ST XTA Coilovers BMW Z4 E85/E86 03-09

ST XTA Coilovers for BMW Z4 E85/E86 (2003-2009) – 15-50 mm Lower, Height & Rebound Adjustable, Camber Top Mounts

This ST XTA kit replaces the standard springs and dampers on the BMW Z4 E85/E86 (2003-2009) with a height-adjustable coilover set. It lowers the car by approx. 20-50 mm at the front and 15-40 mm at the rear, which sharpens the steering, cuts body roll and closes up the wheel arch gap. The ride height is set on threaded struts, so you can go for a subtle drop or use the full approved range, and change it again later.

The ST XTA is ST's fast road and track day coilover. As well as stepless height adjustment and 16-click rebound damping, it comes with Unibal (spherical bearing) top mounts on the front axle, so you can adjust front camber after the coilovers are fitted to get more of the tyre on the road in corners and sharper turn-in. It uses a race spring system: a linear main spring for consistent, predictable behaviour, supported where needed by a helper spring that keeps the main spring seated at full droop. ST is part of the KW automotive group, and the kit is developed and made in Germany using KW engineering.

This kit is for the BMW Z4 E85/E86 (Roadster, Coupe) with the 2.0 i, 2.2 i, 2.5 i, 2.5 si, 3.0 i, 3.0 si, up to a 790 kg front axle load. Check the Fitment section below before ordering.

Specifications

• Front lowering: approx. 20-50 mm
• Rear lowering: approx. 15-40 mm
• Max front axle load: up to 790 kg
• Max rear axle load: up to 890 kg
• Height adjustment: Stepless, on threaded strut housings
• Minimum ride height (wheel hub centre to arch edge): front 320 mm, rear 330 mm
• Damping: Adjustable rebound, 16 clicks
• Springs: Linear main springs with helper springs where needed
• Top mounts: Front Unibal mounts with camber adjustment
• Strut housings: Galvanised steel
• Approval: Parts certificate (German §19.3)

Lowering figures are ST's, measured against the standard car. The actual drop varies with engine, equipment and tolerances on each car, and the springs settle slightly after the first few hundred miles.

Key Features

• Front Unibal top mounts with camber adjustment after fitting
• 16-click adjustable rebound damping, delivered with a base setting for this vehicle
• Stepless ride height adjustment on a coarse, dirt-resistant trapezoidal thread
• Race spring system with linear main springs for consistent, predictable handling
• Galvanised, multi-sealed steel strut housings for long-term corrosion protection
• Composite spring perches with stainless steel inserts that stay easy to adjust for years
• Dust covers and bump stops protect the damper seals
• Developed and built in Germany, based on KW engineering
• Supplied with a parts certificate and fitting instructions

What's in the Kit?

• 2 x height-adjustable front coilover struts with springs
• 2 x rear dampers
• 2 x rear springs with height-adjustable spring seats
• 2 x front Unibal top mounts with camber adjustment
• Composite spring perches with stainless steel inserts
• Dust covers and bump stops
• Parts certificate and fitting instructions

Please note: the photos are ST's own images of this kit. Small details such as brackets can differ from the photos.

Fitment

• BMW Z4 Coupe E86 (Mar 2006 to Dec 2009)
• BMW Z4 Roadster E85 (Sep 2002 to Dec 2009)
• Engines: 2.0 i, 2.2 i, 2.5 i, 2.5 si, 3.0 i, 3.0 si

Not suitable for: any vehicle not listed above. Contact us with your registration if you are unsure.

Installation

Fitting means removing the original struts, springs and dampers and fitting the ST units in their place. We recommend a qualified workshop experienced with coilovers. The Unibal top mounts replace the original front top mounts. Set the ride height within the approved range, tighten the suspension bolts with the car's weight on its wheels, and torque everything to the manufacturer's figures. A four-wheel alignment is required once the car is at its final ride height. Re-check the height and alignment after the first few hundred miles, once the springs have settled.

Download ST's documents for this kit: Fitting instructions (PDF), Parts certificate (PDF), Damper adjustment guide (PDF).

Set the front camber on the Unibal top mounts before the alignment, and start with the rebound adjusters on ST's base setting.

Before you start:

• With the factory wheels and tyres, wheel spacers may be needed to give enough clearance to the coilovers.
• On the original wheel sizes, wheel spacers may be needed to keep enough clearance.
• Disconnect any ride height sensors (headlight levelling or self-levelling) before removing the old struts.
• Clean the threads before adjusting, and start with the height adjusters in the middle of their range.

After fitting:

• Do not go below ST's minimum height, measured from the wheel hub centre to the wheel arch edge: front 320 mm, rear 330 mm.
• Expect the car to settle a further 5-10 mm once it has been driven, then re-check the height.
• Check there is at least 5 mm clearance between the tyres and the suspension through the full steering and suspension travel.
• Have the headlight aim reset, along with any other height-dependent systems.
• ESP/ABS warning lights can appear after fitting. Some clear after a short drive, others need full steering lock both ways or a reset with a diagnostic tool.
• On cars with radar or camera driver assistance systems, have the calibration checked after lowering.

Upgrade Further

If you only need height adjustment, the ST X Coilovers BMW Z4 E85/E86 03-09 has fixed damping and costs less.

If you don't need camber adjustment, the ST XA Coilovers BMW Z4 E85/E86 03-09 offers height and rebound adjustment.

Will this fit my BMW Z4 E85/E86?

It fits the BMW Z4 E85/E86 (2003-2009) with the 2.0 i, 2.2 i, 2.5 i, 2.5 si, 3.0 i, 3.0 si. Check the Fitment section for the body styles and exclusions, or send us your registration and we will check.

How low will my BMW Z4 E85/E86 sit?

ST quotes a drop of approx. 20-50 mm at the front and 15-40 mm at the rear compared with standard. The exact drop varies from car to car with engine, equipment and tolerances. ST also sets a minimum: the distance from the wheel hub centre to the wheel arch edge must stay above approx. 320 mm at the front and 330 mm at the rear.

Can I adjust the damping?

Yes. The rebound adjuster has 16 clicks and the kit arrives on ST's base setting for this car. Turn towards firm for tighter body control or towards soft for a more comfortable ride.

Will the ST XTA make my BMW Z4 E85/E86 ride harshly?

The XTA is the sportiest ST kit, with linear race springs, so it is noticeably firmer than standard. The 16-click rebound adjuster lets you take some of the edge off for road use, but it is aimed at fast road and track day cars.

Do I need an alignment after fitting?

Yes. Changing the ride height changes camber and toe, so a full four-wheel alignment is needed once the car is at its final height, and again after any later change. With the XTA you can also set front camber on the top mounts.

Will my standard wheels fit?

On the original wheel sizes, ST says wheel spacers may be needed to keep enough clearance. Aftermarket wheels should be checked for clearance at your chosen ride height.

Is it road legal in the UK?

Yes. It is designed for road use and comes with a German parts certificate. Keep the ride height within ST's approved range and tell your insurer about the modification.

What is the difference between ST and KW coilovers?

ST is part of the KW group and its coilovers are made in Germany using KW engineering. ST uses galvanised steel strut housings and offers fewer adjustment options than KW's stainless steel Variant range, which keeps the price lower.

Is it covered by a warranty?

Yes, ST covers it against defects in materials and workmanship. If a part ever needs replacing, contact us with your vehicle details and order number.