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Audi A6 strut bump stop 4F0512131C is the rear suspension buffer of the C6 generation, the executive range Audi built from 2004 to 2011. Catalogues assign the reference to A6 and S6 vehicles equipped with air ride suspension, with one cushion on each side of the rear axle. Bonpora manufactures the replacement as number 4110109 in micro-cellular polyurethane, following drawing data of 22 mm bore, 62.5 mm outer diameter and 104 mm free height. This page explains the application, the sourcing situation around a reference some catalogues no longer list, and how trade buyers order it.
The A6 C6 carries its kerb weight and its occupants on sophisticated rear suspension, and on air ride versions an air spring carries the load itself. Whatever the spring medium, the axle still moves through its full travel over deep potholes and loaded kerb strikes. At that moment the polyurethane buffer at the end of the travel compresses progressively: the final stage feels firm rather than harsh, and the components around it, including the air spring assembly and the damper, never absorb a direct metal-to-metal impact.
A worn or collapsed buffer announces itself through a hard knock from the rear over rough surfaces and a harsher ride at the end of the compression stroke. The buffer costs a small fraction of the parts it protects, which is why workshops inspect and renew the cushions whenever rear suspension work is carried out.
The catalogue note attached to this reference, A6, S6. All. With air ride suspension, tells the buyer where the part sits in the range: it belongs to the versions fitted with adaptive air suspension, on the rear axle, left and right. The numbering follows the VAG logic trade buyers know well: the 4F prefix identifies the C6 platform, the 512 group covers rear axle suspension and the 412 group the front. Catalogues list the neighbouring front cushion 4F0412131D at about 85 mm and the rear cushion 4F0512131D of the 8RB Allroad version at about 130 mm, while this reference sits between them in height. The C suffix marks a revision of the base number 4F0512131.
The A6 C6 is now between fifteen and twenty years old, and the genuine supply situation reflects that age. One large US parts catalogue lists the genuine 4F0512131C as permanently NLA, no longer available through the dealer network. The vehicles themselves remain in daily service across Europe, North America and the export markets, so an aftermarket replacement built to the same drawing data keeps the fleet on the road, and a polyurethane programme with batch control offers a supply route that does not depend on remaining dealer stock.
The published parameters of the replacement are summarised below.
| Parameter | Value |
|---|---|
| Product Name | Strut bump stop (rear axle suspension buffer) |
| OE Number | 4F0512131C (base reference 4F0512131) |
| Bonpora Nos | 4110109 |
| Fitment | Audi A6 / S6 C6 with air ride suspension, rear axle |
| Nominal Size (Bonpora drawing data) | Φ22 × Φ62.5 × 104 mm |
| Catalogue reference figures | Width about 61 mm (aftermarket listing); genuine part weight about 0.5 lb |
| Position | Rear axle, left and right, one per side |
| Material | Polyurethane (micro-cellular) |
| Country of Origin | China |
| Warranty | 1 year |
| Delivery Time | 15-30 days |
| Packaging | Neutral export packaging |
| Custom Service | OEM & custom design support |
Bonpora supplies this buffer inside a wider polyurethane bump stop programme that covers European, American, Korean and Japanese references, and every batch is checked for size and hardness before packing.
The Bonpora drawing states a bore of 22 mm, an outer diameter of 62.5 mm and a free height of 104 mm. Aftermarket catalogue data for the same reference prints a width of about 61 mm, which agrees with the outer diameter within rounding. The listings describe the same cushion from different measurement points, not different parts. Treat the drawing values as nominal, compare the removed buffer against all three figures, and request a sample where the application is critical.
US catalogue fitment data for the 4F0512131C covers the 2005 to 2011 A6 range on the C6 platform: the A6 Base with the 3.2 litre V6, the A6 Quattro in sedan and Avant body styles with 3.0, 3.2 and 4.2 litre petrol engines, and the S6 with the 5.2 litre V10. The parts diagrams place the buffer in the rear suspension section, item positions left and right, and the note about air ride suspension runs through the whole list. A V10 super sedan and a six cylinder Avant share the cushion because the part depends on the axle layout and the suspension variant, not on engine output.
Two checks keep an order clean. First, confirm the suspension variant: the reference belongs to cars with air ride, and a steel-sprung C6 may call a different cushion. Second, compare the three measurements of the removed part with the drawing data, and check which end of the car it came from, because the front group 4F0 412 131 and the taller Allroad rear cushion 4F0512131D look similar in photographs. Where doubt remains, send photographs with the three measurements and the axle position, and the factory confirms the match before production.
