Frame Modification

As I believe I've mentioned I rebuilt a Japanese road bike with
horizontal, forward facing rear dropouts which I've never been really
satisfied with.

I got to thinking that if I simply sawed off the rear dropouts and
replaced then with socket type rear dropouts with the modern
vertically oriented openings I could, with the exception of paint
damage, have what I preferred with minimal work.

When I measured the dropouts it appears that the newer dropouts will
move the position of the axle forward about 1/4" (about 6mm) and
reduce the wheelbase from the present 1 metre by that amount.
Clearance between the wheel and the chain stay bridge will decrease by
the same amount but that isn't a problem as the bridge is already very
far forward due to the present horizontal dropout slots.

Alignment shouldn't present a problem as simply installing a bare
wheel in the tacked or pinned dropouts should be sufficient for
vertical alignment and a taunt string from the front wheel will show
any horizontal misalignment.

The present rear brake calipers have the brake pads as low as possible
with about 1/2" vertical movement available so I don't believe that
wheel - brake bridge clearance will be a problem.

As far as I can tell without the replacement dropouts actually in hand
there should be no problem with either chain stay or seat stay angular
alignment.

And finally, I do have the necessary skills to do the job.

Any comments? Have I overlooked anything?
--
cheers,

John B.

On 1/6/2017 10:59 PM, John B. wrote:

As I believe I've mentioned I rebuilt a Japanese road bike with
horizontal, forward facing rear dropouts which I've never been really
satisfied with.

I got to thinking that if I simply sawed off the rear dropouts and
replaced then with socket type rear dropouts with the modern
vertically oriented openings I could, with the exception of paint
damage, have what I preferred with minimal work.

When I measured the dropouts it appears that the newer dropouts will
move the position of the axle forward about 1/4" (about 6mm) and
reduce the wheelbase from the present 1 metre by that amount.
Clearance between the wheel and the chain stay bridge will decrease by
the same amount but that isn't a problem as the bridge is already very
far forward due to the present horizontal dropout slots.

Alignment shouldn't present a problem as simply installing a bare
wheel in the tacked or pinned dropouts should be sufficient for
vertical alignment and a taunt string from the front wheel will show
any horizontal misalignment.

The present rear brake calipers have the brake pads as low as possible
with about 1/2" vertical movement available so I don't believe that
wheel - brake bridge clearance will be a problem.

As far as I can tell without the replacement dropouts actually in hand
there should be no problem with either chain stay or seat stay angular
alignment.

And finally, I do have the necessary skills to do the job.

Any comments? Have I overlooked anything?


I don't think you have. There are a variety of frame ends in
each format. Some are longer, some shorter, different angles
between chainstay/seatstay, etc.

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

In theory, changing axle height changes geometry/handling
but in practice that seems slight in your case. We'd select
a pair of ends to avoid that change but hey it's your bike
and may not be even noticeable to you. It's simpler when you
have a selection at hand.

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

https://www.google.com/#q=wheels+mfg+dropout

with slanting rear dropouts add an adjuster ...best. takes up chin slack in adjusts wheelbase for loads

string goes from down tube past seat tube with plywood shims holding string from tubing then measure distances with steel rule for an idea of where the frame is or is not.

On Saturday, January 7, 2017 at 11:00:06 AM UTC-5, DATAKOLL MARINE RESEARCH wrote:
string goes from down tube past seat tube with plywood shims holding string from tubing then measure distances with steel rule for an idea of where the frame is or is not.

AHA ! WWTToN ?

goo.gl/Itr6pv

On Sat, 07 Jan 2017 08:42:37 -0600, AMuzi wrote:

On 1/6/2017 10:59 PM, John B. wrote:

As I believe I've mentioned I rebuilt a Japanese road bike with
horizontal, forward facing rear dropouts which I've never been really
satisfied with.

I got to thinking that if I simply sawed off the rear dropouts and
replaced then with socket type rear dropouts with the modern
vertically oriented openings I could, with the exception of paint
damage, have what I preferred with minimal work.

When I measured the dropouts it appears that the newer dropouts will
move the position of the axle forward about 1/4" (about 6mm) and
reduce the wheelbase from the present 1 metre by that amount.
Clearance between the wheel and the chain stay bridge will decrease by
the same amount but that isn't a problem as the bridge is already very
far forward due to the present horizontal dropout slots.

Alignment shouldn't present a problem as simply installing a bare
wheel in the tacked or pinned dropouts should be sufficient for
vertical alignment and a taunt string from the front wheel will show
any horizontal misalignment.

