How rear struts work
A rear strut is an essential part of a vehicle’s suspension system. Often called a MacPherson strut, it’s similar to a shock absorber, but does more than simply act as a buffer between the vehicle’s wheels and body, protecting occupants from imperfections in the road surface.
A strut does all of that and also forms part of the geometry setup, ensuring the rear wheels are angled correctly for optimum handling and tyre wear.
It’s important to note that most cars have shock absorbers fitted at the rear, rather than struts, but there are exceptions such as the Subaru Legacy and older Honda Civic models. When you change rear struts you also need to have the alignment angles reset because they can govern the caster and camber angles.
Because of this extra feature you normally have to pay more for struts than for shock absorbers.
This task requires some experience. You will need a comprehensive tool kit and the job will take around an hour per wheel, depending on your model.
Every car is different, so before you view the full instructions, find yours…
When to change your rear struts
“A strut is responsible for the way a car rides and handles, and dictates how a tyre makes contact with the road surface”
A rear MacPherson strut should last for several years and tens of thousands of miles, but sometimes poor road surfaces, and especially potholes, can cause damage. Fortunately, the spring, gaiter, upper mounting and buffer can be replaced separately, although if the strut is more than a few years old Haynes recommends changing the entire strut. Always change struts in pairs.
A strut is made up of several key parts. From the top down they are: the strut upper mount, the cap, the piston rod nut, the upper mounting, the upper spring seat and rubber gaiter, the spring and the buffer. The piston rod is integral with the strut and can’t be replaced separately.
If it is time to change your strut, use our ‘before you begin’ checklist, and ‘find your car’ (both below) for specific instructions.
How to change your rear struts
Here is an example clip from a sample video.
A very brief summary of the task:
- Support the car on axle stands and remove the wheel
- Unclip the ABS speed sensor and free any hoses or wiring from the strut.
- Disconnect the lower control arm from the strut.
- Undo the strut upper mounting nuts/bolts, usually from within the boot, and lower the strut out through the wheel arch.
- Installation is the reverse of the removal process.
Why you should change your rear struts
Rear struts are a key part of a vehicle’s suspension system, and when they become worn they compromise driveability. You may be able to feel a shaking through the body, the tyres may have uneven wear (on the edges or in the middle) or the vehicle’s body control may be poor, especially when cornering.
Sometimes a strut will leak oil – you’ll see it covering the outside of the strut body. If this has happened to yours you’ll need to replace the entire unit.
First of all, make sure the strut is to blame. Second, identify which part of the strut has failed and whether it can be replaced separately, or if the entire strut has to be changed.
With the new strut installed, drive the vehicle to the nearest tyre fitter equipped with alignment equipment, so the steering geometry can be corrected.
Before you begin – tools you may need
Tools you will need
- A comprehensive toolkit will be required for this job.
- Floor jack (not your car’s emergency jack)
- Axle stands
- Wheel lug wrench
- Torx socket set
- Allen (hexagon) key set
- Ratchet and socket set
- Torque wrench
- Spring compressor tool (if changing the spring)
- Wide-opening grips
- Flat-bladed screwdriver
Parts that you may need
- Pair of new MacPherson struts
- New bolts
How much do new rear struts cost?
- Strut £50-£200
- Springs £25-£100
- Garage fee savings £100-£400