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Changing from a Crawler to Speed Runner - Coyote Install

rcmbronc

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Seriously thought about selling my bronco and building a new one. Wife decided against it for me but I want to change how it handles.

Right now pretty much set up for woods crawling and not the very best at faster speeds. Have some ideas to change and looking for opinions.

Change the tires and wheels to 35x12.5x17 with aluminum wheels. Radial tires. Looking at Maxi Trepadors. Open to suggestions.

Looking at changing the front to King coil overs. Probably keep the Cage arms.

Looking at adding a front sway bar. Suggestions?

Not sure what to do with the rear end. I have 4.5" WH leafs that I have removed a couple of leaves out of. This way has a bit of sway so maybe need to add the leaves and lower the truck a bit maybe with different shackles or maybe different leaves. Could link it or trailing arms with coil overs but not really ready for that yet.

Any suggestions?
 
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thorgan

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Dec 26, 2012
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Air bumps! Fox, Sway-a-way, King - it doesn't matter. I'm using Light Racing air bumps in the front only because I haven't had a chance to add them to the rear yet. This is the single most effective modification you can make to your suspension in my opinion (former vehicle dynamics engineer for the Nevada Automotive Test Center). Set them up so you won't need your rubber or poly bump stops any longer. You'll find that you don't have to slam on the brakes when you see a big bump coming. You can just drive right through it without worrying that the suspension will rebound uncontrollably.

The front sway bar is good for on-road handling. I'm using a front bar I adapted from a '96 Dodge 1500 4x4 and it works great because I added quick disconnects and I unhook it when off road to cut down on head-toss. You'll want to add a small rear sway bar to add roll stiffness in the back. Otherwise you'll find that it pushes a lot in the corners (understeer).

My opinion is that the coilovers are unnecessary unless you plan on doing a lot of spring rate tuning. Matter of fact, you'll probably find that they add a bit of ride harshness because of the rigid spherical bearings that connect them to your chassis at each end. This is why most shocks use rubber or poly bushings. Cuts down on harshness. Bypass shocks would be badass because of the tunability although you're getting back into spherical bearing mounts again and the accompanying harshness.

I'll probably think of other stuff...
 
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rcmbronc

rcmbronc

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Air bumps sound like great idea. Did not think about that.

One of the main ideas with the coil overs is that it helps me get better shock location with a good reservoir shock and not working around the coil spring.
 

Bukin 67

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Hi rcm. I was pretty much where you are now. I wanted my Bronco to handle better on long desert runs. We did some 500-700 mile runs in the desert southwest and I beat it up trying to keep up with the pre-runners. I knew this was the direction I wanted to go in, so I talked to my race fab buddies and came up with a plan to completely rebuild it.

My build thread is HERE. You might be able to pick up some ideas to get started without going balls out at first. My first advice to consider would be to remember, you can really wad it up at speed, not that you can't rolling down a hill or off the edge of a canyon when crawling, but things need to be pretty beefy and reinforced when you do a pre-runner type build to take the abuse, so how fast you want to go will determine how far you go in that direction.
 

ntsqd

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Hydro-bumps are good (there shouldn't be any air in them, just nitrogen and oil), but effective damping over the whole travel range is more important to driving manners and are where to first focus time & $$.

Not convinced that coil-overs offer a huge advantage in anything other than the packaging of damper(s) springs, etc. For going at speed the smallest damper to use up front would be a 2" body with at least a 5/8" damper shaft. Note that this counts out Bilstein 5100 and 7100's, and that's not an accident. Those have 14mm shafts and by the time you get damping that works you're in danger of bending those little shafts in a big hit. IF you can figure out how to do it, put the dampers in front of the axle. This is one of the key things that makes a Stock class desert racing Ranger of Full size work the best. It is all about shock piston speed & travel distance, and putting the damper in front of the axle is effectively an over-drive for both. With all of the unsprung mass involved, over-drive is a good thing.

