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Technical Rear triangulated 4 link

Discussion in 'The Hokey Ass Message Board' started by StefanS, Oct 31, 2018.

  1. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    This is kind of a continuation from my notch thread. While I was under there looking at things, I decided I want to maybe bag the rear. Now I'm not going to hook it up to switches or anything, but l like the fact of being able to determine my exact ride height and pinion angle, with no possibility of settling to a different height/pinion angle or negative arching. I found a kit made by Helix for $307 with free shipping. That includes every part needed including 2500 pound double bags, 50' of line, fittings and all arms and brackets. That's about a hundred cheaper than a pair of new leaf springs after shipping. My question is, if the bag's right over the axle or behind it, will it hang low enough when I jack the car up to get the rear tires off? I would hate to have to unbolt the bottom of the bag if I got a flat or something like that.
     
  2. Mr T body
    Joined: Nov 2, 2005
    Posts: 2,028

    Mr T body
    Alliance Vendor
    from SoCal

    Helix is a Hoffman brand. Move forward carefully.......
     
  3. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    I emailed the company selling the kit and asked them if they can remove the lower bars and lower bar frame/axle brackets. I went on suicidedoors and found lower arms with bushings the exact width to use my front leaf spring eye. I'm sure the bags aren't the best but what else should I be weary of with that company?
     
  4. AndersF
    Joined: Feb 16, 2013
    Posts: 628

    AndersF
    Member

    I have never buy anything from them but search Hoffman on this site and see for your self.
     
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  5. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    All I could really find was things about their front suspension parts.
     
  6. Reds 29
    Joined: Jan 16, 2006
    Posts: 435

    Reds 29
    Member

    I have used suicidedoors suspension parts on a number of projects. All the parts were first rate and good info too. I used their universal triangulated 4 bar set-up on a project and it works great. I also used the air bags from them, but like you are planning, no tanks or compressors. I have a shrader valve mounted where I can get to it.
     
  7. Whether or not it will hang low enough to get the tire off will depend on the geometry of the suspension, body, and air bags. I don't think any of us can answer that question with the lack of information you provided.

    Another thing to be aware of is total suspension drop out when jacking the car up, or even going over big bumps. The bags may have much less rebound travel then the shocks. This would cause the bag to become the suspension limiter and support the weight of the axle/suspension under extension/rebound conditions. Air bags are not designed for this purpose, and you can easily tear the rubber away from the bead plate. Look at using limiting straps (common in the 4x4 / Off Road community) to control the amount of rebound if required.

    On my '62 Merc, the air bag (Slam Specialties) does not allow enough rebound to get the tire off without unbolting the limiting strap and airbag (only 4 bolts, so not a real big deal in the shop). For that reason, I carry a tire repair kit, a can of "fix-a-flat", and enough hose to reach from the compressor/air tank to any of the tires on the car. Unless it is a massive blowout, I can probably fix it and air it back up on the side of the road. If it is something major, that is what tow trucks are for.
     
    Last edited: Oct 31, 2018
    CaddyRat likes this.
  8. DDDenny
    Joined: Feb 6, 2015
    Posts: 12,226

    DDDenny
    Member
    from oregon

    And briskly!
     
    XXL__ likes this.
  9. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    Stay away from Hoffman Group and Airbagit, they sell junk that looks the part, but is inferior all around, even the bags they sell are rip offs called Denominator, a rip off of the well regarded Air Lift company Dominator series bag. Suicide Doors/ Thorbecke Brothers are a class act and know what they're doing, and have been at it for awhile, and in the truck world, are regarded as some of the best. I have used them before with off topic air suspension trucks, and they make some really nice, heavy duty stuff, but a lot of it is made to order if they aren't doing a run of something, so you could be waiting a bit. AVS on the web is another great source for quality air suspension fabrication parts, good prices and a lot of what they sell, they stock in house, as well as carry the brand names. Gambino Kustoms I believe also has a kit exactly with what your looking for, though it will be more than the Helix one, but a much better product.
    *AIR SUSPENSION IS NO PLACE TO CHEAP OUT ON PARTS*
     
