By Jerry Cole, Technical Advisor
I grappled with the title to this article on rear spring replacement, bouncing back and forth between Spring has Sprung and Feeling so Low but decided on the chosen title because my Mercedes-Benz lost that sagging feeling and it was righteous. That has to be my worst pun yet.
Over the decades, I have had numerous Mercedes-Benz that seemed to sit a little low in the rear end and plowed downward in the back when I accelerated. 114, 115, 116, 123 and 107 chassis Mercedes were all subject to this and I’m sure they’re not alone. The same symptoms plagued with my current 1977 450SL. During our run to Roslyn, a fellow club member pointed out how low my exhaust was to the ground and how he thought it was going to touch the highway. I checked the exhaust, thinking I had broken a mount but everything was in place. It was then that I decided it was time to have a look at those rear springs.
Not wanting to break the bank on a $1,000 car but still wanting good quality, I picked up a pair of rear springs made by a Swedish company called Lesjofors, for just over $40 each. Lesjofors was established in 1675, started manufacturing springs in 1852. I figured they probably had a good handle on the process by now.
Replacing the rear springs is relatively easy with the right tools. A jack, a pair of jack stands some basic hand tools and a very specific spring compressor. Do not attempt to compress the springs without the correct spring compressor. Even with the rear wheels in the air and the springs somewhat relaxed, they still possess a tremendous amount of potential energy that is best learned about in books, not by taking a spring to the face. JTC tools 1801 or equivalent works perfectly. I bought the JTC spring compressor when I was rebuilding a W123 front suspension and it was just icing on the cake that it fits many others, including the R107 450SL.
Replacement of the rear springs is relatively simple. The procedure is similar on many other years and models of Mercedes as it is to the R107. Position the car on jack stands so that the rear wheels are hanging clear of the ground and the rear suspension is relaxed. Locate the top of the rear shocks and remove the retaining nut. I use a set of Vise-Grips on the flattened tip of the shock’s shaft to keep it from spinning while I remove the nut with a gear wrench. This really speeds up the process. Once the nut is removed, make note of how the washers and rubber bushing are positioned on the shaft and remove them. Underneath the car, remove the two retaining bolts at the bottom of the shock and remove the shock.
Select the appropriate diameter spring compressor discs and slide them between the spring coils. One goes very near the top and the other very near the bottom. The disc with the larger diameter center hole goes at the bottom so the compressor shaft can pass through it. Pass the spring compressor through the hole where the shock was and engage it with the top compressor disc. Do not use an impact wrench on the compressor nut. Turn the nut with a ratchet and socket to compress the spring.
Once the spring is compressed, it can be lifted out. Make note of the upper rubber bushing and its orientation. If it is damaged, replace it. Looking at the bushing, it will be obvious where the end of the new spring needs to be. With the compressed spring removed, note that the spring is flat on one end and round on the other. The flat side is the top, so make sure the new one goes in that way.
Carefully remove the compressor from the old spring and install it on the new one in the same way. Install the new spring in the same orientation as the old one was. Rotate it around until it fits neatly in the upper rubber bushing. Slowly release the spring compressor and pay close attention to where your fingers are at all times. The remainder of installation is the reverse of removal. Once back on the ground, the car will appear higher than normal. This will settle out once it has been driven a short distance.
In my case, I gained about 3” of height and the car now sits level. When I accelerate, the downward plunge in the rear end is greatly diminished. The added bonus I didn’t even think about is much less body roll in turns. For less than a hundred bucks and a couple of hours with the right tools, that is a lot of bang for the buck.
I waited until I was finished, but I paired this job with a Tequila Sunrise. Springs… rise... get it? I know; don’t give up my day job.