Mod: Fox Shocks + Hellwig Sway Bar
DETAILS: Fox Shocks + Hellwig Sway Bar
After driving more than 24,000 miles with various suspension upgrade combinations, I now feel that I've found the perfect configuration for my 2018 rig (on a 2016 Sprinter chassis): Hellwig Sway Bar + Agile Tuned Fox 2.5 Rear Shocks (with no Sumo Springs!).
The motorhome drives the best it ever has! I tested it on the dirt roads in Quartzsite, in/out of driveways and gas stations, in Arizona winds on the I-10 as well as with semi-trucks passing at various speeds. The motorhome is stable, the rocking is very controlled and the ride is quieter with less vibrations (compared to with Sumos). I initially kept the blue front Sumos on to isolate my opinion to the changes in the rear — but after 400 miles, I have now removed the front Sumos too. I have driven more than 2,500 miles on what I think is now my final suspension configuration, and I think the ride is even further improved (in terms of comfort, noise and vibration without any downside in wind or in/out of driveways). I drove in very windy conditions on the I-10 freeway passing through Palm Springs, CA and I always felt in control, albeit two hands were definitely on the wheel.
Now, the details. I've driven my RV during the past 18 months with the following rear suspension configurations:
Stock suspension (1,000 miles)
Hellwig sway bar only (5 miles)
Hellwig + black Sumos (18,000 miles)
Hellwig + black Sumos + 2.5 Fox Shocks (1,000 miles)
Hellwig + yellow Sumos + 2.5 Fox Shocks (400 miles)
Hellwig + 2.5 Fox Shocks + no Sumos in rear (400 miles)
Hellwig + 2.5 Fox Shocks + no Sumos front/rear (3,500 miles)
From my perspective, I'm convinced that these tall, heavy rigs need some suspension tweaks before they feel stable at a range of speeds, have controlled rocking entering/exiting a variety of driveways — and before I could feel comfortable with only one hand on the steering wheel at highway speeds.
Most of my driving (as indicated above) has been with the Hellwig + black Sumos on the rear. It was definitely better than stock, but I didn't know how much better it could get until I drove Brad Weinfeld's rig of the same model year (thanks again Brad!). He has the Hellwig + 2.5 Fox Shocks and no Sumos on front or rear. It was quiet and very controlled entering/exiting driveways and while driving on LA freeways.
I eventually upgraded to the 2.5 Fox Shocks, but kept the black sumos. I thought I noticed some change, but it didn't drive like Brad's rig. I thought maybe I needed more resistance, so I upgraded to the yellow rear sumos (keeping the Hellwig and 2.5 Fox Shocks in place).
Only at Quartzsite was I able to "downgrade" to the stock rear bump stops that I had originally thrown away, but Bob Swor rescued some for me from the trash (thanks again Bob!).
Immediately after leaving the campsite at Quartzsite, and driving through the wash, etc., I realized that the new configuration (Hellwig + 2.5 Fox Shocks and no rear sumos) was the feel I was hoping was possible! I drove the dirt roads from the V/N campsite to Route 95 three times (out, in, then out again) and drove the rockiest parts at various speeds each time to test the sway and overall feel.
In the second photo on this post, note the two electronic candles that I have on the back shelf above the J bed. They are just sitting there, and are not stuck, yet they didn't move an inch in the 120 miles I've driven since leaving Quartzsite which included the three trips to/from the campground, going in/out of a gas stations and store, on/off I-10, etc. In the past, the candles would have slid around and/or fallen onto the bed.
Compressing the Shocks by Hand
I tried compressing the 2.5 Fox Shocks before installing. I placed the shock vertically and put all my body weight on it. After a few seconds, by holding all of my weight, it began to compress very, very slowly, though did not accelerate with any momentum. When I let go, it took about 30 seconds to fully extend. I tried the same thing with the stock shock (after it was removed), and it was almost a joke how easily you could compress it with hardly trying. And, similar to the difference in thickness of the stock sway bar vs. Hellwig sway bar, the 2.5 Fox Shocks are impressively large in diameter when comparing them to the stock shocks (sorry, no photo comparison!).
Final Thoughts / My Opinion
I've realized that while sumos certainly help and are definitely preferred over no suspension upgrade, it's my analysis that Sumos can never do what a great shock can do. When installed at the same time as a shock upgrade, they can get in the way because they are the first line of defense, restricting the shock from doing its job. Rear Sumos seem to be a bit of a bandaid, adding suspension in a part of the chassis that wasn't originally designed to dampen the ride. Instead, they connect the axle and chassis in a place that transfers noise and vibration (while of course limiting body roll by adding constant resistance). However, since Sumos are simply resisting weight without any intelligent, dynamic dampening of an offroad-style shock absorber, it makes sense that they don't offer the body roll control of the heavy-duty, custom-tuned shock that Agile Offroad (in partnership with Fox Shocks) has designed for our rigs.
And, of most important note, Sumos don't resist on the way up like a shock does — they seem to act more like a ping-pong spring with high resistance to limit the travel, but they don't actually hold on and slowly release like a high-end shock. Needless to say, I'm a huge fan of my new, smoother, more stable and quieter ride!
Fox Shock Installation
It's relatively easy — I did it myself. The difficulty level is similar to upgrading the sway bar, which isn't hard. You don't need to lift the rig since the shocks are not weight bearing, but you will need a jack to compress the shock once you have the top bolt holding the shock in position. For a video of how to do it, check out the link below.
Please note: the video features a 2500 chassis and a different version of the Fox Shock with different torque settings, but the process is identical.
The correct torque spec for our 3500 chassis is 110 lbs. for both the top and bottom bolts.
Hellwig Sway Bar: https://amzn.to/2HBSPep
2.5 Fox Shocks: https://bit.ly/2RQcMVt
Install video: https://youtu.be/grVpPIJ8zZY?t=146 [see italicized note above]