Claims about BB/Crank Stiffness (XT)

"Ian G Batten" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff. In
practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider?

ian

Well, stiffer is better. I don't know how much stiffer they are, or if it's worth worrying about
though. But if you can make it stiffer and you're upgrading anyway, it's better that way. If you
have an old-style and you're thinking of upgrading solely for this stiffer claim, I wouldn't bother.
Old-style BB's have been around for a long time and they don't, IMHO, seem to be lacking in
stiffness for most people. I'd be more worried about the pedal eyelet breaking.

Cheers,

Scott..

Ian-<< Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff. In
practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider? >><BR><BR>

The only place stiffness differences can actually be seen on crank arms and BB spindles is on a test
machine and these differences are small.

If anybody rides a bike with this crank or that and comments on how stiff it feels, or how flexible,
they are either feeling the frameset or the wheels or tires or something but they are not feeling
crankarms or steel BB spindles flex or not.

If they were the next thing they would be feeling is something breaking.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

On Tue, 27 Jan 2004 11:27:58 +0000 (UTC), Ian G Batten

may have said:

Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff. In
practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider?

Under competition-level hard pedalling, the stiffer cranks and BB are less susceptible to deflection
that can cause unwanted chain behavior. Yes, for riders capable of generating the kinds of force
that can deflect the chainwheels enough, it's an advantage that's probably worth the expense. For
the pleasure-rider or punter like me, it's probably not.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
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it's also possible that I'm busy.
Words processed in a facility that contains nuts.

On 27 Jan 2004 13:59:22 GMT, [email hidden] (Qui si parla

Campagnolo) may have said:

Ian-<< Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff.
In practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider? >><BR><BR>

The only place stiffness differences can actually be seen on crank arms and BB spindles is on a
test machine and these differences are small.

If anybody rides a bike with this crank or that and comments on how stiff it feels, or how
flexible, they are either feeling the frameset or the wheels or tires or something but they are not
feeling crankarms or steel BB spindles flex or not.

If they were the next thing they would be feeling is something breaking.

By comparison to high-end conventional stuff, that's probably an accurate assessment. By comparison
to low-end stuff under the strain of a 6'3" 220-lb rider standing to pedal hard, well, I've seen the
chainwheels deflect enough to cause hard contact with the front der cage. Swapping from the no-name
crank to an old Deore LX crank was enough to keep it from happening.

There is definitely a point of diminishing returns in such areas, and I think Shimano passed it a
while back. The high-end bike component market is now starting to resemble the athletic shoe
business; nearly all hype of buzzword features that are of questionable value to the majority of
potential purchasers. (Not that the products are *bad*, mind you, but just that there's no good
reason to spend the extra money for the merely trendy features most of the time.)

--
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Yes, I have a killfile. If I don't respond to something,
it's also possible that I'm busy.
Words processed in a facility that contains nuts.

-----BEGIN PGP SIGNED MESSAGE-----

In article <[email hidden]>, Werehatrack

Quoted message said:

(Qui si parla Campagnolo) may have said:

Ian-<< Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff.
In practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider? >><BR><BR>

The only place stiffness differences can actually be seen on crank arms and BB spindles is on a
test machine and these differences are small.

[snip]

Quoted message said:

There is definitely a point of diminishing returns in such areas, and I think Shimano passed it a
while back. The high-end bike component market is now starting to resemble the athletic shoe
business; nearly all hype of buzzword features that are of questionable value to the majority of
potential purchasers. (Not that the products are *bad*, mind you, but just that there's no good
reason to spend the extra money for the merely trendy features most of the time.)

_ Read Keith Bontrager's rather long rant about "stiffness", very interesting.

bontrager.comindex.aspOpen ↗

_ Booker C. Bense

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Ian G Batten said:

Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff. In
practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider?

I do not know.

Tonight at a Shimano tech show, the speaker said that because frames have gotten so light and
flexible, the stiffer new Shimano crank returns stiffness to previous levels.

With a straight face.

Me? I can't flex my TA Cyclotouriste single ring enough to notice.
--
Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971

Andy-<< Tonight at a Shimano tech show, the speaker said that because frames have gotten so light
and flexible, the stiffer new Shimano crank returns stiffness to previous levels.

