Polaris RZR Trail 900 ball joints fail at the snap ring, not the joint itself. That thin clip is the only thing holding a factory joint in the A-arm, and tight technical trail work is exactly the duty cycle that finds it. Keller ball joints remove it entirely — the two-piece housing threads into the arm like a nut and bolt. Hardened 4340 chromoly, greaseable, adjustable and rebuildable.
Todd Keller's original threaded design, covering the 50-inch RZR Trail 900 from 2021 onward. On this machine the same joint serves both positions, so you simply choose how many you need.
Key Features
- Two-piece threaded housing eliminates the OEM snap ring
- 4340 hardened chromoly steel housings and studs
- Adjustable and greaseable for correct stud articulation over years of service
- Rebuildable — a worn joint is serviced, not replaced
- One joint fits both upper and lower positions on this platform
- Limited lifetime warranty against manufacturing defects
- Made in USA
Built To Solve: RZR Trail 900 Ball Joint Pull-Out and Snap Ring Failure
- Snap ring shearing and letting the joint separate from the A-arm
- Clunking or knocking from the front end over roots, rock ledges and ruts
- Play in the wheel when rocked top-to-bottom on a jack
- Repeat OEM joint failures on a machine that spends its life at full steering lock
- Torn boots admitting water and grit so the joint wears from the inside
- Replacing the same joint often enough that it has become routine maintenance
Best For: Tight-Trail and Wooded-Terrain RZR Trail 900 Riders
- RZR Trail 900 owners riding narrow, rocky or rooted trail systems
- Riders who spend most of the day at or near full lock rather than at speed
- Owners who have already replaced an OEM joint and do not want to do it again
- Machines running larger or more aggressive tires than stock
- Anyone who wants a serviceable joint rather than another disposable one
If the joints are sound but the boots are torn, the Keller boot replacement kit is the cheaper fix.
Specifications
- Material: 4340 hardened chromoly steel, stud and housing
- Design: two-piece threaded housing, no snap ring
- Serviceability: adjustable, greaseable and rebuildable
- A-arm modification: not required
- Positions: one joint serves both upper and lower on this platform
- Warranty: limited lifetime against manufacturing defects, original purchaser
- Manufacturer Part Number: BJK-P-RG#AM (one joint), BJK-P-RG-K-2#AM (two joints)
Fitment
- Polaris RZR Trail 900: 2021 onward
This is the 50-inch Trail 900 specifically. The wider Trail S 900 and Trail S 1000 take their own Keller listings, so check which car you have before ordering. Fitment is not guaranteed on applications not listed above.
FAQ
Why do RZR Trail 900 ball joints pull out of the A-arm?
The factory joint is retained by a snap ring seated in a groove. Side load at full steering lock, rock strikes and the extra leverage of bigger tires can deform or shear that ring, and once it goes the joint has nothing holding it. Keller joints thread into the A-arm instead, so there is no clip to fail.
Is this the same part as the Trail S 900 or Trail S 1000?
The physical joint is shared across much of the platform, but each car has its own SuperATV listing and part number. Order from this page for the 50-inch Trail 900 and from the matching page for a Trail S.
Do I need different joints for the upper and lower positions?
No. On the Trail 900 the same Keller joint serves both positions, which is why this product is sold by quantity rather than by upper and lower.
How many do I need for a full front end?
Four — two per side. SuperATV lists this car in single and two-joint quantities, so a complete front end is two of the two-joint option.
Do Keller ball joints require A-arm modification?
Standard Keller joints do not — they thread into the factory arm as supplied. The Mega version uses an oversized housing and does require machined A-arms, which is the main reason to pick one over the other.
Can these be rebuilt instead of replaced?
Yes. They grease and adjust, and the Keller ball joint rebuild kit for Polaris services them with a new cup, boot and pin when the internals eventually wear.
Why Keller
Todd Keller designed the two-piece threaded ball joint to fix the one part of a stock front end that keeps failing, and SuperATV now builds and backs the line. The design has barely changed because it does not need to: thread the housing in like a nut and bolt, use a chromoly stud, and make the whole assembly serviceable so a worn joint gets rebuilt rather than binned.
Complete Your RZR Trail 900 Front End Rebuild
Before ordering, confirm you have the 50-inch Trail 900 rather than a Trail S, then decide whether you are replacing a single failure or doing all four corners. If the boots are torn but the joints are sound, the Keller boot replacement kit is the cheaper fix. If the joints are worn but the housings are good, the Keller rebuild kit for Polaris services them. Tie rods and A-arm bushings are worth inspecting while everything is apart.
Installation Video
Official SuperATV installation walkthrough with Todd Keller: How To Install Keller Ball Joints
