Question on rear dropout adjusting screws

[A Muzi]

kwalters wrote:
> 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?

Convenience only.
As with the conical springs on your skewer, makes wheel changes a
split-second faster. Throw out the springs and those little screws with
impunity - and save grams!!

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

 

[A Muzi]

datakoll wrote:
> 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

Jobst does this 'upside down' (bike upright) and both of us can manage
it without frame screws. Face it, they are vestigial if you are not
racing in a supported event.

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

 

[A Muzi]

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

> "David L. Johnson" <[email protected]> wrote:
>> 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.

[email protected] wrote:
> 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=wQ...ts=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.

Having reworked a large number of broken bicycle frame ends, I don't
believe it matters.
(I'm blissfully ignorant of wood in its entirety).

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

 

[A Muzi]

> "kwalters" <[email protected]> wrote:
>> 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?

* * Chas wrote:
> 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.

That's an odd assessment.
I've built with Suntour's forged ends and do quite a bit of frame
repair. IMHO the forged ends of the era (1960s~1970s) are high quality
and much more ductile, hence forgiving, than the later brittle cast SCM
ends which replaced them. Cast ends are cleaner as delivered and take
less prep time but don't move much before cracking when things go awry.
Suntour, Campagnolo and Shimano forged ends are all similar and of good
quality in my experience.

Pressed 5mm ends are another thing altogether.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[* * Chas]

"A Muzi" <[email protected]> wrote in message
news:[email protected]...
> kwalters wrote:
> > 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?
>
> Convenience only.
> As with the conical springs on your skewer, makes wheel changes a
> split-second faster. Throw out the springs and those little screws with
> impunity - and save grams!!
>
> --
> Andrew Muzi
> www.yellowjersey.org
> Open every day since 1 April, 1971

But they don't look as retro.

Chas.

 

[* * Chas]

"A Muzi" <[email protected]> wrote in message
news:[email protected]...
> > "kwalters" <[email protected]> wrote:
> >> 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?
>
> * * Chas wrote:
> > 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.
>
> That's an odd assessment.
> I've built with Suntour's forged ends and do quite a bit of frame
> repair. IMHO the forged ends of the era (1960s~1970s) are high quality
> and much more ductile, hence forgiving, than the later brittle cast SCM
> ends which replaced them. Cast ends are cleaner as delivered and take
> less prep time but don't move much before cracking when things go awry.
> Suntour, Campagnolo and Shimano forged ends are all similar and of good
> quality in my experience.
>
> Pressed 5mm ends are another thing altogether.
> --
> Andrew Muzi
> www.yellowjersey.org
> Open every day since 1 April, 1971

The Suntour dropouts from the early 1970s with the wider seat stay
attachment points were really hard on the surface. I removed the fender
eyelets off of at least one set and they were almost too hard to file. I
had to use a grinder. It's hard to say whether they were cast or forged -
I don't remember.

Most of the forged dropouts were made of much tougher steel. This is a
moot point since most bikes today come with much better designed dropouts.

Chas.