Swing Axle Vs. IRS

[johber41]

Can someone in the group give me the cliff-notes version of the difference between a Swing Axle and an IRS, which I am assuming means Independent-Rear-Suspension. I see it mentioned many times in old postings and in technical explanations but I am not sure of the differences when it refers to VW buggies. Thanks for tolerating my lack of VW knowledge!

[GregR]

I'll take a shot...

The swing axle does not have diagonal trailing arms and only has the spring plate, axle tube and transmission supporting the rear of the car. The axle tubes provide lubrication from the gearbox connection at the spring plate. A swing axle can "tuck under" during hard cornering...but look pretty cool if you want to slam the buggy.

The IRS has diagonal trailing arms and CV joints. The result is that rear end is supported by the trailing arms and spring plates allowing the drive axles to have that one job...getting power to the wheels.

Which is better? That'll depend on who you ask. It seems off-roaders generally prefer swing axle setups as the have a bit more travel.
On road, the IRS seems a bit smoother and doesn't suffer from wheel tuck. Again, it depends on who you ask.

Technically, both are independent suspensions.

[johber41]

Thanks Greg, that helps plenty. I then understand that the classic VW setup is a Swing-arm system with the transmission and trans-axles hanging from the rear fork in the frame. So an IRS system is something found in custom builds like rails. Thank you sir!

[BrianB]

Swing axle was in bugs until late 1968 when it was changed to IRS for the 1969 model. All bugs after this point(US delivery) had IRS transaxles. So if you would rather have IRS in your buggy go out and find a late model pan and have at it or convert the one you have.

[johber41]

Thanks guys!

[johber41]

I want you guys to know that you have motivated me to take a better look at these machines when I see them accumulate at local car meets. Today I went to Clear Lake Shores for the regular Saturday night car meet and heard a couple of the guys laughing when they saw me looking under their cars to see the suspension differences. A great many questions were answered after studying the IRS system. My buggy is the first VW I have ever owned. In years gone by, I used to wonder why some of the beetles and buggies had the wheels leaning so far out (practically on a 45 degree angle) making it look like they were running on the inside wall of their tire. Now I see how the swing axle affects the angle of the rear tires to the pavement, especially as the cars are lowered to the ground. I often wondered if the cars that had the tires on such a lean would wear the rubber on the inside of the tire unevenly and wondered if the lean would starve the wheel bearings of lubricant. Some guys at the meet that have cars with this style explained that the turning of the axle inside the rear axle tube forced lubricant to the wheel bearings. That lean still looks extreme to me, but I guess it gives them a look they like in the older models. My knowledge grows!

[ManxManiac]

Thought I'd add my 2 cents worth... for my driving style, both on & off road, I prefer the swingaxle rear suspension.
Main reason... simplicity.
A swingaxle system consists of an axle on each side & an axle bearing on each side.

The IRS is much more complicated. It has an axle on each side, a total of 4 CV joints & boots, a CV flange on each side of the IRS transaxle & a CV stub axle on each side in the trailing arm, plus the stub axle bearings on each side. However, if you break an axle or CV joint, it is easier to replace them or remove it altogether for flat towing.

The IRS supposedly rides better, but I feel my swingaxle rides pretty well too. I've been everywhere the buggies with IRS have been & vice versa!

A swingaxle pan can be modified with the IRS pivot mounts or a IRS pan can be run swingaxle!

Tire air pressures are very important on a f/g buggy too. I run 10psi all the time in P235/70R15s mounted on 8" wide rims & on the front, it depends on which set of tires/rims I have on... anywhere from 8 psi to about 12 psi.

So it all comes down to personal preference!

[johber41]

Thanks Manx Maniac Michael. What a difference understanding the generations of drive trains makes when you are looking at parts on-line! You hate to commit to a part for an IRS trans-axle when you are running a Swing Axle. Like you said, a lot less parts on the Swing Axle.

John