Question on rear dropout adjusting screws

kwalters said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Both. If they are something other than the long Campy 1010 drop outs,
you don't get much wheelbase adjustment.

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

No. They are frequently removed or lost. -- Jay Beattie.

rear wheel alignment is sighted to the seatpost-bike upside down,
seat off-then when the axle nuts are tightened, until you develop
technique, the wheel moves toward the side getting snugged and out of
alignment. turn with two hands at once to develop technique. hold the
wheel steady with the third hand.
the screws aid the alignment process by setting the wheel closer to
the desired alignment if not directly on the alignment as the
alignment in reality is dependent on other variables eg dish
there is an aftermarket dropout half round spacer in two parts with a
groove that sets over the dropout, with a holding screw thru the
center-does similar

kwalters said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Both. Dropouts often were poorly aligned, and these screws took care of
much of the problem. Also, you could decide whether to lengthen/shorten
the wheelbase a bit and still be able to quickly mount a wheel.

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Umm, the hole is already there, whether or not there is a screw in it.
You can't weaken the dropout by removing the screw.

--

David L. Johnson

Anyone who is capable of getting themselves made President should on
no account be allowed to do the job.
-- Douglas Adams

David L. Johnson said:

kwalters said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Both. Dropouts often were poorly aligned, and these screws took care of
much of the problem. Also, you could decide whether to lengthen/shorten
the wheelbase a bit and still be able to quickly mount a wheel.

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Umm, the hole is already there, whether or not there is a screw in it.
You can't weaken the dropout by removing the screw.

Dear David,

Wood isn't metal, and the dropouts probably aren't stressed enough to
matter, but Professor Gordon _may_ disagree with you:

"In general, fastenings like nails and screws do not much weaken
timber, always provided that they are in place and fit tightly. Once
they are removed, however, the resulting hole has a much more serious
effect; and no doubt the same is true of knots in timber. In a highly
stressed wooden structure, such as a glider or a yacht's mast, it is
therefore wise to leave unwanted nails and screws alone and not try to
pull them out. If needs be, they can be cut off flush with the surface
of the wood."

--"Structures," J.E. Gordon, p. 283

http://books.google.com/books?id=wQ0THyS6k4QC&pg=RA1-PA283&lpg=RA1-PA283&dq=gordon+nails+wood+mast+structures&source=web&ots=miKFY571hm&sig=GxfYm6WmVQiK76SWbuJKGIhGYBo

Possibly some engineers will discuss how much threaded bolts in metal
dropouts resemble threaded screws in wooden masts. It may turn out
that they're as different as night and day.

Cheers,

Carl Fogel

kwalters said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Thanks. Ken

Did adjust for less than straight frames and also acted as a b limit
screw, moving top pulley away from the cogs(slide wheel aft), before
there were b limit screws.

Removing them has no effect on dropout strength.

Qui si parla Campagnolo said:

Did adjust for less than straight frames and also acted as a b limit
screw, moving top pulley away from the cogs(slide wheel aft), before
there were b limit screws.

Removing them has no effect on dropout strength.

Hmm.. maybe it's just me, but I never set the screws for "back as far
as possible. Typically I have mine at about "1/3 from the rear".

I've always treated it like a gauge or meter - normal operation should
be somewhere near the middle third of the gauge, not at either
extreme.

hmmm. try roping the hub rearward with a shock cord, or find a friend
or otherwise with a hand to push the wheel against the screw set
midway then align the rim-best to align with the tire off-as evenly
spaced sighted along the rim then against the seat tube
the visible seat tube % to the right of the right rim edge should be a
rectangle not a parallelogram

the screw is loose in the hole. there is a thread percentage. a high
thread percentage means there's more metal in there than space, more
grip but removal is harder. that's what loctite does, it fills the
void between make and female threads so the screw doesn't wiggle and
slide on a ramp to go in or out.

you can blue loctite the screws in place after cleaning the surfaces
with CHO

still me said:

On Sat, 23 Jun 2007 05:41:38 -0700, Qui si parla Campagnolo

Quoted message said:

Did adjust for less than straight frames and also acted as a b limit
screw, moving top pulley away from the cogs(slide wheel aft), before
there were b limit screws.

