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  1. #1
    Administrator wayoflife's Avatar
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    REVERE THE STEER - Rubicat Going Wide with 72.5" Dynatrac XD60 / PRO 1550 Front Axle



    Just because everyone and their mother runs big offset wheels with 4" of back spacing or less, doesn't mean it's necessarily a good idea. While pushing the center line of your wheels further out will help you to run bigger tires and without rubbing issues, you do it at the expense of increasing your scrub radius and at the cost of putting more stress on your ball joints, wheel bearings and even tie-rod. Of course, for most in the industry, that's just the way things have always been done, but for Dynatrac, it's a problem they wanted to solve. As luck would have it, Cindy and I would get a chance to help them do just that and with the assistance of Rubicat.

    Bigger & Better
    In addition to it's superior strength and significant weight savings, the Dynatrac PRO 1550 steering knuckle was specifically designed so that the steering axis inclination (the imaginary line you can draw through the axis of your ball joints) would meet at a point that's a lot closer to the center line of your wheel. By doing this, your wheels will pivot more instead of scrubbing as you make a turn and that alone helps to provide for much better steering and reduced stress on your tie-rod. In fact, the more back spacing you can run on a wheel (5.5" is optimal), the better everything will work especially with a set of 40" tires.


    Just to give you an idea of how much bigger a Dynatrac PRO 1550 is than a factory steering knuckle, here's a side by side shot of of the two. If you can believe it, the difference between the two is only about 1.5 lbs. and this in spite of the PRO 1550's massive size.


    Now, this is a side by side shot of standard PRO 60 steering knuckle on the left and a PRO 1550 on the right. As you can see, the opening is considerably wider on the PRO 1550 and this is to allow for a much bigger shaft. Also, because the PRO 1550 is made out of military grade aluminum instead of nodular iron like the PRO 60, it weighs about 8 lbs. less!


    While the PRO 1550 steering knuckles alone will help improve your steering and a set of wheels with 5.5" of back spacing would make it that much better, Dynatrac understood that there are a lot of folks running coil over systems like the EVO DTD, Cindy and I included, and that this setup would prove to be a problem. To help address it, they decided to create a new version of their awesome XD60 that is wider... a LOT wider! For reference, a factory axle measures 65.5" wide and it can be difficult to run big wide tires or a coil over kit like the EVO DTD without running wheels with very little back spacing and in some cases, wheels spacers on top of them. A standard full width axle like a Dynatrac ProRock 60, XD60 or ProRock 80 will have a width of 68.5" and while the extra 3" will make it possible to run wheels with more backspacing, you'd still end up rubbing the bypass shocks on a EVO DTD setup with anything more than 3.5". This new version of the XD60 comes in a huge 72.5" width - that's a whole 4" wider than a standard full width axle and that will allow you to run a wheel with a whopping 5.5" of backspacing and without any rubbing!


    If you're gonna buy a Dynatrac axle, it's always best to have one that's not only built by them but assembled by one of their technicians as well.


    Gotta love the XD60 differential cover in that it not only comes with a cool o-ring but it also comes with significantly bigger bolts that get torqued on and is used to help strengthen the entire housing.


    Final installation of our new 72.5" XD60 on Rubicat.


    Because there really hasn't been a means to accommodate high end bead lock wheels with a greater amount of backspacing, there hasn't been a need to make them and because of it, there aren't too many options to choose from. Fortunately for us, Trail Ready does and with 5.5" of backspacing - exactly what we needed and the best part is, they're made in the U.S.A.!


    Here's a shot that shows just how well the PRO 1550 and everything installed on it is tucked well inside the Trail Ready wheel.


    A few minor modifications had to be made to the bypass shock mounts to make everything work but I doubt most could even see it.


    While we may have been able to run wheel spacers to help make up the difference in the rear, we decided to recycle our old ProRock 60 and have it rebuilt to a matching width.


    Rubicat back on her feet again.


