I changed the pads and rotors on the rear but when reassembling there was a bit of grit in the caliper threads (not the bracket). The bolts are still fine except for 1 which I'll get a new one. But the threads in one caliper got slightly damaged at the end. Not loose in any way and it holds well, but not going all the way in. I'd rather try and salvage these instead of replacing with non OEM ones. Anyone have any suggestions? I am thinking to use a tap that is the same size but don't want to ruin it by doing so. Would be my first time attempting to repair threads and any advice would be appreciated.

 

If the bolt is not fully seating then you can use a washer under the head to allow for it to be tourqed down. It only needs to be as thick as it need to be to allow the bolt to seat. You can also use a tap if you'd like. No harm in that

 

I'm going to try and clean the threads I think first. I still feel bad putting a couple washers in there. One of the bolts still has 4 threads showing which is quite a bit... probably 3 washers.
Tks.

 

With 4 threads showing - and what I seem to remember is a 1mm pitch, that's quite a bit on what is around 12~15mm(?) thread engagement.

A tap would be unlikely to ruin the caliper unless you start it cockeyed and then run it through to to where the problem starts. A 14x1(?) tap on the other hand won't be cheap, but maybe a carbon steel rather than hss one might be a little affordable for one-off use. If there's just a burr, rather than the last 4 threads totally munted, a thread file may do the trick too.

 

Yeah, agree on the too much sticking out and I don't want to just try and force it and weaken the caliper bolt. I went to home depot and can see it is a fine thread 14mm. But they didn't have a big enough nut to slide over and check the exact pitch. Anybody know what that number is?

 

I used the spark plug for a test but felt resistance quite quickly. not sure if it it because the threads are messy or its a diff size. if the same it will be easy for me to order a thread chaser as they abound on Amazon. Just checked and it's m14 X 1.25. I think it's the same. Any dissenting opinions?

 

Not likely to find a nut in extra fine at hardware places. Pitch gauge will comes in handy for these situations - and are cheap, but you should be able to measure a set distance on the bolt, say 10mm, and count the thread crests to get the pitch easy enough...10 for 1mm, 8 for 1.25, etc.

 

Superb. That's what I'll do then. FYI for anybody else who runs into this situation seems Mazda has discontinued the pins. I'm going to have to clean up the threads on them as well to be safe.

 

Instead of using a tap, try a thread chaser to clean and reform the threads. A tap is designed to cut new threads and can damage existing ones.

 

Yeah, that's what I decided to do after a bunch of research.

1) Ordered pitch measure (90% it;s the same as the spark plugs but want to be 100%)

2) Once I confirm the pitch I'll order a thread chaser set and try with that.

3) If that fails I'll do a helicoil style insert

When I get it, I'll post up the thread pitch for future lookers as it seems this does happen every so often.