Fixed gear conversion questions

Spacers come off the right, go on left, then re true. Chain
tensioners won't work with a fixie, rather a single speed. I
altered one vert DO bike with an Eccentric BB insert but not
cheap @ $150. DO replacement is $120. If you don't get a
true track hub, max hold thread lock and a conventional
lockring can work. Tom

--
Bruni Bicycles
"Where art meets science"
brunibicycles.com
410.426.3420
Michael Press <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

I'm going to convert my old 7-speed road bike to fixed gear. I want
to do it as cheaply as possible; if I really enjoy it I'll spend more
later or get a "real" fixed gear bike.

From reading Sheldon's fixed gear pages (excellent as usual) it seems
I only need:
* A fixed gear sprocket (it'll thread into my freewheel hub)
* A chain tensioner (like the Surly Singelator) since the bike has
vertical dropouts

Optionally I may also get
* A new chain as recommended by Sheldon
* Short stack chainring bolts so I can remove the big ring

And I'll have to re-dish the rear wheel. I'll remove the derailleurs,
shifter and cables, but leave both brakes on.

I have a couple of questions though:
1) How do I set or adjust the chainline since the chainring is in a
fixed position and the sprocket is fixed to the hub? The only thing I
can think of is change the wheel dish, but that doesn't seem right.
2) Sheldon seems to say that chain tensioners will break if you apply
rearward pedal pressure, but it's not completely clear. Is this really
true? Seems like not being able to brake by pedal pressure would take
alot of the fun out of a fixie.
3) Any opinions on the $30 Pyramid chain tensioner vs. the $50 Surly
Singelator?

Any other comments or suggestions on this project are welcomed.

Thanks,
Michael

Michael Press said:

I'm going to convert my old 7-speed road bike to fixed
gear. I want to do it as cheaply as possible; if I
really enjoy it I'll spend more later or get a "real"
fixed gear bike.

From reading Sheldon's fixed gear pages (excellent as
usual) it seems I only need:
* A fixed gear sprocket (it'll thread into my
freewheel hub)
* A chain tensioner (like the Surly Singelator) since the
bike has vertical dropouts

Nope, you need to re-read the articles. Chain tensioners
cannot be used with fixed gears, only with coastie
singlespeeds.

Quoted message said:

Optionally I may also get
* A new chain as recommended by Sheldon
* Short stack chainring bolts so I can remove the big ring

And I'll have to re-dish the rear wheel. I'll remove the
derailleurs, shifter and cables, but leave both brakes on.

I have a couple of questions though:
1) How do I set or adjust the chainline since the
chainring is in a fixed position and the sprocket is
fixed to the hub? The only thing I can think of is
change the wheel dish, but that doesn't seem right.

The chainline is adjusted by re-arranging spacer washers on
the rear axle, moving some from the right side to the left
side, so the hub shell (and sprocket) moves to the right.

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center
of the bike.

Quoted message said:

2) Sheldon seems to say that chain tensioners will break
if you apply rearward pedal pressure, but it's not
completely clear.

Gee, I wrote:

"Note! Chain tensioners cannot be used with fixed-gear or
coaster brake systems!"

I printed that in boldface red type, and italicized
"cannot."

What part of that was not completely clear? Should I
have used a bigger font? Underlined? A handful of
exclamation points?

Quoted message said:

Is this really true?

Naw, I am in the habit of lying about bicycle safety
issues, because I own a lot of hospital stock. I guess you
caught me! ;-)

Quoted message said:

Seems like not being able to brake by pedal pressure would
take alot of the fun out of a fixie.

Not just a matter of "fun", it's a matter of safety. A
chain tensioner WON'T WORK with a fixed gear, and as a
result, the chain will likely fall off. This is dangerous
on a fixed gear.

Quoted message said:

3) Any opinions on the $30 Pyramid chain tensioner vs. the
$50 Surly Singelator?

The Pyramid is very similar to the original Singleator, but
the newer Singleator is nicer, but currently unavailable--
waiting for a new production run.

