Keeping conversion van weight under control

Its easy to get carried away with a van conversion and add all sorts of stuff. But the weight can add up much faster than you think, and soon you could be pushing up against the maximum vehicle weight.

If you’re using a long wheelbase 2500 crew van with a V6 engine and 4×4 transmission like we did, your payload weight isn’t very high at all.

Although 1-1/4 tons sounds like a lot, it soon disappears as you build out cabinets, a bed platform, a fridge, electrical system and some water tanks.

Add in a couple of people, a couple of mountain bikes, and some food, clothes, and water for a week’s getaway and things can get out of hand.

Although Sprinters can carry a lot of weight, they do have an upper limit, Different models have different limits based on chassis length and how strong the rear axle is.

Sprinter Vehicle Identification Placard on driver's seat base
Sprinter Vehicle Identification Placard on driver’s seat base

The weights for your van are shown on the placard on the driver’s seat base. There are several different numbers.

  • GVWR (Gross Vehicle Weight Rating) is how much the van is allowed to weigh.
  • GCWR (Gross Combined Weight Rating) is how much the van and any trailer it’s towing are allowed to weigh in combination.
  • GAWR (Gross Axle Weight Rating) is how much weight is allowed on each axle. It’s different for the front and rear axles. This is to make sure the weight is evenly distributed in the vehicle and that you don’t put too much stress on either axle. You’ll notice that the sum of the front and rear axle permissible weights is higher than the total GVWR. Just because each axle can take slightly more weight doesn’t mean you can add that entire amount to the van.

Weight limits vary by van type

The payload weight (GVWR minus how much your vehicle actually weighs) is how much extra stuff your van can carry. That includes all the junk you’ve added above the empty van weight, and you and your passengers.

  • 144″ Wheelbase 2500 = 3446lbs (~1.5 tons)
  • 170″ Wheelbase 2500 = 3116lbs
  • 170″ Wheelbase Extended 2500 =- 2994lbs
  • 144″ Wheelbase 3500 (dual rear wheels) = 4456 to 5507lbs (~2.5 tons)
  • 170″ Wheelbase 3500 (dual rear wheels) = 4082 to 5133lbs
  • 170″ Wheelbase Extended 3500 (dual rear wheels) = 3916 to 4967lbs

These numbers are just a generic guide. Certain options (crew or passenger van, 4×4, low vs. high roof) change the payload weight limit. For instance, the 6 cylinder 4×4 170″ Wheelbase 2500 crew van has a 2542lbs payload. That’s over 300lbs lost to the extra weight of the engine and drivetrain, and another 250lbs for the 3-person bench seat. The 170″ 2500 V6 passenger van has a 2311lbs payload (~1 ton), mainly because of its extra seats.

Sprinter configuration options with payload shown
Sprinter configuration options with payload shown (mbvans.com configurator)

You can find the theoretical figures for your van on the Sprinter build site. You can find the Mercedes approved payload for your particular vehicle on a sticker on the driver’s door surround (b-pillar).

B-pillar sticker showing actual payload capacity and tire pressures
B-pillar sticker showing actual payload capacity and tire pressures (this will differ from van to van based on build options)

To be really sure, the best thing to do is weigh your van completely empty (but with a full tank), and subtract that weight from your GVWR. That gives you the actual payload capacity for your vehicle.

It’s hardly any surprise that most of the professional upfitters use 3500 vans for their RV conversions.

If you’re driving an RV that was built on a Sprinter platform, the RV manufacturer will have provided another placard that shows the amount of payload weight left over after their conversion. It’s often not much at all. I remember seeing one Class B professional conversion where the payload weight was little more than two marginally overweight adults and their two marginally overweight kids. No extra allowance for personal items, food, clothes, bedding, or the inevitable bikes and barbecue hanging off the back of the rig.

Towing limits

If you’re planning on towing, there’s an important consideration when you’re building out your van. The tongue weight of the trailer on your hitch counts towards your GVWR because it’s weight that rests on the van rather than on the trailer’s axles. That means your payload is reduced by that amount.

Don’t try putting the majority of your load behind the trailer axle to reduce tongue weight – it tends to make the trailer shimmy and handle really badly. Basically, you just have to suck up that additional weight restriction.

The factory hitch is rated at 500lbs tongue weight, 5000lbs trailer weight for the 2500 vehicles and the extended length 170″ wheelbase 3500 vehicles.

The 144″ and regular 170″ wheelbase 3500 vehicles have a 750lbs tongue weight and 7500lbs trailer weight restriction. The 3500 vans have frame rails that are twice as thick as the 2500 vans, with wider flanges to attach them to the body as well. That’s one reason why the vans can carry more weight. The rear axle is solid rather than hollow, and there are four wheels on the axle to spread the load across a larger surface area on the road.

You can’t necessarily use all of the 5000/7500lbs trailer weight. The GCVW is almost always less than the GVWR and the maximum trailer weight. In this situation, if you’ve loaded your van down, you can only fill the trailer up to the additional allowance in the GVCW, not all the way to the maximum trailer weight.

As an example, the 9990lbs GVWR USA-spec 3500 has a GCVW of 15250. If the van was fully loaded (including the trailer tongue weight), then the trailer itself couldn’t weigh more than 5260lbs, even though the upper limit for towing is 7500lbs.

