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The rear jounce bumper 4M0512131 is the compression stop fitted inside the rear coil springs of the Audi Q7 and the related Q8, one buffer per side on the rear dampers. Bonpora moulds the same component in micro-cellular polyurethane as number 4110103 and supplies it direct from China to wholesale buyers. This guide explains what the part does, which vehicles the reference covers, and how to confirm the fit before ordering.
The genuine catalogue files the component under several names: jounce bumper, bumper, spring, buffer, stopper and tube. All describe one part, a cylindrical foam body that sits over the rear damper rod behind the dust boot, and the diagrams group it with the rear springs and dampers.
Under normal load the buffer stays idle: the coil spring carries the body of the SUV and the damper controls the wheel. When a loaded vehicle meets a sharp ridge, the rear suspension approaches the end of its stroke. The 4M0512131 compresses progressively at that point, turning the last stretch of travel into a controlled deceleration instead of a hard knock, and it shields the damper rod seals at full compression. On a vehicle of this weight the rear buffers work hard.
A worn buffer rarely announces itself on smooth roads. The usual signs are a hollow knock from the rear over sharp compressions and a crumbled foam body found while the dampers are already apart, which is why workshops renew the buffers during rear damper or spring work.
Genuine dealer catalogues list the 4M0-512-131 family for the rear axle, left and right, of the current Q7 and Q8 ranges and the electric SUVs built on the same platform. The reference splits into suffix variants, each tied to a suspension build.
| Reference | Genuine catalogue description | Application |
|---|---|---|
| 4M0512131G | without air suspension, standard suspension (PR 1BA) | Q7 2017-2025, 2.0 and 3.0 petrol and mild hybrid |
| 4M0512131 | base reference, quoted without qualifier | current Q7 and Q8 rear axle |
| 4M0512131A | without air spring; Q8 with air suspension, without sport suspension | Q7 2017-2026, Q8 2019-2026 |
| 4M0512131E | with air suspension, with sport suspension | SQ7, SQ8, RS Q8, e-tron Quattro, Q8 e-tron |
The suffix records the suspension build, and the builds are not interchangeable. Steel-sprung models without air suspension take the G entry with the standard-suspension PR code 1BA, air-sprung cars move to the A and E entries, and sport-suspension air builds take the E reference. The suffix from the VIN lookup or the removed part should travel with the order.
The genuine diagrams split the Q7 stops further by vehicle weight range, with separate entries for weight range 3-9 and 10-15, and they carry colour marks such as a light pink marking. The SQ7 diagram adds its own lengths, with 102 mm and 107 mm entries, and one later entry applies from a 29 September 2025 production date. When a number has worn away, the colour mark and a calliper measurement of the free length are the fastest way back.
Aftermarket suppliers file the same replacement across the wider platform range. Borsehung catalogues its buffer B10017 against both 4M0512131 and the alternative OE number 4KD512131, with the fitting position recorded as the rear axle.
The European catalogue filing for B10017 covers the A4 B9 saloon and Avant, the A4 Allroad B9, and the A6 C8 saloon, Avant and Allroad, with engines from the 1.4 TFSI to the 40 TDI mild hybrid. Chinese trade listings file 4KD512131 as the rear buffer of the A6L C8 and the Q5L, while the genuine US data ties the 4M0 number to the Q7 and Q8. Treat the A4 and A6 coverage as a supplier filing to confirm, not a promise.
Where an enquiry mentions the A4 B9 or A6 C8 platforms, request the OE number from the removed part, 4KD512131 or 4M0512131, and compare the bore, outside diameter and free length with the drawing data below.
The 4M0-512-131 family belongs to the rear axle only. The front suspension of the same Q7 takes the stopper 8R0412131D, a 96 millimetre buffer catalogued for the front, left and right, of the Q5 FY and the current Q7 without air suspension. The two differ in length and diameter and do not interchange, yet enquiries sometimes quote a front number for a rear order, so confirm the axle first.
The first generation Q7, built from 2006 to 2015, takes the 7L0-512-131 family at the rear and the 7L0412303 references at the front. Those numbers predate the current platform and do not interchange with the 4M0 series.
