fixie frames

Quoted message said:

Quoted message said:

Quoted message said:

I'd like to build a fixed gear bike, but only currently have an old MTB frame available. Is this
ok to use, or should I wait until I can find a road frame to invest in?

Quoted message said:

Quoted message said:

Peter Chisholm : Look for a cheapie road frame with horizontal dropouts...

Matt J said:

Given that one cannot use a conventional derailer-type chain tensioner for a fixie because
backpedaling would rip it off. I think I saw on a tandem one time, as a chain tensioner for the
sync chain, a chainring (with diameter greater than the vertical distance between chain runs)
suspended between the upper/lower chain runs. As the top run went forward, the rear run went
backward, and the ring stayed in the same place. Could such a contraption be used as a "chain
tensioner" on a fixie w/ vertical dropouts?

Wouldn't actually do anything and you'd have to cut either the frame or the ring.

What exactly do you think that chainring in midair was doing? Do you think they actually kept a
bunch of rings to swap in one-tooth increments instead of simply moving the tandem's chain adjuster?
One tooth difference on a chainring is a pretty coarse 'adjustment'.

Moving the axle is the best way to tension a chain, IMHO, but that doesn't stop guys from seeking
complexity.

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

Matt J said:

Given that one cannot use a conventional derailer-type chain tensioner for a fixie because
backpedaling would rip it off. I think I saw on a tandem one time, as a chain tensioner for the
sync chain, a chainring (with diameter greater than the vertical distance between chain runs)
suspended between the upper/lower chain runs. As the top run went forward, the rear run went
backward, and the ring stayed in the same place. Could such a contraption be used as a "chain
tensioner" on a fixie w/ vertical dropouts?

The "phantom chainring" technique is well known for use on homebuilt tandems, I've done it myself,
but won't work on a conventional single frame 'cause the chainstay is in the way of where the
phantom chainring would need to go.

Sheldon "Nice Try" Brown +-------------------------------------------------------+
| ...what is hailed as a new style or a new school | in literature often consists of doing as a
| novelty | what a Victorian did long ago as a joke. | -- G.K. Chesterton |
+-------------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

A Muzi said:

Quoted message said:

Given that one cannot use a conventional derailer-type chain tensioner for a fixie because
backpedaling would rip it off. I think I saw on a tandem one time, as a chain tensioner for the
sync chain, a chainring (with diameter greater than the vertical distance between chain runs)
suspended between the upper/lower chain runs. As the top run went forward, the rear run went
backward, and the ring stayed in the same place. Could such a contraption be used as a "chain
tensioner" on a fixie w/ vertical dropouts?

Wouldn't actually do anything and you'd have to cut either the frame or the ring.

No, it would do something. This trick is common for homemade tandems; it's called a "phantom
chainring". Problem is that in this case the ring would have to go around the chainstay. Maybe you
could cut the ring, slide it on, then somehow secure the cut area so it would hold up. You'd have to
do this to a number of chainrings, though, to swap them in/out to adjust the tension.

Why not just get a bunch of chainrings, and a bunch of cogs, and swap them in and out until you find
one where the tension is correct? Limits your gearing, but there is no reason why it would not work.

Quoted message said:

What exactly do you think that chainring in midair was doing? Do you think they actually kept a
bunch of rings to swap in one-tooth increments instead of simply moving the tandem's chain
adjuster? One tooth difference on a chainring is a pretty coarse 'adjustment'.

Well, actually, it's for tandems without an eccentric. One tooth is not that coarse and adjustment.
One-tooth difference in a sprocket or chainring amounts to 1/8" fore-aft adjustment of the axle. (one-
half tooth (1/4"😉 for the half circle of sprocket the chain sits on, and that
1/4" is evenly split between top and bottom runs of chain.

