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Joel's multipurpose XJ build (rocks/boulevard)

Thanks for the links. Helpful.

The only downside I see to the stout aftermarket brackets referenced is most seem to move the shock mounts up higher on the axle which reduces available travel and I already got into trouble by bottoming out the shocks (10" travel). I was planning to raise the rear of my rig with a bastard pack but only by an inch or two and the shorter brackets would give that right back up. Now I could cut up the wheel wells to raise the shock mounts but it seems like if I'm going that crazy I should be using a long travel shock and some proper Deaver G09 leaf springs. That said, some of the stories about guys re-aching things gives me pause. if I were going to go nuts I tend to think I should build a 4 link rear. The problem is that relative to the cost of time if I were going to do links I'd want to do coil-overs too. After all half the reason I built things is because I like building things. That said, I still want what I've built to work and keep breakages to a minimum. I'm always trying to do enough research that I'm not totally out in left field (but 3rd base is okay though). It seems like a majority of folks on here are into hardcore rocks and therefore the quality of a build is based upon how big the numbers are comes after the word "dana" front and rear.

I find myself reading more and more of the jeep speed threads and I'm not all all sure beefcake axles and giant tires are worth the weight if you like going fast.

So the theme of this thread is multipurpose right? I have this crazy vision of 14" coilovers with roughly equal travel up and down. Seems like 16" is really pushing it. If I'm getting after this thing. I don't mind having shock mounts peaking through my hood. I know you need some serious reinforcements to not beat the unibody to death when going fast but that's something I'm overdo on getting done regardless. That said, is it nuts to spend the effort linking Chrys 8.25? (even a 29 spline version thereof?) Maybe I just need to be patient and find a basic D44 rear. I know it'd need a truss, but 33 x 12.5's seem to be the tire to go fast on and I'm not tackling a ton of stuff where I think the difference between 33's and 35's (much less 37s) would be that notice able.

If you had say a 4k budget to play with what would you do?

-Air bumps, 7100 shocks, and serious leaves?
-Fox 2.0, 2.5 remote reservoirs (or not) coilovers and links?
-King triple bypass something-or-other instead of bumps?
-Pickup some bad ass axles and cut to clear 37's?
-Screw it all and go v8? (breaks the proposed budget but at least it's something I know well).

One think I'll mention is that I'd like to avoid a full cage if I can... Done right the cross bracing ruins my interior volume for hauling stuff. I basically want a rig that's reasonably fun to drive, stops, goes, and is a solid compromise of peformance in the rocks and whoops. The more I look at it the more I think 33's with some overkill in the suspension department might be the way to get there. WJ steering and ZJ discs are already in the works. The simple version is to just do the basic stuff I was already planning, weld my broken mount back in and drive the thing. (Oh but put air bumps on it just because it's fun and different.

Too many possible plans and not enough concrete courses of action.
 
unless your motor is giving you issues or lacks the power you need: my .02 would be to start with coilovers/links all the way around.

then when you've only spent 2k to do that, then start shopping for that LS...
 
Who do you like for coil overs? Seems like King and Fox are the most well known but I've herd some good things about FOA and Sway a Way as well. Any others I should consider as well? Any vendors known to offer especially good deals?

I like the theory about building the links first and sizing from there...
 
I like Fox. I have been running their 2.0s on my rig for some time and am very happy.

kings are overpriced. FOA have a bad reputation but I have no experience with them.

Put a set of Sway-a-ways on a buddy's rig about a year ago. they seemed like very nice coilovers.

most everyone I run with has fox shocks and are very happy. I have become decent friends with Fox's contracted race tuner and he has been through my shocks a few times; it really makes a difference.
 
Perfect, that's a the kind of feedback I'm looking for. I had read a few good things about FOA, but I've now run across some poor reviews as well so it sounds like they're a little hit and miss. Sounds like Fox has great reputation with a solidly "upper middle class" pricepoint. That's a good place for me to start research. Anyone have vendors for Fox they like?

