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50.4 BCD TA vs. VO



 
 
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  #21  
Old September 2nd 19, 07:49 AM posted to rec.bicycles.tech
John B. Slocomb
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Posts: 498
Default 50.4 BCD TA vs. VO

On Mon, 2 Sep 2019 15:11:57 +1000, James
wrote:

On 2/9/19 2:16 pm, John B. Slocomb wrote:


I wouldn't argue except to say that over the years I've owned quite a
number of bicycles which undoubtedly had varying BB width... and I've
never been able to tell the difference. I've never jumped on a bike
and thought "Gee, those pedals are a long ways apart" or conversely,
"Gee those pedals are really close together".


I think "Gee those pedals are a long way apart" when I ride my MTB.

It's another reason I don't like riding that bike, and why I bought a
gravel/touring bike that has a similar (if not the same) Q factor as my
road bike.


Out of curiosity what is the difference in BB/crank width ?
--

Cheers,

John B.
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  #22  
Old September 2nd 19, 05:06 PM posted to rec.bicycles.tech
Tom Kunich[_5_]
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Posts: 764
Default 50.4 BCD TA vs. VO

On Sunday, September 1, 2019 at 8:19:20 PM UTC-7, Ralph Barone wrote:
John B. Slocomb wrote:
On Sun, 1 Sep 2019 18:12:12 -0700 (PDT), Tom Kunich
wrote:

On Friday, August 30, 2019 at 7:49:45 PM UTC-7, AMuzi wrote:
On 8/30/2019 9:07 PM, Don Gillies wrote:
If a vintage crank needs an offset on one side, you can just add the
offset to the other side and substitute a symmetric crankset, so a 116
R+5 bottom bracket can be substituted with a 121 symmetric bottom
bracket (120 or 122 would work fine.)

- Don Gillies
Palo Alto, CA, USA


Which makes your tread ( aka "Q") wider.
Deal breaker for some riders.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

The iliac width is why the BB50 has become so common. People's legs do
not have to spread so wide and the length of the BB shaft is narrower
and consequently stiffer. Average hip breadth is 13" or 33 cm. So the
narrower the BB the more angularly correct a pedal spacing would be.

Time for Frank to tell us all that I don't know what I'm talking about.


By gorry Tommie! You hit the nail right on the head!

You whip out these hip width measurements like they are carved on
tablets of stone... and perhaps they are. Except that you neglect to
mention that hip width in males is noticible different than in
females. To the extent thjat a female's knee joints are closer
together then her hip joints while a male's knee joints are generally
speaking the same width.

But perhaps you are telling us that women don't ride bicycles? Or the
moon is made of blue chease?

--

Cheers,

John B.


And, of course, the important measurement when discussing Q factor is how
far apart the ankles are when doing a similar exercise like walking or
running.


The front sprockets remain in the same place. The chain line remains the same. The contact point on all of the pedal systems remain the same. So the only real difference is the depth of the crank where it attaches to the BB axle.
  #23  
Old September 3rd 19, 02:56 AM posted to rec.bicycles.tech
James[_8_]
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Posts: 6,000
Default 50.4 BCD TA vs. VO

On 2/9/19 4:49 pm, John B. Slocomb wrote:
On Mon, 2 Sep 2019 15:11:57 +1000, James
wrote:

On 2/9/19 2:16 pm, John B. Slocomb wrote:


I wouldn't argue except to say that over the years I've owned quite a
number of bicycles which undoubtedly had varying BB width... and I've
never been able to tell the difference. I've never jumped on a bike
and thought "Gee, those pedals are a long ways apart" or conversely,
"Gee those pedals are really close together".


I think "Gee those pedals are a long way apart" when I ride my MTB.

It's another reason I don't like riding that bike, and why I bought a
gravel/touring bike that has a similar (if not the same) Q factor as my
road bike.


Out of curiosity what is the difference in BB/crank width ?


I too was curious, because I remember it feels noticeably wider but I
didn't know off hand by how much, so I measured it yesterday before I
replied to you, in case the feeling was in my head. Nope, the
difference is 20 millimetres, as near as I could measure to the outside
face of each crank. 160 mm to 180 mm.

--
JS
  #24  
Old September 3rd 19, 09:03 AM posted to rec.bicycles.tech
jOHN b.
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Posts: 824
Default 50.4 BCD TA vs. VO

On Tue, 3 Sep 2019 11:56:14 +1000, James
wrote:

On 2/9/19 4:49 pm, John B. Slocomb wrote:
On Mon, 2 Sep 2019 15:11:57 +1000, James
wrote:

On 2/9/19 2:16 pm, John B. Slocomb wrote:


I wouldn't argue except to say that over the years I've owned quite a
number of bicycles which undoubtedly had varying BB width... and I've
never been able to tell the difference. I've never jumped on a bike
and thought "Gee, those pedals are a long ways apart" or conversely,
"Gee those pedals are really close together".


