Thursday, 21 February 2013

Marzocchi set up guide: understanding the basics

Break-in Period
Some forks may require 5-10 hours of use before the fork fully breaks-in. After the bushings, seals, and other parts have matched to each other, the fork will move smoother. The tight tolerances make the fork last longer and work better.

Sag
Sag refers to how much the fork compresses when the rider is in the normal riding position. Marzocchi recommends 10-20% of XC travel and 20-30% of DH travel in sag to provide the best overall ride. The easiest way to measure sag is to put a zip tie around the stanchion and then measure how much the fork compresses when the rider is in the normal riding position. Keep in mind that the normal riding position on a DH bike may not be correct on level ground. Refer to the following charts for reference.

Spring Preload
Spring preload can be done with the external adjusters on top of the fork. Preloading the springs will compress them slightly and increase the initial force needed to compress the spring. Bomber forks can use the maximum amount of preload from the adjuster and the fork will still get full travel. Spring preload is used to fine tune the spring rate to adjust for the proper sag measurement. Minimal spring preload is recommended for better performance and longer working life of the springs, so it is better to change to a stiffer spring rate than to add significant preload (10+ turns.)

Coil Spring
The spring rate of a coil spring refers to the amount of force needed to compress the springs in the fork. Marzocchi offers several different spring kits to coordinate rider weight and riding conditions. All springs are made from the highest quality chromium silicon (CRSI) or Titanium. Marzocchi use linear wound springs. Some older models used Pro-Wind springs which are progressively wound (coil wind gets closer together at one end.) Dual Rate kits use two compression springs per side. Put the longer compression spring on the bottom and then put the short spring on top to later ease disassembly. 

Air Spring
Air spring rate is the amount of air pressure that is in the fork. Marzocchi forks come pressurized for the average rider at about 35psi/3.0bar. Air pressure can be infinitely adjusted using a shock pump to fit rider preference. Be sure to use a pump that can accurately gauge air pressure in the adjustment range. Full air pressure charts can be found via www.marzocchi.com these recommendations should be used as a starting point. Air pressure may need to be adjusted according to riding style, frame design, terrain, and/or personal preferences and may vary between pump brands.

Rebound Damping
Rebound damping controls the rate in which the fork is able to extend. Most models all feature some type of external adjustable rebound damping. Rebound damping should be set fairly fast, but without causing a sudden, harsh force back to the rider. This will allow the fork to comfortably extend to full travel as soon as possible after impact.It is a good idea to get a feel for how the different rebound adjustments affect the fork. On forks that have external adjusters, try turning the adjuster all the way counter-clockwise to the fastest rebound setting and then quickly compress and release the suspension several times. Next test the fork with the adjuster turned all the way clockwise and then somewhere in between. This will demonstrate the differences between damping settings.
Older models using the SSV Non-Adjustable System can change their rebound damping with oil viscosities. Stock oil is 7.5 weight, so changing to a lighter oil (Example: 5 wt.) will increase the rebound speed. Heavier riders using stiffer springs may want to adjust their rebound speed with heavier weight oil. Be sure only to use a high quality motorcycle fork oil like Marzocchi’s Factory Fork Oil.
 
Compression Damping
Compression damping is the oil flow resistance felt when compressing the fork. Compression damping is categorized in two ways: low speed compression and high speed compression. Low speed compression refers to when the fork is compressed slowly and gradually, for example during rolling impacts and rounded bumps. High-speed compression refers to the resistance felt during multiple, hard impacts and square-edged bumps. It is better to be conservative while setting the compression damping because the spring offers resistance to compression as well. Too much compression damping creates a harsh ride because the suspension cannot compress rapidly enough to absorb large impacts. Compression damping is not a substitute for proper spring rate and should not be adjusted until the fork has the proper spring setup for the rider.
RC3 models feature both high and low speed compression damping. Turning the adjuster to the '+' or hard will increase the low speed compression damping and turning to the '-' or soft increases the high speed compression damping with both damping curves crossing in the middle.
Forks that do not have an external compression adjuster can modify their compression damping by changing the oil viscosity. Although most riders will be happy with the stock compression settings, some riders may prefer a different weight oil to coordinate with rider weight and/or spring setup. Keep in mind that changing the oil viscosity will change the entire damping range and will affect rebound as well. 

12 comments:

  1. Is there a way could make a 150mm bomber steer right on a kona stuff frame that originally came with a 100mm fork ?

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    1. I'm afraid not, a long fork is always going to make a frames head angle very slack.

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  3. I would like to drop my bomber from a 180 mm to a 150 mm for my setup on a sant Cruz blur tr, can I put a 10 and 20mm spacer in or do I need to find a 30mm spacer- thank you for all your help.

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  4. Hi, I have a set of 350 NCR's and have read about adding oil to decrease the volume of the air thus ramping up the progression. If I wish to add oil can this be done through the shrader valve and what oil would I use?

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  5. adding oil has the same effect as the bottom out tokens in RS forks and is the fork tuners oldest trick in the book!!! Just unscrew the top plug using a socket and add some SAE 7.5w oil, try 10ml at a time

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  7. Hi, can anyone tell me the min/max air pressure I can safely run in my 2011 bomber dj2's? Iv been looking for hours online and everywhere seems to have conflicting info :(

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    1. the recommended pressure for air-assist on coil forks is about 25psi as they become un-usable after this. The reality is the fork has the same seals as an air fork so in theory it could take 70-80psi, so you are not going to damage it using 30psi, it just wont move...

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