--

David L. Johnson

__o | It is a scientifically proven fact that a mid life crisis can _`\(,_ | only be cured by
something racy and Italian. Bianchis and (_)/ (_) | Colnagos are a lot cheaper than Maserattis
and Ferraris. -- Glenn Davies

Quoted message said:

On Sun, 28 Dec 2003 20:23:34 +0000, A Muzi wrote:

blah blah blah about a floating chainring in a tandem timing chain or similiar in a single -snip-

David L. Johnson said:

Well, actually, it's for tandems without an eccentric. One tooth is not that coarse and
adjustment. One-tooth difference in a sprocket or chainring amounts to 1/8" fore-aft adjustment of
the axle. (one-half tooth (1/4"😉 for the half circle of sprocket the chain sits on, and that
1/4" is evenly split between top and bottom runs of chain.

Well, that's a difference of opinion, I guess. Having some experience with a bike we used to
maintain, the rider asked us to swap 47 to 48 and then a new chain with the 47 again for a couple of
years. Not all that great IMHO but I suppose you make a good point that if tandem builder left no
other provision it's one solution. What tandem has no adjustment?

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

A Muzi said:

then a new chain with the 47 again for a couple of years. Not all that great IMHO but I suppose
you make a good point that if tandem builder left no other provision it's one solution. What
tandem has no adjustment?

Someone who welded two single bikes together, usually.

--

David L. Johnson

__o | When you are up to your ass in alligators, it's hard to remember _`\(,_ | that your initial
objective was to drain the swamp. -- LBJ (_)/ (_) |

A Muzi wrote: ....

Quoted message said:

Moving the axle is the best way to tension a chain, IMHO, but that doesn't stop guys from seeking
complexity.

Maybe I am missing something here, but doesn't moving the axle back and forth in a set of horizontal
fork ends lead to the possibility of having the rear wheel out of alignment with the frame (i.e. the
two are not parallel)? This would not occur with the use of either an eccentric BB or the ENO hub
(assuming the frame is straight).

Tom Sherman – Close to 41½ N, 90½ W

David L. Johnson said:

A Muzi said:

Quoted message said:

Given that one cannot use a conventional derailer-type chain tensioner for a fixie because
backpedaling would rip it off. I think I saw on a tandem one time, as a chain tensioner for the
sync chain, a chainring (with diameter greater than the vertical distance between chain runs)
suspended between the upper/lower chain runs. As the top run went forward, the rear run went
backward, and the ring stayed in the same place. Could such a contraption be used as a "chain
tensioner" on a fixie w/ vertical dropouts?

Wouldn't actually do anything and you'd have to cut either the frame or the ring.

No, it would do something. This trick is common for homemade tandems; it's called a "phantom
chainring". Problem is that in this case the ring would have to go around the chainstay. Maybe you
could cut the ring, slide it on, then somehow secure the cut area so it would hold up. You'd have
to do this to a number of chainrings, though, to swap them in/out to adjust the tension.

Why not just get a bunch of chainrings, and a bunch of cogs, and swap them in and out until you
find one where the tension is correct? Limits your gearing, but there is no reason why it would
not work.

Quoted message said:

What exactly do you think that chainring in midair was doing? Do you think they actually kept a
bunch of rings to swap in one-tooth increments instead of simply moving the tandem's chain
adjuster? One tooth difference on a chainring is a pretty coarse 'adjustment'.

Well, actually, it's for tandems without an eccentric. One tooth is not that coarse and adjustment.
One-tooth difference in a sprocket or chainring amounts to 1/8" fore-aft adjustment of the axle.
(one-half tooth (1/4"😉 for the half circle of sprocket the chain sits on, and that
1/4" is evenly split between top and bottom runs of chain.

Without delving too much into trigonometry, one tooth increments on the floating phantom chainring
povide even finer adjustment than that, because you're spreading the chain runs apart by 1/2"
divided by pi each time, and this change is to the shortest side of a very long thin triangle. A
quick calculation suggests an adjustment equivalent to about .002" axle movement. For comparison, a
typical chain tug gives about .032" axle movement for each full turn of the screw. I adjust my chain
tugs 1/4 turn at a time, so I reckon you need axle position adjustment in increments of about .008"
(0.2mm) for optimum tension. Maybe you can get away with something coarser if you don't mind a lot
of backlash, and I certainly run the chain looser than that on my singlespeed MTB, but for fixed I
like the chain nice and tight with no pedal load. You can get the bottom run distinctly slack with
just hand pressure on the pedal if you start with a little static tension in the chain.

