9

I'm reinstalling a threadless stem after cleaning and degreasing.

There are two sets of bolts: the faceplate bolts that attach the handlebars to the stem and the pinch bolts that clamp the stem to the fork's steerer tube. To be clear, since some discussion I've read online just uses a catch-all term "stem bolts", these are what I'm talking about:

Stem Bolts

Source

For each of these sets of bolts, should I use grease, threadlocker, anti-seize, or nothing (dry)? And if the answer for either is anti-seize, what is the next best option if I don't have access to anti-seize?

The Park Tool article linked above says grease or threadlocker for the faceplate bolts, but doesn't specify for the pinch bolts. Elsewhere, the Park Tool Guide to Bicycle Lubricants and Compounds says "Medium-strength threadlocker can be used on threaded bottom bracket cups, disc brake rotor bolts, stem bolts, etc," with no distinction between the two types of bolts.

FWIW, it appears the bike came stock with grease and I've never had issues with handlebars slipping in 12 years.

Thanks.

2 Answers 2

14

Any of the choices except dry will be fine in most use cases. (This assumes a medium strength threadlocker).

Lubrication on torque-sensitive fasteners is important. When your goal is to achieve a certain amount of thread preload, you need to reduce factors that cause your torque input to result in some amount less preload. You can measure torque, but not preload. The list of such potential factors is long (materials, finish, tolerances, condition, quality of machining, etc.), and lubrication vastly reduces the effects of most of them. Lubrication also prevents corrosion from seizing the fastener.

Grease and anti-seize do a similar job of reducing the effects of these sources of added friction. Anti-seize is better in very corrosive environments. It has the downside of being very messy to work with and has some material compatibility concerns that should be abided by. The major one that comes up with bikes is that theoretically, copper anti-seizes can cause failures in stainless parts by "inter-crystalline corrosion which can cause parts to crack or break when under heavy loads." Stem bolts are an area where this is a factor since many stem bolts are stainless. I have no idea what it would take to get the copper-on-stainless issue to occur on stem bolts, but using a silver grade (aluminum base) is better. Anti-seize is fine to use if it's what you have or if the application has specific corrosion or galling concerns, but otherwise is overkill. The messiness factor is real if you're working with it often.

Grease is the norm for most bike applications, including stem bolts, and will usually provide all the lubrication and corrosion protection needed. In the kinds of heavily corrosive environments bikes need to deal with (maritime, salted roads, etc.), using anti-seize over grease offers marginal safeguards, but grease is typically enough to prevent seizure even over a long service life. The basket cases tend to involve parts that were assembled dry.

Medium-strength threadlocker does an acceptable job of providing lubrication and blocking out corrosion while adding protection against the threads backing out. The main reason it would ever back out in a stem or most other applications on a bike is inadequate torque - this is not a concern in most cases otherwise. Stem manufacturers probably like that it provides a degree of safeguard against poor installation while doing everything else needed, so it's found a home on stem bolts. Compared to the alternatives, threadlocker is most likely to stop working with repeated installations since it will flake off when the bolts are out, so it does have the disadvantage of potentially needing to be re-applied where the other two are more persistent.

2
  • Is it necessary (or desirable) to chase the thread to remove the old threadlocker? Apr 4, 2023 at 14:27
  • 1
    @AndrewMorton Not with bikes. If you had an application where things vibrating loose was a huge concern and you really needed to know the threadlocker was going to do the best job possible, then getting the threads down to bare, degreased metal would make sense. It will also block out corrosion best if left undisturbed after being allowed to set up that way. Apr 4, 2023 at 14:59
5

Anti-seize prevents galvanic corrosion between titanium and other metals - actually, it should prevent galvanic corrosion between any two metals with different electrode potentials. Conventional wisdom is to use copper anti-seize where any one component is titanium.

How many stem bolts are made of titanium? If uncertain, you can check with a magnet. Titanium is not as strong as steel in this application. I don't know how many stems use ti, and I would expect ti bolts to be less common on MTB stems like pictured. In the weight weenie days, you would frequently find ti bolts on lighter road stems (again, not sure about MTB stems).

If you don't have access to anti-seize and you have a ti component, you can just use grease. You might wish to check the component more regularly, particularly if you ride in the rain or on a trainer - the more water, the faster galvanic corrosion will occur.

Threadlockers are like glue. For press fit BB installations, people commonly use threadlocker as a safety measure. In theory, if the frame and BB are within their specified tolerances, threadlocker may not be necessary, but it's a low-cost preventive measure that should help eliminate creaking - it's a bit like how teflon tape on threaded BBs was (and perhaps still is) a commonly done thing. On bolts, you would use threadlocker if you had problems with the bolts working loose. I am not sure how often this occurs on good quality components. I had the B-tension screw on my Ultegra rear derailleur inexplicably work its way loose a couple years back, and I threadlocked it. Yes, this is a rare failure, and I swear it did happen.

3
  • Shouldn't it read thread locker for threaded BB and retaining compound for press fit BB?
    – gschenk
    Apr 3, 2023 at 7:46
  • FSA makes a ¹ PF30 BB adapter to threaded BCA is pressed in the bike and loctite comes shipped with it for the press-fit aspect of it's install.
    – Jeff
    Apr 3, 2023 at 13:40
  • @gschenk that's a fair point. I had the two substances conflated in my head. however, do we know that thread locker and retaining compound are different chemistries, or do they do pretty different things? I thought they were the same general class of substance
    – Weiwen Ng
    Apr 3, 2023 at 15:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.