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Can I use lithium (lithium soap based) grease for lubricating the steel headset cups when pressing them into the aluminium frame?

I mean cups, not the bearings inside them.

Is it good for preventing corrosion on steel/aluminium contact?

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Yes, totally suitable. Of all the remotely common grease types, there's not really a scenario on bikes where the type matters for this application unless it's a titanium or stainless frame, and then use anti-seize.

As someone who presses things into bike frames on a regular basis and lives/works in a rainy climate, I do always use grease, but it's primarily for information, not corrosion resistance. Greasing the surface every time comes close to normalizing the contribution that surface friction makes to the force required, so problems with the press fit are easier to pick out in both the too loose or too tight direction.

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  • 1
    "information" ? Not sure what that means here.
    – Criggie
    Apr 14 at 22:42
  • 4
    It's the same principle as greasing fasteners to make the reading from a torque wrench more meaningful. Some variance in surface friction remains, but it becomes an amount much closer to zero relative to the force required by the interference fit, or to preload the threads by the target amount in the case of a torque wrench. Apr 15 at 0:30
  • 2
    @Criggie I believe in this context information means tactile feedback. Apr 16 at 18:40
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Grease will do much more to protect it than nothing, with many mechanics preferring marine-grade grease if near the ocean or salted roads. Optimally, you should use an anti-seize compound. In general:

  • Grease - Parts that always move and are protected (bearings and shifting system). For operating temperatures and pressures of bikes, the type of grease is pretty irrelevant unless you are in extreme temperatures or using a hub brake
  • Oil = Parts that always move and are not protected (chains, brake levers)
  • Anti-seize - Parts which are friction fit or threaded that do not need extra holding capacity (most threads). Especially useful for dissimilar metal contact points and is more water resistant than grease. Again, marine grade is preferred.
  • Thread locker - Parts which are threaded that need a bit more friction after torqued down and vibration protection (handlebar clamps, fender mounts). Keep note that removing a fastener after the threadlock is cured will break it's form and require another application.
  • RTV Silicone (clear) - Apply over fastener heads that are not frequently accessed to prevent corrosion of head.
  • Tung/Boiled Linseed Oil - For spoke threads. Crystallizes as viscous "plastic" which allows rotation of nipple without permanently breaking like thread lockers.
  • Dry lubricants (teflon, wax) = Lubricates exposed components (and cable housings) better than oil without attracting dirt in dry conditions only.
  • Carbon paste = Friction enhancer for carbon fiber parts.
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  • Is there any benefit to anti-seize compared to anaerobic liquid threadlocker (where the threadlocker would cure in the space between the threads, preventing direct contact and filling the space so water can’t get in)? I was under the impression antiseize was largely for high-temperature applications where the oil/grease component may burn off. Also thought carbon paste was more about getting clamped parts like seatposts and handlebars to have adequate grip without increasing the clamping force/torque? Are you saying carbon paste prevents seizing, or that it’s for friction fit/threaded parts?
    – Pisco
    Apr 14 at 20:35
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    RTV Silicone should mostly NOT be used, because it produces acetic acid as part of its curing process.
    – Armand
    Apr 14 at 21:07
  • Grease works to (a) lubricate moving parts (even if they are moving rarely, such as screw threads or press-fit cups) and (b) protect against corrosion. It tends to be much less messy than anti-seize, and so is probably the most commonly used chemical in bike work.
    – Armand
    Apr 14 at 21:13
  • Anti-seize is basically a grease with metal particles in it that are designed to be "sacrificial" in a situation of galvanic corrosion. The particles corrode and not the surrounding parts. It's also designed to lubricate to prevent mechanical seizing and (hopefully) corrosion. Thus, it does more than threadlocker, but in practice grease, threadlocker and antiseize are somewhat interchangeable and are used from room temperature on up.
    – Armand
    Apr 14 at 21:21
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    Perfect is the enemy of good - Bike shop should should have all of these (except RTV- put RTV near my bike and you are likely to have something big and heavy thrown at you), A home bike mechanic can get by on one grease and chain lube. Thread locker and carbon paste (if you have carbon) are useful.
    – mattnz
    Apr 14 at 21:58

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