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Old 04-30-2018, 05:53 PM   #1
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Default Suspension upgrades??

Have you replaced your original equipment Mercedes Benz Sprinter shocks with Koni FSD... or added a sway and track bar for stability?
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Old 04-30-2018, 05:57 PM   #2
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If ever you need more help than the input from this forum, these guys are Sprinter suspension specialists: VanCompass
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Old 05-09-2018, 06:29 PM   #3
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Default Sumo

We decided to do something about the “bottoming”’out of our rear suspension after driving more than 85 miles at 30 mph on a bumpy AZ highway.

The initial options offered not much confidence via forums and reviews along with reasonably high prices. We came across Sumo Springs and had them installed front and rear.

These are one of our best upgrades! It all but eliminated the “bottoming out” and tightened the steering. They are inexpensive and fit exactly. If you’re the least bit
auto mechanic-y, you could likely install these yourself. Detailed instructions were included with both my sets.
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Old 05-09-2018, 07:25 PM   #4
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We decided to do something about the “bottoming”’out of our rear suspension after driving more than 85 miles at 30 mph on a bumpy AZ highway.

The initial options offered not much confidence via forums and reviews along with reasonably high prices. We came across Sumo Springs and had them installed front and rear.

These are one of our best upgrades! It all but eliminated the “bottoming out” and tightened the steering. They are inexpensive and fit exactly. If you’re the least bit
auto mechanic-y, you could likely install these yourself. Detailed instructions were included with both my sets.
Super Steer folks told me to skip the Sumo Springs on my 170 inch wheelbase. Would make it too rough.
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Old 05-09-2018, 08:19 PM   #5
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We have all learned on here that suspension handling and ride are very, very, subjective, so what others like, or vendors recommend are very hard to evaluate unless you ride or drive in a sample.


Sumo springs are very progressive, so how much stiffer you get will be determined by how far they get compressed in the van. For the handling issues you are talking about, as long as you aren't porpoising, it is likely you would not need them. Stiffening the front will increase understeer, which is probably what you are feeling with rear wagging. Understeer is very common in dualies.


The bottoming out in the rear you feel is possibly (likely?) the springs going onto the overload leafs. If this is the case, you will need to go up higher to make sure they don't contact on big bumps (or all bumps). It would probably take 1-2 inches higher and will stiffen the rear end, which lots of folks have not liked in the Sprinters.


Stiffening the rear and adding a big swaybar should help reduce understeer.


Of course, I don't know if anyone knows how stiff the new shocks will be, as Koni usually makes them pretty highly damping, and not multivalved like Bilsteins are.
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Old 05-09-2018, 09:41 PM   #6
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Our PW is an Ascent, not a dually. After the installation of our Sumo Springs we haven’t experienced a single thing you described.

For relatively low cost, we took care of all those issues and more with our Sumo Springs.

As you said though, it is very subjective. Sumos work best for us so far.
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Old 05-09-2018, 11:36 PM   #7
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Quote:
Originally Posted by booster View Post
We have all learned on here that suspension handling and ride are very, very, subjective, so what others like, or vendors recommend are very hard to evaluate unless you ride or drive in a sample.


Sumo springs are very progressive, so how much stiffer you get will be determined by how far they get compressed in the van. For the handling issues you are talking about, as long as you aren't porpoising, it is likely you would not need them. Stiffening the front will increase understeer, which is probably what you are feeling with rear wagging. Understeer is very common in dualies.


The bottoming out in the rear you feel is possibly (likely?) the springs going onto the overload leafs. If this is the case, you will need to go up higher to make sure they don't contact on big bumps (or all bumps). It would probably take 1-2 inches higher and will stiffen the rear end, which lots of folks have not liked in the Sprinters.


Stiffening the rear and adding a big swaybar should help reduce understeer.


Of course, I don't know if anyone knows how stiff the new shocks will be, as Koni usually makes them pretty highly damping, and not multivalved like Bilsteins are.
Thank you for your very complete explanation.....

I had.a 30 minute conversation with the folks at Super Steer....and they listened very carefully to my concerns...

My rig rides remarkably well if you are on level pavement and don't make sudden moves or tight turns...I don't get a lot of bouncing or porpoising as you described.... what I am experiencing is a lot of sway when I make turns and go over uneven surfaces...then the rig does pitch side to side and the cabinets shake pretty violently...

My local RV shop said ...my shocks are bad..I don't think I need to let them go to the point where the entire rig either bottoms out or bounces just driving down the highway.. that's losing control.....my RV shop is very a very well respected family business..and have been around since 1981... And get wonderful reviews from their clients..it takes a month or more just to get an appointment for them to see your rig....in other words.. they have more business than they can handle.....To me, the rig feels a little less responsive than either of my cars....a little like floating..by comparison...