Kinky Cowboy*

*Batteries not included May contain traces of nuts Your milage may vary

Tom Sherman said:

A Muzi wrote: ....

Quoted message said:

Moving the axle is the best way to tension a chain, IMHO, but that doesn't stop guys from seeking
complexity.

Maybe I am missing something here, but doesn't moving the axle back and forth in a set of
horizontal fork ends lead to the possibility of having the rear wheel out of alignment with the
frame (i.e. the two are not parallel)? This would not occur with the use of either an eccentric BB
or the ENO hub (assuming the frame is straight).

Tom Sherman – Close to 41½ N, 90½ W

Yes, but....

An eccentric BB changes the relationship between the three contact points, and the effective
chainstay length/wheelbase, every time you adjust the chain

An eccentric rear hub changes the BB height, effective chainstay length/wheelbase and frame angles
every time you adjust the chain

A horizontal fork end changes the effective chainstay length/wheelbase every time you adjust the
chain. It's very easy to get the wheel in the same plane as the frame, especially if you use chain
tugs on both sides. And hoizontal fork ends, as original equipment, are a much cheaper solution than
either an eccentric BB or an eccentric hub, as well as being more secure (chain tugs lock in your
adjustment, eccentrics rely on friction)

Now, if Identiti would just produce a road frame with their Adjustable Dropout System...

identitibikes.comfmit drjadsOpen ↗
1030506.html

Kinky Cowboy*

*Batteries not included May contain traces of nuts Your milage may vary

Kinky Cowboy said:

Without delving too much into trigonometry, one tooth increments on the floating phantom chainring
povide even finer adjustment than that, because you're spreading the chain runs apart by 1/2"
divided by pi each time, and this change is to the shortest side of a very long thin triangle.

That's true, but actually not all that relevant. The way you adjust tension with a "phantom
chainring" system is by moving the phantom ring closer to one of the working sprockets.

For folks having trouble envisioning how this works, see:

sheldonbrown.comtandem build2.htmlOpen ↗

Sheldon "Phantom" Brown +------------------------------------------+
| To invent, you need a good imagination | and a pile of junk. --Thomas Edison |
+------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-
9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

On Sat, 27 Dec 2003 23:35:45 -0600, A Muzi <[email hidden]> wrote:

(Seatpost diameter is a quick rough guide to

Quoted message said:

frame material)

Could you elucidate please?

--
Scott Johnson "Always with the excuses for small legs. People like you are why they only open the
top half of caskets." -Tommy Bowen

Top Sirloin said:

On Sat, 27 Dec 2003 23:35:45 -0600, A Muzi <[email hidden]> wrote:

(Seatpost diameter is a quick rough guide to

Quoted message said:

frame material)

Could you elucidate please?

25.4mm seatpost = gas pipe (I have one).

26.2mm seatpost = 531 or other decent steel [1].

On the basis that all road tubes have standardised OD because they have to fit standard lugs.

[27] if 531 is silver brazed with a gentle heat so that the seta tube does not go out-of-round it
will take a 27.4mm post without any reaming. Few builders do this.

Sheldon Brown said:

Kinky Cowboy said:

Without delving too much into trigonometry, one tooth increments on the floating phantom
chainring povide even finer adjustment than that, because you're spreading the chain runs apart
by 1/2" divided by pi each time, and this change is to the shortest side of a very long thin
triangle.

That's true, but actually not all that relevant. The way you adjust tension with a "phantom
chainring" system is by moving the phantom ring closer to one of the working sprockets.

For folks having trouble envisioning how this works, see:

sheldonbrown.comtandem build2.htmlOpen ↗

Sheldon "Phantom" Brown

Any mathematicians with more spare time than me can work out whether this is true. I think using a
phantom 1 tooth bigger than the drive rings gives a total change in chain length of less than
.00003" if you move it one inch from halfway between the drive rings!

The illustrations on Sheldon's site show phantom rings (sometimes two) much larger than the drive
rings. These wider angles appear to give more scope for static chain tension adjustment (especially
with the "two phantoms" arrangement), but maybe they also mean the tension goes awry when loaded,
with the top chain run straight and the phantom forced downwards?

