48T to replace 42T Chainwheel?

Quoted message said:

Is it possible to replace the 42T on a 22/32/42T
chainwheel with a 48T? (Shimano Nexave model). The outer
chainwheel can be removed - I'm just worried that the 32<-

Quoted message said:

48 jump may be a little too much for the front mech to

handle. If not what is the biggest I could get away with
on the front top?

You'll have a couple of problems with using a 48t. First,
the current derailleur is made for the radius of a 42t
chainring; to use it on a 48t, it's going to have to be
moved way up, with the tail end of the derailleur dragging
the chainring while the front (where the shifting normally
occurs) too high above the chainring to move the chain
efficiently.

The other problem you'll encounter is that *any* derailleur
will have trouble dealing with a triple when there's a 16t
gap between the largest two chainrings. This is because it
(the derailleur) will be sitting so high above the middle
chainring (since its height is dictated by the large
chainring) that it won't want to move the chain off of the
32 during a downshift.

A 2-tooth increase to 44t will probably work fine; beyond
that, you'll notice significant degradation in performance.

--Mike-- Chain Reaction Bicycles
chainreactionbicycles.comchainreactionbicycles.comOpen ↗

"Ben Rowlands" <ben.REMOVE_THIS@AND_THIS.zone-2.com> wrote
in message -"]news:[email hidden]-
.ic.ac.uk...

Quoted message said:

Hi,

Is it possible to replace the 42T on a 22/32/42T
chainwheel with a 48T? (Shimano Nexave model). The outer
chainwheel can be removed - I'm just worried that the 32<-

Quoted message said:

48 jump may be a little too much for the front mech to

handle. If not what is the biggest I could get away with
on the front top?

Thanks,

Ben
---

"Ben Rowlands" <ben.REMOVE_THIS@AND_THIS.zone-2.com> wrote in message
"]news:[email hidden]

Quoted message said:

Hi,

Is it possible to replace the 42T on a 22/32/42T
chainwheel with a 48T? (Shimano Nexave model). The outer
chainwheel can be removed - I'm just worried that the 32<-

Quoted message said:

48 jump may be a little too much for the front mech to

handle. If not what is the biggest I could get away with
on the front top?

What's your crank's model number? The Nexave FC-C900 crank
is a 36-46T double. 22-32-42T sounds like an Alivio. If you
also have an Alivio front derailleur Shimano recommend a
maximum tooth gap of 10 (although I'm getting away with 12).
The Deore cranksets come in either 22-32-44 or 26-36-48.
This is consistent with the maximum 12 tooth gap Shimano
recommend for the Deore front derailleur. I put a 44T on my
Alivio but I doubt you'd get away with a 48, the 16 tooth
gap would be too big.

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

Quoted message said:

Quoted message said:

Is it possible to replace the 42T on a 22/32/42T
chainwheel with a 48T? (Shimano Nexave model). The outer
chainwheel can be removed - I'm just worried that the
32<->48 jump may be a little too much for the front mech
to handle. If not what is the biggest I could get away
with on the front top?

You'll have a couple of problems with using a 48t. First,
the current derailleur is made for the radius of a 42t
chainring; to use it on a 48t, it's going to have to be
moved way up, with the tail end of the derailleur dragging
the chainring while the front (where the shifting normally
occurs) too high above the chainring to move the chain
efficiently.

The other problem you'll encounter is that *any*
derailleur will have trouble dealing with a triple when
there's a 16t gap between the largest two chainrings. This
is because it (the derailleur) will be sitting so high
above the middle chainring (since its height is dictated
by the large chainring) that it won't want to move the
chain off of the 32 during a downshift.

A 2-tooth increase to 44t will probably work fine; beyond
that, you'll notice significant degradation in
performance.

FWIW, I have a 22-34-48 combo (on a road bike) that I shift
with a bottom pull LX front derailleur and STI shifters. The
gears are flat (no ramps). It shifts without problems. I
have over 25K miles on this arrangement.

Speaking only from my own experience, Tom

I changed my 22/32/42 to 22/32/46. The 32->46 shift is fine. I imagine that 32->48 would still work OK but probably just a bit more sluggish.

"Gonzo Bob" <[email hidden]> wrote in message
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Quoted message said:

I changed my 22/32/42 to 22/32/46. The 32->46 shift is
fine. I imagine that 32->48 would still work OK but
probably just a bit more sluggish.

What front derailleur do you have?

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