Compact chainrings flex too much?

Dans le message de news:%6zYf.4608$fS6.3889@dukeread11,
Phil, Squid-in-Training <[email hidden]> a réfléchi,
et puis a déclaré :

Quoted message said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from a
108 to a 113. It upshifted rather poorly afterwards, but the rider
wanted at least the 3rd from last cog (9sp) while in the 34t. During
adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm. This
was rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain. The chain really had to be
forced up by the inner plate onto the chainring to get it to work.
Has anyone else seen this in practice?

A national level racer I ride with on occasion bought a compact, figuring he
could use a 50x36 in mountain races, and 53-42 regularly. He managed to
bend over and snap off the 53. He's a big boy,at 1m85 and around 90kg.
--
Sandy
--
C'est le contraire du vélo, la bicyclette.
Une silhouette profilée mauve fluo dévale
à soixante-dix à l'heure : c'est du vélo.
Deux lycéennes côte à côte traversent
un pont à Bruges : c'est de la bicyclette.
-Delerm, P.

In article <%6zYf.4608$fS6.3889@dukeread11>,

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front

I had a rubbing problem after swapping my 30-40-50 Racing-T for a
34-50 FSA compact. The other pieces of the equation are a Litespeed
Natchez frame, 13-23 9-speed cogset, and 9 speed Campagnolo chain.

Playing with my dial calipers I found that the ring-to-ring spacing
was less than Campagnolo specified for the current 10-speed setup which
is in turn .4mm closer than the 9-speed setup.

Adding a .4mm spacer on the big ring got me back a couple of gears without
ill effects; going out 1.0mm elimianted rub in the last 3 cogs rubbing but
made upshifts a little slower; I don't recall if I left that or went to
.8mm narrower.

I got my .4mm and .6mm shims from Wheels Manufacturing.
--
<a href="http://www.poohsticks.org/drew/">Home Page</a>
In 1913 the inflation adjusted (in 2003 dollars) exemption for single people
was $54,567, married couples' exemption $72,756, the next $363,783 was taxed
at 1%, and earnings over $9,094,578 were taxed at the top rate of 7%.

Sandy said:

A national level racer I ride with on occasion bought a compact, figuring he
could use a 50x36 in mountain races, and 53-42 regularly. He managed to
bend over and snap off the 53. He's a big boy,at 1m85 and around 90kg.
--

I use 52/36 all the time w/o problem and FSA rings. I've used 54/42 x
110 Sugino rings on Tandem for years, also w/o problems. Many people
have done this.

I don't recall broken rings at all.

Doug Taylor said:

The compact derailleurs are shaped to fit the diameter of the smaller
rings and designed to pull the bigger gap (they say).

The clear and undisputed winner is the Dura Ace 10/ FSA combination:
instant, easy, crisp, precise.

Coming in second is Dura Ace 10/Dura Ace 8. Not quite as good as the
above, but the 10 year old 8 speed Dura Ace is still Dura Ace.

Tied for Third is Ultegra 10 / FSA and Ultegra 10/Dura Ace 8. My Dura
Ace shifter blew up, and the Ultegra 10 I swapped it with just doesn't
pull the either derailleur with the authority of the two above. I'm
still messing around with all kinds of variables: cable tension,
limits, height above the rings.

I've had great luck with DA 8 font derailleur and compact cranks. I
most frequently use Campy 10sp front derailleurs and not the CT type.
The IRD and CT have not been impressive. I can get a Campy front with
Ergo shifters to shift rings like Sugino that don't have shift
assists. You cannot tell how good a 50t ring will work w/o trying. I
have a 50t Shimano SG ring that has minimal shift assist that is one
of crispest shifting rings.

Barend and DT shifters will shift almost any front and compact cranks.

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front
derailleur, I noticed that the large chainring was *bending* severely during
upshifting, up to ~3mm. This was rather shocking to see, especially since
the ramps and pins simply didn't want to grab the chain. The chain really
had to be forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

I was mashing the pedals during a hard acceleration and bent my FSA
Energy crankset. The chainrings flexed out and bent the spider to the
outside. FSA repaired it, but I could still see the chainrings flex
3-5mm every time I really pushed on the pedals. I ride a Campy Centaur
now and don't see this kind of flexing. After that crankset and a
couple bottom brackets gone bad I don't care much for their products.

-nate

"Drew Eckhardt" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <%6zYf.4608$fS6.3889@dukeread11>,

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front

I had a rubbing problem after swapping my 30-40-50 Racing-T for a
34-50 FSA compact. The other pieces of the equation are a Litespeed
Natchez frame, 13-23 9-speed cogset, and 9 speed Campagnolo chain.

Playing with my dial calipers I found that the ring-to-ring spacing
was less than Campagnolo specified for the current 10-speed setup which
is in turn .4mm closer than the 9-speed setup.

Adding a .4mm spacer on the big ring got me back a couple of gears without
ill effects; going out 1.0mm elimianted rub in the last 3 cogs rubbing but
made upshifts a little slower; I don't recall if I left that or went to
.8mm narrower.

