I was watching this video: https://youtu.be/LuJmbEmh7vY?si=M7f8KiRHI7U78GWv
and at 7:30 they put grease in the screw holes for the stem.
I've wrenched on a number of other things other than bikes, and this is not standard practice. IME with screws like this you would use blue loctite and then possibly even use aviation security paint or even just some improvised version of a "witness mark" so you could visually tell if the screw was backing out.
I have my bike currently just kinda together and am waiting for the weekend to finish.
So do I really want to grease the screw holes? I know I don't want to get it where it isn't wanted, but this seems like just asking for them to back out with my "other than bike wrenching".
Should I really back out the screws and grease them?
by CCCCLo0oo0ooo0
8 Comments
This is extremely google-able information.
grease allows for proper torquing of a fastener, while also preventing corrosion. It does not allow them to back out.
Loctite is the proper way to do it but grease also work. You just want something to cover the threads so it doesn’t rust. The important thing is to torque it to spec.
Blue thread locker on critical bolts is okay to use here. Many people use grease, torque to spec and happily ride on.
Aluminum corrodes and oxidizes when exposed to salt from sweat and moisture, grease does help mitigate the potential for this to occur in a way that thread locker does not. If using thread locker, just check and relubricate your bolts periodically. Once a season? That’s my answer to, “how long is a piece of string?”
Sometimes loctite is appropriate but usually it’s grease. Bikes break down and need to be fixed. It would really stink for any mechanic if every bolt was loctited.
when Using a lubricant (anti seize, thread lock), you should torque to 10-20% lower than specified torque, which is normally for a clean/dry fastener.
When using a lubricant such as thread locker or anti-seize, you need to torque at 10-20% of specified torque. torque is usually specified for a clean/dry fastener. Using grease seems to be a cheap way out—use proper anti-seize for type of metal.
Stem bolts are expected to be frequently… well, relatively frequently removed compared to other fasteners on a bicycle. Want to service your headset? Change stack height/feel, rotate the bars out of the way for transport, etc. then you will be messing around with your stem bolts. For that reason, grease (or anti seize) makes more sense than blue Loctite. You are free to use threadlocker but if the bolts are correctly installed to clamping force, you don’t need threadlocker.
For most fasteners, it’s mechanics preference. You are way over thinking it if you think security tape or a witness mark is needed on a stem. If it gets loose, you’ll know immediately by feel as the handlebars are something you touch every time you ride and if the stem were loose, you are going to start feeling play in the headset. There might be a slight delay until the topcap starts to back out, but you’ll absolutely notice.
If you already put blue loctite on there, that’s fine. You can grease right over the blue loctite and you don’t have to bother doing that until the next time you remove the bolts. If you put nothing on there? It’s fine for now and there’s no pressing need to disassemble, but you should lubricate those particular bolts.
You say that you have wrenched on a number of things, but you also seem to be under the impression that grease on threads will cause them to loosen. These two things aren’t in sync with one another. What matters is clamping force… so long as you achieve that, the fasteners will be locked in place and it will not loosen. If you don’t apply sufficient clamping force, then it will loosen. It will loosen faster, with grease combined with insufficient clamping force, for the reason that’s obvious to you. But the reason a lack of grease would better hold the bolt in place is the same reason you want to use grease in the first place… to prevent galling due to lack of lubrication.
Grease also helps to prevent cross-threading during installation, and it helps to prevent galvanic corrosion of dissimilar metals (aluminum stem and stainless bolt). Due to lubricating the fastener, it will also make it easier to achieve clamping force with a relatively lower torque. Whether torque specs require grease or are for no grease, is a can of worms question on here and I’m not going to argue with anyone on that topic; but I’ll state my position is to always add some sort of lubricant unless the manufacturer explicitly states not to, and I assume the given torque spec is for a lubricated fastener. When in doubt, contact the manufacturer.
When to use threadlocker.. parts that vibrate or you don’t expect to touch again.. so, brake caliper bolts after it’s been adjusted for safety and to hold the caliper in the desired alignment.. you’ll sometimes see lock tabs or lock wire in these places but it’s infrequent. You also generally use a threadlocker for the bolts that hold racks, bottle cages, fenders, and that sort of thing in place.
I prefer anti seize for BB shell cups and pedal axles. I tend to use grease for fasteners everywhere else.
(edit to add) because you mention how things are approached “everywhere else.” I’m an industrial mechanic and former USN nuke mechanic; bikes are a hobby, but being a mechanic is my professional job and training. Somethings don’t get greased.. lug nuts on a car are a good example. No reason to lubricate compression fittings either. It just depends on what you are working on, what materials are involved, what if any chemical exposure will take place, etc. Common practice tends to be very industry specific.