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Lock-tite or Ti prep on Ti rotor bolt? Came loose on Ti prep.

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Suns_PSD

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Discussion starter · #1 ·
I bought some Ti brake rotor bolts, put some Ti prep on them and torqued them to 4 NMs. After 3 rides the front rotor came loose.
Do I up the torque or swap to lock-tite on the Ti threads?
Thanks.

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#2 ·
I use lock-tite without issue and ride in the PNW. If you're concerned with corrosion you could use the stuff that cures in air and apply the prep as well.
 
#3 ·
I double-checked, and Magura, and Shimano (for their 6-bolt versions) do indeed recommend a max of 4Nm of torque.

That said, I've been using Ti bolts, with just prep for years, and have never had any come loose - not a single bolt. You shouldn't have to use loc-tite - I almost wonder if your wrench is significantly out of calibration. (?)
 
Discussion starter · #6 ·
phlegm said:
I double-checked, and Magura, and Shimano (for their 6-bolt versions) do indeed recommend a max of 4Nm of torque.

That said, I've been using Ti bolts, with just prep for years, and have never had any come loose - not a single bolt. You shouldn't have to use loc-tite - I almost wonder if your wrench is significantly out of calibration. (?)
Click to expand...
It's a thought. Just re-torqued to 5nm with no other changes.
I had tightened the front rotor bolts on the trail yesterday so they were fine. However the rears rotor bolts were coming loose as well.
And yes, my concern with using lock-tite is that the Ti bolts will cold weld to my hubs in time.
Maybe I can use both compounds, just add lock-tite without cleaning off the Ti- prep?

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#10 ·
How would aluminum cold weld itself across the distance of a 5mm bolt? Anybody have any literature on this phenomena? Surely the concern is oxidation/galvanic corrosion?... to which loctite is also an adequate barrier to my understanding.
 
Discussion starter · #14 ·
Well the size of the bolt/ nut in large part determines how much torque is required, not the item being held.

And I have 6 small bolts compared to 1 larger nut for CL rotors.

Anyways, it's done, 4 NM with blue locktite.
 
#15 ·
Suns_PSD said:
Never heard of that, makes sense however. Thx
Ti is strong, no concerns of them failing.

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Click to expand...
Sorry missed this comment. I'll try to find a scientific article but cold welding is super common with ti components, everything from brake bosses to seatposts are at risk. Aluminum is less common but ti to al happens as well.
 
#18 ·
Antisieze helps to prevent galvanic corrosion by providing a metal that will give away its ions. In case of ti and aluminum the ti will steal ions from the aluminum, but if antisieze is present then it will take from the zinc instead.

Removable threadlocker seals the threads away from air and water which also hugely reduces galvanic corrosion. By protecting the threads from corrosion it prevents the bolt from loosening.

I've never seen corrosion on a bike without water present. Im sure its possible with enough time but ive never seen it.

With water present i've seen a steel bolt turn surrounding aluminum into a sponge that i could break with my hands, and titanium is hungry-er than steel.

In neither of these cases is the compound going to prevent loosening until corrosion has occurred, like others have said its the bolt stretch from proper torque that keeps bolts tight. Ti is stretchier than steel so the steel torque spec should have been adequate.

I dont know what the perfect approach is here. I would use locktite 242... Same as i use for my steel brake bolts.

Wikipedia has good description of galvanic corrosion.

Torque wrench: A beam style wrench is almost infallibly accurate. I have a cheap small nieko from amazon and i love it. Torque on small bolts is important, very easy to overtighten and wreck something expensive.
 
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#19 ·
eri said:
...

Torque wrench: A beam style wrench is almost infallibly accurate. I have a cheap small nieko from amazon and i love it. Torque on small bolts is important, very easy to overtighten and wreck something expensive.
Click to expand...
Excellent post. Pretty sure calibration can be put off if the wrench in question has been dropped - perhaps a few times over the years, so perhaps not infallible.

I suspected a wrench issue in my earlier reply because the torque setting the OP references is the one also suggested by known manufacturers, and I use the same amount. I've never had a bolt go loose with just Ti prep, so suspected unintentional under-torquing, although agree it is probably rare.
 
#20 ·
phlegm said:
Excellent post. Pretty sure calibration can be put off if the wrench in question has been dropped - perhaps a few times over the years, so perhaps not infallible.

I suspected a wrench issue in my earlier reply because the torque setting the OP references is the one also suggested by known manufacturers, and I use the same amount. I've never had a bolt go loose with just Ti prep, so suspected unintentional under-torquing, although agree it is probably rare.
Click to expand...
Cheap Non-beam type torque wrenches... sometimes that means a lubed notch and a spring. Dropping can hurt their accuracy, but the cheap spring loses its force over time. Owner does nothing wrong and it still lies.

reminds me of that far side comic where the scowling witch is being yelled at by the parents: "Let me get this straight... we hired you to babysit the kids and instead you killed and ate them both?"

Someone went to the trouble of buying a torque wrench AND they bothered to use it, and then it lies to them? It's the very opposite of getting your moneys worth.

And all the time customer could have bought a beam wrench, technology from the 1920s which pretty much only depends on a metals Reynolds number for accuracy. If the steel beam isn't cut or badly bent and the zero is centered then you know it's accurate. Period. So cool.
 
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