BTW there's several solid tech articles on coilovers here. I'm only partway through but it's extremely well thought out thus far.

http://www.pirate4x4.com/tech/billavista/coilovers/Part_1/
http://www.pirate4x4.com/tech/billavista/coilovers/Part_2/
 
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Hot damn...

Those coilover articles are good stuff. I tracked down the author and found he has a massive body of work in the wheeling world. Probably not a surprise to many folks who've been into this longer than I have but I counted this as gold...
http://www.billavista.com/Tech/Category_Index/index.html

His bio talks about launching from NAXJA so Bill if you're on here. Thanks!!!

One question from the coilover article part 1. In arguing for tuning based upon natural frequency (wheel rate and sprung corner weights) Bill makes the claim that you want a higher frequency in the rear than in the front. Yet, I seem to recall that quite a few folks are running softer rears with stiffer fronts and that seems to be the opposite of what he suggested. Any opinions as to why?

-Joel
 
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frijolee said:
Bill makes the claim that you want a higher frequency in the rear than in the front. Yet, I seem to recall that quite a few folks are running softer rears with stiffer fronts and that seems to be the opposite of what he suggested. Any opinions as to why?
Click to expand...

I don't KNOW, but I'd guess it's because there are three components to the natural frequency of a spring-mass-damper (K, M, b) system. And, usually, the front mass (with the engine) is quite a bit larger than the rear. Since Fn is (approximately) proportional to K / M, you need to run a larger K in the front than in the rear to get the natural frequencies close, but slightly higher in the rear.
 
Awesome jeep man and I love the LS. Last job was at a dyno shop and I specialized in the LS platform. Best motor on the face of the planet. Also, I have heard of your company as well in my pre-jeep days lol. What're the specs on the ls? cam, heads, ect?
 
Plinkerneil,
Thanks for that. That's a good way to think about it. To restate, if the weight of the front end is enough larger than the rear, the natural frequency in the rear can still be higher than the front despite using the softer spring rate. This works because the mass being controlled is higher which lowers natural frequency. It wasn't intuitive at a glance but it makes sense. I need to borrow some race car scales and then I'll see if I can put some math behind it.

Wisco,
The LS in the RX7 is a 429 ci LS2, Lunati forged rotating assembly, MTI spec 243 heads with upsized valves, 235/239 cam (pretty small for a stroker), plus a bunch of extra work in the breathing track. Glad to hear Ronin Speedworks is getting known.

The good news is that I pulled the RX7 my the garage for the first time yesterday (finally had the space after a move last August). As soon as that's repaired, I can rip into the Jeep more seriously. FWIW I've been doing quite a bit of reading on the coilover front and it just sounds like my style. I don't have to be on the biggest baddest tires to have a super fun multi purpose rig, plus I like having something to tinker with and tune. 33x12.5 sounds like it might be a sweet spot for me when my current 32s let go, that seems popular among the Jeepspeed guys. Plus this has the bonus that I keep my brand new 32" spare and call it close enough.

On the axles side of things, my impression is that I'll need more truss work to avoid bending. However the smaller shafts/ring/pinion are less limiting in the desert and more limiting in the rocks where big tires can spin and stop suddenly. I recently had it described to me that shock loads in rocks are typically the drivetrain fighting the wheels. It was a different way of thinking about things because that means it's not necessarily straight power that breaks shafts (IE like you see in drag cars) but rather momentum. Driveline momentum explains why breakage is especially prevalent in low gears and high revs. It also explains why rock bouncers always break their stuff. :D

Any massive flaws in this understanding? If not, then my axle budget moves to coil-overs and efforts focus over there. I was lying under the rig a few days ago and I think I can cut/segment my mid skid to work with links and I've found some nice graphical interface calculators to work out the anti-squat and geometry.
 
Plinkerneil,

All I really remember from my theory of vibatations class 15 years ago is that the net damped vibration equation uses partial differential equations therefore solving the full equation with damping is beyond the scope of just about all hand calcs. Undamped vibration is much easier as you alluded to (but thanks for that, saved me the trouble of looking it up).

