Chain Line
 

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.

--
Cheers,

John B.

Chain Line
 

On 6/13/2017 9:09 PM, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


Good start but you ought to measure from frame to rings
because ring position (which matters for this) may be closer
or farther from crank arm on various models.

Designers have great latitude for all those parts (arms,
spindle, bearings, rings) to achieve any given chainline.
For example, older square arms were straight on the outer
face with long spindles. Later designs curve using a shorter
spindles with no change in chainline, AEBE.

http://www.yellowjersey.org/photosfr...t/CRSPNDLS.JPG


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

Chain Line
 

On Wednesday, June 14, 2017 at 5:58:51 AM UTC-7, AMuzi wrote:
On 6/13/2017 9:09 PM, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


Good start but you ought to measure from frame to rings
because ring position (which matters for this) may be closer
or farther from crank arm on various models.

Designers have great latitude for all those parts (arms,
spindle, bearings, rings) to achieve any given chainline.
For example, older square arms were straight on the outer
face with long spindles. Later designs curve using a shorter
spindles with no change in chainline, AEBE.

http://www.yellowjersey.org/photosfr...t/CRSPNDLS.JPG

When I did this measurement I did it by putting it in a gear where I had a perfectly straight chain-line to the third or forth cog (don't remember which). When I changed to the hollow two piece crank there was no discernable chain line change.

The only reason I'm presently using square taper is that I had all the parts to put two triples on my two steel bikes.

Chain Line
 

On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.

--
Regards, Joerg

http://www.analogconsultants.com/

Chain Line
 

On 15/06/17 06:31, Joerg wrote:
On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.


On my previous frame, I migrated from Campagnolo square tapered BB &
cranks to Campagnolo outboard bearing BB assy, and the chain line didn't
shift 10mm.

Why do you think you are special?

--
JS

Chain Line
 

On 2017-06-14 15:28, James wrote:
On 15/06/17 06:31, Joerg wrote:
On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.


On my previous frame, I migrated from Campagnolo square tapered BB &
cranks to Campagnolo outboard bearing BB assy, and the chain line didn't
shift 10mm.


Did you buy new cranks? If not, was there sufficient clearance to make
up for the added millimeter of the outboard bearing? On my bike there isn't.


Why do you think you are special?


See above. There simply is no room for another 11mm without the crank
moving at least 10mm outward. Naturally, the goal was to keep the
Shimano 600 cranks. Installing a UN55 internal cartridge bearing allowed
me to do that and so that is what I did.

--
Regards, Joerg

http://www.analogconsultants.com/

Chain Line
 

On Wed, 14 Jun 2017 13:31:57 -0700, Joerg
wrote:

On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.

You must have a very strange bicycle as at least three others have
commented that when they changed from the older BB to a more modern
one that the chain line didn't change.

I can only assume that you are unique.
--
Cheers,

John B.

Chain Line
 

On 6/14/2017 5:28 PM, James wrote:
On 15/06/17 06:31, Joerg wrote:
On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old
square
tapered BB to a modern Shimano outboard bearing bracket.
The argument
was that this would destroy the perfect chain line of the
original
three piece BB.

Now, I have changed back and forth between the original
square tapered
axle to the outboard bearing BB and to my recollection
the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit
some of my
wife's relatives and as we used my wife's car she drove.
It is about
250 Km, one way, so I had a lot of time to think abut
things and one
of the things I thought about was how could I change
bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did
some measuring
and it turns out that with the old fashioned three piece
BB there is
slightly over 10mm clearance between the inner edge of
the crank arm
and the outer edge of the BB. The outboard bearing
"flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern
BB results in
very little, if any, difference in chain line. Certainly
less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above
does explain why
I, after switching from one type to the other, and back
again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600
gear which is
what I have on my road bike. The clearance from the inner
edge of the
drive side crank to the outer surface of the BB is 3mm.
Now assume your
12mm measurement minus the 1mm that the regular cartridge
BB has. That's
already 11mm of chain line offset. A lot. You could reduce
the clearance
to 2mm but that much wiggle room you really need for
square taper and
that would still leave you with a chain line 10mm off from
where it was.


