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Reply to "IRS vs Non-IRS"

As Robert, Bruce, Stan, Ed and others have said- go irs! Not only is handling superior, the ride is a little more comfortable as well. If you do narrowed trailing arms now is the time to decide on whether a brake upgrade is in the cards, as discs (or bigger type 3 drums and shoes) will space the wheel mounting surface out 1/2-5/8" and that needs to be figured into the mix.

Right now on my older Intermeccanica body (with VW pan) I have short (swingaxle) torsion bars, cut down swingaxle spring plates, Beetle drums, stock irs trailing arms, late 6" Fuchs with 1" added to the inside so they're 7's (a la '67 911R) and 195/60's just fit, there being 1/8" spring plate clearance and less at the fender edge. I was hoping to use 205's but they wouldn't go. If you use adjustable spring plates you'll have less room, and if you go with irs (longer) torsion bars the early double spring plates will limit the tire width as well. The later single spring plates are more than strong enough, so that's the way to go. I never did have an irs torsion bar cap in my hands to weigh, but they are significantly heavier as well

For those in the conversation- there's no need to modify an irs pan for swingaxle; it's just a matter of ignoring the trailing arm brackets, using the shorter torsion bars, appropriate spring plates/caps and installing the transaxle. An irs pan under a swingaxle Speedster will have the trailing arm brackets as long as nobody's cut them off.

I used swingaxle torsion bars and spring plates to save weight- the shorter bars are (iIrc) almost 1 lb (each) lighter, double irs plates weigh 2300 grams each, singles about 1700 g's and my cut down spring plates just under 1,000 grams (each!). The adjustable spring plates from Sway a Way I have weigh about 2550 (sorry, don't remember the exact numbers) and just under 2600 grams- they are really heavy!

To modify swingaxle spring plates for irs isn't that hard; they need to be shortened, narrowed (top and bottom) slightly (or you'll get less suspension travel) and new holes and slots drilled. And of course they have more holes- they're mine! 

lightened spring plate- cut down for irs

 

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Last edited by ALB
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