I think "Gee those pedals are a long way apart" when I ride my MTB.

It's another reason I don't like riding that bike, and why I bought a
gravel/touring bike that has a similar (if not the same) Q factor as my
road bike.


Out of curiosity what is the difference in BB/crank width ?


I too was curious, because I remember it feels noticeably wider but I
didn't know off hand by how much, so I measured it yesterday before I
replied to you, in case the feeling was in my head. Nope, the
difference is 20 millimetres, as near as I could measure to the outside
face of each crank. 160 mm to 180 mm.


Interesting. I've got two bikes here one with a triple front and one
with a double. I'll measure them tomorrow. The bike in Bangkok is a
old fashioned tapered shank double model and I don' remember whether
it is an original 3 piece BB or a newer "cartridge" but I'll measure
that when we get to Bangkok, the middle of the month, or so.

I don't think that I've notice4d any difference in pedal width between
the double and triple but I'll measure both bikes and than test ride
them both.

Another thing I was thinking about driving up here today. I've had
bikes with big wide pedals the kind with toe clips and straps and
changed them for clip-ons that were, maybe, half the width and than
back to wider single sided pedals and I can't remember ever noticing
what must have been some sort of difference in effective pedal width.
--
cheers,

John B.

  #25  
Old September 6th 19, 06:26 PM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,864
Default 50.4 BCD TA vs. VO

On Mon, 02 Sep 2019 11:16:46 +0700, John B Slocomb
wrote:
On Mon, 2 Sep 2019 03:19:15 +0000 (UTC), Ralph Barone
wrote:


And, of course, the important measurement when discussing Q factor is
how far apart the ankles are when doing a similar exercise like
walking or running.


I wouldn't argue except to say that over the years I've owned quite a
number of bicycles which undoubtedly had varying BB width... and I've
never been able to tell the difference. I've never jumped on a bike
and thought "Gee, those pedals are a long ways apart" or conversely,
"Gee those pedals are really close together".


I prefer narrow pedal spacing which seems to make my knees feel better.
I have had patellar inflammation in the past and have had a torn
meniscus scoped so wider cranks make my left knee hurt. People with
healthy knees might not notice Q factor differences much. My bikes are
mostly set up with old style Ritchey Logic cranks (110 mm BCD) on Campy
Veloce BBs which gives me a Q factor of 142-144 mm; my bike with
Truvativ ISIS cranks has a Q fctor of 140 mm; my old Raleigh Sports has
a Q factor of 145 mm. I don't notice the miniscule differences between
those. My tandem has Shimano cranks with a Q factor of 170 mm and that
is very noticeable and feels noticeable throughout the ride. I lost out
on a set of Ritchey Logic tendem cranks a number of years ago through
inattention; still bummed about that.

My wife- with wider pelvis than me and a bit knock-kneed- prefers a
wider Q factor of 160 mm or so. She sets her SPD cleats as far in as
she can and complains of discomfort if the Q factor is too narrow.

For that matter, I see people running and their stride seems wider
with running shoes on than when barefoot.


I have read claims that when running people's effective Q factor is less
than zero- their feet overlap along the centerline of their stride.
I've never bothered to verify that but suspect that this is true for
some folks and not true for others. Contrary to Tom's claim, pelvic
and leg geometry vary widely (no pun intended).

As always, I may be wrong, but like many of the things that seem to be
of such major concern, I just can't believe that pedal width (within
reason) is THAT important. --


For people with normal healthy knees and average body geometry, it is
probably not important and usually not even noticeable. People who are
outliers- especially with very short legs, bowlegged or knock-kneed,
etc.- Q factor differences might be noticeable. The hips move in all
dimensions to accommodate movement- otherwise we'd only be able to walk
or run of certain kinds of terrain.
  #26  
Old September 6th 19, 06:50 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 7,595
Default 50.4 BCD TA vs. VO

On 9/6/2019 1:26 PM, Tim McNamara wrote:

I prefer narrow pedal spacing which seems to make my knees feel better.
I have had patellar inflammation in the past and have had a torn
meniscus scoped so wider cranks make my left knee hurt.


Maybe 20 years ago I started getting some minor pain in one knee. In
trying to diagnose it, I somehow noticed that I seemed to be applying
force toward the outside of the pedal, using the outside edge of my
foot. I began concentrating on using the ball of my foot (just behind
the big toe) to apply force, and my knee problems largely went away.

For people with normal healthy knees and average body geometry, it is
probably not important and usually not even noticeable. People who are
outliers- especially with very short legs, bowlegged or knock-kneed,
etc.- Q factor differences might be noticeable.


Agreed. Also, people who ride only short distances at low effort may
never notice a difference. That's the vast majority of bicyclists.

--
- Frank Krygowski
 




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