What I find interesting is the care that must be taken with the units. Most of the time spring rates are referenced as lbs/in or kg/mm. However, at least to be used in the above equation we have to be talking lbf/in or N/mm such that Fn ends up as 1/sec. Now I'm curious what value manufactures are really using.

From http://billavista.com/tech/Articles/Coilover_Bible_Part_1/index.html

Spring Rate (k)

Coil springs have a rate – a description of how stiff they are. The rate describes how much the spring will deflect (compress) for a given load (weight) placed on it. The rate is measured in pounds per inch. The greater the rate, the stiffer the spring, and the more pounds of load it takes to compress the spring one inch.

Four things determine a coil spring’s rate:

The material from which it is made (the “torsional modulus” of the material, in psi)
The diameter of the wire from which the spring is wound (Dw)
The diameter into which the coils are wound – the Coil Mean Diameter (Dm); and
The number of active coils in the spring (Na)
Virtually any spring that is of interest to us will be made from chrome silicone steel, which has a torsional modulus of about 11,250,000 psi, so that when we calculate a spring’s rate based on its dimensions, the torsional modulus becomes a constant.

The equation for calculating a spring’s rate from its dimensions is:

k = 11,250,000 * (Dw)^4 / 8 * Na * (Dm)^3
Click to expand...

I looked this up as a sanity check on unit. Turns out BillaVista is missing a couple key parenthesis and one annotation of units. The correct formula should be:

k = [11,250,000 psi * (Dw)^4] / [8 * Na * (Dm)^3].

I confirmed this after a quick check in Shigley 7th edition (eqn. 10-9 if anyone cares). Also there's a small difference in nomenclature. Shigley notes the 11.25 Mpsi term as "modulous of rigidity" and states a value of 11.5 Mpsi as typical of carbon steel. I say good enough.
 
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When working this sort of problem, I usually convert to SI at the beginning, and then back to my target units after everything is done. My favorite units conversion site is wolframalpha.com.

Tuning a damped system using a theoretical approach is not exactly unsolvable, but the uncertainty involved in applying it to an individual car is pretty high. So the only practical use for theory in onesie-twosie applications is to make sure you avoid undamped oscillation as the system ages and degrades.

In the end, though, I suspect that most shock absorber manufacturers use units of "a little bigger" and "a little smaller". :D
 
frijolee said:
Wisco,
The LS in the RX7 is a 429 ci LS2, Lunati forged rotating assembly, MTI spec 243 heads with upsized valves, 235/239 cam (pretty small for a stroker), plus a bunch of extra work in the breathing track. Glad to hear Ronin Speedworks is getting known.
Click to expand...


:us::cheers:
 
Well, I went and did that thing you’re never supposed to do… Buy something without a firm plan in place.

Goals: I’m still looking for an all arounder kind of vehicle. I use this Jeep hauling the family, towing trailers, camping, rocks, oh and I want to be able to go faster in the whoops. I basically just want a small SUV version of a Ford Raptor but since I can’t afford one I get to build it.

The conundrum: I’m still driving on 3 shocks and I feel dumb replacing exactly what I had because it’s not nearly enough shock to go fast (which I love). I also just can’t see doing bad ass shocks or coilovers on stock axles. Mine’s a 99 so I have a little better axle internals but still... I also hate the constant clunking of the auto locker up front so I wanted some kind of selectable but again wasn’t looking to throw more money at a D30.

Anyways I ran across a pretty screaming deal on a front D44 that’s not quite right, but was still too good a deal to pass up and relatively local.

D44bought1s.jpg


D44bought2s.jpg


D44bought3s.jpg


D44bought4s.jpg


D44bought5s.jpg


D44bought6s.jpg



  • The Good: It’s a Dyantrac Trail series D44 (3/8” wall tubing) with a OX locker/cable, reid knuckles, 5.13 gearing, 1350 spindle, already rotated knuckles and one side worth of 35 spline shafts/CTV u-joint. ~64” WMS width which sounds doable under an XJ.
  • The Bad: It’s a 6 lug Toyota pattern, low pinion, missing quite a few things: long side shafts/joint, one spindle, locking hubs/bearings, calipers, OX shifter. It’s bare of mounting points which isn’t really a pro or a con.
Best guess, I have about a grand worth of parts to buy to put this back together assuming I run it. I also I need to put together a matching rear axle.

