Compact Crank Ring Differential

In article
<[email hidden]>,
[email hidden] says...

Quoted message said:

According to Cyclingnews, several Giro riders were running 52/34

chain

Quoted message said:

rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

My recolletion from cyclingnews was a 52x36 with a 29 in back,
specifically for Diluca.

Dans le message de
news:[email hidden],
VeloJon <[email hidden]> a réfléchi, et puis a déclaré :

Quoted message said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

They weren't swapping back and forth. One change for up - one change for
down. They could run the K7's almost full range in either ring.

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I saw that too, and I assume they solved it with a custom / pre-
production front derailleur or a front derailleur intended for triple
ring cranksets. The derailleurs are the most important components that
limit these setups. It is also possible that the limit of 16 teeth
difference is merely a best case max rather than a hard limit. IOW,
you may be able to use this setup with some loss of shifting
performance. Even in the worst case, keep in mind that with a
difference of more than 16 teeth (say, 18) you are not going to be
shifting back and forth as much anyway so I would say that the
performance gain you get from this "beyond standard" setup may still
be worth the gain you get from these gears even factoring in the
slower, noisier, oe whatever that you have to put up with. Given that
the 16 teeth 50/34 cranksets can be used with typical derailleurs not
specific to the compact cranks, maybe you will get roughly the same
performance from a 52/34 with a compact designed front derailleur as
those that run 50/34 with a standard derailleur designed for 130-135
double ring cranks.

I would for for it and if you have to buy another pair of rings, how
bad can that be? You may find that the 50 tooth ring has less
influence than you think. Looking at gear charts, you will only need
to spin 6% faster. A 50*12 is slightly closer to a 53*13 than a 53*12,
but it is still bigger than a 53*13 and you may even find the 50*12 a
better gear for you than you had guessed. I would absolutely recommend
trying the gears first before you change the cassette. My hope for the
compact cranks (when I finally get around to changing) is closer gear
ratios. I can run a 12/21 or 12/23 in place of a 12/25< and even put
my existing cassettes back on for really mountainous terrain and leave
the 18 at home. I am convinced that a 50*12 is enough for me since I
have already spent enough time with a 50/39 (on a 135 bcd) to know
this. I guess that is one more option, to buy a budget 50T chainring
for an existing crank to see how much you really want or need to
change. There are so many options, you only need to decide what to try
first, so think it through comparing options side by side. You may not
really need the 18 tooth difference, or that you can get along with a
52/35, and that (only 1 tooth over the implied max.) I am sure will
not cause any problems. Some times these min. and max. specifications
come from variables that do not apply to your intended setup. As I
said, given that the standard double front derailleurs really work ok
with the 16 tooth differential, I can't imagine that a dedicated
(compact) design won't be just fine with 17 if not 18 teeth
differential to deal with. And... don't forget to make sure your rear
derailleur is up to the task with your intended cassette(s). I believe
this is precisely why Campagnolo brought out the medium length rear
derailleurs, which needs to be able to handle the larger rear cogs and
the chain wrap differential.

Don't forget to post your findings so that others can be more
confident in their choices (please).

Chris M said:

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I saw that too, and I assume they solved it with a custom / pre-
production front derailleur or a front derailleur intended for triple
ring cranksets. The derailleurs are the most important components that
limit these setups. It is also possible that the limit of 16 teeth
difference is merely a best case max rather than a hard limit. IOW,
you may be able to use this setup with some loss of shifting
performance. Even in the worst case, keep in mind that with a
difference of more than 16 teeth (say, 18) you are not going to be
shifting back and forth as much anyway so I would say that the
performance gain you get from this "beyond standard" setup may still
be worth the gain you get from these gears even factoring in the
slower, noisier, oe whatever that you have to put up with. Given that
the 16 teeth 50/34 cranksets can be used with typical derailleurs not
specific to the compact cranks, maybe you will get roughly the same
performance from a 52/34 with a compact designed front derailleur as
those that run 50/34 with a standard derailleur designed for 130-135
double ring cranks.

