Strut Bump Stop 4A0412131 for Audi A6 & Audi 100 | Supplier & OEM Guide

A strut bump stop is the elastomer element that defines how a strut behaves in the last part of its compression travel. On Audi suspension layouts, this small moulded part sits over the damper rod and stops the suspension from compressing metal to metal. Importers and workshop buyers normally arrive at it from one of four directions: the OE number 4A0412131, the Audi model range, the dimensions and material, or a request for a custom-moulded equivalent. This page answers all four from a procurement point of view.

What a Strut Bump Stop Does

Also written as jounce bumper, bump stopper, or strut buffer, the part is a moulded elastomer sleeve fitted over the piston rod. During normal driving it stays clear of the top mount. Under a hard compression event — a pothole, a speed bump, a fully loaded cabin — it engages progressively and turns what would be a metal impact into controlled resistance.

Three functions that matter to a buyer

• Damper protection: without a stop, the piston rod and internal valving absorb the full impact of bottoming out, which shortens oil seal life and leads to leaks.
• Noise and ride quality: a progressive elastomer stop softens the end of the stroke, removing the harsh suspension knock that drivers report over broken surfaces.
• Geometry control: it limits compression travel, helping preserve tyre-to-body clearance and suspension geometry when the vehicle is loaded.

Elastomer parts age. Heat, ozone, road salt, and repeated compression cycles harden the material until it cracks and loses its progressive behaviour. From that point the damper begins to bottom out and the failure spreads to the mount and the shock absorber. For the wider range, see our auto parts catalogue.

OE 4A0412131: Specification Reference

The item described here is a strut bump stop for Audi applications, referenced under OE number 4A0412131 and Bonpora number 4110058. The table below lists the data buyers usually ask for before requesting a quotation.

Reading the dimensions

Φ23.3 mm is the inner bore that fits over the damper rod, Φ56 mm is the outer diameter of the elastomer body, and 90.5 mm is the free length. The bore decides whether the part can be assembled at all; the free length decides when in the stroke it engages. A stop with the correct bore but the wrong free length engages earlier or later than the original, which changes load behaviour and generates fitment complaints after the parts have shipped. Compare all three values against the part removed from the vehicle before approving a substitution.

Why the material is polyurethane

Polyurethane suits this application. Compared with conventional rubber it resists tearing and oil exposure better, holds its shape across a wider temperature range, and can be moulded to a controlled hardness so the compression curve stays progressive rather than abrupt. That makes it a practical choice for daily-driven cars and for vehicles that carry regular loads, including estate and Quattro variants that work the suspension harder.

Audi Fitment Notes

In Audi part numbering, the 4A0 prefix identifies components from the Audi 100 / A6 family, and OE 4A0412131 is referenced for the applications listed above: Audi A6 (2005-2008), A6 Quattro (2005-2008), Audi 100 (2002-2004) and Audi 100 Quattro (2002-2004). Regional model naming differs — the same body line has been sold under different names in different markets — so the OE number on the removed part, or the vehicle identification number, remains the most reliable reference for ordering.

How to confirm fitment before ordering

1. Read the number on the old part. Bump stops normally carry a moulded reference, or sit alongside a dust boot and mount that do.
2. Match the platform, not just the badge. Two Audi models of a similar size can use different damper assemblies and different stops.
3. Compare all three dimensions. Bore, outer diameter, and free length together decide whether the stop behaves like the original.
4. Ask for a written cross-reference list. A supplier who works regularly with Audi chassis parts can confirm the application range and flag superseded numbers.

Sourcing Guide for Importers and Distributors

Bump stops are a low-unit-value, high-turnover line that supports higher-margin suspension sales. Sourcing them well is mostly about consistency rather than the lowest quotation.

What to confirm with a supplier

• Material grade: ask for the polyurethane grade and Shore A hardness rather than a generic PU description.
• Dimensional tolerance: request the inspection report for bore and free length, since these two values drive fitment claims.
• Batch consistency: elastomer parts are sensitive to cure conditions, so stable hardness across batches matters more than one good sample.
• Packaging: neutral export packaging is standard, but confirm whether branded or private-label cartons are available.
• Warranty terms: 1 year is typical in this category; check what evidence a claim requires.

Custom and OEM programmes

Suppliers with OEM and custom design capability can produce stops to a customer drawing or sample, including non-standard bore sizes, different hardness grades, and application-specific profiles. This suits distributors building a private-label suspension range as well as workshops servicing vehicles with modified ride heights. If you need a made-to-spec part, our auto parts sourcing team can review drawings and samples alongside OE-referenced items.

Lead times and order planning

For catalogue items held in stock, 15–30 days covers production and export preparation. New tooling adds development time, so plan the first order of a private-label line well before the selling season, and confirm the shipping method and destination port when requesting the quotation.

Installation and Inspection Notes

A worn bump stop is often discovered during damper replacement, but it can also be diagnosed from the driver seat.

Symptoms of a failed bump stop

• A heavy or metallic knock from the suspension over sharp bumps.
• Cracks, crumbling, or a hardened, shiny surface on the elastomer.
• Oil residue on the stop, which points to a leaking damper that has been over-compressing.
• Excessive squat under load or uneven ride height from side to side.

Replacement practice

Bump stops are normally replaced together with the damper mount and dust boot, since all three share the same access procedure and a similar service life. Replace both sides of the axle at the same time, support the suspension correctly before releasing fasteners, and torque components with the car at normal ride height. Compare the old elastomer part against the new item before installation to confirm that the three dimensions match.

FAQ

Does one bump stop fit every Audi A6 generation?

No. Suspension travel and damper dimensions change between generations, so each application has its own reference. The 4A0412131 number covers the models listed in the specification table; other generations need a different part. Confirm the application with the vehicle identification number or the removed part before ordering.

Will a polyurethane bump stop work on standard suspension?

Yes, provided the dimensions match the original. Polyurethane is a direct replacement material for this application, and the fitment decision is driven by bore, outer diameter, and free length rather than by material alone.

Can 4A0412131 be supplied as a custom part?

Where an existing mould matches your drawing, the OE reference is enough. Where the profile, hardness, or length differs, the part can be produced to your sample or drawing under an OEM programme. Send the drawing with the target annual volume for a specific quotation.

How long does delivery take?

Quoted delivery is 15–30 days for stock-referenced items, with export packaging prepared for sea or air freight. Confirm the shipping method and destination port so the quotation reflects the right terms.

Request a Quotation

If you are sourcing strut bump stops for Audi applications, or need a custom-moulded stop to your own specification, send us the OE number, vehicle platform, and annual volume. We can confirm availability, provide dimensional data, and quote on neutral export packaging or private-label terms.

Contact our auto parts team for pricing and samples →