IRS vs swing in the quest for 200 mph

[WickedWagens]

Our land speed races for this year at the Bonneville Salt Flats were all canceled due to water over the course, so I'm starting to plan for next year. My question is which setup will be better for high speed? I keep running into fulcrum and axle wear with my swing axle. I just don't think they were designed to run 170+ MPH. So would IRS be up to the task? Better bearing setup, CV joints, etc? What are your thought on this? I have to switch to 5 lug wheels anyways, so I might as well tear things apart.

[slayer61]

Mind you, it's drag racing, not salt flats, but Dave Folts wouldn't have gone to the trouble to convert a IRS bus trans for swing axle use, if it wasn't of value. Then again, he had no fulcrum plates to deal with either...

Swing bus trans.jpg

[WickedWagens]

Not exactly apples to apples. He was trying to find a way to add strength. Going to a bus trans helps with this, next is the CV joints. He replaced those with U-joints and converted back to swing axle stubs for the bearing housing. I'm not too worried about strength. A well built IRS trans will be ok and I am pretty sure the wheels will spin before I have to worry about hurting an axle. No shock load of launching like drag racing. Just high speed is where I am concerned with.

[richie,uk]

Personally I think IRS is way to go, if only for keeping tyre flatter on surface to help with traction to get to your goals. I have only been 160mph on stock IRS set up but it seems much more stable to me, I have built a few fast swingaxle & IRS cars over the years and would always choose IRS when possible, the removal of issues like fulcrum plate wear is just another bonus

cheers Richie

[Ol'fogasaurus]

I would also add outboard connections from the suspension to the outboard part of the pan to help reduce any twisting at the center connection to the pan (distribute loads when necessary). The VW pan is a tunnel style of pan (where most of the strength is) but the body mount area also needs some support for load transfer when needed.

Just a thought!

Lee

[Chip Birks]

I'm basically planning to convert anything I ever build to IRS at this point. I'm doing a bus now, my bug will be next then probably another bug when I get to that one. I'd way rather have bearing wear happing outside of my transaxle that inside. IRS has 2 big nice bearings supporting the stub axle instead of the single one that swing axle cars have. Brake damage from leaky seals goes away too. There are a few more components, and they do take up some space back there, but I think it's probably a worth while venture.

[WickedWagens]

I had a chat with Mike Fischer that runs the Fastest Ghia in Land Speed at 190 MPH. He basically confirmed my and some of your thoughts, he is even running regular type 1 CVs. The 930s aren't needed because of lack of traction. I was going to run type 2 parts from a Thing for strength, but he said his type 1 parts have held up fine. Now to see if it can be done without pulling the body off.

[Ol'fogasaurus]

I had a chat with Mike Fischer that runs the Fastest Ghia in Land Speed at 190 MPH. He basically confirmed my and some of your thoughts, he is even running regular type 1 CVs. The 930s aren't needed because of lack of traction. I was going to run type 2 parts from a Thing for strength, but he said his type 1 parts have held up fine. Now to see if it can be done without pulling the body off.

For what it is worth:
The bus trans uses larger dia. (and stronger) CVs than a stock Bug IRS does. A stock bug trans could be used but you would have to convert the stock bug CV to the bus CV mount, not hard to do and takes just a short time to accomplish. You would also have to change the rear axles to the longer/stronger axles for potential hard and soft loading as you could get at the higher speeds.

At the speeds you are talking about you need the IRS setup (no swing for sure) just for potential loading problems at those speeds such as any bouncing around or spinning out. Also, would an aftermarket Truss/Kaffer bar conversion be strong enough to handle any potential problems you might get into (make sure the outer torsion tube mount is attached solid to the body from both the top and it's bottom. The bottom attachment is almost nil.).

While I haven't been that interested in going fast, I have watched runs on the Salt Lake and seen some of the spinouts that have happened. It can be bumpy and also there is the potential airflow problems that could happen.

Plan ahead but it also takes times to think about everything so be prepared on that also (I'm caught in that myself).

Lee

I forgot to mention the change to the bus stub axle.

Lee

[Chip Birks]

I had a chat with Mike Fischer that runs the Fastest Ghia in Land Speed at 190 MPH. He basically confirmed my and some of your thoughts, he is even running regular type 1 CVs. The 930s aren't needed because of lack of traction. I was going to run type 2 parts from a Thing for strength, but he said his type 1 parts have held up fine. Now to see if it can be done without pulling the body off.

When I was buying stuff for my bus, I decided on going the type 2 CV route only because there are stub axles made that allow you to use a standard 5 lug bug short snout rear hub assembly. Conversion parts are out there to do whatever you want, the empi stubs and output flanges fit well and are pretty tough looking parts. A little more costly than hunting down OEM thing stuff down, but not too bad.

[Bad Bob]

I think you’ll be way ahead to separate the pan and body to weld the pivots in. Not much room in there.