BMW 4 Series Brake Discs: Specs, Fitment & Wear Symptoms

On the 4 Series, what's commonly called "warped discs" is genuinely almost always uneven pad deposits, since cast iron is genuinely hard to warp.

Illustration for editorial purposes

OEM Part Number: 34118848417

Genuinely confusing naming worth knowing: the "M Sport" trim package (330mm front discs) and the separately-optioned "M Sport Brakes" (option code S2NHA, 340mm front discs with 4-piston Brembo calipers) are two genuinely different things despite the near-identical name — confirm exactly what's fitted before assuming disc size from the trim badge alone.

Standard trims, front disc (shared across 1/2/3/4 Series, confirmed for F32/F33/F36 428i)	BMW OEM: 34118848417 — 312mm diameter, 24mm thickness
M Sport trim package, front discs	330mm diameter — larger than standard, but not the same as the M Sport Brakes option below
M Sport Brakes option (S2NHA), front discs	340mm diameter, vented, 30mm thickness, with 4-piston Brembo calipers
M4/M440i, front discs	380mm+ diameter — a significantly larger, genuinely different performance specification

The Part That Pads Depend On

Discs and pads work as a pair, and neglecting one tends to accelerate wear on the other — which is exactly why worn discs so often get discovered during what was meant to be a routine pad change.

Before you buy: disc size and design vary by trim, engine size and whether your car has the standard or "sport" brake package. Always confirm against your VIN before ordering.

BMW 4 Series Brake Discs reference plate

What They Do

Brake discs provide the surface the brake pads clamp against to slow the car, converting momentum into heat through friction. Larger, sportier trims of the 4 Series typically use bigger discs than standard versions to handle the additional heat generated by more aggressive braking.

A Genuinely Important, Honest Clarification Worth Knowing — BMW 4 Series Brake Discs

If a vibration under braking has been diagnosed as warped discs, this is genuinely worth knowing: what's commonly described as "warped discs" is, in reality, almost always caused by uneven deposits of pad material on the disc surface, since cast iron itself is genuinely difficult to warp under normal driving conditions.

A genuinely alarming, honest account worth knowing: documented cases describe fast-fit chains replacing "warping" discs under warranty multiple times within less than a year, with owners suspecting the cheapest available parts were being used.

It's also genuinely worth knowing a useful fix worth trying: thoroughly cleaning the mating surfaces between the wheel hub and the disc, or better still fitting new hubs entirely, has been documented resolving this kind of persistent vibration.

Wear Symptoms, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Brake Discs Guide for warning signs to watch for, confirming fitment against your VIN, and choosing a reliable aftermarket disc.

More BMW Brake Discs

The same part, covered across other BMW models.

BMW 4 Series Brake Discs: Specs, Fitment & Wear Symptoms

OEM Part Number: 34118848417

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A Genuinely Important, Honest Clarification Worth Knowing — BMW 4 Series Brake Discs