Purpose of the adjusting screws on droupouts

[Paul McKnab]

On a Merckx steel frame there are two screws built into rear dropouts of the frame that adjust how
far in the rear axle will travel when inserted. I know that the screws can be used to adjust the
wheel's left/right positioning so that the wheel is true with the frame. Here is the question: the
screws can also be used to determine how far in the wheel/axle slides. What determines that correct
distance? How far in is too far in and how would I know?

 

[Qui Si Parla Ca]

Paul-<< Here is the question: the screws can also be used to determine how far in the wheel/axle
slides. What determines that correct distance? How far in is too far in and how would I know?

The guy that taught me said to have the rear wheel axle in line with the seat stays, so that's what
I do on horizontal dropouts with adjusting screws.

It really doesn't make a huge difference tho, particularly with rear ders with b limit screws.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Jobst Brandt]

Paul McKnab writes:

> On a Merckx steel frame there are two screws built into rear dropouts of the frame that adjust how
> far in the rear axle will travel when inserted. I know that the screws can be used to adjust the
> wheel's left/right positioning so that the wheel is true with the frame. Here is the question: the
> screws can also be used to determine how far in the wheel/axle slides. What determines that
> correct distance? How far in is too far in and how would I know?

It was these screws that got me to introduce the vertical dropout to Cino Cinelli and he
subsequently to Tullio Campagnolo. Those screws were leftovers from fixed gear riding that the old
timers felt was essential to early season training, never thinking that they were doing this because
derailleurs were so clumsey and unreliable. By the time the Campagnolo Gran Sport came along the
horizontal dropout was an anacronism but it would not go away because there were still a bunch of
old timers who swore by them. If we did it, it must have been right.

The longitudinal dropout also was a major cause of Campagnolo axle failures because the jam nut is
unsupported in the fore and aft or chain tension direction. Chain tension is about a four times
greater force than rider weight because it has about a 2:1 ratio at the crank and is concentrated on
one side of the axle. Those dropouts bugged me from the first day I worked with them. I was glad to
discover vertical dropouts on Diamant bicycles at the 1960 Olympics. That was the end of axle
adjusting screws for me.

Jobst Brandt [email protected] Palo Alto CA

 

[Sheldon Brown]

Paul McKnab wrote:
> On a Merckx steel frame there are two screws built into rear dropouts of the frame that
> adjust how far in the rear axle will travel when inserted. I know that the screws can be
> used to adjust the wheel's left/right positioning so that the wheel is true with the frame.
> Here is the question: the screws can also be used to determine how far in the wheel/axle
> slides. What determines that correct distance? How far in is too far in and how would I
> know?

The screws allow for quick wheel changes, because you can set them for where you like the axle to
be, and the wheel will stop there when you install it.

The long dropout slots permit you to vary the effective chainstay length. Some people have the
belief that there's some virtue in short chainstays, and these folks can move the wheel all the way
forward. This was quite fashionable for a while.

I prefer to move the wheel farther back, partly because longer "effective" chainstays give a
slightly more comfortable ride, partly because they reduce chain angle when the chainline is
sub-optimal, and partly to get more chain wrap.

For older rear derailers that lacked a "B-tension" or similar adjustment, fiddling with the axle
position in the dropout would sometimes make a difference in the maximum rear sprocket size you
could use, and/or, in the shifting performance.

Sheldon "And They're Great For Fixed-Gear Use" Brown
+------------------------------------------------+
| If you don't want your message to get to me, |
| insert **NO-SPAM** into my email address. |
+------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

 

[Erik Brooks]

>Here is the question: the screws can also be used to determine how far in the wheel/axle slides.
>What determines that correct distance? How far in is too far in and how would I know?

6 months ago, I swapped RDs on an old bike of mine that had those screws. I decided to just take
them out. Doing that lengthened my wheelbase by a probably imperceptible amt, and has no downsides
that I've discovered.

BTW, I don't know if this is true, but I seem to recall hearing that one purpose of those was to
allow the framebuilder to be less precise during frame assembly and then adjust away any
misalignment.

