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Thread: Mounting height for trailer leaf springs

  1. #1

    Mounting height for trailer leaf springs

    Am going through the process of upgrading the springs, axle and wheels on my box trailer so bit by bit I can convert into a camper trailer.

    One thing I have noticed with cars/utes with rear leaf springs is the front spring hanger is much lower than rear hanger, in a lot of cases the front hanger is in line with the rear axle where as on a trailer the front and rear hangers are in the same plane attached to the trailer rails.

    Can anyone tell me if having the front lower on vehicles is done for a reason other than they just match the curve of the chassis?

    Reason I ask is while looking in to it I found this link http://go.jeep-xj.info/HowtoTrailerPlans1.htm and in it he mentions that it helps the trailer track better. Is there any fact to this??

    Thanks Adam

  2. #2

    Re: Mounting height for trailer leaf springs

    Basically the bigger bonus of higher mounts at the rear of the trailer is you effectively have a greater departure angle meaning you can cross deeper gullies etc without dragging the arse on the bank. That being said though you still have the departure angle of the tow vehicle and the attitude clearance between your trailer and the rear of the vehicle.
    I disagree that it will make it tow any straighter or easier if the trailer is built square to the centreline and suitable lengths between axles are used.

    No matter what design you use there will be an improvement in one area and a deficit in another, there is no magical perfection to be had.

    Workout what entry and exit angles you think would suffice and build around that.
    Jack.

  3. #3

    Re: Mounting height for trailer leaf springs

    Hadn't thought about how it would affect deparure angles etc. too many other variables like mentioned above. I was just curious about the claim of towing straighter while loaded. I am using the same tyres and rims as tow vehicle and keeping the wheel track the same to help when I use it on the sand.

    I still don't know why utes for example have the lower front spring mount???

    Adam

  4. #4

    Re: Mounting height for trailer leaf springs

    As you flatten out a leaf spring under load, the centre point of the spring moves backward.

    This means that if you hit a bump on one side the axle actually turns a bit and can be de-stabilising and start the wobbles.

    By tipping the leaf spring forward it can be neutralised a bit (lower front spring mount).

    When you load up a leaf spring that is "leaning forward" then the rearward movement of the spring centre is compensated by the front mount pivot which is now pivoting the spring centre up and forward a bit on its arc.

    This is hard to explain.

    Darren

  5. #5

    Re: Mounting height for trailer leaf springs

    Thanks, think I understand where you are going. I might space the front spring mount lower than the rear by 50mm and see how it goes.

    Adam

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