Sprinter 3500 Class C Upgrade Series: Part 4 - Front Struts
87-2657 Front Struts
Welcome back to our Sprinter 3500 Class C upgrade series! So far, we've covered the rear shocks, rear sway bar, and rear trac bar. Now, we'll be moving to the front of the coach to cover our testing of aftermarket front struts.
A strut is essentially the same as a shock absorber, except that it also serves to locate the suspension linkage. The Sprinter chassis uses shock absorbers with leaf springs and a solid axle for the rear suspension, while on the front it has independent suspension with struts and a transverse leaf spring.
We started with the rear suspension on our Sprinter because the rear shocks are quite a bit easier to change out compared with the front struts, and it also felt like the main area that needed help was the rear suspension. The front suspension felt fairly nicely planted with a good ride and decent handling, so it was not an initial priority.
Once we had done the rear shocks, sway bar, and trac bar on our Sprinter, we knew we had to move on to the front suspension to test the available upgrades. We went into the testing a bit unsure of how much difference there would be, given that we only had about 20,000 miles on our front struts and they still felt pretty good... but we had to try and find out for ourselves just how much room for improvement there was.
We started out by installing the 8705-1331 Koni FSD front struts. As far as struts go, those on the front of the Sprinter are actually pretty simple to install. This is because of the transverse front leaf spring used on the Sprinter. Normally a strut suspension will use a coilover design, with a coil spring attached to the strut assembly. If the strut is replaced, either a new spring has to be supplied with the new strut, or the old spring has to be detached from the old strut and attached to the new replacement strut. This process can sometimes be a bit tricky, especially without the proper equipment to safely compress the strut.
The transverse leaf spring used on the Sprinter is not directly attached to the struts and therefore can be left installed when the struts are removed. Without having to deal with removing and reinstalling springs, the strut replacement process is quite a bit easier. Mercedes also did a nice job of making the strut mount accessible from inside the cab of the coach. On some other makes using a front strut setup, the dash has to be partially disassembled in order to get to the top mount, but on the Sprinter it's a fairly quick process to get at the mounts. All in all, it's a 2-3 hour job to replace the struts, with an alignment required afterward.
Once we got the 8705-1331 struts installed, we took our Sprinter back on our test route. We noticed a smoother ride and an improvement in stability, but not a dramatic change. Since our project was really focused on improving the stability of our Sprinter, we knew we needed to try another option. Next on our list to try was the 87-2657 Koni Red adjustable struts.
We pulled the 8705-1331 struts off and before installing the 87-2657 struts, adjusted the rebound damping to its max. Most people would not run the struts this way but we really wanted to see what the Konis were capable of. Since the Konis need to be fully compressed in order to be adjusted and thus would need to be partially removed if we decided to go back and tighten them up, we decided to just go right to the max and then dial them back if they were too stiff.
Right away, we were blown away by how much more stable our Sprinter felt. The front end was much more planted - when we changed directions, it stayed much more level with a significant reduction in dive. It felt almost like we'd put a bigger front sway bar on our coach!
Not only was the coach more nimble on the road, but we also noticed that the irritating rocking sensation was even further reduced. The combination of the SuperSteer SS88-1889 Rear Shocks, SS110 Rear Sway Bar, and Koni 87-2657 Front Struts proved to be a winner, with the rear shocks and front struts complementing each other nicely. Because the front struts are so much farther outboard than the rear shocks, they can really play a significant part in cutting down on that rocking without having to be too stiff over bumps.
We were a bit concerned about what would happen to our ride quality with the front struts at their maximum stiffness. We did notice a bit more of a "grainy" feeling from the pavement up front compared with how smoothly the FSD struts rode, so it was a bit of a tradeoff. However, to us it was worth it because the ride was still very good and the handling dramatically improved.
For anyone with a Sprinter 3500 Class C looking for a dramatic improvement to the front suspension, we would definitely recomment the 87-2657 Koni Adjustable Struts set to 50-75% adjustment or more, depending on the coach owner's preference. For a customer who is looking for the smoothest ride up front possible (especially if they have more miles on their coach and the factory struts are getting more worn), then we would recommend the Koni 8705-1331 FSD struts since they did ride very nicely.
For Sprinter owners interested in getting the adjustable struts as part of a package with the rear shocks and sway bar, we have a couple variations of the SS480 Performance Suspension Package, which can combine them as well as the SS701 Rear Trac Bar.
Take a look at the video below which highlights the improvements made by this combination, including the comparison at the end - the SS88-1889 Rear Shocks, SS110 Rear Sway Bar, and 87-2657 Front Struts combined reduced body roll in our Sprinter by 50% per our measurements in a stationary rocking test!
If you'd like to read more about the Koni adjustable struts for the Sprinter, we'd also encourage you to check out Bruce Smith's article "When 'Seeing Red' Is a Good Thing" in the February 2023 issue of RV Enthusiast Magazine, which we highlighted in a past blog post.
Please check back with us next week as we continue our series! Next, we'll be looking at our SSWCT-001 Sprinter Wheel Centering Tool and how we determined the need for it.
Sprinter Upgrade Series: Part 1 - Rear Shocks
Sprinter Upgrade Series: Part 2 - Rear Sway Bar
Sprinter Upgrade Series: Part 3 - Rear Trac Bar
Sprinter RV Chassis - Better Steering and Handling (Filmed back in 2022, earlier in our testing process)
Sprinter Upgrade Summary Video
Sprinter SS480-3 Before and After Video