extended radius arm question

bushman_22 · Mar 6, 2013

First of all I apologize if this has been answered before. I am going to be building extended radius arms for my 72 and am wondering how to determine what length they should be. I have read multiple threads and have come up with at least 6 different lengths. Everyone gives you their opinion on length but can't seem to find why that length was chosen. Just trying to understand.

Bushman_22

shamu · Mar 6, 2013

Wild Horses old arms are 11.5 inches longer than factory.

burntfish · Mar 6, 2013

Some reading.
http://classicbroncos.com/forums/showthread.php?t=141187
http://www.norcalbroncos.com/forum/showthread.php?t=1405&page=1&pp=15
http://classicbroncos.com/long_radius_arms.shtml
Wristed
http://www.broncofix.com/viewtopic.php?t=261596
http://www.colorado4x4.org/vbb/showthread.php?67425-Early-Bronco-front-articulation

http://www.pirate4x4.com/forum/newbie-general-4x4-discussion/964435-wristed-radius-arm.html

bushman_22 · Mar 7, 2013

ok I reread everyone of those articles. The only thing I found as far as determining length was the longer I go the more body roll I get with more flex (to a point). The shorter I go, the less flex and body roll. That's it? otherwise these guys are just pulling numbers out of the air. I have seen differences in length from 3" longer up to 15" longer than stock in almost 1" increments.(non wristed) Anyone else want to weigh in on this: IE what your current set up is what kind of driving you do and how satisfied you are with the results of your length choice and what your length choice was.

Bushman

Doyle · Mar 7, 2013

I started researching this last year, but still haven't got it done. What I found was less than 6" of extension wasn't worth the small gains, and more than 12" of extension the additional gains were minimal. I would probably go somewhere in the middle, the more serious offroading done, the longer the arms.

Nelson · Mar 7, 2013

I went with 10.5"s after looking at all the different lengths people have used. I finally decided on 10.5"s due to the fact that there is a hole on the bottom of the frame about 10"s back from the original rear frame mount. I cut the original frame mounts off and drilled a .310" hole in the top of the mount (frame side) and threaded it for a .375" bolt. The head of the bolt fit in the hole on the bottom of the frame perfectly. This meant that the frame mounts should be aligned and square to each other and a plumb bob confirmed that both axle were square and parallel. Hope this helps.

Ethansdad73 · Mar 8, 2013

There is someone making the extensions that just bolt to the stock arms ...may help with guess work and fab time... unless your wanting to bend them for tire clearance..

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70_Steve · Mar 8, 2013

I built a set of Lars Bars, which wind up about 6" longer than stock. Reference the NorCal Broncos link above. I wanted better articulation, but nothing too extreme. But that being said, I also built a pair of coil spring towers 2 1/2" taller than stock, and installed some 5 1/2" springs. Net suspension lift is 3" but the front does move pretty well. The pic below is on the ramp, measuring for shocks.

I'm happy with the performance. I do get more roll than with the old 2 1/2" supension lift, but it's not bad at all, and very predictable.

Pic courtesy of motoman!

bushman_22 · Mar 8, 2013

Thanks for the answers guys. I was just trying to understand where the length numbers were coming from. If I can get mine to stretch out as well as yours 70_steve, I will be happy.

Bushman_22

burntfish · Mar 8, 2013

I have stock bars that have been wristed that flex like steves or better.

Howard2x4x4 · May 16, 2018

Nelson etal, I've got this on my further down the road to-do list, after I actually do get the Bronco going down the road. I like the thought process behind 10 1/2 inches. How were the stock arms extended to work, ala Lars bars? Did you re-use the frame mount brackets? Also, I've seen comments regarding body roll when radius arms are extended. Can someone please comment? Thanks everyone! Howard in beautiful west Michigan

Skiddy · May 16, 2018

Howard2x4x4 said:
Nelson etal, I've got this on my further down the road to-do list, after I actually do get the Bronco going down the road. I like the thought process behind 10 1/2 inches. How were the stock arms extended to work, ala Lars bars? Did you re-use the frame mount brackets? Also, I've seen comments regarding body roll when radius arms are extended. Can someone please comment? Thanks everyone! Howard in beautiful west Michigan

just put mine on this year and the body roll really isn't that noticeable 3 1/2" lift. drives so much better even at 75mph

Boss Hugg · May 16, 2018

Skiddy said:
just put mine on this year and the body roll really isn't that noticeable 3 1/2" lift. drives so much better even at 75mph

^^^Duff long arms, BTW. (for the OP.)

Skiddy · May 16, 2018

ahuggins6 said:
^^^Duff long arms, BTW. (for the OP.)

oops yes sir

jonpblewis@yaho · May 16, 2018

X2 on the 10.5" . Can't remember why for sure. I think I was going for 11" but found a 21" piece of dom 1.5"OD x 5/8"ID in the scrap bin and that took the guess work out of it for me. I also dropped the mounts 1.5 - 2" and inward a bit too ?

Apogee · May 16, 2018

Howard2x4x4 said:
...Also, I've seen comments regarding body roll when radius arms are extended. Can someone please comment?

A radius arm front suspension essentially works like a sway bar, where most of the give is provided by the bushings at the c-wedges. When you make the radius arms longer, they have more leverage over the bushings and allow for more twist, and thus more sway/roll.

Howard2x4x4 · May 16, 2018

Skiddy, how much longer are the Duff's Long Arms?

SteveL · May 16, 2018

I have the wh/all for fun arms on my 72. Travel is great bot it does add quite a bit of body roll on the road. Some of the guys I asked about it said a lot of the body roll is from the inboard rear shocks. I did both mods at the same time so not sure which added more roll. Currently working on making it more road worthy and changing shock mount so we'll see.

Skiddy · May 17, 2018

Howard2x4x4 said:
Skiddy, how much longer are the Duff's Long Arms?

10 1/2" longer than stock

Howard2x4x4 · May 17, 2018

Thanks Skiddy! And don't be lookin' at my booger welds! Howard in beautiful west Michigan

extended radius arm question

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