OK, that does very much appear to be a proper Mini Hub (for Disc Brakes).
Just keep in mind that machining down the 8.4's to 7.9" is only taking 1/4" off the radius, so not much and that pic ^ does look about right.
The Drive Flange also looks to be a stock type as would be used with the 8.4" Discs. Those for the 7.5" Discs have 4 Countersunk Phillips Head Screws holding the Flange to the Disc.
Google is thy friend (but not always!)
http://www.miniminimini.com/?p=15
"10″ Brake Conversion For The Classic Mini
From about 1986 the powers that were made the decision to update the look of the classic Mini across the range. The decision was to fit 8.5″ brake discs for safety and up the wheel size to 12″ from the 10″ used previously. Of course, these weren’t the first cars to use the 12″ wheel. The Mini Clubman 1275GT used 12″ wheels way back in the mid seventies. 13″ wheels were introduced in 1997 in a further update to vehicle specifications, mainly to satisfy the German market.
Since then Mini owners have had the choice of using 10, 12 or 13″ wheels. The latter two present their own problems when fitting them to the car. Most 13″ and some of the wider 12″ wheels require modification to the body, specifically the wheel arches to allow enough clearance when turning the front wheels.
Using 10″ wheels on a disc brake equipped vehicle presents its own problems. That problem is that the 10″ wheel will not fit on the hub of the disc brake without fouling the caliper. The fix for this is to fit 7.9″ or 7.5″ brakes discs and the appropriate size calipers. Easy to say, not so easy to do.
Of course, there are (as always with Minis!) a few options. The first option is to locate a 7.5″ disc setup from a classic Mini Cooper. These are however becoming more difficult to locate and as such the price is increasing. The second option, and the one for those with lots of money is to purchase an aftermarket disc and caliper setup.
The kit shown to the left is available from Mini Sport at a cost of £267 inc VAT. It consists of everything that you will need to convert to 10″ wheels. If you’re feeling really flush you could go for this 7.5″ 4-pot brakes setup from Mini Speed, but at £469.15 ex VAT, it’s only really a viable option if you intend to race or do track days, or you’ve won the lottery!
Okay, you’re a Mini owner. My guess is that you’re thinking there must be a cheaper alternative. You’re right, there is. It means scrabbling around in scrap yards, getting out the grinder and ordering custom brake hoses, but that’s half the fun right!?
Sammy D over at P&SMOC‘s forum has a thread running where he is doing the conversion to a 7.9″ brake setup using Mk I Ford Fiesta calipers. He’s documenting the conversion as he goes along, but it should turn out to be a really interesting read. So far he’s collected the parts he needs and is attacking the calipers with the angle grinder. If you are considering a 10″ conversion on a budget then this thread is definitely worth bookmarking for reference."
