Torquing to Spec

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I did my front brakes today, and I was surprised to see what the torque was on the caliper pins and bracket bolts. Both were much higher than spec coming off. It made me wonder a little about whether the last person putting everything back together torqued everything to the right specs. How often do you think that mechanics actually torque to spec on brakes? Best, ET16
 
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I would be surprised if professional mechanics ever use a torque wrench on brake caliper pins. How did you determine the original torque? It's not uncommon to take more torque to break free or loosen a bolt compared to the tightening torque. I would guess that most car caliper pins are in the 25 to 35 lb. ft. range, give or take a few pounds?
 

ET16

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I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench. I suppose it could have just been rusted, but I checked the torque coming off another car that I did a brake job on two weeks ago and the torque coming off was much closer to spec.
 
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FWIW, Honda dealership I worked once, I was told to use a hand wrench "tight" but not screaming tight. No torque wrench.
 
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German torque spec: "gutentight" ;-) As a professional mechanic, as much as I would like to torque each and every bolt, I simply cannot. Good mechanics have a feel for how tight a bolt should be based on size, thread pitch, etc. I would venture that I can get pretty close to torque spec by hand on 90% of bolts. Some things to keep in mind: -Bolts rust and get hard to break loose -There is no accurate way to measure amount of torque to loosen a bolt with common hand tools. Due to bolt design, any given bolt will always take more torque to loosen than the tightening spec. IE: after tightening to 80ft/lb does not mean 80ft/lb to "break loose". That being said, most mechanically inclined people have a good grasp of a bolt that is "too tight" when trying to loosen it. I wouldnt be surprised if your brake calipers were overtightened, most mechanics seem to over do it a bit. I tell ya, finesse is something many don't have, people need to realize that most of the time "just snug" is just fine! Once you surpass the bolts elastic range, it isn't the same.
 
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 Originally Posted By: AcuraTech
Once you surpass the bolts elastic range, it isn't the same.
+1 I've seen wheel lugs stretch and crack from really pounding on them--to tight is too weak sometimes.
 
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 Originally Posted By: AcuraTech
German torque spec: "gutentight" ;-) As a professional mechanic, as much as I would like to torque each and every bolt, I simply cannot. Good mechanics have a feel for how tight a bolt should be based on size, thread pitch, etc. I would venture that I can get pretty close to torque spec by hand on 90% of bolts. Some things to keep in mind: -Bolts rust and get hard to break loose -There is no accurate way to measure amount of torque to loosen a bolt with common hand tools. Due to bolt design, any given bolt will always take more torque to loosen than the tightening spec. IE: after tightening to 80ft/lb does not mean 80ft/lb to "break loose". That being said, most mechanically inclined people have a good grasp of a bolt that is "too tight" when trying to loosen it. I wouldnt be surprised if your brake calipers were overtightened, most mechanics seem to over do it a bit. I tell ya, finesse is something many don't have, people need to realize that most of the time "just snug" is just fine! Once you surpass the bolts elastic range, it isn't the same.
You also touch on a physics concept pertaining to friction. The coefficient of static friction is always higher than the coefficient of kinetic friction. This means that it is usually harder to get something moving than to keep it moving.
 
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 Originally Posted By: ET16
I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench.
30 ft lbs. to remove a pin isn't much. Every brake job I ever did, I torqued them by hand.
 
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 Originally Posted By: ET16
I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench.
NEVER use a torque wrench to loosen bolts!
 

PT1

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 Originally Posted By: AcuraTech
I tell ya, finesse is something many don't have, people need to realize that most of the time "just snug" is just fine!
I own a Harley Davidson...once you have lived at "The House of Harley" you want to torque your gas cap on. So, I torque everything to spec.
 

ET16

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 Originally Posted By: Zaedock
 Originally Posted By: ET16
I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench.
30 ft lbs. to remove a pin isn't much. Every brake job I ever did, I torqued them by hand.
It was actually 30 ft lbs more, something like 100-120 ft. lbs. on the bracket bolts.
 
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 Originally Posted By: The Critic
 Originally Posted By: ET16
I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench.
NEVER use a torque wrench to loosen bolts!
+1
 
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It always takes more to loosen a fastener than to tighten it. Especially if it has been assembled for a while. If yours were loose, they were not initially tightened properly.
 

ET16

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 Originally Posted By: demarpaint
 Originally Posted By: The Critic
 Originally Posted By: ET16
I agree that there's normally more torque coming off, but I think I had 30 or more ft. lbs. more than spec coming off the bracket bolts. I almost couldn't get one off, and that was with the torque wrench.
NEVER use a torque wrench to loosen bolts!
+1
I was just curious to see what the torque would be coming off. I wanted to see how close it was to spec.
 
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The only thing I use a torque wrench on is head bolts. I have been shade treeing for 40 yrs, so I pretty much work by feel. Been ages since I sheared a bolt or had something loosen up
 
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I use the German torque spec: good and tight.Some caliper pin bolts I tighten with my Snap On FAR7200 air rathet which are tight on the spot.If any of them are a torx or hex head,break them loose by hand first.I hate what GM does,put in chincy caliper braket bolts,a 12mm bolt with a 13mm head which round off very easily.
 
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You can use a beam or dial type torque wrench for removing bolts. that is the proper way to measure "breakaway torque" and "running torque". http://www.boltscience.com/pages/quality.htm Breakaway torque is always greater than the initial torque spec. Static vs dynamic friction is one of the factors at play. You shouldn't use a click type torque wrench because you can damage the mechanism in the torque wrench. The main concern being that you apply more torque than the wrench is set at adding stress to the wrench.
 
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The beam type torque wrenches are worthless,hard to read and I would throw them away.I like the clicker type better
 
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