Crankset Question

I have a touring/commuting bike that I really love. I'm running an Shimano Deore crankset on it. The
chainrings on it are about wasted, and the crank itself is really starting to show it's age. I'm
going to put a newer crank on the bike. It currently has a 122.5mm square taper bottom bracket. I've
always noticed a fair amount of "flex" or "give" in crank/BB . I'm looking into replacing it with a
newer XTR crankset and BB that uses the pipe billet spindle and the hollow tech arms. Have any of
you that have made this change notice that it is significantly "stiffer"? Is this type of setup
worth the additional cost over a traditional square taper design?

TIA

 

> I have a touring/commuting bike that I really love. I'm running an
Shimano
> Deore crankset on it. The chainrings on it are about wasted, and the
crank
> itself is really starting to show it's age. I'm going to put a newer
crank
> on the bike. It currently has a 122.5mm square taper bottom bracket. I've always
noticed
> a fair amount of "flex" or "give" in crank/BB . I'm looking into
replacing
> it with a newer XTR crankset and BB that uses the pipe billet spindle and the hollow tech arms.
> Have any of you that have made this change notice that it is significantly "stiffer"? Is this type
> of setup worth the additional cost over a traditional square taper design?

I've switched from "square" XT to splined LX. For me LX is way stiffer (I simply "feel" it, and
during hard pedaling with chain on largest chainring there's no rub against the front derailleur). I
think that XTR won't be significantly stiffer than LX (both are hollowtech and splined).

--
Melon - grandmaster of sweat, pain and suffering himself.

 

"melon" <[email protected]> wrote in message news:[email protected]... I think that
XTR won't be
| significantly stiffer than LX (both are hollowtech and splined).
|

I'm looking at one of the 5-arm cranksets with a 48 tooth sprocket. There is no option like that in
LX or XT. This crank I'm looking at is NOS with the splined BB.

 

On Thu, 6 Feb 2003 20:05:10 -0700, "I C S" <Fachausschuß@Saarbrucken.net.de> wrote:

>I have a touring/commuting bike that I really love. I'm running an Shimano Deore crankset on it.
>The chainrings on it are about wasted, and the crank itself is really starting to show it's age.
>I'm going to put a newer crank on the bike. It currently has a 122.5mm square taper bottom bracket.
>I've always noticed a fair amount of "flex" or "give" in crank/BB . I'm looking into replacing it
>with a newer XTR crankset and BB that uses the pipe billet spindle and the hollow tech arms. Have
>any of you that have made this change notice that it is significantly "stiffer"? Is this type of
>setup worth the additional cost over a traditional square taper design?
>
>TIA
>
>
My XT XTR combo it the most annoyingly noisy combo I've ever used.. and I really don't trust (over
the long term) the way the rings/spider attach to the crank arms.

And yes it is the cranks/spider making the noise..

 

I have a hard time believing people can really "feel" the flex in modern cranks. With all the
flexing going on in your tires, bars and stem it seems unlikely the crank bends enough to be felt my
human nervous systems. My other hobby is audio and it is truly amazing what people are convinced
they hear. Bricks on amps, frozen cables, green ink on CDs, the list goes on. I think the major
reason for the shift to splined cranks, other than just having something new to hype (and tying you
into buying the manufacturers BB), is that they are cheaper to make. Square holes are more difficult
to make with the tighter tolerances needed. But, I guess that's all we are going to have when Campy
finally makes the switch.

Tim

>
> I've switched from "square" XT to splined LX. For me LX is way stiffer (I simply "feel" it, and
> during hard pedaling with chain on largest chainring there's no rub against the front derailleur).
> I think that XTR won't be significantly stiffer than LX (both are hollowtech and splined).
>
> --
> Melon - grandmaster of sweat, pain and suffering himself.

 

> I have a hard time believing people can really "feel" the flex in modern cranks. With all the
> flexing going on in your tires, bars and stem it
seems
> unlikely the crank bends enough to be felt my human nervous systems. My other hobby is audio and
> it is truly amazing what people are convinced
they
> hear. Bricks on amps, frozen cables, green ink on CDs, the list goes on.
I
> think the major reason for the shift to splined cranks, other than just having something new to
> hype (and tying you into buying the manufacturers BB), is that they are cheaper to make. Square
> holes are more difficult to make with the tighter tolerances needed. But, I guess that's all we
> are going to have when Campy finally makes the switch.