Quoted message said:

Removing them has no effect on dropout strength.

Hmm.. maybe it's just me, but I never set the screws for "back as far
as possible. Typically I have mine at about "1/3 from the rear".

I've always treated it like a gauge or meter - normal operation should
be somewhere near the middle third of the gauge, not at either
extreme.

Me neither. I place them in my Merckx so that the line of the seatstay
lines up with the axle but for bigg-ish freewheels, like 13-28s,
sometimes gotta move the wheel aft to get the top pulley off the
biggest cog, and still have enough chain for big-big combo.

Ken Walters said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

They stop the wheel when it is at the depth of engagement you want.
This was done so that fixed gear riders could set their chain tension
and switch back and forth between fixed gear and derailleur wheels.
Then after a while the depth of slot was made shorter and finally the
fixed gear idea went away, it being a bit of folklore.

I believe the concept arose because only track riders who rode indoor
tracks were in good condition after each winter and it was said that
the fixed gear was the key. No one noticed that these riders rode
much of the winter while many road riders sat it out. It's like the
belief in Power Cranks. They'll go away.

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout
will have a hole through it fore and aft?

The derailleur sifts better if the axle is not at the end of the slot
but if that isn't noticeable, take them out. Besides, their ends get
bent when they bump into a solid object. I made my own vertical
dropouts that Cinelli used when making my bicycles in the 1960's...,
before he gave a set to his friend Tullio, who put them into
production.

Jobst Brandt

Carl Fogel said:

Quoted message said:

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Quoted message said:

Quoted message said:

Both. Dropouts often were poorly aligned, and these screws took
care of much of the problem. Also, you could decide whether to
lengthen/shorten the wheelbase a bit and still be able to quickly
mount a wheel.

Quoted message said:

Quoted message said:

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout
will have a hole through it fore and aft?

Quoted message said:

Quoted message said:

Umm, the hole is already there, whether or not there is a screw in
it. You can't weaken the dropout by removing the screw.

Quoted message said:

Wood isn't metal, and the dropouts probably aren't stressed enough
to matter, but Professor Gordon _may_ disagree with you:

# In general, fastenings like nails and screws do not much weaken
# timber, always provided that they are in place and fit tightly.
# Once they are removed, however, the resulting hole has a much more
# serious effect; and no doubt the same is true of knots in timber.
# In a highly stressed wooden structure, such as a glider or a yacht's
# mast, it is therefore wise to leave unwanted nails and screws alone
# and not try to pull them out. If needs be, they can be cut off
# flush with the surface of the wood.

Quoted message said:

--"Structures," J.E. Gordon, p. 283

http://tinyurl.com/2b7m9n

Quoted message said:

Possibly some engineers will discuss how much threaded bolts in metal
dropouts resemble threaded screws in wooden masts. It may turn out
that they're as different as night and day.

They are. But the screws are loose in the holes using spring load to
keep them from changing position (as tension in spokes does for spoke
nipples.) They cannot add to rigidity, and if tight, could only
effect strength negatively an immeasurable amount, lying in the
neutral bending axis.

Jobst Brandt

Quoted message said:

Carl Fogel said:

Quoted message said:

> Have an older steel frame with adjusting screws in each dropout.
> Just what do these do? Compensate for misaligned dropouts? Allow
> the wheelbase to be shortened/lengthened? Both former and latter?

Quoted message said:

Quoted message said:

Both. Dropouts often were poorly aligned, and these screws took
care of much of the problem. Also, you could decide whether to
lengthen/shorten the wheelbase a bit and still be able to quickly
mount a wheel.

Quoted message said:

Quoted message said:

> If I take them out, do I weaken the dropouts, since each dropout
> will have a hole through it fore and aft?

Quoted message said:

Quoted message said:

Umm, the hole is already there, whether or not there is a screw in
it. You can't weaken the dropout by removing the screw.

