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Suspension Seat Mod for Tall People

Discussion in '70-Series Tech' started by zuker81, Oct 5, 2017.

  1. zuker81

    zuker81

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    Hey folks… the first thing I noticed when I originally test drove my HZJ73 was how cramped my 6’4” frame was with the seat all the way back. Being a manual didn’t help as you often have two feet on the pedals and don’t get to stretch out. I asked around the local LC shop about people having modified theirs but didn’t get any definitive info so I decided to give it a shot together with a relative of mine.


    Before starting I made sure to grease and lubricate every possible pivot point on the suspension seat because some squeaks had cropped up, including the inside of the rails. The black paint had chipped or rusted in some spots so a little rust-oleum finish was in order. The worst rust was the surface of the springs, which I thought would look way better with black semi-gloss anyway. It will all be more exposed after the mod. Make sure not to get any paint on the damper shaft.

    IMG_2760.jpg.jpg
    (^Passenger seat, slightly different than driver’s)

    The easiest way I could find to move the seat backward was to add a longer base onto the sliding rails for the seat to bolt into. Those of you adept at welding or metal purists might frown on the solution of wood, but this is 1 full inch of Brazilian walnut which is exceptionally strong, possibly stronger than the thin metal in the existing rails. It also took a matter of minutes to cut, sand, drill and route the wood.

    IMG_0053.jpg.jpg


    I chose 2.5” additional rearward movement just for long trips. Add to that 1” of height for the now elderly and sagging damper and things are looking up. The new inside rail is 2” wide, and the outside rail I think was 2.5 or 3”. This is to add extra strength since one of the levers is attached to the metal rails and requires routing a couple millimeters for the wood to sit flush.

    IMG_0057.jpg.jpg

    Each new rail will need 4 holes for the M8 bolts, two for bolting to the metal rail, and two for the new position the seat will be bolted to. Keep in mind if your rails are flush to the originals, the forward (toward steering wheel) hole for the seat on each side will need to be in-set so the bolt head doesn’t stick out. I recommend space a washer in there too if using wood. Wallow out one of the holes for the seat side because inevitably your measurement is just slightly off.

    I used all new hardware for the bolts, washers, lock washers and nuts as they all need new length. Measure before buying bolts because the chair doesn't allow an infinite amount of thread to stick our beyond the weld nuts. I decided to add some washers in between the the seat and the wood to add a little more ride height, so that added length to the bolts as well. I offset the front to bring the seat up under my knees more, which all my tall comrades will understand.

    IMG_0050.jpg.jpg

    Bolting everything back together is a bit of a farce, but everything should line up. It’s easier to attach it all back to the base without the small spring connected (the one that helps the seat slide forward) then use some pliers to connect it back after.

    Installed @ Full Extension:
    IMG_0063.jpg.jpg

    I ended up liking the increased ride height and tilt of the seat base so much that I added washers to the passenger side too.

    Note: I’ve noticed that the seat belt does not give slack as easily with the seat higher as it did in the original position. This means on big bumps you feel the belt tighten against your waist more than before. Still troubleshooting this but I know there is a way to fix. Let me know if anyone has any clues.
     
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  2. roscoFJ73

    roscoFJ73

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    Adding height is the easiest way to get more legroom. I got a friend to make a up a cushion from the densest foam. Its 100mm thick but when I sit on it ,it crushes down to about 2 inches
     
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  3. RhinoRig

    RhinoRig

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    Dude. Awesome. I've been sucking it up, but no longer. Thanks.
     
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  4. divemedic

    divemedic

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    the wood should be adequate baring freek accidents. That said, you should consider what an insurance adjust will think in the aftermath of plausible accident. Both the car insurance and the health insurance. Lastly the "thin metal" will bend not fracture from too much force. Just my $.02. It's sexy, but just because you can doesn't mean you should.
     
    Last edited: Oct 6, 2017
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  5. Billyfj7312ht

    Billyfj7312ht

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    I haven't sat in my car for long periods of time but was worried the seats might be too high with suspension bases. So knowing a guy over 6 foot can add 2" to the height and not hit the roof is great news. Thanks for sharing. On the timber thing (I'm a joiner and prefer working with timber too) you will need to be careful your weight,vibration and the pressure of tight bolts doesn't compress the timber after a few trips (only needs 1mm) and the bolts will vibrate loose. Maybe slide some metal pipe/sleeves into the holes first so it bottoms out?
     
