Radius arm brackets different distance from front (0.25" - 0.5"): should I fix?

[DuctTape]

Radius arm brackets different distance from front (0.25" - 0.5"): should I fix?

Trying to tune handling. 3.5" lift, 31" tires going to 35". Steering geometry is solid (trac/drag angle) after drop pitman and trac riser, toe is good, tire pressure good, box centered. Isn't super scary on pavement but it does wander a bit with just the 7 degree c-bushings. The wander is bad enough to make snow & ice driving scary, so it needs to get fixed.

Currently have 1.8d/1.6p caster (measured with bc tool and digital level). Decided to install 4" radius arm drop brackets vs turn the yokes. The wh drop brackets are welded on over the stock brackets.

Thanks to Paul (dirtdonk) for telling me to check the existing stock brackets because sure enough they are different from each other by about 3-4 degrees (pass bracket is close to 90 vs frame rail behind). Took a reference measurement and driver's side end of bracket is 1/4" farther rearward than passenger side. But I'm not sure which one is correct.

My trig is pretty rusty but if I did the math right I'm predicting with no correction that after installing drop brackets the drivers side will be around 0.4" farther rearward than pass side, which would make my front axle around (I think) about 0.5 degree off perpendicular to centerline.

My question(s):

1) wouldn't that give the rig a pull to driver's side? Or is that so small an amount it isn't worth fixing thru shims when I put on the drop brackets?

2) Is 90 degree correct or should the drop brackets angle back a bit to make the arm/bracket angle closer to perpendicular? I know that's part of what bushings are for but I can't figure out which one is at correct angle.

3) Would shimming 1/4" on the driver drop brackets compromise structural integrity of the drop brackets? I'm not an engineer or a welder but I know increasing the fulcrum length puts more force at the pivot point.

Basically I don't know if I should worry about fixing it or not, and if I fix it I don't know which side to correct to. As always the help is appreciated.

 

[jasonb]

Have you looked at the James Duff drop brackets? They replace your existing brackets, and they are also adjustable for caster. And they just look good (in my opinion). I had them on my last Bronco, which had a 3.5 inch Duffs lift, and that truck drove great. I never checked the alignment as this was all done before I bought it, but like I said, it drove great. Just a thought.
Jason

 

[phldwsnoc1]

Wheelbase delta

It's been a while but I don't think wheelbase variations of that amount are uncommon. I wouldn't do anything until it was assembled and precise wheel alignment measurements were taken. After a look at the big picture the key adjustments are usually clear. The radius arms are overbuilt to the point that shimming for correction will not be a problem if needed. Keep us posted and good luck!

 

[DuctTape]

Have you looked at the James Duff drop brackets? They replace your existing brackets, and they are also adjustable for caster. And they just look good (in my opinion). I had them on my last Bronco, which had a 3.5 inch Duffs lift, and that truck drove great. I never checked the alignment as this was all done before I bought it, but like I said, it drove great. Just a thought.
Jason

I did consider them but they were twice as much as the wh brackets plus simpler installation. I did the math and trig said the wh brackets would get me on the outer edge of acceptable caster without changing c-bushings and I could go lower degree c-bushings if I ended up with too much. Never considered that stock brackets would be off (I should have). If I had it to do over again probably would have just gone the yoke rotate route but duff's would have been better than current situation as to install the duff's you cut off the stock brackets.

 

[Whoaa]

I'm going through this right now also. I have the same problem/issue, but going a different path to correct it.

I recently bought a set of the Duffy long radius arms, they have a threaded hiem joint on the end versus the old doughnut bushing. The threads are deep inside the radius arms, several inches, and this will allow for some adjustability to square everything.
I cut the old radius arm mount off of the frame, w/o measuring them for accuracy before cutting them off. Next I fitted the new radius arm mounting brackets. Upon close inspection and detailed checking and re-checking the proper location of the new brackets I couldn't get the drivers side and the passenger's side to reconcile based off the measurements provided in the instructions for the new mounts. The instructions said the location of the new mounts are suppose to be 10 1/4" back of the old location. I measured back 10 1/4" and set both mount in place and was ready to weld them solid, but before welding them I decided to pull some measurments in other places just to make sure everything was perfect before making a solid weld. I pulled measurments from just about every place that I assumed and *thought* should be the same to both side; I measured from the front of my un-altered original frame, I measured from the motor mounts back, and of course I measured from the old/stock radius arm mount location back to the new location. Everytime I made measurments from the left & right sides and then checked the location of my new mounts I was continously off by anywhere from 1/8" to 1/4". I finally choose a "happy medium" location to weld the new mounts knowing that I could take up any difference, and hopefully make everything square, with the threads on the hiem joint.

