Corner weight vs axle weights

[booster]

When we made the change from 375ah of wet cells to 440ah of AGM in our 07 Roadtrek 190, the batteries moved from the stock locations which were on the far outer edge of the passenger side, in front of and behind the rear wheel. The AGMs are mounted dead center, right behind the axle.

The batteries and hardware were near 250#. This took nearly 125# off the right rear tire, leaving 125#, and added 125# to the left rear tire. It also changed the front wheel weights as the the right rear went up and the right rear went down, which moved the right front up and the left front down some.

I hadn't really thought about it much until I saw the van sitting on the very flat part of the driveway when we got home yesterday. It had an obvious lean to the driver's side which measured to be at about 1/2" at the wheelwells. The fronts showed a similar, but smaller difference, but reversed. Our wheelwells would normally be within about 1/8" unloaded, so it was different. I also know that when we are even on the wheelwells the front and rear swaybars are unloaded, so with the different heights side to side, both bars would be trying to get it back to level, so the actual out of level would be more than the 1/2". We have always been a bit of the exception, I think, in that we would be level with the airbag pressure the same on both sides, but not any more. It took about 10 psi extra in the drivers side to get back near level, which makes sense. Each bag carries 2500# max at 100 psi, so they are 25 square inches. 25 sq inches X 10# gives the 250# change. The Chevy Roadtreks bias towards the drivers side on weight , I think, pretty bad because of all the stuff on the drivers side, like the kitchen, cabinets, gas tank, and fresh water tank, so the mass of batteries mostly canceled that out when they were on the passenger side. It is worst when we first start out with a full gas tank and full fresh water tank, and nothing in the grey and black tanks on the other side. We don't have the second fresh tank on the passenger side as we removed it.

On our short trip, I thought it felt a bit different to drive, but wrote it off to having not driven it for quite a while, softer tires because it got pretty cold, and lots of wind. It will be interesting to see if I can notice any difference with it back to level, or if it stays a bit different because of the weight move.

It is nice to be able to balance out things with individually adjustable bags. I think we will set them at 15# higher on the driver's side when we have full gas and water and see how it sits, at the next trip.

For anyone who would be close on rear axle weight limits, being that much different side to side could easily put one rear tire over max weight limit and cause problems.

I would guess the only way to get the individual wheel weights would be at one of the weigh stations where they do the weights with the portable scales?

[markopolo]

I'd love to get the corner weights for my van. I sort of recall at least one report here on the forum from someone who got their rear corner weight.

My van needed around 10 PSI more in the drivers side rear suspension air bag to make the van perfectly level when I checked it right after all the suspension changes (rear air suspension, new front coils).

I just went out and checked it today and it is equal height across the rear with equal pressure in the air bags. I had set the pressure a little higher than usual because the van is basically in end of season storage. It must be the sway bar(s) leveling things out as I don't think there's a millimeter difference at the rear wheel well measurements. Tire PSI was set a couple of days ago with rears exactly the same. The only difference from the original measurement is that the rear cargo box has been taken off. That would have contributed a few hundred pounds of load on the rear and a lessening of the load on the front.

Drivers side front is almost 1/4" lower than passenger side front. That is typical of what I've previously seen.

[gregmchugh]

You might be able to connect with this group when they are near where you are sometime to get corner weights...

Weighing Schedule/Locations

[Boxster1971]

Although not as accurate as a portable scale you can get close to individual wheel loads by weighing each axle and then weighing one side to calculate the wheel loads. But the RV weight experts don't think much of this method because most truck stop scales like CAT won't allow you to weigh just one side.
http://www.rvsafety.com/weighing/whe...ition-weighing

I did mine at a moving company near Colonial Airstream in New Jersey. It's the place that Colonial recommended and they were very accommodating since they do a lot of RVs.


Sent from my iPad using Tapatalk

[markopolo]

This - https://www.amazon.com/Sherline-LM-5.../dp/B007REJKXA - looks like it would be accurate enough for getting weights on a camper van.

Looks like the gauge is visible in 50lb increments. You'd have to rotate the gauge and maybe zoom in with a digital camera to capture the weight rather than you being under the van.

Put it on a floor jack and lift each corner. You'd have to position it as close to the hub as possible. I think lifting the outer part of the front lower control arm would give a good result.

I'm not sure if lifting the rear axle out under where the leaf spring is would be 100% accurate but it would show you the difference in weight between driver and passenger side.

The owner manual indicates the PSI gauge is replaceable so a 3000lb gauge (for a Chevy van) might be able to show lesser weight increments, maybe get it to 25lb markings.

[booster]

Originally Posted by markopolo

This - https://www.amazon.com/Sherline-LM-5.../dp/B007REJKXA - looks like it would be accurate enough for getting weights on a camper van.

Looks like the gauge is visible in 50lb increments.