Flip side is that a remote res 7100 with a 255/70 or 275/78 shim stack (depending on "63'd"* springs or not) in it works very nicely on the rear.

Dial-out every last bit of bump-steer that you can figure how to get rid of. What was OK in a crawler won't be at speed. While you're under there go with the longest trac-bar and drag link that you can fit.

*63'd Springs: those springs with a spring-perch sized shim at the center bolt between each pair of leaves and have tip sliders. Refers to the fabled 63" long GM truck springs that were the first common domestic use of this friction reducing technique.
 
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FlogginHarvey

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I gotta say if I had the time and money I LUV Bukin67's build. But I don't and won't for a while. So, I tried to go in the middle: trail build I could take to the sand dunes from time to time and still get my wife and two small daughters to the fishing hole and icce cream hut from time to time. It's taken a lot more time than I thought but it is close. (Waiting on a radiator to get it "trail-worthy" now.) I went WH 4.5" lift springs, king shocks, full cage, and plan/hope for king bumps down the later this year or early next.

It's night and day on the black top and on the pasture/dirt road it is sure footed and stable. Sand dune trip this fall after work settles a bit.

Pics in garage and build thread under "Sweet Pea Go-fast'ish"
 

toddz69

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Air bumps! Fox, Sway-a-way, King - it doesn't matter. I'm using Light Racing air bumps in the front only because I haven't had a chance to add them to the rear yet. This is the single most effective modification you can make to your suspension in my opinion (former vehicle dynamics engineer for the Nevada Automotive Test Center). want to add a small rear sway bar to add roll stiffness in the back. Otherwise you'll find that it pushes a lot in the corners (understeer).
.

Since you worked at NATC, do you know Jim Frens?

Todd Z.
 

thorgan

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Dec 26, 2012
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Yes, Todd, I know Jim very well. He and I were partners in Nth Degree early on. I learned everything I know about vehicle dynamics from Jim.
 
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rcmbronc

rcmbronc

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Alot of good info. Thanks,

I am not pre-running but want to be very stable at good speed. Do you think the rear should be linked instead of leafs? Also should I used different front arms instead of the Cage arms in front? I see Bukin 67 used a three link up front and four link in rear. Seems good with the rear lowers reinforced. I would assume a link set up in the front would be better and to control the front axle caster change during travel. Also the rear being linked may be more stable.
 

ntsqd

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20" of poorly damped wheel travel will be beaten by 8" of well damped wheel travel every time. Emphasize the damping and control of the suspension instead of max wheel travel.

There are plenty of desert race, pre-run, and chase trucks out there capable of sustained high speed in the rough that use leafs in the rear. At the outer limits they're not ideal, but if you're not going to go there then I'd focus on the basics first. If you opt to stay with leaf springs I'd look for the longest spring that you can fit under the truck.

As to radius arms vs. a three link; I don't see the pay-off for all of the effort until you're really moving, and you will need to do considerable design work before cutting any metal. The key is to look at your ride height and what the Caster gain/loss is from there towards full droop and full compression. Yes, it is a good thing to to have Caster gain from full droop and not being starting from the wrong side of zero. Even a long radius arm won't give you that, but it will reduce how far on the wrong side of zero you are at full droop. My guess is that you'll find it easier and better for all aspects to lower the truck's ride height. In doing that you'll need to really look at how to gain up-travel. Don't accept extended or tall bump-stops. Work until the axle can touch the frame without bending, hitting, or binding anything else, then add the bump-stops back in. Crawlers tend to set ride height at 70% down/30% up or taller. Desert racers are more in the 50/50 zone.

What is helpful is to have some mild toe-in at full droop. How often do you expect to have the truck airborne? Can get that stability at landing from the late style steering linkage. That is actually WHY Ford used it, it caused some toe-in in droop.
 

thorgan

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Dec 26, 2012
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79
The Cage arms look nice and beefy. It's doubtful you'll need any changes there.