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  10. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    I "built" a full kit on suicide doors and it came up to about $200 more than the helix kit, which isn't bad if it's that much better. Limiting straps are a great idea. The lower arm axle brackets I'll be using are 3.5" long (axle tube to bolt hole). If I use those (straight down from the axle) and mount the upper arm axle tabs to the front of the axle tubes instead of on top, will that cause any torque issue? With the tabs on top the arms would be at completely different angles
     
  11. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    off the top of my head, I forget the maths of it when I set up a tri 4 link in one of my trucks, but at ride height, the uppers and lowers are mostly parallel to each other with the uppers having a very slight negative angle on them, and I have no bind throughout articulation. Having the top bars' axle mount to the front of the axle tube and the lower mount to the bottom, seems like it could cause some binding and pinion angle issues. One of the issues with a triangulated 4 link, always seems to be the space and clearance they require to have them work correctly. I would also highly recommend getting atleast 1 side of the uppers to be adjustable to fine tune/ correct any issues down the line.
     
  12. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    Thans for the response Stooge. Mounting them that way, the bars will be parallel. If I mount the upper bars on top of the axle, they go up toward the rear while the lowers will be parallel with the ground
     
  13. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    You do realize you responded to my post about deciding to use suicide doors parts instead since the cost isn't much more at all..?
     
  14. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    Come on Ken, we've already steered him in the right direction to Jason Thorbecke! (Muttley from the ye' old C10forum o_O as you can see I forgot all of my math from there already!)
     
  15. XXL__
    Joined: Dec 28, 2009
    Posts: 1,728

    XXL__
    Member

    That's not what that post says, but OK.

     
  16. Blue One
    Joined: Feb 6, 2010
    Posts: 9,815

    Blue One
    ALLIANCE MEMBER
    from Alberta

    If you want to bag something get a job in the supermarket.
    If you buy anything from any Hoffman company you are asking for a screwing.

    You've been warned, the rest is on you.
     
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  17. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    True, I didnt say it word for word which maybe I should have. The $200 more isn't bad if it's that much better part was an implication of my decision. Anywho...I'm piecing a kit together from suicide doors since it's only a couple hundred more and the wearable parts won't need to be replaced right away, which in turn would potentially double the cost of the helix kit. There, fixed it
     
  18. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    I don't necessarily need airbags. Let's say I bought four inch lowering Springs like I planned...it would cost me $290 for the pair, another $80 or so to ship them and I'd still need 2" lowering blocks to sit where I'm at now. Then once the springs settle I may have to shim the rear. Then since they're essentially de-arched 4", that's just that much sooner they'll invert and not only change the ride height but change the pinion angle yet again. That's what I just went thru with my old springs. The problem now is, I'm about an inch to 1.5" past my scrub line and I need to fix it asap
     
  19. chopolds
    Joined: Oct 22, 2001
    Posts: 5,652

    chopolds
    Member
    from howell, nj
    1. Kustom Painters

    Much as I don't mind using bags sometimes, if it's economy and longevity you want , stick with what's already there. Get new leafs, lowered, and fine tune them with blocks. Yea, your OLD leaves gave you problems, but they were already 50+ years old! To spend 300 and get a new rear suspension that will last another 40 years, is a bargain. AND you don't have to bother with running air lines (hard lines are better, the plastic ones tend to leak), changing out bags every 5-10 years, compressor wiring, compressor wearing out, welding on all those brackets on the rear and chassis ( are you a good enough welder to do this?) etc., etc.
     
