56T chainring

Shimano and every bike shop says it can't/shouldn't be done. I have a
39/56 on my Cervelo. Looked for a 42 or 44 but don't want to pay full retail for one. Mine shifts
very well up, but sometimes downshifting it doesn't engage completely for a 1/4 to 1/2
revolution.

TriRod IMC 2002 IMUSA CdA 2003

Jim Quinn said:

Does the Dura Ace 56T time trial chainring have to be matched with a similar small chainring or
can it be used with a standard 42 or 39 chainring?

How many watts would it take to push a 56 x 12 at 100RPM on the flats into a null wind for a 160-170
lbs rider? For a 700cc wheel what speed would that work out to?

Rod Richeson wrote in message <[email hidden]>...

Quoted message said:

Shimano and every bike shop says it can't/shouldn't be done. I have a
39/56 on my Cervelo. Looked for a 42 or 44 but don't want to pay full retail for one. Mine shifts
very well up, but sometimes downshifting it doesn't engage completely for a 1/4 to 1/2
revolution.

TriRod IMC 2002 IMUSA CdA 2003

Jim Quinn said:

Does the Dura Ace 56T time trial chainring have to be matched with a

similar

Quoted message said:

Quoted message said:

small chainring or can it be used with a standard 42 or 39 chainring?

BillX said:

How many watts would it take to push a 56 x 12 at 100RPM on the flats into a null wind for a
160-170 lbs rider? For a 700cc wheel what speed would that work out to?

Lots. That's probably why he's asking about the 39T small chainring option.

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

Quoted message said:

How many watts would it take to push a 56 x 12 at 100RPM on the flats into

a

Quoted message said:

null wind for a 160-170 lbs rider? For a 700cc wheel what speed would

that

Quoted message said:

work out to?

Why do you assume that the original poster will be pairing that 56 tooth chainring with a 12 tooth
cog? For that matter, why do you assume that they wish to pedal at 100 rpm?

Andy ("55 x 12 at 78 rpm = 300 W and 28 mph"😉 Coggan

Most road cyclists find a cadence of 90-110 rpm on the flats to be optimal although there are some
like yourself who find a lower cadence like 80 rpm to be more effective. I'd assumed that someone
wouldn't use a 56x12 on the flats unless they could push 90 rpm or better in that gear.

Andy Coggan wrote in message

Quoted message said:

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

Quoted message said:

How many watts would it take to push a 56 x 12 at 100RPM on the flats

into

Quoted message said:

a

Quoted message said:

null wind for a 160-170 lbs rider? For a 700cc wheel what speed would

that

Quoted message said:

work out to?

Why do you assume that the original poster will be pairing that 56 tooth chainring with a 12 tooth
cog? For that matter, why do you assume that they wish to pedal at 100 rpm?

Andy ("55 x 12 at 78 rpm = 300 W and 28 mph"😉 Coggan