Suspension

With the cheapest and most common cause, which is the anti roll bar links. They are small ball jointed rods taking constant reversing loads, and they wear quickly, producing a light metallic knock over ripples and manhole covers at low speed that vanishes on smooth roads. After that, control arm bushes produce a heavier knock over larger bumps with wandering steering, and top mounts produce a knock at the front that is accompanied by a creak on turning. All three are inexpensive.

Dampers, yes, across the axle. Two units of different condition on the same axle give the car different responses on its left and right sides, and the moment that matters is a swerve or a hard stop on a bumpy road. Springs are a little more forgiving but follow the same logic, since a sagged spring on one side leaves the car sitting low and loads the anti roll bar permanently. Front and rear are independent decisions. There is no obligation to change all four corners unless all four have done the same mileage and show it.

Think of the rubber as a spring in torsion rather than a plain bearing. It is bonded to the inner sleeve and to the outer shell, so when the arm swings the rubber winds up instead of sliding. Clamp that bolt while the wheel hangs free and you have set the neutral position at full droop, which means the rubber is permanently wound in one direction whenever the car rests on its wheels. It tears itself apart in a season. Load the suspension on ramps or with a jack under the hub before final tightening.

Load and unload each side with the steering. A failing bearing produces a rumble that rises and falls with road speed rather than engine speed, and weight transfer changes it: on an empty road, a long gentle curve to the left puts more load on the right hand wheels, so a right hand bearing gets louder there and quieter on the opposite curve. Confirm off the road by lifting each wheel and rocking it at twelve and six o'clock while feeling the hub. Eliminate the tyres first, since a worn tread pattern roars in a very similar way.

After anything that disturbs an arm, a knuckle, a subframe or a tie rod, yes, because those components define camber, caster and toe, and bolts through slotted or eccentric mountings will not return to exactly the same position. Dampers alone on a rear axle usually do not change geometry, and front struts do, since camber is set at the strut on many designs. When in doubt, book the rig visit. It costs far less than a set of tyres.

Generally, yes, and the bushes and top mounts usually show it first. A battery pack adds a large mass carried low in the body. The springs sit under more preload, the dampers work in a higher load range and every rubber joint deflects further over each bump. Instant motor torque also twists the arms and their bushes each time you pull away. Parts for these vehicles are rated for that load, so fitting a lighter design from another model is a false economy. Read the OE number on the old part and enter it exactly in the search box.

Not always. A light mist of oil around the rod seal is common and usually harmless, because the seal is designed to leave a thin film on the rod. If the body is coated in wet, dirty oil or it drips onto the spring seat, the seal has failed and the unit is losing the fluid that does the damping. Confirm it on the road. A failed damper lets the body float after a crest, dive under braking and skip over broken tarmac. If you see both signs, read the OE number on the old unit and search for it.

Easily. Springs usually snap at the bottom coil. Water and salt sit in the spring seat there and corrode the coating until a pothole finishes the job. The broken end often stays trapped in its seat, so the car feels almost normal on a smooth road. The clues are one corner sitting slightly low, a clonk over speed humps or a creak at full lock. Shine a torch along the lowest coil to look for a clean break. A loose end can cut into the tyre, so stop driving and read the OE number on the old spring before ordering.

It depends on how the arm is built. On many arms the bushes are bonded and the ball joint is riveted or pressed in and not serviced separately, so the complete arm is the only proper repair. Where the bush can be serviced, fitting a new one needs a press or a dedicated tool, and the arm must be sound with a tight ball joint. If the ball joint has play, a torn boot or corrosion, fit the complete arm. Search the OE number from the old arm. If you only need the bush, ask through the quote form and we reply within 24 hours, usually sooner.

Both designs exist. Many modern vehicles use a sealed hub unit that bolts to the knuckle in one piece, with the bearing, flange and wheel speed encoder built in. Other designs press a bearing into the knuckle and then press a separate hub into the bearing. That needs a press and the correct drifts, because pushing on the wrong race ruins a new bearing instantly. On press fit types the magnetic encoder side must face the wheel speed sensor, or the ABS light comes on. The OE number on the old hub or bearing tells you which design your vehicle uses.

Often not. Many hub nuts have a collar that is staked into a groove in the driveshaft, and that deformed collar is what stops the nut loosening. Once the nut has been undone, it cannot lock the same way again. Some arm and knuckle bolts are tightened to a torque plus an angle, which stretches them slightly and makes them single use. A reused fastener can work loose or leave the bearing with end play, which also disturbs the wheel speed signal. Check the fitting instructions for your model and have a qualified mechanic do the final tightening.

Usually, yes. The top mount carries the full load of that corner through a rubber isolator. On the front it also contains a bearing that lets the strut turn with the steering. It has done the same mileage as the old strut, and replacing it later means compressing the spring and stripping the corner a second time. While the corner is apart, check the bump stop and the dust boot as well. A split boot lets grit score the new rod, and a crumbled bump stop lets the strut bottom out. Read the OE number on the old mount and search for it alongside the strut.

Mostly after corrosion or an impact. The subframe is a steel cradle that carries the arms, the steering rack and often a drive unit, and it bolts to the body through large rubber mounts. Worn mounts cause a clunk when you accelerate or brake and a vague feel in corners, and they can be replaced on their own. The frame itself needs replacing when rust has thinned the metal near a mounting point, or when a kerb strike has bent it so the alignment cannot be brought back into range. Have a qualified mechanic measure it, then match the OE number on the old frame.

If only one corner drops, the leak is almost always at that corner. The usual causes are a perished rubber bellows on the air spring or a loose line fitting. If the whole car drops evenly, suspect the valve block, or a compressor that can no longer keep up. With the suspension raised, spray soapy water over the bellows, fittings and lines and watch for bubbles. Deal with it early, because a compressor that runs constantly to make up for a leak overheats and fails as well. Take the OE number from the old air spring or strut before ordering.

Many arms, knuckles, hubs and struts are handed. The left and right versions are mirror images and carry different OE numbers. Sides are named as seen from the driving seat facing forwards, so in the UK the left is the nearside, next to the kerb. A part fitted to the wrong side may still bolt up, but it puts the caster angle, the caliper mounting or the sensor in the wrong place. The OE number on the old part already tells you the side. If the part changed during production, the build date on the identification plate decides which version fits.