Shocking Pictures - Don't Open!

Does anyone have a LH crank arm in 172.5mm?

:(

ahhhh!!!

Oucheroo.

Out of interest, do you grease your BB spindle tapers before installing the cranks? I've read a bunch of different opinions - some say you should, others say if you do this happens. What did you do in this case?

I am not a mechanic but as far as i know there are only a very few things you should never ever grease:

1) BB spindle tapers
2) when pressing headset cups
3) saddle rails / stem clamp

who would grease saddle rails?!?!?!

jesus what did you do to that

Roberto I am not a mechanic but as far as i know there are only a very few things you should never ever grease:

1) BB spindle tapers
2) when pressing headset cups
3) saddle rails / stem clamp

I always grease my spindle tapers.

Never had a problem as yet.

i may have something... i remember seeing 172.5 written on something. It may have been a right crank arm though. No idea how i have ended up with loads of non matching arms.

Also roberto... Do you know of anywhere i can get a french bottom bracket for my lejeune frame. The one it came with is starting to pit itself.

Cheers

my freind phil wood makes french bbs

I also grease my spindle tapers. I had a horribly boring afternoon with a certain mr T. furgurson getting his off not to.

French BBs. Ha, seek and ye shall find.

Phil is a flashy expensive kinda guy.
I was thinking more along the lines of a NOS stronglight

yeah phil is not cheap to hang with, but he will treat you well.

smallbrownbike Phil is a flashy expensive kinda guy.
I was thinking more along the lines of a NOS stronglight

....... :)

Yeah, i think they angle-ground that too ;)

Wheels is right.

I always grease my spindle tapers.

Spindle greasin' from SheldonBrown.com

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

A: 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.

[size=20]So grease them tapers ![size] or Sheldon will come back to haunt your ass.

Roberto I am not a mechanic but as far as i know there are only a very few things you should never ever grease:

1) BB spindle tapers
2) when pressing headset cups
3) saddle rails / stem clamp

And I do the exact opposite. (except the stem clamp)

1) BB spindle tapers - to create a seal between aluminum and steel and to insure they go on all the way, just know how much to tighten as to not overtighten.
2) when pressing headset cups - again sometimes it due to aluminum and steel contact and to form a barrier against rust or corrosion.
3) saddle rails - many annoying creaks have been solved this way.

i've always been told to grease anything where aluminum or ti touches steel to prevent natural welding.

About to press some ally bearing cups into a steel frame today, what is the logic to not lube? After years of old crusty motorcycles I've learned to always lube or copperslip (antisieze) any metal to metal contact unless a manufacturer specifically says not to.
Anyone?

according to Zinn & The Art Of Road Bike Maintenance you should grease the headset, and the stem.

Bad luck, Roberto :0(

trampsparadise [quote]Roberto I am not a mechanic but as far as i know there are only a very few things you should never ever grease:

1) BB spindle tapers
2) when pressing headset cups
3) saddle rails / stem clamp

And I do the exact opposite. (except the stem clamp)

1) BB spindle tapers - to create a seal between aluminum and steel and to insure they go on all the way, just know how much to tighten as to not overtighten.
2) when pressing headset cups - again sometimes it due to aluminum and steel contact and to form a barrier against rust or corrosion.
3) saddle rails - many annoying creaks have been solved this way.[/quote]

Me too and for all the same reasons. Pretty much the only thing I wouldn't grease on a bike is the tyres and the handlebars. Any metal to metal contact is gonna be fine with a bit of grease and it stops things seizing.

BTW Rob - great thread title which has done nothing to put people off

If it was a splined axle I'd definitely grease it, if a square taper, i'd be inclined to put some on too

"Q: My cranks get loose, quite quickly too; over about 10 miles or so from being solid to flopping about in the breeze. Any suggestions?
A: One or both of the cranks are ruined!"

shit, my lh crank does that. it fell off on my the way home last night. :-(

oo look, my first post. hello.