caliper bolt fell off on the freeway
07-22-2008, 07:04 PM
#21
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had this happen to a friend. His bottom bolt on a rear caliper fell out on a highway drive then as he came to a stop in the tech lane at the drag strip
the top came out. and the caliper grabbed the rotor and went around with it till it broke the brake hose.
the top came out. and the caliper grabbed the rotor and went around with it till it broke the brake hose. 
07-23-2008, 01:09 PM
#23
The most important thing is having the correct torque, which is 74 lb ft. (If you have the work done at a shop and they can't tell you what torque they set these bolts to, don't trust that the work was done correctly!)
Its also critical to have the proper strength bolt. For the rear calipers, the bolt should have a 10.9 stamped in the head. This signifies that the bolt is a 151,000 psi steel. If the bolt does not have this marking, the bolt will be too weak and will not be safe to use. If the bolt is the wrong type of steel, it may also not develop the proper tension under torque and could come out of place.
Locktite is nice, but is really unnecessary. Its a great product for keeping screws from coming out of place due to vibration - but in the case of the caliper bracket bolts, the forces at play from a properly torqued bolt are far in excess of what locktite can provide. No harm in using it - but as 00 Trans Am points out, all locktite will really do in this application is cause a mess and make the bolts harder to get out once you break the torque.
Using lockwashers is also not a safe thing to do in this application. Over a short period of time, they will yield and compress. As they do this, the bolt will loose tension (torque) and the bolt will probably come out again. As noted above, the holding strength of locktite is less than that required of the proper torque, so even with the locktite - the bolt can still come out if the bolt is not the proper strength and is not properly torqued.
Overtorquing the bolts above the recommended number (74 lb ft) is also not generally a safe thing to do. Increacing the torque will also increace the tension and stretch in the bolt. This may also weaken its working strength and make it more succeptable to failure under shear.
Its also critical to have the proper strength bolt. For the rear calipers, the bolt should have a 10.9 stamped in the head. This signifies that the bolt is a 151,000 psi steel. If the bolt does not have this marking, the bolt will be too weak and will not be safe to use. If the bolt is the wrong type of steel, it may also not develop the proper tension under torque and could come out of place.
Locktite is nice, but is really unnecessary. Its a great product for keeping screws from coming out of place due to vibration - but in the case of the caliper bracket bolts, the forces at play from a properly torqued bolt are far in excess of what locktite can provide. No harm in using it - but as 00 Trans Am points out, all locktite will really do in this application is cause a mess and make the bolts harder to get out once you break the torque.
Using lockwashers is also not a safe thing to do in this application. Over a short period of time, they will yield and compress. As they do this, the bolt will loose tension (torque) and the bolt will probably come out again. As noted above, the holding strength of locktite is less than that required of the proper torque, so even with the locktite - the bolt can still come out if the bolt is not the proper strength and is not properly torqued.
Overtorquing the bolts above the recommended number (74 lb ft) is also not generally a safe thing to do. Increacing the torque will also increace the tension and stretch in the bolt. This may also weaken its working strength and make it more succeptable to failure under shear.
at least he sat on the floor on the towel the whole way.
07-23-2008, 03:17 PM
#25
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FYI - I would go with Wssix99's suggestions on torque specs. I've gotten to where I just tighten mine down as much as possible. But, I'm also taking them on and off once per month to swap brake pads (going from RR to autox pads, or swapping RR compounds).
07-31-2008, 06:54 AM
#30
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That 74ft lbs spec is for the bracket that holds the caliper correct? The actual caliper bolts get torqued to 22 something ft lbs? Just changed my brakes and am going on a long trip with the car. This thread has me a bit paranoid and I'm going to double check everything before I hit the road.
08-01-2008, 07:14 AM
#31
That 74ft lbs spec is for the bracket that holds the caliper correct? The actual caliper bolts get torqued to 22 something ft lbs? Just changed my brakes and am going on a long trip with the car. This thread has me a bit paranoid and I'm going to double check everything before I hit the road.
I'm away from my books right now, but I believe the 22 ft lb is for the bolts that hold the caliper to the bracket. The torque is less critical for these. (Low torque on low strength bolts.) I assume that GM feels they are more prone to vibrating out, which is why they ship with Thread Lock on them. I personally wouldn't worry as much about checking these bolts other than a simple tightness check, unless you have the time to get in there, check for Thread-Lock, etc.
11-17-2008, 12:46 PM
#32
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Yea, that 74 ft lbs is ONLY for the big beefy high strength bolts that hold the caliper carrier bracket to the spindle in the front or the axle plate in the back. If you have a torque wrench and if someone else has touched these bolts on your car and if you are not sure the work was done correctly, I would deffinitely suggest that you check thier torque. They are easy to get to and its a relatively easy thing to do - great insurance.
I'm away from my books right now, but I believe the 22 ft lb is for the bolts that hold the caliper to the bracket. The torque is less critical for these. (Low torque on low strength bolts.) I assume that GM feels they are more prone to vibrating out, which is why they ship with Thread Lock on them. I personally wouldn't worry as much about checking these bolts other than a simple tightness check, unless you have the time to get in there, check for Thread-Lock, etc.
I'm away from my books right now, but I believe the 22 ft lb is for the bolts that hold the caliper to the bracket. The torque is less critical for these. (Low torque on low strength bolts.) I assume that GM feels they are more prone to vibrating out, which is why they ship with Thread Lock on them. I personally wouldn't worry as much about checking these bolts other than a simple tightness check, unless you have the time to get in there, check for Thread-Lock, etc.
11-17-2008, 09:45 PM
#33
Can you tell me the size of the wrench or hex size it takes to disconnect the calipers from their mounting brackets? I would hate to get her all jacked up, stands under her, wheels off, and then not have the proper size wrench to take the calipers off!!! Thanks in advance.
12-29-2009, 07:44 PM
#34
Bringing this thread back to life after a year. Can these be tourqed down with the wheels still on the car? I tightend them all by hand as hard as I could when replacing my pads but didn't tourqe them down. I have since bought a tq wrench and would like to be sure.
12-30-2009, 09:15 AM
#37
Can you tell me the size of the wrench or hex size it takes to disconnect the calipers from their mounting brackets? I would hate to get her all jacked up, stands under her, wheels off, and then not have the proper size wrench to take the calipers off!!! Thanks in advance.
12-30-2009, 09:42 AM
#38
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I have been working on car for a living for a long time now and have never used loctite or any other anti-seize on anything. hundreds of cars all years makes and models. everything from jags, to mercedes and porsches for old 60's cars and ive even done corvettes and f-bodys. I've never seen a properly installed caliper come lose. Loctite is not necessary at all.
12-30-2009, 09:48 AM
#39
Is what I posted above the correct specs? I have a tq wrench and I'm about to use it on the brakes. Thanks for the help..
