Trailing arm/alignment question Options

[Mueller]

Hopefully this makes sense to someone besides me (IMG:style_emoticons/default/smile.gif)

Pictured below is a bad representation of the trailing arm shaft and the inner trailing arm ear.

When adjusting the alignment on the trailing arm which side is tightend down first? (mount or inner ear)

I cannot see how the face of the trailing arm shaft and inner ear are perfectly flat against each other, if the outer mount is moved and tightened so that it mates perfectly flat with the shaft as well something has to give.

The 3° in the picture is just number I came up with...but ideally, one would want 0° on both planes where the mounts mate with the shaft.......with the current design, both mating surfaces can be perfectly flat with one another, but the alignment more than likely will not be correct??? IMHO

Opinons?? / Flames??

[Dave_Darling]

The outboard mount stays attached to the trailing arm. When you change the alignment, you move the outboard mount around with respect to the rest of the chassis.

Does that answer your question? ...I think that the above implies that the effective answer to your question is "inner is tightened first", even though that is not necessarily the case...

--DD

[HotRod]

Mike, I agree. I would guess that the inner tab would have to be aligned to whatever camber the rear trailing arm is set at. I would also imagine that using the rubber (stock) bushing that this difference is made up for in the play provided by the rubber bushing. Using solid bushings which would be less forgiving would aggrevate the problem and probably accounts for why I have broken the bushings at that point on my race car. Maybe Weltmeister has considered this because I've noticed that their rear bushings are less solid or hard than the ones that they make for the front.

Which brings me to another point, wouldn't this be even more critical if one were using needle bearings instead of bushings? Also, as you are aware, I'm looking at moving the outside pivot point back. If I were to do this by extending the ear that provides the outside pivot point, wouldn't this allow even more flex in the outside pivot point and make the problem even worse? Can the ear be reinforced enough to minimize flex if I go that route? Or, would it make more sense to move the suspension pick-up point rearward instead of extending the ear? I guess as far as the inside point is concerned, the best that I could do is to estimate the angle that would be consistent with the camber that I intend on running and set that point at that angle. Did that make any sense to anyone but me?

[Brad Roberts]

Mike,

Your correct in your thinking. The inside of the crossshaft does not sit flush on the control arm ear ( I see this when pulling apart a plastic bushing car or a rubber bushing car) I will say: I think the ear will twist and bolt up flush with the cross shaft.

My plan is to tighten the inside one first on Ron's car and then tighten the outside mount last, then adjust toe. At rest the control arm is almost 0 toe. Its starting to look like the mono balls are the way to go. They would "angle" and move around to mount flush on the ears at all times.

B

[Tony C]

Mike, I think what will happen as Brad said is that the innear ear flexes enough to mate the two surfaces. Not ideal...but it could get too triack to fix that issue.

-Tony

[Mueller]

I think I have the fix (IMG:style_emoticons/default/smile.gif)

Tony and Brad,

I'll draw up the design on Monday to show you two....it can be used on cars using poly bushing and of course roller bearings......

[Mike T]

Its starting to look like the mono balls are the way to go.

I've considered adapting monoballs to the 914 rear trailing arms but was unsure what the axial thrust load requirement would be and if there were any monoballs that would suffice.

Mike T

[cha914]

here is a good thread on pelican where a guy posted alot of pics of his setup...look about halfway down the page:

http://forums.pelicanparts.com/showthread....20&pagenumber=2

[ChrisFoley]

I have always bolted the outer ear onto the shaft first, even before attaching the arm to the car. The sheet metal at both ends will flex enough to compensate for any slight misalignment. Ideally, spherical bearings would completely eliminate bending loads at the ends of the pivot shaft. Some good pictures of a custom monoball installation are available at the VCI website.
I make Delrin bushings for the rear, along with a heavy duty outer mount, which works out very well. See my website for a picture of the mount. Also I rework the trailing arm and shaft so the alignment is perfect. The shaft pivots freely, with no play and no drag or side loads.

[Jeroen]

Hey Chris,

Can you put your website in your membersprofile
(click "my controls" in the menu above)
and / or post it here please...

I'm sure I have it somewhere, but can't find it right now (IMG:style_emoticons/default/unsure.gif)

Didn't you also have monoballs for the rear upper shockmounts?

cheers,

Jeroen

PS the fab work VCI does looks sooooo nice (IMG:style_emoticons/default/biggrin.gif)

[ChrisFoley]

Yes, I have kits for the rear strut towers. A 3" hole saw and a mig welder are the only special tools required.

I plan to raise my rear suspension pickups using the VCI photos for reference.