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Posted by: stugray Jan 25 2011, 11:28 PM

I took the trailing arms out of my current car for repairs to the suspension ears.
While they are out, I figure I should:

Clean boxes,
Reinforce with weld plates,
powder coat ( or Plate? ;-),
Replace rear bearings,
Replace rear bushings,

While I am at it, I should do the axles:
strip & paint axles,
replace CVs,
replace boots,
Get new bolts.

Then the rear calipers....
Clean,
rebuild kit,
send to PMB performance...?


Here's the rub..... I have multiple complete sets of everything mentioned above for one car.
Four rear trailing arms
Four rear axles
SIX rear calipers....


For efficiency's sake it seems I should do all of them sets whiles I's at it.

Should I do them all and keep for myself, or..... assume that I can recoup some of my costs by selling/trading the extra sets here after they are rebuilt?

Group buy in NOCO area on some cleaning, & powder coating?
I think I would need to buy 4 new bearings for the arms and 4 CVs to make four good axles...

Stu

Posted by: McMark Jan 26 2011, 12:08 AM

Do them all if you have the means.

Skip welding on the reinforcement plates. They're more dead weight than anything else and there's a lots more effective places to put that weight than on the trailing arm.

Posted by: avidfanjpl Jan 26 2011, 12:13 AM

On that subject of reinforcing stock 914 trailing arms, Mark, what is the risk if you run a 914-6 without reinforcing?

I never heard any story of stock ones in good shape ever failing. I am not talking about rusty or bent ones, just totally stock ones in good shape.

I hear all sorts of stories. What have you heard? Just that it is dead weight?

I am really interested in what you say.

Thanks!

John
avidfanjpl

Posted by: stugray Jan 26 2011, 01:17 PM

Mark,

"They're more dead weight than anything else"

So the boxes sold by AA are useless? They dont look very heavy.

How about what Tangerine racing does to their "upgraded trailing arms": 'Welded Internal and External Reinforcements to eliminate flex and twist'?

Is that different from just welding the box on the outside?

I saw on another thread around here recently, that you can reinforce these by welding addition tubes in just like the one that is already in there? ( I think for brake adjustment? ).



John
avidfanjpl

Do you work at JPL?

Posted by: Eric_Shea Jan 26 2011, 01:25 PM

Do this... it's easier, lighter and stronger:









Boxed arms only add about 4-6lbs each if I recall and they stiffen by around 40%. Not a bad tradeoff but these will be stronger and weigh nothing.

I heard about an old racer that was doing this. We offer it as a service now but feel free to plagerize it... I didn't invent it.

Posted by: SirAndy Jan 26 2011, 02:05 PM

Are you running sticky race rubber slicks?

If the answer is no, i don't see any need for any trailing arm reinforcement.
If the answer is yes, the additional tubing is the better choice over the clam shells.

Posted by: stugray Jan 26 2011, 03:25 PM

I will eventually have new Hoosiers, but the first year will probably be used racing tires.

So I'll do the tube method.

Thanks Eric!

Does anyone have a picture of one that has failed?
I would be interested in seeing that.

Posted by: Loser_Cruiser Jan 26 2011, 03:32 PM

Eric- So are you still doing trailing arm services? I thought I read awhile back that you stopped.

Posted by: Eric_Shea Jan 26 2011, 04:07 PM

I stopped doing 5-lug but I can still do the control arm mods. I seemed to find a reliable machinist as well so... some 5-lugs may trickle out. We'll see.

Posted by: McMark Jan 26 2011, 10:06 PM

There is a VERY long thread on here somewhere which includes FEA for stock and modified trailing arms.

Most people don't need any stiffening on their trailing arms. Stiffen your chassis first, second, third and fourth.

Posted by: strawman Jan 26 2011, 11:46 PM

Gotta agree that the trailing arm clamshells add a lot of weight. I welded on a set, compared them to a spare set stock ones and was amazed at how much heavier the reinforced ones are. Pretty porky, and unsprung weight at that. I ended up plagiarizing Eric's suggested tube reinforcements (thanks!) on my spare set...