Parts: Front Control Arm Rubber Bushing

It’s been a while since this series has been updated, we’re slowly finding new parts worth our time on the go. The front lower control arm rubber bushing is a common maintenance part that is embedded in the lower control arm, consists of two smaller bushings and one bigger bushing. Today we’re going to talk about the bigger one, which have a more complex structure and more variations, and are also more vulnerable.

Take the used parts on the Nonna for example, tearing is how it breaks down. The rubber connecting the core and the sidewall will gradually break as the rubber hardens and the control arm bounces. Next, the metal bushing sleeve on the inside will make hard contact with the subframe in the bumps, and the vibration will be transmitted to the subframe, and then part of it will be transmitted to the body and the passengers inside. At the same time, the control arm will have more clearance, allowing other suspension parts connected to this arm to float. This is not only about comfort, but also about basic driving safety.

If you look up the EPC today, the lower control arm rubber bushing is a very general part during the production run of the W 140, meaning you could order the same part for a 1991 car and a 1998 car. However, the part did undergo a documented change as “upgrades”. Mercedes put a lot of effort into the front lower control arm rubber bushing for the 140 during the long development, but it was still not perfect. The result was an upgrade around A096694, following complaints from American consumers about the tyres, from the original solid rubber to hydraulic, which allowed the lower arm to absorb more road bumps to improve tyre flat spot problems, more information can be found here.

In the current EPC, the bigger rubber bushing is not listed separately, but sold as a repair kit together with the two small bushings. The part number valid until A096694 is A1403306007, which refer to the original solid rubber version. The second version is A1403306307 valid until A244502, which was already a hydraulic part, but for some reason it was changed again. The third version, which is the last and currnet version, is A1403308207, valid from A244503 until discontinuation of production. Since the final version is the replacement for the first two versions, the old versions are no longer produced, so only the latest version can be ordered.

If you have a car before A096694, maybe you can’t wait to get new bushings to experience a more perfect car. Or like me, you miss the old parts with frustration. I really want to experience the difference of these parts, but it seems that there is no chance to get factory solid bushings anymore. Therefore, today’s discussion is not about period correctness, which period of the car should be equipped with which rubber bushing to get factory status, we simply don’t have a choice. The topic is to explore the difference between old parts and new parts and the difference between different manufacturers.

First I tried to find relatively original bushings from some old lower control arms, but had no luck, it is a rather fragile part. For example, Nonna is an example in disrepair, all the rubber parts are rotten, it could have been original. But you can be sure that it is not factory installed by the wrong installation direction of the bushing. It could be the second, third, or more. The search for the most original factory parts is still going on, which is more difficult than finding NOS (in fact, most of them are also produced after the end of production). The most original bushing I have is from a 1998 S 320 with about 55,000 km.

After all it is aged and the surface was covered in wax and dirt, so I just read what I could make out. Part number A1403331814 , this is the part number of the big bushing itself, it is not recorded by EPC. The bushings on both sides are mounted at the correct angle, which does not even happen on dealer installations when the older mechanic retires from the dealer. That’s why we believe it is a factory part. A car with 55,000 km may have only experienced factory rubber bushings. Maybe this is the second one, then we are unlucky. By the way, both look strong and have no signs of damage.

Between the core and the outer sleeve there are 4 rubber struts, each at a 90 degree angle. The profile of these struts varies, and 3 of them have inscriptions. They are: #1 BOGE, manufacturer. BOGE is an automotive parts manufacturer that dates back to 1931, and since then they have been developing and producing shock absorbers and rubber-to-metal products. BOGE produced many rubber parts for the W 140, such as the subframe rubber bushings, engine mount. #2 GERMANY, a proud statement. #3 number “24-02”, which seems to be a BOGE part number.

Reference #1, a pair of NOS. Apparently in the past this parts kit included two bushings. The photos were taken a few months ago and they are now on Nonna… First of all this is the nostalgic blue packaging, it is important to emphasize that this repair kit only contains two bigger bushings, not a complete set on one side like the EPC. The part number is also A1403331814, which is also not available in the EPC. Many Mercedes part numbers are hidden and can be ordered even though they cannot be found by the EPC, I will mention this again later.

The NOS part is in its own blue box, there was very little information on the box in that era, I don’t know when it was produced, but it should be before 2003. It has the same part number as our assumed factory part, the same BOGE and Germany stamp. Overall the unknown year NOS looks identical to the factory parts. The rubber is still fresh after all these years. There is a layer of wax on the rubber, not that thick.

