Is my DOM too thick?

[Mike Bradbury]

I am in process of converting a C20 to C10 and getting rid of the rear leaf springs. I am building my own set of trailing arms too. Never could find a thickness from any of these companies that sell trailing arm kits, they only described them as heavy wall DOM tubing. So I bought some 2" x .250 wall DOM tubing notched and welded bushing ends, and got some soft polyurethane bushings.
Now I am starting to think that the tubing might be over kill and will not flex enough, and cause the bushing and weld to take the brunt of the torsion. I know that that is the bushings job but the original trailing arm was able to twist more, relieving the crush factor on the bushing. Also since I went with poly bushings they are a bit stiffer than the rubber so this in turn is going to add quite a bit of torsion to the weld. I am confident in my welding ability, but the more I think about it I don't want to add repetitive strain day in and day out, plus I don't want to have to replace worn out bushings every 20,000 mi. Where if I went to a thinner DOM that has a little flex in it might solve some problems in the future. I would appreciate some advice, am I thinking about it too much or is it just too stiff.
Sorry the images kind of suck, only had a cell phone on hand.

[HotRodYJ]

Overkill is good. I personnally wouldn't want my link bar to flex any at all, I think you'll be fine. I use 1.5" OD .25" wall DOM for most all my stuff.

[2tons of fun]

flexing bars is bad.

why would you want any of it to flex, its not a 4x4/crawler, flat and stiff is street and fast.

[Shane]

you are right on the money about the stock 2 pc. trailing arms being designed to flex ... that's the reason they are riveted together as opposed to being welded ... for what it's worth

[FnLow69]

i think everyone will have a different answer to this question, but suicide doors link bars ar made from 3/16". my link bars on my dodge are made of 1/8" DOM, for a none weight bearing (meaning airbag not mounted to it) 1/8" DOM is ok. 1/4 should be fine, probably overkill but will work. Most truck frames (1/2 ton) arent even 3/16" wall...for what its worth

justin

[Mike Bradbury]

This is what I was thinking, I would rather be a bit to overkill than a bit to linguine. Since I am still in the design stage I still may cut the joint and put a heim joint in place.
Before I asked my question I did some research and came across many opinions on the forum about Heims and how they make it louder and they tend to wear quicker. But they do make a less binding set-up. I am also planing on mounting Bilstein coil overs to the ends of the arms behind the axle.
Thanks for the advice, Any body else?

[71'tahoe]

Get some currie flex joints or flex joints from suicide doors or from rubicon express.

They are like heims but run a delrin bushing and they are all rebuildable. They wont be as stiff as poly non flex bushings you have now.

All those companys sale them and the most expensive ones Ive seen were ballistic fab and they where still under $50 a piece. They have the weld on ends included,all you do is weld up where youre bushing mount is now and your good to go. Hope this helps

[Mike Bradbury]

Yes that is exactly what I was thinking about! Thanks, has the flex of a heim and the softness of a bushing. I cut the DOM at 60" for just this reason so if by chance I wanted to change, I could easily cut off the joint and add a different style without wasting $100 in DOM. Just what I was looking for.
The reason I am making my own rather than just buying some is that I am putting this whole system on a Ford 9" (actually Lincoln w/ disc) and every detail has to be somewhat modified so I figured I should just make the whole thing rather than cut up some premade ones. I am going to be installing coil overs behind the axle and I am going to have a 6" drop, so there is no need to have a bend in the trailing arm for a spring perch.
It is all shaping up nicely and I totally appreciate all the help.

[71'tahoe]

They are the best way to go. As far as the bend in the arm are you talking about in the arm,that is there for the angle of the arms. if you were to draw a line from the center of the mount on the chassis to the center of the axle the angle would be pretty drastic. So to correct the pinion angle of the rear axle and to not have such a drastic angle the factory added the angle to the arms. You can try to run your home made arms stright from the chassis mount but then you have a huge angle.

[LEEVON]

Your new .250 DOM should be just fine. I believe you're overthinking a little bit. Gauranteed none of the aftermarket suppliers were thinking about flex and bushing wear when they built theirs (that's not saying much, but still).

The moment (bushings) are so far away from the load (spring perches) and at such a low angle there's not a lot of force on them and what is there surely wouldn't be affected much by flex. It's been awhile since I took a statics course, but I bet there's some engineers in here that could quickly do a moment calculation and show you the exact forces, my bet is they're low at that point.

Those look badass though, I'd love to have a set! Wait, I meant to say is ummm...they'll never work so just send them my way.

[Mike Bradbury]

The 9'' rear was cleaned of any of the old brackets and set up under the truck behind the OE Dana 60 that is on the truck now. Pulled the rear bolts on the leaf springs and lowered the truck frame 6 inches which is the ride height I wanted. The yoke on the diff was almost a straight shot from the tranny, so I mounted some mock up arms and they ran straight back to the 9" axle. Now I knew where to mount my new brackets. Remember there were no brackets on the 9" axle so I could set my pinion angle where ever I wanted to. Also I am running coil overs behind the axle so I will not have to have a flat spot on the arm for the springs which is another reason for the bend. I calculate that the pinion angle will be 2* at ride height. There will be three holes in mt coil over brackets for adjustment.