Square taper crank fitting queries

[Sergeant Pluck]

Hi all - a couple of specific queries, advice appreciated.

I'll shortly be fitting a new set of cranks - square taper. It is possible that, after a trial fit, I may need to remove the cranks, put a different BB in, and re-fit. So:

1. How far do cranks move along the taper when the crank bolts are torqued up? That is, during a trial fit, do I need to torque the crank bolts fully up? My reasoning is that, if possible, I'd like to avoid any unnecessary removal / refitting of the cranks. Or do I not need to worry about two or three on / offs including fully torqued bolts?

2. Sorry to have to bring this up again. My own view is that tapers and crank bolts should be greased. But my confidence in this has been reduced by Campag's instruction leaflets, which state emphatically that they should be not greased and furthermore that they should be degreased first. I'm inclined to follow Campag's instructions but metal-to-metal just feels wrong. Any advice?

[Zoidburg]

Grease them lightly.

Campag talk crap - they also live in a warm dry country were it does not piss it down 75% of the year.

With the correct crank and BB the crank should effectively bottom out on the top of the taper, so yes you need to tighten them all the way down.

Just don't use crap white lithium grease - it bonds ally and steel together with galvanic corrosion.

[TimO]

I'd agree with Zoidburg.  I've always lightly greased square tapers (and other types for that matter).  I've had ones which were obviously ungreased as supplied on bikes, and they were an absolute bugger to get off.  Ones which have been lightly greased are generally not too bad to release (with the proper tools).

Not fully tightening the bolts, and then using the bike, is likely to damage the tapers, which would be a bad thing.

[Sergeant Pluck]

I note that both times I've removed my cranks after fitting by decent bike shops they've been greased a touch. No problems in use or when it came to take them off.

I can't see that static fitting / torquing up fully / removing a couple of times could cause any wear to worry about. My thinking is that if the parts are all compatible and that one does not overtighten or re-tighten the bolts there is no reason why a couple of on / offs should do any harm.

[Biggsy]

1.  The cranks move a fair way up the taper (I couldn't tell you by how many mm now), but the crank around the hole is elastic and I don't think is normally damaged by full torque and use, apart from any insignificant minor scratches or indentations.

2.  I get fewer (in fact no) problems since I started greasing.  But you should be ok dry if everything is mint and clean and fully torqued.  The recommended torque range might not be appropriate if you are greasing, though.  I use less than the recommended max when greasing.

[Sergeant Pluck]

2.  I get fewer (in fact no) problems since I started greasing.  But you should be ok dry if everything is mint and clean and fully torqued.  The recommended torque range might not be appropriate if you are greasing, though.  I use less than the recommended max when greasing.

Interesting point. Can't recall who mentioned it (Crumbling Nick?) but I recall talk of grease allowing the crank to go further up the taper than intended. How much less torque do you use?

[Biggsy]

Campag's recommended torque is 32-38 Nm.  I go to about 36 with grease.  That might be too much in theory (?), but I like my cranks tight!

It would be interesting to get more opinions on this point.  If x Nm is recommended for dry, what should it be for greased?

[mattc]

Grease them lightly.

My father gave me a very specific defn of "lightly":
the tiniest smidge, and wipe most of it off with your finger.

I now assume that this gives anti-seizing properties without messing up the torque required. I haven't had any problems, but I've removed very few cranks, so not a good sample size.

(He also gave me a magic pot of sparkly grease, but I can't remember what's in it right now ... )

[Zoidburg]

Sparkly grease?

Thats copper slip.

Anti seize normaly for bottom bracket cups.

[mattc]

No, it's silvery ( as opposed to brown/gold or however you choose to describe copper slip!)

(I am only allowed to use it on BB axles - I think it may have come from Lothlorien.)

[rogerzilla]

TA say grease them.

Makes no difference how much you use, since any excess is scraped off by the close clearance.

Ideally, fit them to the recommended crankbolt torque, ride for 100 miles and then remove the bolts, clean all the threads and re-torque with threadlock.  Then never touch them again unless the BB needs replacing.

[Biggsy]

Even the thinnest smear of grease or oil will interfere with the torque, so if using any lube at all, it doesn't matter if you put a big dollop on.

I just use ordinary grease rather than anti-seize.  My cranks ain't going to seize.

