Torque wrench needed to put on crank arms?
Christan P Neves
that I need to torque the bolts on when I put on the crank arms. Is it
possible to do this without a torque wrench without ruining the crank
arms? Should I put grease on the spindle tapers or not? Any advice on
successfully putting back my crank arms would be greatly appreciated.
Thank You All.
chri...@uhunix.uhcc.Hawaii.Edu
John Rivoire
writes:
Never grease the spindle tapers! Doing so causes the crank to go on too
far and could ruin it. This is also part of the reason for using a
torque wrench. You don't want to put the cranks on too tight either. If
you plan to do a lot of your own bike maintenance I'd highly recommend
you invest in a torque wrench. It does provide some piece of mind when
you are cranking some of those bolts and bottom bracket shells down.
lema...@paradise.caltech.edu
>I took my 3 piece cotterless crank apart to clean and lube it. I read
>that I need to torque the bolts on when I put on the crank arms. Is it
>possible to do this without a torque wrench without ruining the crank
>arms? Should I put grease on the spindle tapers or not? Any advice on
>successfully putting back my crank arms would be greatly appreciated.
>Thank You All.
>
>chri...@uhunix.uhcc.Hawaii.Edu
>
Well, when they say "torque" I think all they mean is "turn the bolts
in 'til they're good and tight." You certainly don't need a torque
wrench for this job, unless you're hopelessly brutish. You're threading
a steel bolt into a steel spindle, so the fear of stripping anything
is quite small. I'd only be concerned when threading a steel bolt
into an aluminum part. But then you still don't need a torque wrench,
you just need to proceed with care. Grease everything, I say. Grease
the bolt and the spindle, this will make disassembly easier next time.
You never need a torque wrench for anything unless it's a very sensitive
application _and_ you know what the recommended torque numbers are.
Even if you used a torque wrench for you cranks, you wouldn't know what
to set it to anyways.
--Paul L.
Jason Harrison
>Never grease the spindle tapers! Doing so causes the crank to go on too
>far and could ruin it. This is also part of the reason for using a
>torque wrench. You don't want to put the cranks on too tight either. If
>you plan to do a lot of your own bike maintenance I'd highly recommend
>you invest in a torque wrench. It does provide some piece of mind when
>you are cranking some of those bolts and bottom bracket shells down.
John,
Please explain how grease on the spindle tapers could cause the crank
to go on too far. I fail to see how a small loss of friction between
the crank and the spindle could cause the crank to be pushed onto the
spindle far enough that the crank would crack. This is not a friction
fit, but a wedge-fit. As the crank is pushed on to the spindle the
stresses between the crank and spindle increase. Grease cannot
decrease this force. Nor can grease make a square peg fit into a
round hole.
As has been stated before, taper fit parts have been used and well
understood for a long, long time. Just because it's on a bike doesn't
mean that the laws of physics suddenly change. Similiarily, lock nuts
CAN BE greased, and won't spontaneously loosen if greased. Grease
doesn not make parts friction less, or undeformable.
Crank binder bolts should be tightened to 220-300 in-lbs. This is
about the limit most people can exert using a small wrench (6-8 in
long). Though I recently started using a torque wrench just to be
sure. When I feel more comfortable, then it will probably not be
required. YMMV.
Don't under torque the bolts or the crank can loosen up as you ride
and become worn. The preload on the crank keeps it from wearing
against the spindle as you ride.
If you properly torque the bolts, as you ride the crank will become
tighter on the spindle. Do not re-tighten the bolts or then you will
split the crank.
Is this in the FAQ? Can we put it there?
-Jason
--
-------------------------------------------------------------------------------
J. Harr...@cs.ubc.ca http://www.cs.ubc.ca/spider/harrison
Graduate Motto: Free-time with guilt. ftp://ftp.cs.ubc.ca/pub/local/quotes
--
-------------------------------------------------------------------------------
J. Harr...@cs.ubc.ca http://www.cs.ubc.ca/spider/harrison
Graduate Motto: Free-time with guilt. ftp://ftp.cs.ubc.ca/pub/local/quotes
Joshua_Putnam
>As has been stated before, taper fit parts have been used and well
>understood for a long, long time. Just because it's on a bike doesn't
>mean that the laws of physics suddenly change. Similiarily, lock nuts
>CAN BE greased, and won't spontaneously loosen if greased. Grease
>doesn not make parts friction less, or undeformable.
>If you properly torque the bolts, as you ride the crank will become
>tighter on the spindle. Do not re-tighten the bolts or then you will
>split the crank.
>Is this in the FAQ? Can we put it there?
