Rear Strut Bump Stop 8RD512131 for Audi Q5 8R A4 B8 A5 A6 C7 - Polyurethane Suspension Buffer Wholesale

The OE 8RD512131 is the rear suspension bump stop of the Audi Q5 8R and the A4 B8 generation, and aftermarket application tables extend the same position across the A5 and the A6 C7. The number circulates in the Chinese domestic parts market as the reference for the models built by FAW-VW, where the marking on genuine packaging also appears as L8RD512131. In the European aftermarket the same position is served by Febi 36722 and SWAG 30 93 6722, made against the German numbers 8K0 512 131 and 8K0 512 131 H. This page presents Bonpora No. 4110104, a polyurethane replacement made in China for wholesale export, nominal size Φ15.5 x Φ61.5 x 146.7 mm.

What the 8RD512131 Rear Bump Stop Does

The rear axle of the A4 B8 and Q5 8R uses coil springs with separate dampers. Inside each rear damper assembly, above the working chamber, sits the elastomer bump stop. It is the final travel limiter: when the suspension reaches full compression over a pothole, a speed bump or a fully loaded descent, the stop is progressively crushed and absorbs the energy the damper cannot take. It prevents harsh metal to metal contact, softens the last part of the travel and reduces the peak loads that pass into the dampers and the body. A healthy buffer keeps the rear axle quiet over broken roads and protects the components around it.

Why It Is a Regular Service Item

The buffer works at every full compression event, so it ages with mileage. Microcellular polyurethane hardens with time and heat, takes a permanent set under load and can crumble at the edges. A flattened stop shortens the working travel of the rear suspension, and the symptoms follow: a hollow knock from the rear axle over sharp bumps, a ride that turns harsh when the car is loaded, and faster wear on the rear dampers. Workshops inspect the buffer whenever the rear dampers are removed, and replace in pairs so both sides keep the same working height.

Fitment Guide: A4 B8, A5, Q5 8R and A6 C7

Aftermarket application tables span the whole B8 generation and the related models of the same rear suspension layout, while the China-built cars carry the 8RD512131 reference on the same position. The table below summarises the coverage; the removed part or a VIN check remains the final word.

Engines from the 1.8 TFSI to the S6 appear in the application lists, because the stop depends on the rear suspension layout rather than the engine. The same logic applies to the China-built A4L and Q5 produced by FAW-VW, which carry the locally produced 8RD512131 on the rear axle. S4, S5 and S6 quattro variants are listed as well.

Boundaries and Common Order Mistakes

Five boundaries keep this reference clean. First, the axle: 8RD512131 belongs to the rear axle; the front struts of the same cars take a separate, shorter buffer from the 8K0 412 303 series. Second, the height revision: this page covers the tall version around 145 mm for standard suspension builds; a short revision with OE 8K0512131D, about 109 mm tall, exists for other suspension variants and does not interchange. Third, the German catalogue variants: Q5 application lists also carry the 8R0512131 series, so a Q5 order should always be matched against the removed part. Fourth, the packaging marking: China-market genuine packaging writes the number as L8RD512131; the L prefix marks the locally produced line. Fifth, the quantity: one piece per side, two per car, replaced in pairs, with the dust bellows inspected at the same visit.

Specifications of the 8RD512131 Bump Stop

The table below lists the catalogue data of the Bonpora replacement.

Reading the Dimensions

Febi 36722 and SWAG 30 93 6722 read 145 mm thick at 0.13 kg for the German reference 8K0 512 131 H. Bonpora reads Φ15.5 x Φ61.5 x 146.7 mm at its own reference points. Differences of this scale are normal for elastomer parts, because each brand measures at different points and a free stop sits taller than one compressed on the damper rod. Treat both datasets as nominal and match the new stop against the removed original before releasing a full batch.

Polyurethane vs Rubber for the Jounce Bumper

The OE stop and the main aftermarket equivalents are produced in microcellular polyurethane or conventional rubber. The material decides how the stop behaves across years of compression cycles, oil contact and weather.

Rubber remains serviceable in mild climates and standard duty. Polyurethane keeps its working height longer under repeated compression, which decides how soon a loaded A4 Avant or Q5 starts to knock at the rear axle.

Which Material for Which Market

European and North American distributors restock polyurethane as the primary line because it matches the OE material family. Price driven tenders in some regions still call for rubber versions. Bonpora produces the polyurethane line as standard and can quote rubber on request against the same drawing.

Sourcing by OEM Number 8RD512131

Ordering by OEM number is the most reliable route when the marking is still readable. The number appears as 8RD512131 or L8RD512131 in the Chinese parts market, and as 8K0 512 131 or 8K0 512 131 H in the German catalogues; all forms identify the same rear axle position and Bonpora reference 4110104. For orders that span more platforms, the polyurethane bump stops range groups references by system and model family and shortens the quotation process.

