What springs do I need for my body weight?
Why can't I get full 105mm of travel?
Which spring and spacer goes in each side?
How long does it take for my fork to be fully broken-in?
What kind of maintenance should I perform to my fork and how often should I do it?
What exactly is HSCV and how does it work?
What is ETA and how does it work?
My ETA (Extension travel adjuster) stopped working. What's wrong and how can I fix it?
What is the proper way to measure the oil height?
What difference does oil weight (viscosity) have on damping?
What effect does oil height have on damping?
What is the Axle-to-Crown (AC) measurement of the Marzocchi Marathon?
The springs that come with the 2003 Marathon S are considered to be the "heavy" spring weight. These were designed around a "rider weight" (you PLUS all of your riding gear on) of 180-220 pounds. According to Marzocchi tech support, the spring weight for the stock springs is 6.5 kg/cm (which, should be around 36.4 lb/in if I've converted correctly). Below are my recommendations to get you close:
Rider Weight (with gear):
Correct Springs:
Comments:
140 and below Soft 140-160 Medium (Orange and Green) Through your local shop. Quality Bicycle Products Part # FK9851 (Marzocchi Part # 850346/c) 160-180 (1) Medium & (1) Stock "Heavy" (Red) 180-200 Stock "Heavy" Red Springs 200-220 (1) Stock "Heavy" (Red) & (1) Extra-Firm (Green) 220+ Extra-Firm Springs (Green)
For more in-depth tuning information on correct spring weight, see the Advanced Tuning page.
There are two things to check. First, proper spring choice is critical. Before you start messing with oil heights, oil weights, etc, be sure you are on the correct springs for your riding weight . You will save yourself a lot of time and headaches if you do this first!
The second thing to check is the oil height. See the oil change instructions page for directions. If your oil height is too high, then you will not achieve full travel. Once you have the right springs, then set the oil height to 50mm from the top of the fork leg (measured with the springs out and fork legs fully compressed). This oil height is the middle of Marzocchi's recommended height range and should get you in the ball park (45-55mm is the correct height range). If you are getting 90-95% of the travel once per really rough ride then I would leave it. If you aren't using that much travel, then try removing 2-3mm of oil at a time (a little bit goes a long way here).
For the 105mm model: The short spring and spacer goes in the ETA cartridge side. The length of the spring is right around 165mm. The small black PVC spacer is about 10mm long. The correct order is shown in the picture below.
The longer spring and spacer goes in the rebound cartridge side. The spring length is about 188mm. The longer black PVC spacer is about 55mm long. the correct order is shown in the picture below.
The fork will probably feel stickier than normal until the fork is fully broken-in. My fork seemed to be fully broken-in after about the first 50 hours of riding (about 3-4 weeks of regular riding for me). At that point, I highly recommend changing the fork's oil. When I changed the oil at 50 hours of use, there was quite a bit of metal shavings in the fork oil. This is normal, and it's probably caused due to tight tolerances and metal pieces inside the fork moving past each other. In addition, I recommend removing the bolts at the bottom of the lower fork legs and pulling off the lower legs from the upper tubes. Clean the insides of the lower fork legs and apply a very thin layer of Slick Honey suspension lube to the upper dust seals before putting the lowers back on (don't apply too much, or the grease may contaminate your fork cartridge and cause major problems). Your fork will now work smoother than ever!
