are front brake calliper bolts torque-to-yield?

[jeepster]

I was looking under the front end and spotted one of the brake mounting bolts had come loose. If it is TTY, I should get some new ones. I know later models use TTY bolts, but don't know about VR-VS. Dodgy third-party manual says 115-120 Nm, which implies they are standard hi-tensile bolts.

 

[Deuce]

As far as I am aware, they are a standard bolt and as such I have treated them that way in the past.

 

[losh1971]

Yeah AFAIK they are not TTY.

 

[stick3]

mine are same age as the car over 25 years old

 

[Sabbath']

They're not TTY. Who touched your brakes last? I advise not letting them touch them in the future as they should not just come loose.

 

[shane_3800]

TTY bolts don't come loose if reused that's not how they work.
The lack of understanding on TTY bolts astounds me when people try to replace them.

Yeild is a strech zone on a chart that achives higher clamping loads it does not effect the resistance to loosening.

Just tighten the bolts up tight like the 100,000,000,000 caliper bolts around the world have been done in the past 30 years.

 

[losh1971]

Shane I don't think the OPs question was around the TTI bolts coming loose because they are TTI. His concern was that they might have been TTI and required replacing as TTI are generally one use as you know, because like you said they stretch.

 

[Immortality]

TTY bolts don't come loose if reused that's not how they work.
The lack of understanding on TTY bolts astounds me when people try to replace them.

Yeild is a strech zone on a chart that achives higher clamping loads it does not effect the resistance to loosening.

Just tighten the bolts up tight like the 100,000,000,000 caliper bolts around the world have been done in the past 30 years.

And yet you are wrong.

If you torque a bolt to yield you have taken the bolt into what is called plastic deformation and the fastener is throw away once removed.

All fasteners stretch, that is how the clamp load is achieved ( to create a mechanical joint). Fasteners that are stretched but return to their original length (when removed) is called elastic deformation and this is what normal fasteners do. If the fastener is stretched to the point it does not return to it's original length the fastener has yielded and should not be re-used.

If a TTY fastener is re-used it will not provide the correct clamp load and could potentially come loose or worse fail catastrophically

It is poor form for you to tell people to re-use TTY bolts when manufacturers recommend TTY bolts are discarded once removed. If you wish to re-use TTY bolts that is your preogative but please stop giving bad advice in regard the use of TTY fasteners.

 

[shane_3800]

And yet you are wrong.

If you torque a bolt to yield you have taken the bolt into what is called plastic deformation and the fastener is throw away once removed.

All fasteners stretch, that is how the clamp load is achieved ( to create a mechanical joint). Fasteners that are stretched but return to their original length (when removed) is called elastic deformation and this is what normal fasteners do. If the fastener is stretched to the point it does not return to it's original length the fastener has yielded and should not be re-used.

If a TTY fastener is re-used it will not provide the correct clamp load and could potentially come loose or worse fail catastrophically

It is poor form for you to tell people to re-use TTY bolts when manufacturers recommend TTY bolts are discarded once removed. If you wish to re-use TTY bolts that is your preogative but please stop giving bad advice in regard the use of TTY fasteners.

No you're incorrect. TTY are brought to the point of yeild where they retain elasticity this is how they clamp.
Look up the specs on Toyota 4cyl head bolts from about 2002 to 2012 they have a max length spec.
So they're reuseable even though they're torque to yeild.

When a bolt is brought into the yeild zone which is a large area on a graph it will strech a little and the yeild zone will change next time it is used. It's not plastic deformation that only happens if you exceed the elastic zone of the yeild curve. When this happens the clamping force will drop slightly before shooting up. This section where the bolts force shoots up is the plastic zone where it's about to break.

You obviously don't fully understand torque to yeild bolts.

 

[woteva]

No you're incorrect. TTY are brought to the point of yeild where they retain elasticity this is how they clamp.
Look up the specs on Toyota 4cyl head bolts from about 2002 to 2012 they have a max length spec.
So they're reuseable even though they're torque to yeild.

When a bolt is brought into the yeild zone which is a large area on a graph it will strech a little and the yeild zone will change next time it is used. It's not plastic deformation that only happens if you exceed the elastic zone of the yeild curve. When this happens the clamping force will drop slightly before shooting up. This section where the bolts force shoots up is the plastic zone where it's about to break.

You obviously don't fully understand torque to yeild bolts.

At least learn how to spell it before you say everyone else is wrong.

A torque to yield fastener (TTY) or stretch bolt is a fastener which is torqued beyond the state of elasticity and therefore undergoes plastic deformation, causing it to become permanently elongated.