I have 10" rears and they just fit. I would not want to go 10.5". Yes, it's that close to the shock tower. My offset is 45mm(rim is ET65 and I have a 20mm spacer). The fronts should be fine.
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2001 Boxster S Lapis Blue
TS Cat Bypass Pipes and exhaust
iPad Mini Dash Install
DEPO Tail Lights
Factory rims are like 7.5"in. In the front , 9.5"in. In the rear. With factory recommended tires, actual tire contact on pavement is 8"in. In the front and 10"in. In the rear. It works perfect for me since I don't have twin turbo's .lol. A simple factory spec'd 3.2 litre.) I have enough grip action to keep me satisfied.