Erik

 

[Matt O'Toole]

"Sheldon Brown" <[email protected]> wrote in message
news:[email protected]...

> Paul McKnab wrote:
> > On a Merckx steel frame there are two screws built
into rear dropouts
> > of the frame that adjust how far in the rear axle will
travel when inserted.
> > I know that the screws can be used to adjust the wheel's
left/right
> > positioning so that the wheel is true with the frame.
Here is the question:
> > the screws can also be used to determine how far in the
wheel/axle slides.
> > What determines that correct distance? How far in is too
far in and how
> > would I know?
>
> The screws allow for quick wheel changes, because you can
set them for
> where you like the axle to be, and the wheel will stop
there when you
> install it.

Vertical dropouts are even quicker. And there are no screws to bend or break.

> The long dropout slots permit you to vary the effective
chainstay
> length. Some people have the belief that there's some
virtue in short
> chainstays, and these folks can move the wheel all the way
forward.
> This was quite fashionable for a while.

It still is, seeing all those bikes whose rear tires are practically touching their seat tubes.

> I prefer to move the wheel farther back, partly because
longer
> "effective" chainstays give a slightly more comfortable
ride,

I'd rather just have decent length chainstays.

> partly because they reduce chain angle when the chainline is
sub-optimal, and
> partly to get more chain wrap.
>
> For older rear derailers that lacked a "B-tension" or
similar
> adjustment, fiddling with the axle position in the dropout
would
> sometimes make a difference in the maximum rear sprocket
size you could
> use, and/or, in the shifting performance.

I forgot all about this stuff. But since it's not a problem anymore, we don't need those stupid
non-vertical dropouts. Even more stupid are the half-assed, diagonal slots for those who just can't
go "cold turkey". I wish bike makers would just go vertical and be done with it.

> Sheldon "And They're Great For Fixed-Gear Use" Brown

...and internal gear hubs too, but there are still plenty of old frames around for such projects.

If I buy a brand new bike with a modern drivetrain and Ergo/STI, the chances are about zero that I
will ever make it into a fixed gear or hub geared bike. So gimme some easy to use, sturdy,
lightweight, elegant, vertical dropouts.

Matt O.

 

[DiabloScott]

So gimme some easy to use, sturdy,
lightweight, elegant, vertical dropouts.

Matt O. [/B]

That face backwards.

 

[Fred Clydesdale]

In article <[email protected]>, [email protected] wrote:

> It was these screws that got me to introduce the vertical dropout to Cino Cinelli and he
> subsequently to Tullio Campagnolo. Those screws were leftovers from fixed gear riding that the old
> timers felt was

if only you could have stopped them from introducing ergo too, we'd all be much happier. mmmm,
vertical dropouts and 120mm OLN spacing. that's good eatin'. and good engineering too!

 

[A Muzi]

"Paul McKnab" <[email protected]> wrote in message news:[email protected]...
> On a Merckx steel frame there are two screws built into rear
dropouts
> of the frame that adjust how far in the rear axle will travel when
inserted.
> I know that the screws can be used to adjust the wheel's left/right positioning so that the wheel
> is true with the frame. Here is the
question:
> the screws can also be used to determine how far in the wheel/axle slides. What determines that
> correct distance? How far in is too far in and how would I know?

Ensure the screws turn easily in the frame and thoroughly lubricate them . They are notorious for
rusting in place. Hold the outside cap securely and turn the screw into it to lock them together.
From here on out you can adjust them with your fingers.

Run the screws in three or four turns from the farthest back. Install the wheel, ensuring it is
centered. Run the screws snug against the axle. Now you can just pull the wheel back to the stops
whenever you install it.

At one time, we used the adjusters to change the position of the derailleur's relationship to the
sprockets. Please see: http://www.yellowjersey.org/sisend.html

which shows you where to place the wheel in relation to the derailleur for best index shifting.

