Looking for opinions on strengthening the rear trailing arms. Car is a '70 with a 2.7 that will be street legal but used for track days also. Ed914.com has a very nice set of arms, powder coated, new bearings etc, but have not been strengthened. My question is have any of you had trouble with broken/cracked arms from agressive driving ?

I think Chris Foley and Eric Shea both offer a method where holes are drilled and tubes welded in to strengthen them. The Porsche method from the 70's apparently doesn't do much.

Do the arms flex that much to where they need reinforcement? What is the benefit of strengthening them?

More accurate suspension. They definitely flex and when they do, the tire surface changes it's relationship with the pavement. Handling suffers. It's a 10/10ths thing I guess...

If you absolutely need to win a plaque for your wall, go for it. If you just wanna drive fast, don't bother. That's my perspective.

You probably need wide tires & wheels to put enough load on the arms to flex them significantly.

Jim

If you leave them stock and bang something hard with a rear wheel, the trailing arm bends and you replace it. If you reinforce them and hit something hard with a rear wheel, the chassis bends and you have to....?

Sorry should have included that it is a wide body, and my track tires are 245/45-16's. I just remember reading somewhere that cracked arms were a problem. Thanx for all the input.

I'm strengthening mine because I have them off and was doing a lot of welding. Skip the clamshell method, especially for a track car. I read up a lot on the unsprung weight. Do tubes!

I posted pics and measurements on my build thread recently how I did mine. Purchased 24" of 1" steel tube and a step bit. Took about 45min start to finish, and cost under $20.

So you just add two pieces of tube that ties the sides of the rear arms together?
Any special locations for them or just evenly along the length of the arm?

I have lotso' plaques but never had the need to strengthen the trailing arms.....but I was only running 10 inch slicks. Spend your time/money on low striction trailing arm
bearings & good shocks instead.....just my .02
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That's Eric's method not mine.
My stiffening process involves splitting the trailing arm and installing a bulkhead.
A corner gusset between the tube and body takes care of the crack sensitive area.

Thanx Doug n Rob, thats exactly what im going to do. Ive reached out to socalandy so i can get a look and some measurements, as he has already done it. J P, yes i have already bought bilsteins and coil overkit. Looking forward to putting faces with names on 3/2 at Phoenix club.

My home AX venue (PIR south pits) is rough as a cob......double vision rough.
I realigned at the start of each season. Any "flex" in the trailing arms must have been temporary as it held the previous alignment very well for 6-8 years.

The only place I had any cracking problems were at the bottom of the rear shock towers which (I was told) come with the territory when the rear spring rates are over 200lb.....I ran up to 300. Down tubes from the roll hoop to the shock towers tool care of that problem.
I am not adverse to mods......when they are meaningful.