Strut Bump Stop for BMW OE 31331140140 | Polyurethane Jounce Bumper Supplier

BMW suspension is tuned to keep the car flat and composed at speed, and the strut bump stop is part of that tuning. OE 31331140140 is the polyurethane jounce bumper specified for BMW front struts, and for importers, parts distributors and independent workshops it is a recurring line on suspension repair orders. This page sets out the technical data of 31331140140, how to confirm it against the vehicle in front of you, the symptoms that point to a worn bumper, and the routes purchasing teams normally use to source it: by OE number, by model, or through a custom development programme.

What a Strut Bump Stop Does on a BMW

A strut bump stop, also written as jounce bumper, buffer or strut bumper, is fitted on the piston rod of the strut, normally inside the dust boot. In normal driving it sits clear of the strut mount. Under a hard compression event, a pothole, a speed bump or a fast corner with load transfer, it becomes the last spring in the system: it absorbs the final part of the suspension travel and stops the damper from bottoming out metal to metal.

Because the material is progressive, the resistance it adds rises steeply as it compresses. That gives the chassis a controlled end stop instead of a sudden impact, which protects the damper, the top mount and the body structure around the strut tower.

Position and interaction with other suspension parts

The bumper works together with the strut mount bearing, the dust cover and the coil spring. A collapsed bumper changes the load path into the mount, so it is common to find a worn bump stop and a noisy top mount diagnosed in the same job. Workshops that replace these items as a set generally see fewer comebacks, and parts sellers who stock the full strut assembly, not just the bumper, can serve that habit.

Why polyurethane instead of rubber

Older jounce bumpers were moulded from rubber. Microcellular polyurethane has largely taken over because it can be moulded to a defined density gradient, recovers its shape after repeated compression and resists ozone, oil and road salt, which matters in winter-salted European markets. It also tolerates the higher loads of firmer sport suspension layouts. The trade-off is that formulation and moulding control decide everything: two bumpers that look identical on a drawing can behave differently if density and cell structure are not controlled. That is why buyers of polyurethane bump stops usually ask for batch-level inspection records rather than judging from a single sample.

OE 31331140140 Strut Bump Stop: Technical Data

The figures below are the control values for this part number. Dimensions are moulded values, measured before installation.

Read the size notation as an inner bore of 19.36 mm, an outer diameter of 67 mm and an overall height of 89.8 mm. Confirm these three dimensions against the strut being serviced: a bumper with an oversized bore will not seat correctly on the piston rod, and one that is too short will not control the travel as intended. Across BMW generations the platform specifications differ, so the dimensions, not the badge, are the decisive check.

How to Identify the Right Bump Stop for a BMW

Sourcing by OE number

The fastest route is the OE reference. A search for 31331140140 or for the Bonpora reference 4110087 returns the exact item without ambiguity. Importers who maintain a cross-reference database usually map the OE number to their own internal SKU, so a quotation can be issued in minutes rather than hours.

Vehicle-based search and cross-reference confirmation

The second route is model-based: BMW series and model, then year and suspension type, including whether the car left the factory with sport or M-sport running gear. This helps when the customer has no part number, but it should be treated as a first filter rather than a final answer, because one model line can cover more than one strut specification. A third route is cross-referencing aftermarket catalogue numbers. When two references disagree, trust the measured dimensions over the catalogue description.

Checking the old part in the workshop

Before ordering, inspect the removed bumper for the moulded OE marking, measure the bore and height, and photograph the strut rod end. It takes a couple of minutes and avoids the most common return reason in suspension parts: a correct-looking bumper with the wrong bore or height.

Symptoms of a Worn Jounce Bumper

• Metal-to-metal contact or a heavy thud over speed bumps, potholes and expansion joints.
• Visible cracking, crumbling, or a bumper that has compressed and lost its original height.
• Dust boot damage where a collapsed bumper has been rubbing.
• Uneven ride height or early wear on the strut mount bearing.
• Oil weeping from the damper, which often follows repeated bottoming out.

No single sign is conclusive. A bumper is best judged as part of the strut assembly, and replacing it during a shock absorber overhaul is usually cheaper than a separate strip-down later. Buyers who also stock shock absorber parts can offer the complete repair instead of a single line item.

Sourcing OE 31331140140 in Volume

Order quantity, packaging and lead time

Standard production runs follow the published 15-30 day delivery window, and neutral export packaging is available so cartons can carry your own label. Carton and pallet configuration is agreed before the order is released, which keeps container loading predictable. To verify fitment before committing to a full run, request a sample set with the batch inspection record attached.

Custom formulations and OEM programmes

Beyond the catalogue part, polyurethane components can be adapted: density and stiffness changed for a heavier or lowered vehicle, height adjusted for a modified spring, or a new bumper developed from a drawing or a used sample. Tooling for a new mould is normally the main cost driver, so it makes commercial sense when a programme runs over several seasons. What can be modified is summarised under custom parts.

Quality Points to Confirm Before Ordering

• Material grade and density of the specified PU compound.
• Dimensional report against the 19.36 x 67 x 89.8 mm control values.
• Compression or load-deflection data where the application is load-sensitive.
• Ageing and ozone resistance testing for markets with demanding climates.
• Traceability from batch code to production date.

A supplier that answers these five points without prompting is normally one that controls its own moulding rather than trading from stock. The same checks apply across the wider range of chassis and suspension components.

FAQ: Strut Bump Stops and OE 31331140140

Is OE 31331140140 a front or a rear bumper?

This reference is used on BMW front strut applications. Because specifications vary between model generations and trim levels, confirm the position with the strut layout and the bore dimension rather than the model year alone.

How long does a polyurethane bump stop last?

Service life depends on road conditions and loading. In normal passenger car use a correctly specified polyurethane bumper is expected to outlast the damper it is paired with, but repeated heavy bottoming out will shorten it.

Can the bump stop be replaced on its own?

Yes. It can be changed without replacing the whole strut, although it is more economical to combine the work with a damper or top mount replacement while the strut is already apart.

Do you support custom sizes or OEM marking?

Custom dimensions, compound changes and customer-branded packaging are available subject to order volume and tooling. Send the drawing or a sample together with the expected annual quantity for a quotation.

Request a Quotation for OE 31331140140

If you are comparing suppliers for OE 31331140140, or you need a polyurethane jounce bumper developed for another BMW platform, send the OE number, the required dimensions and your target quantity. A BONPORA sales engineer will reply with product data, packaging options and an indicative lead time, so the line can be priced into your next buying cycle.