Project Blue Horn Rhino - HydroDynamics Shocks

“It’s Time to Smooth out the Rough Edges!”

Jul. 01, 2006 By Mike Martin

This is the chosen month…

The time has come to cast aside our stock shocks and unleash the potential hidden within our beast.   To accomplish this feat we call upon the experts at HydroDynamics USA to fully expose this UTV to one of their seriously ishocking products.


A fter almost a year driving on these stock Rhino shocks I have absolutely no doubt of their strengths as well as their limitations.   Not many of us out there are fond of a long rough ride, but then again nobody buys an off road vehicle to remain on the smooth and narrow all of the time either.   With that said, I’m here to offer a solution; the P51 shock by iShock.   The iShock P51 features an “anti-fade” non-reservoir design for easy installation and improved durability; below I have listed some additional features of the P51:

●Increased wheel travel (even with stock a-arms)

●100% Adjustable and tunable

●5/8” Hard chrome plated shaft

●100% Rebuildable

All backed by the Powersport Industries first 100% lifetime/satisfaction guaranteed warranty for a shock absorber (impressive).

Before we begin, let’s take a look at what’s included in the P51 package and then we’ll visually compare them to the Yamaha stocks.   Since these shocks are sold in pairs, the front and rear sets arrived tightly packed in their own boxes.   The rear set includes; 2-rear P51’s, installation instructions, 4-spacer bushings, 2-shock covers, and 2-spanner wrenches.   The front set includes; 2-Front P51’s, installation instructions and a set of spanner wrenches.


As you can see by the side by side comparison of the front shocks below (top of picture) the iShock P51 is several inches longer and is fully adjustable, when compared to the preset adjustment of the shorter stock silver shock.   As for the rear shock comparison; the two below are very close to the same length, but again the P51 maintains its full adjustability compared to the Yamaha stock.  

Installing the Product


If you have access to an ATV or Motorcycle jack it will make the install much smoother and safer.   After blocking the wheels and applying the brake, I lifted the hood and jacked up the front of the vehicle so that the front tires were approximately 3 inches off the ground. With the hood up I had plenty of light and access to both the upper and lower front shock bolts.   These bolts are tight, so be sure to have a wrench or socket on each side to break them loose.   When you install the shocks verify top and bottom with the visual mounting instructions so that the shocks are in the proper upright position.   Before installing the locknuts apply some form of thread locker to the bolt threads to insure they don’t loosen up in the future.


The rear shocks are basically the same install, except for the use of spacers (on some models).   The spacers are being utilized for the purpose of keeping the shock away from the axle. By lifting the dump bed before jacking up the vehicle you will get some well needed elbow room.

The rear shocks fit in just as effortlessly as the front shocks, making this complete install a breeze.  


P51 Adjustments


Now that we’ve got the P51’s on the vehicle, let’s take a look at some of the possible adjustments available on these shocks as well as a brief explanation of their terms.   First off, the pre-load on these shocks is pre-set at the factory for the stock Rhino configuration.   Pre-load is determined by the stiffness of the spring, spring tension is varied by either tightening or loosening the two adjustment nuts on the shock with the supplied spanner wrench.   Tightening the nut applies more pressure to the spring, which in turn increases the pre-load, while loosening the two nuts will remove tension from the spring, which will decrease the pre-load.   For those of you who have installed aftermarket products that add a significant amount of additional weight to your vehicle such as; rear seats, winches, or full cages will need to at the very least apply more pre-load to the springs to compensate for these accessories.   Even aftermarket wheels can affect the pre-load settings, wider than stock off-set wheels can also affect shock performance, to compensate for the increase in leverage, additional pre-load is required.   Tire size is also an important factor, iShock has developed the P51 to utilize all of the available travel with the stock tires, but if you are using some of those bigger than stock treads you’ll have to reduce the travel to keep them from rubbing the bed and bodywork.   To assist you in this travel reduction area HydroDynamics USA produces a set of red anodized billet aluminum travel reducers that are designed to be easily installed by any Rhino owner.

The next adjustment we will talk about is rebound.   Rebound is the speed at which the shock returns to its original position.   IShock has pre-set the rebound all the way out, or its fast setting. With this setting the P51’s will return to their original position very quickly.  

You may wish to slow the rebound; if that’s the case then it’s simply a matter of turning in the slotted adjustment screw clockwise.   The  rebound setting will be best determined by the individual rider depending on the chosen terrain.

