Second-hand braking system: how to safely choose discs, calipers and ABS?
The importance of safety in a car cannot be compromised. One of the most important systems affecting our safety is the braking system . Replacing components such as brake discs, calipers, or an ABS module with used ones can be intimidating – but with proper verification and adherence to purchasing procedures, used car parts can provide not only savings but also full functionality. Here's a comprehensive checklist on how to safely choose used braking components from a store like Global Parts.
Why consider used brake parts?
Second-hand car parts, especially used brake parts —discs, calipers, and ABS pumps—offered by trusted suppliers can be original, functional, and attractively priced. This allows buyers to save money without sacrificing OEM quality. Global Parts, as an automotive store, offers parts for premium brands like BMW, Mercedes, Audi, VW, and Mini. For popular models like the BMW E90, F30, E87, and X3 F25/E83, the store offers a wide selection of front and rear brake discs and calipers. With a proper checklist, you can safely opt for used parts.
Checklist for checking the wear and quality of used brake parts
Checking approvals and quality certificates
When purchasing brake discs, even used ones, make sure they have European ECE R90-02 approval. This standard guarantees that replacement parts meet stringent quality and safety requirements comparable to original factory-fitted components. At Global Parts, you can find discs that meet these standards, which is especially important for models like BMW E90 front brake discs or BMW F30 brake discs .
Disc wear control
- Disc Thickness: The minimum operating thickness is specified by the manufacturer. Using a micrometer, measure the disc at several points (minimum 8) to assess thickness variation and wear. The difference between the thickest and thinnest points should not exceed the allowable values.
- Lateral Runout: Measuring disc runout (deviation from flatness) is crucial because excessive runout can cause vibration and uneven brake pad wear. This measurement is performed using a dial gauge.
- Surface condition: Discs should be free of cracks, deep scratches, and corrosion. Even used discs, such as BMW E87 brake discs or BMW X3 F25 brake discs, must be in good cosmetic condition.
Matching to model and year
The discs used must be compatible with the vehicle model and year. For example, BMW E90 brake discs are different from BMW F20 discs. The Global Parts store offers parts specifically for the BMW E87, BMW F30, BMW X3 E83, and Audi A3 8P (both front and rear), among others.
Checking pad and caliper compatibility
Disc selection should consider compatibility with brake pads and calipers. Poorly selected components can lead to accelerated wear and reduced braking efficiency. Used calipers should also be thoroughly inspected for leaks and the condition of the pistons and guides.
Brake caliper inspection and selection
Brake calipers are a component that directly impacts braking power and safety. When purchasing used calipers, be sure to:
- Check the condition of the pistons and seals – leaks can lead to brake fluid leakage and pressure loss.
- Make sure that the terminals are not corroded or mechanically damaged.
- Verify that the calipers are compatible with the specific car model and discs, e.g. calipers for BMW E90 or BMW X3 F25 .
- In the case of terminals integrated with ABS modules, check their electrical operation and the absence of controller errors.
ABS module – what to look for when buying a used one?
The ABS module is an electronic component that controls the braking system, preventing the wheels from locking during braking. When purchasing a used ABS module:
- Check that the module comes from a vehicle without any damage to the ABS system and that it is compatible with our car model.
- Verify the condition of the electronics and the absence of diagnostic errors.
FAQ – questions from drivers and mechanics
| Question | Answer |
|---|---|
| Can I buy second hand BMW E90 discs? | Yes, provided they are > min. thick, free of wear and cracks. Please check the manufacturer's code and origin – preferably OEM. |
| What to check in BMW E87 / F30 / X3 E83 brake discs? | Inspect: thickness, runout, cracks, and condition of the ventilation rim. Avoid tracks with deep corrosion. |
| How to check the front brake discs of a BMW X3 E83 without disassembly? | Using a run-out sensor – also possible with the disc mounted and with gentle rotation – the difference should be |
What should you pay attention to when purchasing braking system components from Global Parts?
- Used braking system components (discs, calipers, ABS module) offer an attractive price-quality ratio, especially for BMW models (E90, F30, E87, X3 E83/F25), Audi A3 8P and others.
