are front brake calliper bolts torque-to-yield?

[vc commodore]

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.

TTY bolts are single use bolts and single use only...If you choose to use them a second time, do so at your own peril....Oh and any mechanic that reuses a TTY bolt on a paying customers car, shows they are shonky...

To answer the OP's question...No they aren't a single use bolt...Who ever touched those bolts last either didn't do them up properly, or has cross threaded them in some shape or form

 

[Immortality]

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.

I'd bet my lecturer at tech would disagree with you. That toyota bolt in a specific example because the manufacturer has given a specific length to check it against. 99% of TTY bolts do not have this and are throw away after use.

When a fastener is taken to yeild it is plastic deformation and it has NOT returned to it's original length. Go and do some learning.

It's funny, you just proved my point,

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.

With a TTY bolt, you don't know to what point the manufacturer has originally taken the bolt so when you re-use it you don't know how close the bolt is to failure and the exact reason you DON'T re-use TTY bolts (except that specific example where the manufacturer has given a free length for the fastener). Yes yes, I know that you can "feel it" with your expensive Snap on torque wrench you keep telling us but that is not the proper way. Taking a fastener to the point where you feel it going soft is way past where it should have ever gone.

 

[shane_3800]

I'd bet my lecturer at tech would disagree with you. That toyota bolt in a specific example because the manufacturer has given a specific length to check it against. 99% of TTY bolts do not have this and are throw away after use.

When a fastener is taken to yeild it is plastic deformation and it has NOT returned to it's original length. Go and do some learning.

It's funny, you just proved my point,



With a TTY bolt, you don't know to what point the manufacturer has originally taken the bolt so when you re-use it you don't know how close the bolt is to failure and the exact reason you DON'T re-use TTY bolts (except that specific example where the manufacturer has given a free length for the fastener). Yes yes, I know that you can "feel it" with your expensive Snap on torque wrench you keep telling us but that is not the proper way. Taking a fastener to the point where you feel it going soft is way past where it should have ever gone.

I've had an argument with a mechanical engineer. I was telling him LSX head bolts should be replaced.
He explained he had strain tested the bolts and there's numerous articles on google explaining how to re-use them. He said one of his LQ4 turbo builds has re-used bolts making 800hp. He also reused all the gaskets. It was a junkyard engine he was prooving the point.

 

[vc commodore]

I've had an argument with a mechanical engineer. I was telling him LSX head bolts should be replaced.
He explained he had strain tested the bolts and there's numerous articles on google explaining how to re-use them. He said one of his LQ4 turbo builds has re-used bolts making 800hp. He also reused all the gaskets. It was a junkyard engine he was prooving the point.

So on one hand you are saying re-use TTY bolts and on the other hand your saying don't re-use them...Talk about giving conflicting advise

 

[Immortality]

I've had an argument with a mechanical engineer. I was telling him LSX head bolts should be replaced.
He explained he had strain tested the bolts and there's numerous articles on google explaining how to re-use them. He said one of his LQ4 turbo builds has re-used bolts making 800hp. He also reused all the gaskets. It was a junkyard engine he was prooving the point.

Do you strain test sets of used bolts to workout if they are within tolerance?

The only true way to know if a fastener has the correct clamp load is by measuring the bolt stretch, unfortunately in most situations this isn't possible (the best example of it been done correctly is rod bolts fitted using a stretch gauge with a micrometer). When it isn't possible to measure the stretch in the fastener, the bolt fastener torque is used instead unfortunately this is only an approximation because as you well know the torque reading you get can vary greatly depending on a range of factors.

There are many factors that effect the use of the fastener. IF THE MANUFACTURER SAYS TO DISCARD THE FASTER AFTER REMOVAL than it is best to follow this advice. Just because Toyota give a length for a specific set of bolts DOES NOT mean you can apply a similar line of thought to other fasteners.

edit: and yes, re-using MLS type head gaskets (as fitted to LS engines) is nothing new either, just separate the layers, clean and spray with sealer (like copper gasket spray) and they are generally good to go again.