    Look at all that clearance! Oh, and yes, a skid plate for the ram will be installed. It was left off for this photo shoot as adjustments were still being made to everything.


    Close up shot of the passenger side PRO 1550 steering knuckle.


    Shot of the driver side.


    Time to do some fork lift flex testing to check for any rubbing or clearance issues.




    Just as it was designed, the drag link just misses the frame rail even at a full bump.

  2. #2
    Administrator wayoflife's Avatar
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    For comparison, here are a few shots of Rubicat with her new 72.5" XD60 axle standing next to Dynatrac's JK which is running a standard 68.5" axle. Both axles have the PRO 1550 steering knuckles installed, both JK's are running Trail Ready bead lock wheels with 5.5" of back spacing and with 13.50" wide tires.


    Although the extra 4" of width isn't necessary for a standard coil and shock setup or even on a bolt on coil over system, Cindy and I would still run the 72.5" XD60 Cindy even if we weren't running an EVO DTD if only because it offers a nice, wide, lower center of gravity stance and without having to run wheels with very little back spacing. That being said, if you like a factory look, prefer to have your fenders cover your tires or need to because of state laws, going with a standard 68.5" width will get the same job done so long as you aren't running a coil over kit like the EVO DTD. Obviously, Rubicat is running trimmed factory fenders so her tires are sticking out quite a bit past the flares but as you can see on the Dynatrac JK, it's tires are tucked nicely under the Mopar hightop fenders.


    An added benefit of the PRO 1550 knuckles pushed far into a set of Trail Ready bead lock wheels with 5.5" of back spacing is the amount of clearance you gain under your axle.


    Of course, this is to say nothing about the protection your lower ball joints will have from the rocks as well.




    As you can see here, the new XD60 front axle also comes with a built in ram assist mount and while ours doesn't have one installed yet, it can be outfitted with an EVO skid plate.


    We absolutely LOVE the new XD60 differential cover with its significantly larger 7/16x14 grade 9 bolts that can be tightened up to 85 ft lbs. of torque to and are completely recessed in the cover.


    For comparison, here's a shot of the Dynatrac JK with it's standard 68.5" XD60, running PRO 1550 knuckles and Trail Ready bead lock wheels with 5.5" of back spacing. You can really see the 4" narrower stance here.


    In this shot, you can see the optional EVO skid installed to help protect the PSC ram.


    Being that the Dynatrac JK is running a standard coil and shock setup, it can run a standard 68.5" wide XD60 and still have all the same benefits provided by the PRO 1550 knuckles and while running a 5.5" back spaced wheel.


    Here are a few more all around shots of both Rubicat and the Dynatrac JK.









  3. #3
    Administrator wayoflife's Avatar
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    Here are a few all around shots that we took of Rubicat soon after bringing her back home to Camp WAYALIFE.






    Really liking her new Trail Ready bead lock wheels.












    A couple of shots of her updated ProRock 60 rear axle.




    A shot of the front suspension. You can see how the bypass shock had to be changed to make this work.


    And finally, one more shot from the driver side.

  4. #4
    Administrator wayoflife's Avatar
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    So, here's an interesting comparison that'll help put some perspective on things. On the left, you have Rubicat with her new 72.5" XD60 front axle with PRO 1550 steering knuckles and running Trail Ready bead lock wheels that have 5.5" of back spacing. On the right, you have Moby running a standard 68.5" ProRock 60 front axle with Pro 60 steering knuckles and running ATX Chamber Pro II bead lock wheels that have 4" of back spacing. While Moby's tires are 40" tall, they're still only 13.50" wide just like Rubicat's tires and in spite of the 4" axle width difference, both Jeeps measure 85" wide from the outside edge of tire to tire.




    Here's a better shot of just Rubicat's 72.5" XD60 with PRO 1550 steering knuckles.


    And, this is a shot of Moby's 68.5" ProRock 60 with Pro 60 steering knuckles.


    An even closer shot of Rubicat's axle.


    And now Moby's front axle.


