If you're stuck trying to decide between our basic spacer lift or upgrading to our HD rear springs this post is for you! Over the years we received A LOT of requests to design and build a rear HD spring that would help combat the notorious rear sag often associated with carrying additional weight in the back of your Prius. Several years back we designed a spring that did exactly that, but the downside was that it rode like a Sherman Tank when the car was empty. After several renditions and still being unhappy with the unloaded ride characteristics we shifted focus to other projects and put the springs on the back burner. Simply put there is no way to have a spring handle EXCESSIVE additional cargo weight AND also provide a smooth ride unloaded. Think about a 3/4 ton pickup truck that rides rough and bumpy going down the road with nothing but a dozen eggs and a 36 pack of toilet paper in the back seat and yet when you throw 2,000 lbs of concrete in the bed it rides like a Cadillac. Over the years as time permitted we made significant improvements to the spring design and finally found the sweet spot for both an increased carrying capacity and improving the unloaded ride quality. Our springs were built with a target additional TONGUE weight of 200 lbs (ie 2 e-bikes plus a swing out bike carrier, or a loaded cargo box and carrier, etc.) Keep in mind that this number dramatically increases the further forward the weight is placed towards the front of the vehicle. 150 lbs of weight on a cargo carrier hanging 18" off the hitch, is comparable to 300 lbs in the back of the car, and 500 lbs in the back seat. The further forward in the vehicle the lighter the load gets, and the further back the heavier it gets. You should always try to place as much weight centered and low in the vehicle when loading it. Unloaded, these springs ride smoother than stock springs and lift spacers due to the custom coil and spring length which places the rear suspension in a more progressive position in the suspension cycle. Unloaded ride height tends to be just slightly higher than our 1.5" rear spacers and stock springs and provides approximately 1.75"-2" over stock height while unloaded (.25"-.50" more than stock springs + rear spacers). If you don't ever plan on carrying any additional weight in your car the stock springs and spacers work just fine, however there really is no disadvantage to using the HD rear springs unloaded and it really opens up a lot of possibilities for carrying additional weight in the future. Take note how much your Prius sags next time you have 4 people inside with a couple suit cases in back. So if you're looking for the best riding and most versatile setup, and cost isn't a factor, we suggest going with the HD rear lift springs. Also keep in mind that HD rear lift springs are used IN PLACE of rear lift spacers NOT in addition to rear lift spacers. So when you open your package and see that no rear spacers are included with the HD rear spring kit try to fight the urge in thinking you are missing half your order. The HD lift springs have LIFT built into them already. ;)