I think it's been in the FAQ for many years, though I don't have
any really old FAQs sitting around to check. I'm sure it's been
there at least three or four years, a typically pithy writeup
from Jobst Brandt.
--
Jo...@WolfeNet.com is Joshua Putnam / P.O. Box 13220 / Burton, WA 98013
"My other bike is a car."
Bike parts for sale: finger Joshua...@WolfeNet.com for list.
Joshua_Putnam
>Well, when they say "torque" I think all they mean is "turn the bolts
>in 'til they're good and tight." You certainly don't need a torque
>wrench for this job, unless you're hopelessly brutish. You're threading
>a steel bolt into a steel spindle, so the fear of stripping anything
>is quite small.
The most important reason for using a torque wrench on crank
bolts is to make sure they're tight enough, not to avoid
over-tightening. There's no reason you absolutely have to use a
torque wrench, but there are an awful lot of people out there
with under-tightened crank bolts, leading to loose cranks that
wear on the spindle and will never again stay tight.
The specified torque varies by manufacturer, but is generally in
the range of 25-35 foot-lbs.
David Rayner
: I took my 3 piece cotterless crank apart to clean and lube it. I read
: that I need to torque the bolts on when I put on the crank arms. Is it
: possible to do this without a torque wrench without ruining the crank
Christan, I can think of five basic rules of bike technology:
(1) Never grease your bottom bracket spindle tapers. This is just
asking for trouble.
(2) Never hang your bike by the wheels. (Metal has a memory; your
rims will be irreparably damaged before you know it).
(3) Throw out your steel frame after 10000 miles. It will feel 'dead'.
The grain structure undergoes a metamorphosis, or something.
(4) The best single investment you can make is a radially spoked front
wheel. The aerodynamic advantage will allow you to spin at least two
gears higher, and take 10 minutes off your 40k.
(5) The second best investment is a subscription to _Bicycling_
magazine, a reliable source of sound advice and thoughtful cycling journalism.
Any others?
David Rayner
Mike Iglesias
Joshua_Putnam <Jo...@WolfeNET.com> wrote:
>I think it's been in the FAQ for many years, though I don't have
>any really old FAQs sitting around to check. I'm sure it's been
>there at least three or four years, a typically pithy writeup
>from Jobst Brandt.
It's in the FAQ, and as you said it's been there for some time. I guess
some people haven't bothered to read it yet.
The FAQ is available from:
ftp://draco.acs.uci.edu/pub/rec.bicycles/faq
http://draco.acs.uci.edu/rbfaq.html
--
Mike Iglesias Internet: igle...@draco.acs.uci.edu
University of California, Irvine phone: (714) 824-6926
Office of Academic Computing FAX: (714) 824-2069
Jobst Brandt
> Is this in the FAQ? Can we put it there?
This is in the FAQ but believers in myth and lore do not read the FAQ.
As I said, I believe I found from where the admonition to not grease
crank spindles arose. It seems to have come from split cranks that
occur as you described, from fastidious riders who regularly take up
slack in crank bolts after every ride. This is the surest way to
split cranks and has nothing to do with lubrication.
Jobst Brandt <jbr...@hpl.hp.com>
----------------------------------------------------------------------
The FAQ:
Subject: 8.11 Cracking/Breaking Cranks
From: Jobst Brandt <jbr...@hpl.hp.com>
Cranks break because they are aluminum and because they have high
stress at various points. The worst of these points are at the pedal
eye and where the spider fingers join the right crank. The pedal eye
is weak because the joint is incorrectly designed, but since it is a
standard and gives the appearance of working properly, it may never be
changed. This joint always moves and causes fretting corrosion and
cracks that propagate into the crank and cause failure. A better
joint here would be a 45 degree taper instead of a flat shoulder at
the end of the pedal thread.
The thin web between the spider and crank, another common crack origin
on cranks like the Campagnolo Record, was nicely redesigned in the
C-Record crank, but to make up for that the C-Record is otherwise
weaker than the Record version. My experience is that they break in
about 1500 miles because the pedal eye has a smaller cross section
than the Record model, but maybe the alloy is poorer too. I have
subsequently used Dura Ace cranks for more than two years with no
failure yet. I don't believe in eternal life here either.
Aluminum has no safe fatigue limit but just gets progressively safer
as stress is reduced. In contrast, steel has a threshold below which
failures cease. Therein lies some of the problem.
As for cranks loosening, one can view the junction between spindle and
crank in an exaggerated elastic model where the spindle is made of
plastic and the crank of Rubbermaid household rubber. The crank, once
properly installed and the retaining bolt in place, squirms on the
square taper when under torque. During these deformations the crank
can move only in one direction because the bolt prevents it from
coming off. The crank always slides farther up the taper. Proof that
the crank squirms is given by the fretting rouge always found on the
spindle, whether lubricated or not, when a crank is pulled off after
substantial use.
