greasing the tapers

pbiggs · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Asterix
No, not convinced. Why didn't they have warranty claims from customers who didn't grease the cranks, eh? And why didn't he ask them why cranks should not be greased?<hr height="1" noshade id="quote"></blockquote id="quote">Some of the warranty claims may have come from those who greased, some from those who didn't. Brandt's point is that only those who repeatedly tightened their cranks split them, whether they used grease or not. Grease is never the cause of the problem, in Brandt's opinion.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">But anyway, I don't have any trouble with ungreased cranks. I'm a heavy rider who tours in the hills, I give my cranks a hard time. Why I should I start greasing them?<hr height="1" noshade id="quote"></blockquote id="quote">Personally, I wouldn't suggest that anyone removes their cranks just to refit them with grease if they're having no problems, just that grease may help better fitting in the first place sometimes. The argument is more against those who say you must never use grease on cranks and that terrible things will happen if you do. That is not true. At worst it does nothing.

Ken Night · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by pbiggs

<hr height="1" noshade id="quote"></blockquote id="quote">

Big or little end?

"I once prayed to God for a bike, but quickly found out he didnt work that way...so I stole a bike and prayed for his forgiveness"

funkyrayman · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">The argument is more against those who say you must never use grease on cranks and that terrible things will happen if you do. That is not true. At worst it does nothing.
<hr height="1" noshade id="quote"></blockquote id="quote">

I think that is the key point of this whole topic....

pbiggs · June 2007

I dread to ask: big or little end of what? [:)]

If using grease at all, grease the whole area where the crank fits.

msb123 · June 2007

Which end do you start your boiled egg - big or little?

Fab Foodie · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by msb123

Which end do you start your boiled egg - big or little?
<hr height="1" noshade id="quote"></blockquote id="quote">
Err, Big.

The pessimists of this world are rarely disappointed....
Fab's TCR1

pbiggs · June 2007

Oh!! ...Depends on the shape of teh eggcup [;)]

hubgearfreak · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dave5n

From persi=onal experience, albeit a long time ago, I'd suggest you'd notice a loose square-taper crank well before it fell off.
<hr height="1" noshade id="quote"></blockquote id="quote">

yes you would, but his point is that the bolt could come out and be lost, and then after that, the crank start working loose.

it doesn't matter if it's 100 yards or 100 days later..the bolt is lost.

Thanks for the link PB. i was a greaser before, and now know i am right to be

as for a boiled egg. i eat them boiled solid, then eat them fully peeled. off the plate with a knife and fork. as you would a potato[:D]

Axel_Knutt · June 2007

With the bolt fully home (head against the end of the axle), the strain on the crank would only be about 10%. Since the elongation for wrought alloys can be up to 30%, it surprises me not at all the Brandt didn't succeed in breaking any cranks by overload alone.
The flaw in Brandt's argument is that it takes no account of metal fatigue. The fatigue life of the crank is dependent on how much of the material's total strength is already consumed by the static stress from the taper, and not just the dynamic load induced by pedalling. The further the crank is driven onto the taper, the shorter the fatigue life will be. Greasing the taper reduces the risk of a crank seizing, leaving it dry reduces the risk of crashing with a fatigue failure. You pay your money and you take your choice.

jonnywilkinson · June 2007

scratching head now! but am definitely gonna try a little grease before taking that bike out again. the creaking is way too annoying and it doesn't sound like it can do much harm.

FWIW - I don't eat eggs.

cheers all for this, i didn't think it was a point of much contention

Jonny
FGG #2545 & #2983

pbiggs · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Axel_Knutt
leaving it dry reduces the risk of crashing with a fatigue failure.<hr height="1" noshade id="quote"></blockquote id="quote">How many cases of that has there been? Cranks failing through faitigue at the bottom bracket end?

Surely it's rare for a crank to break at all, and when it does happen, it's usually in the middle or at the pedal end.

Axel_Knutt · June 2007

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by pbiggs

How many cases of that has there been? Cranks failing through faitigue at the bottom bracket end?

Surely it's rare for a crank to break at all, and when it does happen, it's usually in the middle or at the pedal end.
<hr height="1" noshade id="quote"></blockquote id="quote">

Well, the premise of Brandt's argument was that the manufacturers had had alot of warranty returns. Brandt himself acknowledges the failures can't have been through overload alone, so that just leaves fatigue. Seizing and fatigue are both rare, but fatigue fractures are more painful, speaking from experience of one at the pedal end after grounding it on a corner. There's no reason for the crank to break in the middle, it's not a high stress point. Unless you reduce the torque accordingly, greasing the taper roughly doubles the static stress on the crank, assuming there's enough travel for it not to bottom out. To calculate how much that reduces the fatigue life, you would need to know the alloy used.

http://www.roymech.co.uk/Useful_Tables/Fatigue/Stress_levels.html

pbiggs · June 2007

Torque should be reduced when using grease.

Cranks broken in the middle:

http://pardo.net/bike/pic/fail-009/ccf9.jpg

http://materials.open.ac.uk/mem/images/ ... ccf10r.jpg

Axel_Knutt · June 2007

If they've broken in the middle, it's hard to see any explanation other than a flaw in the material.

davem399 · June 2007

I had a similar creaking problem a couple of years ago, which was slowly driving me nuts. I checked the cranks, pedals, eventually renewed the bottom bracket, all to no avail. To cut a long story short, the problem was a slightly slack bolt on the saddle clamp (the one holding the saddle to the seat post).

I was convinced the noise was coming from the chainset area, and not from under my ar$e!!

Dave

jhinds · June 2007

I had a similar 'out of the saddle' creak once which I was convinced had its source in the bottom bracket area. Turned out in the end to be the lower head set bearing housing loose in the head tube, fixed with a little araldite. On the subject of tapers, nobody has mentioned that JIS ( Shimano et al ) a subtely different from ISO ( Campag and others )so some combinations rely on more plastic deformation than others although all seem to work in my experience ( without grease ).

JohnH

jhinds · June 2007

I had a similar 'out of the saddle' creak once which I was convinced had its source in the bottom bracket area. Turned out in the end to be the lower head set bearing housing loose in the head tube, fixed with a little araldite. On the subject of tapers, nobody has mentioned that JIS ( Shimano et al ) a subtely different from ISO ( Campag and others )so some combinations rely on more plastic deformation than others although all seem to work in my experience ( without grease ).

JohnH

TomBombadil · June 2007

Re:creak

Also having creak because of saddle slipping. Using the Use Sumo saddle post - the clamp is quite dissapointing!

http://www.use1.com/products/rigid_seat ... m_sumo.php

No matter how hard I tighten the saddle bolt the saddle slips back (I like it forward). And yep it creaks and sounds like it's from the bottom bracket.

The post looks nice and feels good but so far is a pain having to keep pushing the saddle back and reclampming - Ihave thought about using locktite or soemthing like that - any opinions?

Tom

greasing the tapers

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