Implications if you are overweight

The weight limit is there for a good reason. The van’s systems – the suspension, steering, brakes, axles, transmission, even the chassis frame members – were all designed with a maximum weight in mind. If you exceed that weight you will be putting extra stress on those components. The brakes may not be able to stop you properly or may overheat. The suspension leafs can get stressed and fail. The transmission will work harder than it should.

Although it’s unlikely you’d ever be caught, you can be fined for driving with an overweight vehicle. It’s possible that if you were in an accident with an overweight van your insurance company could deny your claim, because your vehicle was being used outside its safety tolerances.

From an everyday practical perspective, driving a van that is at or over its weight limit is more stressful. Getting up to speed and slowing down both take longer than you’d hope. The suspension doesn’t iron out bumps in the road so well. Fuel efficiency takes a hit too.

Keeping your conversion within the limits

We found it really hard to stay within our target weight. Even with a spreadsheet of estimated weights, real life ended up heavier.

  • Our cabinets weigh much more than is necessary because they’re made with a combination of 1/2″ and 3/4″ plywood. We also used 1″ thick countertops. 2″x1″ wood framing with 1/4″ skins would have been much lighter. Our plan is to replace the cabinets with frames made from 80/20 aluminum extrusions and 1/4″ panels.
  • Our electrical system was pretty heavy for a lithium install at just under 290lbs (including batteries, inverters, cables, panels, and outlets but not the solar panels). If we’d used lead acid, it could have been closer to 800lbs for the same capacity!
  • We ran a lot of cables around the van. We ran both positive and negative to each outlet rather than using the van chassis as a negative ground. It’s wonderful having 12v and 120v outlets everywhere we want them, but that much copper does weigh something. Less outlets would mean less weight.
  • We added three large solar panels on the roof (126lbs), mounted on roof rack rails (56lbs). If we’d used a smaller solar panel bolted directly to the roof or a second engine alternator instead we might have saved some weight.
  • The thickness of the panels you put on your walls and ceiling is also a big contributor to overall weight, just because of the large area you’re covering. So long as you aren’t planning on attaching heavy items directly to the wall panels, 1/4″ is the maximum thickness you really need. Most people can get away with 1/8″ if it’s being covered with foam and fabric. Some folks even use honeycomb plastics instead of plywood for these panels to keep the weight as minimal as possible.
  • Sound deadening products often work by virtue of their weight. If you line the entire inside of your van with butyl rubber sound dampener like Dynamat or Reckhorn then you’ll probably be adding over 150lbs of weight. It has questionable value in lots of areas of the van, especially if you’re also using Thinsulate as a heat insulating layer because Thinsulate has pretty good sound deadening properties too. When I see people line the entire floor with Dynamat I worry for their overall build weight.
  • We used 3/8″ rubber stall mat as an insulating layer on our floor. It does a good job of noise insulation but not so much for heat insulation. 1/2″ extruded polystyrene or 1″ PolyIso foam panels would give much more heat insulation for a lot less weight, although they’d require a different floor construction technique than we used.
  • We kept the factory bench seat in our conversion. At ~250lbs it’s really heavy. A DIY chest style bench seat would give us more storage space for much less weight. It wouldn’t have the same safety features, but we find we hardly ever carry passengers anyway.
  • Our water tank and battery storage areas had to be built strong because they are structural – the tank and battery are held in place partly by the cabinetry around them. If we’d used a different design and bolted these components directly to the floor, we could have used less cabinetry and made it much lighter.

It’s yet another thing to consider during the design and build of your conversion. If you’re going for a minimalist conversion in a 144″ wheelbase 3500 van then you probably don’t have any worries. If you want a full-on electrical and plumbing system with hydronic heating, a bathroom, a galley, and solar panels on the roof then you’d better start a weight budget right now.

Weighing your van

You can weigh your van at lots of places – truck stops might charge you, but you aren’t looking for a certified weight, just a good idea of whether you are well within your limits or scraping up against the upper end of what’s safe.

if you have a quarry or stone merchant nearby they will almost always let you just drive on to their scale for free (ask first). Or, if your state has freeway weigh stations where the weight display is visible outside the booth you can just drive through when they are closed. Remember that normally you’ll have to drive really slowly over this type of scale and add up the weight from the front axle and the rear axle to get your full vehicle weight.

It’s a great idea to do this when you first get the van and then again at stages through your build-out. The weight adds up quickly. It’s good to keep track of it so you can make adjustments to your design earlier rather than later.

3 Replies to “Keeping conversion van weight under control”

  1. Just for a data point- I weighed my 2016 143″ Crew van with 2wd and 4 cylinder motor right after I bought it and it came out at 5580 lbs with a full tank of gas. That leaves 2970 lbs for theoretical useful load. Thats almost 500 lbs above the advertised empty weight for a cargo van… if the crew van bench seat is 250 lbs that would explain alot of it though.
    I used a local recycling center to weigh mine.

    1. That just goes to show why weighing it yourself is so important – going from the placard weight *should* be accurate, but isn’t always.

      Maybe they left something off your van 🙂

  2. Another quick weighing data point. Weighed my van (2500 170WB cargo) recently at 7720 pounds. It was loaded with bed, bedding, temp cabinets, our whole kitchen pantry, walls, insulation, emergency stuff, chairs, electrical, me, and a load of 8020 for our final cabinet build. (Also have van compass lift, bigger tires, skid plates, onboard air, etc.) We are right on schedule to keep the final build under GVWR, but it will be close when loaded up for a trip. The 3500 would have had no issues, but added extra complications with the dually wheel wells sticking into the cargo space…

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