Singlespeed chain tensioners, even the best of them, are
ugly kludges, and they CANNOT BE USED FOR FIXED GEARS.

If you want to singlize a bike with vertical dropouts, the
White Industries eccentric hub is a vastly superior
solution, well worth what it costs. sheldonbrown.comwhiteOpen ↗
hubs

Sheldon "Trying To Be Clear" Brown +-------------------------------------------------------
---------+
| The thing about the cold is that you can never tell how
| cold | it is from looking out a kitchen window. You have
| to dress | up, get out training and when you come back,
| you then know | how cold it is. -Sean Kelly |
+-----------------------------------------------------------
-----+ 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 Fri, 07 May 2004 09:26:25 -0400, Michael Press

may have said:

Any other comments or suggestions on this project are
welcomed.

Given that you're probably going to have to spend upwards
of $175 for a hub, sprocket, spacers and such, perhaps this
would be a good time to cast around through the used bike
supply to see if there's one which has more useful
dropouts...and convert *that*, instead. You'll likely spend
less, and you'll still have the old roadie available to
ride as well.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Quoted message said:

Quoted message said:

And I'll have to re-dish the rear wheel. I'll remove
the derailleurs, shifter and cables, but leave both
brakes on.

Quoted message said:

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center of
the bike.

If you're using an existing hub/wheel for the conversion to
a fixie and assuming this wheel is already set up for the
frame to be used as the fixie, then wouldn't it be correctly
spaced for the frame and already be dished? Re dishing
implies you've changed the axle distance and then it
wouldn't fit the frame anymore unless you tweak the frame.
Am I missing something??

Neil

Someone said:

Quoted message said:

Quoted message said:

And I'll have to re-dish the rear wheel. I'll remove
the derailleurs, shifter and cables, but leave both
brakes on.

I replied, in part:

Quoted message said:

Quoted message said:

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center
of the bike.

The anonymous 'Tool Guy said:

If you're using an existing hub/wheel for the conversion
to a fixie and assuming this wheel is already set up for
the frame to be used as the fixie,

But it isn't. He's talking about converting a derailer bike,
using the original rear wheel.

Quoted message said:

then wouldn't it be correctly spaced for the frame and
already be dished? Re dishing implies you've changed the
axle distance and then it wouldn't fit the frame anymore
unless you tweak the frame. Am I missing something??

Yes, you are. The original poster was talking about
modifying his or her original derailer-type wheel, which
would have the freewheel threads too close to the centerline
of the frame for good chainline.

I explained that he would have to rearrange spacers by
moving some from the right side to the left side (but
leaving the total thickness the same) so as to move the hub
shell to the right, until the fixed sprocket would line up
properly with the chainring.

This operation would also move the rim to the right, so the
dish would then be incorrect. The dish would then need to be
corrected by tightening spokes on the left side to bring the
rim back to the centerline of the frame.

Sheldon "Having Trouble Making Myself Clear Today" Brown
+------------------------------------+
| Experience is a hard teacher, | because she gives the
| test first, | the lesson after. -- Vernon Law |
+------------------------------------+ 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 ↗

Sheldon Brown said:

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center of
the bike.

I was assuming I would re-dish first. Now I understand.

Quoted message said:

Quoted message said:

2) Sheldon seems to say that chain tensioners will break
if you apply rearward pedal pressure, but it's not
completely clear.

Gee, I wrote: "Note! Chain tensioners cannot be used with
fixed-gear or coaster brake systems!" I printed that in
boldface red type, and italicized "cannot." What part of
that was not completely clear? Should I have used a bigger
font? Underlined? A handful of exclamation points?

I never saw that quote - it's on the singlespeed page, not
the fixie or fixie conversion pages. I was referrring to
this quote on the fixie-conversion page:

"You cannot use a derailer on a fixed gear bike, even as a
chain tensioner, because when you resist the rotation of the
pedals, you would bend the derailer. This presents a problem
if you want to use a frame with vertical dropouts as a fixed
gear, because there's no easy way to adjust the chain
tension. This is also true of chain tensioners sold for
singlespeed coasting bikes, such as the Surly Singleator."

