The number one selling vehicle in our country is the pickup truck. The number one modified vehicle in our country is also, probably, the pickup truck. One common modification that I regularly see is the what is referred to as a suspension lift.
You have all seen a lifted truck. At the extreme it is the truck parked beside you at the stoplight that you can see right under, unimpeded. In many cases a lifted truck is much less obvious.
One of the recent most common lifts is called a levelling kit. If you look closely at a new truck you will see that the vehicle looks sloped from front to back. The rear is higher than the front. A truck is meant to carry heavy junk and the truck is engineered to have the vehicle sit level when the box is carrying an average load.
Most of the trucks on the road are more often used as cars than trucks. It has become a style thing to raise the front suspension so that the truck looks level without any load. This is a levelled truck. Once level the owner may decide that he/she would like the vehicle to sit a bit higher off the ground. The levelled truck is then raised up by inches to satisfy the owner’s desires.
Lift kits are sold and referred to by the number of inches they lift the vehicle up above the basic height. Many a lift kit is sold for bragging rights. Your friend gets a 4 inch lift kit. You need a 6 inch lift kit. And so on. Your friend needs a power drop down step to get up into his truck. You need a ladder.
In general most lifted trucks serve no real purpose other than style. They do often include bigger tires. These big tires increase ground clearance which may be welcomed off roading.
A lot of engineering went into your truck's suspension. The engineer had some ride and handling criteria that he/she wanted to reach. There was also concern for how long the parts involved were going to last.
There are well engineered lift kits and there are poorly engineered lift kits. No matter what lift kit you install or have installed you are making some compromises. The life of many components will be compromised.
Lifting your truck raises the centre of gravity (Increases the tipiness). Inexpensive lift kits will change the angle at which all your suspension and drive components sit. The engineer that designed your truck wanted your drive axles and suspension arms to sit as close to level when your truck was carrying an average load. Horizontal arms keep the tires flat on the road when the suspension moves up and down during normal driving. Horizontal axles apply power evenly.
Poorly designed lift kits change the normal location of suspension arms and drive axles. The resultant average location now places the parts under higher stress and changes the geometry of how the tires maintain contact with the road. The vehicle will handle differently and wear out parts more quickly.
Better engineered lift kits will contain many more parts. Arms will be moved or replaced with different arms. The engineered lift will maintain level steering and suspension parts along with more horizontal drive axles. Roll stiffness will be increased to ward off tippiness. As you can imagine these kits will require substantially more investment by the owner.