Buyers sometimes assume that an air spring makes the bump stop redundant, because the air spring levels the car and carries the load. The opposite is true. The air spring controls the ride height within its working range, but sudden inputs, a loss of pressure in one corner or an extreme compression still push the axle to the end of its travel, and that is where the buffer works. It also protects the air spring bellows from over-compression, and since a replacement air spring is one of the most expensive lines in C6 suspension repair, the small cushion earns its place many times over. Workshops that maintain C6 cars treat the buffers as normal wear items alongside mounts and dust covers.
Wholesalers building mixed containers often order buffers by dimension, because one geometry can serve several references across brands. For this line the checklist is short: measure the bore, the outer diameter and the free height on a new part, compare the three figures with the drawing data above, and confirm the material is micro-cellular polyurethane.
Two precautions keep the measurement honest. Never take the height of a flattened used cushion as the reference value, because years of compression leave a permanent set; use the drawing height or a new sample instead. Also check the bore over the locating spigot: a 22 mm bore suits a specific seat diameter, and a loose fit wears the cushion off-centre and shortens its life.
Ordering by the OE reference removes the ambiguity of model year ranges and suspension variants.
The buffers fitted at the factory were cellular rubber, and much of the aftermarket supply for this reference is listed in PU. Both materials do the same job with different behaviour along the compression curve.
| Property | Cellular Rubber | Micro-cellular Polyurethane |
|---|---|---|
| Compression behaviour | Progressive, softer initial stage | Progressive, firmer late-stage support |
| Shape retention | Permanent set possible over time | Holds shape through repeated cycles |
| Ageing and ozone resistance | Cracking possible at high mileage | Generally strong |
| Oil and grease contact | Swelling possible | Better resistance |
| Typical market role | Original equipment material | Common replacement material |
Neither material is automatically better. Rubber remains fully serviceable, while polyurethane is chosen where firmer late-stage support and longer shape retention are wanted, and several aftermarket catalogues already list this reference in PU. Buyers who need a defined hardness receive the data sheet with the batch, and the shock absorber parts catalogue lists matching buffers, dust covers and mounts for consolidated shipments.
Beyond catalogue supply, Bonpora runs a custom service for buyers who need their own part number, a modified geometry or branded packaging. Engineering starts from a dimensioned drawing, a physical sample or an existing reference such as this one, and adjusts bore, outer diameter, height and hardness to the application. Tooling is produced in-house, so sampling and revision cycles stay short. Options include part number marking, private label bags and cartons, and consolidated loading with other suspension lines; the custom parts page describes the process and what a quotation needs.
Suspension buffers work amid wide temperature swings, continuous compression cycles and contact with dirt, water and road salt. Incoming polyurethane is checked against specification, dimensions are sampled with calibrated tools, hardness is measured on every batch, and visual inspection covers pores, cracks and flash. Goods are packed only after the batch record is complete.
Standard packing is a poly bag per piece in export cartons sized for pallet loading. Neutral export packaging is the default, which lets distributors sell under their own brand where regulations allow. Lead time is 15 to 30 days from order confirmation and samples usually ship sooner. Bonpora quotes ex-works, FOB and CIF terms and can consolidate this reference with other Audi lines.
Catalogues list it for the rear axle of the A6 C6 range from 2005 to 2011, including the A6 Base 3.2, the A6 Quattro sedan and Avant with 3.0, 3.2 and 4.2 litre engines and the S6 with the 5.2 V10, on versions equipped with air ride suspension. Coverage differs between catalogues, so confirm against the VIN or the removed part before ordering in volume.
The nominal drawing data is a 22 mm bore, a 62.5 mm outer diameter and a 104 mm free height; aftermarket catalogue data prints a width of about 61 mm. Measure the removed part at the same points and request a sample where the figures are critical.
4F0512131 is the base reference and 4F0512131C is a revised form of the same rear axle buffer. Suppliers quote either number and offers can carry the two references side by side; confirm the suffix against the marking on the removed part.
For the rear axle, one cushion per side. The front axle of the same platform belongs to the 4F0 412 131 group such as 4F0412131D at about 85 mm, and the 8RB Allroad rear cushion 4F0512131D is about 130 mm tall. Check the axle position and the height before ordering.
For prices, drawing data and samples for the 4F0512131C rear axle buffer, send the reference, the quantity and the destination port to the Bonpora sales team. Quotations for stock items usually go out within one working day, and this line can be combined with other Audi suspension references.
