Did the rollers on one of these last week. Our third in the last two years. First unit other guys took a long time pulling the carriage out of the top, second two lifts we also cut access holes just small enough to remove the bolt that secures the roller in place. If you can fit safely beneath the lift (with blocking) to reach and change the bottom rollers, you can cut your holes low enough that they don't interfere with the lateral bumpers. Too high and those side play bumpers drag over your holes and fail. Our lower cuts on the last car were 18"AFF. Whole thing took 3.5 hours.