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  20. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    If I knew the leaf springs wouldn't go to crap and would stay where they were height wise when I put them in, I would 100% prefer them over bags. I was thinking coilovers but those things are crazy expensive. I was also thinking caprice rear coils but I cant find coil buckets anywhere
     
  21. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    Well guys, Speedway has coil spring buckets (upper and lower). Heres my plan...Welder Series upper bars, adjustable ends, bushings, frame brackets, axle brackets and lower shock mounts. Suicide doors lower arms, axle brackets and upper shock crossmember. Speedway coil spring buckets and I'll hit the junkyard for rear 2nd gen impala, caprice or caddy coils. Worst case scenario I'll buy new coils from summit or somewhere like that. The buckets dont have coil retainers so I'll be going with the limiting strap idea. Thanks for everyone's warnings and input.
     
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  22. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    Good plan with static lowering and adjustable arms! I like my air suspension truck, it rides nice, and was a good engineering exercise, but I don't see myself doing another air suspension vehicle. i used all quality components, but there are too many opportunities for something to go wrong that I don't drive it much, and with all the time and money spent, (a lot of both), I would definitely go with a static or coilover adjustable suspension before I would do air again, atleast with my own money.

    The adjustability of the rear links, with coils and some good shocks, will make for a fun, worry free drive
     
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  23. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    The rear suspension works great as is with the leaves from the '53 but my scrub line with the blocks is out the window. Bags were my last choice, but the price of that kit vs new leaves (as well as the other benefits of a link vs leaf suspension) made them move to the top of my list. Since this is my daily driver, it'll be nice knowing when I go outside in the morning the car will be sitting the same exact way it was when I went to bed.
     
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  24. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,584

    mgtstumpy
    Member

    The bitterness of poor quality remains long after the sweet taste of low price is forgotten
     
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  25. KustomKreeps
    Joined: Jan 7, 2016
    Posts: 323

    KustomKreeps
    Member

    got to say the Ridetech 4-link set up I got is a nice kit. Good thick parts. good instructions. mounts for bags/coil overs. adjustability. Might not be the cheapest on the market but is still nice kit.
     
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  26. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    The thread kinda got off topic and turned into who's kit was best so let me just keep it rolling. If I follow the 60% rule for the upper bars, it puts them at 14.5". Does that seem too short? With the brackets adding about 2.5" on each end, it'll make the overall length (from frame to axle) exactly how long I measured. In my research I've found that the top bar can angle down towards the frame and that'll work as well, so I can lengthen the top bar if needed.
     
  27. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    Not to throw another monkey in the ring, but have you thought about sourcing some tried and true '60-'72'ish chevy truck/ nascar trailing arms? place for a coil already on the arm and just need a frame spring pocket, and theres only 2 of them to make fitting them a bit easier and you just need a crossmember to mount the fronts to. *edited to correct the triangulation remark

    A few threads to mull over
    https://www.jalopyjournal.com/forum/threads/nascar-truck-arms.672544/
    https://www.jalopyjournal.com/forum/threads/new-truck-arms.451597/
     
    Last edited: Nov 2, 2018
  28. StefanS
    Joined: Oct 7, 2013
    Posts: 1,020

    StefanS
    Member
    from Maryland

    I initially (a year or two ago) looked at the Jimenez kit but I cant figure how they're running dual exhaust without it running below the frame where the crossmember is. I imagine the truck two link is the same..? I know the Jimenez kit uses a pan hard bar which also makes dual exhaust tough. The truck system doesn't use one?
     
  29. Hnstray
    Joined: Aug 23, 2009
    Posts: 10,695

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    This not quite correct. The GM/'NASCAR' trailing arms do indeed need a Panhard Bar or Watts link. They have no ability to keep the axle in place side to side without a 'track' control device.
     
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  30. Stooge
    Joined: Sep 9, 2015
    Posts: 323

    Stooge
    ALLIANCE MEMBER

    Beat me to it! I was just going to revise that, too many damn suspension designs in the old noggin. adding a panhard centering device to it wouldn't be the end of the world, especially with the simplicity of the trailing arm set up

    Running dual exhaust through a trailing arm and panhard set up has been done, just need to get a bit creative
     
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