Reference #2, the newer set. This one is not that new anymore, the label says it is from 2006. But theoratically it is the same spec as the ones currently offered by Mercedes aftersales. It includes one big bushing and two smaller bushings. Don’t be too concerned about the rust on the smaller bushings, it is normal for this part. To keep them from rusting, they must be treated before installation.

The bigger bushing also looks identical to the earlier versions. Still made by BOGE in GERMANY. This shouldn’t be surprising, since 2006 was 18 years ago…

Reference #3. As another interesting comparison I also ordered genuine new parts from the dealer so we could see what the difference was then and now, as reduced quality is a common complaint today. I cunningly ordered them by the number A1403331814 on the bushings instead of the number on the repair kit, and that worked. The current part number of it is A1403331814 02. The full kit costs twice as much as the single big bushing, and the two small bushings can also be ordered separatel. Forgive me for being a stingy S-Klasse owner, I have a dozen cars crying for service.

New genuine part has no box, oh yeah, cost saved. But there are lots of labels to read. Judging from the appearance alone, this 2023 part is basically the same as the factory part from 1997. Still BOGE, same part number. There are slight differences in details but not enough to be considered different. The wax is thicker, which some people will complain about. No actual test to experience their durability, just static observation looks the same. In this conclusion, if I only have one side of NOS, I don’t mind ordering a new genuine to mix with it.

Next up is the non-factory players. We would love for BOGE as the OEM to retail something that is the same as the genuine parts with their own brand and channels, but for the W 140 this rarely happens. Maybe because there is not enough market, maybe because Mercedes aftermarket does not allow them to do so. I have only come across a few rear subframe rubber bushings from BOGE. So, we move our attention to some non-factory brands in the same order as before.

Reference #4, LEMFÖRDER is considered another Mercedes OEM, and its reputation for rubber parts even surpasses BOGE. Of course I can tell you this is because BOGE barely retails their 140 related products under the BOGE brand, not because LEMFÖRDER is more premium. As we mentioned, BOGE has more rubber presence on the W 140, which is not LEMFÖRDER’s territory. However, LEMFÖRDER also retail their own counterpart, so let’s see how it goes.

It’s not easy to get LEMFÖRDER today, it looks like it’s slowly losing out to the competition, the more affordable red box brands are more favored by parts dealers. This is a not so fresh LEMFÖRDER set, it’s retailed as a repair kit just like the Mercedes aftermarket, LEMFÖRDER part number 11006 01. Wow, the label claims it’s made in Germany. Come to think of it LEMFÖRDER only has Turkish made upper control arms and Malaysian made ball joints now, so that’s impressive.

It still has the factory part number, just missing the star. This means that this LEMFÖRDER part comes from the same production tool as the genuine part. In the past, this happened quite often, there were many opportunities to get factory quality part from the OEM at an affordable price. Now, at least for the W 140, this rarely happens anymore, LEMFÖRDER seems to have stopped retailing this part.

Not so surprising, the LEMFÖRDER box actually contains BOGE. As I said this is not LEMFÖRDER territory, BOGE and LEMFÖRDER merged in 1971, now they both owned by ZF Friedrichshafen. So when ZF decided to retail BOGE, some were passed off as the more reputable LEMFÖRDER. However, now such LEMFÖRDER has also disappeared from the parts dealers’ catalogs, just like the genuine quality LEMFÖRDER ball joints of the past. Now these parts are either transferred to other areas with cheap labor to reproduce them with crude quality, or they are no longer offered by brand LEMFÖRDER. Only by spending twice as much from Mercedes aftersales can you get such quality.

Reference #5, because of our unhpaay experience with the red box febi, it ranks after LEMFÖRDER. We never used such part from febi on our cars, but I consulted with some independent Mercedes shops and parts dealers, installation seems to be no longer a problem. In the past we installed febi on other people’s cars, and a lot of hydraulic fluid was squeezed out when installing. As for effectiveness, they don’t care…Today’s typical 140 owner are used car dealers and beginners, thus cars been sold before the bushing is torn again. All in all, not a long-term ownership, but febi can cope with this period, you can also say it is long-lasting enough…

It has no connection with any of the above factory-related parts, which can be inferred from the price. Although this set does not have any production date, it was just ordered and looks very fresh. We assume that it is the current state of febi. Crafty febi will write “Germany” instead of “made in Germany” on parts that are not made in Germany, so that their address information can be misunderstood by buyers as the place of production. But since this bushing claims to be made in Germany, maybe we should accept it.

