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Need to order hubcentric wheel rings to fit Enkie PF01. Difficult to measure exactly with my calipers but about 75mm by ruler. Enkie website says bore diameter is 75mm.
Question is, what size rings will fit exactly.
54.1mm x (75mm?) or is there a tolerance to the 75mm to make a little less.
Any help is greatly appreciated.

Yes you are correct. 75.0 OD, 54.1 ID.

I've never run hub rings on my RPF1's

if you install the wheel correctly it will be right

These are quite contentious fittings. My own view is that they are instruments of the devil.

Do a search on here, I am sick of pointing out what a nonsense they are, but you will readily find my opinion, and that of others, using the search function. Do try and use that function, it is actually very handy

I get you greenmachine. No need for road use where the loads are inside design specification and where the wheels go on or off once in years and then only by your tire dealer.

I come from a racing background and the wheels come off and on frequently. So I like the wheel to sit tight on the studs before the nuts go on. I don't like to rely on the studs to center the wheel. Reason 1.

Reason 2. I like the loads to be shared by the hub AND the studs. Over the years I have seen many wheels destroyed (the car and sometimes the driver also ) on the track. All the ones destroyed I have seen relied only on the friction between the hub and the wheel (no hubcentric rings).

mx5 is a new experience for me so I will fit hub centric rings but I need to know before I buy whether a 75mm OD will go into an Enkie OD of 75mm. So the question is whether Enkie quote 75 but in reality it's 75.1.

I know in engineering terms that a 75mm hub will not fit into a 75mm hole but will fit into a 75.1mm hole.

Goodwin Racing are an excellent resource for hubcentric ring sizing.

http://www.good-win-racing.com/Mazda-Performance-Part/61-0593.html

Optional hubcentric rings (takes size 75/54 for Miata).

Also note:

Note the deep sockets around the lug holes, the upside of this feature is much greater strength and less flex than many wheels suffer in that part of the wheel but the downside is that stock lugs won't work and you need our narrow extended length McGard, BLOX, Team Dynamics, or 949Racing Lugs.

The Zork wrote:I come from a racing background and the wheels come off and on frequently.

I have tracked MX5s for over 10 years. My opinion is informed by that experience.

Nothing further to say. I have said it elsewhere.