Before we leave the subject of adjustments, I want to mention as part of iShocks 100% satisfaction guarantee; they will gladly swap springs and re-valve shocks as needed, free of charge to help the customer tailor his suspension settings to perform perfectly with his exact vehicle configuration.   HDUSA also has trained and certified technicians available via their toll free number 866-GO-ISHOCK or email them at


Putting the P51’s to Work

I have decided to stay with iShocks P51 factory settings on the Project Rhino since it has yet to be affected by any large accessories or aftermarket tire and wheel combinations.

Before I load up and head way out into the desert, I take the Rhino out to a nearby riding area to verify that everything is in proper working order.   As soon as I encounter rough terrain I can immediately feel the difference in the ride and handling of the vehicle.   The front end seems to travel over and down obstacles in a very smooth fashion, as the rear end fails to follow with the familiar jolting sound and feel of the bed landing hard.   I repeat the routine with a passenger on board to get their opinion, while remaining aware of any inconsistencies or changes in the ride.   Any changes that I did notice were positive for the P51’s, since the additional weight seemed to add to the betterment of the ride.   When I had completed my preliminary check I loaded up the Rhino and began planning for a full test near a Rocky River bottom.

I purposely chose several areas that I have traveled frequently in this Rhino so that I could openly compare the differences in this and past rides.   The entrance to the river area is deeply rutted and pitted with many sloped areas to choose from (what a perfect place for testing).   I climbed the 4x4 rutted inclines at various speeds to judge the differences in vehicle control, I then stopped and added a passenger and cargo in the bed of the Rhino to the simulate the extra weight of being loaded down for a long ride.   The extra travel in the front allowed the front wheels to reach out farther, keeping the fully extended side in touch with the ground, this allowed me to have more control and balance maneuvering through the ruts.

After repeating the slopes and hills many times, I made my way to the whoops (one of my least favorite areas).   These whoops are fairly tall and sharp, making this an area where the fast rebound setting should definitely come in handy.   As I motored through the ups and downs I felt support along with the ability to keep my foot glued to the pedal.   In the past I had always found it very difficult attempting to guide the machines jerky response through these seemingly endless mounds of rolling dirt, but now I find the vehicle leading its way through the terrain without my forcing the issue.   I was actually able to push the machine faster while thoroughly enjoying the ride!


Next I drove over to the river bottom where the river rock covers the bed with a light under pack of sand and dirt.   The ride itself is similar to a washboard road laden with larger rocks scattered haphazardly throughout the terrain.   My past riding experience in this area would not be considered smooth by any means, I would just prepare myself to ride out these rough areas and when I had a chance I’d cut over to the sand and ride there until the dense brush forced me to head back to the rocks.   That is until now; the P51’s performed perfectly in this jostling, jolting material, placing a smile on my face and allowing me to stay in the rocks, a feat that seemed impossible in my past trips with the stock shocks.   Stating the P51 provided a smoother ride is simple, but lets look into what goes on in this rocky section; the tires are not only rolling over the uneven rock formations, they are also moving and slipping on the surface rocks as they send them flying in all directions while still trying to push the vehicle forward.   In this case the shocks are dealing with a situation much different than a typical rock laden road where there is a hard pack underneath, they are dealing with ruts caused by the tires, larger rocks in the road, as well as uneven and washboard road surfaces along the way (whew).

Surrounding the end of a far off trail I began driving through some sharp drop offs and washed out areas climbing and descending so that I could get a feel of how well this product would perform under these conditions.   Every imaginable bump, rut, drop-off or rough section I could find I threw at the P51’s, and in the end I found their performance was nowhere short of impressive…not bad for performing in an ambient temperature that never dropped below 105˚ in the shade!   Temperature is always an important factor when testing a product, the hotter the temperature, the more stress the product has to endure to still function properly.

I would strongly recommend iShocks P51 for any Yamaha Rhino owner.   These shocks will handle any terrain that you can throw at them, and then some…So if you are looking for better control, better handling, and a much smoother ride look no further than iShocks P51.

Many thanks go out to the crew at iShock/Hydrodynamics USA for their contribution of time, product, knowledge, and support to this Rhino Project.

Please visit iShock/HydroDynamics USA for all your suspension needs at:

As always, ride hard, tread lightly, and travel often…

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