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

 

[Ant]

"Paul McKnab" <[email protected]> wrote in message news:<[email protected]>...
> On a Merckx steel frame there are two screws built into rear dropouts of the frame that adjust how
> far in the rear axle will travel when inserted. I know that the screws can be used to adjust the
> wheel's left/right positioning so that the wheel is true with the frame. Here is the question: the
> screws can also be used to determine how far in the wheel/axle slides. What determines that
> correct distance? How far in is too far in and how would I know?

i read, in my early years of bike maintenance (oh wait, im still in my early years) that with hor
drops you should put the axle towards the front of the drops for indexed ders, and centered in the
drops for friction. this from langley's 'complete' book of maintenance, which i bought back when i
thought that it _was_ complete.

maybe this ties in with what others were saying abotu shifting performance. it might be useful as a
starting point for others feeling uncertain. i dont know the theory, and cant say whether its true,
false, or inconsequential.

(and i like horizontal dropouts a lot

anthony

 

[Benjamin Weiner]

Matt O'Toole <[email protected]> wrote:

> > Sheldon "And They're Great For Fixed-Gear Use" Brown

> ...and internal gear hubs too, but there are still plenty of old frames around for such projects.

> If I buy a brand new bike with a modern drivetrain and Ergo/STI, the chances are about zero that I
> will ever make it into a fixed gear or hub geared bike. So gimme some easy to use, sturdy,
> lightweight, elegant, vertical dropouts.

Vertical dropouts also make the wheel easier to extract when fendered, which can be annoying even on
a bike with decent length chainstays.

But as Andrew Muzi mentioned a little while ago, there is a catch. Last week's new thing was making
fixed gear bikes out of old road frames, and there are plenty of 700c or 27" donors with horizontal
dropouts for that, at all levels of quality and fairly minimal cost. You could get yourself fixed
(so to speak) for the cost of a track cog (and a wheel if you wanted to be really pro).

OTOH, this week's new thing is singlespeed mountain bikes. And vertical dropouts appeared pretty
early on mountain bikes. So there aren't a lot of good 26" donor frames. Arguably this is good for
builders, making new frames or adding track ends, but it ain't the same easy recycling. Sure, you
can use a derailleur or chichi chain tensioner, but that is bogus.

I eventually came up with a Specialized Hardrock with a filled-in horizontal end - a bit of filing
cleared the axle slot, rendering it fully singlespeedable. The disadvantages are older, slacker
geometry and only 3 tubes CrMo, so I have a heavy singlespeed, go figure. Not everyone has my
patience to find such a frame.

BTW, I'm sure whoever bought this bike never imagined someone would one day want to take all the
gears off. OTOH, removing the Rapidfire Minus push-push shifters was the best thing anyone ever
did for it.

 

[Qui Si Parla Ca]

Jobst-<< It was these screws that got me to introduce the vertical dropout to Cino Cinelli and he
subsequently to Tullio Campagnolo.

But wasn't the reason for some of the first horizontal dropouts Campagnolo's P-R 'rear cog
changing 'system'?

Not a real rear der but the first to be able to move the chain on a multiple cog setup.

Vertical dropouts are nice but horizontal aren't the problem they are implied to be in this thread.
Like Italian BBs, if aligned and used properly, work everyday w/o problem.

I for one, like the ability to someday use the frameset for a fixed gear.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Robin Hubert]

