Driving to work today heard a thunk and the right front brake started making noise. Turned out I lost a bolt that holds the caliper mounting bracket on. This bolt is very fine threaded and unique to the 79. Anyone know where I can get one? The parts manual doesn't even list a part number for it.

Herb

 

lost 'a' bolt meaning 1? there's 2 that hold the bracket. remove the other one and take it to a hardware store and match it up.

 

Herb-
The "mounting adapter" (mazda parts speak for the rear assembly the brake caliper mounts to) is identical in the 1979 and 80 SA, therefore it is safe to say the BOLT you need is the same. The 1980 parts book page DOES list a PN, tho oddly, as you say, the 79 page does not (on the microfiche copies I have).
The 1980 bolt PN is:
9975011018
But am guessing this is not a stocked part.
That said, the SA RX7s used a finer-pitch bolt for a lot of applications that the FBs do not (brake fittings for example), but as others say, that is not to say the Pitch is unique. Fine pitch hardware like this is available. if not locally, then someone like Hillmann or https://www.belmetric.com.
FWIW I have found some surprising options at ACE hardware!

Stu Aull
80GS
AZ

 

Hardware can come in 2 or 3 different fine series of thread pitch's, and normally a single course pitch, as well as in various thread forms (which is a different subject). But the engineering community establishes both a "standard fine" and standard course" pitch for each diameter, American and metric. In some special applications (like engine or transmission internals) an "extra fine" pitch may be called out by the designer. But in something like your brake caliper, it's going to just be the standard or common fine pitch, that you can find at your local hardware store. Like rxtasy3 says, take the other one off and match it up at True Value. Class dismissed.

 

Ace is the place! You can try lowes or homedepot too, but Ace always has the best selection on odd hardware and especially metrics.

 

+1 for Ace Hardware. They always have the best selection for both SAE and Metric.

 

Hope you are right. The bolt looked like extra fine thread to me. I have a direct deposit at my local Ace hardware.

Thanks,

Herb

 

I found that there are two different lengths for that bolt during my build. It's a M12 x 1.50, and one is 25mm long and the other is 40 mm long. I had ordered replacements in the 25mm length but later found that it was just too short for the part of the strut tube that is thicker. Had to order on line and paid about $10 including shipping. Was not happy.

 

For reference, I did some checking and the bolt is still available new from Mazda. You can get one from the hardware store for now and order a new one to have the correct bolt in place.

 

Also keep in mind the bolt strength grade of of the replacement has to be at LEAST as high as the original. You don't want to downgrade brake parts!

Markings on the bolt head, key to the marking in the FSM reference material.