Smart Roadster wheel bearing replacement involves pressing out the old bearing from the hub carrier and pressing in a new sealed unit. Front bearings are 72mm OD, rear 75mm OD. The job requires a hydraulic press or specialist puller kit and typically takes 2–3 hours per corner at a workshop.
Wheel bearings are one of those components that attract little attention until they fail — and on a car as small and taut as the Smart Roadster 452, a failing bearing makes its presence very clear indeed. The low-slung bodywork and minimal sound deadening mean noise travels directly to the cabin, and the car’s tight suspension geometry means a worn bearing affects handling earlier than it would on a larger vehicle. Whether you are investigating an unfamiliar hum or planning preventative maintenance, this guide covers everything you need: how to identify the faulty corner, what to buy, and what the replacement process actually involves.
How to Diagnose a Smart Roadster Wheel Bearing Fault
The classic symptom is a low, cyclic humming or droning noise that changes with road speed rather than engine speed. The key diagnostic clue is that the noise often changes pitch or intensity when you gently weave the car left and right at 40–60 mph — loading and unloading the bearing. If the drone quietens when you steer right, the suspect bearing is on the right side, and vice versa. This works because lateral cornering loads shift weight off the worn bearing momentarily.
Secondary symptoms include:
- A grinding or growling sensation felt through the floor or steering wheel at low speed
- Vibration through the seat at motorway speeds that does not correlate with tyre imbalance
- Slight steering pull toward the affected side under braking
- In severe cases, a clunking or knocking on full lock, sometimes mistaken for a CV joint fault
To confirm the suspect corner, jack the car safely on axle stands, grab the wheel at 12 and 6 o’clock and attempt to rock it. Any detectable play indicates a worn bearing. Then spin the wheel by hand and feel or listen for roughness. A healthy bearing spins smoothly and quietly. Note that the Smart Roadster’s ABS reluctor ring is integrated into the bearing on most units, so a failing bearing can also trigger ABS or ESP warning lights — if you are chasing C1xxx ESP fault codes and cannot find an obvious cause, inspect the wheel bearings before condemning a sensor.
Smart Roadster Wheel Bearing Specifications
The Smart Roadster 452 uses conventional pressed-in ball-race bearings rather than bolt-on hub units, which makes replacement slightly more involved than on many modern cars but keeps the part cost low.
Front Bearing Specifications
- Type: Single-row deep-groove ball bearing, sealed
- OD: 72 mm
- ID: 35 mm
- Width: 17 mm
- Common cross-reference: SKF 6007-2RS, FAG 6007-2RSR
Rear Bearing Specifications
- Type: Single-row deep-groove ball bearing, sealed
- OD: 75 mm
- ID: 40 mm
- Width: 16 mm
- Common cross-reference: SKF 6208-2RS, FAG 6208-2RSR
Always buy from a reputable bearing manufacturer such as SKF, FAG, or NSK. Cheap pattern bearings may last less than 10,000 miles. The cost difference between a budget bearing and an OEM-quality unit is rarely more than £20 — money well spent when a press is required to change it again.
Tools and Parts Required for Smart Roadster Wheel Bearing Replacement
Because the bearing is pressed into the hub carrier rather than bolted in, you cannot complete this job with hand tools alone. The minimum equipment list is:
- Hydraulic press (preferred) or a quality bearing puller/press kit with stepped adaptors
- Torque wrench (hub nut torque: 130 Nm front, 110 Nm rear)
- Socket set including 30 mm or 32 mm for the hub nut
- Circlip pliers (front hub carrier has a retaining circlip)
- Penetrating fluid — hub components on older cars are often heavily corroded
- Copper anti-seize grease for reassembly
- New hub nut (single-use stretch nut on both axles — never reuse)
- Replacement bearing (specify front or rear)
If you do not own a press, most independent garages will press bearings for a modest bench fee even if you supply the bearing yourself. Given that the Smart Roadster sits low and the subframe geometry is tight, many experienced DIYers choose to remove the hub carrier completely and take it to a press rather than fight the job on the floor.
Step-by-Step: Smart Roadster Wheel Bearing Replacement
The procedure below covers the front corner, which is marginally more involved owing to the circlip. Rear replacement follows the same principle without the circlip step.
1. Remove the Wheel and Hub Nut
Loosen the hub nut while the car is on the ground and the wheel is still fitted. Apply penetrating fluid generously. Jack the car, remove the wheel, then fully remove the hub nut. Discard it — a new one must be fitted on reassembly.
2. Disconnect Brake and Suspension Components
Remove the brake caliper and hang it with wire — do not let it hang on the hose. Remove the brake disc. Disconnect the anti-roll bar drop link, lower ball joint, and track rod end from the hub carrier. Mark the position of any adjustable components before removal to preserve your alignment geometry. This is also an ideal moment to inspect the steering rack condition; our detailed walkthrough of how the steering rack is removed and replaced covers the adjacent components you will encounter here.