Back when I had rear leafs, I was using the WH 10-leaf packs for 3.5" lift. As was typical for those packs, I experienced some sagging and loss of lift so eventually I performed a shackle flip which dropped the rear spring eye some 8". Theoretically I should have gotten an additional 4" of lift but, as I found out, going from a tension shackle to a compression shackle adds a spreading force vector to the leafs and they flattened out further. I probably went from about 2" of lift in the rear to about 5". Anyway, I drove it pretty hard with that setup which, to be honest, was more stable than my current rear 2 link. However, in my case, this is more a function of my steering geometry.

In the end, there's really nothing inherently wrong with rear leafs. Some of the most impressive vehicles we developed at NATC had rear leafs. However, they all had air bumps (or as ntsqd correctly points out, hydraulic bump stops), at all 4 corners.

I will also reinforce what ntsqd says about shock location. You want the best motion ratio you can get and mounting the front shocks as far forward as possible on the radius arms will achieve this. This is also the biggest problem with the rear shocks. There's just no room to locate a shock that's sufficiently long enough unless you are ok with cutting big holes in the floor. I went a different route and swapped to full width axles. This gave me the ability to package air springs at all 4 corners with my rear shocks on hoops inside the rear wheel wells.

Long story-short, it's a slippery slope when you start making these sorts of modifications...but the reality is that the stock configuration with coils in front and leafs in back can be everything you really need.
 

Bukin 67

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Bukin 67 what tires and wheels did you end up with and size?

BFG Km2 35 x 12.5 x 15 on Raceline Monster 8" beadlocks with 3,25" backset.

I started the NORRA 1000 with a brand new set of Km2s this year and did the whole 1280 miles without any issues whatsoever. We ended up lugging 5 spares to Cabo and back but that was fine with me!
 

markw

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I can tell you Bukins set up handles the rough terrain of Baja very well. Very different feel from leaf sprung suspension. Well sorted out I'd say. And no flats!
 
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rcmbronc

rcmbronc

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Great info. Sounds like right now I am going to stick with the cage arms and leafs. Not looking for alot of air time.

My thought was the front coil overs mounted next to the steering knuckle. Any farther forward would be in the steering and track bar I think. I wanted to lower the truck any ways. I agree work towards full compression to frame and use the hydraulic bump stops from there. Again I am not in love with coil overs but they do help I think move the shock for the best motion ratio but I may need to look at it and see if I can do it without. Also easier for spring changes. Kind of planning on 2" or 2.5" King or Fox fronts with reservoirs. Also on the rear. The rear shock mounts will be interesting not sure where to exactly put them yet. also pretty sure I will want a custom rear housing.

Still have the D44. Any reinforcement or mods I should do there?
 

ntsqd

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Double-edged sword there in c/o's. 2.5" spring selection didn't used to be as good as those for a 2.0, but a 2.5 moves a lot more oil which is a good thing.

One guy I know likes to put a socket on the upper BJ nut, with a Caster adjuster set for max Caster, and builds his c/o mount to *just* clear the socket & ratchet. On an EB this may put the upper mount thru the hood. Depends on what stroke c/o you go with. If you're going to cycle 13" you don't need a 16" c/o....
 

Bukin 67

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Still have the D44. Any reinforcement or mods I should do there?

I never trussed mine. I only replaced the stock 44 cover with a beefier ARB one from WH. I've seen some stock covers get beat to pieces. Other than that the housing is stock - with the exception of the upper and lower link mounts of course.

I never even switched over to the beefier Reid knuckles. I've had no issues with the stockers. It's on the list, just not done yet.
 

ntsqd

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Reminds me, you WILL want to cut and turn the C's for more Caster once ride height is sorted out. Ignore the OEM specs for anything that lacks power steering. Been some past discussion here about this as to what Caster number to shoot for.
 
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rcmbronc

rcmbronc

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Good point. Will do. Now got to find some time to start mocking this stuff up. Thanks, I am sure I will have more questions.

I assume I want hydraulic bump stops on the rear also.
 
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