While replacing brake pads on a 94 Grand Am, one of the driver-side
caliper mounting bolts -- the thread on the mounting bracket, rather --
got stripped before reaching the torque specs. I thought I could use a
HeliCoil insert, but was advised against it, as there was "too much
pressure" there which would break the HeliCoil. I ended up installing a
universal GM oversized caliper mounting bolt. The problem is that the
bolt seems to be slightly longer and reached the bottom of the hole
before it could get fully seated on the outside of the stabilizer. So
there's a little slack (probably .5 to 1.0 mm) when I try shaking the
How unsafe is that? I know that bolt is not going anywhere, it took some
monstrous torque to get it to where it is. But still, I'd like to be
sure that I'm not missing something. And I'm trying to avoid replacing
the whole mounting bracket because of a stripped thread.
The bolt is one of those self-threading oversized ones that NAPA and
other places sell, to help guys that mess up like I did. When I compared
the oversized bolt to the original one, they seemed of an equal length.
What I should have accounted for is the excess material that the bolt
cuts making its way in. It's got to go somewhere, and probably that's
what's preventing the bolt from going all the way in.
If it were mine I would unscrew the bolt, clean out the threads in the hole
and put it back together again. Surely screwing it in the second time
wouldn't be as difficult would it? Or is the bolt a one time-use only deal?
But that's just me being anal. It would bug the heck out of me thinking
about all the ways that the existing situation might cause a serious braking
problem down the road even if those possibilities are only remote or even
nonexistent. Peace of mind.
Yes, it's one of those -- per the directions on the box, it is not
recommended for reuse. And I'm not sure if a new one of those would
work, if I unscrewed this one and cleaned up the whole. I was hoping I'd
find someone here that has had experience with those oversize bolts.
Agreed. It's bugging me already, more so that it's my son's car. That's
why I'm asking.
you can helicoil it. A helicoil will hold way more pressure than you
think. I have installed a good thousand of them in fighter aircraft
and the brake system is one of the places we install them in. Never
seen one break from too much pressure yet. Normally the bolt will
break before the insert. Just make sure you get Heli-coil Brand and
not a cheap knock off. And get a free running. If you run a screw
locking you will need a good quality bolt and not a parts store cheepo.
As for them breaking with too much pressure. That is complete BS.
The only thing you shouldn't use them for is when the parent threads
need to seal a fluid with any pressure.
There is nothing wrong with using a helicoil. They are as strong
or stronger then the original thread. I certainly wouldn't be using
some sort of oversize universal bolt. These are brakes that we
are talking about. Just fix it right. If you don't feel comfortable
with the helicoil, then install a new spindle, or go get yourself
one from a wrecking yard.
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