[Closed] To grease or not to grease a square taper bottom bracket axle?

Not. In fact, degrease first.

Yes, grease.

Edit: this'll be fun 😉

No grease. Just because people do it doesn't mean it's correct. Think stabilisers.

Nooooooo.

It's one of those things where if you ask a bike mechanic he'll probably say no. If you ask a proper engineer if you shouldn't grease a taper fit, he'll look at you as if you're insane.

Shimano taper bb do often come with grease already on the axle
But with middle burn arms I'd degrease them to keep things nice and creak free

Don't expect this thread to reach a firm conclusion

Don't expect this thread to reach a firm conclusion

I'm expecting it to be a 5-pager with added insults by 2pm.

Copper grease?

Cheers,
Jamie

Isn't about not forcing the crank too far onto the taper and knackering the crank?

A question for retrobike surely?

Loctite!

Just joking. A very thin layer of grease, and ignore all naysayers.

But as folks have said above - will be fun to watch this thread. Aw

Isn't about not forcing the crank too far onto the taper and knackering the crank?

That is the theory. I've never seen it happen, and talking to quite a few people about it it seems to be an apocryphal rumour dating from the early Cyclotourist cranks which tended to snap everywhere.

This is one of those subjects I file under "Cargo Cult Bike Mechanics" - along with things about the direction of pulling spokes on a wheel, using low speeds with a hole saw when mitering tubes, and always facing bottom bracket shells.

Basically stuff that's done because that's how it's always been done, not because anyone has actually thought about it.

I've always put a dab of grease on and haven't suffered any damage or cranks falling off.

I have had trouble getting ungreased cranks off though.

hmmm- might learn something here.
[awaits some proper maths/fea/ nice graphs etc]

I spoke to Cliff at Royce about this once he said de-grease, I followed his instructions and never had a problem.

I've always put a dab of grease on and haven't suffered any damage or cranks falling off. I have had trouble getting ungreased cranks off though.

Exactly as above. Had to cut a set of cranks off a bike recently so much prefer to grease. Might even try copper grease next time

[awaits some proper maths/fea/ nice graphs etc]

I did do some tests a long time ago - I'm now trying to remember where I filed it all 😉

The conclusion, I think, was that with good cranks and a good BB, it didn't matter in the slightest. With cheap cast cranks, greasing helped the crank bed onto the axle more consistently.

bencooper - you could have ended the thread there! But cleverly your conclusion allows this to run on.

Old deore hollowtech 1s - are they 'cheap cast' cranks?

yeeeeeeno

I tend to say no. based on regular (6-8 months) changes of BB's or chainrings.

however, this changes depending upon when you are.

early 90's, definite no. custom expensive lightweight cranks, cnc-ed to death + greased square taper often led to the crank travelling waay up the taper, either cracking the crank or just hitting the shoulder.

early 00's (or just before...), could probably do so. metal on metal contact needs some form of barrier really and materials and manufacturing was better, less prone to crank failures apart from cheap shyte.

now.... probably not, if you're running square taper you're likely to have a budget set of cranks, which has a higher chance of being cheap soft shyte..maybe.

it also depends on how and where you ride and how well you maintain your bike too, which is probably more critical.

Ah, flashbacks to rec.bicycles.tech circa 1990 🙂

[url= http://draco.nac.uci.edu/rbfaq/FAQ/8f.11.html ]rec.bicycles FAQ : installing cranks[/url]

(there is a ton of good info on those pages - I'd forgotten all about it!)

I grease, and always have (left school and went into mechanical engineering), Sheldon Brown greased, Jobst Brandt is also a greaser.

Grease +1 - based on instinct, not science (but I'm convinced by the link above).

I thought the rules were:

Splines = grease
No splines = no grease

I coppaslip. If greasing is going to cause the crank to 'slide'(ie stretch or crack) too far up the taper, then that crank richly deserves the death it finds IMO. I little lubrication to ensure peoper seating and reduce the chance of 'settling' looseness out on a ride. also had cranks bond themselves to bbs before. I imagine this wouldn't be an issue for someone who changes BB or chainrings every 6 months or so.

So maybe the question is: how long are the BB and crank going to stay together?

There's no correct answer. I go with the following because it makes sense to me.

- new cranks/bb - no grease because the mating surfaces should be flat and smooth and not need any lubrication to either reduce friction or prevent creaking

- used - grease to reduce friction and the risk of creaking once there are marks on the surfaces.

bencooper - Member
This is one of those subjects I file under "Cargo Cult Bike Mechanics" - along with things about the direction of pulling spokes on a wheel, using low speeds with a hole saw when mitering tubes, and always facing bottom bracket shells.

Basically stuff that's done because that's how it's always been done, not because anyone has actually thought about it.

We have a winner!

And coincidentally, my brother has the nickname "Grumpy Dave" on Tower FM in response to the texts he sends in to the morning show.

In this climate I grease everything that I wish to remove later.

In Oz I don't need to.

In the spirit compromise how about greasing the drive side and leaving the non-drive side ungreased? Surely that would make everybody happy....

or alternating per face on the taper in the "loves me, loves me not" format?

I'm with Yak and Mike P on this one. I was under the impression that the advice was to grease Octalink/ISIS as there was a physical stop on the axle, but not to grease square taper as there was a risk of forcing the crank too far up the taper and cracking it (similarly, and for the same reason, I was under the impression that you shouldn't just tighten up a lose square taper crank but pull it first then tighten to the correct torque).

If I don't grease my (quality) cranks, they have all sorts of settling in problems.

If I grease them, they are fit and forget (middleburn and white industries)

Copper slip, as its a alloy to steel or Ti inferface.

Now move on nothing to see here 😀

risk of forcing the crank too far up the taper and cracking it (similarly, and for the same reason, I was under the impression that you shouldn't just tighten up a lose square taper crank but pull it first then tighten to the correct torque).

Read the piece by Jobst Brandt as linked above by Gary and he will explain both these things.

Grease FTW.

Just so as you know, the correct way to do it, as they teach bike mechanics for Cytech 2, is NO GREASE.
It's not meant to move. It's meant to stay still. So you don't grease the taper.

It is , however, acceptable to apply a drop of LIGHT oil which will ease assembly but be squeezed out as the taper settles in.

Personally, I've NEVER EVER oiled or greased a taper and NEVER EVER had a problem fitting or removing cranks, probably because I know what I'm doing and have some decent tools though..... 😉

It's not meant to move. It's meant to stay still.

So you never grease threads on assembly either? They are not meant to move.

Yeah, grease ... but; and I dunno where I read the quote, but you only need as much grease as you'd "find on a mechanics finger" (this is clearly from a time before gloves / barrier creams) - which is to say, just a very thin moistening of grease on the faces.

I've always done this and had no negative experiences, including over a couple of seasons of trials riding, which meant frequent BB swaps.

In my experience, just that slither of grease has been fine - enough to facilitate straight-forward installation / extraction, and (but) nothing more.

Possibly just as controversially - I do the same thing when installing headset cups too. 😛

I've always greased them and I'm not a engineer or bike mechanic. Not split one yet.... watch this space. Lol

LOL Cytech.

"LOL Cytech" a shroppyshire+1

A skim of grease and 25 foot lbs if I remember correctly.

LOL Cytech.

Are you impugning the much-respected industry-wide qualifications system? 🙂