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Bruce's way of lowering is correct, you take some of the preload out but there is a suspension softening that goes with it.

FJ's idea I have never heard of before but if I understand it correctly it acts the same as a lowering block on leaf spring cars. Very creative and I guess it must work.

I seem to remember that some guys raise the rear torsion assembly in the car but that is a lot of work!

Yes, you can reindex. That's the right way. But lots of guys get indexing wrong (inner and outer splines) which is why dropped spring plates, adjustable spring plates, etc., were invented.

The simplistic adapter plate I described was used back in the 50's on 356's and Bugs.

Hmmm... ok. Like to see a pic of that.

I also don't really get drop spindles. From everything I've read about torsion bar front ends (and roll centre), lowering is often to the detriment of handing.

Drop spindles actually work very well and don't change front end geometry.

I prefer to lower our Ghia with tires, 50, 60, and 65 series.

FJC

Gold. Love it. You haven't answered my query about roll centre though. Allen Staniforth describes the roll centre as being 'on the ground' with a torsion bar from end (beetle or Porsche) at standard height.



Page 46. So I might be misunderstanding, but basically, if you lower the front beam... the front roll centre ends up lower than the ground... Ouch.

Which is why I guess, so many porsches/early VW race cars appear to be reaching for the sky up front. It also explains why swingaxle beetles were so prone to rolling over with a higher roll centre at the back and all the weight there too.

On a pure trailing arm suspension, (like t1 front end) the roll center is at the ground regardless of ride height.
...and the lower the car, the closer the cg axis is to the roll center.

Also note that the instant the inside tire lifts, the roll stiffness is infinite on that axle, so the roll center is ~out of play.

Front roll center is at ground level on a VW/Porsche beam axle.

And the rear roll center is right about middle of the transaxle.

A thousand words is worth a picture.

Do you have some kind of three stage setup with irs as you have with swing axle? Live the post!

I didn't go into a lot of detail on the IRS because we think it's good the way it is.

We run stock torsion bars, half a degree negative on the rear, and zero toe. We run no rear swaybar to add the safety of understeer at high speed, and we have 16mm and 19mm rear bars. The image above (Daytona infield) shows the results of no rear bar. Even the 16mm rear bar would have kept the front tire down.

FJC

Thank you so much!

So what are your opinions on lowering an IRS rear end? If I am looking to lower purely for handling on a 74 standard beetle, does the lower cg make up for the loss of upward suspension travel (and as such, likely requirement of stiffer bars)? Also, you seem to recommend adjustable spring plates due to their adustability, but other than that, are their benefits/disadvantages to maintaing stock down travel (as opposed to reindexing where you increase your down travel by however much you lower)?

So what are your opinions on lowering an IRS rear end? If I am looking to lower purely for handling on a 74 standard beetle, does the lower cg make up for the loss of upward suspension travel (and as such, likely requirement of stiffer bars)? Also, you seem to recommend adjustable spring plates due to their adustability, but other than that, are their benefits/disadvantages to maintaing stock down travel (as opposed to reindexing where you increase your down travel by however much you lower)?

Adjustable spring plates are the next best thing to coilovers to balance or move weight around in the suspension. See the jacking screws on our '73 Super LeMons bug? We actually get all our lowering from 50-series tires. Raise the rear end to counteract understeer. Lower to really plant the rear tires in a corner.

FJC

FJCamper wrote: ↑Mon Aug 06, 2018 2:39 pm Adjustable spring plates are the next best thing to coilovers to balance or move weight around in the suspension. See the jacking screws on our '73 Super LeMons bug? We actually get all our lowering from 50-series tires. Raise the rear end to counteract understeer. Lower to really plant the rear tires in a corner.

FJC

So just to be kind of clear, you realistically dont recommend lowering a beetle (outside of adjustable plates for finer tuning) as far as performance tuning suspension goes? My largest concern is a bit better aero characteristics tbh (already planning on a front damn, but I have a standard I am building, so flat windscreen), but I dont want to do anything detrimental to handling.

I believe we're talking about two different things, street vs racing applications.

For street, you can do whatever you like, because weight jacking, suspension balancing, and quick ride height changes are not a big factor.

Just lowering a Bug 2" front and rear really transforms it.

FJC