Put it on a floor jack and lift each corner. You'd have to position it as close to the hub as possible. I think lifting the outer part of the front lower control arm would give a good result.

I'm not sure if lifting the rear axle out under where the leaf spring is would be 100% accurate but it would show you the difference in weight between driver and passenger side.

The owner manual indicates the PSI gauge is replaceable so a 3000lb gauge (for a Chevy van) might be able to show lesser weight increments, maybe get it to 25lb markings.

I like that, and not horribly expensive.

I think you could easily make it accurate if you supported the opposite side of the end you were measuring at the same height. The hard part is going to be how high to lift to know you have the weight the same as if it was on the tires.

I wonder if you could put it up on metal ramps that are hollow underneath and lift right at the wheel center?

[markopolo]

Good links from Greg & Boxster also!

The $60 fee seems high at first but then I realized it goes toward supporting RVSEF. It looks like they do a very thorough job. That fee would cover a truck, trailer & tongue weight which all adds up to a fair bit of work.

They'll be at the Florida RV Supershow in January. Post your results if you utilize the service.

[markopolo]

Originally Posted by booster

I like that, and not horribly expensive.

I think you could easily make it accurate if you supported the opposite side of the end you were measuring at the same height. The hard part is going to be how high to lift to know you have the weight the same as if it was on the tires.

I wonder if you could put it up on metal ramps that are hollow underneath and lift right at the wheel center?

Just an idea: The scale height is only 4.5". 3 pieces of flat stacked 2x lumber would also equal 4.5". Drive up on 4 ramps made from flat stacked 2x10. Set brake & chock wheels & jack one wheel at a time to remove & replace ramp with the Sherline scale. Then jack again & remove scale & replace ramp. Repeat 3 more times. Once you know how much the scale compresses then you can compensate for that by putting the matching thickness wood under the Sherline.

Does that seem safe? I edited my post above as you were typing to suggest using digital camera to capture the weight rather than getting under the van.

[booster]

Originally Posted by markopolo

Just an idea: The scale height is only 4.5". 3 pieces of flat stacked 2x lumber would also equal 4.5". Drive up on 4 ramps made from flat stacked 2x10. Set brake & chock wheels & jack one wheel at a time to remove & replace ramp with the Sherline scale. Then jack again & remove scale & replace ramp. Repeat 3 more times. Once you know how much the scale compresses then you can compensate for that by putting the matching thickness wood under the Sherline.

Does that seem safe? I edited my post above as you were typing to suggest using digital camera to capture the weight rather than getting under the van.

I do think that would work and could be made safe. The hardest part is keeping the wheel off the ground from turning, I think. The rear is easy because you can set the parking brake. On the front you might be able just use the service brakes. If the other wheels are on blocks, and the brakes on, if the wheel spun it could only drop the 4.5 inches which probably would not be much worse than an underwear dirtying! I suppose you could also use a floorjack under someplace close like the ball joint in the front and axle in the rear and actually do the lift with that, and then set it onto the jack. Then only the jack could go anywhere as even at max weight, the jack would be maybe 1/4" under the lift point.

[markopolo]

Good point about the front wheel possible spinning - would have to be prepared for and prevent that.

I might get one of those someday. It would be useful for the Travel Trailer also.

[markopolo]

I made a scale using info from these two (and other) sites:

http://www.wichitabuggywhip.com/fire...ptof/ptof.html

Making an Arbor Press Force Gauge

Those sites explain it well.

I'd likely choose a different gauge for my intended use if using the same ram and doing this project again. I might just go ahead buy another gauge with 25 psi or so increments. The reason for that is the multiplier you have to use. The 3000 psi gauge I have has 62.5 psi increments on the dial. The ram cylinder diameter is 43mm and that converts to 2.26 approximately square inches. I have to multiply the gauge reading by 2.26.

I tested it by weighing the travel trailer tongue. The 312.5 (5 x 62.5) psi gauge reading multiplied by 2.26 equals 706.25. That would be 706.25 lbs tongue weight.

home made weigh scale.JPG

The trailer brochure lists the dry hitch weight as 488 lbs. There is a sticker inside the trailer that shows the tongue weight as 560 lbs. That would be dry weight including factory installed options. My assumption is that I need to add approx 50 lbs propane, 50 lbs battery and two thirds of the 80 lbs of gear located in the front storage areas. (It's possible that I have more or less than 80 lbs gear in the front.) I just eyeballed to distance from the axle to the trailer hitch and where the gear is to come up with that 2/3rds figure. There's very little gear stored rear of the axles right now.

My calculation comes out to 713 lbs which is close to the 706 lb home made scale result.

I'll do some more testing to try to confirm the accuracy of this home made scale. With luck maybe I'll meet someone who has a Sherline Trailer Tongue Weight Scale to compare result with this home made unit.

I'll also see if I can use it on the van.

