Spring Seats

A spring seat, also called a spring isolator or spring spacer, is located on the exterior of the shock absorber body or at the upper end of the piston rod. It positions and supports the suspension coil spring, normally in contact with the lower or the upper end of the spring inside the shock absorber assembly. It is made from NR, NBR, EPDM, PU, HDPE or TPE, with or without metal bonded to it, and it withstands the vertical load transmitted by the spring while limiting lateral displacement so that the spring cannot interfere with the surrounding components.

Because the seat sits inside a compressed spring, replacing it is a job where the preparation and the sequence matter more than the part itself. This guide sets out a safe and repeatable procedure from the point the complaint is confirmed to the point the vehicle is back on the ground and checked.

When the Seat Is the Part That Needs Replacing

Not every noise from a strut comes from the seat. Before the vehicle is lifted, separate the possibilities.

• A single knock or creak over bumps that repeats from the same corner points to a worn or collapsed seat, a separated bond, or the spring moving on its seat.
• Ride height lower on one corner suggests that the seat has taken a compression set or that a spring has sagged. Both should be checked.
• A spring that has rotated off its stop is usually the clearest evidence that the seat location feature has worn away.
• Continuous rattle over rough ground more often points to a top mount, a drop link or a worn suspension bushing than to the seat.

Where the strut has to come apart anyway, the seat, the bump stop, the dust cover and the top mount are usually inspected and renewed together, because the labour is already committed.

Safety Before the Strut Comes Apart

A compressed coil spring stores a large amount of energy, and more workshop injuries come from this job than from almost any other suspension task.

1. Use a matched pair of spring compressors rated for the spring, and fit them on opposite sides at the same height.
2. Tighten the two compressors in small alternating steps so the spring compresses evenly. Compressing one side alone can bend the spring and release it suddenly.
3. Keep fingers and the air line clear of the spring coils and never place any part of the body between the spring and the strut.
4. Stand to the side while working, and never use an impact wrench to run a compressor up against load.
5. Release the spring tension slowly and in the same alternating pattern after the assembly is rebuilt.

Tools and Consumables

Stripping the Strut

1. Record the ride height at each corner and, where available, the alignment readings before any work starts. These are the reference for the check afterwards.
2. Loosen the top mount nut and the wheel bolts with the vehicle on the ground, then raise and support the vehicle.
3. Remove the wheel and disconnect anything attached to the strut, such as the brake hose bracket, the wheel speed sensor loom and the drop link.
4. Support the hub or the lower arm so that the drive shaft and brake hose are not over extended.
5. Remove the lower mounting bolts and the top mount nuts, then lift the strut assembly out.
6. Mark the position of the spring end on the seat and the orientation of the upper mount before compressing the spring.
7. Compress the spring evenly with the matched pair, then release the top mount nut and dismantle the assembly.
8. Lay the parts out in order so that washers, spacers and the upper bearing race are refitted in the same sequence.

Inspecting the Parts While Apart

Fitting the New Seat

1. Compare the new seat with the old one before assembling. Check the diameter, the height, the location step, the mounting holes and the material.
2. Clean the spring end and remove any corrosion or old rubber residue from the contact area.
3. Confirm the orientation. Upper and lower seats are different, and a handed seat will only locate correctly one way round.
4. Seat the spring end against the location step so that the end cannot creep when the spring is loaded, and align it to the mark made before stripping.
5. Where a metal insert is bonded into the seat, keep the bond area clean and inspect it for separation before assembly.
6. Fit the new bump stop and dust cover in the same operation where they are being renewed, because they are only accessible with the spring off.
7. Compress the spring evenly again and rebuild the assembly in the reverse order of dismantling.

Reassembly and Torque

Where the workshop data specifies that the suspension must be at ride height before a bolt is finally tightened, support the hub at that position or lower the vehicle onto its wheels first. Tightening while the suspension hangs loads elastomer parts elsewhere in the assembly before the vehicle has moved.

Ride Height and Alignment Check

1. Lower the vehicle and settle the suspension by rolling it a short distance or bouncing each corner.
2. Measure ride height at the same reference points used before the work and compare, allowing for the specified tolerance.
3. Turn the steering from lock to lock and listen for spring noise, which indicates the spring end is not correctly located.
4. Drive over the surface that produced the original complaint and confirm the noise has gone.
5. Re check the alignment where the strut position has been disturbed, and re torque the wheel bolts after a short distance.

Common Fitting Errors

Frequently Asked Questions

Can a spring seat be replaced without removing the strut?

No. The seat sits inside the compressed spring, so the spring has to be compressed and the strut dismantled to reach it. This is why the parts around the seat, such as the bump stop, the dust cover and the top mount, are normally inspected and renewed at the same time rather than being left for a second strip down.

Is it safe to reuse the springs and change only the seats?

Yes, provided the springs themselves are within specification. Check the free length, the condition of the end coils and the corrosion on the wire. A spring that has sagged or lost an end coil will not give the correct ride height even with a new seat, and the two should be assessed together.

Should both sides be replaced at the same time?

Where both sides have covered similar mileage, replacing them together is the usual recommendation, because a new seat on one side and a compressed one on the other produces a measurable difference in ride height and load sharing. A single side replacement is reasonable where the failure was caused by local damage.

Why does the vehicle sit differently after the job?

The usual causes are a spring end that is not located against the stop, an upper and lower seat fitted the wrong way round, a seat that has not been driven fully onto its location, or a spring that was already sagging before the work. Measuring ride height at the same reference points before and after the job identifies which of these applies. Details of the parts concerned are on the spring seat page.

Parts and Technical Support

Bonpora Parts supplies spring seats, spring isolators and spring spacers in NR, NBR, EPDM, PU, HDPE and TPE, with or without a bonded metal insert, moulded to the diameter, height, spring end location and mounting hole positions shown on your drawing. Quality management to IATF 16949 controls dimensional tolerances, weld strength and coating adhesion, and a declared service life of no less than 80,000 km or two years is supported by a one to two year or 80,000 km warranty. Begin with the spring seat range, review the matching dust covers and shock absorber parts, or contact our team with your specification and annual volume. New dimensions are quoted from drawings or samples under custom moulded and bonded parts, the wider programme is described under chassis and suspension, and further references are listed on the products page.