Machining wheel offset

So Lotus specified +60 offset wheels on my car, which as you can imagine are a bit hard to find. The general consensus among Elan owners is that down to +48 will work, but less than that is pushing it. The hubs are 4x100 57mm centre bore, so lots of wheels intended for VWs will fit, but they are typically low-ish offset. How bad of an idea is it to take, say, a +40 wheel and have 10mm machined off the mating surface? On most wheels I've seen there's a lot of material there, but obviously I don't want to compromise the integrity of the wheel. Thoughts?

not a bad idea, but caliper clearance will be reduced.

We'll be doing this to make 18x10 go on the front of our 928 a bit easier.

Won't wheels intended for Hondas work? You should easily be able to find the offset you're looking for.

The issue with machining off the mounting surface of the wheel is that you cannot add material in the bolt hole to add strength there.

The bolt holes are machined to a specific depth, the studs and lugnuts need metal to hold on to. if you machine the thickness away bad thing will happen.

If you got crazy (aka: expensive) with it, you could machine the bolt holes out to have inserts pressed in.

All in all, it's probably just as cost effective to special order the wheels.

I'd look for aluminum wheels that already have steel inserts pressed in for the nuts to seat on. I know I've seen some someplace.Then, machine the back face up to the back edge of the steel insert, and stop there. I wouldn't be machoing any cheap cast wheels, but a decent forged one ought to have more strength , so losing some material might be OK. It's not like you would be putting them on a heavy car. So, xci_ed6 is probably spot on.