As you can see no kerbing and refurbed about 18 month ago
Washing the car ready for a run tomorrow I noticed these
looks like that car is stranded
Wow, you must be gutted 
What wheels are they, original equipment?
Seen this before somewhere, maybe piston heads. General sensus of oppinion is that it’s caused when refurbishing the wheels - Getting the temperature too high when baking the powder coat paint!
Lucky to notice before they broke, could have caused a nasty accident.
Just looked it up.
It’s 2 years ago these where powdercoated, you would have thought if that caused it, it’s a very delayed reaction.
I guess it’s quite possible. If the alloy started to crack after baking then it’s taken this long to creap to the front face.
Difficult to prove after this time, but that’s where I’d put my money.
http://www.mx5oc.co.uk/forum/forums/p/29420/201233.aspx#201233
Now replaced with a set of Rota RB
The wheel pictured is o/s rear. The n/s rear is showing signs on the inside, the n/s front is also showing signs of starting to crack. The o/s front is ok, but I suspect this was powdercoated seperately after I buckled a previous wheel