I got my .4mm and .6mm shims from Wheels Manufacturing.
--

I'm using a regular Chorus 10spd front der with my FSA Compact SLK set up.
The shifting is better than my all Campy double or triple set ups on my
other bikes (the pins really pick up the chain) and I don't have much ring
rub except in the most extreme combinations and I don't detect any flex.
Sometimes I have to look down to see that I've shifted up to the big ring
its so smooth. On the other hand, it took alot of trial and error to get
the cranks tight enought to hold and not too tight to bind the BB bearings
with this mega exo BB. I have to say I don't like this BB design.

Ken

Squid-in-Training said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front
derailleur, I noticed that the large chainring was *bending* severely during
upshifting, up to ~3mm. This was rather shocking to see, especially since
the ramps and pins simply didn't want to grab the chain. The chain really
had to be forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

That amount of flex seems excessive. Someone else on the thread claimed
it as well, so, maybe, but it is hard to believe. That could not be good
for durability.

But the other suggestion worth considering is the spacing between rings.
I would much rather increase that spacing with washers than swap out the
bottom bracket for something wider. That wider BB will also make the
chainline worse on the lowest gears, which often have the highest stresses.

--

David L. Johnson

__o | Do not worry about your difficulties in mathematics, I can
_`\(,_ | assure you that mine are all greater. -- A. Einstein
(_)/ (_) |

David L. Johnson said:

Squid-in-Training said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from
a 108 to a 113. It upshifted rather poorly afterwards, but the
rider wanted at least the 3rd from last cog (9sp) while in the 34t.
During adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm.
This was rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain. The chain really had to be
forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

That amount of flex seems excessive. Someone else on the thread
claimed it as well, so, maybe, but it is hard to believe. That could
not be good for durability.

But the other suggestion worth considering is the spacing between
rings.

Great idea. I'll suggest that one.

Quoted message said:

I would much rather increase that spacing with washers than swap out
the bottom bracket for something wider. That wider BB will also make
the chainline worse on the lowest gears, which often have the highest
stresses.

The chainline wasn't too terrible on the lowest gears, but it would get
better with spacing out the chainrings. The rider really shouldn't be in
the 34t most of the time here in FL.

--
Phil, Squid-in-Training

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front
derailleur, I noticed that the large chainring was *bending* severely during
upshifting, up to ~3mm. This was rather shocking to see, especially since
the ramps and pins simply didn't want to grab the chain. The chain really
had to be forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

--
Phil, Squid-in-Training

You're not saying there's that much flex going on when you shift the
bike while it's the stand, right?

Nate Knutson said:

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from
a 108 to a 113. It upshifted rather poorly afterwards, but the
rider wanted at least the 3rd from last cog (9sp) while in the 34t.
During adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm.
This was rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain. The chain really had to be
forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

--
Phil, Squid-in-Training

You're not saying there's that much flex going on when you shift the
bike while it's the stand, right?

I am.
--
Phil, Squid-in-Training

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from a
108 to a 113. It upshifted rather poorly afterwards, but the rider
wanted at least the 3rd from last cog (9sp) while in the 34t. During
adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm. This
was rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain. The chain really had to be
forced up by the inner plate onto the chainring to get it to work.
Has anyone else seen this in practice?

I think I answered my own question. With the drive-side crank out 2.5 mm,
the derailleur, although a parallelogram, travels in an arc. With the
derailleur further out, it also has to rise. Because it has to rise, the
cage is no longer in the right position, and thus shifting is crappy.

The problem still lies with the shift gates and ramps though. They simply
do not pick up the chain at all.
--
Phil, Squid-in-Training

Phil said:

Nate Knutson said:

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from
a 108 to a 113. It upshifted rather poorly afterwards, but the
rider wanted at least the 3rd from last cog (9sp) while in the 34t.
During adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm.
This was rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain. The chain really had to be
forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

--
Phil, Squid-in-Training

You're not saying there's that much flex going on when you shift the
bike while it's the stand, right?

I am.
--
Phil, Squid-in-Training

Wow, that's pretty amazingly bad.

Paul Kopit said:

Doug Taylor said:

The compact derailleurs are shaped to fit the diameter of the smaller
rings and designed to pull the bigger gap (they say).

The clear and undisputed winner is the Dura Ace 10/ FSA combination:
instant, easy, crisp, precise.

Coming in second is Dura Ace 10/Dura Ace 8. Not quite as good as the
above, but the 10 year old 8 speed Dura Ace is still Dura Ace.

Tied for Third is Ultegra 10 / FSA and Ultegra 10/Dura Ace 8. My Dura
Ace shifter blew up, and the Ultegra 10 I swapped it with just doesn't
pull the either derailleur with the authority of the two above. I'm
still messing around with all kinds of variables: cable tension,
limits, height above the rings.

I've had great luck with DA 8 font derailleur and compact cranks. I
most frequently use Campy 10sp front derailleurs and not the CT type.
The IRD and CT have not been impressive. I can get a Campy front with
Ergo shifters to shift rings like Sugino that don't have shift
assists. You cannot tell how good a 50t ring will work w/o trying. I
have a 50t Shimano SG ring that has minimal shift assist that is one
of crispest shifting rings.

