Rough Rear Suspension - 3500 RB Sprinter, Sportsmobile

[Chance]

Originally Posted by TeeHouse

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We did get a response from Peter at SMB West that the suspension might loosen over time. We will be visiting SMB in the next week or so for a couple of punch list items and to discuss the rear suspension. We had the van's rear suspension inspected by MBZ Long Beach. Their input was that there is no problem with the suspension. Their conclusion was that the 3500 was designed for a heavy load & that the Sportsmobile build-out was not heavy enough, thus the stiff/rough ride.
They suggested replacing the 3500 leaf springs with the 2500 leaf springs. This would change the GVWR of the vehicle to that of a 2500 but would result in a softer ride. The change, according to MBZ, would not invalidate any MBZ warranty, excluding the leaf spring swap.

Have you weighed the van's front and rear axles separately and compared to maximum factory axle ratings? It sounds to me like Mercedes may be on to something.

I don't own a Sprinter but frequently ride in one from the airport to offsite parking. When the van is not full and we end up sitting at the rear the ride is horrible. The suspension is way too stiff when there are only a hand full of passengers, and also, the one-ton 3500 Sprinters have dual rear wheels which add to unsprung weight. When the van goes over bumps the massive unsprung axle weight leads to passengers coming off seats. Even when there are 10 or so passengers with luggage the short ride is still very uncomfortable.

I'm guessing that if you went to a smaller RB van the weight might be lower than most full-size Sprinter conversions. If that's the case and you have a 3500 model the weight may not be enough to load the suspension enough to soften the ride. And for what it's worth, I seriously doubt that springs will "soften" over time. Even if steel springs sag over time, their stiffness doesn't change; not appreciably anyway.

If you haven't weighed the van yet I'd start there. And if you have, I'd like to hear what you discovered. Shocks and other upgrades may help some, but it's hard to overcome a vehicle which is sprung too stiff.

[TeeHouse]

Chance: Thanks for your response & comments. We would have responded sooner but wanted to get the van weighed first. Our 3500 dually has a GVWR of 9,908# (the 2500 is 8550#). With 2 of us in the van & 20 gal. H20 tank (located in the rear under the couch) full, the van weighed 8,160# (fluctuated btwn. 8160 & 8,180) front axle at 3,740 & rear at 4,440. We agree that any appreciable softening of the springs over time is wishful thinking. We are off to SMB next week. Hopefully, they will have a solution, but not sure. Thanks again - any further suggestions would be appreciated.
John

[windguy]

Teehouse,

Curious to see what your build looks like. Maybe you can share with us your floor plan.
Your van weighs about a weekends worth of beer short of the GVWR of the 2500. About 390 pounds, which isn't much margin if you had gone with that model instead of the 3500. Surprised to see that.
Any idea what the van weighed before you did your build?

On a positive note, your weight is distributed evenly between the two axles.
How about side to side weight distribution?

Sorry to hear you're having ride comfort issues.
Hope you can sort that out without too much effort.

Best of luck!

[Chance]

Originally Posted by TeeHouse

Chance: Thanks for your response & comments. We would have responded sooner but wanted to get the van weighed first. Our 3500 dually has a GVWR of 9,908# (the 2500 is 8550#). With 2 of us in the van & 20 gal. H20 tank (located in the rear under the couch) full, the van weighed 8,160# (fluctuated btwn. 8160 & 8,180) front axle at 3,740 & rear at 4,440. We agree that any appreciable softening of the springs over time is wishful thinking. We are off to SMB next week. Hopefully, they will have a solution, but not sure. Thanks again - any further suggestions would be appreciated.
John

I can't quickly find the front axle weight rating or rear axle weight rating for your van. It should be on driver door. That will allow comparing relative weights; design versus actual.

My guess is that your front end is fairly loaded down compared to maximum design weight. The rear probably not as much.