Quoted message said:

Wood isn't metal, and the dropouts probably aren't stressed enough
to matter, but Professor Gordon _may_ disagree with you:

# In general, fastenings like nails and screws do not much weaken
# timber, always provided that they are in place and fit tightly.
# Once they are removed, however, the resulting hole has a much more
# serious effect; and no doubt the same is true of knots in timber.
# In a highly stressed wooden structure, such as a glider or a yacht's
# mast, it is therefore wise to leave unwanted nails and screws alone
# and not try to pull them out. If needs be, they can be cut off
# flush with the surface of the wood.

Quoted message said:

--"Structures," J.E. Gordon, p. 283

http://tinyurl.com/2b7m9n

Quoted message said:

Possibly some engineers will discuss how much threaded bolts in metal
dropouts resemble threaded screws in wooden masts. It may turn out
that they're as different as night and day.

They are. But the screws are loose in the holes using spring load to
keep them from changing position (as tension in spokes does for spoke
nipples.) They cannot add to rigidity, and if tight, could only
effect strength negatively an immeasurable amount, lying in the
neutral bending axis.

the screw holes are not in the neutral bending axis for dropout opening
- derailleur caught in spokes for example. nor in the neutral axis for
dropout torsion. they're only neutral for a strict bend about the screw
hole axis - a most unlikely scenario.

"kwalters" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Thanks. Ken

As several others have noted, it makes no difference strength wise if you
have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to that
there was no standard and this created some problems with index shifting.

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the chainstays
and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in chainstay
length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and the
sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs ( the
"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the chain
gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

On some older frames with short Chainstays moving the wheel back or
forward was the only way to correct for chain length problems.

One other thing, on a lot of bikes you could adjust the head tube angle by
a degree or so by moving the rear wheel position. It's questionable
whether this was a design function or just a poorly built frame.

I've seen older bike that you could change the head tube angle from 72° to
75° with the old, long Campy 1010 rear dropouts. I've heard tell that you
could use the same bike for criterium and road racing.

The right adjusting screw can help a little in preventing wheel suck -
where the wheel shifts and rubs on the left chainstay usually from honking
or sprinting.

The first generation? of Suntour dropouts with a derailleur hanger and
adjusting screws had a propensity to break off at the adjusting screw
hole. These were the dropouts that had a wider attachment point for the
seatstays. They were probably made from a hardened low strength steel.

It was the left dropout that usually broke and was probably the result of
wheel suck.

Chas.

* * Chas said:

"kwalters" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Thanks. Ken

As several others have noted, it makes no difference strength wise if you
have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to that
there was no standard and this created some problems with index shifting.

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the chainstays
and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in chainstay
length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and the
sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs ( the
"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the chain
gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

On some older frames with short Chainstays moving the wheel back or
forward was the only way to correct for chain length problems.

One other thing, on a lot of bikes you could adjust the head tube angle by
a degree or so by moving the rear wheel position. It's questionable
whether this was a design function or just a poorly built frame.

I've seen older bike that you could change the head tube angle from 72� to
75� with the old, long Campy 1010 rear dropouts. I've heard tell that you
could use the same bike for criterium and road racing.

The right adjusting screw can help a little in preventing wheel suck -
where the wheel shifts and rubs on the left chainstay usually from honking
or sprinting.

The first generation? of Suntour dropouts with a derailleur hanger and
adjusting screws had a propensity to break off at the adjusting screw
hole. These were the dropouts that had a wider attachment point for the
seatstays. They were probably made from a hardened low strength steel.

"hardened low strength steel"??? that's an oxymoron. more likely they
were cast or just plain low strength.

Quoted message said:

It was the left dropout that usually broke and was probably the result of
wheel suck.

Chas.

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

* * Chas said:

"kwalters" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Thanks. Ken

As several others have noted, it makes no difference strength wise if

you

Quoted message said:

Quoted message said:

have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to

that

Quoted message said:

Quoted message said:

there was no standard and this created some problems with index

shifting.