 

[Immortality]

Some light reading for your morning bus ride.

https://www.hextechnology.com/articles/bolt-yield/

 

[vs-lover]

All this talk just re-enforces my thoughts of never taking any of my cars to a "so-called" mechanic. I learnt that way back in 1984 when I took my then near new GJ Sigma to Girlock Brakes for a shuddering brake issue, only to have it redone 4 weeks later by them and then again another 4 weeks later.

So from there I lost all faith in the mechanical trade and decided to educate my self with the genuine Workshop Manuals for what ever car I owned and only allowed myself to work on the said cars. Yes certain bits and pieces had to be contracted out such as Disc Machining etc.

Here we are umpteen years later and I've learnt so much and saved so much money that I can do almost anything on my cars to keep them looking A1 and also running A1.

 

[shane_3800]

All this talk just re-enforces my thoughts of never taking any of my cars to a "so-called" mechanic. I learnt that way back in 1984 when I took my then near new GJ Sigma to Girlock Brakes for a shuddering brake issue, only to have it redone 4 weeks later by them and then again another 4 weeks later.

So from there I lost all faith in the mechanical trade and decided to educate my self with the genuine Workshop Manuals for what ever car I owned and only allowed myself to work on the said cars. Yes certain bits and pieces had to be contracted out such as Disc Machining etc.

Here we are umpteen years later and I've learnt so much and saved so much money that I can do almost anything on my cars to keep them looking A1 and also running A1.

The issue is though if every other workshop re-uses caliper bolts and you're the only work shop that charges the extra $20 a bolt you don't win quotes.
A lot of cars are comming out with TTY bolts for the brakes.

 

[Pollushon]

All this talk just re-enforces my thoughts of never taking any of my cars to a "so-called" mechanic. I learnt that way back in 1984 when I took my then near new GJ Sigma to Girlock Brakes for a shuddering brake issue, only to have it redone 4 weeks later by them and then again another 4 weeks later.

So from there I lost all faith in the mechanical trade and decided to educate my self with the genuine Workshop Manuals for what ever car I owned and only allowed myself to work on the said cars. Yes certain bits and pieces had to be contracted out such as Disc Machining etc.

Here we are umpteen years later and I've learnt so much and saved so much money that I can do almost anything on my cars to keep them looking A1 and also running A1.

What you'll notice is it's mostly when Shane is invoved that simple things become semantic arguments. I agree though, no one has a vested interest in a good job on your car like you do.

My rule of thumb next to reading the manual is look at the thread locker. Commodore brake calipers use blue - servicable = not TTY. If a bolt uses red - non-servicable = likely TTY but either way should be replaced.

Sure you can reuse a TTY bolt but why would you? Especially if you've dropped a wad of coin? When hardened/tempered metal of any kind is deformed it has lost its integrity and should not be trusted. Just because a junkyard LS runs okay with reused TTY bolts doesn't prove anything aside the risk profile of the 'engineer'.

 

[lmoengnr]

What you'll notice is it's mostly when Shane is invoved that simple things become semantic arguments. I agree though, no one has a vested interest in a good job on your car like you do.

My rule of thumb next to reading the manual is look at the thread locker. Commodore brake calipers use blue - servicable = not TTY. If a bolt uses red - non-servicable = likely TTY but either way should be replaced.

Sure you can reuse a TTY bolt but why would you? Especially if you've dropped a wad of coin? When hardened/tempered metal of any kind is deformed it has lost its integrity and should not be trusted. Just because a junkyard LS runs okay with reused TTY bolts doesn't prove anything aside the risk profile of the 'engineer'.

Yes! Most Commodore caliper bolts are 'single use' because they're micro-encapsulated with thread locker.
Just apply Loctite and reuse...
Junkyard engines are just that, junkyard engines...