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Thread: D2 Std Suspension Rebound Travel Measurement

  1. #1
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    D2 Std Suspension Rebound Travel Measurement

    I have contacted QLD Transport to try and determine the maximum legal lift for a D2 that is classed as a Minor Modification and recieved the following information;

    Thank you for you email enquiry to the Department of Transport and Main Roads regards the lifting of suspensions.

    There are two (2) forms of lifting a 4X4 vehicle from the vehicle manufacturer's specifications. One being a minor modification (suspensions lift) requiring no formal approval and the other being a specific modification, 50mm body lift.

    Minor Modification:- The first being a suspension modification lift and is briefly explained as follows; The depart of Transport and Main Roads (the department) permits the raising or lowering of a vehicle's suspension provided it meets the following requirements. When a vehicle's suspension is raised to increase the ground clearance, a number of components can be affected. Consideration of components such as drive shafts angles, CV shaft angles, and drag link angles and so on need to be considered when performing the modification.

    Raising a vehicle's suspension has the ability to reduce its road handling characteristics due to factors such as increased Centre of gravity, degradation of braking performance and increased body roll. As such, the department policy limits the amount a vehicle's suspension can be raised.

    As suspension types and specifications change with each make and model, the department does not specify a specific amount a vehicle's can be raised (for example, 50mm). Alternatively, the department stipulates a vehicle's rebound travel must not be reduced by more than one third of it's original measurement. The measurement points are; between the rebound rubber and rebound rubber stop (unaltered), or the bump rubber and bump rubber stop (unaltered).

    Can someone please explain what exactly this means?

    I would have thought that the rebound travel is increased in a lift, but I may be way off the mark here.

    Does anyone have the measurements they refer to for a stock height D2?

  2. #2
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    ide say its a typo, i also think if you raise a vehicle via springs the bump stop clearance will increase.

    cheers phil

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    Does it have anything to do with the difference between a live axle and independent suspension? Would I be right and assuming that in a spring lift on an independent suspension the total gross movement between fully compressed and fully extended doesn't change but merely the 'neutral' point when sitting still. Thus the 'rebound' is the movement opposite to the compression?

    If they mean on a live axle also, then I can't follow either.

  4. #4
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    Yep, they dont diferentiate between live axle or independant.

    I can follow it for independant suspenion and the diagram they provided me depicts independant, but does not reflect live axles at all.

    I am going to provide QT with a sketch of the Land Rover suspension setup and ask for the measure points to be pointed out to me.

  5. #5
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    I believe I have part of the answer.

    You can modify your suspension in QLD by up to 1/3rd of factory specifications.

    To measure the allowable height place vehicle on level ground unloaded with standard suspension. Measure the distance from the rubber bump stop on the chassis to the corresponding metal stop on the axle housing.

    Next take the same measurement with the suspension at full drop. The difference between these two measurements is your rebound travel.

    You can now raise the vehicle by up to 1/3rd of this measurement.

    Now would anyone happen to have these measurements or have a stock suspension D2 that they could possibly measure.

  6. #6
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    Quote Originally Posted by CJT View Post
    I have contacted QLD Transport to try and determine the maximum legal lift for a D2 that is classed as a Minor Modification and recieved the following information;

    Thank you for you email enquiry to the Department of Transport and Main Roads regards the lifting of suspensions.

    There are two (2) forms of lifting a 4X4 vehicle from the vehicle manufacturer's specifications. One being a minor modification (suspensions lift) requiring no formal approval and the other being a specific modification, 50mm body lift.

    Minor Modification:- The first being a suspension modification lift and is briefly explained as follows; The depart of Transport and Main Roads (the department) permits the raising or lowering of a vehicle's suspension provided it meets the following requirements. When a vehicle's suspension is raised to increase the ground clearance, a number of components can be affected. Consideration of components such as drive shafts angles, CV shaft angles, and drag link angles and so on need to be considered when performing the modification.

    Raising a vehicle's suspension has the ability to reduce its road handling characteristics due to factors such as increased Centre of gravity, degradation of braking performance and increased body roll. As such, the department policy limits the amount a vehicle's suspension can be raised.

    As suspension types and specifications change with each make and model, the department does not specify a specific amount a vehicle's can be raised (for example, 50mm). Alternatively, the department stipulates a vehicle's rebound travel must not be reduced by more than one third of it's original measurement. The measurement points are; between the rebound rubber and rebound rubber stop (unaltered), or the bump rubber and bump rubber stop (unaltered).

    Can someone please explain what exactly this means?

    I would have thought that the rebound travel is increased in a lift, but I may be way off the mark here.

    Does anyone have the measurements they refer to for a stock height D2?
    Basically they don't have a stated limit you can lift it, however in the case of lowering (rice burners and homeboygangstadoofdoofmobiles) if you lowered the car, you can only reduce it by no more than 1/3 of it's original unladen height.
    It's not specific to height at all, but for lifting as a safety measure an engineering certificate would be required if you want to go 50mm and up.

    Cheers

    Andrew.

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    Quote Originally Posted by Mundy View Post
    Does it have anything to do with the difference between a live axle and independent suspension? Would I be right and assuming that in a spring lift on an independent suspension the total gross movement between fully compressed and fully extended doesn't change but merely the 'neutral' point when sitting still. .
    Same same for a live axle. Lifting won't change travel, merely the at rest position. Often lifting will reduce travel due to stiffer springs.

  8. #8
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    Quote Originally Posted by BigJon View Post
    Same same for a live axle. Lifting won't change travel, merely the at rest position. Often lifting will reduce travel due to stiffer springs.
    BigJon, after more thought about it you are absolutely correct.

    The department of transport look at a suspension lift as springs only to calculate the allowable lift.

    So if you lift the vehicle, keep the standard shock absorbers and therefore reduce the rebound to full suspension drop the vehicle has.

    That is the calculation.
    Last edited by CJT; 12th November 2010 at 01:23 PM. Reason: Spelling

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