- BMW E90 front/rear discs, F30 brake discs, E87, X3 E83/F25, Audi A3 8P rear discs – perfect provided checklist.
- Clamps – from a reliable source, tested.
- ABS sensors and modules – efficiency tested on computer. By purchasing wisely, used braking equipment from Global Parts allows you to combine safety, economy, and ecology without sacrificing OEM quality.
Definitions and parameters – discs, calipers, ABS/TPWS (VIN/OEM/PN, dimensions, types)
Brake discs are identified by their Ø (mm), nominal and minimum thickness, height "H," and type (solid/ventilated/drilled); for example, BMW E90 front brake discs were available in several diameters depending on the package. Calipers are selected by their disc diameter and carrier; for BMW E46 calipers / Audi A4 B6 rear calipers / Audi A4 B8 brake calipers / Audi A3 8P brake calipers, the piston type (fi) and carrier spacing are important. ABS : sensors can be magnetic (Hall) or inductive ; the phrases " BMW E46 front ABS sensor / BMW E46 ABS sensor / bmw e46 ABS sensor / BMW E46 ABS sensors, BMW E90 ABS sensor", W211 ABS sensor, Passat B7 ABS sensor – differ in pinout and cable length. ABS/ESP pumps (e.g. Audi A3 8P ABS pump, ABS pump BMW E46, 1K0 614 517 BD ) require PN/software version compatibility for full compatibility .
Matching procedure – step by step (VIN → PN/OEM → assembly/test)
Step 1 – Identification by VIN: select the kit for the specific brake code, disc diameter and ABS/ESP version (different plugs/software). Step 2 – Verify parameters: measure disc diameter and height; confirm ABS sensor type (Hall/inductive), cable length and plug; for ABS pumps, check the PN/OEM number (e.g. 1K0 614 517 BD ). Step 3 – Assembly and run-out check: clean the hub (hub run-out ≤0.02–0.03 mm ), assemble the disc and check the disc run-out ≤0.05 mm with a dial gauge; bleed the system according to the manufacturer’s procedure, and in the case of the Audi A3 8P/BMW E46 ABS pump, use the service function (bleeding via tester). Step 4 – Adaptations and logs: clear errors, perform sensor adaptations, and perform a 60→0 km/h road test; if pulsations occur, check the pad parallelism and wheel bolt torques. Have SRS/ABS work performed by a service center/mechanic.
Fit Examples – Most Common Aftermarket Plug-ins
Audi A3 8P rear discs / Audi A3 8P discs – different diameters for versions with/without EPB; selection by VIN eliminates surprises. BMW E90 320d rear brake discs and BMW E90 front brake discs – diameters depend on the package and year; used OEM set + brackets = hassle-free installation . Audi A3 8P brake calipers / Audi A4 B8 brake calipers / gold brake calipers (styling) – remember the disc diameter and bracket spacing; the visual "gold look" is best achieved on original carriers. ABS/ESP : Passat B7 ABS sensor (rear) and BMW E90 ABS sensor differ in signal/plug; ABS pump 1K0 614 517 BD – typical “plug-in” in the PQ35 platform with compatible software.
Table – quick match (phrase → what to check → limit/tip → effect)
| Phrase | What to check | Mounting Limit/Tip | Effect |
|---|---|---|---|
| BMW E90 front brake discs / BMW E90 320d rear brake discs | diameter, thickness, height | disc runout ≤0.05 mm | no vibrations, smooth braking |
| BMW E87 brake discs / BMW E90 front brake discs | package/year | clean hub, hub runout ≤0.03 mm | correct pad pressure |
| Audi A3 8P discs / Audi A3 8P rear brake discs | EPB vs cable | select the yoke according to the diameter | reliable plug-in |
| BMW E46 calipers / Audi A4 B8 calipers / Audi A4 B6 rear calipers | yoke spacing, piston diameter | piston/rubbers without corrosion | even pressure, no pulling |
| ABS sensor BMW E46 front / ABS sensor W211 / ABS sensor Passat B7 | signal type, plug | run the cable along the factory track | no ABS/ESP errors |
| ABS pump Audi A3 8P / ABS pump BMW E46 / 1K0 614 517 BD | PN/soft/beam | bleeding the tester | correct ABS modulation |