I specifically asked the folks at Super Steer about the Sumo Springs...we had a long talk about it... they said that if I had a Winnebago Navion or some other Class C...they would have definitely recommended it...in my case...NO, they advised against it...

Again, my issues are some up and down motion whenever I go onto uneven pavement along with the pitching side to side and yes, I do have a little shimming in the back behind large big rigs...or when they pass me... Super Steer said the Trac Bar should stabilize the back end and keep it inline stable with the front.....

Apparently, the KONI FSD shocks are considered the best aside from an air suspension... and I'm not investing that into this rig...
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Old 05-09-2018, 11:56 PM   #8
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I just looked up the FSD shocks and they are variable valving. They do it with two separate oil paths through the shock damping area. The talk about frequency of oscillation which is also the same as small vs large as they want to tighten up the shock on big bumps and loosen them on small fast ones. This is very similar to what Bilstein has done for quite a while, but I think they do it with one very special valve setup. We have Bilstein's and they are smoother on little bumps and tighter on large bumps than the OEM Chevy shocks were. If the Koni's do similar, which they should, you should be happy with them for comfort and damping, I think.


The rear sway bar and track bar will certainly settle things down for you as far as sway and oscillations. We haven't heard of a lot of Sprinter issues with rear axle side to side movement, so the need for a track bar is a bit surprising. Some leaf spring vehicles seem to need them, and some don't, it appears, depending on the rigidity and geometry of the rear spring mountings. The moving of the rear axle sideways can cause rear steer, which is what your front steering corrections have to counter. There really isn't much downside to the trackbar besides cost.
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Old 05-10-2018, 01:04 AM   #9
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I just looked up the FSD shocks and they are variable valving. They do it with two separate oil paths through the shock damping area. The talk about frequency of oscillation which is also the same as small vs large as they want to tighten up the shock on big bumps and loosen them on small fast ones. This is very similar to what Bilstein has done for quite a while, but I think they do it with one very special valve setup. We have Bilstein's and they are smoother on little bumps and tighter on large bumps than the OEM Chevy shocks were. If the Koni's do similar, which they should, you should be happy with them for comfort and damping, I think.


The rear sway bar and track bar will certainly settle things down for you as far as sway and oscillations. We haven't heard of a lot of Sprinter issues with rear axle side to side movement, so the need for a track bar is a bit surprising. Some leaf spring vehicles seem to need them, and some don't, it appears, depending on the rigidity and geometry of the rear spring mountings. The moving of the rear axle sideways can cause rear steer, which is what your front steering corrections have to counter. There really isn't much downside to the trackbar besides cost.

Hey Booster, thanks for the additional information... I appreciate it....

On our cross country USA trip last fall, almost 11,000 miles, we encountered a lot of winds and yes, I had to do steering corrections for this, the front end which has the McPherson struts did a pretty good job of keeping the vehicle straight on track.. but, I could definitely feel some rear wiggle and occasionally a shudder...the wind was blowing around 20 to 25 MPH... any higher and would have considered pulling over ...

Again, I pretty surprised that my local RV shop said that it really needed new shocks,. I normally don't even consider this for my cars until 100,000...( Except for my Prius that cupped the tires prematurely and I had to do shocks on that early..). My 2010 Subaru Outback has 85,000 and my mechanic said I don't need shocks for that until at least 100k.....

The parts are around $2,100...and the labor to do all of this is $ 780... Really don't think that's and unreasonable number for all this labor...

Super Steer told me that it will be a substantial improvement, and it will feel like a whole different coach....

While I certainly don't expect it to drive and handle as fast as my Subaru...it should be an improvement especially since I'm planning another USA trip this fall...

Everyone I've talked with says that KONI FSD shocks in this particular case will be the best solution for the RV...I've known about Billstein for years and have a great deal of respect for them.... I'll let you know how it works out...I'm very excited about getting them..less so about the price...if I could have just skipped the whole thing and got another 50,000 miles on the stock Mercedes Benz shocks. ( Make by Sachs)..I would have just done that....

With only 40,000 miles..it seems pretty early.. but , the people at Super Steer explained that Mercedes Benz didn't know that this cargo van would be converted into an RV with extra equipment ( constant weight) of the plumbing, toilet, tanks, generator, kitchen, refrigerator, generator, everything... And the generator sits behind the rear axle.... probably contributes to the tail wagging...in high winds...

It made sense after I thought about it...
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Old 05-10-2018, 01:16 AM   #10
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Originally Posted by rlpack1956 View Post
Our PW is an Ascent, not a dually. After the installation of our Sumo Springs we haven’t experienced a single thing you described.

For relatively low cost, we took care of all those issues and more with our Sumo Springs.

As you said though, it is very subjective. Sumos work best for us so far.

I think it might have something to do with the shorter wheelbase.... your setup is on the 144 inch platform...
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