progressive than coil. This allows you to set you fork to be very plush through the first part of the travel, and then ramp up at the end, or remain linear troughout the stroke, or anywhere in between.
Onw way of thinking about it is that say your riding a very non-technical dh trail. You would want a more linear rate to use all your travel. Now say your riding a super tech/rough trail. You would want to add a few PSI to keep the fork from blowing through its travel.
What Marzocchi did was give the rider the ability to adjust how progressive the fork is. Some of their employees started fooling around with this setup a few years ago.
How it works: Any open bath fork has an air space above the oil. As the fork compresses, the space become smaller, meaning that the air pressure goes up, so that the fork gets more progressive. Now you can adjust this. Air is much more progressive than coil. This allows you to set you fork to be very plush through the first part of the travel, and then ramp up at the end, or remain linear troughout the stroke, or anywhere in between.
Onw way of thinking about it is that say your riding a very non-technical dh trail. You would want a more linear rate to use all your travel. Now say your riding a super tech/rough trail. You would want to add a few PSI to keep the fork from blowing through its travel.
MX bikes rejected this method of tuning twenty years ago.They just used the schreader valves on top of the fork to release air buildup.I have always got the best suspension performance by running a stiff enough fork spring so that it required only about 5mm of spring preload(preferably less) to get proper sag,then working with the oil level to control bottoming. That said,I do think with the shorter travel involved in mountain bikes air pressure added to the forks doesn't quite have the bad effects it does in 12 inch travel motorcycle forks.I have ran this same setup on my bikes(air caps plus coil springs) for about 3 or 4 years now myself but I setup the fork for agressive trailriding with zero added air pressure,I don't have to mess with checking the air just for a normal trail ride,and if I decide to do some jumping I can just pump a little in.
My fork is a 2002 Z1 freeride. I felt I was getting too much sag under compression. If I am doing a tight ,slow speed downhill singletrack my fork is compressed well into its travel. I have X heavy springs. I tried 5 psi of air and the fork got really stiff through out its travel. The suspension action is fine for most of my riding expect as mentioned above. Any advice? Thanx
I've got an '03 MX Comp, which is air-sprung. I recently got coil springs and coil-sprung-marzocchi-topcaps for it. My question: can I run the coil springs with the air-spring-topcaps so that I can use the air as an air assist to change progressivity like you guys just said?
You might try raising the oil level 5mm(springs out,fork bottomed,measure from top of fork) or even a shorter stem which would move you back off of the front wheel some.
That's just what I did with a 00 model Z4, a 01 Z5, and my 04 EXR,My DJ3 came that way from marzocchi.On the Z's I had to make my own preload spacers that would fit into the recessed part of the air cap,I don't know what the inside of the air cap looks like on a 03 mx comp,but my EXR has a flat surface on the bottom of the cap. I had to use rockshox judy springs to fit inside the thicker walled EXR,but they work fine.
The inside of the air-topcap is flat indeed, but why did you have to make your own preload spacers?