As was mentioned by various observers, the left crank bolt is usually
looser, after use, than the right one and this could be anticipated
because the two cranks differ in their loading. This does not mean
the left crank is looser. Actually it is tighter, only the bolt is
looser. The left crank is more heavily loaded because it experiences
offset twist from the pedal at the same time it transmits torque to
the spindle. The right crank, being connected to the chain,
experiences either spindle torque from the left pedal or twist from
the right pedal but not torque and twist at the same time.
In this squirming mode, cranks wander away from the retaining bolt and
leave it loose after the first hard workout (for riders of more than
150 lbs). The bolts should NOT be re-tightened because they were
correctly tight when installed. Cranks have been split in half from
repeated follow-up tightening, especially left cranks. The spindle
should be lubricated before installing cranks. A wipe of a mechanic's
finger is adequate since this is to prevent galling in the interface.
To prevent losing a loose crank bolt, the "dust" cover that is in fact
the lock cap should be installed.
Those who have had a crank spindle break, can attest to the greater
stress on the left side because this is the end that always breaks
from fatigue. A fatigue crack generally has a crystalline appearance
and usually takes enough time to develop that the face of the fracture
oxidizes so that only the final break is clean when inspected.
Because a notch acts to concentrate stress, the advancing crack
amplifies this effect and accelerates the advance once the crack has
initiated.
I have heard of instructions to not lubricate spindles before
installing cranks but I have never been able to find it in any
manufacturer's printed material. Although I have broken many
Campagnolo cranks, none has ever failed at the spindle. I am certain
that the standard machine practice of lubricating a taper fit has no
ill effects. I have also never had a crank come loose nor have I
re-tightened one once installed.
------------------------------
Timothy J. Lee
| Also, a torque wrench for bike parts really seems
|like overkill. A torque wrench is best used when you've got the
|manufactures recommended numbers, which you never have for bike
|parts anyways, so you have to just make up the numbers.
Shimano parts and Trek bicycles come with manuals that include torque
values in the installation or maintenance instructions.
--
------------------------------------------------------------------------
Timothy J. Lee tim...@netcom.com
No warranty of any kind is provided with this message.
Eric Swanson
>Christan, I can think of five basic rules of bike technology:
>
>(1) Never grease your bottom bracket spindle tapers. This is just
>asking for trouble.
>
>(2) Never hang your bike by the wheels. (Metal has a memory; your
>rims will be irreparably damaged before you know it).
>
>(3) Throw out your steel frame after 10000 miles. It will feel 'dead'.
>The grain structure undergoes a metamorphosis, or something.
>
>(4) The best single investment you can make is a radially spoked front
>wheel. The aerodynamic advantage will allow you to spin at least two
>gears higher, and take 10 minutes off your 40k.
>
>(5) The second best investment is a subscription to _Bicycling_
>magazine, a reliable source of sound advice and thoughtful cycling journalism.
>
>Any others?
ausing permanent deformation of the frame, fork, etc. (I picutre this as being a bit like the problem of inserting a whole body into=
hyperspace simultaneously -- if part of it goes through first, the rest may get left behind, cf rec.spaceships.tech for more info.)=
Eric
lema...@paradise.caltech.edu
>In <DFx60...@news.hawaii.edu> chri...@uhunix.its.Hawaii.Edu (Christan P Neves)
>writes:
>>
>>that I need to torque the bolts on when I put on the crank arms. Is it
>
>>possible to do this without a torque wrench without ruining the crank
>>arms? Should I put grease on the spindle tapers or not? Any advice on
>>successfully putting back my crank arms would be greatly appreciated.
>>
>>chri...@uhunix.uhcc.Hawaii.Edu
>>
>Never grease the spindle tapers! Doing so causes the crank to go on too
>far and could ruin it. This is also part of the reason for using a
>torque wrench. You don't want to put the cranks on too tight either. If
>you plan to do a lot of your own bike maintenance I'd highly recommend
>you invest in a torque wrench. It does provide some piece of mind when
>you are cranking some of those bolts and bottom bracket shells down.
>
I guess I beg to differ. I don't think greasing the tapers puts you
at risk of putting your cranks on too far (you'd really have to
be cranking away at the bolt to do that), but I do think it aids
disassembly later on. Also, a torque wrench for bike parts really seems
like overkill. A torque wrench is best used when you've got the
manufactures recommended numbers, which you never have for bike
parts anyways, so you have to just make up the numbers. Torque wrenches
make sense for things like how tight to sandwich in some gasket in a car,
or when you're using power tools where you don't have the feedback of
handtools. Save the money of a torque wrench and spend it on something
else.