With a straight face.

I don't get invited to these things when they come to Boulder...I think they know what I would be
saying..Tough questions that the lizards have no answers for.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

A Muzi said:

Tonight at a Shimano tech show, the speaker said that because frames have gotten so light and
flexible, the stiffer new Shimano crank returns stiffness to previous levels.

With a straight face.

Heh. My favorite Shimano pitch was at Interbike back in the mid-80's. The pitch man was explaining
how Biopace was the end-all for cyclists and would make them healthy, wealthy and wise... but for
your more discriminating boy racer customers, Shimano had once again led the innovative push toward
(get this...) a ROUNDER chainring for the Dura Ace gruppo.

Eventually they invented the totally round chainring. Again.

Quoted message said:

Me? I can't flex my TA Cyclotouriste single ring enough to notice.

I dream of the day when I can flex a crank enough to notice.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

in my opinion, the o.p. has a troll coefficient of 0.8, but since you guys are biting...

larger diameter pipe spindles /are/ stiffer, both in torsion & bending. that's fact. [i discussed
some of the torsion math with chalo a while back.]

there is also a debate on whether it's noticeable; in my personal and highly subjective judgment,
and as a clydesdale, i definitely think so. when i first put an xt hollowtech crank on my commuter,
i was new to this new fangled spindle stuff and not expecting any difference, but my route home from
work takes me up a certain san francisco cable car grade and it was immediately apparent that there
was less flex.

does it make a difference? probably not to efficiency because the flex is effectively 100%
elastic. does it help a maladjusted front derailleur not to grind? yes. does it "feel" better?
yes, in my opinion.

but all this is irrelevant to what's really important: the fact that hollow spindles [and cranks]
allow a lighter component to be made with similar or slightly better mechanical properties than
solid ones. just like larger diameter thinner wall frame tube on big frames is a good thing -
hollow components allow the drive train to be made with the same or slightly better stiffness but
less weight.

less weight is good therefore hollow is good.

jb

A Muzi said:

Ian G Batten said:

Grand claims are made that the new XT Hollowtec cranks and ``Big Pipe'' BB are very stiff. In
practical terms, is this true, and does the stiffness of bottom brackets and cranks make a
significant difference to the rider?

I do not know.

Tonight at a Shimano tech show, the speaker said that because frames have gotten so light and
flexible, the stiffer new Shimano crank returns stiffness to previous levels.

With a straight face.

Me? I can't flex my TA Cyclotouriste single ring enough to notice.

In article <[email hidden]>,

jim beam said:

in my opinion, the o.p. has a troll coefficient of 0.8, but since you guys are biting...

It wasn't intended as such. A bike I am consider buying (Marin Mount Vision, for reasons unrelated
to its bottom bracket) has Shimano new
XT. The salesman, in passing, made claims of stiffness. I was curious as to the impact of this.

ian

A Muzi said:

Tonight at a Shimano tech show, the speaker said that because frames have gotten so light and
flexible, the stiffer new Shimano crank returns stiffness to previous levels.

With a straight face.

Me? I can't flex my TA Cyclotouriste single ring enough to notice.

Well, if Shimano is restoring a bit of stiffness to their bottom brackets, it's stiffness they
themselves took away with the advent of cartridge BBs.

I was a shop mechanic when cartridge BBs hit the market. When I went out to test ride the first bike
I had built that used one, I thought I'd broken it with the first few pedal strokes. The flex was so
much more than what I was attuned to, that it felt as if the pedals were swinging under the bike
past the centerline. The Specialized Rockhopper CrMo frame was of utterly normal status-quo
construction, so what I was feeling was the bottom bracket itself.

I can tell the difference in stiffness between different BBs, clear as day. I have a single-speed
whose sprockets catch on the chain's sideplates if I pedal too hard. That's a problem IMO, and it's
partially related to BB spindle and bearing flex.

Chalo Colina

Quoted message said:

Me? I can't flex my TA Cyclotouriste single ring enough to notice.

That surprises me. Well, no it doesn't, because it's a single ring, and where I notice the
difference between a stiffer and less-stiff crank is in chain rub on the front derailleur. You have
no front derailleur, thus no chain rub to serve as an indication of chain rub.

