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A rear bump stop is one of the least expensive parts on a BMW 3 Series, yet it decides how the back of the car behaves at the end of every suspension stroke. OE 33531138109 is the strut bump stop that BMW specified for the rear axle of E36 and E46 cars built with sport or lowered suspension, including the M Sport chassis variants. If you are sourcing this number for a workshop chain, a suspension rebuild programme or a European aftermarket brand, the fitment restrictions matter just as much as the price.
This guide explains what 33531138109 is, which vehicles it covers, how it differs from the standard-suspension bump stop 33531136395, and how to build a purchasing specification that will pass your technical team without a second round of samples.
BMW catalogues 33531138109 as a rear axle additional shock absorber — in workshop English, a rear jounce bumper or rear shock bump stop. It slides over the piston rod of the rear shock absorber, inside the dust boot, and its only job is progressive: during normal driving it stays clear of the damper body, and under a heavy compression event it cushions the last part of the stroke so metal never reaches metal.
The number uses BMW’s standard twelve-character logic. The 33 prefix identifies the rear axle group, 53 is the shock absorber and damper sub-group, and the trailing digits identify the individual part and its revision level. Because this is a rear-axle reference, it is not interchangeable with front strut bump stops such as 31331124449 — a distinction that catches out buyers who search by dimension alone.
The table below lists the parameters of the production part we manufacture against this reference. Values follow our current drawing; confirm against your own drawing version before tooling or volume release.
| Parameter | Value |
|---|---|
| Product name | Strut bump stop (rear jounce bumper) |
| OE reference | 33531138109 / 33 53 1 138 109 |
| Bonpora No. | 4110084 |
| Fitting position | Rear axle, left and right |
| Dimensions | Φ10.44 mm bore x Φ56 mm body x 91 mm length |
| Material | Polyurethane (microcellular PU) |
| Fitment | BMW E36 and E46, sport / lowered chassis |
| Quantity per vehicle | 2 (replace as a pair) |
| Country of origin | China |
| Warranty | 1 year |
| Delivery time | 15-30 days |
| Packaging | Neutral export packaging |
| Custom service | OEM and custom design support |
The 10.44 mm bore is sized for the rear damper piston rod, and the 56 mm body diameter is what gives the stop its progressive rate. If your customer’s vehicle is running an aftermarket coilover with a different rod diameter, the bore dimension becomes the first thing to verify rather than the overall length.
33531138109 is a rear-axle part for the E36 and E46 generations of the BMW 3 Series, released only for chassis with the sport or lowered suspension specification. Key applications include:
| Chassis | Models | Notes |
|---|---|---|
| E36 (1992-1999) | 318i, 318is, 318ic, 323is, 323ic, 325i, 325is, 325ic, 328i, 328is, 328ic, M3 | Sport chassis only; not standard suspension |
| E46 (1999-2006) | 323Ci, 325Ci, 330Ci, 325i, 330i, plus Compact and Touring variants | Sport chassis only; early-build dates vary |
| Excluded | E46 xDrive (Xi) models, E46 M3 | Different rear shock and stop arrangement |
Two limitations deserve attention. First, E46 all-wheel-drive Xi cars and the E46 M3 use a different rear shock assembly and are not served by this reference. Second, several early E46 listings carry a production-date cut-off, so a buyer checking by VIN may find that a 2001 or 2002 car built on a certain date takes the other stop. This is exactly the category of detail that ends up in a warranty claim if it is not confirmed before shipment.
This is the single most common ordering error on the E36 and E46 rear axle. BMW used two different rear bump stops depending on the suspension the car was ordered with, and the two are not interchangeable even though they look similar on a workbench.
| OE reference | Application | Practical difference |
|---|---|---|
| 33531138109 | Sport / lowered / M Sport chassis | Shorter effective stack, tuned for reduced static suspension travel |
| 33531136395 | Standard suspension | Longer stack, matched to factory ride height |
The logic is straightforward: a lowered car has less usable travel before the damper bottoms out, so the stop has to begin its progression earlier while still contributing less total height. Fit the standard-suspension stop to a sport car and the rear axle will sit hard on the bumper; fit the sport stop to a standard car and the last part of the travel loses its cushion.
For buyers, the practical instruction is to pull the old stop and read the casting or the last seven digits before pricing. Reverse-lookup by VIN alone is not enough on cars that have been lowered, lifted or converted in service, because the suspension on the car may no longer match what the VIN built.