To me, this wasn't clear. Certainly the red bold warning on
the singlespeed page is clear. I suggest adding that to the
fixie-conversion page since that's where fixie-newbies like
myself would be reading.

Quoted message said:

Quoted message said:

Is this really true?

Naw, I am in the habit of lying about bicycle safety
issues, because I own a lot of hospital stock. I guess you
caught me! ;-)

I guess I was really asking for more detail or other ideas
and didn't word it right. I don't intuively understand why
backpressure on the chain would bend a derailleur or chain
tensioner.

Quoted message said:

Quoted message said:

Seems like not being able to brake by pedal pressure
would take alot of the fun out of a fixie.

Not just a matter of "fun", it's a matter of safety. A
chain tensioner WON'T WORK with a fixed gear, and as a
result, the chain will likely fall off. This is dangerous
on a fixed gear.

Singlespeed chain tensioners, even the best of them, are
ugly kludges, and they CANNOT BE USED FOR FIXED GEARS.

I think I've got it now ;-)

Thanks, Michael

Sheldon Brown said:

Someone said:

Quoted message said:

>And I'll have to re-dish the rear wheel. I'll remove
>the derailleurs, shifter and cables, but leave both
>brakes on.
>

I replied, in part:

Quoted message said:

Quoted message said:

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center
of the bike.

The anonymous "Tool Guy" wrote:

Why am I anonymous? My name on the wreck is Toolguy and I
signed it with my real name, Neil.

Quoted message said:

Quoted message said:

If you're using an existing hub/wheel for the conversion
to a fixie and assuming this wheel is already set up for
the frame to be used as the fixie,

But it isn't. He's talking about converting a derailer
bike, using the original rear wheel.

Quoted message said:

then wouldn't it be correctly spaced for the frame and
already be dished? Re dishing implies you've changed the
axle distance and then it wouldn't fit the frame anymore
unless you tweak the frame. Am I missing something??

Yes, you are. The original poster was talking about
modifying his or her original derailer-type wheel, which
would have the freewheel threads too close to the
centerline of the frame for good chainline.

I explained that he would have to rearrange spacers by
moving some from the right side to the left side (but
leaving the total thickness the same) so as to move the hub
shell to the right, until the fixed sprocket would line up
properly with the chainring.

This operation would also move the rim to the right, so the
dish would then be incorrect. The dish would then need to
be corrected by tightening spokes on the left side to bring
the rim back to the centerline of the frame.

Got it now. Thanks. Not having done this before, I was
interpreting the spacing on the freewheel threads (spacing
the cog on the freewheel threads instead of the axle). It
makes perfect sense now. Thanks for the clarification.

Neil (aka Toolguy)

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

Quoted message said:

If you want to singlize a bike with vertical
dropouts, the White Industries eccentric hub is a
vastly superior solution, well worth what it costs.
sheldonbrown.comwhite hubsOpen ↗

Sheldon "Trying To Be Clear" Brown

Sheldon, So does this also mean that if you want to use a
flip-flop hub, with fixed on one side and SS on the other,
and a frame with vertical drop-outs, that you MUST use this
eccentric hub?

Thanks, Erik Brooks

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

Quoted message said:

On Fri, 07 May 2004 09:26:25 -0400, Michael Press

may have said:

Any other comments or suggestions on this project are
welcomed.

Given that you're probably going to have to spend upwards
of $175 for a hub, sprocket, spacers and such, perhaps
this would be a good time to cast around through the used
bike supply to see if there's one which has more useful
dropouts...and convert *that*, instead. You'll likely
spend less, and you'll still have the old roadie available
to ride as well.

True. A couple weeks back, I spied a nice road frame & fork
of indeterminate origin (good workmanship, Campy horizontal
dropouts) for $50 at the local used bike emporium: Citybikes
in Portland, Oregon.