First question: Rear axle selection: What would y’all recommend? At the moment I’m leaning Ford 9, but the pinions are so damn low. I could also do a hp d60 rear but that leaves me driving on the coast side and there’s a still a possibility I’d add power via an LS or stroker. In terms of wheeling I like to go fast so weight of the axles is a consideration (a major upside of the Ford 9). Now that I’m into this I’m recognizing that finding used deals on something that really matches my front may be hard. I do spend a great deal of time on the street so I’m thinking the detriot tru trac is still a good rear diff for me. If I need specific gears and I’m planning a specific diff, disc brakes, width and I’d love 35 spline shafts to match, does that mean I should just bite the bullet and build up a fabricated housing with new parts? Are there any Toyota axles I’m overlooking that would be appropriate? If not I’m likely going to have to swap lug patterns up front but that’s not a huge deal. 5x5.5 seems common and that’s good for used wheels.

Second question: Tires: it really comes down to 33’s or 35’s. 32’s are wearing out. I’m thinking leaning 35s just because the D44 is built to take it (and maybe more). I don’t see 37s in my future as the cutting involved gets excessive and I want the uptravel. Anyone into the go fast stuff want to make an argument that I should stay smaller with the 33’s?

Third question: To link or not to link. I’m planning coilover fronts. That’s almost a given. Rear could be coilovers w/ links or could stay leaf with good shocks. I have hookups for ~20% off on either Fox or King (non-transferrable, so don’t ask sorry). The big advantage of leafs is the simplicity. Both my mid skid and exhaust work as-is with leafs but not with links. If I can keep shocks under the rig (or at least only protrude through to the surface of my current false deck) that’s a huge advantage in terms of storage space it save’s me in the back. I regularly haul hoods and 40” wide plates of steel back there for Ronin Speedworks. I could make the tower framework rectangular so I can put stuff on top but that’s extra work too and means no more sleeping in the back.

ToLinkOrNotToLink1.jpg



Links would wipe out some of my exhaust and mid skid. I can work around them to some degree but it’s a challenge either way.

ToLinkOrNotToLink2.jpg



I’d really love not redo my exhaust so the most likely route would be to section off part of my muffler and cut into the unibody rails to get the upper pivots higher but it might be a challenge to keep sufficient structural integrity. If I did links I’d be shooting about for 75% anti squat so I keep some travel under power. Thoughts?

Thanks in advance.
-Joel
 
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Solid work. I dig it. I'd also be looking for a way to seal off the towers from dust intrusion and full sheet metal isn't a bad way to go. However what you did also illustrates the loss of cargo space with towers. Compare that to the sheet of steel I posted and you can see my challenge. . Is de-arching of leaves just a fact of life when hammering bumps in the desert?
 
Doesn't have to be.... I run this Active Suspension kit on my XJ and it's great for hauling loads and taking jumps. I love it for the simple fact that I can run a softer leaf and adjust the pre-loading and height based on what I'm doing. Not to mention it actually pushes droop while flexing.


FA8FB17C-93B8-4727-AA91-62A1E7107FAA_zpsfggnnbyx.jpg


love the thread/read - keep it up
 
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That 44 looks almost like a waggy 44 essentially, I just built a set of axles (hp44 Detroit, chromo's, Chevy outters/highsteer, warn premium hubs, pretty happy and not a lot of money out of my pocket. My 9" is shaved with a Strange engineering 3rd(Daytona style pinion) Yukon grizzley 35 spline locker, Dutchman axles with matching 6 on 5.5 pattern with Isuzu disc(parking brake) and not a lot into it as well but ran into a lot of deals. Well worth it to have some real axles in a jeep and to have lockouts incase of a shaft or joint failure.
 
This build is amazing, good job brother a lot of good info in here. building all this crazy shit n I cant even find a decent welder.
 
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