How to Properly Set Up Coilovers (Your Coilovers Aren't Set Up Right)

*Last updated: 21 January 2026

PREFACE

There’s a big mix of information out online on how to set up coilovers but there's nothing that directly addresses considerations like bump & droop travel, needing to be at street legal height and going even lower than the coilovers will allow out the box. This guide addresses all of the above.

INTRODUCTION

So you’ve bought and installed a set of two piece coilovers. You expected better and thought you should feel like you're on top of the world yet somehow your fully sick coilovers ride like absolute rubbish. Maybe you do feel like you're on top of the world and you simply don't know better.

Are you going ejecto seato instead of gliding over big bumps? Are you experiencing hopping or sudden snap oversteer when cornering hard? Is your car constantly bouncing? Chances are you haven’t set up your coilovers properly and you're hitting bump stops. This article goes through how to get the most out of your el cheapo coilovers (yes this includes whatever fancy expensive name brand you have as long as it's in two pieces).

GLOSSARY

• Two piece coilovers: Coilovers with a threaded shock body and lower cup
• Spring perches: The locking collars right under the spring
• Stroke: Total shock travel from end to end
• Bump travel: How much the shock can compress from static height. Complementary to droop travel
• Droop travel: How much the shock can extend from static height. Complementary to bump travel
• Bottoming out: Compressing the shock until it has no more bump travel
• Motion ratio: Ratio of how much the shock travels compared to the wheel. On a double wishbone suspension equipped car, the coilover attaches to a spot along the control arm and not to the wheel itself. Because of this, for every 1mm of movement at the wheel, the shock travels less than 1mm. On an NB MX5, movement of 1mm at the wheel is 0.68mm (0.66mm for NA) at the front shock and 0.77mm at the rear shock.
• ‘Preload’: An unhelpful myth. Preload is based on the idea that the spring is pre-compressed and exerting an initial force that needs to be overcome (this state only occurs when the wheel has lifted off the ground). The idea is that the static weight of the car must offset this force before the shock can start compressing. This is unhelpful because: 1. it focuses on weight rather than length measurements which makes it useless for adjustments, and 2. it has no influence on the performance of linear springs once the car is on the ground.
• Resetting the car: Lift the whole car up on a hoist and rest it back on the floor, then roll it a good distance back and forth. If you don’t have access to a hoist then gently roll the car back and forth a few times. Do not press down over each corner, you will dent the panels, ask me how I know. This is to remove any stiction in the suspension components.
• Take note: record/note a measurement

TESTING CLEARANCES AND SETTING UP A MINIMUM HEIGHT

1. Do everything on smooth, level ground

2. Disconnect front and rear sway bars so that the shocks can move freely

3. Disassemble a coilover and reinstall it with the spring removed

4. Check clearance and find minimum height

• Install your wheel and jack up the control arm until either the shock bottoms out or the wheel contacts something on the car. At the front, turn the wheel to observe any interference
• Two piece coilovers: Adjust the shock body length by threading the shock into or out of the lower cup so that the shock bottoms out right before the wheel contacts anything. Trim the bump stop or install extended top hats to reduce wheel gap if necessary.
• One piece coilovers: Add bump stop shims or trim the bump stop so that the shock bottoms out right before the wheel contacts anything.

• *** Take note: this is your absolute minimum functional shock body / bump stop length ***

5. Match the setup across the axle

• Remove the coilover and reinstall it with the spring. Set the spring perches so that the spring is barely seated i.e., ‘zero preload’
• Measure and adjust the other coilover across each axle to match

6. Torque all nuts and bolts with the car resting on the ground

7. Repeat Steps 3 to 6 at the other end of the car

ADJUSTING HEIGHT

Now for the fun part!

1. Ensure tyre pressures are equal at all 4 corners

2. Raise the ride height

• Raise the car by raising the spring perches. This way, you retain all the travel set by following the steps above and raise the car by pushing the piston higher up out of the shock body. See notes below re: preload being a myth. Tip: knowing your motion ratios is helpful to estimate changes in ride height after adjustment.
• Depending on what coilovers you have, you might get to a point where you can no longer raise the perches to achieve your desired ride height. If this happens, raise the car by unwinding the shock from the lower cup. Do not exceed the minimum found above if subsequently lowering by the cup after raising it.

