School me on radius arms. . . . .

[mustange70]

Alrighty so i decided to make a switch from leafs to radius arms and decided that you guys in here would be my best bet to get a good straight answer and ideas(and after my first tastes of some half decent air, well kinda 4'high for a good 40'. i will get pictures for proof ), i would go 4 link but simplicity and cost and the fact that i do a lot of mud bogging(main purpose for the truck, and i've found 4link's plow a lot of mud in the pits).

The truck in question is an 80' f-250, d60f/10.25r, both with 4.10's and lockrights, i stretched the wheelbase from 133 to 145" (pushed the front end foward), then it has a 6" lift with leafs front and rear and the lift is from custom made shackles and hangers with a shackle flip in the rear, and it performs ecellant, but i want more, more performance in the high speed area opf fun.

So here's what i've come up with and few things that i desire out of this. First is that i'll do this front and rear. After taking some measurements i found that a length of 48" will work well as far as where the arms mount to the frame and all that goodness, but if this won't work i will change it. Then for springs and shocks i'm thinking of using some soft coil springs and then use some fox 2.0 air shocks for adjust ability, i want to use coilovers, but the ones i want cost more than what i can afford, whereas the fox shocks and coils i can get for cheap.

Now design/performance wise i'm looking for something that can provide excellant travel (i want to shoot for at least 18"), but a catch is that i need to keep as much artulation as possible so i can stay competitive in the pits (we have lots of deep nasty holes and decent articulation has won me a couple of mud bogs ). Now here is where i need the majority of the help. Where does the bind occur in a radius arm setup? I've been playing in autocad and it seems as though it occurs when the top and bottom of the axle want to travel in different arcs, as the other endsof the radius arm don't allow any movement and there's not enough give in the bushings/heim joints correct? If i'm wrong please point me in the right direction

So i played around and i found that you can change the mounting points on the radius arm to get these arcs to intersect in a useablerange of travel in order to retain some reasonable amounts of articulation, i think anyway , if anyone has any input chime in. Next thing is with mounting the springs and shocks. Now i know with all the high travel deserts trucks and buggys that use a trailing arm setup the coil overs are mounted to the trailing arms, would this by acceptable to do to the radius arms?

i thank anyone in advance for any input in this, as i intend to beat on the truck and i thought i'd ask the guys that know high speed best.



p.s. i intend the use some big ass hiems on the radius arm to frame mount with bushings on the axle end and the trac bar with also use bushings on the axle end and a hiem on the frame connection.

[MudOnTheTireS10]

Don't happen to need weld-on C's for the radius arms do you?

Oh and I'd go with a flex joint (like a Johnny Joint) rather than a huge heim. Not to mention that to buy a heim as big as I would consider proper, it'd cost you damn $60+ when all is said and done.

[mustange70]

Yeah i'm not using the weld on c's, the mounting is the same style as what you drag racing 4-link setups use. The hiems i'm planning to use are bigger then proper and they are something i'm willing to spend some coin on, as i'm only having to purchase 4.

[WHITE RHINO]

check out my build

[mustange70]

Good flex, nice build overall, that flex is about what i want to achieve. I did some play around in the shop today and i think that i'll wrist on arm, well its kinda like a wristed arm, its along the lines of a shackle set up on the bottom connection bar then where it connects to the upper tube it would use a small shackle (using 1/2" plate no longer than 2'' centre to centre) to allow for the movement that prevents bind, i think should work, i have a mock up i'll snap some pictures of and post em up.

White rhino the one thing that you should condsider with your rig is the that one good hit on that arm and its gonna bendm as the 2"x.25 dom used the way you have is not very strong when the truck drops off a ledge and lands on a rock or something it can very easily bend the arm, also buckling could be an issue at the point of the stock arm to the dom, but i dunno how much dom covers the factory arm. I don't mean to bash or anything, but just my $0.02, but yeah i like the truck

[WHITE RHINO]

yeah thanks for the advise i have smashed them pretty hard on rocks nothing happens they are sleave about a foot onto the stock arms i might pull them off and plate them more with 3/8"s i havent had time to do it and its not high on my priority list right now but thanks again

[Scott F]

For high speed running, make you panhard bar as long as possible to minimize side to side axle movement. I would make the axle mount as far outboard as you can, and then do the same on the frame. Build the frame mount wider than the frame. At ride height the bar should be near level.

