Preload, ride height and damping are all easier to set on a bench than under a car. Twenty minutes of prep per corner saves you crawling under the chassis twice — here's the full procedure.
Difficulty
1h 10m – 1h 45mBench time · logged
5 stepsProcedure
Area 03Chassis & Susp.
Most coilover horror stories start the same way: the units go straight from the box onto the car, then every adjustment afterwards happens on your back, in the dark, with the spring fighting you. The fix is boring and effective — do everything adjustable on the bench first, fit the unit once, and the only under-car job left is torquing.
This guide covers conventional thread-body coilovers with separate spring seats (BC, MCA, Fortune Auto style). Inverted monotubes and air setups have their own quirks — different guide.
⚠ Before you start
A compressed coil spring stores enough energy to put you in hospital. None of the steps below require a spring compressor — that's deliberate. If a step ever seems to need one on this style of coilover, stop: you've likely wound a collar the wrong way. Back up and re-read rather than reaching for compressors.
01
Unbox, match, inspect
Logged: ~10 min for the set
Lay all four units out and match them to corners — fronts and rears differ, and on some kits left and right do too (check for bracket orientation and sway-bar tab position). Confirm spring rates against the invoice: kits do occasionally ship with mismatched springs, and finding that now costs nothing.
Check threads for shipping damage — run each locking collar through its full travel by hand.
Confirm top-hat orientation matches your chassis (pillow-ball vs rubber mount).
Photograph each unit's as-shipped collar positions before touching anything.
✓Done whenAll four units are corner-matched, threads run clean, and you have a photo record of factory settings.
02
Set spring preload
Logged: ~15 min per pair
Preload is the spring-seat setting, and it's the one most often set wrong because people confuse it with ride height. On a separate-spring-seat design: wind the lower spring seat up until the spring just stops rattling at full droop — zero preload — then add whatever your kit's manual specifies (commonly 0–5 mm for street rates).
Do this with the unit upright in a soft-jaw vice, damper fully extended. You should be able to just barely rotate the spring by hand at zero preload; if it spins freely there's slack, if it won't budge you've already compressed it.
Photo · spring seat at zero preload, vernier on exposed thread
Fig. 01 — Measure exposed thread below the seat and write it on tape on the body. Future-you will need it.
Workshop tip
Set preload identically left-to-right by measuring exposed thread length, not by counting collar turns — thread starts can differ between units, and "six turns" on one body isn't "six turns" on another.
✓Done whenBoth units in a pair show identical exposed-thread measurements at the spring seat, recorded on the body in tape.
03
Set initial ride height
Logged: ~20 min per pair
Ride height on this style of coilover comes from the lower mount position, not the spring seat — that's the whole point of the separate adjustment. Wind the lower bracket to replicate your old strut's installed length as a starting point: measure the old unit centre-of-mount to centre-of-mount and match it, minus whatever drop you're targeting.
A sane starting drop is 20–25 mm under stock for a street car. You will fine-tune on the ground later regardless — the bench setting just needs to be close enough that the first drive isn't on the bump stops.
✓Done whenEach unit's mount-to-mount length matches its old counterpart minus target drop, and both sides of an axle are within 1 mm of each other.
04
Set damping baseline
Logged: ~5 min for the set
Click adjusters are far easier to reach on the bench than installed (rear adjusters especially can end up behind trim). Wind each adjuster gently to full stiff, counting nothing yet, then back to full soft counting total clicks — that's your verified range. Then set the kit's recommended street baseline, counted from full stiff, which is the convention almost every manufacturer uses.
✓Done whenAll four adjusters are verified through their full range and set to baseline, with the click count written on the body tape.
05
Lock collars, stage for install
Logged: ~10 min for the set
Tighten every locking collar against its setting using the kit's C-spanners — hand-tight plus a firm bump, not gorilla torque (aluminium collars gall easily). Then stage each unit at its corner with its hardware. From here, installation is purely mechanical: the unit goes in once and nothing on it needs adjusting under the car.
FastenerSpecStage
Top-hat nuts (M8)25 NmOn install
Knuckle bolts (M12)95 NmAt ride height
Lower mount lock collarHand + bumpOn bench
Damper top nut55 NmOn bench
// example specs for an S13 chassis — always confirm against your kit & FSM.
✓Done whenAll collars locked, top nuts torqued, each unit staged at its corner. Bench work complete — the car only gets touched once.
Where this saves you
The payoff shows up in the install log
On our last set, bench prep took 1h 25m and the actual fitting took 40 minutes a corner — with zero under-car adjustment afterwards. Compare that against the day a seized bolt blew the schedule apart in Coilovers in, knuckles out: a 9-hour Saturday. Prep is the part of the job you control.