Quoted message said:

Quoted message said:

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the

chainstays

Quoted message said:

Quoted message said:

and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in

chainstay

Quoted message said:

Quoted message said:

length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and

the

Quoted message said:

Quoted message said:

sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs

( the

Quoted message said:

Quoted message said:

"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the

chain

Quoted message said:

Quoted message said:

gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

On some older frames with short Chainstays moving the wheel back or
forward was the only way to correct for chain length problems.

One other thing, on a lot of bikes you could adjust the head tube

angle by

Quoted message said:

Quoted message said:

a degree or so by moving the rear wheel position. It's questionable
whether this was a design function or just a poorly built frame.

I've seen older bike that you could change the head tube angle from

72? to

Quoted message said:

Quoted message said:

75? with the old, long Campy 1010 rear dropouts. I've heard tell that

you

Quoted message said:

Quoted message said:

could use the same bike for criterium and road racing.

The right adjusting screw can help a little in preventing wheel suck -
where the wheel shifts and rubs on the left chainstay usually from

honking

Quoted message said:

Quoted message said:

or sprinting.

The first generation? of Suntour dropouts with a derailleur hanger and
adjusting screws had a propensity to break off at the adjusting screw
hole. These were the dropouts that had a wider attachment point for

the

Quoted message said:

Quoted message said:

seatstays. They were probably made from a hardened low strength steel.

"hardened low strength steel"??? that's an oxymoron. more likely they
were cast or just plain low strength.

They could have been made of case hardened 1018 low carbon steel FOOL!

Chas.

* * Chas said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

* * Chas said:

"kwalters" <[email hidden]> wrote in message
news:[email hidden]...
> Have an older steel frame with adjusting screws in each dropout.
> Just what do these do? Compensate for misaligned dropouts? Allow
> the wheelbase to be shortened/lengthened? Both former and latter?
>
> If I take them out, do I weaken the dropouts, since each dropout will
> have a hole thru it fore and aft?
>
> Thanks. Ken
>
As several others have noted, it makes no difference strength wise if

you

Quoted message said:

Quoted message said:

have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to

that

Quoted message said:

Quoted message said:

there was no standard and this created some problems with index

shifting.

Quoted message said:

Quoted message said:

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the

chainstays

Quoted message said:

Quoted message said:

and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in

chainstay

Quoted message said:

Quoted message said:

length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and

the

Quoted message said:

Quoted message said:

sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs

( the

Quoted message said:

Quoted message said:

"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the

chain

Quoted message said:

Quoted message said:

gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

On some older frames with short Chainstays moving the wheel back or
forward was the only way to correct for chain length problems.

One other thing, on a lot of bikes you could adjust the head tube

angle by

Quoted message said:

Quoted message said:

a degree or so by moving the rear wheel position. It's questionable
whether this was a design function or just a poorly built frame.

I've seen older bike that you could change the head tube angle from

72? to

Quoted message said:

Quoted message said:

75? with the old, long Campy 1010 rear dropouts. I've heard tell that

you

Quoted message said:

Quoted message said:

could use the same bike for criterium and road racing.

The right adjusting screw can help a little in preventing wheel suck -
where the wheel shifts and rubs on the left chainstay usually from

honking

Quoted message said:

Quoted message said:

or sprinting.

The first generation? of Suntour dropouts with a derailleur hanger and
adjusting screws had a propensity to break off at the adjusting screw
hole. These were the dropouts that had a wider attachment point for

the

Quoted message said:

Quoted message said:

seatstays. They were probably made from a hardened low strength steel.

"hardened low strength steel"??? that's an oxymoron. more likely they
were cast or just plain low strength.

They could have been made of case hardened 1018 low carbon steel FOOL!

joke presumably?

Hide quoted text -

LOCTITE?

* * Chas said:

"kwalters" <[email hidden]> wrote in message

news:[email hidden]...

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout will
have a hole thru it fore and aft?

Quoted message said:

Thanks. Ken

As several others have noted, it makes no difference strength wise if you
have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to that
there was no standard and this created some problems with index shifting.

