Spacer Lift vs Preload Spacer vs Coilover Preload
The good, the bad, the ugly
January 24, 2023
When it comes to lifting your IFS truck or SUV, there are quite a few options to choose from. Depending on your goals or budget, an affordable spacer lift may be too good of a deal to pass up. Although appealing in price, there can be some serious drawbacks to performance that you may not be aware of. Below we will review these drawbacks and give you a better visual on what is happening when the suspension is in motion. We will show what a top hat spacer lift does and what a preload spacer does while the suspension is cycling and compare it to an aftermarket adjustable coilover. These visuals should help explain how everything works and what to expect if you choose one of these options for your truck or SUV. Enjoy!
Animation #1 | Spacer Lift
[left] Shock Failure due to spacer lift and incorrect bump stop height. [right] Spacer lift causing UCA to hit coilover at full droop
What is a spacer lift? A typical coilover spacer lift includes some type of spacer/block that goes in between the top of the coilover and the shock mounting point on the frame. In general, it lowers the coilover position by what ever height the spacer is to lift the vehicle. The spacer height is not equal to the amount of lift the vehicle will get. Independent front suspension will have the coilover shocks mounted to the lower control arm with a motion ratio. Example: Let’s say the motion ratio is 0.5. So height changes to the coilover (at ride height), it will be double that at the wheel. So 1″ of height change at the shock will change the ride height 2″. Spacer lift blocks are offered in a variety of sizes and material choice.
-Good: Spacer lift kits are very affordable compared to replacement aftermarket shocks. Spacers are simple to install and bolt on with basic hand tools. For those looking to level their truck and don’t plan to off-road much, this is a popular option.
-Bad: Spacer lifts are the cheapest lift kit option out there and they follow the golden rule of “you get what you pay for”. These spacers are not a performance upgrade since they do nothing to the shocks other than lower the mounting position on the frame. Most of the time these spacers are used with stock shocks so there will be not much of a difference in ride quality. Spacer lifts are mainly designed for street driven vehicles wanting their vehicle to look better. Lift spacers are not adjustable and usually come with the same height left to right. Not only do spacers not provide any performance gain, they can actually create serious issues. [view animation #1] When the coilover is lowered down with the spacer, it changes quite a few things. Issue #1, Stock bump stop is now too short for the new compressed length. The shocks now bottom out before the bump stops engage which can cause the shock to break. Issue #2, At full droop, the coilover extends too far and the upper control arm can hit the coilover shock and spring. #3 With excessive suspension droop at the wheel, the upper control arm ball joint is now fully maxed out beyond what it was intended for, which can cause premature wear or failure. There are a few other issues with steering joints and cv axles that can arise from this, so its best to avoid spacer lifts all together.
*Not to be confused with a coil spring preload spacer lift
Animation #2 | Preload Spacer Lift
PRELOAD SPACER LIFT
A preload spacer lift kit includes some type of spacer that goes in between the top of the coil spring and the top of the coilover assembly. [See animation #2] These are generally installed on stock coilovers. Preload spacers do not change the mounting points of the shock, and do not change the compressed or extended length of the shock. Preload spacers are usually installed on vehicles with added weight to maintain stock height or add small amount of lift. Similar to the top hat spacer lift, the preload spacer height will not equal the amount of lift you will get on the vehicle, same motion ratio will apply. As the name says, these spacers are adding preload to the coil spring to gain the lift height.
-Good: Preload spacer lift kits are cheap compared to replacement aftermarket shocks. They can help gain ride height back after adding weight to the vehicle. They do not require aftermarket upper control arms and do not change the mounting location on the vehicle.
-Bad: Depending on the setup, preload spacers can force the shock to be too extended at ride height. This will reduce down travel at ride height and potentially have you topping out the shock more frequently. Some vehicles come stock with internal bypass shocks, which are ride height sensitive. These shocks are designed to be in a specific zone during normal driving conditions and get firmer during max compression or extension. Adding a preload spacer to these can put the shock closer to the top out zone which in turn can affect ride quality. Preload spacers are difficult to install since it requires a spring compressor to remove the spring from the shock. More than basic tools will be needed for this process. Since most of the time a stock spring is still being used, there is still no performance gain. Preload spacers can be a temporary fix for a setup that really needs a heavier spring rate. There is also risk of the stock spring going into coil bind with too much added preload.
*Not to be confused with a top hat spacer lift
Animation #3 | Adjustable Preload Lift
COILOVER PRELOAD ADJUSTMENT
Aftermarket coilover shocks are a complete replacement option. There is a huge variety of coilover shock options on the market that range in size and performance. Most aftermarket coilovers from companies like Fox and King will be adjustable, which means the shock will have a threaded body with a preload nut to allow for ride height adjustments. Aftermarket coilovers are usually installed for added lift height and performance gain. Manufacturers design their shocks to work around factory suspension geometry and require minimal upgrades to go along with them.
GOOD: Aftermarket coilovers are generally pretty simple to install. They are similar to replacing a factory coilover with basic tools. Adjustable aftermarket coilover shocks are great for making small changes on each side to compensate for uneven weight on a vehicle. These coilovers are usually serviceable, tunable and are capable of having different springs swapped for extra weight. Various spring rate options and ride height adjustability is a huge performance gain compared to stock or any type of spacer lift. Some aftermarket coilovers will also provide more shock travel, which will allow for a lift and better performance off-road. Manufactures have designed these coilovers to not exceed the limitations the stock geometry can withstand, however an aftermarket upper control arm is usually required with a longer coilover to help with alignment and wheel travel.
BAD: Aftermarket coilovers can be an expensive upgrade (buy once, cry once). Adjusting preload can be difficult without the right tools. Most longer travel shocks will require an aftermarket upper control arm.