I built a single-speeder around a Raleigh frame that was
given to me- about $35 for the fork and then I scrounged
from my pile. Total bill came to $65, I think.

Jeff

Erik Brooks wrote:

I said:

Quoted message said:

If you want to singlize a bike with vertical
dropouts, the White Industries eccentric hub is a
vastly superior solution, well worth what it costs.
sheldonbrown.comwhite hubsOpen ↗

Sheldon "Trying To Be Clear" Brown

Erik Brooks asked:

Quoted message said:

Sheldon, So does this also mean that if you want to use a
flip-flop hub, with fixed on one side and SS on the other,
and a frame with vertical drop-outs, that you MUST use
this eccentric hub?

Yep.

They're swell hubs, I like mine a lot.
sheldonbrown.orgrambouilletOpen ↗

Sheldon "Eccentric" Brown +-------------------------------------------------
+
| Search the Quality Bicycle Products Catalog | and order
| on line: | sheldonbrown.comqualityOpen ↗ |
+-------------------------------------------------+ 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 ↗

Werehatrack said:

Given that you're probably going to have to spend upwards
of $175 for a hub, sprocket, spacers and such, perhaps
this would be a good time to cast around through the used
bike supply to see if there's one which has more useful
dropouts...and convert *that*, instead. You'll likely
spend less, and you'll still have the old roadie available
to ride as well.

$175?!? How much is that White Industries hub again?

A Dura-Ace cog is only like $20 and a lockring is maybe $8.
If you ask nicely, most shops will give you a handful of
spacers when you buy a hub or just about anything else.

EK

Michael Press said:

I'm going to convert my old 7-speed road bike to fixed
gear. I want to do it as cheaply as possible; if I
really enjoy it I'll spend more later or get a "real"
fixed gear bike.

From reading Sheldon's fixed gear pages (excellent as
usual) it seems I only need:
* A fixed gear sprocket (it'll thread into my
freewheel hub)
* A chain tensioner (like the Surly Singelator) since the
bike has vertical dropouts

Optionally I may also get
* A new chain as recommended by Sheldon
* Short stack chainring bolts so I can remove the big ring

And I'll have to re-dish the rear wheel. I'll remove the
derailleurs, shifter and cables, but leave both brakes on.

I have a couple of questions though:
1) How do I set or adjust the chainline since the
chainring is in a fixed position and the sprocket is
fixed to the hub? The only thing I can think of is
change the wheel dish, but that doesn't seem right.
2) Sheldon seems to say that chain tensioners will break
if you apply rearward pedal pressure, but it's not
completely clear. Is this really true? Seems like not
being able to brake by pedal pressure would take alot
of the fun out of a fixie.
3) Any opinions on the $30 Pyramid chain tensioner vs. the
$50 Surly Singelator?

Although a vertical-end bike can be made functional as a
single speed by adding a chain tensioner (and no, there
isn't much difference between those) fixed is another
thing entirely.

The forces involved are enough to wreck a derailleur or
tensioner ( and a used derailleur, free, does the same job
as your $30 fashion item).

Why not keep your eye out for a used road frame with normal
horizontal ends? Or if you love your bike, give it a little
plastic surgery: yellowjersey.orgtrakends.htmlOpen ↗

To adjust chainline on a fixed hub, move the crank in with
the appropriate )shorter) spindle. Most classic spindles are
asymmetric and reversible.

With a road freewheel hub*, your cog ends up pretty far
inside. You can move axle spacers from the right to the
left, as you surmised, and recenter the rim over the
locknuts. Your wheel will end up with more even tension.

*We've had this discussion to death, and I can't add
anything new, but you might review previous threads here
about a fixed cog on a hub without a proper reversed
lockring. YMMV.
--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971

Quoted message said:

Quoted message said:

Quoted message said:

And I'll have to re-dish the rear wheel. I'll remove
the derailleurs, shifter and cables, but leave both
brakes on.