On my previous frame, I migrated from Campagnolo square
tapered BB & cranks to Campagnolo outboard bearing BB assy,
and the chain line didn't shift 10mm.

Why do you think you are special?


Chainline errors are entirely from not using the
manufacturer's specified parts.

Only a complete idiot would pull a functional spark plug
from a V8 and drop it into a 4-cyl Asian econobox. Yet
people mix arms and spindles which are ridiculously
incompatible every day and then ride over here to complain
that the crank's no good. Oy!

p.s. Almost all derailleur systems will work well with
+1mm/-1mm chainline error. Few can accept 10mm either way,
that is a very large distance.

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

Chain Line
 

On 2017-06-14 18:19, John B. wrote:
On Wed, 14 Jun 2017 13:31:57 -0700, Joerg
wrote:

On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.

You must have a very strange bicycle as at least three others have
commented that when they changed from the older BB to a more modern
one that the chain line didn't change.

I can only assume that you are unique.


Gazelle Trim Trophy frame from the Netherlands and Shimano 600 BB,
cranks, derailers, brakes. Not unusual at all for that era (80's).

--
Regards, Joerg

http://www.analogconsultants.com/

Chain Line
 

On 15/06/17 08:33, Joerg wrote:
On 2017-06-14 15:28, James wrote:
On 15/06/17 06:31, Joerg wrote:
On 2017-06-13 19:09, John B. wrote:

In a recent discussion I suggested changing from the old square
tapered BB to a modern Shimano outboard bearing bracket. The argument
was that this would destroy the perfect chain line of the original
three piece BB.

Now, I have changed back and forth between the original square tapered
axle to the outboard bearing BB and to my recollection the chain line
didn't seem to change noticeably.

Over the weekend we took a trip "up country" to visit some of my
wife's relatives and as we used my wife's car she drove. It is about
250 Km, one way, so I had a lot of time to think abut things and one
of the things I thought about was how could I change bottom brackets
with no appreciable difference in chain line.

This morning I turned one of my bikes bottom up and did some measuring
and it turns out that with the old fashioned three piece BB there is
slightly over 10mm clearance between the inner edge of the crank arm
and the outer edge of the BB. The outboard bearing "flanges" measured
12mm in thickness and the old sty;e BB flange is `1mm..

Thus the changing from the old style to the more modern BB results in
very little, if any, difference in chain line. Certainly less then the
difference between two cogs on the cassette.

Granted that bicycles are all different but the above does explain why
I, after switching from one type to the other, and back again, have
seen no noticeable difference in chain line.


The discussion you were referring to was about Shimano 600 gear which is
what I have on my road bike. The clearance from the inner edge of the
drive side crank to the outer surface of the BB is 3mm. Now assume your
12mm measurement minus the 1mm that the regular cartridge BB has. That's
already 11mm of chain line offset. A lot. You could reduce the clearance
to 2mm but that much wiggle room you really need for square taper and
that would still leave you with a chain line 10mm off from where it was.


On my previous frame, I migrated from Campagnolo square tapered BB &
cranks to Campagnolo outboard bearing BB assy, and the chain line didn't
shift 10mm.


Did you buy new cranks? If not, was there sufficient clearance to make
up for the added millimeter of the outboard bearing? On my bike there
isn't.


Is there an outboard BB bearing assembly that uses a square tapered axle?

I don't know. I bought a Campag Ultra Torque crank & BB assy back in
2007-8. I've replaced the bearings once, about 5 years ago. No bearing
slop noticeable yet.


Why do you think you are special?


See above. There simply is no room for another 11mm without the crank
moving at least 10mm outward. Naturally, the goal was to keep the
Shimano 600 cranks. Installing a UN55 internal cartridge bearing allowed
me to do that and so that is what I did.


So you think you're special because you want to keep cranks that aren't
compatible.

Good luck.

--
JS