3. Lower the ride height

• Lower the car by lowering the spring perches.
• DO NOT lower the car by the lower cup. Lowering by the lower cup beyond the set minimum height means the wheel will contact the car before the shock bottoms out, resulting in damage and wasted travel. You'll have the same amount of bump travel until the car bottoms out, but instead of bottoming out the shock, the wheel hits the chassis. The bump stroke left over after the wheel hits the chassis is completely unusable. It could have been used for droop travel by lowering the spring perch instead.
• If the spring becomes unseated, consider installing helper springs to keep the spring seated at all times. Repeat this step after installing helper springs. Otherwise, leave it as is if it's acceptable to you.

Note: Adjusting the spring perch affects how much bump and droop travel you have. See the notes below on bump and droop travel.

4. Check ride height

• Reset the car (see glossary) and observe ride height
• If you are measuring your ride height, use a tape measure from the ground to the front and rear pinch welds to find chassis height. Avoid measuring wheel to fender as this is less accurate and is not as informative for chassis rake.
• Repeat steps 2-4 until you achieve your desired ride height

ALIGN WHEELS AND FINE TUNE

1. Reconnect sway bars and get a wheel alignment

Your wheel alignment is affected by adjustments to suspension components. Even 1mm of ride height change will affect your alignment. Get a wheel alignment to minimise undue wear to your tyres.

2. Fine tuning

• By attaching a small cable tie around the shock piston under the bump stop, you can find out if you've hit bottomed out by seeing if the cable tie has buried itself into the bump stop. If this happens, consider:
• Increasing the spring rate (consider replacing all four corners to maintain handling balance); or 
• Adding bump travel by raising the spring perch.
• If the shock tops out, add droop travel by lowering the perch. If you have to choose between bottoming out or topping out, choose topping out. 
• Get another wheel alignment

ADDITIONAL NOTES AND EXPLANATIONS

How much bump and droop travel should you have?

A general rule of thumb is that 2/3 bump and 1/3 droop is a good place to start; i.e., target droop = 1/3 * stroke, and target bump = 2/3 * stroke. This can't be helped with one piece coilovers where you'll either have your desired ride height or a set amount of bump/droop travel but not both at the same time (unless coincidentally they are the same). While two piece coilovers have independent adjustment, they might still not provide adequate travel in either direction.

The truth is, it doesn't matter how much bump and droop travel you have as long as you're not bottoming out or topping out. The shock behaves the same in each direction whether you have 20mm, 30mm or 40mm of bump or droop travel.

Explanation of why spring perches are used for height adjustment and why 'preload' is a myth:

At static height, the shock is somewhere between the limits of its travel. Imagine a shock that has 100mm of stroke, has a 10kg/mm linear spring installed, and 500kg of force/weight on the corner resulting in 50mm of spring compression. The shock therefore has 50mm of bump travel and 50mm of droop travel.

Raising the spring perch by 5mm extends the overall shock length by moving the shaft 5mm out from the body. The weight/force on the shock remains 500kg and so the spring stays compressed by 50mm but the shock now has 55mm of bump travel and 45mm of droop travel. As the spring perch is raised: the shock is extended, bump travel is gained, droop travel is lost, and spring compression remains unchanged.

At full droop, the shock has no more room to extend via the piston and so the 5mm upward adjustment on the spring perches results in 5mm of spring compression. Importantly, while 'preload' and weight/force on the shock push the piston in opposite directions, they move the spring in the same direction. At full droop, there is an equivalent of 50kg of upward force on the shock. With 500kg on the corner: the first 50kg of force offsets the 'preload'; the remaining 450kg of force compresses the spring by an additional 45mm to a total of 50mm, and pushes the piston 45mm downwards. Once again, the shock has 55mm of shock travel and 45mm of droop travel. Hopefully this explains why 'preload' has no bearing on coilover performance as long as the wheels stay on the ground.