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the chainstays
and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in chainstay
length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and the
sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs ( the
"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the chain
gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

<snip>

For me, moving the wheel never made much of a difference in shifting
with the NR derailleur. I just centered it in the dropouts and forgot
about it -- unless I had bad race anxiety and needed more mojo, then I
would shorten the wheel base and convince myself it made a difference.
It had about the same effect as making sure the file tread on my sew-
ups was going the right direction, or that the CG was on the rear and
the CX in front.-- Jay Beattie.

"Jay Beattie" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

* * Chas said:

"kwalters" <[email hidden]> wrote in message

news:[email hidden]...

Quoted message said:

Have an older steel frame with adjusting screws in each dropout.
Just what do these do? Compensate for misaligned dropouts? Allow
the wheelbase to be shortened/lengthened? Both former and latter?

Quoted message said:

If I take them out, do I weaken the dropouts, since each dropout

will

Quoted message said:

Quoted message said:

Quoted message said:

have a hole thru it fore and aft?

Quoted message said:

Thanks. Ken

As several others have noted, it makes no difference strength wise if

you

Quoted message said:

Quoted message said:

have the screws in or not.

The screws serve a number of purposes.

In the late 1980s Shimano set the standard for location of the rear
derailleur gear hanger bolt hole relative to the hub axle. Prior to

that

Quoted message said:

Quoted message said:

there was no standard and this created some problems with index

shifting.

Quoted message said:

Quoted message said:

One of the first reasons for the adjustment screws was to aid in
reinstalling rear wheels to quickly position them between the

chainstays

Quoted message said:

Quoted message said:

and locate them above the derailleur for the proper chain gap.

A lot of bike frames were pretty crudely made and differences in

chainstay

Quoted message said:

Quoted message said:

length of up to a 1/4" (6mm) was not uncommon. On a lot of older
derailleurs the chain gap - the distance between the jockey pulley and

the

Quoted message said:

Quoted message said:

sprockets - was critical for good shifting.

Suntour and later Shimano put adjusting screws on their derailleurs

( the

Quoted message said:

Quoted message said:

"B" dimension that Peter mentioned ) for correcting this distance but
positioning the wheel forward or back was the only way to adjust the

chain

Quoted message said:

Quoted message said:

gap with derailleurs based on Campy's 1960s Record design which many
makers copied.

<snip>

For me, moving the wheel never made much of a difference in shifting
with the NR derailleur. I just centered it in the dropouts and forgot
about it -- unless I had bad race anxiety and needed more mojo, then I
would shorten the wheel base and convince myself it made a difference.
It had about the same effect as making sure the file tread on my sew-
ups was going the right direction, or that the CG was on the rear and
the CX in front.-- Jay Beattie.

On some bikes it didn't make too much difference. I've seen bikes where
you could increase or decrease the head tube angle by up to 2 degrees by
moving the wheel - 75° for criteriums and 73° for road races. With the
longer 1010a dropouts you can change the wheel base length at least 20mm,
even more with the older 1010 dropouts.

The adjustability being more of a function of dropout length than
adjustment screws.

The notion of adjustable frames came down from the old-time bikies and
framesmiths in the early 1970s. We had several ex-pat Brits in our cycling
group one of whom raced semi-pro in Blighty.

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

* * Chas said:

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

* * Chas wrote:
> "kwalters" <[email hidden]> wrote in message
> news:[email hidden]...
>> Have an older steel frame with adjusting screws in each dropout.
>> Just what do these do? Compensate for misaligned dropouts? Allow
>> the wheelbase to be shortened/lengthened? Both former and latter?
>>
>> If I take them out, do I weaken the dropouts, since each dropout

will

Quoted message said:

Quoted message said:

Quoted message said:

>> have a hole thru it fore and aft?
>>
>> Thanks. Ken
>>
> As several others have noted, it makes no difference strength wise

if

Quoted message said:

Quoted message said:

you

Quoted message said:

> have the screws in or not.
>
> The screws serve a number of purposes.
>
> In the late 1980s Shimano set the standard for location of the rear
> derailleur gear hanger bolt hole relative to the hub axle. Prior to

that

Quoted message said:

> there was no standard and this created some problems with index

shifting.