Quoted message said:

Quoted message said:

Once you have adjusted the chain line, you will then need
to re-dish the wheel to bring the rim back to the center
of the bike.

toolguy said:

If you're using an existing hub/wheel for the conversion
to a fixie and assuming this wheel is already set up for
the frame to be used as the fixie, then wouldn't it be
correctly spaced for the frame and already be dished? Re
dishing implies you've changed the axle distance and then
it wouldn't fit the frame anymore unless you tweak the
frame. Am I missing something??

While a derailleur system handles the 52-26 combination
complainingly, a fixed-length chain wouldn't like that as
much. We're assuming his wheel is spaced for a seven
freewheel but has only one cog now. Hence the
"respace/redish" advice.
--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971

On Fri, 07 May 2004 17:50:37 -0700, Elmo Spam King

may have said:

Werehatrack said:

Given that you're probably going to have to spend upwards
of $175 for a hub, sprocket, spacers and such, perhaps
this would be a good time to cast around through the used
bike supply to see if there's one which has more useful
dropouts...and convert *that*, instead. You'll likely
spend less, and you'll still have the old roadie
available to ride as well.

$175?!? How much is that White Industries hub again?

Around $160. I've never seen one in a shop, though. I
suspect that the local shops don't get much demand for fixie
stuff, which is reflected by the fact that to date, I have
seen a grand total of one fixie being ridden in this
immediate area. You would think that our relatively flat
terrain would be prime territory for this type of unit, but
I suspect the prospect of Thou Shalt Pedal When Moving is an
unappetizing "feature" for our warm summers.

Quoted message said:

A Dura-Ace cog is only like $20 and a lockring is maybe $8.
If you ask nicely, most shops will give you a handful of
spacers when you buy a hub or just about anything else.

The ones that have them, that is. We seem to have sprouted a
number of shops whose stock of fiddly bits is limited,
sparse or nearly nonexistent...and a couple that are almost
aggressively anticooperative about supplying what I see as
really common repair items. We also have some that are very
accommodating, helpful, well-stocked and/or willing to get
whatever the customer needs, and not rapaciously priced.
It's not hard to predict the effect that this has had on my
shopping habits.

--
My email address is antispammed; pull WEEDS if replying via
e-mail. Typoes are not a bug, they're a feature. Words
processed in a facility that contains nuts.

michael-<< I'm going to convert my old 7-speed road bike to
fixed gear. I want to do it as cheaply as possible; if I
really enjoy it I'll spend more later or get a "real" fixed
gear bike.

From reading Sheldon's fixed gear pages (excellent as usual)
it seems I only need:
* A fixed gear sprocket (it'll thread into my freewheel hub)
* A chain tensioner (like the Surly Singelator) >><BR><BR>

DO NOT use a chain tensioner with a fixed gear. You run the
risk of a ripping it off the bike...Go single speed(BMX
freewheel) but not fixed!!

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St.
Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali
costruite eccezionalmente bene"

Qui si parla Campagnolo said:

michael-<< I'm going to convert my old 7-speed road bike
to fixed gear. I want to do it as cheaply as possible; if
I really enjoy it I'll spend more later or get a "real"
fixed gear bike.

From reading Sheldon's fixed gear pages (excellent as
usual) it seems I only need:
* A fixed gear sprocket (it'll thread into my
freewheel hub)
* A chain tensioner (like the Surly Singelator) >><BR><BR>

DO NOT use a chain tensioner with a fixed gear. You run
the risk of a ripping it off the bike...Go single
speed(BMX freewheel) but not fixed!!

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St.
Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali
costruite eccezionalmente bene"

As Peter said, don't use a chain tensioner. They're not
designed to resist the force when you resist the motion of
the pedals (back pedal). Depending on how horizontal the drop-
outs are on your bicycle bicycle, you may be able to get the
chain tight without one.