"Benjamin Weiner" <[email protected]> wrote in message news:[email protected]...
> Matt O'Toole <[email protected]> wrote:
>
> > > Sheldon "And They're Great For Fixed-Gear Use" Brown
>
> > ...and internal gear hubs too, but there are still plenty of old frames around for such
> > projects.
>
> > If I buy a brand new bike with a modern drivetrain and Ergo/STI, the chances are about zero that
> > I will ever make it into a fixed gear or hub geared bike. So gimme some easy to use, sturdy,
> > lightweight, elegant, vertical dropouts.
>
> Vertical dropouts also make the wheel easier to extract when fendered, which can be annoying even
> on a bike with decent length chainstays.
>
> But as Andrew Muzi mentioned a little while ago, there is a catch. Last week's new thing was
> making fixed gear bikes out of old road frames, and there are plenty of 700c or 27" donors with
> horizontal dropouts for that, at all levels of quality and fairly minimal cost. You could get
> yourself fixed (so to speak) for the cost of a track cog (and a wheel if you wanted to be
> really pro).
>
> OTOH, this week's new thing is singlespeed mountain bikes. And vertical dropouts appeared pretty
> early on mountain bikes. So there aren't a lot of good 26" donor frames. Arguably this is good for
> builders, making new frames or adding track ends, but it ain't the same easy recycling. Sure, you
> can use a derailleur or chichi chain tensioner, but that is bogus.
>
> I eventually came up with a Specialized Hardrock with a filled-in horizontal end - a bit of filing
> cleared the axle slot, rendering it fully singlespeedable. The disadvantages are older, slacker
> geometry and only 3 tubes CrMo, so I have a heavy singlespeed, go figure. Not everyone has my
> patience to find such a frame.
>
> BTW, I'm sure whoever bought this bike never imagined someone would one day want to take all the
> gears off. OTOH, removing the Rapidfire Minus push-push shifters was the best thing anyone ever
> did for it.
>

You can also have a local frame builder braze in some horizontals. This is usually inexpensive.

--
Robin Hubert <[email protected]

 

[G.Daniels]

A touring or commuters load on the rear rack increases the fourfold pressure on the rear
axle/bearings/cones gradually pulling the assembley out of whack and into the wear zone blowing the
mech's intial dead on bearing/cone/axle adjustment within a few loaded miles. The loaded rear axle
pullout gives considerable wobble in the real world of self maintainence not adjust and send it oput
of the shop. The rider mounts the wheel after a flat/broken spoke not readjust the bearings and bill
unless you're obsessive. You know like three times a rear is enough already. The general looseness
and AMUZI's: "Run the screws in three or four turns from the farthest back. Install the wheel,
ensuring it is centered. Run the screws snug against the axle. Now you can just pull the wheel back
to the stops whenever you install it." A good approach that doesn't account for the wrestleing match
I wind up with tightening the rear axle nuts on a '87 T-Raleigh as the nuts(given the situation of
periodically slathering the dropouts with linseed for rust protection)(***^##@!!! slide the axle out
of adjustment as I tighten. So far, my technique does not result in a Wood's Bros. manuver. So I
bought(to cut to the chase), an axle stop from 3Hand, beat the frame with a switch, installed the
wheel, marked the spot, loctited the stop and installed everything then let the mess sit to cure.
After several tries at this, it came right. NOW! when the wheel remounts, the moveable worn
bearing/hub/cone/axle tolerants measured off course at the tire not the axle end hahahhja wheee! be
serious. this is a serious discussion stupid. ok Yeah it does.Instead of weaving aroound lika drunk
on glaze',the axle goes down on the stop opposite the deray where once there was only empty ummapped
desolation anomie and rootlessness. Ah! Then with the stop one can begion to set the axle/rim
inplace to the seatpost then the CR/rear deray line if obsessive that day. The stop, to be relevant,
is a fixed screw, and a welcome labor saving device that reduces long term wear plus drive ahead
friction. With the touring/commute load, a stop may reduce the total wear by limiting onesides
potential eliptical wear path movement.

LINSEED STEEL REAR DROPOUTS!!

 

[Sheldon Brown]

Benjamin Weiner wrote:

> Vertical dropouts also make the wheel easier to extract when fendered, which can be annoying even
> on a bike with decent length chainstays.
>
> But as Andrew Muzi mentioned a little while ago, there is a catch. Last week's new thing was
> making fixed gear bikes out of old road frames, and there are plenty of 700c or 27" donors with
> horizontal dropouts for that, at all levels of quality and fairly minimal cost.

Actually, the supply is not as abundant as it was a couple of years ago, and shrinking rapidly.

> OTOH, this week's new thing is singlespeed mountain bikes. And vertical dropouts appeared pretty
> early on mountain bikes. So there aren't a lot of good 26" donor frames. Arguably this is good for
> builders, making new frames or adding track ends, but it ain't the same easy recycling. Sure, you
> can use a derailleur or chichi chain tensioner, but that is bogus.

