Tube Axle with Hairpins - Tech Question

[Rix2Six]

I read an article in the So-Cal catalog where they recommend not running hairpins with a tube axle because for the tube axle wont twist like an I-Beam will. How important is this? My car is set up with a tube/hairpin and I'm wondering if I should change over to an I-Beam.

[tommy]

I don't remember it as being a safety issue. No rash of broken hairpins. It was more an issue of suspension travel. 4 bar systems allow more travel than a hairpin system. The saftey police may disagree.

[lesabre59]

As i understand it, the tube will develop fractures over time due to the twisting effect which could eventually lead to a snapped axle.

[flt-blk]

On an I-Beam the axle will twist when one tire goes up and
the other goes down Left and Right hairpins are running in
different arcs. The bind is absorbed by the I-Beam.

Theory says a tube will not twist therefore causing extra
stress on the wishbones and possibly stressing the weld
betweent he tube and forged ends on a tube axle. There are
some good illustrations of this in the P&J catalog.

Personally I have seen both systems and never heard of a
tube breaking. Also realize you usually only have a
couple inches of travel things are pretty minimum.

Your call.
TZ

[Andy]

I have a friend who snapped the bottom half off of the perch bolt. The axle just sheared it off where the radius rod fit next to it. This allowed the radius rod to shift and so releaved the stress. I have talked to builders who admit that the shearing of the perch bolts is not all that rare. This is the same problem with wide mounted rear split radius rods. I've seen them sheer bolts and once actually tear a large chunk off the rear end where it was attached.

[Rix2Six]

Hmmmm... I think I'm gonna go for an I-Beam when I redo the front end. I'd hate to have a problem with it. Thanks for the info!

[Chopt 34]

I have read the same, but I also think it depends on how you have your front end setup and length of hairpins. The longer the hair pins the less twist you would induce on the axle.
Anyway, I am not disagreeing with the fellow members on the board. But here is a photo of my 32 with a dropped bell and hairpins, this has been set up this way since at least 1975.
I have to admit the travel is limited on this one, but it still rides nice.

[Jkustom]

[ QUOTE ]
As i understand it, the tube will develop fractures over time due to the twisting effect which could eventually lead to a snapped axle.

[/ QUOTE ]
Thats what Ive always understood too. When stuff cant move the way it wants to, something will eventually give so it can. But Ive have seen cars run around with a tube/hairpins.... -J.