When you lift an XJ, the axle can travel farther up before anything stops it — bump stop spacers put that limit back where it belongs so your tires don't chew the fenders and your shocks and springs don't get crushed at full compression.
Lift a Cherokee and you gain ride height, but you also open up extra up-travel that the factory bump stops were never sized for. At full compression — a hard whoop, a big ditch, landing off a ledge — the axle now travels closer to the body than stock, and nothing catches it until the tire is buried in the fender or the shock is topped out internally. Bump stop spacers (also called extensions) shim the stop back down to meet the axle at the right point. They're one of the cheapest parts in a lift and one of the most skipped, and skipping them is how people end up with sliced tires, torn fender seams, blown shocks, and cracked leaf packs.
The rule of thumb: extend roughly 1 inch of bump stop for every 1 inch of lift beyond the first 2 inches. A 2" budget boost usually gets by on stock stops. At 3" and up — especially with 31s, 32s, or 33s — you need to add extension, and the exact amount depends on your tire size and how much rub you're willing to live with. This isn't a guess-and-go part; you measure it on your own rig.
Steps
Get the XJ on level ground, then safely lift and support the frame with jack stands so the suspension hangs at full droop. You need the wheels off the ground and the axle free to move for measuring.
Locate the stops. The front bump stops sit inside the top of each coil, tucked into the coil bucket on the unibody. The rear stops are rubber cones mounted to the frame rail directly above each axle tube.
Find your up-travel limit. Remove the coil or lower the axle on the jack, then cycle the axle upward by hand or with the jack until the tire kisses the point in the fender where you want it to stop. Bigger tires need to stop sooner.
Measure the gap. With the tire at that stopping point, measure the distance between the rubber bump stop and its landing pad (the strike plate on the axle). Add about 1/2" to that number to account for the rubber compressing under load — that's the extension height you need.
Choose your method. Bolt-on poly pucks (Daystar) thread onto the factory stud and are the fast route. Stackable spacer kits (JKS) let you dial exact height with interlocking pucks. Adjustable weld/bolt plates (Zone, DPG) give the most precision. For a DIY front fix, stacked rubber hockey pucks inside the coil are a proven budget move.
Install the front extension. Drop the coil, set the extension on the factory bump stop stud or stack pucks in the coil, and reinstall the coil. Torque the lower control arm and shock hardware to spec if you disturbed them (LCA bolts 55–75 ft-lb, shock lower nut ~17 ft-lb).
Install the rear extension. Bolt or clamp the extension to the frame-side stop, or add a spacer to the strike pad on the axle. Keep both sides equal height so the axle lands square.
Cycle and check clearance. Lower the Jeep, then flex it — a driveway ramp, a curb, or an off-camber pull into the yard. Watch for tire-to-fender contact and confirm the stops make contact before the tire does. Re-measure and add height if the tire still rubs at full stuff.
Why it works
Cheapest insurance against sliced tires and torn fender seams on a lifted XJ
Protects shocks from bottoming internally and leaf packs from over-compression
Tunable to your exact tire size and lift height
Bolt-on options install in a driveway afternoon with hand tools
Trade-offs
Trades away some up-travel, so a stop set too tall stiffens the ride and cuts articulation
Getting the height right takes measuring and often a second pass after test-flexing
Precision adjustable and weld-on kits cost more and can need drilling or welding
Overshooting is a real risk — more spacer than you need only makes the truck ride harsher
Tools required
floor jack and jack stands
metric sockets and wrenches
tape measure
flashlight
torque wrench
drill or grinder (for some weld-on/bolt-on kits)
Parts
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Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.