My $.02,
Paul L.
Richard Wurdack
: Christan, I can think of five basic rules of bike technology:
[sage advice snipped]
: Any others?
Not a basic rule, but one I learned last week on a group ride:
Never use hydraulic brakes! When you go up hill, the fluid will drain to
the rear calipers and cause the pads to drag on your rims, increasing
your effort.
Richard.
Robert Horvatich
> I guess I beg to differ. I don't think greasing the tapers puts you
> at risk of putting your cranks on too far (you'd really have to
> be cranking away at the bolt to do that), but I do think it aids
> disassembly later on. Also, a torque wrench for bike parts really seems
> like overkill. A torque wrench is best used when you've got the
> manufactures recommended numbers, which you never have for bike
> parts anyways, so you have to just make up the numbers. Torque wrenches
> make sense for things like how tight to sandwich in some gasket in a car,
> or when you're using power tools where you don't have the feedback of
> handtools. Save the money of a torque wrench and spend it on something
> else.
If torque specs are not available, there are tables of recomended
torques for fastners dependent on fastner grade and size.
Rob
email: |"You can't take life too seriously,
rho...@tbd.ford.com | you don't get out alive." Bugs Bunny
Joshua_Putnam
><lema...@paradise.caltech.edu> writes:
>| Also, a torque wrench for bike parts really seems
>|like overkill. A torque wrench is best used when you've got the
>|manufactures recommended numbers, which you never have for bike
>|parts anyways, so you have to just make up the numbers.
>Shimano parts and Trek bicycles come with manuals that include torque
>values in the installation or maintenance instructions.
Also, if you buy a Park torque wrench it comes with a full page
of torque specifications for bicycle parts, from chainring bolts
to cable pinch bolts and idler wheel pullies. Some parts tend to
get overtightened, others undertightened. A torque wrench is
overkill if you're mechanically inclined, but could save you a
lot of grief if you aren't sure how much to tighten your
handlebar binder bolts.
Paul
uses allen bolts. Do you know where I can find an allen
head socket?
Mike Iglesias
Joshua_Putnam <Jo...@WolfeNET.com> wrote:
>Also, if you buy a Park torque wrench it comes with a full page
>of torque specifications for bicycle parts, from chainring bolts
>to cable pinch bolts and idler wheel pullies.
There's a list of common torque values from the Third Hand catalog
in the FAQ.
Michael Finger
>
>Any others?
You forgot the most important ones of all for trendy, hip mountain bikers!
6) CNC machining is the strongest way to work AL, but only if it's
annodized (Fill in name of latest cool color), but not annodized
(fill in name of lasts seasons cool color).
7) New model stuff is always better then last seasons stuff, but
only if it costs more.
Later'
Michael Finger
Stephen Tu
David Rayner <dra...@mercury.uah.ualberta.ca> wrote:
>Christan, I can think of five basic rules of bike technology:
>
>asking for trouble.
>
>(2) Never hang your bike by the wheels. (Metal has a memory; your
>rims will be irreparably damaged before you know it).
>
>(3) Throw out your steel frame after 10000 miles. It will feel 'dead'.
>The grain structure undergoes a metamorphosis, or something.
>
>(4) The best single investment you can make is a radially spoked front
>wheel. The aerodynamic advantage will allow you to spin at least two
>gears higher, and take 10 minutes off your 40k.
>
>(5) The second best investment is a subscription to _Bicycling_
>magazine, a reliable source of sound advice and thoughtful cycling journalism.
>Any others?
(6) Heavier riders don't roll down hills any faster than lighter riders,
since Gallileo proved that all objects fall at the same speed by dropping
rocks off the Tower of Pisa.
(7) Aluminum is inherently stiffer than steel.
(8) Use WD-40 for your chain, it's a great lubricant.
(9) It's CNC machined and anodized neon purple. A lot of thought must
have gone into the engineering of that part.
Stephen Tu
ste...@eskimo.com
Bruce Jackson
John Rivoire <bik...@ix.netcom.com> wrote:
> Never grease the spindle tapers! Doing so causes the crank to go on
> too far and could ruin it. This is also part of the reason for using
> a torque wrench. You don't want to put the cranks on too tight
> either. If you plan to do a lot of your own bike maintenance I'd
> highly recommend you invest in a torque wrench. It does provide some
> piece of mind when you are cranking some of those bolts and bottom
> bracket shells down.