Installing Cranks by Jobst Brandt

[Sergeant Pluck]

then remove the bolts, clean all the threads and re-torque with threadlock

What's your thinking there?

[Biggsy]

Grease on the bolts assists good tightening.  Threadlocker prevents loosening.  These two things are incompatible.  There's been no need for threadlocker with my crank bolts, though.

Actually, wet threadlocker assists tightening as well, and prevents corrosion as well if loads is used.  Crank bolts can loosen if the cranks squirm up the taper in normal use.  Use some threadlocker if you are concerned about this.

[inc]

Campag's recommended torque is 32-38 Nm.  I go to about 36 with grease.

Greasing threads and the taper will allow over tightening for the same torque as the thread and taper friction will be reduced, depending on what data you read by  between 30-40%. Unless otherwise specified by the manufacturer thread torque figures are for dry threads.

[Biggsy]

Thanks Inc.  So my cranks are tighter than they are supposed to be.  This does at least mean they won't be loosening by themselves!  Which I like!

[Sergeant Pluck]

I'm buggered if I can find where I read that the crank bolts are not to be greased  

I was more surprised by that than the well-known tapers debate. But I can see no sign of the source of that "info" - could have sworn it was in the manual.

On a slight tangent, I see in the manual that Campag are also very keen on BB shell drain holes.

[Biggsy]

http://www.campagnolo.com/repository/documenti/en/7225254_Crankset-07-05.pdf - pdf page 15 -

"NEVER lubricate the bolts before tightening them".

Take a pinch of salt with that.

[Steve Kish]

I grease the spindle, grease inside the crank taper and grease the bolts that go into the spindle.

Unfortunately a couple of the recumbent ladies on the last FNRttS may remember what happened to my L/H crank on the Longwick to Thame road .... so this can be overdone, I guess!

[Crumbling Nick]

I'm buggered if I can find where I read that the crank bolts are not to be greased  

I was more surprised by that than the well-known tapers debate. But I can see no sign of the source of that "info" - could have sworn it was in the manual.

I think this might be what you remembered. It took me a few/several searches to find...

My caution about the conventions is that there is a very big difference between manufacturing with new components and our world of maintenance where corrosion, wear, minor thread damage (or worse) are commonplace.

HTH.

[inc]

Judging by the number of threads on this forum about stuck cranks, BB, seat pins etc I think maintenance is non existent for a lot of bikes.

[mrcharly-YHT]

I don't grease my tapers (ooer).

I've never had a crank stuck on - but then a lot of my bike have been using old-school BBs, so got stripped down every few months.

The only crank I've had come loose was on a bike built in an lbs, and the tapers were greased.

[LittleWheelsandBig]

With the correct crank and BB the crank should effectively bottom out on the top of the taper, so yes you need to tighten them all the way down.

They shouldn't bottom out on the top of the taper.  That would cause damage to the crank, particularly under torque.  However, the bolts should be sufficiently torqued and the vast majority of the taper should engage with the crank.

[Biggsy]

I agree it shouldn't bottom out, and doesn't when using the recommended maximum torque.  It would give the wrong chainline or even clearance problems, even if no damage to the crank.  It's easily possible to apply an absurd amount of torque with a long wrench, so there is a limit to what is sensible.

If using just an ordinary short allen key though (which I do not advise), then yes you want to tighten as much as you can manage, and do then definitely lubricate both the taper and the bolt, and pray to your god, because you'll need all the help you can get.  (Lubrication makes it physically easier to tighten).

[Zoidburg]

With the correct crank and BB the crank should effectively bottom out on the top of the taper, so yes you need to tighten them all the way down.

They shouldn't bottom out on the top of the taper.  That would cause damage to the crank, particularly under torque.  However, the bolts should be sufficiently torqued and the vast majority of the taper should engage with the crank.

You can feel them bottom out.

That's with full engagement.

I did not say a single thing about wellying it up with foot long tommy bar as Biggsy mentioned - that will split the crank arm or strip a thread.

Take a crank bolt out, you can see the face of the taper flush against the crank bolt hole, if you could not see it you would have a crank that is not all the way home which will run lose and deform over time, this is why they warn against mixing shimano pattern and campy as the tapers are slighty out of proportion to one another, get it wrong and it's bottoms out without being properly engaged or the taper can be driven in until it splits the crank.

Using the right combo it's not a problem.