Quoted message said:

> One of the first reasons for the adjustment screws was to aid in
> reinstalling rear wheels to quickly position them between the

chainstays

Quoted message said:

> and locate them above the derailleur for the proper chain gap.
>
> A lot of bike frames were pretty crudely made and differences in

chainstay

Quoted message said:

> length of up to a 1/4" (6mm) was not uncommon. On a lot of older
> derailleurs the chain gap - the distance between the jockey pulley

and

Quoted message said:

Quoted message said:

the

Quoted message said:

> sprockets - was critical for good shifting.
>
> Suntour and later Shimano put adjusting screws on their derailleurs

( the

Quoted message said:

> "B" dimension that Peter mentioned ) for correcting this distance

but

Quoted message said:

Quoted message said:

Quoted message said:

> positioning the wheel forward or back was the only way to adjust the

chain

Quoted message said:

> gap with derailleurs based on Campy's 1960s Record design which many
> makers copied.
>
> On some older frames with short Chainstays moving the wheel back or
> forward was the only way to correct for chain length problems.
>
> One other thing, on a lot of bikes you could adjust the head tube

angle by

Quoted message said:

> a degree or so by moving the rear wheel position. It's questionable
> whether this was a design function or just a poorly built frame.
>
> I've seen older bike that you could change the head tube angle from

72? to

Quoted message said:

> 75? with the old, long Campy 1010 rear dropouts. I've heard tell

that

Quoted message said:

Quoted message said:

you

Quoted message said:

> could use the same bike for criterium and road racing.
>
> The right adjusting screw can help a little in preventing wheel

suck -

Quoted message said:

Quoted message said:

Quoted message said:

> where the wheel shifts and rubs on the left chainstay usually from

honking

Quoted message said:

> or sprinting.
>
> The first generation? of Suntour dropouts with a derailleur hanger

and

Quoted message said:

Quoted message said:

Quoted message said:

> adjusting screws had a propensity to break off at the adjusting

screw

Quoted message said:

Quoted message said:

Quoted message said:

> hole. These were the dropouts that had a wider attachment point for

the

Quoted message said:

> seatstays. They were probably made from a hardened low strength

steel.

Quoted message said:

Quoted message said:

Quoted message said:

"hardened low strength steel"??? that's an oxymoron. more likely

they

Quoted message said:

Quoted message said:

Quoted message said:

were cast or just plain low strength.

They could have been made of case hardened 1018 low carbon steel FOOL!

joke presumably?

The lower priced Swedish made Crescents came with Suntour dropouts (DB531
tubing, Nervex lugs, racing geometry). We sold a number of these and they
were the most common bike that I saw with broken rear dropouts - usually
the left one, broken off at the adjuster screw hole.

The surface of these dropouts was hard, the serrations on the lock nuts
and QRs didn't dig in very much. This could have contributed to wheel
suck.

Campy and Simplex dropouts would bend before breaking and it was usually
the right side from the derailleur running into the wheel.

My thinking was that Suntour intentionally made these hard to prevent the
serrations from digging in. There wasn't much sport cycling in Japan at
the time. Most people rode 50 Lb. black, rusted out rod brake beasts for
basic transportation.

Keirin track racing was popular but it's a sport in the sense that
thoroughbred horse racing is a sport. The main raison d'être for Keirin
racing is parimutuel betting - gambling!

The Keirin jockeys er riders were treated more like thoroughbred horses
than athletes. You can say the same for a lot of other sports but Keirin
racing in Japan was no different than going to the track and throwing some
money at a nag.

For this reason, Japanese bikes and components in the early 1970s left a
lot to be desired. Suntour rear derailleurs and later Shimano derailleurs
had a leg up in performance over European products but the Japanese didn't
use many of their sport cycling products at home. Their bikes and
components were made for export and built to the specs of the importers in
the US and Europe.

Chas.