    Angled view of Rubicat's XD60.


    Angled view of Moby's ProRock 60.


    XD60 differential.


    ProRock 60 differential.


    PRO 1550 steering knuckle tucked far into the Trail Ready bead lock wheel and with lower ball joint completely protected.


    Pro 60 steering knuckle sticking way out of the Chamber Pro II bead lock wheel and with the lower ball joint completely exposed.


    Shot of Rubicat's modified EVO DTD bypass shock with relocated adjustment tubes and frame mounted reservoir.


    Moby's standard EVO DTD bypass shock setup with adjustment tubes facing out and reservoir mounted on the side of it.


    Here are a few parting shots of both Rubicat and Moby side by side.






    IN A NUTSHELL

    Why You'd want an XD60
    • Dynatrac signature profiled center section that offers maximum clearance.
    • 10.1" ring gear which is 16% stronger than a 9.75" Dana 60 gear.
    • New center section with increased rigidity.
    • Significantly larger carrier and pinion bearings for greater strength.
    • Lighter than a ProRock 60.
    • Proprietary internal Dual Sump High Volume (DSHV) lubrication system that provides optimal oiling.
    • Cast-in features for optimal air and electric locker connections.
    • 3-3/4" OD axle tubes with 1/4" or 5/16" wall thickness.
    • Differential covers designed to provide additional strength to the center section.
    • Differential cover O-ring that replaces traditional gasket.
    • Deeply recessed differential cover bolts holes for maximum protection.
    • Largest in the industry 7/16" fasteners.
    • Massive 1550 axle shafts.
    • 68.5" width allows for wheels with 5.5" of back spacing

    Why You'd want PRO 1550 Steering Knuckles
    • Made of military grade aluminum.
    • Significantly strong than stock and only 1.5 lbs. heavier.
    • Stronger than a Pro 60 and 8 lbs. lighter.
    • Ball joints are pressed into knuckle instead of end forging.
    • Bigger bore allows for use of massive 1550 joints or Series 30 CV joints.
    • New bigger upper ball joint.
    • Taller knuckle pushes ball joints out providing more leverage on tires.
    • Improved steering axis inclination reducing scrub radius.
    • Significant improvement in steering.

    Why You'd want Wheels with 5.5" of Back Spacing
    • Brings center line of wheel in and when used with a PRO 1550 knuckle, dramatically reduces scrub radius.
    • Reduces stress on ball joints and wheel bearings.
    • Protects knuckles, brakes and lower ball joints.

    Why You'd want a 72.5" Wide Axle
    • To run wheels with 5.5" of back spacing and still maintain a wide stance.
    • To clear EVO DTD coil over system components at a full turn and stuff.

    After 8+ years and well over 100,000 miles of punishing our Dynatrac ProRock 60 front axle on Moby, I'd be the first to say that I truly wondered whether or not an improvement to it was really needed. That being said, I'm glad to know that Dynatrac is the kind of company that is never satisfied with a "good thing" when "better" can always be had.

    Without question, the XD60 front axle is simply amazing in its design, superior strength and lighter weight in spite of some of its larger features. Coupled with PRO 1550 steering knuckles, a set of wheels with 5.5" of back spacing and wider 72.5" axle width if necessary, the XD60 will steer with ease (even with your lockers on) and have a turning radius similar to a factory front axle. For those of you who know, this is a HUGE improvement over the ProRock 60 which can at times feel more like driving a full size truck than a nimble Jeep. Of course, the ability to bring the center line of your wheels inward means that you'll put a less wear and tear on your ball joints and wheel bearings and being that your tires will no longer pull inward when taking on tough climbs, your tie-rod will see a lot less stress as well.

    I literally could go on and on but I'll stop here and be more than happy to answer any questions you might have.