They obviously work in practice, and as you can usually get chainrings from your LBS bargain bucket
for about $10 a piece, it's a cheap solution compared with an eccentric BB

Has anybody built an "inverted phantom" by using a pair of derailleur pulleys running on the
outside of the timing chain run, linked by a free floating pair of tie bars? This would give more
chain wrap on the timing rings (negligible advantage) and the timing chain would be running through
a closed loop so it couldn't eject the tensioner over rough ground, which looks possible with
phantom rings. A selection of mounting holes for the pulley axle bolts would give all the
adjustability you could need.

Kinky Cowboy*

*Batteries not included May contain traces of nuts Your milage may vary

Tom Sherman said:

A Muzi wrote: ....

Quoted message said:

Moving the axle is the best way to tension a chain, IMHO, but that doesn't stop guys from seeking
complexity.

Maybe I am missing something here, but doesn't moving the axle back and forth in a set of
horizontal fork ends lead to the possibility of having the rear wheel out of alignment with the
frame (i.e. the two are not parallel)? This would not occur with the use of either an eccentric BB
or the ENO hub (assuming the frame is straight).

Not if you set the little screw adjusters to be the same. Incidentally, a lot of frames with
horizontal dropouts are quite badly built because this adjustment is possible. Vertical dropouts
make framebuilders a bit more careful!

Kinky Cowboy said:

Quoted message said:

Well, actually, it's for tandems without an eccentric. One tooth is not that coarse and
adjustment. One-tooth difference in a sprocket or chainring amounts to 1/8" fore-aft adjustment of
the axle. (one-half tooth (1/4"😉 for the half circle of sprocket the chain sits on, and that
1/4" is evenly split between top and bottom runs of chain.

Without delving too much into trigonometry, one tooth increments on the floating phantom chainring
povide even finer adjustment than that, because you're spreading the chain runs apart by 1/2"
divided by pi each time, and this change is to the shortest side of a very long thin triangle.

Correct. I had dropped consideration of the phantom chainring and was just thinking about swapping
sprockets at that point. Sorry it was not clear.

Quoted message said:

A quick calculation suggests an adjustment equivalent to about .002" axle movement.

To go from a phantom chainring that is just the same size as the left-side rings, to the next tooth
or two up, I'd imagine that it would be even finer than that. The point of tangency would move
0.25/pi" out, on a run of maybe a foot and a half.

Quoted message said:

the chain looser than that on my singlespeed MTB, but for fixed I like the chain nice and tight
with no pedal load. You can get the bottom run distinctly slack with just hand pressure on the
pedal if you start with a little static tension in the chain.

To follow-up on an older, and very weird, thread, you do have to be careful to check the tension at
the tightest point if you are going for that much tension.

On my tandem (vertical dropout, 7-speed internal hub) I was able to swap sprockets and chainrings
around and get a good gear range, and good tension, with no idler. This is on the rear chain; being
a real tandem it does have an eccentric so I can adjust the front chain tension easily.

--

David L. Johnson

__o | There is always an easy solution to every human problem - neat, _`\(,_ | plausible, and
wrong. --H.L. Mencken (_)/ (_) |

In article <[email hidden]>,

Sheldon Brown said:

Ryan Cousineau said:

I have something to show you:

norco.com4hun.jpgOpen ↗

As you can see, a picture of a singlespeed (in this case, the 2003 Norco 4Hun, a hardtail dirt-
jumping bike, sort of a big angry BMX with a suspension fork and disc brakes) with a single-
wheel tensioner (ie not a converted derailleur).

It may not be true on this bike, but it appears that if you could adapt this tensioner design so
that the tensioner still had chainstay clearance when the bottom chain-run came tight, you could
make a tensioner work on a fixed-gear as well.

If it was a spring-loaded tensioner, it would still cause the top run of chain to go slack, and
likely derail.

If it was a rigid tensioner it would have to be ungodly strong to hold up under backpressure.

Quoted message said:

There's a bigger question, though: why does this bike, which has a very skookum rear-facing
horizontal fork ends, need a tensioner?