Larger, stronger riders most definitely notice the symptom of flex in the system. Whether it's from
the bottom bracket (frame construction), axle or chainrings... the problem of flexing enough to
cause grief with chain rub on the derailleur is real, not imaginary. Anything done to stiffen up
those areas of the bicycle is a good thing in my book.

--Mike-- Chain Reaction Bicycles chainreactionbicycles.comchainreactionbicycles.comOpen ↗

Originally posted by Mike Jacoubowsi

Quoted message said:

where I notice the difference between a stiffer and less-stiff
crank is in chain rub on the front derailleur. [...] the problem of
flexing enough to cause grief with chain rub on the derailleur
is real, not imaginary. Anything done to stiffen up
those areas of the bicycle is a good thing in my book.

FD chain rub is something that I've always attributed exclusively to frame
flex in the BB shell area. It seems unlikely to me that a short steel (or
Ti) cylinder supported near both ends is going to flex more than the frame.
But, I'm just supposing here. The crank transmits torque to the BB spindle
but it will also apply some bending force...has anybody (outside of Shimano's
R&D lab) modeled or measured that?

Anybody else with anecdotes about how replacing a conventional BB with a
large-diameter hollow spindle has reduced chain rub?

JLS

Quoted message said:

Mike J-<< the problem of flexing enough to cause grief with chain rub on the derailleur is real,
not imaginary. Anything done to stiffen up those areas of the bicycle is a good thing in my book.

Quoted message said:

Quoted message said:

<BR><BR>

(Qui si parla Campagnolo) said:

True but the 'flex' isn't in the aluminum crankarm or the 'twist' of the steel spindle. If that
'flex' was that noticable, the next thing noticed would be the spindle or the aluminum crankarm
breaking.

For a rider to say he feels arms bend or spindles twist is just bugleoil.

I have no opinion on the issue of spindle or arm flex, but I _have_ observed a rub between the front
derailer and chain as Mike described when putting a lot of force unevenly into the pedals, as I
sometimes do in tall gears. I weigh 210 pounds and often mash very tall gears.

That said, what else could cause that rub? Frame flex? If it only happened on my road bike, a
plausible explanation could be that my hands are flexing the hoods so much as to change the tension
in the derailer cable; but it has happened on my mountain bike too.

Quoted message said:

Peter Chisholm

--
Rick Onanian

fair enough. technically, your sales person is correct, but as you can see from this thread,
opinions differ on its relevance.

xt is great kit. won't let you down. have fun!

Ian G Batten said:

In article said:

in my opinion, the o.p. has a troll coefficient of 0.8, but since you guys are biting...

It wasn't intended as such. A bike I am consider buying (Marin Mount Vision, for reasons unrelated
to its bottom bracket) has Shimano new
XT. The salesman, in passing, made claims of stiffness. I was curious as to the impact of this.

ian

(Qui si parla Campagnolo) said:

For a rider to say he feels arms bend or spindles twist is just bugleoil.

The hell! When I mash down on a platform pedal attached to a regular aluminum crank and a square-
taper BB, I can not only feel the sucker sag down under my foot, I can _see_ it sag down. Some of
that sag is in the spindle, and some in the frame, but a lot of it is due to flex in the crank arm
and spindle.

I have broken square-taper spindles before. Do you suggest that they broke without ever having
flexed noticeably?

I am not claiming that Octalink or Isis are significantly better in that regard, but there is a big
difference in stiffness between a traditional crank and BB and one that is built for rigidity
(Bullseye, Primo, Profile, Redline Flite, etc.)

Chalo Colina

"Citharoedus ridetur chorda qui semper oberrat eadem." - Horace
On 29 Jan 2004 13:50:56 GMT, [email hidden] (Qui si parla

Campagnolo) said:

Mike J-<< the problem of flexing enough to cause grief with chain rub on the derailleur is real,
not imaginary. Anything done to stiffen up those areas of the bicycle is a good thing in my book.

Quoted message said:

Quoted message said:

<BR><BR>

True but the 'flex' isn't in the aluminum crankarm or the 'twist' of the steel spindle.