Cross Reference Checklist

• OE 8RD512131 or L8RD512131 marking readable on the removed part: order Bonpora 4110104.
• Febi 36722 or SWAG 30 93 6722 quoted: same application, polyurethane, 145 mm tall, for the German references 8K0 512 131 and 8K0 512 131 H.
• Meyle 100 742 0026, VAICO V10-3372, Sachs 900 225, KYB 910120, Monroe PK278, Optimal AK-735450, Birth 51959, Metalcaucho 40448, Topran 113 452 or Maxgear 72-2566 quoted: further European equivalents.
• Kits that add the dust bellows: Febest ADSHB-8K5R-KIT, GSP 5405041PK or Monroe PK279.
• Short rear buffer around 109 mm requested: OE 8K0512131D family (Birth 52379, VEMA 380294, Optimal F8-7719), a different suspension build.
• German Q5 catalogue variant requested: 8R0512131 series, with VAICO V10-6414 quoted against 8R0512131E.
• Front axle request: 8K0 412 303 series, a shorter front buffer.
• Number too worn to read: identify by make, model, model year, axle position and suspension build, confirmed with the VIN.

Wholesale Supply from a Chinese Auto Parts Factory

This bumper is manufactured in China as a catalogue item with existing tooling, priced for carton, pallet and container quantities. Typical buyers include Audi specialists and suspension parts importers across Europe, the Middle East, Southeast Asia and Latin America. Because one reference serves the A4, A5, Q5 and A6 families, one pallet position covers several model lines. Orders ship in neutral export packaging, delivery takes 15 to 30 days depending on volume, the warranty period is 1 year, and samples can be arranged to verify bore, height and hardness before a bulk commitment.

Quality Control Points

Each production batch is checked for bore, outer diameter, overall height and material hardness, with visual inspection for flash, voids and surface defects. Dimensional records are kept per batch, so repeat orders match the approved sample and support the 1 year warranty.

Custom and OEM Manufacturing Support

Beyond the catalogue part, the same line supports OEM and custom design work: adjusted hardness, modified bore, outer diameter or height, coloured material, branded packaging and private label marking. For a custom project, send a drawing or a sample with the expected annual volume; a first article sample confirms the fitment before series production begins.

Custom Project Workflow

The workflow is simple: drawing review, material and hardness proposal, first article sample, fitment check, then batch production with per batch inspection records. Most projects move from drawing to approved sample within a few weeks.

Installation and Replacement Notes

The buffer is renewed with the rear dampers or on its own when flattened. The car is raised and the rear wheel removed, the lower damper bolts are released and the damper assembly is lowered far enough to slide the old buffer off the rod. Inspect the dust bellows, the top mounts and the rear dampers at the same visit, because leaking damper oil is the fastest route to a destroyed buffer. A stop seated unevenly wears on one side, so check the seating.

FAQ

Which models does the 8RD512131 bump stop fit?

The rear axle of the Audi Q5 8R (2008-2017) and the A4 B8 saloon and Avant (2007-2016), including the A4 Allroad, with aftermarket tables extending to the A5 B8 and the A6 C7 (2011-2018). One piece per side, two per vehicle, replace in pairs. The China-built A4L and Q5 carry the same position under 8RD512131, marked L8RD512131 on genuine packaging. A VIN check or the number on the removed part confirms the order.

Is 8RD512131 the same as 8K0512131?

They serve the same rear axle position. 8K0 512 131 and 8K0 512 131 H are the German catalogue numbers, and Febi 36722 with SWAG 30 93 6722 serves that family in the European aftermarket at 145 mm. 8RD512131 is the reference used for the China-built versions of the same models. Match the marking on the removed part when ordering.

What is the difference between the 145 mm and the 109 mm rear buffers?

The height marks different suspension builds of the same rear axle position. The tall version around 145 mm covers standard suspension builds of the A4 B8, A5, Q5 8R and A6 C7. The short revision, OE 8K0512131D at about 109 mm, belongs to other suspension variants and does not interchange. The German Q5 catalogue also lists the 8R0512131 series. Compare the removed stop height before ordering.

Can this bump stop be made in a custom size, and what are the trade terms?

Yes. OEM and custom design support covers adjusted hardness, modified dimensions, coloured material and private label packaging. Delivery time is 15 to 30 days depending on quantity, packaging is neutral export with branded options on request, and the warranty period is 1 year. Send a drawing or a sample with the target annual volume to receive a quotation.

Request a Quote

Send the OEM number 8RD512131, the Bonpora number 4110104, the quantity and the destination port, and the sales team will confirm specification, packing and delivery schedule. Buyers building a wider suspension programme can review the chassis and suspension parts range, and the full auto parts line covers rubber, steering and chassis components from the same factory.