Breaking this down we have the following items under the cap (1); the chrome tubes that attach to the triple clamps (8) are the “fork tubes” or “stanchions”. The lower section that slides up and down the fork tube (16) is conveniently called a “slider”. As mentioned above, there is a spring (5) that support the weight of the rider and motorcycle, oil (not shown – but in there) to create damping (motion control) and the damping rod (7) that controls the rate of motion of the forks. There is a spacer (3) that is used to preload the spring to control/tune the sag of the suspension and seals (11-13) that keep the oil inside the forks. For the majority of fork maintenance, only parts 3 through 5 are removed and the oil is replaced. The o-ring (2) is attached to the cap. Parts 6 through 15 are bolted to, or pressed into, part 16 and only get removed if you take the steps to remove them.

As you can see, it’s a fairly simple design with few parts. Let’s take an in depth look at the springs. Motorcycle springs typically come in two types; linear which are a single-rate spring, and progressive which are a multi-rate spring. As the name implies a linear or single rate spring maintains its rate for the full compression of the spring. If the spring is rated at 20 pounds per inch (expressed as 20 lb/in) it takes 20 pounds to compress the spring one inch. The second inch of travel requires an additional 20 pounds of force, and so on until the spring has reached its mechanical limit of movement. A progressive spring is one that starts as one rate, but finishes at another rate. For example the spring may start as 10 pounds per inch and finish at 30 pounds per inch. This would be expressed  as a 10/30 lb/in spring.

The Savage comes equipped with dual rate progressive springs from the factory. This type of spring is typical for conventional damping rod forks because a damping rod with fixed orifices, in and of itself, has no means of adjusting the speed of movement (compression and rebound damping). It can only provide a fixed amount of motion control. A progressive spring requires additive amounts of force to compress; this allows for fast movement in the early part of the fork stroke and as the fork compresses the spring requires additional force to achieve the additional movement.

The damping rod (7) is a tube with an opening on the top and a pair of small holes (shown on the drawing as the orifice) on the lower portion of the tube. The damping rod has a seal (6) and acts as a piston as the slider (16) moves up and down the fork tube (8). As the fork is compressed the piston moves/forces oil through the damping rod from the top of the tube through the smaller holes on the bottom. This creates resistance inside the fork itself. This resistance to movement is called damping; compression damping as the fork compresses and rebound damping as the spring in the fork seeks its static or neutral position.

How did Suzuki select the rate of the spring and the size of the holes in the damping rod? They estimate an “average rider” across their vast market. In this case a rider who weighs around 140-150 pounds. If this is you, your springs have been designed with you in mind. If this is not you, your bike is most likely under-sprung for you. Also, you may weigh 150 pounds, but you have added equipment and accessories to the bike that increased its weight. If this is the case, the combined weight of the bike, accessories and you are now outside the design limit of the springs.

From data found on the suzukisavge.com site it would appear that the OEM spring are a dual rate progressive spring with an initial rate of 19 lbs-in  ( 0.34kg/mm) from its static position to 4 inches and then 23 lbs-in (0.41 kg/mm) from 4 to 7 inches. The overall length of the spring is about 15-1/2 inches (355mm). If this rate data is accurate, these are extremely light duty springs and I have to imagine that the vast majority of you are unhappy with the stock forks (even the 150 pound riders). Luckily, there are alternatives.

If you want to simply respring the forks with dual rate progressive springs of a higher rate I would suggest Progressive Suspension (brand) part number 11-1153. These springs have an initial rate of 35 lb/in and finish at 50 lb/in (0.63/0.89 kg/mm). They measure 30x445mm – so they are longer than the OEM springs by 3-1/2”. This extra length is off-set by cutting down the OEM spacer (or making a new spacer out of PVC). These springs will work well for riders between 160 to 220 pounds. I would suggest that you use 15w fork oil at an oil height (actually an air gap – measured with the forks compressed and springs out) of 120mm, and set the initial preload at 15mm (more on that later).

Regarding the spring rate of 35/50 lb/in; this is obviously a significant change from the 21/23 lb/in springs that Suzuki installed at the factory. I did do some benchmarking. First, my own LS650 uses a linear rate spring of 40 lb/in. However, do keep in mind that my Savage weighs 310 pounds vs 360 for a standard LS650, and I only weigh 170 pounds. I'm also using a cartridge emulator so I enjoy dynamic damping. Second, I also benchmarked some similar (but heavier) bikes. The VS800/S50, a bike that weighs 440 lbs and comes with a OEM spring of 26 lb/in, has a suggested spring rate from RachTech of 50 in/lbs with a 170 pound rider. Progressive suggests a 35/50 lb/in spring for this bike as well. RaceTech also recommends a 50lb/in spring for a VN750 (485 lb bike) with a 170 pound rider whereas Progressive suggests a 30/45 lb/in. Finally, unless heavily preloaded, I don’t think that you’ll use the top end of the 35/50 lb/in range. I say this because the available compressed length of about 220mm is longer than the 175mm of available travel of the OEM spring. I do think that this spring will work perfectly in the Savage forks.