Rear bump stops are almost never replaced alone in a professional suspension job. The usual companion items are the rear shock dust boot, the rear shock mount and the spring pad at the top of the rear spring. When you quote a rebuild kit, offering the stop, the boot and the mount together reduces the number of purchase orders your customer has to raise and gives them a shorter parts list at the counter.
Original bump stops on these platforms were microcellular foam or rubber. Polyurethane holds its shape longer under repeated compression, keeps more of its progressive rate after years of use, and resists the oil, ozone and road salt exposure that turns old foam stops crumbly. The comparison below is a general material property overview rather than a claim about any specific competitor’s product.
| Property | Polyurethane (PU) | Conventional foam / rubber |
|---|---|---|
| Compression set after long service | Lower — recovers shape better | Higher — tends to flatten and crumble |
| Oil and ozone resistance | Good | Depends on compound |
| Progressive rate retention | Retains over service life | Falls away as the cell structure breaks down |
| Hardness control | Adjustable by formulation | Limited range |
| Typical failure mode | Deformation at extreme overload | Crumbling, splitting, disappearing entirely |
Hardness is the parameter that matters most for ride evaluation, and it is also the parameter buyers most often leave unspecified. If your brand wants a firm feel or a soft feel relative to the original, tell us the target Shore hardness or send an original part for reference — we can match by formulation rather than by guessing.
Most purchase enquiries for this part arrive through one of a few predictable routes. Knowing them helps us quote faster and helps you structure your own product page.
Rear bump stop, jounce bumper, shock absorber buffer and rear axle additional shock absorber all describe the same item. Buyers who search by dimensions — bore, body diameter, overall length — usually already have the old part in hand, so a dimension table on the page converts better than a long product description.
Searching the bare OE number, or its spaced format 33 53 1 138 109, is the fastest route to an exact match. Cross-reference numbers from the aftermarket are useful as a second confirmation, but they should be treated as a search aid rather than a fitment guarantee, because several of them cover more than one chassis variant.
Buyers with a specific car in front of them search by model instead — "E46 330Ci rear bump stop" or "E36 328i rear jounce bumper". These enquiries almost always need a suspension-type question answered first, which is why the sport versus standard split belongs high on the page rather than in a footnote.
Distributors who already stock the number often move to a private-label arrangement once volume is stable. We support custom design and OEM development for this family, including branded packaging, carton artwork and mixed cartons for multi-reference orders. Existing drawings can be matched directly; new variants are developed from a sample or a dimension sheet.
We manufacture this part in polyurethane at our own production facility. Moulds for the 33531138109 profile are already tooled, so sample quantities and pilot batches do not require new tooling investment. Our process controls cover incoming compound inspection, dimensional checks on the bore and body diameter, hardness verification and a compression test on sampled units from each batch.
Production lead time is 15-30 days depending on order quantity and whether custom packaging is required. Standard shipments leave in neutral export packaging; private-label packaging adds artwork approval time, so build that into your first order schedule. For buyers comparing sources, ask about the bore tolerance and the hardness range rather than only the unit price — those two numbers decide whether the part performs like the original or becomes a comeback.
We are happy to review a photograph of the old part or a copy of your drawing before quoting. That usually resolves the sport-versus-standard question in a single message.
No. Both are rear axle bump stops for the E36 and E46 3 Series, but they serve different suspensions. 33531138109 is specified for cars with sport or lowered suspension, while 33531136395 covers cars with standard suspension. They have different effective stack heights and should not be mixed on the same axle.
No. The E46 all-wheel-drive Xi models and the E46 M3 use a different rear shock and stop arrangement, and this reference does not cover them. Confirm fitment against your vehicle identification number as well as the suspension specification before ordering.
Two. The rear axle takes one bump stop on each side, and workshops normally replace them as a pair together with the rear shocks and dust boots, because the labour to access them is the same.
Yes. We can adjust the polyurethane formulation to a target hardness range if your brand needs a different feel from the original, and we produce to customer drawings for new variants. Private-label packaging, carton artwork and mixed cartons for multi-reference orders are all supported, with samples available before volume release.
If you are sourcing this rear bump stop for distribution, a suspension rebuild programme or a private-label line, send us your target quantity, the suspension type, and any cross-reference numbers you are already using. We will come back with pricing, sample lead time and the production schedule.
Browse the wider polyurethane bump stops range for matching references, review the shock absorber parts category for companion items such as dust boots and mounts, or look at our custom parts service if you need a new profile developed to your own drawing.