That's true, but Doug White has come up with a _great_ solution, see:

http://sheldonbrown.com/harris/white-hubs.html

> I eventually came up with a Specialized Hardrock with a filled-in horizontal end - a bit of filing
> cleared the axle slot, rendering it fully singlespeedable. The disadvantages are older, slacker
> geometry and only 3 tubes CrMo, so I have a heavy singlespeed, go figure. Not everyone has my
> patience to find such a frame.

I don't think I'd agree that the "older, slacker geometry" is a disadvantage! Those early MTBs had a
very nice, stable handling, and the only disadvantage of the geometry was poor traction in very
steep off-road climbing.

It is unfortunate that these early MTB frames were generally rather heavy and overbuilt, because the
builders of the day had exaggerated ideas about how stressful mountain biking was to equipment.

Sheldon "Excelsior!" Brown +----------------------------------------+
| The art of being wise is the art of | knowing what to overlook. | --William James |
+----------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

 

[Matt O'Toole]

"Benjamin Weiner" <[email protected]> wrote in message news:[email protected]...

> But as Andrew Muzi mentioned a little while ago, there is
a catch.
> Last week's new thing was making fixed gear bikes out of
old road
> frames, and there are plenty of 700c or 27" donors with
horizontal
> dropouts for that, at all levels of quality and fairly
minimal cost.
> You could get yourself fixed (so to speak) for the cost of
a track
> cog (and a wheel if you wanted to be really pro).
>
> OTOH, this week's new thing is singlespeed mountain bikes.
And
> vertical dropouts appeared pretty early on mountain bikes.
So
> there aren't a lot of good 26" donor frames. Arguably
this is
> good for builders, making new frames or adding track ends,
but
> it ain't the same easy recycling. Sure, you can use a
derailleur
> or chichi chain tensioner, but that is bogus.
>
> I eventually came up with a Specialized Hardrock with a
filled-in
> horizontal end - a bit of filing cleared the axle slot,
rendering it
> fully singlespeedable.

One could just buy one of these...

http://www.sheldonbrown.com/harris/redline-monocog.html

...probably for a lot less than many people wind up spending on such projects.

Matt O.

 

[Mike S.]

> > But as Andrew Muzi mentioned a little while ago, there is
> a catch.
> > Last week's new thing was making fixed gear bikes out of
> old road
> > frames, and there are plenty of 700c or 27" donors with
> horizontal
> > dropouts for that, at all levels of quality and fairly
> minimal cost.
> > You could get yourself fixed (so to speak) for the cost of
> a track
> > cog (and a wheel if you wanted to be really pro).
> >
> > OTOH, this week's new thing is singlespeed mountain bikes.
> And
> > vertical dropouts appeared pretty early on mountain bikes.
> So
> > there aren't a lot of good 26" donor frames. Arguably
> this is
> > good for builders, making new frames or adding track ends,
> but
> > it ain't the same easy recycling. Sure, you can use a
> derailleur
> > or chichi chain tensioner, but that is bogus.
> >
> > I eventually came up with a Specialized Hardrock with a
> filled-in
> > horizontal end - a bit of filing cleared the axle slot,
> rendering it
> > fully singlespeedable.
>
> One could just buy one of these...
>
> http://www.sheldonbrown.com/harris/redline-monocog.html
>
> ...probably for a lot less than many people wind up spending on such projects.
>
> Matt O.
>
>
Yeah, but the mechanic in me likes to tinker around, so I'd rather make something work than buy
something pre-built.

Mike

 

[Benjamin Weiner]

Sheldon Brown <[email protected]> wrote:
> Benjamin Weiner wrote:

> > Last week's new thing was making fixed gear bikes out of old road frames, and there are plenty
> > of 700c or 27" donors with horizontal dropouts for that, at all levels of quality and fairly
> > minimal cost.

> Actually, the supply is not as abundant as it was a couple of years ago, and shrinking rapidly.

