Brake Speculation

Suspension, brake, and hydraulic/electric steering discussion.
CrashTestDummy
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Location: Pearland, Texas

Re: Brake Speculation

Post by CrashTestDummy »

So, do the caliper mounting bolts screw into the caliper or the mounting bracket? I haven't looked yet. As Bill indicates, having it drilled and tapped out to 14 mm, unless it leaves way too little metal around it, should be fine at that torque, which I suspect will be around 50-60 lb-ft when all's said and done. Are the mounting bolts 'torque to yield'? What a waste of resources!!
Gene Beaird,
Pearland, Texas
2012 Caprice 9C1
1992 B4C 1LE Camaro
2018 Tahoe PPV (her car)
1995 DGGM Impala SS
1985 Firebird - 310 LS1 C Prepared autocross car.
1980 Bluebird Wanderlodge
And some others
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Navy Lifer
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Location: Canton GA

Re: Brake Speculation

Post by Navy Lifer »

GTObert wrote:If you find something off the shelf to use as a bushing let me know. I am toying with the idea of having the machinist at work spin me out a couple. But really, there have been no problems with leaving it as is, so I might not bother.
Here’s a potential candidate for the bushing:
http://www.mcmaster.com/#8486a54/=zwx03z" onclick="window.open(this.href);return false;

What I’m not sure about is just how much material is left around the mounting holes on the uprights—the bushing I’ve identified is 18mm OD, which may be too large to safely use in the knuckle, and I’m not even certain about the proper length (actually width) that the bushing would need to be....it’s only offered in 12 or 20mm length.

Since 18mm OD may be too large, I suppose a machinist might be able to reduce the OD, but there's not a great deal of material to grip to do that. The McMaster Carr info indicates custom sizes (ID, OD & length) are available.
CrashTestDummy wrote:So, do the caliper mounting bolts screw into the caliper or the mounting bracket? I haven't looked yet. As Bill indicates, having it drilled and tapped out to 14 mm, unless it leaves way too little metal around it, should be fine at that torque, which I suspect will be around 50-60 lb-ft when all's said and done. Are the mounting bolts 'torque to yield'? What a waste of resources!!
Gene, the Brembo calipers are threaded, and there's plenty of material around the mounting ears to go from 12mm to 14mm. I've got to dig into the FSM service procedure to see if TTY is mentioned, or a statement that says "do not re-use" the original fasteners--sometimes it appears to be as simple as using new fasteners because they have the thread locker applied. The torque spec is 30 lb/ft +90 degrees, which is low because the material is aluminum.

The OE fasteners do come with thread locker pre-applied (dry), and at 14mm, I would not have any concern, at that low torque value, about re-using them, as long as fresh thread locker was applied in the process--GM Parts does list a product (adhesive) 89021297, for this purpose, but generic Loctite blue sealant should work as well. Still, I can't tell you what 30 lb/ft +90 degrees is in straight-out torque level/load--it could be pretty high (over 100 lb/ft) as a 14mm fastener (wheel stud for example) is in range at 120 to 140 lb/ft, and we know those are re-useable. The difference is the wheel stud is finer pitch M14x1.5 compared to the caliper mount bolts, @ M14x2.0, which means the finer thread fastener will have a different "holding" load on the threads when it reaches its torque setting.

My point is this--we can conduct an experiment with the wheel--run the lug nuts on with torque wrench set at 30 lb/ft, then adjust torque wrench to 140 lb/ft, and see how many degrees additional is require to reach the 140 setting. This might give us some idea of what happens to the torque on the Brembo caliper mounts, but (again) recall that the thread pitch is not the same, and the coarser 2.0 pitch is actually going to pull or "stretch" more for a given amount of bolt rotation.

Unless the torque is enough to adequately load the fastener, a fastener with a specified torque value that isn't in the range to put at least a little stretch over it's length is not working as intended--and that's why the thread locker is so important. We learned this with the brake fasteners on the 9C1 and Impala SS (B-body) when people would slap in new (rear) brake pads, re-tighten the caliper pin bolt (spec is 23 lb/ft) or caliper bracket bolt(s) (spec 74 lb/ft - M12x1.75), run down the road for awhile, then come to the Forum and ask what happened, why did the bolt come out and allow the caliper to come loose and dig into the wheel? Between not replacing the bolts (FSM says replace each time), or not using thread locker, and not tightening the bolts to the correct torque....yes, it will come back to bite you.

I will add this--it is not easy to get a straight shot at the two caliper mount bolts on the back of the knuckle/upright to be able to tighten them to the specified "+90 degrees" spec in a single swing of a wrench. Some marking method would be most appropriate to do this, and you could potentially even use an impact wrench to do the final tightening--run the bolts in to the 30 lb/ft spec with a torque wrench, make a mark on the bolt head and a mark on the knuckle at 90 degrees from the mark on the bolt, and just bang it around to the mark--done.
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GTObert
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Re: Brake Speculation

Post by GTObert »

I have removed and reused literally thousands of caliper mounting bolts and never had one come loose. Apparently my 3/8" impact knows the perfect torque for these bolts.
2011 9C1
2005 GTO
Navy Lifer
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Re: Brake Speculation

Post by Navy Lifer »

....or you've just been lucky.

