Compact Chainrings: Best Set?

All rings shifting equal...
34/50
36/50
36/48
$64MM Question: "Which Chainring set?

I've run all the numbers (jbarrm.com). Every CT/cassette (Campy)
combination straddles my natural cadence ratio 15/42== 73 GI. Every CT
combination profile underspins the "little ring" and overspins the "big
ring".

Is the trade-off in the final analysis== No natural cadence GI?

-Rex Riley

On Mon, 13 Jun 2005 20:45:43 -0700, wrote:

All rings shifting equal...
34/50
36/50
36/48
$64MM Question: "Which Chainring set?

I've run all the numbers (jbarrm.com). Every CT/cassette (Campy)
combination straddles my natural cadence ratio 15/42== 73 GI. Every CT
combination profile underspins the "little ring" and overspins the "big
ring".

I'm not sure of what you mean by "underspins" here, but I'm guessing you
mean that the nearest gear to what you want seems to be too low in the
little ring, too high in the big.

Depends on your cassette. A really tight cassette is still available with
an 18-tooth ring, and a 50/18 is a 72.6" gear. The problem with the 50
(for you, at least) is that you need that 18, which is not real common,
but is on my 12-21 9-speed cassette.

The 48 might be better, since that gives you a 73.8" gear with the 48/17,
and durn near every cassette Campy makes has a 17. Either of these gear
ratios is close enough to your preferred 73" that you will not be able to
tell the difference.

Most people with 53/39 or 52/42 chainrings, at least most people on club
rides, spend a whole lot of time using the little ring. With a compact
crankset you spend more time using the big ring, and the little one is
there for the hills. Works for me, but to each his own. If you feel you
need that 53/11 for something, then the compact will disappoint you, but
on the other hand if you want that 34/26, a compact crank will give it to
you and the old-style will not, not without a cassette that misses a lot
of intermediate ratios.

--

David L. Johnson

__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |

" wrote:

All rings shifting equal...
34/50
36/50
36/48
$64MM Question: "Which Chainring set?

I've run all the numbers (jbarrm.com). Every CT/cassette (Campy)
combination straddles my natural cadence ratio 15/42== 73 GI. Every CT
combination profile underspins the "little ring" and overspins the "big
ring".

Is the trade-off in the final analysis== No natural cadence GI?

I'm thinking that if your cassette choices for the compact chainrings
you cite end up "underspinning the little ring" and "overspinning the
big ring" you should probably stick with traditional 53/39 rings: you
don't need compact rings.

Compact rings are chosen precisely because you want/need lower
gearing, and with that goal in mind, there are inevitable trade offs.

I'm running nine speed Shimano and live in an area where hills reign.
I needed/wanted lower gearing than 39:27, and so decided to go with an
FSA 50/34 compact. Running the same Shimano 12-27 cassette, I
achieved the lower gears I wanted, but of course lost the high gear
that all my riding partners have with 53:12 (nobody I ride with has
53:11). So there were plenty of instances of furiously spinning out
in flats and downhills that were frustrating.

The solution is to mess around with custom cassettes, because there is
no stock cassette that has both an 11 and anything over 25.
Currently, I'm running Harris Cyclery's "High and Wide" 11-28
http://sheldonbrown.com/harris/k7.html#9

The 50:11 is actually higher than 53:12. Yeah, the 34:28 is a bit
much, but I use that sucker all the time and even the dreaded 50:28.
34:11 and 34:12 are too slack.

So, trade offs. Someday I'll upgrade to 10 speed and one more gear,
but I ain't getting any younger, so I always have compact up front. I
don't think a triple is really necessary, and am happy with my
compromises.
--dt

When I wanted to change to a more "sane" gearing on my 53/39 road bike what
I did was get a Ultegra 14-25 cassette and a 11-32 mountain cassette. The
23,25 cogs are loose on the 14-25 so I replaced them with the 24,28 cogs
from the 11-32 cassette. I'm pretty sure if you get a Shimano Mountain LX
11-32 the cogs will a be loose. What I got is a SRAM, but I can't recommend
that to you because the the teeth seem to be beveled inward towards the
spokes on the SRAM and outwards on the Shimano. This makes the shift from
the Shimano 21 to the SRAM 24 kind of tricky, but I've fooled around enough
to get everything to work ok but if I had it to do over I would have got the
Shimano.

You can always pop on the 11-32 cassette if you're going to be mountain
climbing, but I prefer the 1 tooth jumps from 14-19 for everything else.
B.T.W the 53/19 is exactly the 73 GI that you're looking for as well.

Another thing to try is getting a 30 tooth cog and swaping the 23, 25 of the
14-15 with a 25,30 instead of the 24,28 that I'm recommending and if you
swap your 39T chainring for a 38T than that'll really give you some climbing
gears with out buying a new crank, bottom bracket, IRD front derailleur, and
Shimano brazeon-to-clampon adapter.

K.

" wrote in message
oups.com...
All rings shifting equal...
34/50
36/50
36/48
$64MM Question: "Which Chainring set?

I've run all the numbers (jbarrm.com). Every CT/cassette (Campy)
combination straddles my natural cadence ratio 15/42== 73 GI. Every CT
combination profile underspins the "little ring" and overspins the "big
ring".

Is the trade-off in the final analysis== No natural cadence GI?

-Rex Riley