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Stripped brake caliper mounting bolt hole

Joined
Mar 26, 2002
Messages
812
Location
Midlothian, VA
Corvette
1981 white/blue interior automatic
I had to replace my right-rear caliper last week, but when I went to tighten the right mounting bracket bolt (towards the front of the car) it didn't feel "right." I decided to check on it again and now I can feel that the bolt hole appears to be stripped. I went as far as replacing the bolt, but as soon as it grabs the threads and you start to torque it, it "slips" back and turns freely. I've done a TON of reading on this, and I can see other C3 owners have had the problem. My question is:

1. Do you think I could get away with just using a 7/16"-20 thread chaser, such as this one? Is it even worth trying?

2. Or is the Heli-Coil the way to go? I've never used one... do I have to take the entire trailing arm off, or do you think I could drill and tap the hole while it's still installed? That solid brake line looks like it's going to get in the way.

Thanks for the help!

-Tatortot
 

GTR1999

Well-known member
Joined
Sep 4, 2003
Messages
1,146
Location
New Haven CT
Corvette
1969,1972,1975
I had to replace my right-rear caliper last week, but when I went to tighten the right mounting bracket bolt (towards the front of the car) it didn't feel "right." I decided to check on it again and now I can feel that the bolt hole appears to be stripped. I went as far as replacing the bolt, but as soon as it grabs the threads and you start to torque it, it "slips" back and turns freely. I've done a TON of reading on this, and I can see other C3 owners have had the problem. My question is:

1. Do you think I could get away with just using a 7/16"-20 thread chaser, such as this one? Is it even worth trying?

2. Or is the Heli-Coil the way to go? I've never used one... do I have to take the entire trailing arm off, or do you think I could drill and tap the hole while it's still installed? That solid brake line looks like it's going to get in the way.

Thanks for the help!

-Tatortot
I see them a fair amount of time when I get in arms to rebuild. The chaser isn't going to help but you can try it if you like. You can repair it but I don't using Heli-Coils because the coils can unwind at times. I use a solid thread insert. You drill and tap it for the inserts OD thread. I screw it in with Loctite #638 green and stake the hole then test fit a 7/16-20 bolt in place. If done correctly it will be fine. You have to get room to work on the car. I do them with the bracket off the arm on the bench. In order to do that you would have to take the arm apart and then you will be looking at rebuilding them for sure.
 

Antz81

Well-known member
Joined
Dec 21, 2013
Messages
936
Location
Auckland, New Zealand
Corvette
1981 4 speed
I agree with gtr. The chaser will only clean up a damaged thread, not repair a destroyed one. Nor would I trust a helicoil in there.
 
Joined
Mar 26, 2002
Messages
812
Location
Midlothian, VA
Corvette
1981 white/blue interior automatic
Thanks for the info guys. Wish I didn't have to press out (and then in) the bearing to get the bracket off... I might as well just replace it if I went that far, which I don't want to do. Wish me luck!

-Tatortot
 

GTR1999

Well-known member
Joined
Sep 4, 2003
Messages
1,146
Location
New Haven CT
Corvette
1969,1972,1975
If you remove the spindle you're going to wreck the bearings most likely so you should replace them. Now some think you can buy new bearings and reuse the shim but that's not going to work. You should be able to use the e-z lock type thread insert on the car but you have to be sure it's locked in place, otherwise you should replace the bracket and will end up rebuilding the arm.
 
Joined
Mar 9, 2009
Messages
1,026
Location
Yemen
If the bolt hole is really stripped I would simply replace that caliper and then keep your old (damaged) one for spare parts.
 
Joined
Mar 26, 2002
Messages
812
Location
Midlothian, VA
Corvette
1981 white/blue interior automatic
Well, I had great success using a Heli-Coil. I know that wasn't the recommended fix, but the packaging for the Heli-Coil kit even said it was great for caliper mounting brackets. It was so much easier than I thought. I didn't know the mounting holes could be drilled from either side, and after removing the rotor I had easy-access to the bracket. The bolt is now snug as a bug and I feel MUCH better. Re-bled the brakes and took it for a test drive and it all appears to be working great! Thanks for all the help!

-Tatortot
 

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