Front A-arm / bushing
 

For those of you who have upgraded your front A-arm to poly ( or other) bushings.... does anyone have a measurement of the A-arm's shaft diameter ( where it contacts the ID or bore of the bushing)?

---Wil Ferch

I've done these twice but didn't happen to measure them. There is some variance, especially if you don't clean and polish them prior to test fitting. If you have any specific question, I'd be glad to help.

Wil, today is your lucky day as I just happen to have a brand new pair in front of me along with my calipers: 36.15 mm :)

Steve and all:
Thanks for taking-on this question... !
BTW...is that dimension same for front and rear portions of the A-arm?

---Wil Ferch

They should be and I know they are supposed to be, but I can't confirm it because the arms I have in front of me have the bushings and bracket over it. The part I measured at the rear was the 5mm or so that stuck out past the bushings, and unless it tapers or something under it, you may want to double check my measurements first. Chuck Moreland would know best.

Yep. He's done the most homework of anybody on this board that i've seen.

http://forums.pelicanparts.com/showthread.php?s=&threadid=137833&perpage=20&highl ight=bushing&pagenumber=2

I second his place as an expert in suspension research.Everything chuck modifys has looked like top quality with an engineers eye to detail.

Elephant Racings bushing design definitly seems to be the best on the market so far. I've got a full set on order.
I just got the Sway-A-Way adjustable spring plates from Pelican and the first thing I looked at were the hard poly bushings.
They didn't seem like they would have even a slight 3-directional give going fast on a bumpy road, and cramming them into the semi-round torsion tube of the frame looked unfun.
The most important thing was the friction surfaces between the moving spring arm/wheel and the frame. Compressed poly doesn't slide well on steel, even with grease.

The issue is not that poly won't slide well ( even greased)....the issue ( for the front A-arms, for instance) is as the outer brackets are bolted-down over the bushings...that'll distort the ID of the bush such that the resulting diameter and/or "roundness" is not maintained. THAT causes the binding and squeeking. "Fitting" the bushings involves reaming/boring/creating a round bushing ID with the outer suspension clamps attached and clamped together...as it would be in an installed-condition.

---Wil Ferch

Will, I can get you an exact measurement as my right front A/Arm is in my basement with the bushings removed, awaiting paint prior to the Poly/Bronze bushings being installed.

Noel

Okey Dokey....standing by ...no hurry

---Wil

Will, if your set on using poly bushings, you might want to:

1)install/clamp them in place and then check the inner diameter for roundness.

2)measure the diameter of the end of the a-arm-where it rotates inside the bushing- to check for interference and grease clearance (how many 1/1000in are needed for grease to spread back onto the loaded side over big-air jumps).

3)hone/shave the i.d. of the bushing to get it round, and have an acceptable working surface(is this possible with poly?)

4)Then install the a-arms.

I think all this is covered by the E.R. bushings. The bronze sleeve liner prevents any i.d. distortion and the poly outer allows bushing flex for control (I hope).

Will, you can have my old S.A.W. bushings for free, to see how nasty and hard the poly is, but they do have a different diameter than the stock early and the later adjustable springplates. Mine were original I believe(35 y.o. suspension!) and I'll pay extra for something that lasts twice as long.

Wil,

The measurements are as follows using a analog micrometer.

Front and rear both measured 1.420"

I hope this helps.

Noel

Just as additional info.
Front and rear on mine ('74) measured at 36.474mm or 1.436" but I'm sure I could have more than a hundreth inch error in my measuring ability...
I have them off as I'm doing the re-bush as well.

Pat

Thanks all...
Right now just wanted to know if the front of the A-arms are different than the rear pivot points ( of the *front* A-rm).....thanks.

John... understand the install drill, and thanks all the same I won't need your bushings, but appreciate the offer.

---Wil Ferch

Having done these a few times, I've found the best way to get the proper fitment is to individually fit one bushing to one part of the A-arm and leave it there. This can only be done by first following a pattern of fitting the external od to the housing, be it the front or rear. It actually better to be slightly loose and then use an adhesive to then secure it. This will prevent any distortion of the id. Then remove the id in minimal amount, cool and test fit. A proper fit will fit securely with no "play" but allow easy turning of the bushing. Once these are greased, they will turn much easier. What you don't want to do is predrill to a size and expect if to fit perfectly. Once you oversize it, play and imprecision will be part of your suspension and you will have to start over. It's not that difficult, just takes time and patience.

Wil,

I agree with 89911, when I was fitting my rear bushings, I simply machined and then test fit them after they cooled. They were easy to spin on the spring plate but didn't have any play. You definatley want them be too loose than too tight.

Good luck.

Noel

Noel:

"Front and rear both measured 1.420 in. "

Pat S:

"Front and rear on mine ('74) measured at 36.474mm or 1.436 in. "

Chuck's analysis:

"The tolerance on the control arm itself is loose. Sample a pile of arms (I have), their size ranges about .015. The ID of the outer mounts varies even more, about .030. The polyurethane probably has a tolerance of .010 or so. Stack all that tolerance and you've got .055 or so, a very poor fit. "

How 'bout that guys? Your measurements agree with Mr. Elephant's findings! Good deal.

I used the same method as 89911. I just want to emphasize the "cool" part. The poly bushings expand a lot with temperature. I quenched mine in cold water for several minutes after each machine operation, before doing the trial fitting.

Talking about expanding with temperature. I found that the poly bushing is fairly stable with temp change. What really made me nervous was the expansion of the steel housing and control arm diameters. I had fitted the rear bushings to the sway away spring plates after installing the bushings in the outer housing as suggested above. Really nice fit at 50 degree F outside. Then when the arctic deep freeze set in in Michigan a few months back, I inspected the bushing in 10 degree weather and it was really loose.....lots of slop. I took it in the house to warm it up and everything was fine again. I worry if in 90 degree weather everything will be too tight. Not much can be done about it, but shows another disadvatage of the poly bushings.

Fredmeisater:
I really think the coefficeint of expansion is greater for plastics in general than it is for steel... meaning...the difference you're seeing is more likely to be due to the plastic...not the change in steel dimension.

---Wil Ferch