I would for for it and if you have to buy another pair of rings, how
bad can that be? You may find that the 50 tooth ring has less
influence than you think. Looking at gear charts, you will only need
to spin 6% faster. A 50*12 is slightly closer to a 53*13 than a 53*12,
but it is still bigger than a 53*13 and you may even find the 50*12 a
better gear for you than you had guessed. I would absolutely recommend
trying the gears first before you change the cassette. My hope for the
compact cranks (when I finally get around to changing) is closer gear
ratios. I can run a 12/21 or 12/23 in place of a 12/25< and even put
my existing cassettes back on for really mountainous terrain and leave
the 18 at home. I am convinced that a 50*12 is enough for me since I
have already spent enough time with a 50/39 (on a 135 bcd) to know
this. I guess that is one more option, to buy a budget 50T chainring
for an existing crank to see how much you really want or need to
change. There are so many options, you only need to decide what to try
first, so think it through comparing options side by side. You may not
really need the 18 tooth difference, or that you can get along with a
52/35, and that (only 1 tooth over the implied max.) I am sure will
not cause any problems. Some times these min. and max. specifications
come from variables that do not apply to your intended setup. As I
said, given that the standard double front derailleurs really work ok
with the 16 tooth differential, I can't imagine that a dedicated
(compact) design won't be just fine with 17 if not 18 teeth
differential to deal with. And... don't forget to make sure your rear
derailleur is up to the task with your intended cassette(s). I believe
this is precisely why Campagnolo brought out the medium length rear
derailleurs, which needs to be able to handle the larger rear cogs and
the chain wrap differential.

I've posted more than a few times my personal experience with front
derailleur shifting efficiency with the 16 tooth gap in the "typical"
50-34 compact ring set up.

My experience is that a standard derailleur works, but that anything
less than top of the line standard components (I run Shimano, so Dura
Ace front der. and shifter) works slowly and sluggishly shifting up
from 34 to 50. Actually, the best combo I have found for crisp and
quick upshifts is Dura Ace Shifter and FSA C-16 compact specific front
der.

So it would be my guess that standard front ders. would have a tough
time shifting 17 or 18 teeth up with any precision. They are, after
all, designed for 14 teeth.

Cassettes are another animal. If you want the benefit of lower gears
without sacrificing your highest gear, you necessarily are going to
end up with a wide block with more than a few 2 and even 3 tooth
jumps, even if you run a 10 speed.

In order to keep your high gear close to what it was with the standard
53:12, you need to run a 50:11. In order to get the benefit of a
lower low that 39:25 or even 39:27, you need to run at least a 26 with
your compact.

SRAM sells a 10 speed cassette with these cogs:
11/12/13/14/15/17/19/21/23/26

Your second lowest gear @ 34:23 is slightly lower than your lowest @
39:25 (and only slightly higher than 39:27); and you have one mega low
gear. That's what compact is all about. But you have three 2 tooth
jumps and one 3 tooth in your block as a trade off.

IRD sells 10 speed cassettes with these cogs:

11/12/13/14/15/17/19/21/23/25

and

11/12/13/15/17/19/21/23/25/28

While the former is pretty close to the SRAM, the latter would be a
nightmare for a straight block purist. But it yields 2 lower gears
than 39:27, so is a compromise that fools such as I are willing to
accept in order to hang on to the back of the pack uphill as well as
down.

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I have a 110 mm crank with a 52-34 chainring. I have not poblems
shifting. I have to shift slowly no to drop the chain. But if I drop
the chain, I just shift in the opposite direction while pedaling until
the chain re-engages.

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I've used a 48-30 ring combination with a standard double front
derailleur. It shifted badly. But I did not shift it too often. A
46-30 with a compact front derailleur works OK. Again, I don't really
shift it too often. I've never figured out why people/companies seem
to love the 50-34 combination. And now you want to go with a 52-34?
Shimano makes a 12-25 and 12-27 cassette in 9 and 10 speed.
Campagnolo makes a 12-25 cassette in 10 speed. One would think you
could get a more than high enough gear with a 50x12 and a low enough
with a 34x27 or 34x25. But you need a high of 52x12 AND a low of
34x25 or 34x27? How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

email hidden said:

How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

Big hills.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
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VeloJon said:

Before I go and try a 52/34 combo,
opinions please?

I don't know what you are used to, but I don't even like the 34/50 for
other reasons... too much rear shifting when the front is shifted, and
too little overlap. I run a 34/48 with a 9spd 12-26 and don't miss the
high gears when I'm tucked and coasting at 55mph. If you are running a
very wide range cassette the overlap is less of an issue, though.

Quoted message said:

How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

On the contrary, folks who need a low bottom gear very often have more
use for a high top gear as well. The 52x12 is for going down the hills
that you need the 34x25 for. Or in my case, the hills that I need the
30x30 for. I suppose you could always coast down the steeper hills, but
pedaling down them is sometimes useful and often fun.