Where do you suppose it is, then?

Quoted message said:

If that 'flex' was that noticable, the next thing noticed would be the spindle or the aluminum
crankarm breaking.

Not necessarily. People have commented for years about flex issues with frames, brake calipers,
handlebar stems and other parts. Simply identifying that flex was happening didn't always mean that
failure of the subject part was imminent.

Quoted message said:

As I said before, these two items can be tested and compared with other crankarms and BB spindles
on a flex machine, that exerts a bunch more force than any rider...and then these values or
differences found on the machine are small, small.

Can you point to a test that shows this? The last such comparison I recall was done by a magazine
and it occurred not just a few years ago (latter '80s?). It well preceded any current model road or
mountain crank from Shimano or Campagnolo.

Quoted message said:

For a rider to say he feels arms bend or spindles twist is just bugleoil.

Well (to keep with your brassy metaphor), I think you can blow that one out your spitvalve. A couple
of months ago, I fitted my own bike with a set of the new Dura-Ace 7800 cranks. Only the crank was
changed (and the bearings to match); I even used my old chainrings. The outgoing crank (Dura-Ace
spined) was somewhat cosmetically challenged; but it, and its bottom bracket (Ultegra splined) were
mechanically uncompromised.

With the new crank, when moving away from a stop, the first eight or ten standing pedal strokes have
a distinctly different feel. I don't harbour any delusions about how much free speed I've found, but
that there has been a reduction in the amount of sag with the new cranks is unambiguous. It's
apparent even with relatively modest efforts, which leads me to think that much of what I feel is
due to the relocation of the 7800's crank bearings outboard of the bottom bracket shell.
-------------------------------
John Dacey Business Cycles, Miami, Florida Now in our twenty-first year. Our catalogue of track
equipment: eighth year online. businesscycles.combusinesscycles.comOpen ↗

Chalo:

Quoted message said:

(Qui si parla Campagnolo) said:

For a rider to say he feels arms bend or spindles twist is just bugleoil.

The hell! When I mash down on a platform pedal attached to a regular aluminum crank and a square-
taper BB, I can not only feel the sucker sag down under my foot, I can _see_ it sag down. Some of
that sag is in the spindle, and some in the frame, but a lot of it is due to flex in the crank arm
and spindle.

Quoted message said:

I have broken square-taper spindles before. Do you suggest that they broke without ever having
flexed noticeably?

I think the opposite is what Pete has said many times before, that noticeable flex will result in
broken parts soon enough.

An interesting question for you is, how long do your cranks last with noticeable flexing before you
break them?

John Dacey:

Quoted message said:

Quoted message said:

If that 'flex' was that noticable, the next thing noticed would be the spindle or the aluminum
crankarm breaking.

Not necessarily. People have commented for years about flex issues with frames, brake calipers,
handlebar stems and other parts. Simply identifying that flex was happening didn't always mean
that failure of the subject part was imminent.

It is with aluminum components. Flex is not a good thing with Al.

Quoted message said:

Quoted message said:

For a rider to say he feels arms bend or spindles twist is just bugleoil.

Well (to keep with your brassy metaphor), I think you can blow that one out your spitvalve. A
couple of months ago, I fitted my own bike with a set of the new Dura-Ace 7800 cranks. Only the
crank was changed (and the bearings to match); I even used my old chainrings. The outgoing crank
(Dura-Ace spined) was somewhat cosmetically challenged; but it, and its bottom bracket (Ultegra
splined) were mechanically uncompromised.

With the new crank, when moving away from a stop, the first eight or ten standing pedal strokes
have a distinctly different feel. I don't harbour any delusions about how much free speed I've
found, but that there has been a reduction in the amount of sag with the new cranks is
unambiguous. It's apparent even with relatively modest efforts, which leads me to think that much
of what I feel is due to the relocation of the 7800's crank bearings outboard of the bottom
bracket shell.

If true, it then means that what you felt was axial bending of the spindle, not cranks bending or
spindles twisting.

What's contentious is the notion that aluminum components in cranks and BB are noticeably felt to
flex without the components breaking soon enough. This just isn't possible, hence the attribution of
most flex to something else.