I admit that all the years I spent working in bike shops I never
greased spindles with the rare exception of when it was the only
way to eliminate a creak. The manufacturers of cranks do not
(as far as I know) recommend greasing the tapers but many folks
do without problem so the caution seems unfounded.
As far as avoiding overtightening goes, I find that the wrenches
designed for tightening crank arms are short enough and uncomfortable
enough that it is unlikely that folks will overthighten. With a
fairly thin 6"-7" wrench it hurts your hand before you can tighten the
crank to the point where it is damaged. Someone using a socket wrench
(especially with a breaker bar) could over do it though.
--
Bruce Jackson | P. O. Box 13886-NT | GAB 550E
UNIX Systems Admin. | Denton TX 76203-3886 | (817)565-2279
Computer Sciences | jac...@cs.unt.edu | FAX (817)565-2799
Univ. of North Texas | http://replicant.csci.unt.edu/~jackson/
ELPHLS
torque, but how about those of us who use allen key crank bolts? Of
which there are many.
Robert Horvatich
> You never need a torque wrench for anything unless it's a very sensitive
> application _and_ you know what the recommended torque numbers are.
> Even if you used a torque wrench for you cranks, you wouldn't know what
> to set it to anyways.
It just so happens that people can have the proper equipment and the
knowledge to use it.
David Rayner
: I have a torque wrench, but the crank on both of my bike
: uses allen bolts. Do you know where I can find an allen
: head socket?
Easy. Many good hardware stores will have hex wrench sockets to fit a
1/4" or 3/8" drive handle. I got mine from Sears (Craftsman); set of
six going from 4 through 10mm, cost about CDN$20. (This is really more
than I need; I only use the 5 and 6mm with any frequency so I could have
just bought those two singly).
If you can't find them locally, order from Third Hand. They have a
series of them for three or four bucks each.
A warning: if you put hex wrench sockets on an ordinary ratchet handle,
and if you are a hamfisted sort of guy like me, you will have a weapon
which overtightens (and decapitates) bolts with great ease. I've
ripped the heads off a couple of seatpost binders this way.
Bike techie nirvana is (i) a set of Bondhus balldrivers (the ones with
the sexy red handles) and (ii) a set of sockets-- both in 4, 5, and 6mm hex.
David Rayner
lema...@paradise.caltech.edu
Yes, you're right of course. I may have been a bit hasty. However,
I will stand by the statement that torque wrenches are largely
unnecessary for bike work.
--Paul L.
Jobst Brandt
> I guess I beg to differ. I don't think greasing the tapers puts you
> at risk of putting your cranks on too far (you'd really have to
> be cranking away at the bolt to do that), but I do think it aids
> disassembly later on.
Once in use, the lubricant will be displaced from the interface by
fretting motions that, in time, cause rouge (Fe3 O4) to form in the
interface. Removal is just as difficult with or without applying
lubricant.
Jobst Brandt <jbr...@hpl.hp.com>
Jeff turbo Deifik
says use the Panaracer EASY PATCH kit to patch them. Supergo, as well
as other bike stores have not been able to get the Panaracer brand patch
kit, nor anything else designed for patching polyurethane tubes. One
mechanic said that Speed Patches might work. So how do I patch these tubes?
Jeff turbo Deifik
jde...@weasel.com
tu...@weasel.com
Alex D Rodriguez
Paul <pa...@techno.discordia.org> wrote:
>I have a torque wrench, but the crank on both of my bike
>uses allen bolts. Do you know where I can find an allen
>head socket?
>
Allen head sockets are pretty common. Most tool stores should have them.
Of course there is always Sears if there is no tool store near by.
-----------------
Alex __O '86 Dodge Omni GLH Turbo
_-\<,_ '87 Alfa Romeo Milano
(_)/ (_) '88 Vitus/Dura-Ace
Jobst Brandt
> Five basic rules of bike technology:
> (1) Never grease your bottom bracket spindle tapers. This is just
> asking for trouble.
> (2) Never hang your bike by the wheels. (Metal has a memory; your
> rims will be irreparably damaged before you know it).
> (3) Throw out your steel frame after 10000 miles. It will feel
> 'dead'. The grain structure undergoes a metamorphosis, or
> something.
> (4) The best single investment you can make is a radially spoked
> front wheel. The aerodynamic advantage will allow you to spin at
> least two gears higher, and take 10 minutes off your 40k.
> (5) The second best investment is a subscription to _Bicycling_
> magazine, a reliable source of sound advice and thoughtful cycling
> journalism.
Marvelous! This is a little shorter than the recently posted
excellent list of the important differences between Power Bars and dog
shit.
