Greetings everyone! Some bike mechanics use grease on the threads when they screw the parts, whether there are the threads of a thru axle or the pedals axle and probably other parts or nuts. I think they use grease because it will be easier to unscrew the parts. I understand the reason for the grease usage, but won't adding grease on the threads make the parts come out easier by accident or by vibrations let's say? Since the need for those parts is to stay in place, won't adding grease lower the friction force that keeps the parts screwed and they may come out by accident, and when there is no grease, then they will be more firmly locked in place ? Thank you!

Either way you want to do it. However you should always check to see if the manufacturer has something to say about it. I tend to lube or use anti-seize. But mostly just lube on the bike. As anti-seize can be really hard to get out of clothing if any should get smeared where you can come in contact with it.

On old vintage bikes I did use anti-seize on seat posts and those old style 7 stems for the portion that went in the steerer tube.

Nickle anti-seize. As it's more suited for most any use. Even though bikes aren't going to see the high temperatures it's special for. But again, very limited needs on bikes. And only on my old bikes for me.

Where there is metal-metal contact I put grease or blue LoctTite unless there is a nylon sleeve securing the bolt. This has worked well for 45 or so years.

Use grease. The torque will be more accurate and therefore higher tension holding the bolt.

Greased bolts do not work loose.
They are also less likely to be cross threaded.

When it comes to metal on metal contact, I recommend grease most of the time, unless the manufacturer says otherwise. It is rare I will use a threadlocking compound unless it calls for it is already on the bolt or the bolt has a history of coming loose. Bolts that are properly greased or anti seized and torqued don't usually come loose maybe if it is a really cheap bolt on some rough terrain but usually they aren't coming loose when properly installed but if it does then I employ some mild threadlocker usually a blue color.

Torquing the fastener puts a certain amount of "stretch" in the theads which will "usually" be sufficient.
High vibration etc. loads will probably use a lock washer at a minimum or a thread locker of some degree.
For bicycle use, Green or Blue Locktite. Green is "weaker". I always buy Blue. Both times
Red requires EXTREME heat to remove.

This sums up the situation pretty completely.

Chainring bolts also benefit greatly from grease come disassembly time.

Would you say I need to put grease inside the seat tube between the saddle rod and the interior walls of the seat tube? Won't that make the saddle rod slip down?

Have you considered getting a book or consulting the Park Tool website before you continue doing work on your bike? You seem to not have any knowledge of things like stuck seat posts.

Saddle rod? Is that a cross between a cattle prod and a seat tube?

You have to know what your seat tube and cattle prod seat post are made of. If one or both is carbon fiber, I'd go with carbon fiber assembly paste. CF can be a little slippery. The paste has grit in it to give some friction.

As far as anything getting slippery with grease, when you bind or clamp them, then the skin friction will overcome the lubes friction reducing tendency. With CF made to be light, we can't always put that much clamping force on things to completely overcome the tendency to slip. Unless we damage it or risk damage. So that's where the carbon paste comes in with the grit. The CF stuff could be built to take a large clamping force without assembly paste, but then we'd be giving up the lightness that we pay the big bucks for.

Otherwise, it's still your choice. Even with CF. So make a choice and get some experience. If you have an issue later because of how you did something, then you'll know better what you need to do the next time. Assuming you can make reasonable assessments of why it failed or didn't work well.

Park Tool, as another suggested, does have some good information and videos....... https://www.parktool.com/en-us/blog/repair-help

It's called a seatpost. It shouldn't slip if it's a good fit, if it's not a good fit get one that is - if the slot in the seat tube, by the pinch bolt, narrows toward the bolt then the seatpost is probably too small - open the slot with a large flat screwdriver or similar lever and fit a larger seatpost. If the seatpost is too loose but the next size up is too tight you might need to get the seat tube reamed. If the ears the pinch bolt goes through are squeezed in or the bolt is bent then it's been overtightened - straighten the ears, replace the bolt. Some seatposts will just not play nice - if you've covered all the previous points and it still slips, use carbon assembly paste, which is basically gritty grease, to stop the sliding. Some people recommend using lapping compound, which is also gritty grease but primarily designed as an abrasive rather than grip paste - I'd hesitate to use it anywhere near bearings, but bottom brackets are mostly cartridge bearings so should be immune to grit falling down inside the seat tube.

I will check the Park Tool website. I haven't got the bike yet. Now I am learning everything I need to do when I purchase the bike before riding it. It would be a shame if something were to break or wear because of something so simple as not putting grease on some parts.

I meant seat tube. The bike that I want to buy has an aluminum frame. What is CF ?

Carbon fiber

If you are ordering a bike that will be shipped to you, then be sure to follow their instructions for assembly. If there are conflicts between what they say and what you believe, then call their support line.

If the bike is from a shop that assembled it, then take it back to them for any immediate needs. Typically they do that work for free. And it was probably their mistake in the first place. Which they should see so it can be addressed. Whether it's the mechanic slapping himself or the owner refraining from slapping the mechanic. <grin>

I have not worked with Carbon bikes but on all metals I have successfully used Marine Grease and Permatex Anti-Seize compound...

I worked as an Industrial Mechanic for close to 40 years. Generally, we did not grease bolts. That said, stainless steel bolts and nuts did get a good shot of anti-seize prior to assembly. The anti-seize was to help prevent the occurrence of thread pick-up. Put another way, it is not uncommon for stainless steel fasteners to transfer, as is darn near weld, tread to thread. Perhaps the following, not my words, but certainly what I believe...
"Generally, lubricating bolt threads with grease should be avoided in most cases, especially if a specific torque value is required. While grease can prevent corrosion and ease future removal in some situations, it significantly reduces friction, which can lead to incorrect clamping forces, potential damage to components, and even bolt failure."

