As someone said earlier, Metro and Mini offsets are different. Have a look at this guide from Metropower, it will give you some ideas.
http://www.metropower.org.uk/portal/def ... 88&mnu=188Too wide a rim on a MK3 will make the steering very heavy and probably stick beyond the wheel arch. My rims on that convertible with the MX5 seats are only 5.5 inches, but have a wide section tyre and I just manage to keep the tyre on the limit of the wheel arch. There is some argument about the offset (also called the "C" distance) on my wheels which is 115mm, some people say it should be 128mm. If the offset on my wheels was 128mm, it would mean that the tyre would be closer to the coil-over (inboard), probably meaning that it would fit under the wheel arch better!
So in simple terms 128-115=13mm closer inboard.
Bloody maths I wish I'd gone to school more often!
This could create other problems, like the tyre catching on the inside.
This is my understanding, but others my have a differing opinion! Some Midas owners have stated that the Metro turbo wheels ( I think) have the best offset for a Midas. You can use different wheels say from a Honda car (just an example), but you would have to re-drill your hubs to a differing PCD (Pitch circle Diameter). So you basically put your wheel studs in a different place on the hubs! There are no rules, these are Kit Cars, you make it up as you go along! So that's my two-penny's worth.
Hope it helps.
Alan