I can tell your list of rules could also grow, but would probably not
end as abruptly as the Power Bar list did, when an astute contributor
pointed out that ultimately, if you are in dire straights you could
(in contrast to a Power Bar) actually eat dog shit. That pretty well
ended the discussion
Jobst Brandt <jbr...@hpl.hp.com>
Derek Anderson
: I have some of these tubes. The instruction sheet that comes with them
I have had trouble getting patches as well. Speed patches will work
perfectly if you are using mountain tubes, but will come of due to the
higher pressure if you are using road tubes. I heard that vinyl car seat
patch will bond on a regular patch to a greenlite, but have never tried it.
- Derek
Ming Dong
: I have some of these tubes. The instruction sheet that comes with them
: says use the Panaracer EASY PATCH kit to patch them. Supergo, as well
: as other bike stores have not been able to get the Panaracer brand patch
: kit, nor anything else designed for patching polyurethane tubes. One
: mechanic said that Speed Patches might work. So how do I patch these tubes?
A Water Bed patch kit should will work perfectly.
Ming
Richard Kaiser
I learned to use torque wrenches when I worked on aircraft, and I still
use them on auto and bicycle repairs. Now, if only I could get used to the
lack of safety wire on all of those important bolt (safety wire is stainless
steel wire that is used to keep bolts from coming loose). If all else fails,
measuring the torque needed to break-loose a bolt will give a high figure for
the torque needed to tighten it. After using a torque wrench for quite a
while you develop a feel for the right torque -- when the torque just starts
to climb. Without a torque wrench most people overtighten bolds.
Richard
OWEN G EMRY
> You tell us approximately how to tell if we are tightening to the correct
> torque, but how about those of us who use allen key crank bolts? Of
> which there are many.
>
What difference could that possibly make? The torque should
be the same no matter what your bolts look like.
-oge
OWEN G EMRY
> I have a torque wrench, but the crank on both of my bike
> uses allen bolts. Do you know where I can find an allen
> head socket?
Have you tried a hardware store? I figured it was
a long shot, but that's where I found mine.
-Owen G. Emry
OWEN G EMRY
> I have a torque wrench, but the crank on both of my bike
> uses allen bolts. Do you know where I can find an allen
> head socket?
Hardware stores. Go figure. Not really a rare item.
-Owen G. Emry
Jobst Brandt
> I learned to use torque wrenches when I worked on aircraft, and I
> still use them on auto and bicycle repairs. Now, if only I could
> get used to the lack of safety wire on all of those important bolt
> (safety wire is stainless steel wire that is used to keep bolts from
> coming loose).
Bicycles are spared that because they have no vibrating motor that
dissipate energy throughout the frame. There isn't enough shake to
loosen anything on a bicycle but rattling fenders if you have them.
> If all else fails, measuring the torque needed to break-loose a bolt
> will give a high figure for the torque needed to tighten it.
I think you should qualify that a bit. The classic bolt that is a
candidate for a torque wrench on bicycles is the crank retaining
screw. This one in particular is nearly always substantially looser
than it was when tightened for the reasons explained in detail
previously.
(also see the FAQ on crank tightening)
> After using a torque wrench for quite a while you develop a feel for
> the right torque -- when the torque just starts to climb. Without a
> torque wrench most people overtighten bolts.
I don't know what you call overtighten, but my definition of that is
permanent damage to either the fastener or the parts it retains. I
don't believe that either of these occurs to the degree that you suggest.
Jobst Brandt <jbr...@hpl.hp.com>
Don Piven
Tim Smith <tss...@netcom.com> wrote:
>Only exceptionally well-equipped hardware stores, at least in my part
>of the world. What I've done is cut off an Allen key, then epoxy it
1>into an equivalent metric socket. Lasts a while. Braze it in for more
>durability.
Or you could just go to Sears and get their set of 3/8" drive metric
allen keys. Got one, works great with their torque wrench.
--
Don Piven d...@suba.com
Chicago IL piven...@nova.novanet.org
phyx...@zeus.kent.edu
>> the right torque -- when the torque just starts to climb. Without a
>> torque wrench most people overtighten bolts.
>
>I don't know what you call overtighten, but my definition of that is
>permanent damage to either the fastener or the parts it retains. I
>don't believe that either of these occurs to the degree that you suggest.
My experience is that most people overtighten aluminum and titanium bolts.
The fact that these types of bolts feel ``soft'' has something to do with
it, I think. This is made worse by the fact that many bikes will have
stainless bolts in one location, that the home mechanic will crank down
as hard as he can, then go to an aluminum bolt, and bam, strip that
sucker right out. Happens all the time.
