Square taper, grease or not!!!!

[We_are_Stevo]

Still no proper reasons from the NO brigade
Putting a bit of grease helps it it slide on fully and to more importantly slide off again
Grease DOES NOT soften alloy so the axle pushes further into the crank damaging it,as has been suggested a couple of posts back That comes from people thinking they know what theyre about and use the biggest spanner they have and keep turning it more and more forcing the taper of the axpl in deeper and deeper till the crank has been damaged
Then they blame the grease :roll:

TORQUE
This is what the bloody bolt is for. Take a torque meter and tighten the bolt. DO NOT OVER TIGHTEN

Read this in conjunction with the reproduction of the official Raceface recommendation and RadNomads textbook reply (which could equally have come from my Grandfather, also an aircraft engineer prior to and during WWII)...

...then perhaps the 'No' Brigade can give an equally rational and non-emotive explanation as to why not?

 

[Jussa]

As an Aircraft engineer/technician from 1988 - Present day, I have assembled many precision mechanical components from installed aircraft systems many with interference fit assembly also where high torque loadings are applied, a light coating of grease is always applied to prevent cold welding and seizing of components, we use numerous grades of grease all serving a purpose in the assembly process. Agreed military aircraft are subjected to all manner of conditions, but I've applied a similar regime with my bikes and touch wood I've never had an issue with damaged tapers, or any damage to components that have been lightly coated. But I will as a general rule of thumb when things are taken apart the surfaces are cleaned and if reassembled then fresh grease applied.

Just my input and my opinion, it's still a personal choice and not mandatory, unlinke when working on aircraft.

 

[sylus]

Absolutely

I treat my bikes like my women.... The bits that are going to be ridden the hardest and with the most force .... Always get a little but of lube

 

[gtRTSdh]

You wouldn't grease a morse (circular) taper on a machine tool.

Based on the above where the surface area of the taper provides all of the drive (the tang is only for removal uses).

Clearly a square taper is different because the shape transmits torque as well as the surface area.

Now in my opinion, you don't want to encourage movement between the two tapers as this will cause wear and eventually damage, hence with no grease the tapers should lock together better, which IMHO is what is actually wanted, who cares if you have to use more force with a crank puller to remove the cranks?


Anyway as many of you know, I hate sqtp with a passion and the obvious solution to all the discussion is to use a splined setup (but not isis that's sh1t), end of crank.

 

[mkaavin]

You wouldn't grease a morse (circular) taper on a machine tool.

Based on the above where the surface area of the taper provides all of the drive (the tang is only for removal uses).

Clearly a square taper is different because the shape transmits torque as well as the surface area.

Now in my opinion, you don't want to encourage movement between the two tapers as this will cause wear and eventually damage, hence with no grease the tapers should lock together better, which IMHO is what is actually wanted, who cares if you have to use more force with a crank puller to remove the cranks?

...and what you now wrote is of course the most rational explanation! Thank you.

....why others in here has to back up their arguments by stating long experience in the airline industry....??....well it only seems to be one agenda behind such rhetorics; and that is to discourage others, less educated, from providing a rational explanation based on their own practical experience. :?

A relevant argument should be enough.

As for me, I totally support gtRTSdh's argument. I too have never used grease and have both ridden, mounted and dismounted several cranks over the years with no problems at all.

I can also imagine that when grease is applied it will be easy to "push" the crank to far in on the axle. This could maybe be remedied (as suggested by another RB member earlier in the discussion) by using a torque tool, but I think few of us are using such tools even though we probably should.

So I stand by my vote: No grease! Simple as that.

 

[Woz]

Love this - a bit like the Schrader vs Presta debate - anyhow, let's mention too that not all cranks are made with equal hardness. For example, an STX-RC crank is a different animal than a Middleburn RS7. The early Shimano ones you can keep tightening up what seems to be forever and there is visible distortion on the surface. The Middleburn on the other hand simply gets to an abrupt point and you can't tighten no more; you simply feel that any more tightening is either going to strip the thread on the crank bolt or split the crank. This goes for a UN54 steel or UN72 Cro-Mo BB.

Not to use some form of lubricant to reduce friction of two metal parts in the process of assembly is gossip. There is no need to have a fancy torque wrench either for the decimal accuracy - just a 25 cm long allen key and don't use all of your force.

