ODS vs. Noleen NR-1

[theycallmethefatman]

Is there a huge difference between an ODS shock and a Noleen NR-1? My winter mind is wondering if it's worth the upgrade F & R on my 657.
Thanks,
John

[kiwi]

from our own archives

7. What is a Noleen shock? What is a GDT shock? What is an ODS shock? How do they work?

         Noleen shocks

         Noleen is a manufacturer of coil-over mountain bike shocks as well as a motorcycle suspension "works" company         located in southern California. Noleen has been involved in cutting-edge suspension technology for many years, and has         successfully transferred much of the technology learned in the motorcycle industry to their mountain bike shocks, the  original coil-over MTB shocks.                                                                 

         Noleen shocks use (and have used for many years) a number of design features that are being copied throughout the     bicycle industry. The easily-adjustable coil spring makes preload adjustments and coil changes a snap. The internal    damper uses a proven technology that provides consistent damping and wide adjustability. The internals of the Noleen  shocks can be separated into five main parts: the seal head, main piston, floating piston, rebound adjuster, and  compression adjuster.

         The seal head is the part that keeps the oil in and the dirt out. It also provides lateral support to the shock shaft so the         shock always compresses evenly into the shock body. The seal head allows for a very, very small amount of oil to "stick"         to the shock shaft when it fully extends, thereby lubricating the shock shaft and providing smooth shock action.

         The main piston, which is forced through a reservoir of oil when the shock compresses, is a machined disk attached to         the shock shaft and surrounded on either side by a washer stack. Varying the number of washers and size of the washers         around the main piston increases or decreases the rate at which the oil flows through the main piston, thereby varying         the damping. Changing these washers to fit a person's personal preferences is referred to as "custom valving".

         One of the most important parts of a Noleen shock is the floating piston. This second piston, which it located near the  top of the shock body, serves three interrelated and very important purposes. First, the floating piston separates the    nitrogen and the oil. Noleen shocks, and others like it, require a nitrogen charge (200psi for all Noleens!). Injecting  nitrogen directly into the shock without a floating piston would work, but it would mix the oil and nitrogen and lead to frothing and bubbling in the oil. This gas and oil mixing adversely affects the even movement of oil through the main    piston. Secondly, the floating piston places pressure on the oil reservoir in the shock. Pressurizing the shock creates an         even oil pressure on either side of the main piston. If the pressure is not even on either side of the main piston, the oil         must reach a certain pressure on one side before it is forced through the valves. Controlling the internal pressure of the         shock maintains smooth main piston movement and ensures proper function of the valving. The third function of the         floating piston is to expand and compress the nitrogen slightly as the main piston moves into the oil. The floating piston         moves to accommodate the increased volume of metal (the shock shaft) moving into the shock. If the floating piston does         not move, the shock shaft may increase the pressure inside the shock to the point of seal failure or "hydraulic lock"         where the shock shaft simply freezes.

         The rebound adjuster located around the end mount varies the diversion of oil around the main piston valving. As the         rebound adjustment is increased, a pin is forced into a hole that allows oil to bypass the main valves. As more oil is         forced through the main piston, damping is increased. When more oil is permitted to bypass the values and move         through the alternative hole, the damping decreases. Both rebound and compression damping are affected by this         adjustment, but the changes in rebound damping are much greater due to the washer stack configuration.

         The compression damping adjustment on the NR-4 regulates the rate at which oil moves into the piggyback reservoir. While not adversely affecting the performance of the shock, the restricted oil movement slows the shock shaft movement         on compression and effectively "stiffens" the shock.

         Although while sounding complex, the Noleen shock is a user-friendly, easily serviceable shock. There are special tools that are needed for proper service, but having these tools, a shop can easily ser vice or customize a shock. Girvin strongly suggests that all work on Noleen shocks be performed by a qualified Noleen service technician.

[kiwi]

continued
GDT shocks

         The GDT shock ("Girvin Damping Technology") is a shock that was offered as an Original Equipment item on our 1996         and 1997 bicycles. It uses a similar technology to the Noleen shocks, but does not include an adjustable washer stack or         any external adjustments. The GDT, however, utilizes a floating piston and performs well because of this feature. This         shock was designed by Girvin engineers to be used on most of our 1997 lineup, but with the late-season purchase of         Noleen, was spec'd on only a few bicycles and will not be sold as an aftermarket item.

         ODS shocks

         The Girvin ODS (Oil Damping System) was designed to work in conjunction with our MCU springs and provides the         additional needed oil damping for the MCU shocks. ODS shocks are very simple shocks and do not utilize the same         technological advances that make the Noleen shocks superior performers. The ODS shocks lack a floating piston, and         therefore have a oil/air mix in the reservoir. They do, however, provide the limited damping required by MCU springs. Our         experience has been that the ODS units function acceptably well when fitted with coil springs in the front only.         "Clunking" noises and oil frothing are minimized in this application. Using coils in the rear, however, can and will cause         improper shock function and is not recommended by Girvin. Many performance enhancements have been suggested by         many people, but the only change that Girvin suggests be made to this shock is the replacement of the stock 30w oil to a         SAE 10w or 15w oil, if so desired. Continuing to use the MCU springs on the ODS shock will yield the best performance         from this simple damping unit.