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  1. #1
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    Default Trailer with axle to the rear

    This post is more out of curiosity than any thing else.

    Usually a trailer has its axle located roughly in the middle (front to back) which I would assume is usually to do with keeping the centre of gravity in the middle and controlling tow bar weight. I have however seen a hand full of trailers with the axle further back (seems to be the Lynx brand of trailers predominantly). I like the look of a trailer with the axle further back and I have read that it makes for superior towing performance (stability) as well as makes it easier to reverse the trailer due to the longer distance between hitch and axle.

    I am sure the down side to this layout is the centre of gravity will tend to be too far forward increasing the tow bar load to unacceptable levels. I am guessing this is why this layout is scarce.

    So my question is how does the Lynx guys counter this tendency? And why are more people not using this configuration if it is more stable and easier to reverse with?


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  2. #2
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    Default Re: Trailer with axle to the rear

    The trailer axle should only be located where it makes sense in terms of the centre of gravity. Ie slightly forward to ensure there is not a negative towball mass.

    Waterski boats tend to have the axle very far back, only because the engine is the most significant mass and that shifts the COG further back, hence the axle is far back. There is no other reason to move the axle rearwards.

    I am sure the trailer manufactures can give better advice on exact percentages but the physics is clear. By the way, lowball mas cannot exceed 100Kgs in South Africa for static load. I have seen quite a few towbars where this figure is even lower, like 75kgs.

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  4. #3
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    Default Re: Trailer with axle to the rear

    To the best of my knowledge the maximum legally allowed tow ball weight may not exceed 100kg.

    The only way I can think that the Lynx trailer avoid exceeding this is putting a limitation on how much weight you can load in various positions in the trailer - especially the forward compartments?

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  6. #4
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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by CvdN View Post
    To the best of my knowledge the maximum legally allowed tow ball weight may not exceed 100kg.

    The only way I can think that the Lynx trailer avoid exceeding this is putting a limitation on how much weight you can load in various positions in the trailer - especially the forward compartments?
    I suspect that is correctly, but given the clear design compromise this layout entails I was hoping to learn more about the advantages, perhaps from an owner.

    Looking at photos the longer A frame and nose is in use and not empty, so perhaps water tanks and fridge are at the back?

    Thanks for the comment!


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    Default Re: Trailer with axle to the rear

    I was told that these are "high speed" trailers. this was due to the ability of towing these trailers at a higher speed without out the tail wag of a badly loaded trailer
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  9. #6
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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by Commander View Post
    I suspect that is correctly, but given the clear design compromise this layout entails I was hoping to learn more about the advantages, perhaps from an owner.

    Looking at photos the longer A frame and nose is in use and not empty, so perhaps water tanks and fridge are at the back?

    Thanks for the comment!
    Seems most of the trailers with such a layout are short and compact. Maybe it is placed far back so that they could create space to fit a fridge slide and door, or some or other storage space, and for the doors to still clear the fender - without increasing the trailer length or going to smaller wheels/fenders?

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  11. #7
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    Default Re: Trailer with axle to the rear

    It's all about weight distribution.
    If the axle in in the center, it would be very easy to have a "light" front. This then cause the trailer to tow very unstable.
    If you now move the axle further towards the back, this problem can be "fixed".
    Ultimately it is up to the user to ensure that the trailer is correctly packed to that the weight distribution is correct.


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  13. #8
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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by stephenplumb View Post
    There is no other reason to move the axle rearwards.
    Discounting the ball weight for the moment, the further back the axel the better the trailer tows and the more stable it is and the easier it is to reverse.

    Towing my boat is a dream compared to my caravan, and yes I know the wind loading is different.

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  15. #9
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    Default Re: Trailer with axle to the rear

    Agree totally with Wetkit and Andrew although maybe for different reasons.
    Yes it does require careful planning on the load distribution to avoid to heavy or light load on the towball.
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  17. #10
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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by Andrew Leigh View Post
    Discounting the ball weight for the moment, the further back the axel the better the trailer tows and the more stable it is and the easier it is to reverse.

    Towing my boat is a dream compared to my caravan, and yes I know the wind loading is different.
    Totally agree and more so with a dam boat where the axle is very far back.

    Having said that there is a nice youtube vid that shows various axle loading configurations with a little car on a treadmill. It has featured on some other threads here.

    The bottom line is the load should be over the axle as far as practically possible. Moving loads out to the ends, may not affect the COG, but it still affects the handling negatively in terms of dynamics behaviour as large loads are moved out to the extremities excessbivly load the axle/chassis.

    It seems the OP may be referring to having a very long draw bar? I guess this will make things more stable, but it will come at the expense of storage and possibly legal length issues?

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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by Commander View Post
    I suspect that is correctly, but given the clear design compromise this layout entails I was hoping to learn more about the advantages, perhaps from an owner.

    Looking at photos the longer A frame and nose is in use and not empty, so perhaps water tanks and fridge are at the back?

    Thanks for the comment!
    I had a Squaredrop trailer built for me. I copied the Australian Bruder EXP-4 design with the only difference being my wheels are outboard.

    Yes, towball weight is fairly high at about 130kg but it's not a problem for my FJ-Cruiser.

    It does tow very well in high cross winds, passing big trucks, etc. Reversing is also much easier. The only downside is that on a tight and narrow off-road track, the turning is difficult. But I put big wheels on and busy with a secondary airbag system to enable it to go over most things if unavoidable. Name:  IMG_20210630_101615_edit_36492169494430.jpg
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  20. #12
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    Default Re: Trailer with axle to the rear

    Quote Originally Posted by Ubbo View Post
    I had a Squaredrop trailer built for me. I copied the Australian Bruder EXP-4 design with the only difference being my wheels are outboard.

    Yes, towball weight is fairly high at about 130kg but it's not a problem for my FJ-Cruiser.

    It does tow very well in high cross winds, passing big trucks, etc. Reversing is also much easier. The only downside is that on a tight and narrow off-road track, the turning is difficult. But I put big wheels on and busy with a secondary airbag system to enable it to go over most things if unavoidable. Name:  IMG_20210630_101615_edit_36492169494430.jpg
Views: 92
Size:  55.5 KB
    Thanks, something like this is more or less what I was wondering about. I am very familiar with the limitations and requirements for load on the tow ball. What got me wondering about the layout is the fact that it is rare, but not unheard of, which means some designers opt for this design on purpose. My question was to try and understand the reasoning behind such a choice given the known limitations (max weight on the tow bar, the potential for incorrect weight distribution when loading).

    It seems clear from the responses so far that locating the axle further back makes for superior towing performance and easier reversing. I am not sure what the length restrictions are on a trailer, but taking into account how long some double axle car trailers are I doubt one will easily exceed that on a luggage or off road trailer and stay within the weight limitations.

    I guess since designers need to try and make their products at least somewhat idiot proof it may be risky to create a utility or luggage trailer with an axle far back as the risk would be for the tow bar to be completely overloaded without the user necessarily knowing, which may be why we don't see thise trailers in that configuration.

    Where it comes to an off road trailer or mini caravan (as pictured), the weight distribution can be more under the designers control by fixing the interior layout of the trailer, so the axle further back layout can be used for its other advantages.

    Lengthening the draw bar just for the sake of having it long may be too much of a compromise in overall length, but perhaps for long stretches of highway it may be worth it.


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