Distorted threads on GT350 rear calipers?

[JAJ]

So, I've had my rear calipers out of the car three times now, and it's always been a brutal experience getting the caliper mounting bolts out. Just turning them has been a 30 to 40 ft-lb torque exercise.

I always blamed this on the bolts. The factory pair were blue (always a bad sign) and they were miserable to get out. So, I bought a new set of bolts from the parts department and used them. They came with thread locker on them and they were worse! They were so hard to install that I actually hit target torque before they were all the way in. The caliper was rattling so I tightened them some more.

So, over the winter I invested in some bolts from Belmetric. 10.9 rated with the correct dimensions and no thread locker. I figured I had it beat. But, today when I pulled the calipers off to install the CCB rear rotors, I found that even the new uncoated bolts wouldn't screw into the caliper threads. So, I took my trusty M12x1.75 tap and chased the threads. Well, it wasn't really "chasing" them. It might as well have been "making" them. Even with lots of Tap Magic, it was tough going (and this is aluminum) but I got the tap through. There was a mess of thread locker and metal chips, but when i was done, I could finally screw the bolts in with no problem.

So, the question is, has anyone else experienced this? Are my rear calipers mis-manufactured or do they really have distorted threads to keep the bolts from backing out. I've never seen anything like it.

 

[captdistraction]

all 4 were that way? GT350 caliper or the coated R?

 

[JAJ]

all 4 were that way? GT350 caliper or the coated R?

They're the grey anodized GT350 calipers, on the car from new in May of 2016. All four bolts - both bolts on both calipers - were like this, which is why I think it might be intentional. They were all like this, but they weren't all the same - one was super tough and one was (relatively) easy, but you couldn't put a standard M12x1.75 bolt into any of them without a wrench.

The problem is that while those bolts are relatively easy to reach, they're surrounded by suspension parts so you can't get an impact wrench on them and the fender and the brake hose combine to stop you from using a long-handled ratchet, so it's like doing bench presses with a standard length 1/2 drive ratchet.

 

[VoodooBoss]

I stopped using loctite on brake caliper bolts for this reason. I'm not recommending not using loctite but it's there for the street car that sees a brake job every 60-100K miles not necessarily for track/race cars.

 

[TMSBOSS]

If you do use locative. You need to clean threads every use.

 

[TymeSlayer]

What color was the Loctite? Red or Blue? Or was it a nylon patch that was sprayed on? If it was the nylon patch, small particles of the patch will become dislodged and can cause interference in the female mating hole. If you do go with a threadlocker, blue would be the way to go.

 

[JAJ]

What color was the Loctite? Red or Blue? Or was it a nylon patch that was sprayed on? If it was the nylon patch, small particles of the patch will become dislodged and can cause interference in the female mating hole. If you do go with a threadlocker, blue would be the way to go.

If this question was for me, the answer is that the original blue bolts had no thread locker on them. They were clean but crazy tight and hard to get in and out. I took them off once, on once and off again before I replaced them. I assumed the blue finish meant that they were distorted so they didn't need locking compound. I thought they were way too tight so I replaced them with Ford parts-counter replacements that come with a ring of thread locker on them. My experience with them in other locations on the car is that they're easy the first time going in and they are tight coming out, but if you re-use them they loosen up but they're not at risk of falling out. Well, they were even harder to put in than the blue ones and brutal to get back out this week. As I said, they actually got to torque spec of 85 ft-lbs before they were fully seated.

When I was chasing the threads, I got the thread locker from the second set and I got lots of aluminum chips as well. They're currently assembled with dry bolts - no locker at all. Now that I have the situation under control, the next time around I'll be using VC-3 (https://www.vibra-tite.com/threadlo...ble-threadlockers/vibra-tite-vc-3-threadmate/) on them.

What I'm curious about is whether anyone else with a GT350 that's had their rear calipers off has experienced this phenomenon.

 

[thelostotter]

Experienced the same thing on my 17 GTPP. I thought I had somehow buggered up the threads on the drivers side since the passenger side was fine. So I bought a M14 x 2.0 tap and was going to chase the threads and use new bolts. Turns out I was able to twist the tap through with just my fingers and it cleaned out a TON of thread locker. No issues since.