# Rear Overhang Point



## ob1

I understand the relationship between payload, rear axle load and vehicle overhang. However if there was a significant fixed extension out from the rear of the vehicle to the coupling to which the load was attached does the coupling become the overhang rear point, or is it still the fixing point of the extension at the body end. I am favouring the former but would appreciate a definitive answer from the tech heads.


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## inkey-2008

The overhang is measured from the center of the rear wheels to farthest point from it.

Andy


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## ob1

Thanks Andy - that's what you call definite!


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## speedytincan

As Andy said overhang is measured from centre of the rear axle to the rearmost fixed part of the vehicle, and if my memory serves me well must not exceed 60% of the vehicles wheelbase. If it were a tandem axle it would be the centre of the two rear axles.


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## ob1

Thanks speedytincan. Actually the 60% rule has been superseded, now the overhang is governed by the vehicle turning circle - in basic terms. The 60% is still a good guide although I wouldn't fancy that much.


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## shirlsian

*rear overhang*

Hi just thought i would clarify what speedytincan said. On a commercial vehicle when measuring wheelbase on a rear tandem axle the measurement is taken from the centre of the front axle to the centre of the two rear axles plus 100mm to the rear


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## 747

ob1 said:


> Thanks speedytincan. Actually the 60% rule has been superseded, now the overhang is governed by the vehicle turning circle - in basic terms. The 60% is still a good guide although I wouldn't fancy that much.


I think it certainly has nowadays. I saw a new Elddis van, the 155 (I think). The rear overhang was not much less than the wheelbase. What it would handle like if slightly overloaded worried me a bit, I certainly would not like to drive one.


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## pneumatician

Think you have adequate answers. But if you go back to your physics its all about moments and on a Camper you have two fulcrums. The front axle and the rear axle. Increasing the load on the rear will rotate about the rear axle (force * Distance) increasing rear axle load and reduce the front axle load.
We all worry about rear axles but forget there is also a minimum front axle loading. 
Light steering going down the Alps can be embarrasing if not down right dangerous.

Dave Burley has the proper formula somewhere.

Steve


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## sparky20006

My overhang is measured from the belt buckle to the point at which my toes appear from above.


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## inkey-2008

You can see your toes????.

Not to much overhang then.

Andy :lol: :lol: :lol: :lol: :lol:


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## pneumatician

Retractable undercarriages were a much later development (evolution) than fixed. Giving the Fuzelage/body much improved efficiency when passing through a fluid yet just as effective when lowered/extended.

Thats my reasoning any road up.

Steve


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