The sound of your expensive tires grinding away at the body produces the same sensation as your third-grade teacher running her fingernails down the chalkboard. Some of us have learned to block out the grinding and go about our mayhem. Others would rather limit wheel travel to stay out of trouble. Perhaps the most commonly thrown-away and overlooked lift-kit parts are the bumpstop extensions. Oh sure, you believe you need them if youre really bashing your Jeep like a 15-year old in moms Volvo, but for normal trail use and rockcrawling you dont need bumpstops. You couldnt be more wrong. The extensions that came with your lift kit arent always perfect for your application so they may allow the tires to rub or they may even be too tall for the tires you are using. So weve put together some info on how and where bumpstops should be located so you can fine tune your suspension and possibly avoid some expensive repairs.
The Problems
There are three reasons to run properly located bumpstops: clearance, impact absorption, and spring fatigue. The first, clearance, is simple enough. If you dont have bumpstops, something will probably make contact or bottom out. This can lead to bent driveshafts, damaged shocks and shock mounts, tweaked steering linkages, broken transfer cases, and more.
Impact absorption is what the bumpstop does. It slows the bottoming force with a chunk of flexible rubber, or in the case of the Rancho bumpstops were using for this story, urethane.
Spring fatigue, better known as sagging, happens when a spring is bent past what it was designed for. If springs are compressed too much they may lose some of their arc. This most commonly occurs when a spring is bent into a negative arc.