Swing Axle vs. IRS

What is the difference between a Swing Axle and IRS regarding handling and general ride quality, if any? Is one preferable over the other?

Well, Goofy, you're going to get a ton of answers to this question. But none will be as short as this:
IRS is better. In every way.

John is right; IRS units have better handling. Still, though, swingaxles are preferred by drag racers because of their almost bulletproof qualities. They are very sturdy and are simpler so they have less parts to break. In my build I chose one to stay true to the 356's original design, although that's just my personal preference.

"Swing Axle" pivots the rear wheel up and down in an arc starting at the side of the transmission. The arc is described by the length of the wheel's drive shaft, so when it (the wheel) goes "up and down" it is actually pivoting around that arc. When looked at from the rear of the car, as the wheel goes down, the top moves outward while the bottom moves inward as it "arcs", thus allowing the tire contact patch to shift back and forth across the surface of the tire as the wheel moves up and down. Not all that good for positive handling of the auto (it sucks, basically). The driveshaft is inside of a torque tube and is a straight shaft out to the wheel.

IRS, on the other hand, has the rear wheel hub attached to the chassis via a trailing arm that is designed to pivot up and down from forward (and slightly inboard) of the wheel hub. This design allows the wheel to move straight up and down, thus, keeping the tire contact patch flat to the road surface at all times. The drive shaft must now be articulated via two (one on each end) constant Velocity (CV) joints (or wicked-fancy universal joints) because the transmission drive point is held stationary, whilst the wheel is allowed to move up and down, thus necessitating the dual CV joint design.

gn

If you have a choice, the IRS is the only way to go, and it can be made to perform wonderfully with a few fairly inexpensive up grades.

I'm sticking with a short axle conversion, swing axle: mostly because I very much wanted to mimic the original, partly 'cause I'm too lazy to install my adapters and convert to IRS.

In a previous post I was begging for info (Gordon hook me up with the Mother or all web sites) on "Z" bars, and camber compensators and limiter straps and the like, just to get the swing axle to act civilized under spirited

The reason I asked is because the car builder offered a swing-axle for $500 additional, touting that it was rare and that I should definitely consider it instead of IRS. To me, "rare" says parts are hard to find, and any maintenance chores possibly harder, unless one is a mechanic and has tons of time and garage space to boot. I am/have neither of these. I want a unit that works, is easy to repair, is reliable for a long period, gives good handling and good ride for ordinary street use and PCH-type quick driving. Sounds like IRS is the way to go.

Jim Bob, I've never heard that expression, "bravo sierra." Is that an Oklahoma coloquialism? Since the first letters are "B.S." I am going to assume that you mean something like sales pitch, a good place to apply caveat emptor.
John as in Hoss

John-

Radio call letters, my man:

A= Alpha
B= Bravo
C= Charlie
D= Delta

Echo, foxtrot, gulf, hotel, etc., etc., until you get to Romeo, Sierra, Tango, and so on.

I'll let you figure it out.

Barry-

Extra for a swing axle? I'm going to try to sit on my hands here, but I'm really confused by some of the stuff you are asking. I'll say this though- the only reason to get a swing axle car is that they were original on A model 356s. By every functional measure, they are inferior. I've had both on speedsters.

If you order the base JPS, or Vintage- it comes with a swing axle. You have to specify, and /or pay extra for IRS. IRS Beetles went into production in '69, long after the VW boom was fading badly. There was hundreds of thousands less IRS cars produced, compared to swing axle cars. Rare swing axle cars? Well.... Caveat Emptor.

And IMHO, either one is about equal in strength, serviceability, reliability and longevity.

The BIG difference, is that the Swing Axle types cause the rear end to break loose on hard cornering and then you watch as the rear comes around the side and passes the front.

The IRS can do this too, but it is much more predictable and quite a bit harder to make it let go in the first place, so, basically, the IRS is a MUCH better handling rear suspension.

Oh, and your builder is giving you a line of Bravo Sierra on the Swing Axle thing. Sounds like he has an IRS kicking around and would have to scramble if you want a swing arm to look "authentic".

Barry, with the usual builders it's always the other way around; the IRS is an option and will cost you more. If this builder is giving you an IRS in his base price take him up on his offer.

Sounds like Bravo Sierra. $500 extra for a swing?

An added thought . . . I only get one per day . . .

If this kind of thing is happening already, and you're at the early stages of choosing a platform for the build, I would highly recommend NOT going through with the rest

Exactley my thoughts... bail now. If they are scamming you early, then this build can only get worse.