[mustange70]

Awesome, basically keep the arms and panhard as level as i can, keep the mounts wide and the panhard as long as possible. That helps a lot.

[braxton357]

Originally Posted by mustange70

Good flex, nice build overall, that flex is about what i want to achieve. I did some play around in the shop today and i think that i'll wrist on arm, well its kinda like a wristed arm, its along the lines of a shackle set up on the bottom connection bar then where it connects to the upper tube it would use a small shackle (using 1/2" plate no longer than 2'' centre to centre) to allow for the movement that prevents bind, i think should work, i have a mock up i'll snap some pictures of and post em up.

White rhino the one thing that you should condsider with your rig is the that one good hit on that arm and its gonna bendm as the 2"x.25 dom used the way you have is not very strong when the truck drops off a ledge and lands on a rock or something it can very easily bend the arm, also buckling could be an issue at the point of the stock arm to the dom, but i dunno how much dom covers the factory arm. I don't mean to bash or anything, but just my $0.02, but yeah i like the truck

A couple things, if you're going with a non C bushing radius arm style--a la every long arm jeep setup--then it's pointless to wrist. Use a radius arm on the side of the axle the diff is on, then only a single link on the other. Basically, a --- rather than ---< Same thing as a wristed arm. I personally would just do 2 radius arms, make them long enough and forget about wristing...still plenty of flex--again, look at almost all long arm kits--
Also, I don't know about him bending the 2" DOM...but if you're going to be using it for a not-so-high clearance app like mud/desert racing then you build your arms differently, like the guys running beams up front in desert trucks do... Two separate tubes the entire length rather than one. Kind of like this.

Otherwise, there is a weeks worth of reading material here on radius arm/3 links. Including many how-to's. Search for it all for a better understanding.

[mustange70]

Good point braxton with tthe three link style setup, but due to the ag tires i plan on running, if they grab there's gonna be some serious axle wrap happenin if one side is just -------- instead of ------< as you suggested. The style i've planned on is pretty well identical to that in the picture you posted, only the ends that mount to the axle are rotated 90* in comparison the those i-beam/traction beams arms in that picture. I will do some more searching on pirate to see if i can come up with something and i'll post back with more questions probably, but if anyone has any input please post up.

[mustange70]

Alrighty i think i'm all set to go, just need to do everything found some things though that i had a question on, more or less with shock/spring placement. In the the desert wheeling picture thread the picture of the baldwin truck is the one i'm referring to:



Now in my truck i'm limited for space on the front axle (drivers side), so much so that coil sping placement on the drivers side would place the coil spring half way on the dana 60's pumpking, and i'd like to avoid this, essentially to keep from welding on the housing cause welding to cast is a bitch and i don't want to deal with the proper welding procedures (i'm a welding engineering tech.) so i don't bugger up the housing.

So anyway would using this type of cantilever setup be applicapable to support a 5000lb truck? I'd build it using some 2x.250 dom instead of plate, do some basic bends use some 1" or larger grade 8 hardware for the pivot points, then make the travel ratios vary with different mounting points from 1:1 to i dunno 1.5:1 and then have a few different adjustment points to vary ride hieght. I would do this for the fronts only and keep the rear basic with the coils on the axle inboard of the frame (i'd use some front eb lift coils or coils from a jeep), then mount them on a similar mount that again can be varied for ride right adjustments (low for the fast stuff and high for the deep mud), then mount the shocks on the radius arms to gain travel.

So would something like that work for me up front or should i persure other routes?

[Samco Fab]

I would say dont use the cantilever setup for the front suspension, it would add a ton of extra weight, money and complexity.

I made a front "tripple bushing" radius arm setup and mounted the coilover to the radius arm. I used a 12" coilover and got 15" of travel at the axle. Here are some pictures, but it might be hard to see. The FJ handles good on the street, the radius arms have kind of a sway bar effect, but still flex.

[Beat95YJ]

If you aren't sure if a cantilever setup will work, you are not ready to put one on the front of a truck. Pay a pro, or startup with an easier project.

[mustange70]

Good point on the weight and cost issue samco, beat. As far as getting someone to work on my truck for this kind of stuff, well i simply can't afford it, and the only thin they would be doing that i can't is the design/setup, plus its just and idea that i was wondering about to save some packaging issues that i have in the front end, but thanks for the input.

Peace out i have all the answers i need.