Thread: Is This For Real ?

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I just read in my new Posies catalog something scary if its indeed true.
" Do not use tube axles with a split wishbone or hairpin raduis rods. You will break something and it won't be pretty."
This is written on page 8 as a "Posies do's don'ts and HOT tips.

Has anyone ever heard or expirienced this ? It goes on to say that tubes are too stiff and won't flex.
Whats all your thoughts on this?

This has been conventional wisdom for near 30 years. The cross section of a tube has much more torsional resistance than a solid beam (or rod for that matter). The notion is that since there's a single rear pivot point with either hairpin or split bone it requires more flex in the axle to compensate for the limitations on twist of the locating members. Since 4 bars have matching spaced pivot points front and rear, the supposition is that there is less twist at the batwing attachment.

There was an article in I believe Street Rodder 5 or so years ago that attempted to debunk this "theory". That being said, most folks don't want to temp the fates so follow the "conventional wisdom", though some have used a tube axle and either hairpins or split bones and not had a failure. Luck, or proof? Use your own judgement.

Drag racers used tube axles and split the radius rods but they didn't go over bumps or around corners at speed street rods followed the old drag race design which was ok for straight line driving. you can end up with terrible handling and bump steer on the road they can point ypu in the wrong direction real quick . the same goes for the rear suspension
I.ve had hair pins break
the i beam can flex (twist from one end to the other. 4 bars make more sense on a street driven car