[markopolo]

I used this home made scale on the van yesterday by raising each wheel and then setting if down on the scale. A small square of plywood was in between the tire and the scale. The wheel being measured would have been approx 2.75" higher off the ground than the other three wheels. I don't know if or how that extra height would affect the weight shown.

I noticed that from 500 psi and up there are 10 increments for each additional 500psi so each increment mark would be 50 psi.

Also, if the ram cylinder diameter is 43mm then that converts to approximately 2.25 square inches and not the 2.26 I used previously.

I think the weight it shows is 5% higher than the actual weight if the weights obtained on my previous truck scale visits were accurate.

The results for the passenger side front and the drivers side front were the same.

passenger side front.JPG driver side front.JPG

They both look to show 940 (or so). Multiply 940 x 2.25 = 2115. Two previous visits to the truck scales showed 4020 & 4040 for the front axle. That's why I think the home made scale is approx 5% high.

The good news is that the front corner weights appear to be equal.

In between weighing each rear corner I did a wheel rotation and hadn't set proper tire pressures so I'm not sure if one weight was accurate. I'll re-do the rear after driving around a bit to settle the sway bars and shocks etc. If the weights were accurate then there could be a 300lb difference between sides. On the light side rear, the water tanks (fresh & hot) were empty. They can take 35 gallons which would add 292lbs and help even out the imbalance. I had a full tank of diesel and 3/4 tank of propane on the heavy side.

[booster]

Doing one wheel at a time with a height difference will give an error due to angle that is pretty small (sine of the angle thing), but what will mess you up is if there is a sway bar on that axle, which is going to be transferring force to the other wheel. That may be your 5% high you are reading. The good news is that both sides will see the same transfer, so the side to side balance will be accurate. The sway bar on the other axle will also make difference as it too will be in play with the uneven wheel height.

You might want to set the other wheel on a some boards to get the same height. Doing all 4 wheels on blocks would be most accurate, but just the on the opposite wheel is probably quite good.

[avanti]

I've posted this before, but the following setup is incredibly useful for working under the vehicle:

Lift f.jpg

Lift.jpg

I can raise the vehicle in about one minute, and there is plenty of clearance to work underneath. A set of these would make it very easy to level out the measurements.

It would be really slick to build your setup into one of the ramps.

[markopolo]

I'll try the blocks for sure. It wouldn't be too surprising (as Booster pointed out) to see that 100lbs (5%) over, or some of it, being caused by lifting one end of a sway bar almost three inches.

I'm a fan of wooden ramps also.

[tgregg]

Took me so long to enter my reply while watching TV at the same time, I didn't see others had already posted about the blocks.

Sorry for the extra post.

Originally Posted by markopolo

I used this home made scale on the van yesterday by raising each wheel and then setting if down on the scale. A small square of plywood was in between the tire and the scale. The wheel being measured would have been approx 2.75" higher off the ground than the other three wheels. I don't know if or how that extra height would affect the weight shown.

The extra height will affect the weight because that's one of the ways you calculate the height of the center of gravity in a car. You weigh each wheel when the axle is level and the you raise one wheel and reweigh. The change in weight and the height you raised it can be be used to calculate the height of the center of gravity.

Can you place a 2.75" block under the opposite wheel while you are weighing a wheel?

Blocks under the other 3 wheels would be ideal, but a block under the wheel on the other end of the axle should be accurate enough for your purposes.

[markopolo]

No worries, I've been typing while others were posting many times

I made the two front wheels the same height using blocks while weighing earlier today and that 5% overage disappeared

Both front corners show just a bit under 900 PSI on the gauge so I'll say it was 895 PSI.

passenger front level.JPG driver front level.JPG

895 x 2.25 = 2014 lbs
That's close enough to what I expect to see. The average front axle weight from two truck scale visits was 4,030 lbs and half of that would be 2,015 lbs.

I'd say the home made scale is accurate enough to be a useful item to have. The gauge was purchased at Northern Tool and the 10 ton ram was purchased from Harbor Freight using a 20% discount coupon.

I should get a chance to weigh the rear corners this afternoon.

For weights registering up to 500 PSI on the gauge would you use 62.5 psi or 50 psi increments? (see photo)

home made weigh scale.JPG

[tgregg]

Originally Posted by markopolo

I noticed that from 500 psi and up there are 10 increments for each additional 500psi so each increment mark would be 50 psi.

Do you think the increments below 500psi are also 50 pounds, but the gauge just doesn't read below about 150psi?

Just wondering.

[markopolo]

I think it is all in 50 psi increments now after looking at the Valley Instrument website. Their site shows that the 2000 and 3000 psi gauges graduation - minor is 50 psi. The 1500 psi gauge graduation - minor is 20 psi.

[booster]

Did you have any problems with the front wheel spinning, or was the plywood enough to steady it?