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Spring Conversion On Flatfender

Discussion in 'Flat Fender Tech' started by Heimbig2, Jan 12, 2020.

  1. Jan 12, 2020
    Heimbig2

    Heimbig2 Member

    Richland, WA
    Joined:
    Jan 13, 2003
    Messages:
    151
    I have a CJ3B with a centered dana 44 rear end and a custom dana 44 front end. Spring under with passenger side drop. I am looking at doing a spring conversion, I would like some feedback from those that have done either the Holbrook springs or Wrangler spring conversion. I currently run Black Diamond 2 1/2 inch lift springs and am looking for a better ride.

    Thanks

    Mike
     
  2. Jan 12, 2020
    duffer

    duffer Rodent Power 2019 Sponsor

    Bozeman, MT
    Joined:
    Sep 17, 2009
    Messages:
    2,552
    I just finished putting the Holbrooks on the front of my 3B (rear still on the to do list). I have no miles on it to tell you how they perform. All four of the springs in my kit had a lateral bow in the second leaf which also forms the military wrap. I had to grind about 3/16's off of the military wrap eye on those warped leaves to keep them from applying lateral pressure (and the subsequent accelerated wear) on the spring hangers and shackle mounts.

    The spring hangers supplied are constructed of 3/16" material as opposed to the stock 1/4" wall hangers. More important, the spring bolt holes were not perpendicular to the hanger mounting bolt's centerline. I would be willing to bet the hangers are Omix Oda. I ended up re-using my front stock hangers and made my own rear hangers. The spring bolts supplied in the kit are grade 5 9/16" off-the-shelf bolts. They were length sized for the hangers width but that leaves about one third of the inside bearing surface being threads. Made my own greaseable versions out of Grade 9 bolts (McMaster-Carr).

    Last, but certainly not least, the suggested mounting distances leave the shackles standing vertical and, under full droop, there is a distinct possibility of a shackle inversion. I think you could decrease the instruction suggested distance from the shackle hanger centerline to the spring hanger centerline by an inch and be about right. I also moved my front axle 3/4" forward from the spring bolt position.

    Would I purchase these springs knowing what I know now? Probably not but I have yet to experience them on the trail. Just moving the suspension with jacks, I can easily see I have more than double the travel I had with the previous Rancho 2 1/2" springs. If you do decide to go this route, maybe you can just buy the springs and forget about the rest of the "kit".

    There are a few photos of the front installation here:
    The Square Deal
     
  3. Jan 12, 2020
    y2grey

    y2grey Member

    Fayetteville NY
    Joined:
    Sep 18, 2011
    Messages:
    80
    Unless you are going to upgrade to Old Man Emu do not go YJ. Stock YJ springs sucked on YJs that's why we all dumped them. My MB5 is SOA. It runs Walck rear springs with a few leaves pulled on all 4 corners. So far a really like them.
     
  4. Jan 12, 2020
    Heimbig2

    Heimbig2 Member

    Richland, WA
    Joined:
    Jan 13, 2003
    Messages:
    151
    I was planning on OME if I go that route. Would love to hear from someone that put these on a flatfender.

    Mike
     
  5. Jan 13, 2020
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
    Messages:
    4,519
    I've got Holbrooks on my '51 and have been running them with Rancho 9000 adjustable shocks for years. I really like them and have had no issues with them at all over the years. Nice articulation, and pared with the RS9000s adjustable so I can firm them on the road and soften them on the trails that 'touch' you need now and then.
     
  6. Jan 13, 2020
    Norcal69

    Norcal69 Out of the box thinker 2019 Sponsor

    Northern California
    Joined:
    Sep 6, 2014
    Messages:
    1,264
    I was under the impression that Holbrook is no longer doing the jeep spring kits. That is the reason I went with OME yj springs on my 5.
    Duffer, How long ago did you buy your springs?
     
  7. Jan 13, 2020
    duffer

    duffer Rodent Power 2019 Sponsor

    Bozeman, MT
    Joined:
    Sep 17, 2009
    Messages:
    2,552
    My Holbrook springs have been occupying garage floor space for 3 to 4 years. Holbrook's did not actually manufacture those springs. They are a product of Benz Spring. Benz Spring Company – Benz Spring Company manufactures leaf springs, custom springs, u-bolts, and many spring steel applications.

    I'm going to guess Benz would still make a set to the Holbrook specs.
     