Richard Kaiser
>Richard Kaiser writes:
>
>> get used to the lack of safety wire on all of those important bolt
>Bicycles are spared that because they have no vibrating motor that
Opps, forgot the smiley face. I deleted a reference to safety/bailing wire as
being too obscure.
>
>> If all else fails, measuring the torque needed to break-loose a bolt
>> will give a high figure for the torque needed to tighten it.
On rethought, loosten the bolt and then measure the torque to retighten to the
same position. Though finger tight plus 1/6 to 1/4 turn does work for most
bolts on a bicycle.
>I think you should qualify that a bit. The classic bolt that is a
>candidate for a torque wrench on bicycles is the crank retaining
>screw. This one in particular is nearly always substantially looser
>than it was when tightened for the reasons explained in detail
>previously.
>(also see the FAQ on crank tightening)
I actually considered the crank-arm bolt unusual as these are the only taper
fittings on the bicycle (and some bicycles do not have them). Without a
torque wrench most people overtighten bolts, but without a torque wrench on
crank bolt I know I would always under-tighten.
Also, I do not use any grease on my cranks per Campy's instructions that came
with my cranks (Athena). The BB has a hard black coating or treatment that
may take the place of lubrication to prevent galling (re: Jobst's posting on
crank assembly in FAQ). I agree with Jobst in the FAQ that if you do not have
a torque wrench to tighten crank arm bolts pay a bike shop to do it right.
Also, consider that a torque wrench is cheaper than new crank arms.
>> After using a torque wrench for quite a while you develop a feel for
>> the right torque -- when the torque just starts to climb. Without a
>> torque wrench most people overtighten bolts.
>
>I don't know what you call overtighten, but my definition of that is
>permanent damage to either the fastener or the parts it retains. I
>don't believe that either of these occurs to the degree that you suggest.
>
>Jobst Brandt <jbr...@hpl.hp.com>
Overtighten a bolt that is in tension and you are reducing the load that the
bolt can take before it fails. Most people are saved by design margins.
Plastic deformation will also reduce the torque on a bolt to a safe level if
the bolt does not thin too much. I consider over or under tightening as less
than the maximum strength available before failure.
It does not happen to experience mechanics, but new riders learning to do
their own repairs do break bolts (I know, I was one at one time). The
insidious thing about overtightening bolts is they stretch and become loose.
And then you retighten them even harder. And they stretch and become loose.
And then... If you are lucky they break in the shop, if you are unluck they
break a long way from home.
Richard Kaiser
rka...@primenet.com
Pasaden, CA
Jobst Brandt
> My experience is that most people overtighten aluminum and titanium bolts.
> The fact that these types of bolts feel ``soft'' has something to do with
> it, I think. This is made worse by the fact that many bikes will have
> stainless bolts in one location, that the home mechanic will crank down
> as hard as he can, then go to an aluminum bolt, and bam, strip that
> sucker right out. Happens all the time.
So what does that have to do with the price of tea in China? We're talking
about tightening crank bolts when installing cranks, not vanity screws.
Jobst Brandt <jbr...@hpl.hp.com>
Eyvind Ness
writes:
Actually, Phyxr has a point. One particular instance that might interest
you is that the '95 XTR cranks come with Ti crank fixing bolts.
I don't know for sure about Dura Ace cranks, but wouldn't be terribly
surprised if they used the same "vanity screws", too. And if my memory
serves me well, Jobst could very well be using "vanity cranks" himself,
and by implication, "vanity screws" on his own bikes. I find that
amusing, but expecting Jobst to violently refute my assumptions ;-)
And BTW: Yes, I use a liberal amount of grease and a torque wrench for
the crank fixing bolts (recommended torque: 307-395 in.lbs according to
the instructions that came with my Shimano XTR cranks).
Eyvind.
Kit Cheves
Jobst Brandt
> Also, I do not use any grease on my cranks per Campy's instructions
> that came with my cranks (Athena). The BB has a hard black coating
> or treatment that may take the place of lubrication to prevent
> galling (re: Jobst's posting on crank assembly in FAQ). I agree
> with Jobst in the FAQ that if you do not have a torque wrench to
> tighten crank arm bolts pay a bike shop to do it right. Also,
> consider that a torque wrench is cheaper than new crank arms.
I think you'll also note that I said that it is difficult to
overtighten a crank bolt because the bolt will break before any other
damage occurs. The crank certainly does not suffer, because it can
hardly be made too tight on initial tightening. The only reason you
might mention a new crank becoming damaged is that there is so much
talk of overtightening that people are fearful of getting them
adequately tight. I believe there are far more failures of cranks
from an insufficient press than from *dread* overtightening.