My morning commute involves a left turn off of a 5 lane street in
downhill 35 MPH traffic. The hill isn't steep enough for me to reach
that speed on gravity alone, and being able to help things along without
spinning like a madman is very nice.

Quoted message said:

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

Quoted message said:

I've used a 48-30 ring combination with a standard double front
derailleur. It shifted badly. But I did not shift it too often. A
46-30 with a compact front derailleur works OK. Again, I don't really
shift it too often. I've never figured out why people/companies seem
to love the 50-34 combination. And now you want to go with a 52-34?
Shimano makes a 12-25 and 12-27 cassette in 9 and 10 speed.
Campagnolo makes a 12-25 cassette in 10 speed. One would think you
could get a more than high enough gear with a 50x12 and a low enough
with a 34x27 or 34x25. But you need a high of 52x12 AND a low of
34x25 or 34x27? How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

Just because.

I remember Nishiki Internationals with a then-new 34t low gear
freewheel. Our friend Peter Davis in Champaign IL sold a ton of them -
on the prairie, where the Interstate overpass is the highest point.

No rider can be wrong about his own opinion. Doesn't have to be logical.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

RS said:

My recolletion from cyclingnews was a 52x36 with a 29 in back,

That does work flawlessly here, with an old DuraAce front and bar
end shifters.

--
MfG/Best regards
helmut springer

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

It works fine and if ya must, get a 'compact' or triple FD..but I have
installed many 52(3)/34 systems and they work fine. Probably will need
a third eye type chainwatcher..steep angle from the 52(3) to the
34..but otherwise it works fine, particularly with Campagnolo. Still
OK with shimano altho not as clean.

email hidden said:

I've never figured out why people/companies seem
to love the 50-34 combination.

Because it is versatile?

Quoted message said:

How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

Old age and ego.

If you ride in a pack of riders who all have 53:12 as a high, you WILL
find numerous situations, downhill, where a 50:12 just doesn't cut it
(you might not spin OUT, per se, but you might well spin too MUCH).
And you don't have to be Godzilla for this to be the case.

Meanwhile, going up, you will NEED the low-low gears (I have a 34:28,
thank you very much) in order not blow up 56 year old knees and quads.
I live in a hilly area where 34:28 is not even all that wimpy. Being
able to climb even the most arduous pitches seated is a great quad
saver for a Master Fatty. You can stand and grind if you want - but
you don't HAVE to.

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

Quoted message said:

VeloJon said:

According to Cyclingnews, several Giro riders were running 52/34

chain

Quoted message said:

Quoted message said:

Quoted message said:

rings for the big climbs. I thought the conventional wisdom was

that

Quoted message said:

Quoted message said:

Quoted message said:

a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

Quoted message said:

I've used a 48-30 ring combination with a standard double front
derailleur. It shifted badly. But I did not shift it too often. A
46-30 with a compact front derailleur works OK. Again, I don't really
shift it too often. I've never figured out why people/companies

seem

Quoted message said:

Quoted message said:

to love the 50-34 combination. And now you want to go with a 52-

34?

Quoted message said:

Quoted message said:

Shimano makes a 12-25 and 12-27 cassette in 9 and 10 speed.
Campagnolo makes a 12-25 cassette in 10 speed. One would think

you

Quoted message said:

Quoted message said:

could get a more than high enough gear with a 50x12 and a low

enough

Quoted message said:

Quoted message said:

with a 34x27 or 34x25. But you need a high of 52x12 AND a low of
34x25 or 34x27? How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

Just because.

I remember Nishiki Internationals with a then-new 34t low gear
freewheel. Our friend Peter Davis in Champaign IL sold a ton of them -
on the prairie, where the Interstate overpass is the highest point.

No rider can be wrong about his own opinion. Doesn't have to be

logical.

