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Contents: 1. Calculating Load on the Back of a Motorhome 2. Vehicle Weight Calculations 3. Load Compensating Valve
While in Spain during the summer of 2002. I met Dieter from Germany. We got talking about loads on the back of Motorhomes. He showed me a German book which had a description and illustration on the German way to calculate loads on the back wall.
For example using my Motorhome measurments;
my 'Omni,' 2 bike rack weighs 5Kgs.
Each bike weighs 20kgs, + 5kg = 45Kgs total hanging on the back wall.
r = 340Cms
a = 530Cms
G = 45Kgs
H = 45 X 530 = 70.15
340So according to Dieter's German handbook the theoretical weight effect on the back axle is just over 70Kgs, this is a calculated excess of 15Kgs to the actual weight!
Vehicle weights are not normally considered by the Motorhome owner, after all who has considered their car weight!
It is very important to consider the weight factor. As many motorhomes during conversion from a van chassis to a motorhome gain a lot of weight.
It has been known for a motorhome after conversion by a coachbuilder to be at it's maximum carrying weight before passengers and luggage have been installed!
This is not only against the law but can be dangerous for the running of the vehicle. Tyres are stressed and can blow out.
The only way to assess the weight is of course to go to a local weighbridge and carry out a weight check and obtain a certificate.
Weigh the whole vehicle, and then with one axle off the weighbridge. Take the lower weight from the whole weight and you get the weight on the other axle.
Example;
Whole weight: 2820Kgs
Front axle on the weighbridge: 1180kgs
This is the weight of the load on the rear axle: 1640KgsWhen I weighed the rear axle it was; 1620kgs.
The above are the exact weights which I took after returning from out continental tour in Sept. 2005. It would appear I was overloaded on the rear axle. Perhaps all the presents, bottles of wine and slabs of lager could be the cause.
Normally one should add the passengers and fully filled fuel tank.
So Partner = 70 kgs, fully filled tank = 80kgs. These would be added to the front loading. 150kg plus 1180kgs = 1330Kgs, within the plate weight.
The weight plate found under the engine front bonnet catch reads:
Max: 3100kg, Rear 1500kg, front 1500kg.
So it would appear we were overloaded on the rear axle by 150kgs.
Having said all that, the weighbridge attendant told me, he did not think that the off axles weights would be correct as the weighbridge was calibrated for an even all wheels on central position. Which, perhaps, would accommodate the seemingly excessively 140kgs on the rear axle.
The answer is to find a weighbridge that will weigh in the manner required, i.e. front, overall, and rear axles.
This information is attributed to George & Val Collings, "Interchange" fame as seen in the Motorcaravan Motorhome Monthly Magazine, Nov. 2005 in the U.K.
I came upon some information regarding travelling in France:
Motorhome MAW
French policy Maximum weight must be within 5%
In my case my MAW is 3100Kgs
3100 X 5% = 155kgs
3100 - 155 = 2945
Therefore my Maximum travelling weight must be 2945Kgs.
The above information, 'Back Axle Load,' so what!
This was calculated by an German engineer who felt that weighing the back wheels on a weighbridge was not satisfactory.
Extra weight on the back wheels have an effect on the steering, also front wheel drive by lifting the front end. As I found to my cost in France. It had rained the week previously. I reversed on to the grass pitch, immediately I sank in and was not able to drive forward, even though the front wheels were on the hard surface of the approach road.
The effect of loading can be seen on many Motorhomes as they travel on the Motorways. The front wheel arch has quite a space above the front wheels and the back end is down on the springs.
This back loading affects braking and is taken care of by the "Load Compensating Valve" located near the back axle. This LCV controls the brake fluid pressure, normally to the back brakes. The LCV controls amongst other things, the locking of rear wheels during braking.
On the Wanderer, based on the Peugeot Boxer van, the "Load Compensating Valve can be seen in the images below.
Click icons for larger image.
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Rear view of the Load compensating Valve |
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Additions to Motorhome pages 2010:-
