Alex,
Remember when we test fitted my 18x10 et 47 to your trailing arms last year ? We took a measurement, and when I did my 944 NA ebake setup to my stock '74 trailing arms, the conversion ended up being 22mm wider, which was the same amount as your AL arms.
So both conversions increase the track by 22mm, benefit of yours is lighter weight.
All,
Here's some calculations we can work with. These were measured when I did the conversion.
Application is starting with irs beetle rear drums and ending with 944 NA ebrake conversion with 944 turbo rear disks (299x24mm) and 4 piston brembos.
Stock beetle 15x4.5 wheels (et34, overall width = 5.375") have 4.03" of space behind the drum mounting face (backspacing) and 1.35" sitting out towards the fender from the drum mounting face.
Now after converting to the early AL arms, or doing the 944 ebrake conversion, you increase the width per side by 22mm. Say you are using a 17x7 et 52mm. The overall width of this wheel is 8" so that breaks down into 6.05" backspacing and 1.95" towards the fender.
With the increase in width per side of 22mm, the outside of the wheel ends up sitting (1.95" + 22mm/25.4mm per inch - 1.35") = 1.47" further towards the fender than a stock 15x4.5 wheel on drum brakes.
There is definately 1.5" of clearance with the stock wheel so fitting the 17x7 et52 on early AL arms or converted IRS arms will work, as confirmed by HOT66.
This assumes the tire sits flush with the outside of the wheel.
Sandeep
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