Shocks
Much of the discussion of the forks applies to the shocks as well. The shocks define how comfortable the bike will ride – so it’s important to get them right. What makes one shock better then another? Like the forks, the primary function of the shock is to 1) support the sprung weight of the bike and rider and 2) provide damping to control the speed of movement throughout the stroke of the shaft. Without damping a spring will seek its static position as quickly as possible, overshooting its static position due to inertia. Also, just like the forks, a shock uses oil and air to create compression and rebound damping. As the shock moves it creates heat which is absorbed into the oil. When the oil gets hot it foams within the chamber and if the oil gets too hot it causes cavitation (slipping) within the chamber – impacting the ability of the shock to provide predictable (or meaningful) damping. The faster that heat can be absorbed and dissipated, the better the shock can perform its primary function of providing predictable damping. As a rule: the bigger the oil chamber the more effective the heat management of the shock.

The OEM shocks on the Savage are what are known as twin-tube shocks. Twin-tube shocks are the type most typically found on budget bikes. They are self-contained with an inner oil chamber and an outer air chamber (hence, the twin tubes). As a result of this design the inner oil chamber is very small. The damping rod (shaft) is connected to a piston that moves through the oil, creating damping. The vast majority of these shocks are typically low performance, non-rebuildable (meaning the valving can’t be adjusted), provide fixed damping and only adjustable for spring preload (usually just 5 positions for spring preload).

The OEM shocks on the Savage are under sprung and under dampened and are a significant limitation to comfort. If you’ve taken any of the above advice on your forks, then take this advice – throw your shocks in the garbage. Many Savage riders have had good success with Progressive Suspension’s 412 Series shocks. This is still a twin-tube shock, but they are slightly longer (1/2 to 1 inch) allowing for additional swingarm travel, have a dual rate spring that is more suited towards heavier riders, are nitrogen filled and “may” have better damping.

In order to select the correct part number of the 412 Series shock you will need to make a few decisions. First is your ride height. The OEM Savage shocks are 10-1/2 inches long and provide about 1-1/2 inch of travel. The 412 Series come in a number of lengths, but the closest to the OEM is an 11 inch unit offering 2” of travel and there is an 11-1/2 unit that has 2-1/2 inches of travel.  Next, you will need to select the spring rate(s). There are two available rates that will work well on the Savage, depending on your body weight. The is a 90/130 lb/in spring that will work for riders up to about 200-210 lbs and a 115/155 lb/in rate that will work for riders above that weight. Finally, there are both black and chrome versions of the shocks. Looking at Progressive’s spec sheet I’ve put together the following viable part numbers. There may be more, but these made the most sense. Before ordering call Progressive and talk to a tech support person.

11 Inch Eye-to-Eye
412-4005, 90/130 Spring Rates, comes in Black or Chrome
412-4232, 90/130 Spring Rates, comes in Chrome only
412-4233, 115/155 Spring Rates, comes in Chrome only

11-1/2 Inch Eye-to-Eye
412-4006, 90/130 Spring Rates, comes in Black or Chrome
412-4200, 90/130 Spring Rates, comes in Chrome only
412-4201, 115/155 Spring Rates, comes in Chrome only

For reference, I use an 80/100 lb/in spring on my bike. My bike is probably 40 pounds lighter on the rear axle than a stock Savage. The 90/130 should work nicely for the average sized rider.

I know that some have used the shocks from the VS800/S50. I would not recommend putting these shocks on your Savage. Yes, it does have heavier rate springs but it is exactly the same crappy damping used on the Savage.

The next step up from the 412 series shocks would be a gas pressurized emulsion shock. I’ve yet to find a bolt-on replacement gas pressurized shock with the correct specifications. The short size/stroke is typically found on small displacement (very light) bikes. As a result the spring rates are typically too low and the mounts are 10mm or 12mm (the Savage has 14mm mounts). If there is enough interest or demand we might see if CL Moto can rework 280mm (11”) RFY shocks for use on the Savage. This approach world require cutting springs and reworking the bushings for 14mm mounts – but they would be a tuneable/rebuildable bolt-on replacement with unlimited preload adjustment (versus the 5 click stops).

As you can probably tell from above, I’m not a big fan of multi-rate springs in forks. Used in the forks I find progressive springs too soft in the initial stroke and unpredictable in the remainder of the stroke. I believe that proper valving is the best route towards fork “progressivity”. However, multi-rate springs are necessary for our shocks. Here’s why.

Many modern motorcycles use a mono-shock arrangement. Mono shocks use a linear rate spring. The progressivity in the system comes from the multi-link connection between the shock and the swing arm. With this configuration, as the swingarm moves up there is less leverage between the shock and the swingarm, creating additional force with increased motion. Classic motorcycles like the Savage that use twin shocks have a direct connection between the upper shock mount and the swingarm, so there is a linear relationship between the motion of the swingarm and the compression of the shock. A multi-rate spring allows the shock to apply additional force on the swingarm as it moves up towards the bike.

What a well timed post.
That's really neat!

Wowza...very thorough, Gary. Good write-up!

Very informative post.  Did I miss it?  What was the cost of the recommended rear shocks substitute?  Shocks and Springs for about a 200 Lb. person?

Does Koni (now IKON) have any suitable shocks for this application?

Thanks for taking the time to write that up, Gary.

What are the length of those fork springs? Too long and they may require too much preload. To short and they can bind at full travel (or not allow full travel). But they might work nicely...just need the specs.

The YSS PD Fork Valve is a "import" copy of the Racetech unit. What is the valving and what is the valve spring rate? That will determine set up. I think if you go with the YSS unit you'll be on your own for set up. The GVE has been adapted to the S40 forks so there is known setup info.