...PS: I'm now going to try Nutella and Philadelphia cheese and see what happens; will probably be able to market one with some re-labeling as the de-facto product to end the debate ;-)

 

[We_are_Stevo]

Well no actually, because the Nutella will stick to the bread but the Philadelphia will just slide off the spread and you'll end up with half of it in your lap!

Don't you know anything?

...and those of the 'No' Brigade who resort to petty 'playground' petulance would do well to remember that, as with raising ones voice, they have already lost the argument.

 

[highlandsflyer]

http://sheldonbrown.com/brandt/installing-cranks.html

"Subject: Installing Cranks
From: Jobst Brandt

My cranks get loose, quite quickly too; over about 10 miles or so from being solid to flopping about in the breeze. Any suggestions?

One or both of the cranks are ruined!* Once ridden in the "floppy" mode, the tapered square bore of the crank has been deformed and can no longer be secured on a spindle. Install and properly tighten new cranks on the spindle after greasing the tapered square ends of the spindle. Proper tightness should be achieved with a torque wrench or by a skilled hand.

The admonition not to grease the spindle finds life mainly in the bicycle trade. When I discussed the "dry assembly" rule with crank manufacturers, I discovered that they had warranty claims from customers who split cranks. However, cranks cannot be split by overtightening them. This can be proven by attemting to do so. An M8x1 bolt is not strong enough to split a major brand crank.

Failure from "over-tightening" is caused by repeated re-tightening of properly installed cranks. In use, an aluminum crank squirms on its taper and, because the retaining bolt prevents it from moving off the taper, it elbows itself away from the bolt and up the taper ever so slightly. The resulting loss of preload, after hard riding, can be detected by how easily the bolt can be turned.

Loss of crank bolt preload is greater on left than the right cranks, because left cranks transmit torque and bending simultaneously while right cranks transmit these forces separately. The left crank transmits driving torque through the spindle to the right crank and chainwheel while the right crank drives the chainwheel directly. Besides that, the right crank transmits torque to the spindle only when standing on both pedals. Doing this with the right foot forward (goofy footed) is the only time the spindle transmits reverse torque.

Mechanics, unaware of why crank bolts lose preload (and commensurate crank tightening), have re-tightened bolts until cranks split. No warnings against re-tightening properly installed cranks are evident although it is here where the warning should be directed rather than at lubrication.

Because friction plays no role in torque transmission, preload in the press fit must be great enough to prevent elastic separation between the crank and spindle under torque and bending. This means that no gap should open between crank and spindle facets under forceful pedaling. Crank bore failure occurs when the press fit is loose enough that a gap opens between spindle and crank. Torque is transmitted by both leading and trailing half of each facet, contact pressure increasing and decreasing respectively. In the event of lift-off, the entire force bears only on the leading edge of facets and causes plastic deformation, causing the bore takes on a "pin cushion" shape (loose crank syndrome). Subsequent tightening of the retaining screw cannot correct this because neither the retaining bolt nor crank are strong enough to re-establish the square bore.

The claim that a greased spindle will enlarge the bore of a crank and ultimately reduce chainwheel clearance is also specious, because the crank cannot operate in a plastic stress level that would soon split the crank in use. However, increased engagement depth (hole enlargement) may occur without lubricant, because installation friction could ream the hole.

With or without lubricant, in use, cranks will make metal-to-metal contact with the spindle, causing fretting erosion of the steel spindle for all but the lightest riders. Lubricating the spindle for assembly assures a predictable press fit for a given torque. Without lubrication the press is unknown and galling (aluminum transfer to the steel spindle) may occur during assembly. After substantial use, spindle facets may show rouge and erosion from aluminum oxide from the crank, showing that lubricant was displaced.

Crank "dust caps" have the additional duty to retain loose crank bolts. Because crank bolts lose preload in use, they can become loose enough to subsequently unscrew and fall out if there is no cap. If this occurs, loss of the screw will not be noticed until the crank comes off, after the screw is gone.

Jobst Brandt "

 

[We_are_Stevo]

...and it doesn't get much more conclusive than that

 

[gtRTSdh]

...and it doesn't get much more conclusive than that

Indeed, if the chap didn't put grease on his tapers they wouldn't come loose after 10 miles