> Overtighten a bolt that is in tension and you are reducing the load
> that the bolt can take before it fails. Most people are saved by
> design margins. Plastic deformation will also reduce the torque on
> a bolt to a safe level if the bolt does not thin too much. I
> consider over or under tightening as less than the maximum strength
> available before failure.
Once the tension begins to reduce, you are beyond yield stress and the
bolt is breaking. The way you say that, it could reinforce the fear
of too tight bolts. This is an extremely rare problem that does a new
mechanic good to break some screws to develop a sense for how tight
important screws should feel.
> It does not happen to experienced mechanics, but new riders learning
> to do their own repairs do break bolts (I know, I was one at one
> time). The insidious thing about overtightening bolts is they
> stretch and become loose. And then you retighten them even harder.
> And they stretch and become loose. And then... If you are lucky
> they break in the shop, if you are unlucky they break a long way from
> home.
There you go again, fear mongering. Far more damage is caused by screws
that are too loose than ones that are too tight. This is especially true
for crank bolts. Just read the net for how many people have had loose
cranks that can no longer be made tight because their bores have been
banged out on a loose fit.
Jobst Brandt <jbr...@hpl.hp.com>
Eric P. Salathe, Jr.
wrench and wiggle-free). I notice the chain ring is rather close to the chain
stay (which was bent to accomodate hubs that are now obsolete), and observably
crooked (the chainring is definitly flat). So, what keeps the cranks from being
pressed or from creeping too far onto the spindle? What kees them straight?
These are 15-yr-old Campy cranks I have not succeeded in breaking, but perhaps
the bores are showing signs of age....
--
Eric P Salathe, Jr sal...@atmos.washington.edu
Seattle, Washington http://atmos.washington.edu/~salathe
Sheldon Brown
>...does a new mechanic good to break some screws to develop a sense for how
>tight important screws should feel...Far more damage is caused by screws
>that are too loose than ones that are too tight. This is especially true
>for crank bolts.
Truer words were never typed. Even more than crank bolts, consider the cable
anchor bolts used in brakes. They are skinny, and they often have holes drilled
through them, very easy to break.
If you have never broken one of these, you are not yet a good mechanic.
Your hands have to learn how it feels.
If you overtighten a cable anchor bolt, it breaks, you learn a valuable lesson,
and you have to buy a new bolt for a buck-and-a-half.
If you undertighten a brake anchor bolt, everything will seem hunky dory, the
brakes will work just fine in normal use, until that bus cuts you off--then
you will squeeze _extra hard_ on the brake lever, the cable will slip, and
your brake will fail just when you need it most!
Sheldon "Human Torque Wrench" Brown
Newtonville, Massachusetts
+-------------------------------------------------------+
| Disclaimer: |
| The above are the Official Views of the |
| Institution, and are not necessary my own. |
+-------------------------------------------------------+
Eyvind Ness
kch...@qualcomm.com (Kit Cheves) writes:
;; In article <EYVIND.95O...@bingen.hrp.no>, Eyvin...@Hrp.No wrote:
;;
;; > I don't know for sure about Dura Ace cranks, but wouldn't be terribly
;; > surprised if they used the same "vanity screws", too.
;;
;; My Dura Ace 7410 cranks came with steel fixing bolts.
I checked with the 1995 Shimano catalogue: And Yes, the Dura-Ace comes
with Ti crank fixing bolts, too! Yours must be an older model.
The last laugh is mine after all. NyahNyahNyah ;-)
Eyvind.
jim frost
>jbr...@hpl.hp.com (Jobst Brandt) wrote:
>>...does a new mechanic good to break some screws to develop a sense for how
>>tight important screws should feel...Far more damage is caused by screws
>>that are too loose than ones that are too tight. This is especially true
>>for crank bolts.
>If you have never broken one of these, you are not yet a good mechanic.
>Your hands have to learn how it feels.
>If you undertighten a brake anchor bolt, everything will seem hunky dory, the
>brakes will work just fine in normal use, until that bus cuts you off--then
>you will squeeze _extra hard_ on the brake lever, the cable will slip, and
>your brake will fail just when you need it most!
I've never broken one of these bolts, but one of my tests is to pull
the levers as hard as I possibly can after putting everything
together. If it's going to slip under use it'll slip then. It took a
few tuneups before I got used to how tight they have to be to avoid
slippage, but I never had to break the bolt....
On the other hand I wouldn't call myself a good mechanic, but not
because I haven't broken bolts. Rather it's because I'm reluctant to
tear down certain parts.
jim frost
ji...@world.std.com
--
http://world.std.com/~jimf