Left / right weight distribution considerations for build out?

99sport

Active member
How much left / right imbalance is too much? I am contemplating putting all my built-ins on the driver’s side as this leaves the passenger’s side flexible for motorcycles, moving large objects, etc. Perhaps 800 – 1000 lbs more weight on the drivers half of the vehicle. Is this too much? Anyone else do a similar build? If so, does the van lean?

This is in a 2005 T1N 2500 former FedEx cargo van. Weight is 5400 lbs empty. Cargo capacity empty is about 3,000 before the additions. The rear springs are STIFF! I’m not sure if the FedEx springs are the same as the other T1N cargo vans. Fed Ex vans came with a heavy duty (25mm) sway bar in front and standard (22mm) sway bar in the rear. Van has new Koni shocks.

Built ins would be: electrical system (liFePO4 batteries, inverter, etc - 150lbs), refrigerator (70 lbs plus food), water heater (35 lbs), water (300 lbs), factory diesel tank is unfortunately on the same side (150 lbs), misc cabinets (as lightweight as possible, but weight currently unknown) – all of these would be on the driver’s side.
 

ddunaway

Member
A lot of vans end up like this with more weight on one side.....never seen a leaner. Most people perseverance over it a little though. Fuel is closer to centerline. Maybe move a heavy thing to passenger side. Batteries under passenger seat or something like that....
 

Midwestdrifter

Engineer In Residence
Don't assume that having 1000lbs to the left will result in the left being 1000lbs heavier. Find the center of gravity of the weight/object. Then measure how far it is between the centerline of the vehicle and the wheel. If the center of gravity of the load is half way between the wheel centerline and the vehicle centerline, then 3/4 of the weight is on the near wheel, and 25% of the weight on the far wheel.

Assume the loaded weight is about 2500lbs. Shift that load so its 25% from one wheel centerline, and 75% from the other. The resulting load would be 1875lb on the near wheel, and 625lb on the far wheel (not counting the vehicles curb weight). Its pretty difficult to get a load that asymmetric, as you would need a lot of heavy gear right over the wheel well. More typically you would see something closer to 1500/1000 L/R. While significant, thats not going to be a big deal, as the front axle is still pretty balanced from the factory. On a fully loaded van at about 8,200lbs, thats an imbalance of about 500lbs or less than 10%.
 
Last edited:

99sport

Active member
My CAD sketch suggests the CG of my built-ins is about 24" from the van centerline. Using the math Midwestdrifter suggested above, and assuming the wheel centerlines are 67" apart (76" to outside edge with a 9" tire width), that puts 85% of the built-in load or the left side. Assuming 1000 lbs, which I think is quite a bit more than these items should weigh, that is 850 on the left and 150 on the right or 700 lbs extra on the left - or probably under 10% of the total vehicle weight. I am sure FedEx did much worse things than this to the van in its lifetime. I expect the van would have a higher cornering limit turning left than right, but I am not building a sports car. Hopefully it wont cause a noticeable lean - I will see if I can talk 5 or 6 of my neighbors into climbing in the van and checking what happens with a bubble level.

Attached are some cartoons of the layout I am contemplating.
 

Attachments

Bobnoxious

Made in the USA Qualité Supérieure
Many mysteries can be unraveled here.

https://www.upfitterportal.com/en-us/tech-info/beg

I suspect many never consider center of gravity and weight and balance an issue. But it is!!! But how oh great Bobnoxious? Because of all the newfangled driver assist gadgets. Proper center of gravity, weight and balance will allow steering and braking stabilization algorithms to function optimally. BUT, MORE IMPORTANTLY, PERSERVE SAFE CONTROL OF VEHICLE. So, stay within the build envelope.
 