Believe me or not, I didn't supsect LX splined to be stiffer than XT square, I even didn't think
about it that way. I simply had to replace the crankarms due to chainring wear (LX is cheaper than a
set of new fairly good chainrings), and after doing that I was amazed ("WOW! it's amazing" - like in
the stupido TV ads ) how noticable the difference is. I'm not saying that it improves performance
(except that chain doesn't rub anymore (same chainring size, same front derailleur)); what I am
saying, is that my new setup feels stiffer thus better. Another factor to consider is that I'm about
200 lbs heavy and have pretty strong legs.

--
Melon - grandmaster of sweat, pain and suffering himself.

 

> I'm looking at one of the 5-arm cranksets with a 48 tooth sprocket. There is no option like that
> in LX or XT. This crank I'm looking at is NOS with the splined BB.

IMHO, when it comes to "splined" cranksets capable of running 48 tooth chainring, either choice
won't be worse than squared Deores (assuming we aren't looking at egzotic lightweights). I've poped
up with the splined LX idea, because for me XTRs doesn't give too many "bangs for a buck".

--
Melon - grandmaster of sweat, pain and suffering himself.

 

"Tim McTeague" <[email protected]> wrote in message news:[email protected]...
| I have a hard time believing people can really "feel" the flex in modern cranks. With all the
| flexing going on in your tires, bars and stem it
seems
| unlikely the crank bends enough to be felt my human nervous systems. My other hobby is audio and
| it is truly amazing what people are convinced
they
| hear. Bricks on amps, frozen cables, green ink on CDs, the list goes on.
I
| think the major reason for the shift to splined cranks, other than just having something new to
| hype (and tying you into buying the manufacturers BB), is that they are cheaper to make. Square
| holes are more difficult to make with the tighter tolerances needed. But, I guess that's all we
| are going to have when Campy finally makes the switch.
|
| Tim

And that's what I came here for.... to get opinions on whether of not this is all worth it. I am
leaning against getting the splined crank.

 

Tim McTeague writes:

> I have a hard time believing people can really "feel" the flex in modern cranks. With all the
> flexing going on in your tires, bars and stem it seems unlikely the crank bends enough to be felt
> my human nervous systems. My other hobby is audio and it is truly amazing what people are
> convinced they hear. Bricks on amps, frozen cables, green ink on CD's
, the list goes on.

I think you are correct with that assessment but it isn't why ISIS spline standard was introduced.
There are a sizable number of failures, in cranks, spindles failures, and bearing pitting from the
overload causes by such a small diameter shaft. Just because people who own bicycles for occasional
outings have no failures does not mean there are none. Proof of this is the controversial
instruction of mounting cranks with no lubricant on the square shaft. This is a mistaken notion
brought on by crank failures due to the high loads at this interface and of course ill advised
tightening of the retaining bolt.

> I think the major reason for the shift to splined cranks, other than just having something new to
> hype (and tying you into buying the manufacturers BB), is that they are cheaper to make. Square
> holes are more difficult to make with the tighter tolerances needed. But, I guess that's all we
> are going to have when Campy finally makes the switch.

The main impetus behind this is the same as Shimano's splined hollow crank spindles. There is a
reliability problem regardless of conjecture about motivations for change. The crank spindle is a
great leap better today than with steel cranks and cotters of old, but it is not reliable to the
degree that there are no liability claims for failures.

>> I've switched from "square" XT to splined LX. For me LX is way stiffer (I simply "feel" it, and
>> during hard pedaling with chain on largest chainring there's no rub against the front
>> derailleur). I think that XTR won't be significantly stiffer than LX (both are hollowtech and
>> splined).

The larger diameter of Shimano splined crank spindles greatly reduces stress and especially bending
from the outboard load from the pedal. I doubt that a rider can feel this but, as you say,
chainwheel lateral deflection is a good measure of spindle flex and spindle bearing clearance, both
of which are magnified at the rim of the chainwheel.

>> Melon - grandmaster of sweat, pain and suffering himself.

What does this have to do with square or splined crank attachment, or are you one of those who rides
bike to get self awarded merit badges for suffering. I think of these folks when I see them walking
around with "I survived the Death Ride" shirts. Look at me, I'm tough. I grimace a lot on bicycle
rides to look like Lance Armstrong in his publicity photos.

Jobst Brandt [email protected] Palo Alto CA

 

> >> Melon - grandmaster of sweat, pain and suffering himself.

> What does this have to do with square or splined crank attachment, or are you one of those who
> rides bike to get self awarded merit badges for suffering. I think of these folks when I see them
> walking around with "I survived the Death Ride" shirts. Look at me, I'm tough. I grimace a lot on
> bicycle rides to look like Lance Armstrong in his publicity photos.

