With Timbrens, at some time the gap will go to zero. Maybe a partial load, maybe very bumpy road, maybe a combination, but it will happen. Then as the suspension transitions from stock to Timbren aided and back, the ride characteristics will change. And it might happen on just a single rear wheel at a time and multiple times in a trip. I did not like that unsettling feeling on dry roads and it seemed likely to be dangerous on wet or icy roads. They are basically a softer set of bump stops with less suspension travel. Ditched them in favor of air bags.