I tend to error on the side of over-kill when it comes to maintenance because lets face it, bike equipment is anything but cheap! Here's what I'd do (keep in mind I ride about 4-5 times/wk.; 12-15 miles per ride in a dry and dusty climate):
Frequency: Recommended Maintenance: After Each Ride Wipe off excess dirt, dust, and mud from stanchions and dust seals. Every Other Ride Put a couple of drops of Teflon lubricant (like Tri-Flow) around the upper dust seals. Monthly
(About 50 hours)
Change fork oil Every 2 Months (About 100 hours)
Remove lower legs; clean; and apply a very small amount of Slick Honey suspension lube just under the dust seals. Do not go overboard with the lube. Too much will cause probs. Once per Year Inspect and replace oil & dust seals (I would recommend Enduro Fork Seals versus Marzocchi brand)
The rebound cartridge side of your fork also contains the HSCV which is unique to Marzocchi's high-end forks. HSCV stands for High-Speed Compression Valve. In the past, Marzocchi's have been criticized for "spiking" under big hits, transmitting the harshness to the rider. To combat this problem, Marzocchi came up with the HSCV to allow the compression damping "blow off" under big hits eliminating the spiking. The cartridge on Marzocchi forks is not user serviceable, so it's hard to tell exactly what's going on inside. However, after some careful examination of the cartridge and research, here is my best guess:
Forks with the HSCV operate in a very similar manner as a Koni Twin-Tube damper (for the car geeks out there). Inside the the damping cartridge is a piston and from that a rod extends up to the top of the fork (the rebound adjuster). The piston has four half moon ports cut into it with a one-way valve on the top of the piston (and possibly rebound damping shims on the other side) so that oil can flow freely through the piston during compression. The damping rod is hollow and oil can flow through it past the piston during compression and rebound. During the compression stroke, the damping rod pushes the piston down through the cartridge. Simultaneously, a quantity of oil is displaced by the volume of the damper rod entering the cartridge. Some of this oil is forced through four of the tiny holes near the bottom sides of the cartridge (see picture).
(I believe these are acting like a free bleed in both compression and rebound phases to act as low-speed damping). If the bump force is large enough, the oil won't be able to move quickly enough through the four tiny holes (I think only 4 of them pass oil through them until the HSCV opens) and the oil will force the HSCV shims to bend open exposing the remaining holes. The oil is forced moves into the area outside and above the cartridge unit. At this point, the fork is approaching full travel and since oil cannot be compressed, it is forced into the area underneath the preload caps. Here, a small pocket of air (this is where your oil height comes into play) is forced to compress which greatly ramps up the spring rate during the final 20% of your travel and prevents a harsh bottom-out.
In the rebound phase, oil is trying to move from above the piston (top of the cartridge) to below the piston. Oil is sucked back in from the fork legs into the cartridge through the tiny holes at the bottom of the cartridge. At the same time, the one-way valve closes over the top of the piston and the oil is forced to travel through the metered rebound orifice in the center of the cartridge rod and out the bottom of the cartridge rod. The rebound adjustment knob raises and lowers a cone shaped rod into the rebound orifice to decrease or increase rebound damping.
ETA is Extension Travel Adjuster. If you turn the little lever on the left fork leg (as you sit on the bike) clockwise, the ETA cartridge drastically slows the rebound of the fork. This makes the fork settle into its travel and limits the fork to 30mm of travel. When the ETA is working properly the 30mm of travel will be completely undamped and very "springy" on both compression and rebound. Lowering the front of the bike is helpful for long road or fire road climbs where you don't want a lot of fork bob. The other place that ETA is helpful is on very steep climbs where you want your weight forward to prevent the front tire from lifting off of the ground.
The ETA is actually a cartridge too. It relies on oil, just like your rebound / compression cartridge. Therefore, if the oil height is too low then the cartridge can suck in air into the cartridge which causes issues. This can also happen if you change the oil in the ETA side but forget to "prime" the cartridge with oil by cycling the cartridge rod several times. To fix the issue open up top caps, remove the springs and spacers, compress the lower fork legs fully, fill both legs about half full of oil, cycle the cartridges until you no longer hear air in them, fill the legs to 45-55mm from the top of the inner threads inside the fork legs, then reassemble.
