caliper bolt fell off on the freeway
12-30-2009, 11:45 AM
#41
Use threadlocker... GM does.
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www.stranoparts.com --814-849-3450
18 SCCA National Championships in house, many more for our customers prove we know our stuff.Talk is cheap, results matter.
Check out our KONI prices, our Master Cylinder Brace, and new Xtracker Hub/wheel bearing upgrade kits!
12-30-2009, 02:23 PM
#42
12-30-2009, 04:15 PM
#43
Alright I've got them all done both caliper and bracket bolts. The guy at Oreilley's said to use Permatex thread sealant instead of the blue threadlocker med strength. I hope he knows what he's talking about lol. It's high temp thread sealant and it's white. He said they won't back out but still can be removed by hand. I hope so.
09-13-2016, 04:25 AM
#44
Im bringing this thread back from the dead. Im about to torque down my rear brake bracket bolts and my 98 gm shop manual is telling me to torque them down to 160 ft lbs. I thought it was a mis print but after reading about all these calipers coming loose Im considering the 160 torque. So question is 74 ft lbs? Or does GM seriously want 160 for the rear brake caliper bolts?
09-14-2016, 08:24 AM
#45
Im bringing this thread back from the dead. Im about to torque down my rear brake bracket bolts and my 98 gm shop manual is telling me to torque them down to 160 ft lbs. I thought it was a mis print but after reading about all these calipers coming loose Im considering the 160 torque. So question is 74 ft lbs? Or does GM seriously want 160 for the rear brake caliper bolts?
In this case, that torque spec IS a misprint - and a pretty dangerous one. GM has a TSB on it: http://workshop-manuals.com/chevrole...liper_bracket/
So, you can rest easy by torquing the bolt to 74. As long as you get that torque, the bolts will stay. Its a lot of torque and I recall that most people who have had problems with the bolts coming out have not used the appropriate tool/bar to get this torque or took their car to a "mechanic."
09-15-2016, 11:24 PM
#49
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.
When working on the car I only use that for breaking things lose, never for reassembling and torquing.