It has no connection with any of the above factory-related parts, which can be inferred from the price. Of course, while the shapes may look similar, there are some differences. The next comparison is of the 4 rubber struts, which do have slightly different shapes.

In the last, we have a couple of unknown bushings in our inventory as reference #6, which are a scam giveaway. Sometime in the past we acquired a batch of NOS from dealers, at least I think so, they were in the original old box. When we got the box, we found that in fact only the box was NOS, the parts inside were all replaced with aftermarket ones. This is from a front control arm bushing kit. It does not look like LEMFÖRDER, nor febi, and there is no information except the production date stamp on the rubber. Here it is compared as a inferior to the other models above.

We don’t have any professional dynamic testing conditions, the most we can do is put them into X-ray to see the difference hidden under static. For this purpose, we X-rayed 5 rubber bushings, NOS, Genuine, LEMFÖRDER, febi, and inferior products to see their internal structure.

Since the equipment is quite basic, we can only roughly judge their differences. They are placed at the same angle. The top row is 3 Genuine and similar, from left to right is NOS, Genuine and LEMFÖRDER. Green is alloy, blue is rubber, and orange is liquid. The basic structure is rubber bushing wrapped around metal, and then there is liquid between the rubber and the shell. Three parts are basically the same, of course you can see that the liquid is concentrated in different places, some are on the left and some are on the right. This means that there is not much liquid, and they are low liquidity.

The bottom row is two that are not related to Genuine. On the left is the febi, and on the right is the unknown manufacturer. By comparing the images with the Genuine, febi’s rubber bushing has a smaller diameter. Another visible difference is that there is more liquid inside the febi, and it does not gather at the bottom of the bushing like the Genuine, but seems to fill the entire bushing. It also seems to be more homogeneous and thus more fluid than Genuine. It is difficult to determine whether this is a good or bad, perhaps the febi fills more to prevent some of the liquid from squeezing out during installation. Since liquid cannot be compressed, at least it should not be fullfilled, otherwise there will be no damping. The unknown manufacturer is not composed of solid rubber as I expected, it just has minimal liquid. But its X-ray structure is closer to Genuine, now febi is the most unique among the all five…

We can already say that the new Genuine and LEMFÖRDER are equal to the NOS, and that the febi should be ranked behind them all. What is not yet clear is which one is more worthwhile, and when it comes to worthwhile, we have to talk about cost. Since the three parts in comparison come from different channels and even purchased from different countries, I investigated their prices in the same market to avoid the impact of transportation, tariffs and premiums. After adjustment, my purchase price is $90 for Genuine, $40 for LEMFÖRDER, and $40 for febi. Prices may vary in different markets, but the ratio is relatively fixed.

Genuine is pretty expensive compared to febi. Since it’s not a cosmetically important part, maybe you can offset the short life with the price advantage. Genuine can at least exchange 2 sets of febi without considering labor and time. But the ride quality of febi is unlikely to be close to genuine, so whether it’s worth it is entirely up to the owner. To be fair, due to the premium of Mercedes aftermarket, the retail price of OEM versions is usually half or less of the Mercedes price. Then the actual value of BOGE is not more than $50, and not much higher than febi, but hopefully their quality is also close.

It must be emphasized that the design of rubber parts must take more factors into consideration because it is an elastic part. It is not a ball joint or drag link like the metal majority. That is why it is so important that it is considered to improve the weakness of the tire. This is also why it is so difficult that Mercedes still did not get the best answer in one go after years of testing and had to improve it twice. If you look up the development methods of some parts manufacturers, the design of rubber bushings is more semi-empirical, and manufacturers who have not done OEM cannot obtain Mercedes’ design data. They first test the stiffness of factory parts, including radial, axial, torsion, and swing stiffness. Then they look for similar existing products in the database for modification.

This borrowing and following method is very dependent on engineering experience, and it is generally difficult to ensure that all directional stiffnesses are consistent with the target. You can only hope that febi is dedicated enough, or that they have a way to get Mercedes’ manufacturing information. But from what the X-rays showed, they seem don’t. At the same time, the fluid could be squeezed out during installation, and the amount of squeezed out will also affect the performance to some extent, which can only be checked by continuing X-ray after installation. In other words, if it were not for the subframe with rubber bushings to filter the vibration from the front suspension again, the difference between different lower control arm rubber bushings would be more obvious. At this point, do you think Genuine deserves its name?

Please note that all brand new parts are purchased in recent times (2024), they represent the current status of these manufacturers only and do not imply anything about the past or distant future.