Really? Tell us the details. I defer to your extensive experience in this field, and know little
about the retail side, but it sure seems like there are a lot of 70s-80s fixable road bikes out
there, like competently made Japanese steel chromo bikes, or 1980s steel Treks. There can't possibly
be enough bike messengers to soak them all up. Higher end frames are rarer of course, but seems to
me that most old steel frames short of collectible ones (Colnagos, etc) are more or less
inexpensive, certainly at swap meets, perhaps even on ebay.

> > OTOH, this week's new thing is singlespeed mountain bikes. And vertical dropouts appeared pretty
> > early on mountain bikes. ..

> http://sheldonbrown.com/harris/white-hubs.html

The White hub is very neat looking, though probably as expensive as having new ends brazed in a
steel frame (which is not to call it overpriced).

> I don't think I'd agree that the "older, slacker geometry" is a disadvantage! Those early MTBs had
> a very nice, stable handling, and the only disadvantage of the geometry was poor traction in very
> steep off-road climbing.

I dunno, this one doesn't feel too bad but I once had a Diamondback with 68 deg head tube and long
rake that felt slow to turn, and had an amazingly long wheelbase. Also with these old frames, you
can't really put a suspension fork on (1" headtube, and makes the HT even slacker). With Rivendell's
turn to road oriented bikes, fans seem to have forgotten that a major Bridgestone claim to fame was
building nice-handling MTBs with moderate length chainstays and 71 degree headtubes.

> It is unfortunate that these early MTB frames were generally rather heavy and overbuilt, because
> the builders of the day had exaggerated ideas about how stressful mountain biking was to
> equipment.

Yes. OTOH, it seems like people on Usenet are always complaining about breaking today's MTB
stuff, aluminum frames especially. (I know, the vast majority of bikes don't get ridden hard and
don't break.)

Ben

 

[Ryan Cousineau]

In article <[email protected]>, Benjamin Weiner <[email protected]> wrote:

> Sheldon Brown <[email protected]> wrote:
> > Benjamin Weiner wrote:

> > It is unfortunate that these early MTB frames were generally rather heavy and overbuilt, because
> > the builders of the day had exaggerated ideas about how stressful mountain biking was to
> > equipment.
>
> Yes. OTOH, it seems like people on Usenet are always complaining about breaking today's MTB
> stuff, aluminum frames especially. (I know, the vast majority of bikes don't get ridden hard and
> don't break.)

Totally different purposes. Those early frames were designed for what we would now call
cross-country riding. In most circumstances, the frame-breakers are not riding hard, they're
free-riding or downhilling, in other words doing big drops. Even 8 inches of suspension can't absorb
every drop.

--
Ryan Cousineau, [email protected] http://www.sfu.ca/~rcousine President, Fabrizio Mazzoleni Fan Club

 

[Sheldon Brown]

I wrote:

>>I don't think I'd agree that the "older, slacker geometry" is a disadvantage! Those early MTBs had
>>a very nice, stable handling, and the only disadvantage of the geometry was poor traction in very
>>steep off-road climbing.

Quoth Benjamin Weiner:

> I dunno, this one doesn't feel too bad but I once had a Diamondback with 68 deg head tube and long
> rake that felt slow to turn, and had an amazingly long wheelbase.

Yeah! ;-) Long wheelbase is sometimes a Good Thing!

> Also with these old frames, you can't really put a suspension fork on (1" headtube, and makes the
> HT even slacker).

With those frames, a sus fork would be gilding the lily.

I'm not maintaining that this is a great design for technical offroad use, but those old "California
cruiser" mountain frames were _super_ for heavily-loaded touring.

>>It is unfortunate that these early MTB frames were generally rather heavy and overbuilt, because
>>the builders of the day had exaggerated ideas about how stressful mountain biking was to
>>equipment.
>
> Yes. OTOH, it seems like people on Usenet are always complaining about breaking today's MTB
> stuff, aluminum frames especially. (I know, the vast majority of bikes don't get ridden hard and
> don't break.)

Thesis. Antithesis. Synthesis.

Sheldon "Dialectic" Brown +--------------------------------------------+
| In order to understand recursion, | first, you have to understand recursion. |
+--------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com