SHOCK TECH: SHOCK THERAPY SPRINGS AND LIMIT STRAPS

SHOCK THERAPY SPRINGS AND LIMIT STRAPS

Polaris RZR XP Pro Ultimate suspension upgrades By Ray Gibbs and the staff of Dirt Wheels

When you order your spring kit, you are required to fill out a questionnaire about your car and typical driving setup. Your spring kit comes with specific setup information. For the rear shocks on my Pro XP, the preload adjuster was to be set at 3.5 inches from the end of the threaded portion of the shock body. After putting some miles on the car, the springs will take a “set,” and the preload may need to be readjusted.

SHOCK TECH: 

The 2020 Polaris XP Pro Ultimate is an impressive machine right off the showroom floor, but it is not perfect. I grade any off-road machine in four categories: power, braking, suspension and comfort. The powerplant delivers a thrilling experience, and the CVT clutch system is tuned to modulate and transmit the power to the ground effectively with excellent drive-belt durability. Power gets an A+.

The brakes are powerful, with balanced control and a great pedal feel. Even when abused, they do not fade and remain consistent in operation, so they earn an A-.

The cockpit is well thought out and comfortable, with adjustable features that accommodate a wide range of pilots. The seats are comfy for long hours in the car, and the tilt and telescoping wheel puts the controls in the optimum driving position. Comfort earns another A+.

This is the same rear shock with a tape measure showing the location of the crossover collar. It was to be set at 11.75 inches from the end of the shock threads. The crossover bridge starts the primary spring compressing before the tender spring is bottomed out.

SHOCK TECH: 

The Dynamix electronic suspension is next level, but the spring quality and rate choices are flawed. If the driver is over 150 pounds, and if the car has the typical accessories, the rear tender springs will sag. In my RZR, I usually have a passenger in the cab (since she let me buy the car), a spare tire and rack, tools, a cooler and the rest of the gear that is over the rear of the car. You could crank down the preload adjusters enough to get the required ride height, but then you are left with non-working tender springs (coil bind) because of the excessive preload. 

This overly soft spring rate causes the rear suspension to ride deep in the travel, and it bottoms too easily. You can make up for it somewhat with the Dynamix settings, but it isn’t optimum.

I had the opportunity to try a Band-Aid fix by substituting a pair of 8-inch (unloaded length), 350-inch-pound springs in place of the OEM rear tender units. This was a big improvement over the stock setup, but I still had to be very mindful of the suspension settings and had the thumb at the ready on the red panic button.

This is a comparison between the silver Shock Therapy front springs and the OEM red Polaris front springs. It can be hard to see the difference in the spring rate. It depends on the wire thickness, length of the spring wire before it was coiled, and the quality of the raw material. Plus, in our case, the rear was where most of the spring change needed to happen.
This is what the installed Shock Therapy front springs look like compared to a shock with stock front springs. Again, a spring compressor was essential to the job.
Shock Therapy supplies all of the critical measurements needed for a personalized setup. A web video shows you what to do. The preload and crossover measurements for the front Shock Therapy spring shocks are 2.25 and 5.0 inches.

THE SOLUTION

After some research, I felt that the Shock Therapy dual-rate spring kit would be my best solution. It claims to convert both the front and rear suspension over to a true dual-rate system. These kits use a threaded adjustable collar that controls the motion of the upper (tender) springs.

This is the front limit strap kit from Shock Therapy. Initial setup is done with the shocks removed from the car. Measurements (from Shock Therapy for the RZR XP Pro) have you install the strap on the upper mount loosely, and then adjust the threaded rod until the strap is 1.5 inches shorter than the extended shock. This is in anticipation of the new strap stretching until it is 0.25 inches shorter than the shock. It becomes taut right before the shock top’s out.

SHOCK TECH: 

For me, one of the worst sounds in off-roading is the horrible clunk when the front shocks hit their mechanical stops at full extension. Over time, this can damage the shocks. Shock Therapy didn’t invent limiting straps, and they aren’t the only company that sell them. I haven’t heard that sound on my RZR, but I don’t want to. I liked the design of the Shock Therapy straps, so I decided to add them while I was changing the springs. Every component in this kit is a quality part, and the materials and workmanship are top-notch. The top mount is a robust two-piece clamp and is easily adjustable, which (in my opinion) is much better than having to deal with buckles.

The limit strap clamp gets positioned as far up on the threaded shock body as possible. It should be just below, but not touching, the reservoir bridge.
The eyelet of the clamp gets set in line with the shock bolt hole. The four Allen-head screws get torqued to 22 pound-feet.

SHOCK TECH: 

When driving with the straps installed on the car, you won’t even notice that they are there. When adjusted properly, the straps do an excellent job of stopping the extension at just the right moment. This is done smoothly and silently, so you don’t even notice them, which is exactly what you want. These straps, by nature of their design, will stretch a bit. Further adjustment will be necessary.

Position the strap adjuster nuts on the bolt loosely. There is a measurement before the final tightening.
Here are the rear springs for comparison—Shock Therapy in silver and OEM Polaris in red. There is a huge difference in lengths. Most of the difference is in the tender springs. As you can imagine, this could not be done without the spring compressor.

The following are the steps I took while installing the springs and limit straps. Note that a spring compressor is not shown but is required for the job.

This is the installed front shock with the Shock Therapy springs and the limiter strap. It is a clean installation, and it looks ready to rock.
This is the rear shock installation with the much-longer-than-stock Shock Therapy springs. The shock looks smaller in diameter but longer. Both are optical illusions.
The limit strap will be set at 1.5 inches from hole to hole. Then, tighten the adjusting bolt nuts. The strap will stretch after initial use. The ideal measurement is that the strap should be 0.25 inches shorter than the shock, so it will stop the shock at full extension.

THE RESULTS

The final step is to check the ride height after installing the shocks. The instructions state to check this with all the accessories and driver and passenger in place. After my initial test ride with the new springs, I found that my setup needed a bit more preload to get the car to the prescribed ride height.

Once dialed in, the new ride is a huge improvement over the OEM springs. I found that the car no longer had any trace of hitting the ground on landings, whoops or G-outs. With the new spring system installed, the computer-controlled Dynamix suspension system comes into a new dimension.

Instead of having to constantly toggle up and down between the settings (Comfort, Sport and Firm), I found that I can leave the settings in Comfort in most conditions where I was previously in Sport. Aggressive driving in Sport results in a new level of connection and confidence with the car. I’m able to leave the computer settings in Comfort for most conditions and save the Sport setting for aggressive driving. The Firm setting is rarely used.

SHOCK TECH: 

With the Shock Therapy spring kit installed, I have found a new level of confidence while driving the car. In my opinion, the 2020 Pro XP is a very good platform for an off-road vehicle. The Shock Therapy springs take it from very good to awesome! These springs not only fixed the low ride height and bottoming, but add a new level of plushness to the ride.

The red (firm) panic button on the steering wheel is still used for the really big stuff. I have not had the car bottom out, and the ride in Comfort setting is truly Cadillac-like.

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