Recommended clearances for 944NA rear brakes

[matara]

Hi,

I'm stripping down my 61 Cabrio on an IRS chassis so I can send the body off to be painted. Before I do so I need to fit up the Porsche brakes and see how far my wheels sit out. I have 944NA rears with S2 fronts (is this bad to mix early 944 rear with late brembo fronts?) My wheels are

front: 7.5' x 17 with ET50
rear: 8.5' x17 with ET55

The brakes went on in 10 mins couldnt believe how easy it was. I dont have a spacer on the hub yet, but to my surprise when I tried putting on the 7.5' wheels, they seemed to fit without any rubbing and plenty of clearance in the springplate area and the bump stop!! I then put the 8.5' on, and this seemed to have plenty of clearance at the springplate, but it was pretty tight 1-2mm next to the bumpstop.

In order to work out what size spacer I will need can anyone tell me what sort of clearance I should have between the springplate and the inside of the wheel, and the bump stop and the wheel. I can't see any other suspension parts even coming near, is there any other places i should check?


Pics:

Here is the 84NA brakes in place on the IRS suspension:-




First up the 7.5' wheel. This is the springplate clearance, about 28mm gap between the wheel and the springplate



Again with the 7.5' here is the bump stop clearance, about 15mm



Lastly with the 7.5' here is the side profile against the body. I think it might just fit under the guard if I put it back on the ground:-




Now with the wheel I intend to put on the rear, the 8.5' ET55. This is the springplate clearance which is about 15mm



With the 8.5' wheel the bump stop clearance is only about 1mm. I think I might need a spacer to bring the wheel out a not more. Any idea how much I need to bring it out?



Lastly here is the body profile. I'm thinking of putting 4cm wider fenders(US)/guards(AUS)/wings(GB) on there. Do you think the wheel will fit under?



Any tips/ideas would be much appreciated

Steve

[starmember]

1st its not bad to mix breaks te most breaking power is in the front. and 2nd the clearance must be about 2cm. Depends on the size tire.