If torquing to spec, you need to know if that spec is ungreased or greased. Greased or not makes a large difference in torque for the same amount of fastener tension (what matters most).

No question greasing lowers the friction. But I don't know if that is a given it will accidentally loosen easier.

For example, on pedals it is always recommend to grease them. But the nature of pedals with the respective right and left hand threads, is the loads we place on them are continually working to tightening them. Of course many other bolts like a seat post clamp are not rotating and nothing is trying to tighten or loosen them.

My own experience, I can't remember having any bolt or nut on a bike loosen becasue it was greased. This is assuming it was torqued to spec to start with.

There are no threaded parts on a bike that you'd leave ungreased unless they come with thread compound on them. So it is hard to run into this problem of not knowing how to interpret torque.

found on the web... part of a lengthy thread about this subject... from someone who has actually tested the differences.

"bolts

What holds a bolt in place is stretch.... Think of the bolt as a spring, as you tighten it you stretch the spring.
The kind of lubricant that you put on any bolt will effect how much torque it takes to get the proper stretch. As you're turning that bolt in you have friction areas in the threads and where the bolt head contacts what ever you bolting together. So if you have dirty threads,dry threads, moly,oil etc... this will all change the amount of torque needed to pull a bolt up to a set amount of stretch.

I just spent about 10 hours doing some tests on rod bolts in my shop. You can take the same bolt and get totally different stretch depending on what kind of lube you put on the threads and under the head of the nut.When it come to rod bolts the only way to get the proper stretch is with a stretch gauge. If you are building a stock or close to stock motor you will be fine just using the factory specs for torque on factory bolts (i believe all the manuals recommend oil on the threads)

Try this simple test. Take a block of steel drill a hole through it and put a bolt and nut together thru it dry. Take a set of mic's and check the length of the bolt. Now start torquing the bolt in like 10 ft/lb increments. Check the length after every pull. Take it apart and put some molly lube on it and try again. Record the lengths per ft/lb dry and with molly you'll be surprised!!!! If you really want to get wild try it with different grade bolts...

keith

K-Star Automotive
Performance Engines"

i. as a pro mechanic, working on literally THOUSANDS of different machines thru the decades... always oiled the threads when the torque was critical... to NOT oil the threads could cause a FALSE TORQUE READING due to stiction.
the oil also reduces the chance of galled threads.
Special care MUST be taken when pre-lubing BLIND HOLE THREADS, or a hydraulic lock situation can occur.
i've watched one young trainee FILL the head bolt holes with oil once....the bolts would go in about two turns and Stop.
he got to sop up the oil with pa[per towels... i doubt he'll ever do the hole filling thing again..
if done to excess, in an aluminum casting, the hyd. forces can actually crack the structure around the blind hole... that would, thankfully, require more than two threads.

there are exactly ZERO "High torque fasteners" on bicycles. ZERO.
and grab-jump torquing of old corroded threads leads to totally worthless torque readouts.
rusty steering gooseneck wedges readily come to mind.
i saw one last year that had been OVER-tightened to the point of splitting the el-cheapo fork steerer tube.
i've also seen a draw bolt so badly rusted/galled up that it couldn't be snugged up enough to not twist in the steerer....

lube it or boob it, your choice.
and what stressed part of a bike always works better when the threads are lubed?
there's even "special lube" for those parts....

Spokes and nipples..

the most important thing is CONSISTENCY, not perfect achievement of some dreamed up "Safe Spec".
most CF parts fail to stay put when torqued to that "safe spec"... seat posts and bar clamps rapidly come to mind.
Conclusion: Engineers that Rarely, if Ever, work on anything, dream up what they think is a "Safe Spec" for a part, then the end users suffer the consequences, and some poor mechanic gets blamed when the bars slip on the first ride......
Signed: S. P. Mechanic, semi-retired.

I always follow the guideline of "grease if it's supposed to move, antiseize (or thread locker) it it's not supposed to move"

That's a lot of unnecessary, messy antiseize where grease would have worked just as well.

How is anti-sieze messier than grease? That is a new one, having built several titanium bikes for myself and some for other people I have never felt that anti-seize is any messier than grease. Essentially anti-seize is grease with copper or other metal flakes in it (yes I know it is more complex than that and the chemical makeup is probably different enough).

I will agree on the usage front. I only use it on titanium frames to prevent galling or if somehow my anti-seize is easier to grab than grease and I am just threading something in.

You seem uniquely immune to the way anti-seize, especially the typical Park stuff with graphite, stains clothes and skin. It also ruins grease if it gets out of the threads and into contact with the bearings.

I also use it to decrease galvanic problems with titanium, but I avoid using it anywhere it can be avoided because grease is completely effective and is easier to clean up when it migrates.

If you like using it, great. But like many things talked about on forums, the stuff went from a weird substance used in jet engines to a "necessity" for the assembly of our toy-like bicycles. It is overkill and sometimes creates problems that you won't see with grease.

I grease most threads. Blue Loctite rack, bottle cage, and rotor bolts, maybe a couple of others.

I've done anti-seize on dissimilar metal situations in the past but it's been at least 10 years, and I'd only do it again if someone asked me to on their bike.