[TeeHouse]

Windguy, thanks for your input & well wishes. Sorry for the tardy reply. We've been on the road. As for the layout/floor plan: The build is a SMB modified RB153s (similar to Chumley's). Rear couch/bed. Driver side (hers) w/ottoman 70". Passenger side (his) w/ottoman 77". Driver side: TV, bath w/shower & porta-potti, refrigerator (Isotherm100) cabinet (behind driver's seat) w/microwave & storage. Passenger side: Galley w/sink (no cooktop) - flip up counters each end. Upper storage all around. No propane. D-5 system (in passenger side ottoman) for hot H20 & furnace, both work great! Roof A/C w/heat element (Nice!) Fantastic Fan attic fan - wouldn't be without it. Twenty gallon H20 tank & Magnum Inverter under couch. We had quite a bit of soundproofing ("roadkill") installed on floor, dual wheel wells, van side walls & roof. One AGM battery under van & 2 gray tanks (one on each side). No awning. Tow hitch. And, by the way, I don't know the weight of the van before the build. I'd post pix but don't know how to!

Chance, Checked the weight ratings posted on the van door. GAWR for front axle = 4,080. GAWR for rear axle = 7,060. Posted GVWR is 9,990 (I incorrectly posted GVWR as 9,908). Weights we got at the scales - front axle = 3,740. rear axle = 4,440. Total weight = 8,180. Looks like we can load another 1,800 lbs. on the rear axle.

[Chance]

Originally Posted by TeeHouse

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Chance, Checked the weight ratings posted on the van door. GAWR for front axle = 4,080. GAWR for rear axle = 7,060. Posted GVWR is 9,990 (I incorrectly posted GVWR as 9,908). Weights we got at the scales - front axle = 3,740. rear axle = 4,440. Total weight = 8,180. Looks like we can load another 1,800 lbs. on the rear axle.

From the standpoint of rear axle only which is what drives the harsh ride at rear, you could add another 2,600 pounds at back. And when you also consider springs don't have to support axle and dually-tire weight which rests on road, it shows your rear springs are "almost" twice stiffer than needed.

Unless you are planning on heavy loads and towing, it seems a 2500 Sprinter would have been capable of your present load. Wish I had an answer that was viable.

[Chance]

P.S. -- By comparison a Ford SRW axle on E-350 is rated just above 6,000 pounds. Your dilemma is one reason I think Mercedes should offer Super Single 1-ton rear axle in US market. I expect it must ride better than DRW rear axles.

[windguy]

Teehouse,

Your build sounds very nice. Lots of great amenities.

Regarding how to add an attachment (pictures, floorplan, any file), see the attached pic for help.
Follow the numbers and it's as easy as 1,2,3,4,5.
Step 1 - Select Browse and find the file you want to attach and select Open
Step 2 - Add a File Comment if you want, which is optional
Step 3 - Select Add the File
Step 4 - Select Preview so you can see the file and your post
There are some limitations on file size (has to be less than 900 x 900 pixels)
so you might get an error message for certain files that you upload.
Step 5 - Select Submit to complete your post. Done!

Cheers!

[TeeHouse]

When I saw the recent post on "My SMB Sprinter Van conversion experience (Chumley)" by Onefin (Dave) on 7/29/14, it reminded me that I had forgotten to report back on our 3500 RB Sprinter rough rear ride (suspension).

We found improvement. Deaver Suspension (902 Second Street, Santa Ana, CA. 92701. Contact: Jeff Crosby (714) 542-2898) replaced the 3rd leaf spring down from the top (bottom one) with a thinner one with a more progressive arch. The ride is much improved. Deaver has a great reputation.

Has anyone else found improvement? Chumley with the adjustable shocks and/or? Anyone else?

Teehouse (8/1/4) - John

[BajaSportsmobile]

I built some custom valved FOX shocks for a customer's 3500 extended hightop with full build out. Made a remarkable difference over the replaced Koni shocks.

Owner posts here and may want to comment.