Last edited:

99sport

Active member
Many mysteries can be unraveled here.

https://www.upfitterportal.com/en-us/tech-info/beg

I suspect many never consider center of gravity and weight and balance an issue. But it is!!! But how oh great Bobnoxious? Because of all the newfangled driver assist gadgets. Proper center of gravity, weight and balance will allow steering and braking stabilization algorithms to function optimally. BUT, MORE IMPORTANTLY, PERSERVE SAFE CONTROL OF VEHICLE. So, stay within the build envelope.
Anyone have the body upfitter guide for the T1N?

The document linked in the post above says the left / right axle weights shall not differ by more than 4% and that the front axle weight shall be at least 25% of the gross vehicle RATING at all times (note that placing weight aft of the rear axle DECREASES the load on the front axle).
 

autostaretx

Erratic Member
Anyone have the body upfitter guide for the T1N?

The document linked in the post above says the left / right axle weights shall not differ by more than 4% and that the front axle weight shall be at least 25% of the gross vehicle RATING at all times (note that placing weight aft of the rear axle DECREASES the load on the front axle).
I would assume those guidelines apply to the T1N as well.

I'm digging thru my archives, and will update this message if i find more, but here's the 2003 as a starter:
View attachment 2003SprinterBodyBuildersHandbook.pdf

Newer editions were better....

update: here's the T1N center-of-gravity calculations guide:
View attachment T1N-Center-of-Gravity-Calculations-MB-BodyBuilderInfoPortal.pdf

--dick (finished archive prowling)
 
Last edited:

Airtime

Active member
I had started my build thread and weight distribution came up. Looking for any threads focused on this topic and found this one. Does anyone know of concrete guidelines other than the limits specified in the BEG? I've run across a number of opinions but not much that is specific.

If I keep within the BEG envelope (which should not be too hard especially if I end up >1000 lbs under my 11,030 GVWR as I expect), then do I really need to worry too much about left/right weight distribution? If so, what other guidelines are there, and why?

Here is what I found in the 2019/2020 BEG.

For x-axis (front to back):

4.1.1 Steerability
"In all load states, the front axle load must represent at least the following proportion of the gross permissible vehicle mass:
  • Up to 4.2 t > 35% of gross vehicle mass
  • Up to 5 t > 30% of gross vehicle mass"
For y-axis (left/right) and z-axis (vertical):

4.1.2 Maximum permissible position of the center of gravity
  • Y-axis: "The maximum wheel load (1/2 the axle load) of the laden vehicle may only be exceeded by 4%."
  • Z-axis: "The overall center of gravity height must not exceed 1300 mm/51.2 in."
And it goes on to say the following (I have not yet tried to look through the MY20 DOG):
"Irrespective of this, the tendency of vehicles to tip over
becomes more likely as the center of gravity height increases.
The ESP® in the new Sprinter is optimized to
reduce the vehicle’s tendency to tip over at overall center
of gravity heights up to approx. 1000 mm/39.4 in.
In this context, it must always be ensured that the vehicles
are fitted with the recommended suspension and
ESP® variants according to MY20 Dealer Ordering
Guide (DOG). This applies in particular to vehicles with an
overall center of gravity higher than 1000 mm/39.4 in. "
 

Kajtek1

2015 long/tall limo RV 2.1l
I used to have bus conversion where left side was about 20% heavier than right one.
Never could weight triple axle, 16 tons coach, but using shop compressor for inflating air bags, I noticed the difference between the pressures it took to lift.
Never did notice difference in handling, but then the old beast was slow and hard cornering never applied.
Sprinters do suffer from high COG, so when I can't avoid putting more weight on driver side, I try to keep it low. Currently I put house battery inside on passenger side, but the under the floor boxes available on ebay catch my attention.
I have electric step on the side, what blocks lot of space under, so I am split between keeping comfortable step, or getting rid of it for more storage space.
 

Airtime

Active member
I looked again at specs for CG in BEG 4.1.2. For my 3500XD, 4% above 1/2 GAWR would be 154 lbs high on one side, and to meet GAWR-Rear, the other side would have to be 154 lbs low. Total side-to-side imbalance of 308 lbs.

