(fits all versions of the Baja 5B & 5T)

Two months prior to the release of these rear A-arms for the HPI Baja 5B & 5T, we released our version of the front A-arms. In that short amount of time, the durability of our Baja A-arms displayed their unbeatable nature! That kind of performance can now be matched out back with our rear A-arms for the 5B & 5T.

RPM Baja rear A-arms start with the basic geometry of the stock arms so they are direct replacement parts – no additional parts will be needed. However, we’ve made a number of modifications  to the arms from there to improve performance and durability. Key durability features are as follows:

• The shock mount on the lower A-arm has been moved forward by a full ¼” to eliminate the severe rubbing issue of the wheel at the shock mount that would cause stock arms to break.

• By moving the shock mount forward, we were able to increase the material around the shock mount to protect the lower shock rod end, preventing it from being the lowest hanging component of the A-arm assembly.

• We’ve incorporated a third inner hinge pin boss at the inside hinge pin of the lower A-arm and tied in structural ribs that help disperse impact energy and rotational forces from engine torque over all three hinge pin bosses.

• Similar corner webs to those found on our front A-arms have been designed into the rear upper and lower A-arms as well to help improve strength and durability.

In the performance department, we moved the rear hub carrier forward by 1/8” over stock geometry. While this does little to change the overall wheelbase of the vehicle, what it does do is alter the angle of the drive shaft as it exits the differential. This reduces the tendency of the Baja to squat under acceleration. This happens when the torque of the motor is opposed by the force of friction created by traction at the rear tires causing chassis squat, consequently causing a loss of grip. By sliding the rear hub carrier forward, we use the torque of the motor to effectively “push” the rear wheels into the ground, using both the weight of the Baja and the torque of the motor to improve acceleration performance. Up top, RPM rear upper A-arms have had a shape change for added lateral stability – the stock “Y” shape tends to allow the upper pivot ball to move forward and backward while the RPM “D” shape holds the upper pivot ball in place more solidly, providing a more consistent feel to the performance of the Baja.

Just like our front arms, we mold our Baja 5B / 5T rear A-arms in both a stealthy black and a dyeable white version for those that like to personalize their vehicles. A little Rit clothing dye, some hot water and our dyeable A-arms can be dyed to any color you prefer!

Tech Notes: RPM Rear A-arms for the Baja 5B & 5T are sold in sets consisting of one upper and one lower A-arm. Two sets will be needed to complete one vehicle.

(fits all versions of the Baja 5B & 5T)
RPM front A-arms for the HPI Baja 5B & 5T are designed around the stock A-arm geometry, which means they are direct fit replacements – no additional parts or accessories are needed. The list of improvements from there is extensive! To start, we’ve eliminated most of the hard rib angles in favor of smoothly contoured curves that enhance survivability during extreme impacts. Both the upper and lower A-arms incorporate much larger and stronger corner webs than the stock A-arms while RPM lower A-arms have a redesigned center brace structure that helps the rigidity and strength considerably by spreading impact energies over a much larger area. RPM A-arms will hold their shape better and have less flex than the stock arms as well!

After extensive in-house review of 5B & 5T A-arms in stock form and listening to Baja owners, we found that the stock pivot ball socket tends to break out under certain impact conditions. We addressed this problem by adding nearly 15% more material around the diameter of the pivot ball socket and we redesigned the shape of the socket to add more support and improve crash survivability without creating any interference with suspension or steering movement. While we were redesigning the pivot ball area, we reduced the amount of slop in the ball socket to help improve and maintain more consistent camber and toe angles for smoother, more precise steering.

Another problem we encountered with the stock A-arms is the lack of protection for the very low-hanging front shocks. We’ve solved that problem in a couple of ways. First, we elongated the lower shock mount, leaving no part of the shock exposed. Next, we incorporated a unique lower A-arm skid plate that completely covers & protects the lower shock mount. This skid plate adds serious bulletproof RPM protection to the lower end of those extremely expensive shocks while adding strength and support to the whole lower A-arm. Additionally, these skid plates are reversible! Since the A-arm is angled up, only the lowest part of the skid plate (the rear area) will see the most wear. By making the skid plates reversible, the 5B / 5T owner can run the skid plates until they wear thin on the one end, swap them from one side to the other and they’re good to go for more punishment!

We have found that a large percentage of 5B & 5T owners like to personalize and customize their buggies. That is why we offer these new arms in stealthy black and fully dyeable white options. With a little Rit clothing dye and some creativity, our white A-arms can be dyed to any color imaginable! Please see our website FAQ page for more information on the dye process. 

Tech Notes: RPM A-arms are sold in sets consisting of one upper A-arm, one lower A-arm, one lower a-arm skid plate, two shock spacers and two skid plate mounting screws. Two kits will be needed to complete one vehicle. RPM Replacement Shock Skid Plates work with RPM Baja 5B / 5T front A-arms exclusively and are sold in pairs with necessary mounting hardware.