The manual says 150 cc's (volume). Marzocchi technical support told me 45-55 mm from the top of the threads inside the fork legs with the springs removed and the fork's outer legs fully compressed. I've had excellent success using the height method. The easiest method to measure the height is to use a straw (of course, don't use it ever again). Take the straw and draw a mark around the middle of it. Now, measure down from your line 45, 50, and 55 mm and make marks at each increment. Lower the straw into the fork leg until your middle mark is even with the top threads inside the fork leg. Now, put your finger over the other end of the straw and raise the straw out of the fork. The oil should stay in the straw and you can compare the actual oil height compared to your desired oil height mark on the straw. If you put too much oil into the fork leg, just lower the straw into the oil, put your finger over the end and lift out the excess oil! For a picture of the oil-height measuring straw with appropriate markings click the picture:
Marzocchi uses black plastic PVC spacers inside the fork to help make up the extra distance between the top of the spring and the bottom of the preload adjuster. It is very possible/common that the black plastic spacer isn't quite long enough to take up the entire "gap". The is especially true if you don't use any preload on your spring (your preload adjuster knobs are fully CCW). Several people on mtbr.com have commented that their "zero" preload point is about 5 turns clockwise. My fork had this problem too. To fix the dead spot, I bought some PVC and cut new spacers that were 6mm longer than the stock pieces. So far the longer piece of PVC has allowed the fork to have a very slight amount of preload, even at full CCW of the preload knobs.
The quick answer is that heavier weight oil will increase both compression and rebound damping. Low-speed damping (on compression and rebound) is controlled by the two tiny holes in the bottom of the cartridge and the oil flowing through the center of the damping rod (mainly on rebound). During a large impact the oil cannot flow through the orifices quickly enough and the high-speed damping "blows off" by opening the shims in the bottom of the cartridge. A thicker weight oil will not flow as quickly through and will switch to (blow off) the HSCV shimmed valve sooner. Therefore, thicker oil will provide increased low-speed (rollers, bob, etc.), but not increase the high-speed damping as much. Be careful though, if you increase the oil weight too much then you may experience "spiking" (so much high-speed damping that the fork stops during compression and it feels very harsh during a big hit). During the rebound phase the thicker oil can lead to "packing", where the suspension cannot rebound quickly enough to absorb the next hit.
On the other hand, lighter oil will flow more easily through the tiny holes in the bottom of the cartridge and the oil will not blow off as quickly to the HSCV at the bottom of the cartridge. This will result in less low-speed damping (more bob and less control over rollers; like an old Cadillac with blown shocks), but not too much of a difference in high-speed damping.
Riders using Extra-Heavy weight springs may complain about a lack of rebound damping. Stronger springs need to be offset with stronger damping. This is one of the few instances that I would recommend trying a 10w oil instead of the stock 7.5w.
Assuming you are adjusting the oil height within the recommended range (45-55mm), then the oil height will not affect damping. Changing the oil height will only make a difference to the final 20% of travel. More oil (45mm) will cause the final part of travel to "ramp up" quickly so you don't bottom out harshly. Less oil (55mm) will cause the final part of travel to be more "linear" and not ramp up as quickly. Do not use oil height as a substitute for springs that are too light for your riding weight!
What is the Axle-to-Crown measurement of the Marzocchi Marathon?
My 2003 Marzocchi Marathon S in 105mm travel mode measures 487mm (19.2"). With the ETA engaged, the fork compresses down to about 459mm (18.1").
For some reason, Marzocchi's published measurements were quite different. They list the AC measurement at 478mm. I measured my fork several times, so I'm not sure why their fork is 9mm shorter.
The 2004 and 2003 models are nearly identical. The major changes were the upper preload caps & knobs. The 2004 model switched from traditional preload adjuster knobs to air-assist preload, which requires a air valve on the rebound knob side. Once you remove the top caps, the oil change procedure and tuning will be the same (except for the spring suggestions).
Standard Disclaimer: This site describes my experiences tuning and maintaining my suspension fork and this information is not an instruction manual. As always, use this information at your own risk. I am not in any way responsible for typos, misinformation, or any of your actions or results. Results may vary.