Not saying your approach is flawed--I have to put faith in the data the OEM puts out there, and to not inform everyone about what it says would be irresponsible on my part.

Until something convinces me it's wrong or pointless to follow the OEM guidance, that's what I'm doing.
CrashTestDummy
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Re: Brake Speculation

Post by CrashTestDummy »

GTObert wrote:I have removed and reused literally thousands of caliper mounting bolts and never had one come loose. Apparently my 3/8" impact knows the perfect torque for these bolts.
Same here! And if there was ever ONE car to have that happen on, it would be my wife's 95 9C1. She hammered on that car, and I've never had an issue with the caliper bolts coming loose. I DID find out how expensive the emergency brake shoes are for those cars, but that was because of a seal leak.
Gene Beaird,
Pearland, Texas
2012 Caprice 9C1
1992 B4C 1LE Camaro
2018 Tahoe PPV (her car)
1995 DGGM Impala SS
1985 Firebird - 310 LS1 C Prepared autocross car.
1980 Bluebird Wanderlodge
And some others
Do YOU have my SPID?
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GTObert
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Location: Jordan, MN

Re: Brake Speculation

Post by GTObert »

Just in case anyone was still wondering, the factory wheels do fir over first gen CTS-V brakes. I just switched back to my factory wheels for winter and they fit, no problems. They are definitely tight on the rear but they do fit.

As a side note, this means that Camaro SS and SS sedan owners might be interested to know that they can have steel wheels for winter if they want them.
2011 9C1
2005 GTO
CrashTestDummy
Posts: 2300
Joined: Sat Feb 07, 2015 2:31 pm
Location: Pearland, Texas

Re: Brake Speculation

Post by CrashTestDummy »

That's great info! I'm seriously thinking of going that route, since the update is relatively-cheap, if you go factory parts. I keep flip-flopping between keeping the factory steelies on it, or getting the SS wheels I acquired coated black and installed. It helps that I'm not forced to go with the SS wheels, at least immediately.
Gene Beaird,
Pearland, Texas
2012 Caprice 9C1
1992 B4C 1LE Camaro
2018 Tahoe PPV (her car)
1995 DGGM Impala SS
1985 Firebird - 310 LS1 C Prepared autocross car.
1980 Bluebird Wanderlodge
And some others
Do YOU have my SPID?
Navy Lifer
Administration Staff
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Joined: Tue Mar 19, 2013 6:30 pm
Location: Canton GA

Re: Brake Speculation

Post by Navy Lifer »

GTObert wrote:Just in case anyone was still wondering, the factory wheels do fir over first gen CTS-V brakes. I just switched back to my factory wheels for winter and they fit, no problems. They are definitely tight on the rear but they do fit.

As a side note, this means that Camaro SS and SS sedan owners might be interested to know that they can have steel wheels for winter if they want them.
The SS cars use a brake pad with added damper(s) that may cause interference with the wheel--if so, the brake pads would need to be changed or modified.

Discussion on SS Forum:
http://www.ssforums.com/forum/wheels-ti ... exist.html" onclick="window.open(this.href);return false;
http://www.ssforums.com/forum/1291146-post18.html" onclick="window.open(this.href);return false;
firepower
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Joined: Tue Jun 30, 2015 12:49 am

Re: Brake Speculation

Post by firepower »

I am about to dive into the brake swap. So far I have stoptech slotted front rotors for 2010+Camaro SS, stoptech slotted rears for 2014 SS sedan, stoptech pads, goodridge braided lines for G8 GT, f&r CTS-V 4 piston calipers. The fronts are getting drilled and tapped for M14 2.0. My question is this: couldn't I reuse the cts caliper bolts on the rear and the caprice mounting bolts on the front? If not because of length, can someone please tell me specifically what bolts to use on the front? Thank you.
-Nate
2012 PPV 6.0.
Brembo f&r, stoptech slotted rotors/pads/fluid, goodridge ss lines, cai, 3.45 lsd, shorty headers, cat delete pipes, modified corsa 2.5" catback, tune, camaro ss wheels, nitto motivos, BMR rear sway bar, lots of dynamat, pioneer speakers, 1/le hood vent
Navy Lifer
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bolt size & length, rotors to use for rear Brembo conversion

Post by Navy Lifer »

You might re-use the CTS rear caliper bolts--never researched them as to length, but the threads will be correct.

As for front, true that the PPV bolts are also M14x2, but I know they are also shorter--just cannot tell you if they fully engage the mounting ears on the calipers--keep everyone informed as far as what you find out!

2014 SS rotors are same as PPV and not correct for using the Brembo rear calipers--the rotors required are 2015 SS (GM 92281427), which are 360mm diameter, where 2014's are 324mm diameter (and thinner).
http://www.gmpartsdirect.com/oe-gm/92281427" onclick="window.open(this.href);return false;

Caliper bolt PN info & size discussion is on Pg 7 of this thread:
viewtopic.php?f=18&t=568&start=60#p9183" onclick="window.open(this.href);return false;

Correct StopTech 360mm slotted rear rotors would be 126.62147SL & 126.62147SR - listed in the link below:

https://store.zeckhausen.com/catalog/in ... _6230_6233" onclick="window.open(this.href);return false;
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