You shouldn't be so sure about somebody's signature ;-). My attitude to riding and the way I do it
sometimes make my friends smiling. This sig explains some reasons of their smiles. And you can be
sure that I'm not deadly serious about it ;-)

Back to topic: German Mountain Bike performed a stiffnes test of crankarms and BBs setups (load
applied to pedals' spindles, measured value: deflection of the crankarm) Deore crankset coupled with
square spindle: ~80 N/mm LX with Shimano splined spindle: ~100 N/mm

Doesn't matter whether I can feel that or not - LX is 25% stiffer (as stiff as XT, and stiffer than
pre-2003 XTR by 10 N/mm !). I think that it's enough to stop my chain rubbing, and make 55$ crankset
worth attention.

--
Melon - grandmaster of sweat, pain and suffering himself.

 

> Back to topic: German Mountain Bike performed a stiffnes test of crankarms and BBs setups (load
> applied to pedals' spindles, measured value: deflection of the crankarm) Deore crankset coupled
> with square spindle: ~80 N/mm LX with Shimano splined spindle: ~100 N/mm
>
> Doesn't matter whether I can feel that or not - LX is 25% stiffer (as
stiff
> as XT, and stiffer than pre-2003 XTR by 10 N/mm !). I think that it's
enough
> to stop my chain rubbing, and make 55$ crankset worth attention.
>

How does crank stiffness, real or imagined, have anything to do with chain rub?

 

On Sat, 08 Feb 2003 22:34:47 -0500, jobst.brandt wrote:

> Proof of this is the controversial instruction of mounting cranks with no lubricant on the square
> shaft. This is a mistaken notion brought on by crank failures due to the high loads at this
> interface and of course ill advised tightening of the retaining bolt.

I am amazed that this poor advice is still being promoted by the industry. I recently found a pair
of Cook Brothers cranks, and just for fun checked them out on the net. They not only advised
attaching the cranks dry, but also said to periodically re-torque the bolts.

Now, in one sense this is understandable, since they sell more that way. But it didn't seem to work.
Their site is out of date (three years), and possibly they are out of businesss..

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems. _`\(,_ | -- Paul Erdos
(_)/ (_) |

 

> How does crank stiffness, real or imagined, have anything to do with chain rub?

Reason (causing that chain (when on the largest chainring) rubs against front derailleur's plate) I
can think of: Force applied to right pedal can be decomposed on two vectors: tangent (rotates the
crank), normal (compresses or expands crankarm). Force is not applied in geometrical plane of the
crankarm, so both vectors give moments. Tangent gives twisting moment, and normal gives bending
moment (bends crankarm "inboard" or "outboard"). Both moments can deflect the chainring. When under
load, crankset is supported in two "points": BB's spindle, chain. Load is applied at the pedal's
spindle. All of these points are in different planes and axis, so we've got at least one moment of a
force causing crankarm and chainring deflections.

--
Melon - grandmaster of sweat, pain and suffering himself.

 

> > How does crank stiffness, real or imagined, have anything to do with
chain
> > rub?
>
> Reason (causing that chain (when on the largest chainring) rubs against front derailleur's plate)
> I can think of: Force applied to right pedal can be decomposed on two vectors: tangent (rotates
> the crank), normal (compresses or expands crankarm). Force is not applied in geometrical plane of
> the crankarm, so both vectors give
moments.
> Tangent gives twisting moment, and normal gives bending moment (bends crankarm "inboard" or
> "outboard"). Both moments can deflect the chainring. When under load, crankset is supported in two
> "points": BB's spindle,
chain.
> Load is applied at the pedal's spindle. All of these points are in
different
> planes and axis, so we've got at least one moment of a force causing crankarm and chainring
> deflections.

Try this on for size as a more likely cause. Bad front derailleur adjustment.

 

> Try this on for size as a more likely cause. Bad front derailleur adjustment.

I've already tried, but had to sacrifice shifitng performance. We're discussing rubbing as an
indicator of stiffnes, not as the problem

--
Melon - grandmaster of sweat, pain and suffering himself.

 

Robert Strickland writes:

> How does crank stiffness, real or imagined, have anything to do with chain rub?

The plane of the chainwheel(s) is governed by the right crank and crank spindle. Flex in either of
these in response to the overhung load from the pedal force will alter the plane of the chainwheels
and can cause the chain to drag.

Jobst Brandt [email protected] Palo Alto CA