Barend and DT shifters will shift almost any front and compact cranks.

In our experience the only CT FD to work well is the Campag one IF it
is mated to a Campagnolo compact crank and chain. With FSA, it just
works poorly, a standard FD works well. Also finding FSA rings and BBs
are not of a very high quality, judging by the quick wear of both. The
shimano compact and Centaur aluminum compact/Centaur BB are our
compacts of choice these days, inspite of the more $. better rings and
BBs, better for the long run.

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon Compact
Pro cranks and FSA compact front derailleur. We troubleshooted the
big-ring-rub problem by changing out the BB from a 108 to a 113. It
upshifted rather poorly afterwards, but the rider wanted at least the 3rd
from last cog (9sp) while in the 34t. During adjustment of the front
derailleur, I noticed that the large chainring was *bending* severely during
upshifting, up to ~3mm. This was rather shocking to see, especially since
the ramps and pins simply didn't want to grab the chain.

sounds like a chain problem, not a crank problem. what type of chain
was it?

Quoted message said:

The chain really
had to be forced up by the inner plate onto the chainring to get it to work.

Has anyone else seen this in practice?

Qui si parla Campagnolo said:

In our experience the only CT FD to work well is the Campag one IF it
is mated to a Campagnolo compact crank and chain. With FSA, it just
works poorly, a standard FD works well. Also finding FSA rings and BBs
are not of a very high quality, judging by the quick wear of both. The
shimano compact and Centaur aluminum compact/Centaur BB are our
compacts of choice these days, inspite of the more $. better rings and
BBs, better for the long run.

For better or for worse, I have little experience with Campy, and none
with their compact components. I'll defer to you on that subject:
http://www.velonews.com/tech/report/articles/7844.0.html

Though I have complimented many IRD components that others don't like
- e.g. cassettes and chains - I did not like their CT FD. As
reported, however, the FSA CT works great for me when paired with the
Dura Ace shifter, and unlike the shifter, is inexpensive

I have used FSA Carbon Pro Elite and bb on one of my bikes for 2
seasons with noen of the wear issues you notice, but that's one rider
and not a customer list :-)

I have a new K -Force mega Exo on the other, and will now find out
about all the bearing wear issues etc. that people whine about. I did
have the frame bb threads faced before I installed it, so maybe not.

Paul Kopit said:

I use 52/36 all the time w/o problem and FSA rings. I've used
54/42 x 110 Sugino rings on Tandem for years, also w/o problems.
Many people have done this.

I don't recall broken rings at all.

The stronger tandem teams on the local list reported flex in large
but thin 110BCD rings, something like the 4,5mm XTR or thicker
worked well...

--
MfG/Best regards
helmut springer

jim beam said:

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from
a 108 to a 113. It upshifted rather poorly afterwards, but the
rider wanted at least the 3rd from last cog (9sp) while in the 34t.
During adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm. This was
rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain.

sounds like a chain problem, not a crank problem. what type of chain
was it?

Although my memory is weak, I'm pretty sure it was a Wipperman Connex 908,
and it was on a Shimano 105 group.

--
Phil, Squid-in-Training

Phil said:

jim beam said:

Phil said:

I had a customer with a Bianchi come in with his newish FSA Carbon
Compact Pro cranks and FSA compact front derailleur. We
troubleshooted the big-ring-rub problem by changing out the BB from
a 108 to a 113. It upshifted rather poorly afterwards, but the
rider wanted at least the 3rd from last cog (9sp) while in the 34t.
During adjustment of the front derailleur, I noticed that the large
chainring was *bending* severely during upshifting, up to ~3mm. This was
rather shocking to see, especially since the ramps and pins
simply didn't want to grab the chain.

sounds like a chain problem, not a crank problem. what type of chain
was it?

Although my memory is weak, I'm pretty sure it was a Wipperman Connex 908,
and it was on a Shimano 105 group.

try it with a shimano chain. the bulges in the side plates on the 9-s
groups are designed to be picked up by the ramps. flat plated chains
work, but not anywhere near as well.

jim beam said:

Phil said:

jim beam said:

Phil, Squid-in-Training wrote:

> I had a customer with a Bianchi come in with his newish FSA Carbon
> Compact Pro cranks and FSA compact front derailleur. We
> troubleshooted the big-ring-rub problem by changing out the BB from
> a 108 to a 113. It upshifted rather poorly afterwards, but the
> rider wanted at least the 3rd from last cog (9sp) while in the 34t.
> During adjustment of the front derailleur, I noticed that the large
> chainring was *bending* severely during upshifting, up to ~3mm.
> This was rather shocking to see, especially since the ramps and
> pins simply didn't want to grab the chain.

sounds like a chain problem, not a crank problem. what type of
chain was it?

Although my memory is weak, I'm pretty sure it was a Wipperman
Connex 908, and it was on a Shimano 105 group.

try it with a shimano chain. the bulges in the side plates on the 9-s
groups are designed to be picked up by the ramps. flat plated chains
work, but not anywhere near as well.

Good point, thanks.
--
Phil, Squid-in-Training