IRS in a pre 68 beetle

Dear dubbers
Im only young but mighty enthusiastic,
Im looking to put a powerful motor in a lowered bug just wanted to get some opinions on if IRS is necessary, as i have heard mixed thoughts, if so what is the best way of going about it?
thankyou very much

Hi! Welcome to the forum. Please browse around and have a read, there are plenty of members' cars both with and without double-jointed IRS, and I'm sure that there are plenty of tech pages already on the subject. Do you have a VW at the moment? We would love to see pics of your car if you do.

I've driven both swing-axle and IRS bugs, and I have to say that the IRS is definitely a much better-behaved rear end setup. Whether converting to IRS is necessary or not depends entirely on what you prefer as well as where and how you're going to drive your car. For drag racing I believe swing-axles are usually considered to be superior. Swing axle rear ends can be made to handle quite well, especially if they're lowered sufficiently that they maintain negative camber most of the time. The unsettling behaviour of swing-axles only occurs when the rear end is unloaded when heading into a corner, usually caused by lifting off the throttle or braking deep into a corner. When the rear end lifts high enough, the rear end goes into positive camber, which can lead to snap oversteer. I drove my swing-axle Beetle close enough to the limit to experience this several times, and I was always able to predict when the rear end was going to come round and catch it with opposite lock. Whether this kind of behaviour from your car is acceptable or not is up to you.

Swing axles are IRS as well - IRS means 'independent rear suspension'. ALL air-cooled VWs have IRS.

The newer design is called the 'double joint' rear - this was the phrase VW used in their spec sheets. For Australian Beetles it was only fitted to Superbugs, post '68 semi autos and the '76 torsion bar Beetle. All the rest were swing axles.

You can convert a swing-axle rear to double-joint but the price might make you stop and think - ring Vintage (02) 9789 1777 for a quote. If you planning on some serious circuit racing, you might consider the conversion; then again, VWs raced at Bathurst (and won their class in '63) with swing axles and drum brakes. It's all how they are driven. For street driving, where the urban speed limit is mostly 60 km/h, it's just not necessary. Swing axle Beetles also sit on 110 km/h on the freeway with no problems. You won't ever get in the 'rear out' oversteer condition unless you are showing off, or going far too fast for the conditions, or otherwise driving foolishly. It doesn't really 'snap' oversteer, but rather tends towards that behavior from the start. It is easily corrected with opposite lock. It's a different driving technique from modern FWD cars, but once learned it becomes instinctive. Many VW drivers actually prefer it to the understeer common in modern cars. It requires some caution in wet or greasy conditions until you are familiar with the handling.

You can fit a camber compensator to eliminate the 'tuck under' and make the handling more neutral. Talk to Greg Mackie - he raced a swing axle Beetle at Bathurst in '63 and races a swing axle Beetle now.

Try the articles at Aircooled.net you will find them just what you are looking for. Basically Swing axle wheels will tuck in at the bottom as you corner hard unless you do something about it. You could fit a camber compensator (easiest option) or you could fit straps that limit the downward travel of the axle. Both work effectively. I recently converted my pan to IRS and it costs! 300 to get the pivot boxes in, 200 for the diagonal arm and different spring plates and torsion bars, then you need a different gearbox and might need to replace the CV too. just think about what you are looking for.

A lot has been said about the pros & cons of different rear suspensions on a VW. The fact is, the VW is HEAVIER in the rear, therefore that's the end that will 'flick out' when the adhesion limit is reached. Whatever your preference - and it's all about preference - the same thing will happen.

My GT-3 Porsche has a very well engineered suspension, however when that 'limit' is reached, guess which end 'flicks out'? The rear end.😵‍💫 It does it beautifully, though.👍 Cars with close to 50/50 weight distribution are much more likely to be 'neutral' (read - boring). The important thing is to learn to master what you have, and enjoy it.😁

Cheers, Greg

Greg what GT3 do you have??? Jealous much?🙂

2004

Very jealous of that GT3 Greg. I understand what you're saying about the cars being fundamentally tail-heavy, but I have to say that my S-Bug will hold it's line and keep the rear end in through corners and speeds at which my old swing-axle 1500 would be sideways all over the road, on the exact same set of tyres. I bet the handling and grip limits of that GT3 raise the bar by quite a long way again above the Superbug!

Aha! now you're bringing tyres into it. 'The exact same set of tyres' is very important, as you were comparing 'apples with apples' - something that many neglect to do, waveman.👍 The GT-3 has 295x30x18 rear tyres, enough rubber to keep that heavy rear-end held down - with the help of a very well designed rear suspension, and a little downforce from the rear wing.

From my experience (over the last 50 years) the swing-axle rear end can be made to work well, but it needs a bit of perseverance (or stubbornness). I suppose when I first started to tame the swing-axle rear end, there was no alternative.:no I had to make it work, or else!🤪