Hint: Norco couldn't answer that question either, as the 2004 model does not have a tensioner:

norco.com1hun.jpgOpen ↗

That looks more like a BMX/Freestyle bike, that can't decide whatthehell it is s'posed to be, also
featuring a brake rotor and a derailer hanger. If it's s'posed do be a BMX bike, why the rotor? If
it's s'posed to be a freestyle bike for aerial stuff, why the 36 spoke wheels? If it's s'posed to
be a freestyle bike for flatland, why no front brake (though it does have a disk mount in front.

I can explain some of these features. This is indeed meant as a fairly specialized dirt-jumper, but
it's running 24" wheels stock, which is bigger than BMX (it's a now-popular wheel option for certain
freeride and dirt-jump bikes).

The rotor is because this is for doing dirt-jump tricks. It ends up being a big boy's big-air bike,
or a super-duper BMX sized for 6-footers. The 36-spoke wheels are because this bike is designed to
be crashed heavily. No, really. Basically the frame will be relatively heavy, and allow for
reasonable survivability when you blow a dirt jump and have to bail out.

Quoted message said:

The photo seems to show a cantilever boss even with the rim, too high for normal cantilevers, too
low for a U-brake...?

The canti posts you see will accomodate a 26" wheel (the bike may well have screw-in posts and
mounting bosses for either 24" or 26" wheels. How's that for flexibility?)

Quoted message said:

Personally, I don't think that horizontal, adjustable fork ends are a good combination with a rear
disc brake anyway.

Oh? What goes wrong? The rear disc is cable-actuated, and it looks like sliding the wheel in and out
wouldn't be too much trouble.

Quoted message said:

Sheldon "Won't Be Buying One Of Those" Brown

I didn't pick you for a dirt-jumper, offhand. :P

norco.com1hun.htmOpen ↗

This is a very specialized bike, obviously not the hot seller in the line. It's a very adaptable
frame: think of it as a severe-conditions Karate Monkey. It can do 24" or 26" wheels, The hub and
fork are fitted for a front disc, the geometry will accomodate a medium-travel suspension fork, and
the close observer will see that it even has a derailleur hole right under the horizontal fork ends.

The BB is BMX standard: in a lot of ways this is meant as a hybrid of a BMX freestyle bike and a
freeride mountain bike. It doesn't have to be for everyone (it's not for me, either. I'd get a nice
5" trailbike with one of those pretty new stable-platform shocks for my next MTB, as a complement to
my do-everything hardtail).

Share & Enjoy,

PS: I have a question for you about Nishiki.

sheldonbrown.comjapan.htmlOpen ↗

I have a mid/late-80s Nishiki mountain bike, a very respectable cro-moly frame of the era with the
usual low-end bike-shop bike features (friction shifting, Shimano "RS" group, off-brand brakes and
shifters). But it has a sticker on it describing it as "Designed by Norco".

And indeed, at the time I could have bought the same frame as a Norco-branded bike or the now-
obscure "Fiori" brand, which appears to have been another badge-engineering exercise by Norco, this
time to give their bikes an Italian flavour (I recall that the Fioris came in more frou-frou
pastels, like the green-yellow-pink triple-fade job my co-worker uses as a commuter).

Do you know anything about this Norco/Nishiki relationship? Did Norco own the brand for a
while? Anyone?

Oh, and one correction for you: you have Mikado listed as a Japanese make. I can only assume the
makers were fans of Gilbert and Sullivan, as this is a Canadian brand, still based in Quebec as far
as I know, but now part of the Procycle conglomerate, along with Rocky Mountain, CCM, Balfa, and
other Canadian brands.

mikadobicycles.comdefault.aspOpen ↗ procycle.comdefault.aspOpen ↗

Mikado has long specialized in touring bikes, from what I hear. I have an excellent ca. 1980 touring
bike from them with all the good features (mid-fork rack bosses, three bottle cage boss sets, road
triple, spare-spoke mounting bosses on the chainstay...)