You'll also need a 'retaining system' of some kind. You can
Loctite a bottom bracket lockring overtop of the cog, to
prevent it from unthreading when you 'back pedal'. If you're
going brakeless, seriously consider getting a track hub.

Cheers

Cam

Quoted message said:

You'll also need a 'retaining system' of some kind. You
can Loctite a bottom bracket lockring overtop of the cog,
to prevent it from unthreading when you 'back pedal'. If
you're going brakeless, seriously consider getting a
track hub.

Yes, I'd prefer a lockring even though I'll keep the
brake(s). I've also discovered since my original post that
the bike actually has "semi-horizontal" dropouts - much
closer to horizontal than vertical, so I'm defintely going
forward with this.

Can you give more detail on this - what's a bottom bracket
lockring? Is that from an old-style bottom bracket? I recall
the last BB I installed (a few years ago), a cartridge-type,
each half of the BB screwed in on opposite sides, but I
don't recall a lockring. Can this still be bought or do you
have to scavenge an old BB?

Also, does the lockring screw into the hub threads after
the cog? If not, what do you mean by Locktiting "overtop
of the cog"?

Thanks, Michael

Michael Press said:

Quoted message said:

You'll also need a 'retaining system' of some kind. You
can Loctite a bottom bracket lockring overtop of the cog,
to prevent it from unthreading when you 'back pedal'. If
you're going brakeless, seriously consider getting a
track hub.

Yes, I'd prefer a lockring even though I'll keep the
brake(s). I've also discovered since my original post that
the bike actually has "semi-horizontal" dropouts - much
closer to horizontal than vertical, so I'm defintely going
forward with this.

Can you give more detail on this - what's a bottom bracket
lockring? Is that from an old-style bottom bracket? I
recall the last BB I installed (a few years ago), a cartridge-
type, each half of the BB screwed in on opposite sides,
but I don't recall a lockring. Can this still be bought or
do you have to scavenge an old BB?

Also, does the lockring screw into the hub threads after
the cog? If not, what do you mean by Locktiting "overtop
of the cog"?

Thanks, Michael

Yes, the bottom bracket lockring is from the old-style
bottom bracket. Check out Sheldon Brown's excellent guide
to conversions at sheldonbrown.comfixedOpen ↗
conversion.html With the orientation of the dropouts, you
can probably get good chain tension. You could also use a
"half-link" in the chain, which is a short link that
allows more flexibility than standard links when adjusting
chain length.

You can probably still get lockrings, but I use a track hub,
so I've never pursued it. You thread on the cog, then the
lockring, sealing it in place with Loctite. Depending on the
wheel, you may have to redish it.

For a good discussion forum for fixed gear, check out
www.bikeforums.net in the single speed/fixed gear forum.

Cheers

Cam

Michael Press <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

I'm going to convert my old 7-speed road bike to fixed
gear. I want to do it as cheaply as possible; if I
really enjoy it I'll spend more later or get a "real"
fixed gear bike.

<SNIP>

If you really mean "as cheaply as possible" then you can
1. disassemble the freewheel & degrease the innards
2. reassemble it using JB Weld or similar structural epoxy
instead of lubricant (put the bearings into the epoxy so
that it aligns... experience talking)
3. shuffle cogs, if desired, to improve chainline
4. degrease & threadlock the freewheel onto the hub
5. possibly swap inner and outer chainrings to give more
gear ratios with a smaller chain length variation

Forget that "buying" and redishing for a while. Maybe buy
(Ouch!) SRAM powerlink(s) to trivialize chain length/gear
ratio changes.

Using 39 and 42t rings can give several ratios with no chain
length changes (depends on your dropouts). I've been happy
riding fixed on my 53t ring with only horiz dropouts
supporting changing between two "fixed" gears. I change
gears on the road in about a minute.

I'm suspicious that the use of the larger gears reduces
the tendency to dechain in addition to the increased chain
and gear life you get for free. I did not disturb my
freewheel cogs to optimize chainline nor did I spend on a
new retro-chain.

(on topic) Ed