Quoted message said:

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

It would be very helpful for Shimano to make 11-27 cassettes in Ultegra
quality for reasonable price and weight, and in 9 and 10 speed. 50-11 is
higher then 53-12 and sometimes needed. 34-27 is nice if you live
where there are steep hills and/or or just dog tired going up your own
hill. Where're not all 23 both in age and BMI. 😉

VeloJon said:

Quoted message said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I know many folks don't like the "T" word, but you're entering the realm
where a triple makes a whole lot more sense. I don't know what rear
cassette you want to use, but most of the folks on this thread have been
discussing a 12-25 or 12-27. With a 26-38-48 and and 11-21, you get
about the same top gear as a 52/12, a lower bottom gear than a 34/27,
and really really small jumps in the cassette, with easier shifting up
front too. A 28-38-48 with an 11-23 gives even easier shifting up front
and an even lower bottom gear (close to the 34-29 that some of the folks
reportedly used in the Giro). Both setups are easily done with any
74/110 crank, and even possible with a 74/130 "Racing Triple" crank.

Sorry, I'm suggesting practical gearing, I should know better...

Drew

--
Drew W. Saunders

dru (at) stanford (dot) eee dee you

RS said:

It would be very helpful for Shimano to make 11-27 cassettes in Ultegra
quality for reasonable price and weight, and in 9 and 10 speed.

That would certainly be nice. I've been using the 11-26 cassettes from
SRAM. I can't find any LX 12-32 cassettes to make 11-28's anymore. Are
they not being produced anymore?

--
Dane Buson - [email hidden]
All I know is what the words know, and dead things, and that
makes a handsome little sum, with a beginning and a middle and
an end, as in the well-built phrase and the long sonata of the dead.
-- Samuel Beckett

Drew Saunders said:

VeloJon said:

Quoted message said:

According to Cyclingnews, several Giro riders were running 52/34 chain
rings for the big climbs. I thought the conventional wisdom was that
a 16-tooth differential between the 2 rings was the max for shifting
smoothness on the front der. Before I go and try a 52/34 combo,
opinions please?

I know many folks don't like the "T" word, but you're entering the realm
where a triple makes a whole lot more sense. I don't know what rear
cassette you want to use, but most of the folks on this thread have been
discussing a 12-25 or 12-27. With a 26-38-48 and and 11-21, you get
about the same top gear as a 52/12, a lower bottom gear than a 34/27,
and really really small jumps in the cassette, with easier shifting up
front too. A 28-38-48 with an 11-23 gives even easier shifting up front
and an even lower bottom gear (close to the 34-29 that some of the folks
reportedly used in the Giro). Both setups are easily done with any
74/110 crank, and even possible with a 74/130 "Racing Triple" crank.

Sorry, I'm suggesting practical gearing, I should know better...

Drew

--
Drew W. Saunders

dru (at) stanford (dot) eee dee you

Amen - or 30/40/50 with 12-25 or so rear

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

RS said:

It would be very helpful for Shimano to make 11-27 cassettes in

Ultegra

Quoted message said:

Quoted message said:

quality for reasonable price and weight, and in 9 and 10 speed.

That would certainly be nice. I've been using the 11-26 cassettes from
SRAM. I can't find any LX 12-32 cassettes to make 11-28's anymore.

Are

Quoted message said:

they not being produced anymore?

--
Dane Buson - [email hidden]
All I know is what the words know, and dead things, and that
makes a handsome little sum, with a beginning and a middle and
an end, as in the well-built phrase and the long sonata of the dead.
-- Samuel Beckett

My commuter has a 50x34 and a sram 11-28 on the back, though older
8speed setup. Works fine and is a nice wide range. I use road derailleurs
on the back, currently a mid-cage Ultegra 6500 and it works fine though
suspect it would also work with a short-cage derailleur though beyond the
published specifications.

Steve Gravrock said:

Quoted message said:

How is it that you have the strength to spin out a
52x12 but don't have the power to climb in anything harder than a
34x25 or 34x27?

On the contrary, folks who need a low bottom gear very often have more
use for a high top gear as well. The 52x12 is for going down the hills
that you need the 34x25 for. Or in my case, the hills that I need the
30x30 for. I suppose you could always coast down the steeper hills, but
pedaling down them is sometimes useful and often fun.

If that pulls your chain, fine, but frankly "need" and huge gears don't
make much sense to me, unless you need to win that downhill sprint to
become a stage winner on the Tour.

No one, and that means no one, can "spin" a 52/12 on the flats. Build
up to a good rpm in a sprint, maybe, if you are very strong, but spin
along the road? No. On downhills, I can usually beat most anyone I
ride with, and my top gear is a 46/12. I do that by knowing better how
to corner, and by having a better mass/frontal area ratio.

--

David L. Johnson

If all economists were laid end to end, they would not reach a
conclusion.
-- George Bernard Shaw