1.75 is standard coarse thread. Even my local sears has 1.75. 1.25 is super fine and much harder to find.

 

Also I agree that I highly doubt it's 1.75....usually honda uses M12x1.25

 

Sorry guys it was 1.25

 

You can try ARP or DMP Fastners as well.

http://dmpfasteners.com/

I sourced some hard to find bolts through DMP for relatively good price, including stainless steel.

 

My hardrace flange bolts were also too short (~39mm) vs OEM (~37mm). You can see they do not fully thread the knuckle.


So after many hours of digging without success, I scoured the Honda parts bin and found this!

It is a 45mm flange bolt from Honda Civic Si engine mount (90165-SDA-A00 BOLT, FLANGE (12X45)). It does have "10" marking on top of bolt but not sure if it is zinc coated for rust prevention.

I guess you can also use the following (not confirmed)
90397-SNA-A00 BOLT, FLANGE (12X51) <--- this one is 51mm if you want it a little longer, almost sure these will fit fine too
90174-TK6-000 BOLT, FLANGE (12X45) <--- from Honda CR-Z engine mount
90174-TM5-000 BOLT, FLANGE (12X45) <--- from Honda CR-Z engine mount

Notice how they fit nicely!

 

^Better but I'd still prefer a bolt that went all the way through

 

Same here.

 

They are fully threaded with the knuckle. I know it is hard to tell from pictures. The flange bolts are 45mm.

 

20mm of thread is more than enough.

 

Does anyone know the front Hardrace castle nut's size and thread pitch? It looks like M14 x 1.5mm TP, the nut would need to be 20mm tall
In the rear the Hardrace castle nut is the same size and thread pitch as OEM, so I just re-used my existing castle nuts to cure Hardrace's short nut syndrome,
but the front nut is a different thread pitch than OEM...


As far as sourcing other OEM bolts to mount the RCA to the knuckle, It would be nice to find a part number for bolts that have an enlarged shoulder like the original bolts do, see the shoulder on the one on the left? I found 60 mm OEM bolts that do and could work, but it would be nice to find some in 50mm.