Radius Arm Info

[PELLEY]

Disclaimer: Long time A-Arm guy, getting ready to start my first Bronco build (should be picking it up this week!). I searched all over on here and didn't find what I am looking for. Sorry if this is a rookie question, just don't have much experience with beams.

Ok so I am trying to get some info on building a set of radius arms for the new ride. Beams is a whole different topic, trying to stay away from that for now (found lots of info on those). I understand the basic concept of longer radius arms, added length decreases the amount of caster change as the suspension moves through it's travel, please correct me if I am wrong. Them longer beams decreases camber change... My question is, when doing longer radius arms in conjunction with say a 4" lift, do you need to incorporate a change in caster built into the radius arms to match the lift, in turn giving you the desired caster after the 4" lift? I know this is done with the beams with the C/T, but I have not seen any talk about changing radius arms. That said I don't have the Bronco in hand yet to do a little R&D. Is the caster built into the beam, or simply provided with the radius arms?

Thanks for any and all help. New to the forum and TTB so please don't chew me up to bad, haha.

Chris

[philofab]

Caster decreases quite a bit the farther an I beam droops. So if you install a 4" lift with stock radius arms (assuming you can even get the spring in) you will not have enough caster to keep the vehicle going straight without driver input.

Additionally the stock radius arms are so short they limit travel and the bushings do not live long under hard use. I tend to build radius arms that give stock caster at ride height or increase it slightly.

[KBL]

There's about 5 degrees of positive caster built into the TTB beams. You don't need to build much (if any) caster into the radius arms.

Longer radius arms need custom pivot brackets--the height of these pivot brackets influences caster, as does the construction of the radius arms.

[PELLEY]

There's about 5 degrees of positive caster built into the TTB beams. You don't need to build much (if any) caster into the radius arms.

Longer radius arms need custom pivot brackets--the height of these pivot brackets influences caster, as does the construction of the radius arms.

Ya I found a good picture of some new radius arms that Solo built. In the picture you can see in the frame where the OG mount was and where it was moved to. The frame moves down as you move back which will help create that caster gain, paired with the pivot brackets moving the pivot down a little further. After all that change it doesn't seem like much caster change from re-locating the pivot brackets, not much, if any, needs to be built into the arms themselves.

[CBDuner]

I've been wondering the same thing myself, and haven't found much info, but have saved lots of pictures. Looks to me that a lot of the arms don't have much built into themselves, but just dropping the bracket lower compensates for the caster correction, like you said.

[ChaseTruck754]

Yeah - there's usually only a couple degrees in the rad arms if any. Much of it is built into the beams and then the pivot brackets like has previously been stated.

[PELLEY]

Well I don't wanna say it sounds easy, but sounds reasonable... We will see, looking to start pushing some heat very soon here!!! I think I'm even gunna TIG these bad boys, been about 4 years sense I have touched a torch, but should be like riding a bike... haha