BMW F20 F30 F32 Front Strut Bump Stop OE 31336855440 | PU

The OE 31336855440 is the front spring bumper that BMW dealer catalogs file as Additional Shock Absorber, Front and parts platforms list as rubber buffer, suspension. It slides over the piston rod of the front strut and cushions the last of the travel before the damper bottoms out. Bonpora molds this profile as part number 4110233 in micro-cellular polyurethane, with a 24 mm bore, a 72 mm outer diameter and a 95 mm free height. One car needs two pieces, one per front strut, and the same reference serves both sides. The part is produced in China, covered by a 1 year warranty, packed in neutral export packaging and shipped within 15 to 30 days, with OEM and custom design support for project buyers.

What makes this number worth a full page is the suspension logic behind it. The same bumper covers an unusually wide chassis range, from the 1 Series hatchback to the 4 Series Gran Coupe, the X1, the X2 and two MINI estates, yet it only fits cars on standard, non-lowered suspension. The M Sport cars of the very same bodies run a shorter and stiffer piece, 31336857729, and the rear axle runs its own group under the 3353 prefix. The sections below sort out the chassis coverage, the suspension split, the aftermarket crosses and the dimension band.

What the Front Spring Bumper Does

The bumper is the last line of defense inside the strut assembly. Under normal load the coil spring carries the weight and the buffer never engages. When the wheel drops into a deep pothole or the car runs fully loaded, the spring compresses toward coil bind and the polyurethane bumper takes over as the final cushion. Its micro-cellular structure compresses progressively and rebounds without permanent set, protecting the damper seal, the piston rod and the top mount. Because the piece sits exposed to debris, moisture and heat, the foam degrades with age, and a crumbled buffer is a common source of front end knocks on F-chassis cars with higher mileage. BMW requires a new bumper whenever a shock absorber is replaced, which makes the profile a steady service item alongside every strut job.

Fitting Position and Quantity

Dealer data places 31336855440 on the front axle, left and right, one piece per side. BMW lists the part inside group 31 33, the supplementary spring and buffer section of the front suspension, filed with the guide supports and spring pads. The rear axle of the same cars takes a different piece from the 3353 group, so a front or rear mix-up is the first thing to rule out when a quoted size looks wrong. Buyers comparing related shock absorber parts will meet the same axle logic across the BMW range.

Specifications of Bonpora 4110233

One profile, one set of figures. The table below is the basis for every cross check that follows.

Fitment: One Bumper Across the F-Series Range

Dealer and trade catalogs tie 31336855440 to an exceptional span of front wheel drive and all wheel drive BMW platforms built from 2011 onward, plus the MINI estates that share the hardware. Engine coverage runs from the 95 hp three cylinder petrol up to the 360 hp M135i, so the list below is organized by chassis rather than by engine. One part number, eleven bodies, two brands.

Standard Suspension Only

The one filter that matters more than the chassis list is the suspension option. BMW fitment notes for this reference say stock, non-lowered suspension, and suspension specialists repeat the point in their application notes: bump stops are specific to suspension options. The trade platform files the part for the whole engine range of these bodies, while a US suspension house restricts its 855440 listing to standard cars and excludes the wagon, the Gran Turismo and the convertibles it does not stock. The safe habit for quotations is simple: take the VIN or the option codes, confirm the car is not on M Sport or lowered springs, and only then send the price.

The 3133 Number Family: Standard vs M Sport

BMW splits the front bumper of these platforms by suspension option, and the suffix carries the difference. Reading the group number together with the option code keeps quotations inside the right variant.

Front 3133 or Rear 3353

One prefix separates the two axles: 3133 for the front strut bumpers, 3353 for the rear shock buffers. The rear side carries two references, and catalogs assign them by chassis and suspension in the same way as the front, so the axle question comes before the variant question on every inquiry. The wider chassis and suspension parts range follows the same group-number logic.

Aftermarket Cross References and the Kit Question

The aftermarket covers this reference with a short and clean list, and none of the carriers files the piece inside a dust cover kit, which keeps quotations simple. Every line below is a bare bumper for the front axle.

Reading the Dimension Band

Catalogs frame the same piece with slightly different figures. The BMW dealer data on the European trade platform reads 90 mm tall with a 25 mm bore and a 72 mm outer diameter, the Bonpora profile measures 95 mm free height with a 24 mm bore, and an aftermarket copy lists 90 mm height, a 28 mm bore, a 54 mm top and a 71 mm base. The outer diameter is the stable anchor at 72 mm, while height and bore sit in a measuring band, because the foam block is conical and each source reads it at its own points. The FEBEST packaging at 90 x 70 x 70 mm supports the same picture. Treat the 72 mm outer diameter as the hard filter and confirm the free height against a sample before shipping an order.

How Buyers Find This Part

Part type plus size

Searches like BMW front bump stop 72 mm, jounce bumper 90 mm or strut buffer 24 mm bore land on this profile. The 72 mm outer diameter is the fastest filter, because the M Sport piece of the same cars is shorter and neighboring BMW profiles cluster at other diameters.

Part type plus OE number

Buyers who hold a number search 31336855440 bump stop, 31 33 6 855 440 equivalent or BMD-F20F jounce bumper. The spaced dealer spelling, the plain spelling and the FEBEST and Dorman crosses return different catalogs, so listings should carry all of them.

Model plus part

Typical combinations are F30 front bump stop, BMW 320i jounce bumper, X1 strut bumper and 328i spring buffer. Model searches work, yet the suspension split above explains why a VIN or option-code check belongs in every reply.

Supplier plus custom request

Project buyers with a sample or a drawing search custom PU bump stop manufacturer and OEM jounce bumper supplier. The same molding line that produces 4110233 serves molded polyurethane bump stops variations in height, bore and hardness, and the OEM and custom parts service page explains the drawing to sample process.

Factory-Direct Supply of the 31336855440 Profile

Bonpora produces the 31336855440 profile in-house as number 4110233 and ships it from China in neutral export packaging under a 1 year warranty, with a standard dispatch window of 15 to 30 days. Molded polyurethane lets the same tool set serve height, bore and hardness variations for fleet and project inquiries, and OEM and custom design support covers customers who arrive with a drawing or a worn sample instead of a number. Wholesale buyers can order the profile packed under their own brand. Every batch is checked for height, outer diameter and bore before packing, which keeps the dimension band from the tables above stable across orders. For prices on 31336855440 equivalents, send the OE number or the target dimensions and the quotation follows within one working day.

Frequently Asked Questions

How many pieces does one car need?

A front set is two pieces, one left and one right, and the same reference fits both sides. The rear axle takes a different buffer from the 3353 group with its own references, so two front pieces never cover a full car.

Does 31336855440 fit an M Sport car?

No. Bump stops in the F-Series follow the suspension option, and M Sport or M Adaptive cars of the same bodies run the shorter and stiffer 31336857729. Check option codes S704 or S2VF, or confirm by VIN, before quoting.

Why do catalogs show 90 mm and 95 mm for the same part?

The bumper is a conical foam block and every source measures it at its own points: the dealer data reads 90 mm tall with a 25 mm bore, the Bonpora profile 95 mm with a 24 mm bore, while the outer diameter stays at 72 mm across all sources. Confirm by outer diameter and free height together.

Should the buffer be replaced with the shock absorber?

BMW requires new bump stops whenever a new shock is installed, and worn foam accelerates seal wear on the fresh damper. Performance dampers often ship with their own stops, so check the damper box first. Bonpora quotes single pieces and pair sets on request.