Three checks settle the identity in practice. First the position: 4M0512131 belongs on the rear axle only. Second the geometry: a bore near 15.7 millimetres, an outside diameter near 61.5 millimetres and a free length of about 114 millimetres. Third the build: air suspension, sport suspension and weight range each select a different variant.
Bonpora moulds this buffer in micro-cellular polyurethane rather than filled rubber.
| Property | Polyurethane (Bonpora) | Conventional rubber |
|---|---|---|
| Compression set | Low, recovers shape after repeated hits | Higher, takes a set over time |
| Ozone and heat ageing | Strong resistance | Cracks sooner in hot climates |
| Load consistency | Uniform batch to batch | Varies with compound |
| Unit cost | Moderate | Lower |
A full-size SUV carries a heavy body over long-travel rear springs, and its buffers work close to the load limit on bad roads. A compound with a low compression set keeps the free length stable through years of compressions, protecting the travel reserve. The polyurethane bump stop range applies the same approach across the other platforms in the catalogue.
The drawing data below summarises the part as supplied.
| Item | Value |
|---|---|
| Bonpora number | 4110103 |
| OE reference | 4M0512131 (4M0 512 131) |
| Position | Rear axle, left and right, 1 per side |
| Nominal size, Bonpora data | Bore 15.7 x OD 61.5 x length 114 mm |
| Material | Micro-cellular polyurethane |
| Country of origin | China |
| Warranty | 1 year |
| Delivery | 15-30 days |
| Packaging | Neutral export packaging |
| Custom service | OEM and custom design support |
The bore of 15.7 millimetres slips over the damper rod, the outside diameter of 61.5 millimetres locates the body inside the spring seat, and the free length of 114 millimetres places the part in the taller class of the family. Because the buffer sits behind the dust boot, it is often overlooked until the damper comes apart.
The genuine diagrams publish lengths only for selected entries, such as the 102 and 107 millimetre SQ7 stops, while other variants are identified by suffix, weight range and colour mark. The Bonpora figure of 114 millimetres describes the free length of the body as supplied; where a catalogue length for a specific suffix differs, the removed part remains the deciding check.
The catalogue equivalents include Borsehung B10017, filed against both the 4M0 and 4KD numbers, Bapmic BF0321360037 for the G suffix, and the ZPY replacement for the 4KD512131 twin. All describe the same rear buffer, sold individually.
Buyers want a faithful replacement sourced directly from a manufacturer with OEM capability.
Bonpora moulds buffers against the published OE data and ships from its own production line. Standard supply goes out in neutral export packaging on a 15-30 day schedule with a one-year warranty, and pricing is quoted against order volume. Samples can be requested before a container is committed.
For distributors with their own brands, the factory offers private labelling, branded boxes and private moulding. Custom design covers changes of compound hardness, free length or outer profile: send a sample or a drawing and the tooling, minimum order and lead time are confirmed before production. Programme details are on the custom parts page.
Send the OE number, the model year and build of the car, the quantity and the destination port to the export desk. If the number has worn away, quote the bore, the outside diameter, the free length and the colour marks, and the factory will match the drawing. Buyers building a wider programme for the Audi and Volkswagen platforms can browse the shock absorber parts catalogue, where buffers, mounts and related hardware are grouped together.
Steel-sprung cars without air suspension use the G reference with the standard-suspension PR code 1BA, air-sprung cars use the A or E reference, and sport-suspension air builds take the E entry. The suffix from the VIN lookup or the removed part should travel with the order.
The genuine US data ties the number to the Q7 and Q8 rear axle. European suppliers file the same replacement against the alternative OE 4KD512131 for the A4 B9 and A6 C8 ranges. Confirm by quoting the number on the removed part together with its dimensions.
One per rear side, two per vehicle, and the part is not handed, so left and right carry the same reference. Workshops normally renew the pair together, because mixing a new buffer with a worn one upsets the end-of-travel behaviour.
No. The front of the same car takes the 96 millimetre 8R0412131D, and the previous generation Q7 takes the 7L0-512-131 family. Neither interchanges with the 4M0512131.
Bonpora manufactures and exports suspension buffers from China for wholesale buyers worldwide. Quote 4M0512131 or Bonpora 4110103 with your quantity and destination, and the export desk will return unit pricing, packing details and the next available shipment. For the material background, see the polyurethane bump stops overview.