Interestingly enough through this process I learned a lot, LOT about the production quality and lack of attention to detail of old Bronco frame's, and specifically the poor quality welds. Next I spent 3 days grinding out crappy welds and fixing them, finishing welds that were left short from the factory...suffice to sayI now feel my frame is better than it left the factory.

Fast forward to today. Based on the recomendations of my local aligment shop that is used to doing 4 wheel aligments (front and back) on modern cars, I am now going to "square" my front-end to my rear end. The body and frame are close, but I want a Bronco that has the best aligment posible while still using "old" technogy, but using "modern" aligment methods.
So tommorow when I thread the heims into the radius arm end, I will pay attention to getting both arms the "same" lenght, but the focus will be on squaring the front-end housing to the rear-end housing by making sure the distance on the outter R side is the same as the outter L side. And this may mean that the overall lenght of each radius arm assembly may be slightly different.

I have a bunch of neat pic's to tie these comments together, but for some reason my dam photo bucket won't load them right now....

 

[surfer-b]

If I were doing this, before welding, I would also square the front and rear, of course the rear would need to be checked to see if it is square with the frame then the front could be set up with the rear axle. A quick way to chk would be to plumb down the center of the front and rear axle, make a mark on the shop floor and measure between the 2, do both sides and check for diff. A cross measurement would also be good. This would not be perfect but tell you if its close.

 

[Justafordguy]

X3, I think it would be more important to have the front radius arm brackets the same distance from the rear spring hangers so the front and rear axles would be parrallel.

 

[DuctTape]

Thanks guys - you gave me a duh moment with the squaring to the rear insight. Of course that is what matters most - axles parallel to each other - I should have thought of that...

Thanks very much for the help!

 

[DuctTape]

So just got done tack welding the the drop brackets on. I squared to rear axle, which required a 5/16 shim on passenger side, but I'm within 1/16" of square. I was going to finish welding them in but ran out of welding gas, so will have to wait for Monday when supply shops open to finish the project.

Just before I called it a day I decided to check kingpin to front frame horn and came up 1/4" different driver vs passenger side. That threw me so I checked rear leaf mounts to front frame horn and sure enough 1/4" different. I couldn't check rear frame horns as they had been modified from stock by po.

If I did my trig right then my axles are 1 degree off perpendicular to frame. I'm guessing it won't even be noticeable unless someone has a perfect sight line.

For the good news my prelim caster has gone from 1.5 degree range to 8.5 degree range and while front pinion angle might bind in droop, at rest I don't have binding. Since I have 7 degree c bushing in, it gives me a nice range of caster to play with to fine tune.

 

[Whoaa]

Since the last time I read and contributed to this issue, I have got mine squared and welded in place.

On mine, I couldn't find a "perfect" fit location for the new radius arm mounts when I was doing them. And like a dummy, I kept taking measurments from various places from the front; such a radius arm mount location to the front of the frame, R arm mount location to engine mount welded to the frame, new R arm mount location -forward- to the old/stock R arm mount location. I got them "pretty close" and *thought* I was within 3/6" of the new mounts being parallel to each other, then welded them solid.

My new radius arms have a deep threaded hiem joint in the end about 2" deep, and I figured I could take up the 3/16" that I thought I was off on the new mounts welded to the frame w/ the threads. Of course I figured out how to make it square....which was a trip to the local aligment shop and they said to square the front end off of the rear end.

Anyway, now I'm ready to install the heim end into the new radius arm. I pulls some measurements from the outter L and outter R side of the rear end. I found that 3/16" instantly! The right side was 3/16" shorter than the left. So 1 hiem got screwed in 3./16 less deep that the other side, slide the radius arms in place and through-bolted. Then I pulled measurments from the front diff housing to the rear diff housing and bingo! They're so close to being exact, you can't get them any close by using common tools like a tapemeasure and square. Now I'm really happy w/ the way it came out.

Mine is running and driving yet, but very cloose....within a couple of weeks.

As soon as its running and moving on its own the first place we're going is to the local aligment shop (on a trailer) so I can get a super accurate reading of my caster, toe in, and 4-wheel alignment square.

 

[DuctTape]

Sounds like you had the same issue with rear mounts. I wonder how common it is? I wonder how much axles not being square to each other matters for handling?

I gotta believe axles not being square to frame isn't that big of a deal as the only connections other than springs are the pitman and trac bar, and both of those should have enough wriggle/adjustability, right? If it was extreme I guess the vehicle would point slightly different than path of travel but I'm thinking that's a looks issue not a function issue, at least at the variances we are experiencing.