  8. Jan 13, 2020
    Heimbig2

    Heimbig2 Member

    Richland, WA
    Joined:
    Jan 13, 2003
    Messages:
    151
    Does anyone have any photos of using the Rocky Mtn kit on the front spring hanger of a flatfender, or can direct me to some photos. I am looking for the front leaf spring hanger instaled on the very front of the jeep.
     
  9. Jan 13, 2020
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
    Joined:
    Aug 13, 2015
    Messages:
    3,583
    This is my personal opinion, so take it or leave it, but a flatfender’s front frame horns are the frame’s weakest point. They are prone to cracks everywhere around the spring mounts and around the crossmember under the radiator. Adding longer springs (and maybe a Saginaw steering box?) into the mix will be increasing the leverage on these already vulnerable horns. I’d highly recommend replacing the horns with tubing, or at a bare minimum boxing and cross-bracing the horns if going with springs that are longer out front.

    Keep in mind that a flatty’s front springs are shorter than even a CJ5’s front springs by a few inches (3?), so jumping up to a YJ-length spring (3 more?) will almost necessitate some frame work anyway to keep the mount from being unsupported.
     
  10. Jan 13, 2020
    Norcal69

    Norcal69 Out of the box thinker 2019 Sponsor

    Northern California
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    Sep 6, 2014
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    1,264
  11. Jan 13, 2020
    Sierra Bum

    Sierra Bum Member

    The High Sierra
    Joined:
    Oct 23, 2017
    Messages:
    146
    I don't post too often, but I follow the forum when I have time. It is a great place and resource...

    I may be able to offer a few insights here, having set up a few custom suspensions on these old jeeps. I'm with ITLKSEZ in that you will likely (and probably should) end up doing some frame work to strengthen and lengthen the frame for longer springs.

    Usually to improve both ride and off road suspension performance we look to go with longer springs on these old Jeeps. There are a few ways to go about it. I just finished a similar project on my 68 CJ5 and it's worth it. I ended up extending my frame a little and moving my front axle forward some as well.

    First, the flat fender frame is shorter than the ECJ5 frame. I suggest taking some spring and axle placement measurements and it will all make sense.

    -Flatty springs are about 36" long in the front and 41" long in the rear, and 1.75" wide.

    -Wrangler springs are about 44" long both front and rear and 2.5" wide.

    -Early & Intermediate CJ springs are about 38" long in front and 44" in the rear and 1.75" wide.

    -Part of the attraction of the old HOLBROOK Long Leaves is that they are asymmetric springs; the center bolt/axle placements are not centered on the spring. They created a kit that allowed for longer springs without real frame modifications...you simply move the spring hangers but NOT the shackle brackets because one end off the center bolt is made to stock length.

    SOME OPTIONS FOR LONGER SPRINGS
    -An old school Flat Fender mod was to put the 41" Flatty rears on the front. These will probably fit without lengthening the frame.

    -ECJ5 springs set (BDS for example): this would likely entail some lengthening work in the rear to accommodate the longer spring.

    -ECJ5 rears front and rear: This would require lengthening the front and rear frame on your flatty.

    -YJ Springs: Involves the most work to accommodate the longer and wider springs front and rear.

    -HOLBROOK Long Leaves, if you can still get them: Move spring hangers only.


    TIPS: Take lots of measurements. Before you strip off your old suspension, mark and make notes of axle placement. Decide if you're going to move the front axle forward. When you get ready to install your new suspension, mock everything up first. Tack everything in place and weight things before the final welding and bolting. You want to get your shackle angles and axle placement right and there's a good chance you'll want to adjust/move things a little. A 1/4" will make a difference.
     
    ITLKSEZ likes this.
  12. Jan 13, 2020
    Heimbig2

    Heimbig2 Member

    Richland, WA
    Joined:
    Jan 13, 2003
    Messages:
    151
    I did check with Benz spring and they have the drawings for the Holbrook style. Just for info they are about $820 for all four.

    Mike
     
  13. Jan 13, 2020
    73 cj5

    73 cj5 Not ready for the junkyard yet

    MS
    Joined:
    Jan 10, 2014
    Messages:
    1,075
    I opted for used YJ springs ($75) on my junkyard project. My Zuk had some SOA with 35's and it was flexy, comfortable, and pretty stable.
     
  14. Jan 13, 2020
    y2grey

    y2grey Member

    Fayetteville NY
    Joined:
    Sep 18, 2011
    Messages:
    80
    Rear springs to the front did not require extending the frame. Shackle mounts moved to the front of the frame, spring hangers slightly trimmed and mounted directly behind the originals. Everything lined right up.
     

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