Hi,
I'm trying to fit a pair of Paul Dunstan's RX-7 Caliper adapters to my GRP4 Capri coilover struts. No problem with the kit, it's great, but I need to test fit the calipers so I know how much to machine off the spacer kit in order to centre the discs in the calipers. (using alloy hubs, which 
The main problem ( I seem to have an ever growing list of problems with the rebuild!) is that the mounting bolts in the kit are M12 x 1.75 & the caliper mount holes on the struts are a 7/16" UNF 20 thread.
I can see three possible solutions, but would appreciate any input in case I'm missing something.
 
The simplest solution, fit the adapters to the strut using 7/16" bolts. I don't like this idea as the bolts are not a snug fit through the adapter plate holes like the M12 bolts, they are understandably quite loose. Although the bolts would most likely centre themselves in the hole, as the bolt heads are countersunk into the adapter plates, I'm thinking that all of the lateral force from the caliper under braking will be concentrated on the bolt head. Not to mention that the bolts may not centre themselves properly either.
 
Second solution, drill & tap the strut to accept the M12 bolts. Again, not my favourite option, as I don't believe the correct drill for an M12 size tap would remove all of the 7/16" thread, even a slightly oversize drilling for an M12 tap? Doesn't sound ideal. . . especially for brake Caliper mountings. Plus, I've fitted & removed most of the front end so many times in the last month, that I'm over it. The last thing I want to do is strip down a pair of assembled & fitted front struts, yet again!!!
 
Thirdly, find someone that can laser cut a new set of adapters using Paul Dunstan's kit as a template, but have the mount holes drilled & countersunk to take 7/16" UNF bolts. My only concern there is that the kit & the normal 2L strut was designed for M12 bolts, probably for strength reasons. Surely 7/16" UNF bolts should be up to the job? They're barely smaller than M12's in diameter.
 
Also, anyone with experience using this kit. How much clearance from disc edge to caliper should there be radially? I'm using the RDA 7103D discs as recommended. I mounted the RX-7 caliper temporarily using some spare seatbelt bolts (same thread) and although the caliper is very slightly cocked over as it just contacts the disc on one side. . . there looks to be little to no clearance at all radially to the caliper?
 
Any thoughts, clarification or ideas would be most welcome.
Cheers, Jason. 
 

There are bolts avail from UK that have 12mm shank and 7/16 UNF thread.
 
http://www.ebay.co.uk/itm...cnrc5S4KNAS6aRus7gm2-g

http://www.ebay.co.uk/itm...kRmssiw2pQDI_5FQMpJ8_A
 

Thanks, I hadn't seen those before. They're close to what I need, but with a countersunk head.
I'll add some pics tomorrow of the bolts & spacer kit to show what I mean.
 
Cheers, Jason.

Spacers & existing bolts.
 

 
Cheers, Jason.

For anyone who strikes the same problem down the track, high tensile 7/16" UNF countersunk socket head bolts proved very hard to find. . . but they are available.
Anyhow, went for the first solution if anyone's interested. I was probably over thinking it. When the bolts are torqued up & under tension it doesn't really matter that they're not a tight fit through the smaller of the two spacer plates. Much like the way a tapered wheel nut seats. All good!
 
Cheers, Jason.

Looks like you found the solution before I saw your post anyway.
I had to centre the disc ever so slightly when I installed mine. Very slight machining down and was perfect!

The bolts i think i got from BSC, they just had to get them in from another store interstate for me (SA i think it was?).

Thanks all the same though.
Yeah, still need to centre my discs. Looks like I need roughly 2mm machined off both the spacer plates. Will get an exact measurement tomorrow.
Nearly there!

Glad you got it sorted Jason.

Thanks Paul, so am I!
I ended up having the two spacer plates machined down to 13.1mm each to get the discs centred in the calipers. Everything's spot on now. There's also plenty of clearance between the calipers & the new 15" wheels. . . which I was pretty happy about, considering the whole front end is new & basically everything is a test fit as I'm going along. Was due for some good luck with it, ha!

 
 

 
Just need to trim the mount bolts to length & paint the calipers to finish off.
 
Cheers, Jason.