Was this bolt over-tightened

[bw77]

Pic shows 4 rear caliper bolts that I removed from my car.

Looking at the one on the right - does it look like that bolt
was over-tightened last time it was installed (at dealership)?

The cross-section at the top of the threaded part does
not look right.

I used 4 new bolts.

 

[PT Doc]

Oh no they didn't use a torque wrench.

 

[slotard]

2 looks a little suspect as well

 

[theoldwizard1]

Could have stretched when removing ?

 

[neel2008]

Oh no they didn't use a torque wrench.

you don't need a torque wrench for caliper bolts really.....just common sense.....which also wasn't used.

 

[Certified Drunk]

Who use's a torque wrench or common sense, when you have an impact gun.

 

[krivasgarage]

I think #4 was on Jenny Craig.

 

[Gary S]

you don't need a torque wrench for caliper bolts really.....just common sense.....which also wasn't used.

That's why we have torque wrenches and torque charts. People today don't have common sense.....................but, I'm not sure they can read the chart and use a torque wrench either.

 

[srmofo]

wow, ive never seen that before...they must have been hammering on those things to get them to stretch like that

 

[ddawg16]

The really surprising part.....the bolt didn't break.....

Tells me that the hardness is not where it should be....

 

[darkk]

Yup and you are just lucky it came out in one piece...

 

[Thruxton]

you don't need a torque wrench for caliper bolts really.....just common sense.....which also wasn't used.

Good video somewhere on youtube (I probably saw it here) - some mfr at a trade show inviting folks to see how close they could come to proper torque on a fastener without a torque wrench. Basically a big FAIL exercise.

The really surprising part.....the bolt didn't break.....

Tells me that the hardness is not where it should be....

Hardness and ductility (yield strength) aren't the same, these could easily be the correct grade fasteners.

 

[nosnownogo]

We had some clowns at work trying to torque fasteners with a snapon dial type torque wrench 0 to 50 inch pounds .The torque required was 85 .So they would torque to 50 ,
and continue holding the tension then reset the dial to 0 and crank another 35 .These must be the same people who use micrometers as metal clamps and verniers as adjustable
wrenches.

 

[Daniel Dudley]

Could have stretched when removing ?

No, they shear when removing.

 

[Big-Foot]

Possibly a "torque to yield" that was pushed just a wee bit too far...

 

[bw77]

I agree. Spec is 45 ft lbs.

 

[Steve91T]

I bought some exhaust manifold studs from an auto parts store. It said Grade 5 on the box. I ran the studs in and then started torquing them. Snugged them all at right, then torqued them to 20 ft/lbs, then finally to 30 ft/lbs, which is the proper torque. I couldn't get any of them to reach 30 ft/lbs. It honestly felt like the threads were stripped. One of the studs snapped. Fortunately, I was able to remove the broken stud.

Anyway, the bolts were stretched just like what the OP posted. That's what cheap Chinese metal does. I found some grade 8 bolts and all is well.

I could have been that someone just used really cheap bolts. I wouldn't have believed it if it didn't just happen to me.

 

[Big-Foot]

Another thought...

Those bolts have Loctite on them.

It is possible that someone had used an acetylene torch and overheated that particular bolt. Just hard to imagine that unless the bolt was designed with a softer spot like torque to yield, that it would stretch like that without breaking.

 

[bw77]

I could have been that someone just used really cheap bolts.

It looks to me like they are the original bolts on
this 1999 Volvo, reused twice.

Maybe that is why the bolt was stretched - reused
twice instead of replaced. Factory manual says to replace
the bolts.

 

[BigE]

Yup, by that description in the manual, they are torque-to-yield bolts. The strength of a metal is characterized by 3 conditions: forces that cause no permanent change to the metal, forces that cause the metal to change shape and forces that cause the metal to break. That bolt reached the second stage and almost the third. Typically, TTY bolts are right on the edge between the first and second stage to give maximum clamping force. It looks like someone overtightened or overused at least two of those bolts. They are weaker now because 1) they have been stretched lengthwise and 2) the cross section of the bolt is smaller which reduces the amount of force it can stand. Good call on replacing them.

 

[ATC]

They are stretched. I had that happen to the oil filter cover bolts on my old fourwheelers. I just replaced with grade 8 and called it good

 

[wishihadatalon]

MMMM plastic deformation.

 

[pipsters]

It looks to me like they are the original bolts on
this 1999 Volvo, reused twice.

Maybe that is why the bolt was stretched - reused
twice instead of replaced. Factory manual says to replace
the bolts.

Yeah but that is because they put loctite on the factory bolts. Only reason to replace them if you don't put loctite on them again. BTDT got the T-shirt...

Torque to yield bolts should be replaced, if they aren't torque to yield (these aren't) there is really no reason to replace them from a structural integrity viewpoint AFAIK.

 

[Blue98GT]

TTY bolts are supposed to stretch a little. Consider the slinky metaphor- if you stretch a slinky a little, it will retract and stack normally when released. If you stretch it 10 feet, it deforms (your bolt) and will no longer stack. TTY bolts are meant to be stretched once becuase the next time they get stretched like that they will deform. Odd to have TTY bolts on brake stuff. Seems like loc-tite would do.