The present rear brake calipers have the brake pads as low as possible
with about 1/2" vertical movement available so I don't believe that
wheel - brake bridge clearance will be a problem.

As far as I can tell without the replacement dropouts actually in hand
there should be no problem with either chain stay or seat stay angular
alignment.

And finally, I do have the necessary skills to do the job.

Any comments? Have I overlooked anything?


I don't think you have. There are a variety of frame ends in
each format. Some are longer, some shorter, different angles
between chainstay/seatstay, etc.

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

I was thinking about socketed frame ends see:
http://www.framebuilding.com/NEWPART...20Dropouts.htm
(top three) as I could then simply saw the ends of the stays of and
insert the ends into the new fame ends rather than trying to get the
old frame end out and all the brazing brass so the new one would fit.
Providing, or course, the angle of the chain/seat stays is correct.

In theory, changing axle height changes geometry/handling
but in practice that seems slight in your case. We'd select
a pair of ends to avoid that change but hey it's your bike
and may not be even noticeable to you. It's simpler when you
have a selection at hand.

I haven't done any exact measuring but the axle position reference
chain stay center line appears to be about the same height on two
bikes I have here, one with conventional vertical drop outs and one
with horizontal dropouts, and the "horizontal dropouts aren't exactly
horizontal so depending on the position of the axle I would guess that
there is some difference in front fork angle (actually head tube angle
:-)

My thinking at the moment is that while there might be some change in
axle height it probably won't be greater than that of changing tire
size - say 19mm to 25mm.

--
cheers,

John B.

On Saturday, January 7, 2017 at 4:49:43 PM UTC-8, John B. wrote:
On Sat, 07 Jan 2017 08:42:37 -0600, AMuzi wrote:

On 1/6/2017 10:59 PM, John B. wrote:

As I believe I've mentioned I rebuilt a Japanese road bike with
horizontal, forward facing rear dropouts which I've never been really
satisfied with.

I got to thinking that if I simply sawed off the rear dropouts and
replaced then with socket type rear dropouts with the modern
vertically oriented openings I could, with the exception of paint
damage, have what I preferred with minimal work.

When I measured the dropouts it appears that the newer dropouts will
move the position of the axle forward about 1/4" (about 6mm) and
reduce the wheelbase from the present 1 metre by that amount.
Clearance between the wheel and the chain stay bridge will decrease by
the same amount but that isn't a problem as the bridge is already very
far forward due to the present horizontal dropout slots.

Alignment shouldn't present a problem as simply installing a bare
wheel in the tacked or pinned dropouts should be sufficient for
vertical alignment and a taunt string from the front wheel will show
any horizontal misalignment.

The present rear brake calipers have the brake pads as low as possible
with about 1/2" vertical movement available so I don't believe that
wheel - brake bridge clearance will be a problem.

As far as I can tell without the replacement dropouts actually in hand
there should be no problem with either chain stay or seat stay angular
alignment.

And finally, I do have the necessary skills to do the job.

Any comments? Have I overlooked anything?


I don't think you have. There are a variety of frame ends in
each format. Some are longer, some shorter, different angles
between chainstay/seatstay, etc.

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

I was thinking about socketed frame ends see:
http://www.framebuilding.com/NEWPART...20Dropouts.htm
(top three) as I could then simply saw the ends of the stays of and
insert the ends into the new fame ends rather than trying to get the
old frame end out and all the brazing brass so the new one would fit.
Providing, or course, the angle of the chain/seat stays is correct.

In theory, changing axle height changes geometry/handling
but in practice that seems slight in your case. We'd select
a pair of ends to avoid that change but hey it's your bike
and may not be even noticeable to you. It's simpler when you
have a selection at hand.

I haven't done any exact measuring but the axle position reference
chain stay center line appears to be about the same height on two
bikes I have here, one with conventional vertical drop outs and one
with horizontal dropouts, and the "horizontal dropouts aren't exactly
horizontal so depending on the position of the axle I would guess that
there is some difference in front fork angle (actually head tube angle
:-)

My thinking at the moment is that while there might be some change in
axle height it probably won't be greater than that of changing tire
size - say 19mm to 25mm.

John, this isn't a simple case of cutting and brazing. Under normal construction the ends of the stays are inserted and brazed into the dropouts FIRST because that is what they are sized for. Remember that many of these stays are tapered.

So be careful in your measurements to be sure that the NEW vertical drop-outs will fit inside of the modified stays.