Originally Posted by cat
Something i've been wondering about, related to brake disc bolts...
For Ti disc bolts, bolts (like Pro-Bolt), they always say to use anti-seize because of the galling of Ti. But that bothers me a bit - for obvious reasons. So, i wonder, what is the expert opinion on it?
Stainless and Titanium are both very sticky metals. Not sticky like a piece of tape, but sticky as male and female threads are placed under high sliding loads.
Titanium is stickier than stainless. Because of this stickiness some sort of lubricant is strongly encouraged to lessen the tendency of these metals from cold welding themselves together and causing headaches. For threaded stainless fittings used to seal fluid or air, if some sort of lubricant isn't used, you tighten the widget up and hear a creak, or feel grabbiness of some sort, and the fitting is gonna leak. The creak or grabbiness is the slow moving high load surfaces destroying all sealing ability.
In the application of a brake rotor being bolted to a hub, there's a tremendous amount of loading taking place. This side or shear loading of the threaded fastener actually stretches all components. None of us have the tools to measure the stretching and side loading. If we were to use an anti-seize in this application, grease and metal dust will allow you to tighten the fastener up to the point the proper clamp load has been introduced......BUT, nothing worth mentioning is used to fill the gap created between the male and female thread roots. You're depending on the elasticity of the threaded fastener to maintain a sufficient clamp load. Repeated side loading of the threaded fastener (every time you apply the brakes) might cause loosening. I'd rather not take that risk.
Earlier in this thread I get into the purpose of an anti-seize as it relates to slowing/stopping galvanic corrosion-you'll learn more once you find that post.
Just like an anti-seize, by using a threadlocker on the other hand will give you the same lubricity to achieve the same clamp load, you'll still be dealing with the same degree of fastener elasticity....BUT as side loading is induced (brake application) and as the rotor goes through heating and cooling cycles, you'll never loose the clamp load because the airspace contained between the male and female thread roots is fully supported by a hard thermoset plastic.