Mikado still makes touring bikes, though they're swamped by the numerous comfort and utility bikes
in their line-up. They sell electric bikes, a nice generator-hub-equipped "utility" bike, about four
different kinds of recumbents (!), and the Lakeshore, a bike so goofy I have mocked it previously:

mikadobicycles.comrandonnee bikes.aspOpen ↗

It looks like the ugly offspring of an innocent 700c hybrid bike accosted on a bike path by a
freeride bike.

Not a paid endorser,
--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

Sheldon Brown said:

The "phantom chainring" technique is well known for use on homebuilt tandems, I've done it myself,
but won't work on a conventional single frame 'cause the chainstay is in the way of where the
phantom chainring would need to go.

How about a phantom ring that's got a really big center hole, with some sort of angled
bushing...uhhh....nevermind.

Quoted message said:

Sheldon "Nice Try" Brown

--
Rick Onanian

Kinky Cowboy said:

... An eccentric BB changes the relationship between the three contact points, and the effective
chainstay length/wheelbase, every time you adjust the chain

How would an eccentric BB change the effective wheelbase, as the rear wheel is located in the
same place?

Tom Sherman – Close to 41½ N, 90½ W

Ryan Cousineau <[email hidden]> wrote in
:"]news:[email hidden]:

Quoted message said:

I can explain some of these features. This is indeed meant as a fairly specialized dirt-jumper,
but it's running 24" wheels stock, which is bigger than BMX (it's a now-popular wheel option for
certain freeride and dirt-jump bikes).

The rotor is because this is for doing dirt-jump tricks. It ends up being a big boy's big-air bike

One of my son's riding buddies has a bike like that and he follows them, and they are hard core free-
riders, off some of those awesome north shore jumps. Can't remember the name of the frame but it has
front suspension only, rear is rigid. Guy is a great rider.

On Mon, 29 Dec 2003 15:20:28 GMT, Kinky Cowboy <[email hidden]>

Quoted message said:

Has anybody built an "inverted phantom" by using a pair of derailleur pulleys running on the
outside of the timing chain run, linked by a free floating pair of tie bars? This would give more
chain wrap on the timing rings (negligible advantage) and the timing chain would be running through
a closed loop so it couldn't eject the tensioner over rough ground, which looks possible with
phantom rings. A selection of mounting holes for the pulley axle bolts would give all the
adjustability you could need.

Funny you should ask, I was just about to post this:
gallery.consumerreview.comslacker.jpgOpen ↗

I found it when I googled for phantom chainrings to try to learn more.
--
Rick Onanian

In article <[email hidden]>,

Mike Latondresse mikelat@no_spamshaw.ca said:

Ryan Cousineau <[email hidden]> wrote in :"]news:[email hidden]:

Quoted message said:

I can explain some of these features. This is indeed meant as a fairly specialized dirt-jumper,
but it's running 24" wheels stock, which is bigger than BMX (it's a now-popular wheel option for
certain freeride and dirt-jump bikes).

The rotor is because this is for doing dirt-jump tricks. It ends up being a big boy's big-
air bike

One of my son's riding buddies has a bike like that and he follows them, and they are hard core
free-riders, off some of those awesome north shore jumps. Can't remember the name of the frame but
it has front suspension only, rear is rigid. Guy is a great rider.

Shore-oriented companies now make very, very tough hardtails. Aside from being good dirt-jump bikes
(rear suspension tends to absorb the ramp launch and otherwise behave badly during big jumps), they
also add new challenges for riders who can already ride nearly everything thanks to 5-8" of travel
(I've had only a brief experience with serious freeride machinery, but it convinced me that with
this equipment, I could very nearly ride everything, too. Well, except the skinnies. And the A-
frames. And the really big drops...)

Typical Shore hardtail spec is steel or very heavy Aluminum, and nondescript derailleurs combined
with a heavy-duty long-travel fork and big discs.

-RjC.

Kona Roast: konaworld.com2k4 roast.cfmOpen ↗

Rocky Mountain Flow: rocky-mountain.comflow.aspxOpen ↗

Norco Torrent (_very_ high-spec components; Saint and a Jr.-T fork!):
norco.comtorrent.htmOpen ↗

Etc....

--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club