  5. #5
    Administrator wayoflife's Avatar
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    While Cindy and I were doing some additional filming for the video we're working on, I happened to notice something that was worth documenting and sharing with all of you. Specifically, while parked and with the engine running, I turned Moby's steering wheel from a full lock to a full lock - back and forth multiple times and after the fact, I saw the following footprint left behind.
    Attachment 249181

    As you can see in these close up shots, you can really see just how much his tires were scrubbing around the steering axis inclination, basically creating arcs around a point and leaving behind a blurry footprint.
    Attachment 249182

    Attachment 249183

    Now, here's what the footprints looked like from Rubicat doing the exact same thing.
    Attachment 249184

    As you can see here, her tires were clearly pivoting in place and leaving behind distinct and well defined prints of her lugs, twisting around a center point.
    Attachment 249186

    Attachment 249187

    The proof is in the prints

  6. #6
    Administrator wayoflife's Avatar
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    Thanks to her brand new Dynatrac XD60 front axle and PRO 1550 steering knuckles, there really is no question that Rubicat steers and turns a hell of a lot better than Moby, of who is still running a ProRock 60 front axle and with older Pro 60 steering knuckles. However, Cindy and I wanted to know, just by how much and how would she compare to something like a stock JK Unlimited. Needless to say, we decided to do some turning radius tests and here's what we found out. For reference, a bone stock JK Unlimited running 225/75R16 tires measures 73.9" wide and has an advertised curb to curb turning radius of 41.20'.

    Out in an open parking lot, we found a pair of planters that were spaced exactly 5 parking spots apart and with each spot measuring 108" wide. This gave us an opening measuring 45 feet across and that was more than enough for a stock JK Unlimited to clear.
    Attachment 249596

    With her new 72.5" XD60, PRO 1550 steering knuckles and running 37x13.50R17 Cooper STT Pros mounted on Trail Ready beadlock wheels that have 5.5" of back spacing, Rubicat measures 85" across. For the purposes of this test, we started her exactly on the inside edge of the passenger side parking line.
    Attachment 249597

    As you can see, Rubicat easily cleared the planter but had it been a curb lining a street, she would have still hit the other side by if by just a bit.
    Attachment 249599

    Here's a shot of Rubicat after pulling her all the way through the turn to the point where her front tire would have cleared. Curb to curb, we measured a turning radius of 45.27'. Basically, 4' more than stock.
    Attachment 249600

    Attachment 249598

    For comparison, with his 68.5" ProRock 60, Pro 60 steering knuckles and running 40x13.50R/17 Cooper STT Pros mounted on ATX Chamber Pro II beadlock wheels that have 4" of back spacing, Moby also measures 85" wide. Starting off at the exact same point.
    Attachment 249601

    Attachment 249602

    As you can see here, Moby couldn't make the U-turn and clear the planter.
    Attachment 249603

    Attachment 249604

    Attachment 249605

    When all was said and done, we found that measuring curb to curb, Moby had a turning radius of 50.72'. That's almost 10' more than stock!

  7. #7
    Old Timer Mike_JK_Houston_711's Avatar
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    Wow major freaking overhaul. Good work.


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    B.O.D. Build - 2014 Granite Crystal JKU - http://wayalife.com/showthread.php?4...t-Build-Thread

  8. #8
    Been Around the Block FuriousDz's Avatar
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    Wow!! Excellent explanation about this!!
    So sorry if this is a stupid question but are the 1550 steering knuckles a 60 and up thing not something that would work on a prorock 44?


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  9. #9
    Been Around the Block Tylersilverjku's Avatar
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    Wow looks amazing Eddie! Thanks for all the information! Can't wait to see it get dirty


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  10. #10
    Administrator wayoflife's Avatar
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    Quote Originally Posted by FuriousDz View Post
    Wow!! Excellent explanation about this!!
    So sorry if this is a stupid question but are the 1550 steering knuckles a 60 and up thing not something that would work on a prorock 44?
    Not a stupid question at all. The Pro 1550 was designed and made as an upgrade to the Pro 60 steering knuckle and yes, it is for a 60. It would not work on a ProRock 44.



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