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  6. cruiserpilot

    cruiserpilot

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    I have to agree with above, I'd use the wood as a template, followed up with
    'Made of Steel'. Insurance people 'wood' not be happy to see that.
     
  7. peterb

    peterb

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    I bought my HZJ-73 from a tall fellow. It has suspension seats. He had installed some angle iron to raise the rear of the seat sliders. This allowed them to go rearward a couple more inches. Might be simpler than installing wood/metal under the tracks. A search might reveal photos.
    Carry on.
    Peter
     
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  8. Tennessee Jed

    Tennessee Jed SILVER Star

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  9. zuker81

    zuker81

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    That square tubing is very tempting!! I just don't have the tools to deal with the cut out for the lever currently. It's on the wishlist though when I progress that far.

    Some of you bring up great points about the insurance question, and truthfully I hadn't thought about it. In an accident where I can imagine anything going so wrong that the seat base is affected, I think that the real concern is insuring my personal health as I think we all know they won't be giving me half what this truck is worth. The main issue would be if your weight was thrown backward into the seat, and another thread here actually complained that the hinges of the seat back gave way during a fender bender so they seem like the first weak point. Who knows, it's a valid concern, just not one that worries me all that much as I'm not giving this rig tons of risky highway time. If I rolled it bad on the trail, I could take these out probably in less than 30m if I had a drill gun. This just reminds me I really need to install a roll bar :eek:

    Re: wood compression. Another great point. My understanding is this wood is rated at 3684 which correlates to 3684 lbs of force required to push a 0.44" ball bearing halfway into the wood. I'm a skinny guy y'all ... that said, I think proper tightening up front with this hard of wood could be enough. If some play develops, I'm sure I'll hear or feel it with the way this thing rides. Your mileage may vary. I think my spine already compressed a couple millimeters the last few months.
     
  10. Tennessee Jed

    Tennessee Jed SILVER Star

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    Forgot about your relief cut in there - you could use a hacksaw to cut either edge of it through the corners, and file out the interior. Or better yet make friends with your local fabricator dudes so they can make you bumpers and racks etc.
     
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  11. hoser

    hoser SILVER Star

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  12. joekatana

    joekatana SILVER Star

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    Or buy a lhd 7x as they appear to have more legroom then the rhd ones, I am 6'2 and never had a problem in a lhd 7x but feel cramped in all rhd 7x's and even in the rhd 80 I am driving from Canada to Texas now.
     
  13. zuker81

    zuker81

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    And give up the look on people's faces when they realize they have to get in on the other side? No way!!

    Added to the list for this weekend ;)
     
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  14. pithicus

    pithicus

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    Nice solution.I wish my 73 looked like yours inside.
    Why don't 60's have suspension seats? Do 70's have heavier springs?
     
  15. joekatana

    joekatana SILVER Star

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    That novelty grows old very fast, the rhd 80 will be for sale as soon as I get home with it, if it was a lhd it would get a nice spot in the garage but after 10 days now the rhd starts to get annoying already.
     
  16. zuker81

    zuker81

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    The curve was steep the first few weeks but I don't really notice being on the wrong side anymore. I could see how for some it might take away some of the enjoyment of the vehicle though, and that's what's important at the end of the day.

    As far as 60 vs 70 suspension seats, someone more knowledgeable than me will have to chime in on that. For one thing, the shorter wheelbase of the 7x frame is a big factor making for a very poppy back-and-forth ride, exacerbated by the leaf springs. There may have been some commercial duty thinking behind these vehicles from the beginning as well.
     
  17. ForealBoreal

    ForealBoreal Cummins Boostin SILVER Star

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    lhd 70 series have more room for the driver opposed to RHD.
    Being 6'7" i could stretch out my left leg completely straight in LHD and i am completely unable to do that with a RHD truck.
     
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  18. hoser

    hoser SILVER Star

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    I wonder if JDM RHD differs from Australian RHD with regards to the driver’s seat position.