Cheap BMW i3 Brake Master Cylinder

The BMW i3 is a fully electric vehicle and does not use a conventional hydraulic brake master cylinder — its braking system relies on an electro-hydraulic brake booster (sometimes called an iBooster or integrated brake unit) rather than a traditional master cylinder setup. What you may be looking for is the brake booster actuator or integrated brake control unit, which is the component that fulfils the equivalent function on the i3. Ask your breaker specifically for the electro-hydraulic brake unit or iBooster assembly rather than a conventional master cylinder. If you've been quoted a 'brake master cylinder' for an i3, it's worth confirming exactly which component is meant before purchasing.

The BMW i3 was launched in 2013 and received a significant update in 2017 (often referred to as the 2017 facelift or 94Ah battery generation), so a 2014 unit and a 2018 unit sit either side of that boundary. Generation can affect the integrated brake system specification, so you should not assume these are a straight swap. Name the exact generation and battery variant (60Ah or 94Ah) to your breaker and ask them to check the part number against your registration before buying. Never guarantee fitment across a generation boundary without that confirmation.

The i3 was offered with different battery capacities — the original 60Ah pack and the later 94Ah (and subsequently 120Ah) versions — and the overall vehicle weight varies slightly between them, which can in principle affect brake system specification. In practice the brake booster unit may share a part number across battery variants, but this is not something to assume without checking. Give your breaker your full registration so they can confirm the correct part number for your specific build. It's a quick check that could save you an expensive return.

The i3s, introduced in 2017, has a wider track, sportier suspension tune, and slightly higher power output than the standard i3, and it is reasonable to expect the brake system specification may differ to account for the increased performance. Because mid-generation brake specification differences are not always well-documented, you should confirm with the breaker that the unit they have matches your specific variant against your registration rather than assuming any i3 brake booster will fit any other. Trim level in the cosmetic sense (such as interior colour or alloy wheel style) does not affect fitment of the brake unit at all.

The i3 Range Extender (REX) carries a small two-cylinder petrol engine in addition to the electric drivetrain, which adds weight compared to the pure BEV version, and brake system components may have been specified differently as a result. Whether the integrated brake unit is identical across REX and non-REX variants is not something that can be stated with certainty here, so this is exactly the kind of question to put to your breaker with both your registration and the donor car's details to hand. Do not assume the parts are interchangeable without a part number match.

Rather than asking for a 'brake master cylinder,' ask your breaker for the integrated brake booster unit or electro-hydraulic brake actuator for your BMW i3, and give them your full vehicle registration so they can identify the correct specification. It is also worth noting the model year and battery variant (60Ah, 94Ah, or 120Ah) and whether your car is an i3 or i3s, as these details may affect which unit is correct. The breaker will be able to cross-reference part numbers against the donor car's registration to confirm compatibility before you commit to buying.