That is a bit lower than I would have expected. Maybe Mercedes is specifying that conservatively, allowing for a vehicle fully loaded at GVWR and also top heavy at max vertical CG.

However, at lighter loads, I think the imbalance could be safely higher than that. I don't see any Mercedes specs that limit side-to-side CG at lighter loads, as long as max wheel, axle, and vehicle loads are met.

Here's an example just for illustration. On my rig, if I was 10,000 lbs fully loaded, 1030 lbs under GVWR... I could meet all BEG specs with a loading that had:
Front: 3362 lbs (equal to my Basic Curb Weight-Front)
Rear: 6638 lbs, distributed as follows:
- 4015 lbs on left rear wheel (1/2 GAWR-Rear plus 4%)
- 2623 lbs on right rear wheel (balance of the rear axle total load)

This would be almost 1400 lbs imbalance, but still meet all BEG specs. It might have a little more lean than I would want. I'm pretty sure I'll be below 10k GVW, but I think I'll aim for max 500 lbs imbalance, and try to limit it to 300.

Back to the OP... I think a lot of it depends on how close to full GVWR you are. If you are light, you will have more flexibility. If pushing the limits, then I would keep the imbalance down as needed to meet the max specs for your year and model.
 

99sport

Active member
Thanks everyone for all the good advice. I decided to move the electrical system to the passenger's side, purely for weight distribution reasons - it will be mounted on the wall so will be very far to the right - that is about 150 lbs of equipment. All the other permanently attached equipment will be on the driver's side - I'll weigh it as I go and see where I end up.

Here's an example just for illustration. On my rig, if I was 10,000 lbs fully loaded, 1030 lbs under GVWR... I could meet all BEG specs with a loading that had:
Front: 3362 lbs (equal to my Basic Curb Weight-Front)
Rear: 6638 lbs, distributed as follows:
- 4015 lbs on left rear wheel (1/2 GAWR-Rear plus 4%)
- 2623 lbs on right rear wheel (balance of the rear axle total load)

This would be almost 1400 lbs imbalance, but still meet all BEG specs. It might have a little more lean than I would want. I'm pretty sure I'll be below 10k GVW, but I think I'll aim for max 500 lbs imbalance, and try to limit it to 300.
I'm not following your math here. My math is as follows: 6638 axle weight. Max imbalance = 4%, so left wheel = 6638 * .54 = 3585; right wheel = 6638 * .46 = 3053; so the left right difference is 532 lbs = 3585 - 3053. If you put your imbalanced weight exactly between the front and rear axle lines, you could have the follwing max imbalance and still be within the guidelines: 10,000 * .54 = 5400 lbs, 10,000 * .46 = 4600 lbs; max imbalance = 800 = 5400-4600.
 

Airtime

Active member
I'm not following your math here. My math is as follows: 6638 axle weight. Max imbalance = 4%, so left wheel = 6638 * .54 = 3585; right wheel = 6638 * .46 = 3053; so the left right difference is 532 lbs = 3585 - 3053. If you put your imbalanced weight exactly between the front and rear axle lines, you could have the follwing max imbalance and still be within the guidelines: 10,000 * .54 = 5400 lbs, 10,000 * .46 = 4600 lbs; max imbalance = 800 = 5400-4600.
The BEG says "The maximum wheel load (1/2 the axle load) of the laden vehicle may only be exceeded by 4%." My assumption was that the maximum wheel load would be 1/2 of the GAWR-Rear, which is the maximum axle load. On my van, GAWR-Rear is 7721 lbs. So the math is 1.04 * 7721* 0.5 = 4015 lbs.

I think what the spec says is that the maximum wheel load in the rear cannot be exceeded, just as the GAWR cannot be exceeded. It does not say that the 4% applies at lower wheel loads, only at the maximum wheel load.
 

Top Bottom