3. Remove the Hub Carrier
With all ancillaries disconnected, the hub carrier can be removed from the car. Keep it clean and clamp it securely before pressing.
4. Press Out the Old Bearing
Remove the circlip (front only) using circlip pliers. Support the hub carrier on the press bed with the appropriate stepped adaptor and press out the old bearing. The driveshaft spline hole goes through the bearing centre, so ensure your adaptor clears it. A rusted-in bearing may require significant force — work steadily and do not apply heat near the hub carrier itself.
5. Clean and Inspect
Thoroughly clean the bearing bore with a wire brush and inspect for ovality or scoring. Light corrosion can be cleaned up; a deeply scored bore will cause the new bearing to fail prematurely. Check the driveshaft and CV boot condition while everything is apart.
6. Press In the New Bearing
Press the new bearing squarely into the bore, applying pressure only to the outer race. Never press on the inner race or through the bearing body — this destroys the bearing immediately. Press until fully seated, refit the circlip (front), and verify the bearing spins smoothly by hand.
7. Reassemble and Torque
Reinstall the hub carrier, reconnect all suspension and brake components, and fit a new hub nut. Torque to specification. Refit the wheel, lower the car, and re-torque the hub nut with the wheel on the ground. A 4-wheel alignment check is strongly recommended after this work to verify that reinstating the ball joint and track rod end has not shifted the geometry.
How Long Do Smart Roadster Wheel Bearings Last?
On a well-maintained car used on reasonable roads, original bearings can last the life of the vehicle — several owners report original bearings beyond 100,000 miles. However, the Smart Roadster’s low ground clearance means it is disproportionately exposed to deep water and kerb strikes, both of which accelerate bearing wear. Repeated immersion washes out the grease and admits corrosion; a single significant pothole impact can crack the race internally, beginning a wear process that manifests as noise months later.
Cars used on track days are at notably higher risk. Sustained high lateral loads push the bearing well beyond its road-use design envelope. If you use your Roadster for any circuit driving, inspect the bearings annually rather than waiting for symptoms.
It is worth noting that wheel bearing condition interacts with wider chassis health. A car that pulls or vibrates after a fresh bearing can have an unrelated fault — the Softouch gearbox, for example, can introduce drivetrain vibration that mimics bearing noise. If you have replaced a bearing and vibration persists, our guide to diagnosing RPM sensor faults in the transmission may help rule out a gearbox-side cause.
Cost of Smart Roadster Wheel Bearing Replacement
Part cost for a quality bearing is typically £15–£35 per corner. Workshop labour varies considerably but expect £80–£150 per corner at an independent garage familiar with the car, more at a main dealer. The job is not a routine service item, so it pays to use a specialist who knows the model and has the correct press adaptors to hand.
If you are having a suspension corner stripped anyway — for example, to replace a worn ball joint or to address a steering rack issue — combining the bearing replacement at the same time saves significant labour cost since the hub carrier must come off regardless.
Electrical faults can sometimes accompany a bearing replacement if the integrated ABS reluctor is damaged. Always clear any stored codes after the job is complete and verify ABS function on a quiet road. Unexplained B1xxx codes unrelated to the bearing should be investigated separately — our complete breakdown of SAM unit fault codes and their fixes is a useful reference for any electrical gremlins that surface during a suspension strip.
Frequently Asked Questions
Can I drive a Smart Roadster with a worn wheel bearing?
A mildly noisy bearing may be driveable for a short period, but it is not advisable. A failing bearing generates heat and can seize or shed its race without further warning, potentially causing loss of wheel control. If the bearing has detectable play or the noise is severe, the car should not be driven until it is replaced.
Do Smart Roadster wheel bearings come with the ABS ring included?
Most quality replacement bearings for the Smart Roadster 452 include an integrated ABS reluctor ring. Confirm this when ordering, as a bearing without the ring will trigger ABS and ESP faults immediately. SKF and FAG units for this application typically include it as standard.
Can I replace a Smart Roadster wheel bearing without a press?
Not reliably. The bearing is an interference fit in the hub carrier. A slide-hammer puller and stepped-adaptor press kit can substitute for a bench press in the field, but improvised methods risk damaging the bearing bore or the new bearing itself. Hiring a press or using a garage’s facilities is strongly recommended.
Will a worn wheel bearing affect my Smart Roadster’s wheel alignment?
The bearing itself does not set alignment, but dismantling the hub carrier to replace it disturbs the track rod end and ball joint settings. Any smart roadster wheel bearing replacement should be followed by a 4-wheel alignment check to ensure toe and camber remain within Smart’s specified tolerances, preventing uneven tyre wear.
