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Thread: 30 mm bump stop gap on a 110 - Why?

  1. #1
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    30 mm bump stop gap on a 110 - Why?

    Good afternoon,

    I recently installed 2" longer Terrafirma heavy duty springs and shocks (given to me by a generous mate) to my 1984 V8 110. The springs and shocks had done only 20,000km.

    To suit the 2" longer shocks i spaced the bump stops down 2" (the total length of the bump stop is now about 110 mm when measured from the chassis rail). My front bump stop gap is now only 30 mm (45 mm at the highest point due to the roll of the axle). This is with a 55 kg steel bull bar. The front bottoms out fairly often.

    Does anybody know why the bump stop gap is so low? My initial thought is sagged springs, but the springs are only newish.

    The length from the centre of the hub to bottom of the flare is 520 mm. Does this seem about right for a 2" lifted 110? The springs definitely feel heavy duty - the front is very firm! (Or is this due to the shocks? They felt very firm when i tested them off the truck). I cannot remember the free length of the springs, but they have 5.5 turns and are 15.2 mm thick.

    If it helps, the rear bump stop gap is 75 mm.

    For a cheap fix i'm tempted to remove the 2" spacers from the bump stops and put some new original shocks that i have in the front.

    Thank you,

    Edward

  2. #2
    Tombie Guest
    Why space the bump stop for a 2" lift?
    That's where you've gone wrong!!!

    And TF springs are pretty ordinary at the best of times.

    A 2" longer shock is safe with standard mounts. Not sure why you've done what you have..

  3. #3
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    Thanks for your reply Tombie.

    I hope i have made a mistake! It would be easy to fix!

    The closed length of the standard LR front shock is 330 mm (550 mm open). The closed length of the Terrafirma shock is 50 mm more at 380 mm (600 mm open). So don't the bump stops need to be extended 50 mm to prevent the TF shock from bottoming out on compression?

    Edward

  4. #4
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    The TF springs had probably started to sag as soon as they left the factory.

    Your mate gave them to you as he wouldn't be able to look you in the eye if he sold it to you. What was the reason for your mate to only use them for 20,000Km and then get rid?
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  5. #5
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    His intentions were good. The set up was too firm for him (the fronts especially) and they caused problems with the driveline angles on his Puma.

    Edward

  6. #6
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    I suspect the wieght of the motor and accessories is making a difference.
    Your V8 vs a puma motor(dura-what's it).
    Does the front look like it's been lifted or heavily nose down when you stand back?

    I'm with Tombie, remove the bumps stops to give you close to the same gap as the rear.
    Do you remember what the gap was with original suspension?
    30mm is simply not enough.
    It may be worth dropping the lower shock mount and measuring the 50mm of length is available on compression within the shocker.
    As side note I've only seen bump stops extended on 70mm+lifts subject to spring rates and shocker choice.
    Cheers, Kyle



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  7. #7
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    You have the numbers you need.
    Your new dampers have a closed length of 380mm so take a tape and measure the distance that the damper is at static height. Subtract 380 from that and you have your clearance to crash. Optimise your bump clearance to match crash clearance taking into account that you will get 20mm ish of bump compression on the big hits.

    If after doing these measurements you are not happy with your clearances well then you need longer springs or higher rate springs?

    S

  8. #8
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    Quote Originally Posted by alien View Post
    I suspect the wieght of the motor and accessories is making a difference.
    Your V8 vs a puma motor(dura-what's it).
    Does the front look like it's been lifted or heavily nose down when you stand back?

    I'm with Tombie, remove the bumps stops to give you close to the same gap as the rear.
    Do you remember what the gap was with original suspension?
    30mm is simply not enough.
    It may be worth dropping the lower shock mount and measuring the 50mm of length is available on compression within the shocker.
    As side note I've only seen bump stops extended on 70mm+lifts subject to spring rates and shocker choice.
    Thanks for the tips alien.

    The front has just a slight nose-down look - what i'd consider normal. I measured all the hub to flare heights and the truck is sitting nice and even.

    Edward

  9. #9
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    Quote Originally Posted by roverrescue View Post
    You have the numbers you need.
    Your new dampers have a closed length of 380mm so take a tape and measure the distance that the damper is at static height. Subtract 380 from that and you have your clearance to crash. Optimise your bump clearance to match crash clearance taking into account that you will get 20mm ish of bump compression on the big hits.

    If after doing these measurements you are not happy with your clearances well then you need longer springs or higher rate springs?

    S
    Thanks for the tip roverrescue. It seems so straightforward now that you say it. I'll measure it up and report back.

    Edward

  10. #10
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    Good evening all,

    I just remembered i never reported back to this thread.

    I did all the measurements suggested by roverrescue. It seemed that the bump stops DID have to be spaced down, but by only 20 mm or so (not 50 mm as i had first done). I also have since learned that terrafirma bump stops suited to 2" lifts are only 1" longer, so i guess the measurements are about right.

    Edward

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